Patent Application
20230389573
The current invention relates to a marine peptide product derived from by-products of fish processing. In particular, the invention relates to an animal food product comprising marine peptides, which has health benefits including antihypertension activities.
Many pet owners are concerned with both the nutritional and health needs of their pets. To meet nutritional requirements, pet food formulas can be selectively altered to vary the protein content, vitamin and mineral content and the caloric content. The balance of these ingredients becomes critical when making a dry pet food because a portion of the formula must be flours, which are required for structure. When making a dog/cat biscuit, the requirement that a portion of the formula be for structural ingredients becomes even more critical. The alternation of nutritional ingredients can affect the colour, biscuit strength, rise of the biscuit and the hardness of the biscuit. It is often desirable that the texture of dog biscuits intended for older or “senior” dogs provides a softer chew.
Common dog biscuits typically contain between 60% and 70% wheat flour, 10% soybean meal, 6% percent meat and bone meal and between 2% and 3% fat in the form of tallow. 11-12% miscellaneous ingredients are added. These biscuits typically contain about 1.5% fiber and about 20-22% protein. The majority of the protein is derived from the wheat flours used to make the dog/cat biscuit. The substitution of a portion of wheat flour with another ingredient can cause difficulties in the manufacturing of dog biscuits so that texture and appearance of the final product is affected.
Angiotensin-converting enzyme-I (ACE-1) inhibitors represent one of the most commonly used categories of drugs in canine and feline medicine. ACE-1 inhibitors currently approved for use in veterinary medicine are the pro-drugs benazepril, enalapril, imidapril and ramipril and are generally well tolerated. Benazepril, enalapril, imidapril and ramipril are approved for dogs with chronic heart failure (CHF), especially in those with chronic valvular disease. In such clinical settings, ACE-1 inhibitors improve hemodynamics and clinical signs and increase survival time. There have been reports of some benefit in cats with hypertrophic cardiomyopathy in two non-controlled investigations. Mitral valve regurgitation (MR) secondary to degeneration of the mitral valve apparatus is the most common cardiac disease in dogs, and the incidence of MR is approximately 30% in dogs aged 13 years and older. MR is a progressive disease that in severe instances can result in death, despite medical treatment. The progressive character of MR is intimately related to the renin-angiotensin aldosterone system (RAAS) that regulates blood pressure (BP), tissue perfusion, and fluid balance. Like the other cardiac disorders, the dysregulation of RAAS is a key to the process of chronic heart failure (CHF) in dogs with MR. Pharmacological inhibition of the RAAS with angiotensin-converting enzyme (ACE-1) inhibitors plays an important role in the management of MR, as indicated by many reports describing how the long-term efficacy of inhibiting ACE resulted in an improvement of congestive heart failure in dogs with MR.
Renal diseases, especially chronic renal failure (CRF), are common in canine and feline medicine. The renin-angiotensin-aldosterone system (RAAS) plays a pivotal role in these conditions in the development of renal lesions and the progression of kidney dysfunction. Angiotensin-converting enzyme inhibitors (ACEI) are currently considered as the most efficient agents in therapeutic strategies. The benefit of an ACEI treatment can be explained by at least three mechanisms: ACEI limit systemic and glomerular capillary hypertension, have an antiproteinuric effect, and retard the development of glomerulosclerosis and tubulointerstitial lesions. These effects have been studied in dogs and cats, and there is some evidence to support the recommendation of ACEI therapy in dogs and cats with CRF. Nevertheless, the prescription of ACE-1 in such patients should take into account the potential influence of renal impairment on ACE-1 disposition, and adverse effects on the renal function itself (especially hypotension and acute reductions in glomerular filtration rate). The risk of drug interaction with diuretics, nonsteroidal anti-inflammatory drugs, and anaesthetics, should not be overestimated. Furthermore, hypotension may occur in patients on a low sodium diet.
Diet may be also considered as a factor for reducing the risk to the heart of dogs and cats and indeed humans. Although antihypertensive drugs are available on the market, nutritionists claim that peptides which lower BP found in food are safer than “traditional” drugs and can be used as preventive agents in human and indeed animal heart health.
Functional foods provide health benefits if they are consumed on a regular basis as part of a varied diet. Functional foods for pets can modify gastrointestinal physiology, promote changes in biochemical parameters, improve brain functions and may reduce or minimize the risk of developing specific pathologies. This evidence derives largely from clinical studies while only limited evidence is available from studies in dogs and cats.
Pelagic fish species, including mackerel (Scomber scombrus), Blue whiting (Micromesistius poutassou), Horse mackerel (Scad, Trachurus trachurus) and Atlantic herring (Clupea harengus) are in the top 10 species contributing to global total fish catch and are valued for their n−3 long chain polyunsaturated fatty acids (PUFAs), vitamin D and protein content (Lindqvist et al., 2007).
During fish processing, by-products can account for up to 75% of the total catch by weight. Blood is a major by-product of fish processing and can originate from storage on boats, boat unloading, butchering, and processing, scaling, filleting, skinning, and evisceration. This blood-water poses an environmental and economic cost, and it can lead to contamination of the marine environment by raising the biological oxygen demand (BOD) which may cause algae blooms (Islam et al., 2004).
Several problems exist concerning utilisation of fish blood. Firstly, collection and drying of fish blood is difficult as the properties of fish blood vary from warm blooded animals. It is difficult to separate fish blood from the process water after bleeding and process water can pollute the fish blood with materials including faeces, salt and fish scales. Where fish blood is collected along with process waters the composition of these “blood-waters” can vary depending on the species caught, the volume of fish processed, the processing techniques employed (i.e., hand filleting V's mechanical) and other parameters including the temperature on board and the volume of water used during processing.
Skin and bone, which are known to be rich in collagen, make up approximately 30% of the weight of by-products from blue whiting surimi manufacture. Blue Whiting (Micromesistius poutassou) is a pelagic fish found extensively in the northern hemisphere.
CN105063150 discloses a method of preparing peptides from tuna derived blood, by hydrolysing the fish blood with alkaline protease and passing the hydrolysate through an ultrafiltration unit having a cut-off of 10 KDa.
Huang Chun-Yung et al., (Marine Drugs, vol. 16, no. 10, 2018) discloses a method for producing peptides comprising extraction of gelatin from milkfish scales, hydrolysis to produce a hydrolysate and subsequent separation by passing the hydrolysate through an ultrafiltration membrane with a cut-off of 3 KDa.
Khiari Zied et al., (Journal of The Science of Food and Agriculture, vo. 94, no. 8, December 2013) discloses a method for producing peptides comprising extraction of fish gelatin from mackerel skin, preparation of a hydrolysate and isolation by passing via an ultrafiltration filter with a cut-off of 3 kDa.
US2018/352832 discloses preparation of a protein hydrolysate from Calanus finmarchicus comprising peptides of 1-6 KDa, peptides of 0.2-1 KDa and amino acids <200 Da. The product is rich in taurine and arginine. The authors speculate high palatability when used as feed for cats and dogs.
Chen Junde et al., (Marine Drugs, vol. 16, no. 7, 2018) discloses the extraction of gelatin from lizardfish and obtaining peptides from the extracted gelation. The hydrolysate was produced by using a pepsin enzyme. Fractionation of the gelatin hydrolysate was carried out by chromatography.
The current invention serves to alleviate the problems associated with the prior art. The current inventors provide a method to recover, stabilise and characterise by-products of fish processing, such as blood-water collected during processing of pelagic fish and skin and bone from surimi manufacture and to provide an improved functional food in pet nutrition comprising extracts from fish processing. This functional food has a use in pet nutrition for disease prevention and is also appetizing and appealing in terms of appearance.
The current invention relates to animal food products (herein referred to as “the food product of the invention”). Most specifically, the food product is an animal biscuit, particularly for dogs and cats. The food product of the invention comprises peptides derived from marine by-products generated during the processing of fish. The by-products include one or more of fish skins, bone, gut waste and bloodwaters.
The peptides are obtained by recovering the by-product using filtration methods with 3 kDa and/or 10 kDa membranes. Each fraction, or “marine peptide product”, has a particular peptide and amino acid composition and the fraction is used to make the food product of the invention.
Most advantageously, the animal food product of the invention has health benefits, as well as a desirable appearance and texture. The use of the by-product extract with farinaceous ingredients provides a food product in which the overall protein content is increased in essential amino acids when compared to standard animal biscuits and has ACE-1 inhibitory activity. This invention proposes the use of peptide ACE-1 inhibitors for prevention of disease through diet, rather than cure using pharmaceutical drugs. Heart health animal biscuits do not currently exist on the market. Most advantageously, the action of the ACE-1 inhibitory peptides remains active when incorporated into the biscuit.
The current inventors have shown ACE-1 inhibitory activity of peptide product from blue whiting and mackerel blood water in
The peptides of the current invention have not been identified previously from fish species. Furthermore, the inventors are the first to show their use for ACE-1 inhibition and the specific use for the prevention of hypertension in animals, especially companion animals.
In one aspect, there is provided a marine peptide product.
In an embodiment, the marine peptide product is derived or obtained from the by-products of fish processing. Preferably, the by-products include one or more of fish skins, bone, gut waste and bloodwaters.
Preferably, the fish by product used in the current invention is blue whiting or mackerel by product. This may be fish skin, bone, gut waste and/or bloodwaters.
In an embodiment, the fish by-product is bloodwater derived from pelagic or whitefish processing. Preferably, the by-product is pelagic fish bloodwater. Still preferred, the by product is bloodwater from blue whiting or mackerel.
In an embodiment, the fish by product is fish skins, bone, gut waste and bloodwaters. The fish from which it derives can be any fish, such as any fish source from which gelatine and/or gelatine hydrolysed peptides can be obtained. Examples include but are not limited to mackerel, horse mackerel, blue whiting, whitefish and shellfish. In this embodiment, gelatine/collagen is extracted from the fish by product. Preferably, the fish is pelagic fish, such as blue whiting.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 1 to SEQUENCE ID NO. 188, or a variant thereof.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 1 to SEQUENCE ID NO. 64, or a variant thereof.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 65 to SEQUENCE ID NO. 169, or a variant thereof.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 170 to SEQUENCE ID NO. 188, or a variant thereof.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 189 to SEQUENCE ID NO. 271, or 363 or a variant thereof.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 272 to SEQUENCE ID NO. 362, or a variant thereof.
Preferably, the marine peptide product may further comprise at least one fatty acid. The fatty acids may be one or more of the fatty acids listed in Table 5. The fatty acid may be all of the fatty acids listed in Table 5.
In an embodiment, the marine protein product is a hydrolysed marine protein product. i.e. a hydrolysate.
Typically, the pelagic fish is blue whiting or mackerel.
The marine peptide protein may be in the form of a powder, such as a dried protein powder.
In one aspect, the invention provides an animal food product, or comestible product, comprising a marine peptide product. The marine protein product is the marine protein product of the invention as described herein.
Preferably, the animal is a companion animal, such as a dog or a cat.
Preferably, the food product is a biscuit. The food product may be an extruded snack, a dried powder, a kibble, a bounce ball, or energy ball, or any similar suitable animal food product. Typically, the biscuit is suitable for consumption by a dog and/or a cat.
Typically, the biscuit further comprises (or consists of) one or more of wheat flours, water, oil, typically vegetable oil.
In an aspect, there is provided a peptide having a sequence selected from SEQUENCE ID NO 1 to SEQUENCE ID NO. 363, or a variant of SEQUENCE ID NO 1 to SEQUENCE ID NO. 363 (“peptide of the invention”).
A further aspect of the invention provides a method for producing a marine peptide product from a marine by-product, the method comprising the following steps:
The marine peptide product is provided in the obtained fractions.
In an embodiment, the method further comprises a step of drying the retentate, 10 kDa fraction and/or 3 kDa fraction. Any suitable drying method may be used. Preferably, the drying method is selected from the group comprising spray drying, freeze drying and pulse combustion.
Alternatively, the retentate or fraction may be provided in the form of a paste or a liquid product. Any suitable known method of providing a paste or liquid product may be used.
In an embodiment, the by-product is bloodwaters from pelagic fish.
In an embodiment, prior to filtering, the method comprises an optional step of extracting gelatine from the by-product to provide a by-product in the form of a gelatine extract. In this embodiment, the method further comprises a step of hydrolysing the gelatine extract with one or more hydrolyses enzymes. In this embodiment, it is the hydrolysed gelatine extract that is the by-product that is then filtered using one or more filters as per the above-described method.
Prior to extracting the gelatine, the by-product may be pre-treated. This pre-treatment step may comprise one or more acid treatment steps. The acid may be selected from the group comprising NaOH, HCL, sulphuric acid, citric acid and acetic acid.
This may be pre-treatment with an amount of NaOH, following by an amount of sulphuric acid, followed by an amount of acetic acid. The product may be washed with water in between each step of addition. The product may be washed after the final step.
This may be pre-treatment with an amount of NaOH, following by an amount of HCL following by an amount of acetic acid. The product may be washed with water in between each step of addition. The product may be washed after the final step.
This may be a pre-treatment with an amount of an enzyme following by an amount of HCL. The enzyme may be alcalase. The product may be washed with water in between each step of addition. The product may be washed after the final step.
This may be pre-treatment with an amount of NaOH, following by an amount of citric acid. The product may be washed with water in between each step of addition. The product may be washed after the final step.
After the pre-treatment step the gelatine is extracted, for example overnight in a shaker, preferably, using water (3:1 v/w to material) at 45° C. in a MaxQ 8000 laboratory shaker (Thermo Fisher Scientific, MA USA) at 200 rpm speed.
More specifically, four standard operating procedures (SOP) for pre-treatment were assessed by the inventors, three of which (SOP1, SOP2 and SOP4) included chemical treatment, while SOP3 consisted of a combination of both chemical and enzymatic pre-treatment.
SOP1—The skin and bone material was washed once using tap water (6:1 v/w to material) and pre-treated three times in consecutive order as follows with 0.2% (w/v) NaOH (6:1 v/w skin and bone) for 40 min followed by washing with water, then with 0.2% (v/v) sulphuric acid (6:1 v/w to skin and bone) for 40 min followed by washing with water, and finally using 0.05M acetic acid (6:1 v/w to skin and bone) for 40 min followed by washing with water.
SOP2—). The skin and bone material was washed once using tap water (6:1 v/w to material) and pre-treated three times with 0.1M NaOH (6:1 v/w to material) for 30 min. After washing with water, it was treated with 0.25M HCl (6:1 v/w to material) for 2 h, and then with 0.05M acetic acid (6:1 v/w to material) for 1 h, followed by washing with water.
SOP3—The skin and bone material was washed once using tap water (6:1 v/w to material) and hydrolysed with alcalase enzyme (Sigma Aldrich, Ireland; 2.5 U/ml) in 0.1M K-phosphate buffer (pH=8; 3:1 v/w buffer to material+0.1% (w/w to material) enzyme) for 1.5 h at 40° C. After heating the mixture to boiling for 5 min to inactivate the enzyme and washing with water, the material was then treated with 0.25M HCl (6:1 v/w to material) for 2 h and washed with water.
SOP4—The skin and bone material was washed once using tap water (6:1 v/w to material) and pre-treated three times with 0.1M NaOH (6:1 v/w to material) for 30 min. After washing with water, it was treated with 1M citric acid (6:1 v/w to material) for 2 h and finally washed with water.
After pre-treatment using the individual SOPs the by-product skin and bone material was washed with water until neutral (pH 6-7) and gelatine was extracted overnight using water (3:1 v/w to material) at 45° C. in a MaxQ 8000 laboratory shaker (Thermo Fisher Scientific, MA USA) at 200 rpm speed. Following gelatine extraction, solids were removed by filtration through Whatman No 4 filter paper using a BQchi funnel. The clear extracts were then freeze dried (FD80GP, Cuddon Freeze Dry, New Zealand) using the following program: initial temperature −20° C.; 5 steps; run time 90 h; end temperature 0° C. Dried material was placed in sterile sealed 250 ml containers and stored at −80° C. until analyses.
The composition of the extracted gelatine may be: 348 (γ-chain), 215 (β-chain), 117 (α2-chain), or a gelatine as disclosed herein.
The by-product from which gelatine is extracted is one or more of fish skins, bone and gut waste. The fish is any fish. Examples include but are not limited to pelagic fish and white fish. Typically, the by-product is skin and/or bone derived from processing of blue whiting into surimi products.
The enzyme may be papain, alcalase, protamex flavourzyme, or a suitable proteolytic enzyme or similar enzymes.
A further aspect provides a marine peptide product obtained by the method of the invention. The marine peptide product may be the 3 kDa fraction or a 10 kDa fraction.
A still further aspect provides a food product, or comestible product, comprising the marine peptide product obtained by the method of the invention.
An aspect of the invention provides a marine peptide product, the peptide, or food product of the invention, for use as a medicament.
An aspect of the invention provides a marine peptide product, the peptide, or food product of the invention, for use in a method of treatment or prevention of disease in an animal.
An aspect of the invention provides a marine peptide product, the peptide, or food product of the invention, for use in a method of prevention of disease or condition in an animal.
In an embodiment, the disease selected form the group comprising heart disease and renal disease or an inflammatory disease or condition.
The condition may be high blood pressure or hypertension.
In an embodiment, the marine peptide product or food product of the invention, may be for use in improving or maintaining eye health, or prevention or treatment of eye disease.
The heart disease may be selected from the group comprising, but not limited to, chronic heart failure (CHF), chronic valvular disease, hypertrophic cardiomyopathy, mitral valve regurgitation (MR), e.g., secondary to degeneration of the mitral valve apparatus.
In an embodiment, the marine peptide product or food product of the invention, may be for use to prevent high blood pressure or hypertension.
In an embodiment, the disease or condition is one associate with a metabolic syndrome, for examples, heart health or congestive heart failure.
The renal disease may be selected from the group comprising but not limited to chronic renal failure (CRF).
A further aspect of the invention provides a method of treatment or prevention of a disease or condition in an animal. The disease or conditions are those described herein for the use of the invention.
A further aspect of the invention provides a method of extracting gelatine as disclosed herein.
All publications, patents, patent applications and other references mentioned herein are hereby incorporated by reference in their entireties for all purposes as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference and the content thereof recited in full.
Where used herein and unless specifically indicated otherwise, the following terms are intended to have the following meanings in addition to any broader (or narrower) meanings the terms might enjoy in the art:
Unless otherwise required by context, the use herein of the singular is to be read to include the plural and vice versa. The term “a” or “an” used in relation to an entity is to be read to refer to one or more of that entity. As such, the terms “a” (or “an”), “one or more,” and “at least one” are used interchangeably herein.
As used herein, the term “comprise,” or variations thereof such as “comprises” or “comprising,” are to be read to indicate the inclusion of any recited integer (e.g. a feature, element, characteristic, property, method/process step or limitation) or group of integers (e.g. features, element, characteristics, properties, method/process steps or limitations) but not the exclusion of any other integer or group of integers. Thus, as used herein the term “comprising” is inclusive or open-ended and does not exclude additional, unrecited integers or method/process steps.
As used herein, the term “disease” is used to define any abnormal condition that impairs physiological function and is associated with specific symptoms. The term is used broadly to encompass any disorder, illness, abnormality, pathology, sickness, condition or syndrome in which physiological function is impaired irrespective of the nature of the aetiology (or indeed whether the aetiological basis for the disease is established). It therefore encompasses conditions arising from infection, trauma, injury, surgery, radiological ablation, poisoning or nutritional deficiencies.
As used herein, the term “treatment” or “treating” refers to an intervention (e.g. the administration of an agent to a subject) which cures, ameliorates or lessens the symptoms of a disease or removes (or lessens the impact of) its cause(s) (for example, the reduction in accumulation of pathological levels of lysosomal enzymes). In this case, the term is used synonymously with the term “therapy”.
Additionally, the terms “treatment” or “treating” refers to an intervention (e.g. the administration of an agent to a subject) which prevents or delays the onset or progression of a disease or reduces (or eradicates) its incidence within a treated population. In this case, the term treatment is used synonymously with the term “prophylaxis”.
The term “peptide” used herein refers to a polymer composed of 2 to 50 amino acid monomers typically via peptide bond linkage. Peptides (including fragments and variants thereof) of and for use in the invention may be generated wholly or partly by chemical synthesis or by expression from nucleic acid or may be obtained from a marine by-product. For example, the peptides of and for use in the present invention can be readily prepared according to well-established, standard liquid or, preferably, solid-phase peptide synthesis methods known in the art (see, for example, J. M. Stewart and J. D. Young, Solid Phase Peptide Synthesis, 2nd edition, Pierce Chemical Company, Rockford, Illinois (1984), in M. Bodanzsky and A. Bodanzsky, The Practice of Peptide Synthesis, Springer Verlag, New York (1984). When necessary, any of the peptides employed in the invention can be chemically modified to increase their stability. A chemically modified peptide or a peptide analog includes any functional chemical equivalent of the peptide characterized by its increased stability and/or efficacy in vivo or in vitro in respect of the practice of the invention.
The term peptide analog also refers to any amino acid derivative of a peptide as described herein. A peptide analog can be produced by procedures that include, but are not limited to, modifications to side chains, incorporation of unnatural amino acids and/or their derivatives during peptide synthesis and the use of cross-linkers and other methods that impose conformational constraint on the peptides or their analogs. Examples of side chain modifications include modification of amino groups, such as by reductive alkylation by reaction with an aldehyde followed by reduction with NaBH4; amidation with methylacetimidate; acetylation with acetic anhydride; carbamylation of amino groups with cyanate; trinitrobenzylation of amino groups with 2, 4, 6, trinitrobenzene sulfonic acid (TNBS); alkylation of amino groups with succinic anhydride and tetrahydrophthalic anhydride; and pyridoxylation of lysine with pyridoxa-5′-phosphate followed by reduction with NABH4. The guanidino group of arginine residues may be modified by the formation of heterocyclic condensation products with reagents such as 2,3-butanedione, phenylglyoxal and glyoxal. The carboxyl group may be modified by carbodiimide activation via o-acylisourea formation followed by subsequent derivatization, for example, to a corresponding amide. Sulfhydryl groups may be modified by methods, such as carboxymethylation with iodoacetic acid or iodoacetamide; performic acid oxidation to cysteic acid; formation of mixed disulphides with other thiol compounds; reaction with maleimide; maleic anhydride or other substituted maleimide; formation of mercurial derivatives using 4-chloromercuribenzoate, 4-chloromercuriphenylsulfonic acid, phenylmercury chloride, 2-chloromercuric-4-nitrophenol and other mercurials; carbamylation with cyanate at alkaline pH. Tryptophan residues may be modified by, for example, oxidation with N-bromosuccinimide or alkylation of the indole ring with 2-hydroxy-5-nitrobenzyl bromide or sulphonyl halides. Tryosine residues may be altered by nitration with tetranitromethane to form a 3-nitrotyrosine derivative. Modification of the imidazole ring of a histidine residue may be accomplished by alkylation with iodoacetic acid derivatives or N-carbethoxylation with diethylpyrocarbonate. Examples of incorporating unnatural amino acids and derivatives during peptide synthesis include, but are not limited to, use of norleucine, 4-amino butyric acid, 4-amino-3-hydroxy-5-phenylpentanoic acid, 6-aminohexanoic acid, t-butylglycine, norvaline, phenylglycine, ornithine, sarcosine, 4-amino-3-hydroxy-6-methylheptanoic acid, 2-thienyl alanine and/or D-isomers of amino acids. Peptide structure modification includes the generation of retro-inverso peptides comprising the reversed sequence encoded by D-amino acids.
The term “modified peptide” is used interchangeably with the term derivative of the peptide. The modified peptide includes a peptide which has been substituted with one or more groups as defined herein. The modification may be any modified that provides the peptides and or the composition of the invention with an increased ability to penetrate a cell. The modification may be any modification that increases the half-life of the composition or peptides of the invention. In one embodiment, the group is a protecting group. The protecting group may be an N-terminal protecting group, a C-terminal protecting group or a side-chain protecting group. The peptide may have one or more of these protecting groups. The person skilled in the art is aware of suitable techniques to react amino acids with these protecting groups. These groups can be added by preparation methods known in the art, for example the methods as outlined in paragraphs [0104] to [0107] of US2014120141. The groups may remain on the peptide or may be removed. The protecting group may be added during synthesis. In an embodiment of the invention the peptides may be substituted with a group selected from one or more straight chain or branched chain, long or short chain, saturated, or unsaturated, substituted with a hydroxyl, amino, amino acyl, sulfate or sulphide group or unsubstituted having from 1 to 29 carbon atoms. N-acyl derivatives include acyl groups derived from acetic acid, capric acid, lauric acid, myristic acid, octanoic acid, palmitic acid, stearic acid, behenic acid, linoleic acid, linolenic acid, lipoic acid, oleic acid, isosteric acid, elaidoic acid, 2-ethylhexaneic acid, coconut oil fatty acid, tallow fatty acid, hardened tallow fatty acid, palm kernel fatty acid, lanolin fatty acid or similar acids. These may be substituted or unsubstituted. When substituted they are preferably substituted with hydroxyl, or sulphur containing groups such as but not limited to SO3H, SH, or S—S. In an embodiment of the current invention, the peptide is R1—X— R2. R1 and/or R2 groups respectively bound to the amino-terminal (N-terminal) and carboxyl-terminal (C-terminal) of the peptide sequence. In one embodiment, the peptide is R1—X. Alternatively, the peptide is X— R2. Preferably, R1 is H, C1-4 alkyl, acetyl, benzoyl or trifluoroacetyl; X is the peptide of the invention; R2 is OH or NH2. In an embodiment, R1 is selected from the group formed by H, a non-cyclic substituted or unsubstituted aliphatic group, substituted or unsubstituted alicyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted heteroarylalkyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl, Tert-butyloxycarbonyl, 9-fluorenylmethyloxycarbonyl (Fmoc) and R5—CO—, wherein R5 is selected from the group formed by H, a non-cyclic substituted or unsubstituted aliphatic group, substituted or unsubstituted alicyclyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl, substituted or unsubstituted heterocyclyl and substituted or unsubstituted heteroarylalkyl; R2 is selected from the group formed by —NR3R4, —OR3 and —SR3, wherein R3 and R4 are independently selected from the group formed by H, a non-cyclic substituted or unsubstituted aliphatic group, substituted or unsubstituted alicyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted heteroarylalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted aralkyl; and with the condition that R1 and R2 are not α-amino acids.
“Fragment” means a segment of a protein selected from SEQUENCE ID NO's, the fragment typically being contiguous amino acids in length.
“C-terminal domain” as applied to a fragment means the first three amino acids at the c-terminus of the fragment.
“N-terminal domain” as applied to a fragment means the last three amino acids at the n-terminus of the fragment.
A “variant” is a peptide that is altered in respect of one or more amino acid residues. Preferably such alterations involve the insertion, addition, deletion and/or substitution of 5 or fewer amino acids, more preferably of 4 or fewer, even more preferably of 3 or fewer, most preferably of 1 or 2 amino acids only. Insertion, addition, and substitution with natural and modified amino acids is envisaged. The variant may have conservative amino acid changes, wherein the amino acid being introduced is similar structurally, chemically, or functionally to that being substituted. Generally, the variant will have at least 70% amino acid sequence homology, preferably at least 80% sequence homology, more preferably at least 90% sequence homology, and ideally at least 95%, 96%, 97%, 98% or 99% sequence homology with the reference growth promoting fragment. The variant may include a fragment of the peptide wherein one or more amino acids are deleted. The variant may have 1 to 3 amino acid changes selected from insertion, addition, deletion, and substitution. The variant may have ACE-1 inhibitory activity and/or renin inhibitory activity. Methods to determine these activities are described herein.
“Man-made” as applied to comestible products should be understood to mean made by a human being and not existing in nature.
The term “marine peptide product” is one or more peptides derived from a marine by-product.
The term “marine by product” is a product or discard generated as a result of fish processing, e.g., such filleting. The by products include but are not limited to bloodwaters, fish skin, fish bone and gut waste.
The term “pelagic fish” refers to fish derived from the pelagic zone of the ocean or lake water. Examples include but are not limited to white fish, blue whiting and mackerel.
The term “whitefish” refers to various freshwater salmonid food fish, e.g. genera Coregonus and Prosopium. They have an adipose dorsal fin and inhabit cold lakes and streams.
The term “retentate” is the by-product, or processed by-product, retained by the membrane.
The term “bloodwater” refers to the blood from fish released during fish processing.
The term “fish processing” refers to the processes associated with fish and fish products between the time fish are caught or harvested, and the time that the final product is delivered to the customer. It can extend to any aquatic organism, preferably fish in this context.
The “animal” when used herein may be any animal. Preferably, the animal is a companion animal. Still preferred the animal is a dog or a cat. It may be a rabbit, a hamster, a horse, a guinea pig, a rat, a mouse or a reptile. The animal may be any age. Typically, the animal is an elderly animal. An “elderly animal” is one 8 years and older, typically from 8 to 13 years old.
The term “companion animal” when used herein is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock or a laboratory animal.
The invention will now be described with reference to the following figures in which;
The current invention relates to a marine peptide product, obtained from the by-products of fish processing. The current inventors have discovered that marine peptide products obtained from fish processing by-products contain peptides which impart health benefits, allowing them to produce a functional food product for animals, as an alternative to “traditional” drugs for prevention or treatment of disease. Notably, the marine peptide product comprises valuable amino acid rich proteins that contain all the essential amino acids. Most notably, the marine peptide product comprises peptides with ACE-1 inhibitory activity.
The food product of the invention not only has health benefits, but it also has a desirable appearance, taste, strength, and texture. Undesirable colour often renders the product undesirable to the dog owner. Notably, the food product of the invention may be a low-calorie food product. The food product is high in total protein content, high in essential amino acid content, high in heart health benefits. In a preferred embodiment, the food product is a dog food product, typically a biscuit.
In an embodiment, the food product may be a biscuit or similar, and may comprise a substitution of a portion of the wheat flour normally used to make a biscuit of this nature, with the protein product of the invention. This can be carried out to accomplish a variation in the protein content and calorie content and the health benefits of the biscuit to the animal. In other words, the amount of the marine peptide product in the biscuit, or indeed any food product of the invention, can be varied depending on the desired type or composition of the biscuit or the intended use of the biscuit. In the prior art, substitution of wheat flour with another ingredient can cause difficulties in the manufacturing of dog biscuits so that texture and appearance of the final product is affected. However, this is not the case when using the marine peptide product of the invention.
The marine peptide product of the invention comprises peptides that can be derived from by-products of fish processing. In this regard, the invention provides a method for producing a marine peptide product from by-products of fish processing. The marine peptide product is the retentate or fraction obtained in the method. The fraction is the permeate.
In one embodiment of the invention, the by-products are captured before they reach the (Dissolved Air Flotation (DAF) systems) system in a fish processing plant and to utilise recovered solids as a source of proteins and amino acids. In one embodiment of the invention, bloodwaters are captured from the tanker, hopper and process lines. Solids are recovered and stored at −4° C. in containers and then passed through a membrane filtration system incorporating 3 kDa and/or 10 kDa fractions that can recover proteins and peptides and fatty acid methyl esters (retentate fraction) and 3 kDa and 10 kDa fractions containing both amino acids and bioactive peptides with potential to impact positively on heart health (through Angiotensin-1-converting enzyme I inhibition—as these fractions contain ACE-I inhibitory peptides).
In an embodiment, the method comprises filtering the bloodwaters from fish processing, e.g., pelagic or white fish processing, with a 3 kDa and/or a 10 kDa membrane, to obtain at least one retentate, a 3 kDa fraction and/or a 10 kDa fraction, each with a particular peptide and amino acid composition. For instance, if a 3 kDa membrane is used, there is a 3 kDa fraction which contains the peptides and a retentate. If a 10 kDa membrane is used, there is a 10 kDa fraction which contains the peptides and there is also a retentate. If both a 3 kDa and 10 kDa membrane is used there will be a retentate for each membrane used.
The retentate and fractions may then be dried. The method of drying may be any suitable method and such methods are known to the skilled person.
In one embodiment, the bloodwaters are filtered through a 3 kDa membrane and a 10 kDa membrane, to obtain a retentate, a 3 kDa fraction and a 10 kDa fraction. The by-products may pass through the membranes at the same time, or it may be sequentially.
In one embodiment, the bloodwaters are filtered through a 3 kDa membrane only.
In one embodiment, the bloodwaters are filtered through a 10 kDa membrane only.
In an embodiment, the pelagic fish is selected from the group comprising mackerel, Blue-whiting, and Horse mackerel. It may be one or more pelagic fish. Preferably, the fish is blue whiting or mackerel.
This exemplary method is illustrated in
In a notable embodiment of this invention, the by-product may be one or more of fish skin, bone and gut waste. The by-product may be obtained from processing of any type of fish, e.g., filleting. Pelagic and white fish are two preferred examples. However, it may be any fish from which collagen/gelatine may be obtained. When the by-product used is one or more of fish skin, bone and gut waste, the method comprises an optional first step of extracting gelatine from the by-product prior to the filtering step.
Any method of extracting gelatine may be used, and such are well known in the art. In an embodiment, of the invention, the gelatine step may include a first “pre-treatment” step as disclosed herein. The extracted gelatine is hydrolysed prior to filtering.
In an embodiment, gelatine does not require extraction. It is possible to hydrolyse the by-product without first extracting the gelatine to provide a hydrolysate. In this embodiment, the hydrolysate is then filtered as per the steps of the method of the invention. The enzymes used are those as described herein.
In a method of the invention, the hydrolysed gelatine, or hydrolysate, may be filtered through a 3 kDa membrane and a 10 kDa membrane to obtain a retentate, a 3 kDa fraction and a 10 kDa fraction. The hydrolysed gelatine, or hydrolysate, may pass through the membranes at the same time, or it may be sequentially.
In one embodiment, the hydrolysed gelatine, or hydrolysate, is filtered through a 3 kDa membrane only.
In one embodiment, the hydrolysed gelatine, or hydrolysate, is filtered through a 10 kDa membrane only.
The flow rate is typically between 20 L per hour and 50 L per hour, typically around 37.5 L per hour.
The method of any embodiment of the invention, after the filtering step, may further comprise a step of freezing, preferably blast freezing, the permeates and retentates. This step is preferred when the product is dried.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 1 to SEQUENCE ID NO. 188, or a variant thereof.
Preferably, the one or more peptides has ACE-1 inhibitory activity. Typically, the one or more peptides has renin inhibitory activity.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 1 to SEQUENCE ID NO. 64, or a variant thereof. In an embodiment the product may comprise (or consist of) all of the peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 1 to SEQUENCE ID NO. 64, or variant thereof. In an embodiment, the peptide product may comprise one or more of, or all of, the peptides comprising (or consisting of) SEQUENCE ID NO 1 to 15. These peptides may be obtained from marine by-products, bloodwaters from blue whiting processing. The peptides have a molecular weight less than or equal to 10 KDa.
Preferably, the one or more peptides is selected from SEQUENCE ID NO. 1, 2, 10, 13, 16, 22, 25, 32, 44, 57, 58, 64 and 62 or a variant thereof. All of the peptides may be present.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 65 to SEQUENCE ID NO. 169, or a variant thereof. In an embodiment the product may comprise (or consist of) all of the peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 65 to SEQUENCE ID NO. 169 or a variant thereof. In an embodiment, the peptide produce may comprise one or more of, or all of, the peptides comprising (or consisting of) SEQUENCE ID NO. 65 to 74. These peptides may be obtained from marine by-products, typically bloodwaters from mackerel processing. The peptides have a molecular weight less than or equal to 10 KDa.
Preferably, the one or more peptides is selected from SEQUENCE ID NO. 122, 123, 133, 139, 141, 147, 148, 150, 152, 157 and 160 or a variant there of. All of the peptides may be present.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 170 to SEQUENCE ID NO. 188, or a variant thereof. In an embodiment the product may comprise (or consist of) all of the peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 170 to SEQUENCE ID NO. 188 of a variant thereof. In an embodiment, the peptide product may comprise one or more of, or all of, the peptides comprising (or consisting of) SEQUENCE ID No. 170 and 171. These peptides may be obtained from marine by-products, typically blood water from mackerel processing. The peptides have a molecular weight greater than 10 KDa.
Preferably, the one or more peptides is selected from SEQUENCE ID NO. 170, 171, 178, 182, 183, 187, 185, 184 and 186 or a variant thereof. All of the peptides may be present.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 189 to SEQUENCE ID NO. 271, or 363 or a variant thereof. In an embodiment the product may comprise all of the peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 189 to SEQUENCE ID NO. 271 or 363 or a variant thereof. The peptide product is a hydrolysed product. The peptides are those obtained from marine by-products, typically skin and bones from blue whiting surimi processing. The peptides have a molecular weight less than or equal to 3 KDa.
In an embodiment, the marine peptide product comprises one or more peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 272 to SEQUENCE ID NO. 362, or a variant thereof. In an embodiment the product may comprise all of the peptides comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 272 to SEQUENCE ID NO. 362. The peptide product is a hydrolysed product. The peptides are those obtained from marine by-products, typically skin and bone from blue whiting surimi processing. The peptides have a molecular weight less than or equal to 3 KDa.
Typically, said peptide comprises a maximum 50 amino acids in length. Preferably from about 10 to about 20 amino acids in length.
The marine peptide product may comprise at least 1, preferably at least 2, preferably at least 3, preferably at least 4, preferably at least 5, preferably at least 6, preferably at least 7, preferably at least 8, preferably at least 9, or preferably at least 10 peptides, or preferably at least 20, 25, 30, 35, 45 peptides selected from a peptide comprising (or consisting of) SEQUENCE ID NO. 1 to SEQUENCE ID NO. 188, or a variant thereof.
In one embodiment, the marine peptide product comprises at least one or more of a peptide comprising (or consisting of) SEQUENCE ID NO. 1, SEQUENCE ID NO 2, SEQUENCE ID NO 3, SEQUENCE ID NO 4, SEQUENCE ID NO 5, SEQUENCE ID NO 6, SEQUENCE ID NO 7, SEQUENCE ID NO 8, SEQUENCE ID NO 9, SEQUENCE ID NO 10, SEQUENCE ID NO 11, SEQUENCE ID NO 12, SEQUENCE ID NO 13, SEQUENCE ID NO 14 and SEQUENCE ID NO 15. In one embodiment, the marine peptide product comprises at least all of the peptides comprising (or consisting of) SEQUENCE ID NO. 1, SEQUENCE ID NO 2, SEQUENCE ID NO 3, SEQUENCE ID NO 4, SEQUENCE ID NO 5, SEQUENCE ID NO 6, SEQUENCE ID NO 7, SEQUENCE ID NO 8, SEQUENCE ID NO 9, SEQUENCE ID NO 10, SEQUENCE ID NO 11, SEQUENCE ID NO 12, SEQUENCE ID NO 13, SEQUENCE ID NO 14, and SEQUENCE ID NO 15. The product may comprise one or more additional peptides of the invention.
In one embodiment, the marine peptide product comprises at least one or more of a peptide comprising (or consisting of) SEQUENCE ID NO. 65, SEQUENCE ID NO 66, SEQUENCE ID NO 67 SEQUENCE ID NO 68, SEQUENCE ID NO 69, SEQUENCE ID NO 70, SEQUENCE ID NO 71, SEQUENCE ID NO 72, SEQUENCE ID NO 73, and SEQUENCE ID NO 74. In one embodiment, the marine peptide product comprises at least all of the peptides comprising (or consisting of) SEQUENCE ID NO. 65, SEQUENCE ID NO 66, SEQUENCE ID NO 67 SEQUENCE ID NO 68, SEQUENCE ID NO 69, SEQUENCE ID NO 70, SEQUENCE ID NO 71, SEQUENCE ID NO 72, SEQUENCE ID NO 73, and SEQUENCE ID NO 74. The product may comprise one or more additional peptides of the invention.
In one embodiment, the marine peptide product comprises at least one or more of a peptide comprising (or consisting of) SEQUENCE ID NO. 170 and SEQUENCE ID NO 171. In one embodiment, the marine peptide product comprises at least the peptides comprising (or consisting of) SEQUENCE ID NO. 170 and SEQUENCE ID NO 171. The product may comprise one or more additional peptides of the invention.
In one embodiment, the peptide of the invention is modified. In one embodiment the peptide is modified with a protecting group. In one embodiment, the peptide is modified to increase its lipophilicity. In one embodiment, the peptide is modified to increase its half-life. In one embodiment, an N or C-terminal amino acid of the peptide is modified. In one embodiment, the N or C-terminal amino acid of the peptide is modified with a protecting group.
The invention provides a peptide comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 1 to SEQUENCE ID NO. 363, or a variant thereof.
The invention provides a peptide comprising (or consisting of) a sequence selected from SEQUENCE ID NO. 1 to SEQUENCE ID NO. 188, or a variant thereof.
Preferably, the peptide is selected from SEQUENCE ID NO. 1, 2, 10, 13, 16, 22, 25, 32, 44, 57, 58, 64 and 62 or a variant thereof.
Still preferred, the peptide is selected from SEQUENCE ID NO. 122, 123, 133, 139, 141, 147, 148, 150, 152, 157 and 160 or a variant thereof.
In an embodiment, the peptide is selected from SEQUENCE ID NO. 170, 171, 178, 182, 183, 187, 185, 184 and 186 or a variant thereof.
The invention provides a marine peptide product obtained by the method of the invention. The peptide product may be one comprising peptides of 3 kDa or less. The peptide product may be one comprising peptides of 10 KDa or less, or from 3 kDa to 10 kDa. The peptide product may be one comprising peptides greater than 10 KDa. The marine peptide product may be one obtained from skin and/or bone derived from processing of blue whiting into surimi products. Alternatively, the marine peptide product may be one obtained from bloodwater from pelagic or whitefish processing.
In an embodiment, the invention provides a marine peptide product comprising a 10 kDa fraction obtained from bloodwater. The bloodwater may be from pelagic fish processing, such as mackerel and blue whiting.
In an embodiment, the invention provides a marine peptide product comprising a 3 kDa fraction obtained from by-products of fish processing, in which the by product is gelatine extracted from fish by products selected from the group comprising fish skin, fish bones and gut waste. The fish may be any collagen containing fish, such as blue whiting. The fish processing may be blue whiting processing into surimi products.
Preferably, the marine peptide product may further comprise at least one fatty acid. The fatty acids may be one or more of the fatty acids listed in Table 5. The fatty acid may be all of the fatty acids listed in Table 5.
The peptide product of the invention has a particular peptide and amino acid composition. For example, the essential, non-essential and conditionally essential quantities for bloodwaters are illustrated by
In one embodiment, the total amino acid content of mackerel bloodwater hkDa permeate extract (Mackerel) was determined as 199.94 g/kg DW and the content of bloodwater 10 kDa (blue whiting) was determined as 35.31 g/kg DW with the essential amino acid composition approximately 30.41% of the total amino acid composition for Mackerel 10 kDa and 24.62% for Blue whiting 3 kDa, respectively.
The level of the essential amino acids lysine and methionine contained in Mackerel 10-kDa blood-water extracts were comparable to flaxseed protein sources (Ufaz & Galili, 2008) but less than whey protein isolate. The blue-whiting 10-kDa permeate fraction was rich in taurine (14.977 g/Kg D) as was the Mackerel 10-kDa permeate (63.411 g/kg D and taurine levels in all retentates and permeate fractions were greater than either whey protein isolate or flaxseed protein isolate with the exception of the 3 kDa fraction for Mackerel.
These results are outlined in Table below, which shows the content of amino acids in bloodwater retentate fraction, 10 kDa fraction (mackerel and blue whiting), 3 kDa fraction, whey protein isolate and flax.
Table 1: Amino Acids
The levels of taurine in fish bloodwater fractions analysed in BBPP were between 0.2 to 2 g/100 g, which is considerably high compared to beef and pork muscle with taurine content of 50-100 mg/100 g and 118 mg/100 g, respectively. A variety of studies have identified the beneficial effects of taurine in the treatment of cardiovascular diseases, renal dysfunction, and retinal neuron damage and these bloodwaters could be useful in the development of complementary pet foods such as treats to enhance taurine levels for improved heart heath and renal function.”.
A still further aspect provides a food product, or comestible product, comprising the marine peptide product obtained by the method of the invention. The food product is preferably a biscuit for consumption by a dog or cat. The biscuit may be any colour or shape.
An aspect of the invention provides a marine peptide product or food product of the invention, for use in a method of treatment or prevention of disease in an animal, typically prevention. As shown in the accompanying examples, the marine peptide product of the invention has ACE-1 inhibition activity. The marine peptide product also has Renin inhibition activity. Therefore, it has an application for prevention or treatment of heart disease or renal disease in animals, particularly cats and dogs. The food product of the invention is intended as a functional food product and could be used as an alternative to traditional drugs or medicine.
Notably, the current invention provides the use to treat or prevent hypertension in elderly animal, preferably dogs. Typically, this may be hypertension that has resulted from obesity, inflammation and/or proteinuria in the animal. In dogs with marked proteinuria ACE-1 inhibitors may also have reno-protective effects and reduce the magnitude of proteinuria.
A method of treatment or prevention of a disease in an animal is also provided by the current invention comprising administration of the peptide product or peptide of the current invention to an animal. The disease may be selected from the group comprising heart disease and renal disease or an inflammatory disease or condition. The condition may be high blood pressure or hypertension or proteinuria. The heart disease may be selected from the group comprising, but not limited to, chronic heart failure (CHF), chronic valvular disease, hypertrophic cardiomyopathy, mitral valve regurgitation (MR), e.g., secondary to degeneration of the mitral valve apparatus, one associated with a metabolic syndrome, for examples, heart health or congestive heart failure and chronic renal failure (CRF).
It will be appreciated that other ingredients or additives may be added to the food product of the invention. For example, an aroma enhancing ingredient, e.g. Fats (fish derived or tallow) can be added for aroma enhancement.
Unlike conventional biscuit formulas, no salt is added in the most preferred embodiments of this invention. This embodiment of the invention provides higher quality protein or essential amino acids compared to traditional wheat flour biscuits. The total protein content of the biscuit embodiments can be selectively adjusted to provide eye health (cats) or heart health (dogs) benefits.
Also provided is a method for producing a marine peptide product from a mackerel by-product derived from fish processing, the method comprising: hydrolysing the mackerel by-product, which is one or more of fish skins, fish bone and gut waste, with one or more hydrolyses enzymes selected from alcalase and papain, using one or more filters selected from 3 kDa filter membrane and 10 kDa filter membrane, to obtain at least one retentate, a 3 kDa fraction and/or a 10 kDa fraction, wherein the marine peptide product is the obtained fraction(s).
The invention will now be described with reference to the following examples.
Sampling and Stabilisation of Pelagic Blood-Waters
One litre (1 L)×3 samples of either Refrigerated seawater (RSW) from the supply tanker, hopper or process-line containing fish blood from Mackerel, Blue-whiting or Horse mackerel were collected independently from five different processors (Table 2) during the period September-April 2016-2017. Samples were collected in 1 L bottles and transported immediately to the laboratory on ice where they were frozen at −80° C. and subsequently freeze-dried using an industrial scale FD 80 model freeze-drier (Cuddon Engineering, New Zealand), milled and stored at −20° C. until further use. The dry matter content of the samples was calculated following drying. The pH of the samples was determined at 20° C. using pH standard pH meter and a calibrated Hamilton double pore electrode.
Up-Scaled Fractionation of Bloodwaters Using Molecular Weight Cut Off Filtration (MWCO) Skid System
The concentration SKID (FDT engineering, Ireland) shown in
Total Protein and Polypeptide Profile
The total protein content of all samples was analysed using the Bicinchoninic Acid Assay (BCA assay) using bovine serum albumin as a standard. In addition, proximate analysis was used to quantify protein, ash and lipid content of the samples. The total protein content was determined in triplicate using a LECO FP628 Protein analyser (LECO Corp., MI, USA) based on the Dumas method and according to AOAC method 992.15, 1990. The conversion factor of 6.25 was used to convert total nitrogen to protein. The total protein content and yields were calculated per litre of blood and are shown in
Physical and Chemical Properties Determination of Blood Water Fractions
Proximate Analysis
The yield of stabilized products was calculated after freeze-drying and weighing of the samples and is expressed as a percentage of the product in total mass of initial blood water. The total protein content of the samples was determined using the Dumas combustion method using a LECO FP328 Protein analyser (LECO Corp, MI USA), according to Association of Official Analytical Chemists (AOAC) method 992.15 (AOAC, 1990). The conversion factor of 6.25 was used to convert total nitrogen to protein.
The ash content was determined gravimetrically, as previously described (Kolar, 1992).
The total fat content was determined gravimetrically using Ankom XT15 Extractor (Ankom Technology, Macedon NY, USA) for lipid extraction, after previous acid hydrolysis using Ankom HCl Hydrolysis System according to manufacturers' operating manual.
Water Activity
Water activity (aw) of all samples was measured using an AquaLab Lite meter (Decagon Devices Inc., Germany). Approximately 0.25 g of finely powdered sample was placed in the water activity metre and aw and the temperature was recorded.
Total and Amino Acid (TAA) Analysis of Samples
For total amino acid composition analysis, recovered blood-water samples were hydrolyzed in 6M HCl at 110° C. for 23 hours following the method of Hill (1965). Samples were then de-proteinised by mixing equal volumes of 24% (w/v) tri-chloroacetic acid (TCA) and sample, these were allowed to stand for 10 minutes before centrifuging at 14400×g (Microcentaur, MSE, UK) for 10 minutes. Supernatants were removed and diluted with 0.2 M sodium citrate buffer, pH 2.2 to give approximately 250 nmol of each amino acid residue. Samples were then diluted 1 in 2 with the internal standard norleucine, to give a final concentration of 125 nm/mL. Amino acids were quantified using a Jeol JLC-500N amino acid analyser (Jeol (UK) Ltd., Garden city, Herts, UK) fitted with a Jeol Na+ 133 high performance cation exchange column.
Fatty Acid Methyl Ester (FAME) Analysis
Lipids from samples of Blue whiting and Mackerel 3 KDa and 10 KDa permeates and retentates were extracted using ethanol and ethyl acetate mixture (1:1, w/w), as described by Lin et al. (2004). Extracted lipids were then directly converted to FAMEs using boron-trichloride in methanol (14%, w/v) without previous derivatization, with slight modifications of the method previously described by Araujo et al. (2008). Separation and analysis of the FAMEs was done using Agilent 7890A/5975C GC-MSD system (Agilent Technologies, Santa Clara, CA, USA) equipped with Agilent J&W DB-FastFAME column (30 m×0.25 mm, 0.25 μm). Slightly modified method from Agilent Application note 5991-8706EN was used for analysis (Zou and Wu, 2018). Hydrogen was used as carrier gas in constant pressure mode at 8 PSI and sample injection volume was 1 μL in inlet split mode (25:1). Temperature program of oven was as follows: 50° C. (0.5 minutes), then 15° C./min to 194° C. (4 minutes) and finally 4° C./min to 240° C. (1 minute). Mass spectra were acquired in scan mode in the 40-550 AMU mass range.
Chromatographic peaks (total ion chromatogram, TIC) were identified by comparison of retention times (RT) and mass spectra with peaks of analysed FAMEs in the standard mixture. Identification was confirmed by searching the generated MS spectra within available spectral database (NIST11) using Agilent ChemStation software (v X.XX). Supelco Fame 37 mix (Sigma Aldrich, Darmstadt, Germany) was utilized for external calibration by making series of appropriate dilutions with hexane, with individual compound peaks used to construct a five-point calibration curve. Each individual FAME is quantified by measuring response (peak area after integration) of a selected quantifier ion from the compound spectrum using ChemStation software. 1 ml of glyceryl-tri-heptadecanoate (Sigma Aldrich, Darmstadt, Germany) in hexane (1 mg/ml, w/v) was added to lipid samples prior to derivatization, to correct for transesterification efficiency and procedural losses. All samples were analysed in triplicates and results expressed as concentration (mg/g) of each fatty acid in extracted fat.
Determination of Techno-Functional Properties
Water and Oil Holding Capacities
The water holding capacity (WHC) and oil holding capacity (OHC) were measured using the modified methods described by Garcia-Vaquero et al. (2017). In brief, 100 mg of each fraction sample was mixed with 1 ml of distilled water or oil (olive and sunflower oil) using a vortex mixer (VV3, VWR International Ltd., Ireland) for 30 seconds. The suspension was then centrifuged at 2200×g for 30 min (Eppendorf MiniSpin, Eppendorf UK Limited, United Kingdom) at 19° C. The supernatant was then decanted by draining the tubes at 45° angle for 10 min (20 min for oil). Water/oil holding capacity was calculated by dividing the weight of water/oil absorbed by the weight of the protein sample and expressed as grams of water or sunflower oil held by 1 g of protein.
Solubility
Solubility in water (S) was determined using the modified method by Ogunwolu et al. (2009). 100 mg of each sample was dispersed in 10 ml deionised water. Using pH-meter, the pH of the dispersions was adjusted to 2, 4, 6, 8 and 10 with 0.1 N HCl and 0.1 N NaOH. The mixture was vortexed at room temperature (19-20° C.) for 5 min, and subsequently centrifuged at 7500×g for 15 min (Lynx 6000, Thermo Fisher Scientific, MA USA). The protein content in the supernatant was determined using the Pierce™ BCA Protein Assay Kit (Thermo Fischer Scientific, MA, USA). Solubility of samples at different pH conditions was then calculated as:
S (%)=(protein content in the supernatant/protein content in full dispersion)×100.
Foaming Capacity
The foaming capacity (FC) of the blood water permeates and retentate samples were determined by the modified method described by Garcia-Vaquero et al. (2017). Samples were suspended in deionized water to make 1% concentration (w/v) and the pH was adjusted to 2, 4, 6, 8 and 10 with 0.1 N HCl and 0.1 N NaOH. The suspensions were homogenized using a T 25 digital ULTRA-TURRAX® homogenizer (IKA®, Germany) (10,000 rpm; 1 min) and the volume of produced foam was measured in a graduated 50 ml Falcon tube. FC was calculated as the volume of foam using the formula:
FC (%)=(Vf−V0)V0×100
where; V0 is the initial volume of protein solution before homogenization and Vf is the volume of foam produced after homogenization. The foaming stability (FS) was calculated using the same formula, with Vf measured after 15, 30 and 60 min.
Emulsifying Activity and Emulsifying Stability
The emulsifying activity (EA) of the blood water permeates and retentate samples were determined using a modified method of Garcia-Vaquero et al. (2017). Each sample was suspended in deionized water to make 1% concentration (w/v) and the pH was adjusted to 2, 4, 6, 8 and 10 with 0.1 N HCl and 0.1 N NaOH. The solution was homogenized for 30 s at 14,000 rpm using a T 25 digital ULTRA-TURRAX® homogenizer (IKA®, Germany). The emulsion was created by addition of sunflower oil to aqueous phase (oil:sample solution=3:2) in 50 ml Falcon tubes. The oil was added in two steps: half of the volume was first added, and the mixture was homogenized 30 s at 14000 rpm, after which the rest of the oil was added and homogenization was repeated for 90 s at the same speed. The tubes containing emulsion were then centrifuged at 1100×g for 5 min and the volume of the emulsion layer was recorded. Emulsifying activity was calculated by the formula:
EA (%)=(Ve/Vt)×100
Being Ve the volume of the emulsion layer after centrifuging and Vt the all volume inside the tube. Emulsion stability (ES) was determined by heating the previously prepared emulsions at 85° C. for 15 min, cooling at room temperature for 10 min and centrifuging again 1100×g for 5 min. The ES was calculated and expressed as the % of EA after heating and centrifuging centrifuging by the formula:
ES (%)=(Vemulsion after heating/Voriginal emulsion)×100
ACE-I Inhibition Assay
ACE-I (angiotensin-converting enzyme 1) inhibition bioassay of permeate and retentate samples (Mackerel and Blue whiting) was carried out according to the manufacturer's instructions (ACE Kit—WST, Dojindo Laboratories, Kumamoto, Japan). In brief, 20 μL of each sample aqueous solution at a concentration of 1 mg/mL was added to 20 μL substrate and 20 μL enzyme working solution in triplicate. Captopril was used as a positive control. Samples were incubated at 37° C. for 1 h. A 200 μL of indicator working solution was then added to each well, and subsequent incubation at room temperature was carried out for 10 min. Absorbance at 450 nm was read using a FLUOstarOmega microplate reader (BMG LABTECH GmbH, Offenburg, Germany). The percentage of inhibition was calculated using the following equation:
% ACE-I inhibition=100% Initial activity−Inhibitor×100/100% Initial activity
Renin Inhibition Assay
Renin inhibition activity of permeates and retentate fractions was tested in vitro for renin. The bioassay was carried out according to the manufacturer's instructions (Renin Inhibitor Screening Assay Kit, Cayman chemical, Ann Harbor, MI, USA). In brief, 10 μL of each fraction solution in dimethyl-sulfoxide (DMSO) at a concentration of 1 mg/mL was added to 20 μL substrate and 150 μL of assay buffer in triplicate. Renin was then added to 100% initial activity and inhibitor wells, the wells were shaken for 10 seconds and incubated at 37-C for 15 min. Fluorescence (excitation at 345 nm and emission at 490 nm) was read using a FLUOstarOmega microplate reader (BMG LABTECH GmbH, Offenburg, Germany). The percentage of inhibition was calculated using the following equation:
% Renin inhibition=100% Initial activity−Inhibitor×100/100% Initial activity
Peptide Identification by Tandem Mass Spectrometry
The nano-LC-MS/MS analysis was performed using an Eksigent Nano-LC Ultra 1D Plus system (Eksigent of AB Sciex, CA) coupled to the quadrupole-time-of-flight (Q-ToF) TripleTOF® 5600 system from AB Sciex Instruments (Framingham, MA) that is equipped with a nano-electrospray ionization source.
Samples were re suspended in 50 μL of 0.1% TFA in 2% ACN. 2 μl of every sample were loaded onto a trap column (Nano-LC Column, 3μ C18-CL, 350 μm×0.5 mm; Eksigent) and desalted with 0.1% TFA at 3 μl/min during 5 min. After 5 min of preconcentration, the trap column was automatically switched in-line onto a nano-HPLC capillary column (3 μm, 75 μm×12.3 cm, C18) (Nikkyo Technos Co, Ltd. Japan). Mobile phase A contained 0.1% v/v formic acid in water, and solvent B, contained 0.1% v/v FA in 100% acetonitrile. A linear gradient from 5% to 35% of solvent B over 60 min at a flow rate of 0.3 μL/min and running temperature of 30° C. was used for chromatographic separations.
The column outlet was directly coupled to a nano-electrospray ion (nESI) source. Operating conditions for the Q/ToF mass spectrometer were positive polarity and data-dependent mode. Sample was ionized applying 2.8 kV to the spray emitter. Survey MS1 scans were acquired from 350-1250 m/z for 250 ms. The quadrupole resolution was set to ‘UNIT’ for MS2 experiments, which were acquired 100-1500 m/z for 50 ms in ‘high sensitivity’ mode. Following switch criteria were used: charge: 1+ to 5+; minimum intensity; 70 counts per second (cps). Up to 25 ions were selected for fragmentation after each survey scan. Dynamic exclusion was set to 15 s. The system sensitivity was controlled with 2 fmol of 6 standard proteins (LC Packings).
Data Analysis
Automated spectral processing, peak list generation, and database search for the identification of the peptides were performed using Mascot Distiller v2.7.1.0 software (Matrix Science, Inc., Boston, MA) (hppt://www.matrixscience.com) using MascotServer v2.6 (Matrix Science, Inc., Boston, MA) (hppt://www.matrixscience.com).
The UniProt protein database was used to identify the peptides with a significance threshold p<0.05. Used taxonomy for the identification in database was chordata organisms. The tolerance on the mass measurement was 0.3 Da in MS mode and 100 ppm in MS/MS ions.
In Silico Digestion of Identified Peptides
The identified peptides were digested in silico using BioPep online analysis tools (http://www.uwm.edu.pl/biochemia/index.php/en/biopep), with pepsin (EC 3.4.23.1), trypsin (EC 3.4.21.4) and chymotrypsin A (EC 3.4.21.1) in order to simulate gastric digestion process (Minkiewicz et al., 2008). The results of in silico enzyme hydrolysis was then searched for active fragments in BioPep database to identify potential ACE-I inhibitory peptides that may be released during digestion.
Results
Yield and Proximate Composition of Blood Water Fractions
The freeze-dried filtration fractions had a wide range of protein content, with Blue whiting 3 KDa permeate (BW 3 KDa) containing only 11.1 (±1.53) % of protein, up to 40.5 (±0.16) % in Markerel 10 KDa permeate (Mac 10 KDa) sample. Other filtration fractions, Blue whiting 10 KDa permeate (BW10 KDa), Blue whiting retentate (BW Ret), Mackerel 3 KDa permeate (Mac 3 KDa) and Mackerel retentate (Mac Ret) had protein content between those values (13.3±2.17%, 28.9±0.78%, 21.5±0.84% and 29.9±0.45%, respectively). All permeate fractions had a low lipid content (<1%), while BW Ret and Mac Ret had 1.55 (±0.20) % and 1.69 (±0.11) % fat, respectively. All dried fractions had ash content over 50%, with BW 3 KDa and BW 10 KDa containing over 70% (73.0±0.98% and 75.8±2.01%, respectively) and Mac 3 KDa containing 67.4±1.91% ash. Bw Ret and Mac Ret retentate fractions and Mac 10 KDa permeate fraction contained similar ash content (50.2±0.31%, 51.9±0.49% and 53.0±0.18%, respectively). All the tested fractions had water activity (Aw) values below 0.3, which indicates proper drying of the samples and ensures good microbial stability.
The total amino acid (TAA) content of Mackerel blood water fractions is presented in Table 3. The Mac Ret and Mac 10 KDa samples had significantly higher total amino acid content (144.7 and 199.9 g/Kg, respectively) than Mac 3 KDa fraction (65.9 g/Kg). Most abundant detected amino acids were taurine (25.1 g/Kg, 63.4 g/Kg and 2.84 g/Kg in Mac Ret, Mac 10 KDa and Mac 3 KDa, respectively), asparagine (15.3 g/Kg, 8.38 g/Kg and 0.59 g/Kg in Mac Ret, Mac 10 KDa and Mac 3 KDa, respectively) and glutamic acid (13.3 g/Kg, 12.3 g/Kg and 1.20 g/Kg in Mac Ret, Mac 10 KDa and Mac 3 KDa, respectively). All essential amino acids were detected in samples, except tyrosine and tryptophan (which is degraded by acid hydrolysis during sample preparation), with significant concentration of lysine (8.57 g/Kg, 12.2 g/Kg and 0.91 g/Kg in Mac Ret, Mac 10 KDa and Mac 3 KDa, respectively) in all samples.
The fatty acid (FA) profile of Mackerel and Blue whiting retentates and 10 KDa permeate fractions is presented in Table 5. The content and profile of detected fatty acids differ significantly between all samples. The Mac Ret sample had 142 (±11.3) mg of fatty acids per gram of sample, with principal fatty acids being saturated FAs C4:0 (butyric acid, 115±9.44 mg/g lipid) and C8:0 (caprylic acid, 17.5±1.26 mg/g lipid). Main unsaturated fatty acids in this sample, DHA (C22:6) and palmitoleic acid (C16:1), were both present in concentrations below 1 mg/g lipid (0.74±0.13 and 0.45±0.04 mg/g lipid, respectively). The FAMEs profile of Blue whiting retentate (BW Ret), however, is dominated by unsaturated fatty acids (UFAs), which are present at concentration 220 (±16.0) mg/g lipid in contrast to low concentration of saturated fatty acids (SFA, 57.9±3.79 mg/g lipid). Most abundant unsaturated fatty acids in the BW Ret sample are DHA (C22:6; 111 8.44 mg/g lipid), oleic acid (C18:1 c; 42.8±2.54 mg/g lipid) and EPA (C20:5 n3; 21.6±1.78 mg/g lipid); while stearic acid (C18:0) and myristic acid (C14:0) are the most abundant SFAs (9.68±0.74 and 4.24±0.35 mg/g lipid, respectively). The analysed permeate fractions (Mac 10 KDa and BW 10 KDa) contained only low concentrations of caprilyc acid (in Bw 10 KDa, at 0.49±0.06 mg/g lipid) or combination of caprilyc and capric acid (in Mac 10 KDa, at 105±4.22 and 55.3±1.67 mg/g lipid, respectively).
1Total fatty acids;
2saturated fatty acids;
3unsaturated fatty acids;
4monounsaturated fatty acids;
5polyunsaturated fatty acids
The total fatty acids (TFA) content of all the fractions analysed ranged between 293+/−27.6 and 981+/−29.4 mg/g. Unsaturated fatty acids (UFAs) contributed between 167.3+/−9.45 and 786+/−22.6 mg/g of the above total whereas polyunsaturated fatty acids (PUFAs) ranged from 75.71+/−6.15 to 479.9+/−8.94 mg/g. All the samples analysed had a higher content of unsaturated fatty acids compared to their saturated counterparts. The whole fraction of the sample collected on the 30/01/20 from the processing of salmon and white fish had the highest content of unsaturated fatty acids (786+/−22.6 mg/g). Polyunsaturated fatty acids have been shown to have beneficial effects on normal health and chronic diseases, by, for example, regulation of immune, lipid levels, and cardiovascular functions. Among the monounsaturated fatty acids (MUFAs), C18:1 cis-9 (oleic acid) was present in higher quantities in all the samples analysed (0-231+/−7.5 mg/g). The permeate fraction of the sample collected on 30/01/20 from the processing of salmon and white fish had the highest quantity (231+/−7.5 mg/g) of oleic acid. Oleic acid has been shown to reduce the levels of low-density lipoprotein in blood which in turn reduces the risk of heart disease and stroke. Other monounsaturated fatty acids, such as C16:1, C18:1 trans, C20:1, and C22:1 were also identified in lower quantities in the range of 0-116 mg/g. In the category of PUFAs, which, were for all but one sample, less in quantity than their MUFAs counterparts, C18:2 cis-9 (linoleic acid) was the dominating fatty acids with quantities of up to 234+/−2.7 mg/g. Linoleic acid is an essential fatty acid that plays an important role in the synthesis of eicosanoids, which are involved in a variety of physiological functions. Other important health-related PUFAs such as omega-3 fatty acids C22:6 (DHA) and C20:5 n3 (EPA) were identified with the levels in the ranges of 1.79+/−0.44 to 59.07+/−1.5 and 1.6+/−0.68 to 34.74+/−1.5 mg/g. Highest quantities of both EPA (34.7 mg/g) and DHA (59.1 mg/g), were identified in the whole fraction of the samples collected on the 30/01/20 from the processing of salmon and white fish.
From the saturated fatty acids group, all the analysed fish blood water fractions contained a significant amount of C14:0, C16:0, C18:0 and C22:0 fatty acids with C16:0 (palmitic acid) dominating this group with the quantities ranging from 26.6+/−0.26 to 133.8+/−3.9 mg/g. This observation is in line with other studies showing high amounts of C16:0 in fish oil. Other odd number saturated fatty acids such as C13:0, C15:0, C21:0 and C23:0 were also identified, albeit, in very low quantities. Interestingly, for almost every sample analysed, the permeate fraction had the highest amounts of fatty acids compared to the whole and retentate fractions. This data may suggest that the fatty acids investigated in this study are <3 kDa in size or are mostly associated with the <3 kDa proteins in the blood water. Based on the above observation, ultrafiltration may be used to concentrate and alter the fatty acid profile of fish blood waters.
Techno-Functional Properties of Blood Water Fractions
Water and Oil Holding Capacities
Water holding capacities (WHC) and oil holding capacities (OHC) were determined for all Mackerel and Blue whiting retentate and permeate samples. OHC values (g/g) for sunflower and olive oil are presented in
Emulsifying Capacity and Emulsifying Stability
The emulsifying activity (EA) and emulsifying stability (ES) of 1% (w/v) sample solutions (Mackerel and Blue whiting retentates and permeates) at pH range from 2 to 10 are presented in
Foaming Capacity, Foaming Stability and Solubility
The foaming capacity (FC) and foaming stability (FS) of the 1% (w/v) Mackerel and Blue whiting sample solutions at pH range from 2 to 10 are presented in
Solubility (S) of 1% (w/v) sample solutions at pH ranges between 2 and 10 is presented in
Bioactivity Testing
ACE-I and Renin Inhibition Activity
The results of ACE-I inhibition activity of the Blue whiting and Mackerel samples tested at 1 mg/mL (w/v) concentration, with Captopril used as positive control, is presented in
The activity of Mackerel fractions is significantly different when compared to the tested Blue whiting samples, with Mac 10 KDa and Mac Ret samples having highest inhibition activity (96.9±0.29% and 95.4±0.11%, respectively) and Mac 3 KDa sample with 83.9 (±18.9) % inhibition. The activity of Blue whiting samples was 59.4 (±16.5), 33.1 (±0.59) and 28.9 (±16.4) % for BW Ret, BW 10 KDa and BW 3 KDa samples, respectively.
Renin inhibition activity, tested at 1 mg/mL concentration (w/v) of the samples is presented in
Peptide Identification by Tandem Mass Spectrometry
MS analysis results of the 10 kDa Mackerel and Blue whiting 10 KDa permeate fractions and in Mackerel retentate are presented in Table 6. A total of 65 peptides were identified in the BW 10 KDa sample, 103 peptides were identified in the Mac 10 KDa permeate and 19 peptides in Mac Ret sample. All the identified peptides were identified as novel when checked against the BIOPEP database of known peptides.
oculata OX = 27575 PE = 3 SV = 1
gallus OX = 9031 GN = CKB PE = 1
SV = 1
gallus OX = 9031 GN = CKB PE = 1
gallus OX = 9031 GN = CKB PE = 1
gallus OX = 9031 GN = CKB PE = 1
gallus OX = 9031 GN = CKB PE = 1
gallus OX = 9031 GN = CKB PE = 1
glacialis OX = 185735 GN = hbb1
norvegicus OX = 10116 GN = Ccnd2
musculus OX = 10090
musculus OX = 10090
sapiens OX = 9606 GN = NOL6 PE = 1
taurus OX = 9913 GN = RPS7 PE = 2
musculus OX = 10090
musculus OX = 10090
mississippiensis OX = 8496 PE = 2
sapiens OX = 9606 GN = GLB1 PE = 1
alba OX = 56313 GN = CLOCK PE = 2
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
laevis OX = 8355 GN = gapdh PE = 2
laevis OX = 8355 GN = gapdh PE = 2
laevis OX = 8355 GN = gapdh PE = 2
laevis OX = 8355 GN = gapdh PE = 2
lupus familiaris OX = 9615
lupus familiaris OX = 9615
lupus familiaris OX = 9615
lupus familiaris OX = 9615
musculus OX = 10090
musculus OX = 10090
musculus OX = 10090
albacares OX = 8236 GN = ALDOA
magellanicus OX = 92050
mykiss OX = 8022 PE = 1 SV = 2
mykiss OX = 8022 PE = 1 SV = 2
carpio OX = 7962 GN = ATP5F1B
carpio OX = 7962 GN = ATP5F1B
sapiens OX = 9606 GN = MED1 PE = 1
gallus OX = 9031 GN = ENTPD5 PE = 3
taurus OX = 9913 GN = RPL8 PE = 2
sapiens OX = 9606 GN = PPP4R3C
cuniculus OX = 9986 GN = SELE
salar OX = 8030 PE = 1 SV = 3
sapiens OX = 9606 GN = GDPD5
cupreus OX = 37702 GN = MT-CYB
albacares OX = 8236 GN = ALDOA
asiatica OX = 185453 GN = MT-CYB
porcellus OX = 10141 GN = KCNJ15
1Amino acid nomenclature: A, ala, alanine; C, cys, cysteine; D, asp, aspartic acid; E, glu, glutamic acid; F, phe, phenylalanine; G, gly, glycine; H, his, histidine; I, lle, isoleucine; K, lys, lysine; L, leu, leucine; M, met, methionine; N, asn, asparagine; P, pro, proline; Q, gln, glutamine; R, arg, arginine; S, ser, serine; T, thr, threonine; V, val, valine; W, trp, tryptophan; Y, tyr; tyrosine; X, undetermined amino acid.
2Hit number of the assigned sequence using MASCOT search engine
3Accession numbers of protein of origin according to NCBI non-redundant database
Table 6: Identified Peptides in Mackerel and Blue Whiting 10 KDa Permeate Fractions and in Mackerel Retentate
Materials and Methods
Raw Material
Blue whiting by-products were kindly supplied by Bard Iascaigh Mhara (BIM) in the form of 4 kg frozen blocks. The blocks consisted of the skin, meat and bones of Blue Whiting caught in Irish waters in March 2017. 500 g was used for experiments. The material was thawed at room temperature and then cut into 1 cm pieces prior to use.
Skin and Bone Pre-Treatments
Four different pre-treatments were applied to blue-whiting by-products independently. Gelatine extraction and gelatine and gelatine hydrolysate freeze-drying steps remained the same throughout the study. The four standard operating procedures (SOPs) for pre-treatment are presented in Table 7.
Following the pre-treatment steps, by-product skin and bone material was washed with water until neutral (pH 6-7) and gelatine was extracted overnight using water (3:1 v/w to material) at 45° C. in a MaxQ 8000 laboratory shaker (Thermo Fisher Scientific, MA USA) at 200 rpm speed. Solids were removed by filtration through Whatman No 4 filter paper using a Büchi funnel. Resultant clear gelatine extracts were subsequently freeze-dried (FD80GP, Cuddon Freeze Dry, New Zealand) using the following program: Initial temperature −20° C.; 5 steps; run time 90 h; end temperature 0° C. Dried material was placed in sterile, sealed 250 ml containers and stored at −80° C. until analyses.
Characterisation of the Physical and Chemical Properties of Extracted Gelatines
Proximate Analysis
The yield of gelatine extracted was calculated after freeze-drying and was expressed as a percentage of the total by-product raw material used. The total protein content of the gelatine samples was determined using the Dumas combustion method using a LECO FP328 Protein analyser (LECO Corp, MI USA), according to the Association of Official Analytical Chemists (AOAC) method 992.15 (14). A conversion factor of 6.25 was used to convert total nitrogen to protein.
The ash content of the 4 different gelatine extracts was determined gravimetrically, as previously described (15).
Water Activity
Water activity (aw) values for all samples were determined using an AquaLab Lite meter (Decagon Devices Inc., Germany). Approximately 0.25 g of finely milled sample was placed in the water activity meter and aw and the temperature was recorded (16).
PH Value
pH values of 1% gelatine solutions (w/v) were determined at room temperature using a pH213 pH-meter (Hanna Instruments, TX USA), and buffers pH 4 and pH 7 (Sigma Aldrich, Ireland) were used for calibration in accordance with the method described by GME (17).
Lowest Gelling Concentration
The lowest gelling concentrations (LGC) of the Blue-whiting derived gelatines were determined using the method of Ogunwolu et al. (18), and results were expressed as the concentration (w/v) of gelatine solution which could form a gel at 4° C. Briefly, 2 ml of a range of concentrations of each gelatine solution (1, 2, 5, 8 and 10%; w/v) was measured in a 15 ml Falcon tube and placed in the laboratory refrigerator set to 4° C. for 2 hours. The concentration at which the solution would stop flowing in the tube was recorded as the LGC.
Colour Measurement
Colour measurements were carried out using a Minolta Lab colorimeter (CR-400/410, Konica, Minolta, Ireland) in accordance with previously described methods (19). White and black standard tiles were used to calibrate the instrument prior to measurements. Readings were reported in the CIE L*, a*, and b* system, as L* (lightness), a* (redness/greenness), and b* (yellowness/blueness). The chroma (C*) values were calculated using the following equation (20):
C*=√{square root over (a2×b2)}
Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE)
Extracted gelatine samples were prepared for sodium dodecyl sulphate polyacrylamide electrophoresis (SDS-PAGE) analysis according to a previously described method (7). SDS-PAGE was carried out using the discontinuous Tris-tricine buffer system (Sigma Aldrich, Ireland). Briefly, gelatine extracts (1%, w/v) were diluted with sample buffer containing 0.2 M Tris-HCl, pH 6.8 containing 2% (w/v) SDS, 40% (v/v) glycerol, 0.04% (w/v) Coomasie Blue G250 and 2% (v/v) 2-mercaptoethanol at the ratio of 1:1 (v/v) and heated to 95° C. for 5 min. The gels used for electrophoresis were the Bio-Rad Mini-Protean Tris-tricine precast gels (4-20%). Gelatine samples were run in a Mini-Protean® Tetra Cell (Bio-Rad Laboratories, Watford, United Kingdom) at a constant voltage of 100 V. Gels were then fixated in 40% methanol, 10% acetic acid (v/v, in water) and stained with Biosafe Coomassie G250 Stain.
The load volume was 20 μL in all lines. A Bio-Rad Precision Plus Protein™ unstained protein molecular weight standard (Bio-Rad Laboratories, Watford, United Kingdom), MW range (10-250 KDa) and a LW range standard (4-250 kDa) was used to identify the protein fractions. Band detection and molecular weight calculation was done using GelAnalyzer 2010a software (http://www.gelanalyzer.com).
Determination of Techno-Functional Properties
Water and Oil Holding Capacities
The water holding capacity (WHC) and oil holding capacity (OHC) of extracted gelatines were measured using the modified methods described by Neto et al. (21). In brief, 100 mg of each gelatine sample was mixed with 1 ml of distilled water or oil (olive and sunflower oil) using a vortex mixer (VV3, VWR International Ltd., Ireland) for 30 seconds. The suspension was then centrifuged at 2200×g for 30 min (Eppendorf MiniSpin, Eppendorf UK Limited, United Kingdom) at 19° C. The supernatant was then decanted by draining the tubes at 45° angle for 10 min (20 min for oil). Water/oil holding capacity was calculated by dividing the weight of water/oil absorbed by the weight of the protein sample and expressed as grams of water or sunflower oil held by 1 g of protein.
Solubility
Solubility in water (S) was determined using the modified method of Ogunwolu et al. (18). 100 mg of each gelatine sample was dispersed in 10 ml de-ionised water. Using a pH-meter (Mettler Toledo, Barcelona, Spain), the pH of the dispersions was adjusted to 2, 4, 6, 8 and 10 with 0.1 N HCl and 0.1 N NaOH. The mixture was vortexed at room temperature (19-20° C.) for 5 min, and subsequently centrifuged at 7500×g for 15 min (Lynx 6000, Thermo Fisher Scientific, MA USA). The protein content in the supernatant was determined using the Pierce™ BCA (bicinchoninic acid) Protein Assay Kit (Thermo Fischer Scientific, MA USA). Gelatine solubility at different pH conditions was then calculated using the following equation:
S (%)=(protein content in the supernatant/protein content in full dispersion)×100.
Foaming Capacity
The foaming capacity (FC) of the gelatine samples was determined by the modified method described by Bencini (22). Gelatine was suspended in deionized water to make 1% concentration (w/v) and the pH was adjusted to 2, 4, 6, 8 and 10 with 0.1 N HCl and 0.1 N NaOH. The suspensions were homogenized using a T 25 digital ULTRA-TURRAX® homogenizer (IKA®, Germany) (10,000 rpm; 1 min) and the volume of produced foam was measured in a graduated 50 ml Falcon tube. FC was calculated as the volume of foam using the formula:
FC (%)=(Vf−V0)/V0×100
where; V0 is the initial volume of protein solution before homogenization and Vf is the volume of foam produced after homogenization. The foaming stability (FS) was calculated using the same formula, with Vf measured after 15, 30 and 60 min.
Emulsifying Activity and Emulsifying Stability
The emulsifying activity (EA) of the protein extracts was determined using a modified method of Garcia-Vaquero et al. (20). Gelatine was suspended in deionized water to make 1% concentration (w/v) and the pH was adjusted to 2, 4, 6, 8 and 10 with 0.1 N HCl and 0.1 N NaOH. The solution was homogenized for 30 s at 14,000 rpm using a T 25 digital ULTRA-TURRAX® homogenizer (IKA®, Germany). The emulsion was created by addition of sunflower oil to aqueous phase (oil:gelatine solution=3:2) in 50 ml Falcon tubes. The oil was added in two steps: half of the volume was first added, and the mixture was homogenized 30 s at 14000 rpm, after which the rest of the oil was added and homogenization was repeated for 90 s at the same speed. The tubes containing emulsion were then centrifuged at 1100×g for 5 min and the volume of the emulsion layer was recorded. Emulsifying activity was calculated by the formula:
EA (%)=(Ve/Vt)×100
Where; Ve was the volume of the emulsion layer after centrifuging and Vt was the complete volume inside the tube. Emulsion stability (ES) was determined by heating the previously prepared emulsions at 85° C. for 15 min, cooling at room temperature for 10 min and centrifuging again 1100×g for 5 min. The ES was calculated and expressed as the % of EA after heating and centrifuging by the formula:
ES (%)=(Vemulsion after heating/Voriginal emulsion)×100
Microsoft Excel was used for all calculations and graph construction in this study, except in the case of SDS-Page gel analysis, where the GelAnalyzer 2010a software was used for molecular weight estimation. Purified gelatine of bovine (BOV) and porcine (POR) origin (Sigma Aldrich, Ireland) were used for comparison of properties.
Enzyme Hydrolysis
Based on the previously determined chemical, physical and functional properties, gelatine extracts generated using SOP1 and SOP2 were selected for further hydrolysis using the commercial enzymes alcalase and papain. The hydrolysis procedures were undertaken as follows, using a modified procedure described by Lafarga and Hayes (23):
Gelatine samples (2.5 g) were dissolved in deionized water (250 ml) to obtain 1% (w/v) gelatine solutions, which were hydrolysed independently with either Alcalase® (EC number 3.4.21.62, activity ≥5 U/g, Sigma Aldrich, Ireland) and papain (EC number 3.4.22.2, activity ≥3 U/mg, Sigma Aldrich, Ireland). The pH values and temperature of each gelatine solution was set before addition of the enzymes as follows: 60° C. and pH 9.5 for Alcalase, 65° C. and pH 6.5 for papain. Solutions were kept in an incubated laboratory shaker (at optimum temperatures, as specified above) during hydrolysis and agitated at 200 rpm. The alcalase was added in a substrate-to enzyme ratio of 100:1 (w/w) and papain was added in 10:1 (w/w) ratio. After incubation, the solutions were heated at 95° C. for 10 min in a water bath to deactivate the enzymes. The pH of solutions was maintained at the optimum value for each enzyme using 0.1 M or 1 M NaOH. After incubation, the degree of hydrolysis (DH) was calculated using the pH-stat method (24), after 1, 60, 120 and 240 min. The OH was then calculated using the following equation:
DH=B×NB×1/α×1/Mp×1/htot×100%,
where B (mL) is the volume of NaOH consumed, NB is the normality of the NaOH used, 1/a is the average degree of dissociation of the α-amino groups related with the pK of the amino groups at particular pH and temperatures, MP (g) is the amount of protein in the reaction mixture, and htot (meq/g) is the sum of the millimoles of individual amino acids per gram of protein associated with the source of protein used in the experiment. Values for htot and 1/a were obtained from the study conducted by Adler-Nissen (24). Gelatine hydrolysates were freeze-dried as previously described and dried product was kept in sealed containers at −80° C. until further use.
Molecular Weight Cut Off Filtration
Gelatine hydrolysates (0.5 g) were diluted independently in deionized water (10 ml) to a concentration of 5% (w/v). The solutions (10 ml) were then filtered through 3 kDa membrane filters using the Amicon Ultra-15 Centrifugal Filter Unit (Sigma Aldrich, Ireland) at 4000 g for 60 min to obtain fractions with peptides less than 3 kDa in size. Filtrates and permeates were then freeze-dried and the yield of each peptide fraction (s 3 KDa) was calculated after weighing.
ACE-I Inhibition Assay
ACE-I inhibition activity of gelatine hydrolysates and 3 kDa fractions was determined using a bioassay kit in accordance with the manufacturer's instructions (ACE Kit—WST, Dojindo Laboratories, Kumamoto, Japan). In brief, 20 μL of each peptide aqueous solution at a concentration of 1 mg/mL was added to 20 μL substrate and 20 μL enzyme working solution in triplicate. Captopril was used as a positive control (0.5 mg/mL). Samples were incubated at 37° C. for 1 h. A 200 μL of indicator working solution was then added to each well, and subsequent incubation at room temperature was carried out for 10 min. Absorbance at 450 nm was read using a FLUOstarOmega microplate reader (BMG LABTECH GmbH, Offenburg, Germany). The percentage of inhibition was calculated using the following equation:
% ACE-I inhibition=100% Initial activity−Inhibitor×100/100% Initial activity
Amino Acid Composition
The total amino acid content of selected gelatine hydrolysates was determined using the method described by Hill (25). Samples were hydrolysed in 6 M HCl at 110° C. for 23 h. The hydrolysed solutions were diluted with 0.2 M sodium citrate buffer (pH 2.2) to give approximately 250 nmol of each amino acid residue. The sample was then diluted 1:1 with the internal standard, norleucine, to give a final concentration of 125 nmol/mL. Amino acids were quantified using a Jeol JLC-500/V amino acid analyser (Jeol Ltd., Garden city, Herts, UK) fitted with a Jeol Na+ high-performance cation exchange column.
MS Analysis
Gelatine papain hydrolysates generated from gelatines isolated with SOP1 and SOP2 were selected for MS analysis based on results from techno-functional and bioactivity assays. Samples were cleaned prior to MS analysis using the TiO2 clean-up kit (Pierce, USA). Samples were re-suspended in 50 uL of 0.1% TFA in 2% ACN. 5 μl of every sample was loaded onto a trap column (NanoLC Column, 3μ C18-CL, 350 mm×0.5 mm; Eksigent) and desalted with 0.1% TFA at 3 μl/min during 5 min.
The peptides were then loaded onto an analytical column (LC Column, 3μ C18-CL, 75 um×12 cm, Nikkyo) equilibrated in 5% acetonitrile 0.1% FA (formic acid). Elution was carried out with a linear gradient of 5 to 35% B in A for 45 min. (A: 0.1% FA; B: ACN, 0.1% FA) at a flow rate of 300 nl/min. Peptides were analysed in a mass spectrometer nanoESI qQTOF (5600 TripleTOF, ABSCIEX). Sample was ionized applying 2.8 kV to the spray emitter. Analysis was carried out in a data-dependent mode. Survey MS1 scans were acquired from 350-1250 m/z for 250 ms. The quadrupole resolution was set to ‘UNIT’ for MS2 experiments, which were acquired 100-1500 m/z for 50 ms in ‘high sensitivity’ mode. Following switch criteria were used: charge: 1+ to 5+; minimum intensity; 70 counts per second (cps). Up to 25 ions were selected for fragmentation after each survey scan. Dynamic exclusion was set to 15 s.
Data Analysis Procedure
ProteinPilot (version 5.0) software from Sciex was used in the data analysis. ProteinPilot default parameters were used to generate peak list directly from 5600 TripleTof wiff files. The Paragon algorithm (26) of ProteinPilot v 5.0 was used to search the NCBI_collagen (162534 searched proteins) database with the following parameters: no enzyme specificity, no taxonomy restriction, and the search effort set to through. The protein grouping was done by Pro group algorithm.
Results
Proximate Analysis
The choice of pre-treatment procedure had a significant impact on the yield and proximate composition of the extracted gelatines, as can be seen in Table 8. The yield of dry gelatine recovered was 4.55±0.53% for SOP1, 4.73±0.41% for SOP2, 2.22±0.51% in the case of SOP3, while SOP4 resulted in a yield of 5.02±0.89% gelatine. Although yields are low relative to previous work [(27), (3), (28)], reports on gelatine extraction yields vary greatly throughout available literature [(29), (27), (30), (31)]. The crude protein content of the samples was 86.4±2.49% for SOP1, 85.6±2.41 in SOP2, 67.6±0.93 in SOP3 and 67.4±5.03% in SOP4 gelatine sample, while it was 91.7±0.27% and 94.8±0.29% in the case of control bovine and porcine gelatines, respectively. The SOP1 and SOP2 samples had similar ash content (5.06±0.15 and 5.95±0.19%, respectively), while SOP3 sample had an unusually high (23.3±2.86%) content of ash, and SOP4 sample contained 11.6±0.09% ash. These determined values were significantly higher than in bovine and porcine control samples, which both contained less than 1% ash (0.68±0.12 and 0.24±0.10%, respectively).
1LGC—lowest gelling concentration;
2Aw—water activity
3BOV—bovine gelatine;
4POR—orcine gelatine
Water Activity, pH Value and LGC
The pH values of 1% (v/w) aqueous gelatine solutions are shown in Table 8. The values for SOP1 and SOP2 samples (pH 7.05±0.02 and pH 6.59±0.02, respectively) were similar to the pH values of the porcine control sample (7.57±0.01); while pH of SOP3 and SOP4 gelatines (4.61±0.02 and 5.03±0.02, respectively) was closer to value determined for bovine gelatine (5.77±0.01). The aw values of the examined samples were 0.26±0.01, 0.44±0.00, 0.52±0.01 and 0.39±0.01 for SOP1, SOP2, SOP3 and SOP4 extracted gelatines after drying, respectively. Bovine and porcine gelatines had comparable water activity (0.42±0.01 and 0.36±0.01, respectively). The lowest gelling concentration (LGC) values of the samples (Table 8) show that SOP1, SOP2 and SOP4 solutions were able to form gels at 4° C. at 2% concentration (w/v), while SOP3 gelatine did not show gelling up until 8% concentration. Both control mammalian gelatines formed gels at 1% concentrations.
Colour Measurement
The colour parameters of the examined gelatines are presented in Table 9. It can be seen that values of L (lightness) was 95.3±0.73 in the case of SOP1 gelatine, 95.3±0.73 for SOP2, 82.7±3.14 for SOP3 and 9.4±1.93 for SOP4 sample. The b parameter (yellowness/blueness) showed a wide range of determined values, between 2.58±0.85 and 29.5±5.69 (SOP4 and SOP3 samples, respectively); similarly to calculated C value (chroma) of the samples, which was in the range between 2.62 (SOP4) and 29.62 (SOP3). The a parameter (greenness/redness) of all measured samples had negative value, indicating a slight colour shift toward greenness.
1BOV—bovine gelatine;
2POR—porcine gelatine
Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SOS-PAGE)
The distribution of molecular weights (MV) in the gelatine samples is presented in
Water and Oil Holding Capacity
The water holding (WHC) and oil holding capacity (OHC) of the fish gelatine samples are presented in
Solubility, Foaming Capacity and Foaming Stability
Solubility (S) of 1% (w/v) gelatine solutions at pH ranges between 2 and 10 is presented in
The foaming capacity (FC) and foaming stability (FS) of the 1% (w/v) gelatine sample solutions at different pH values (2, 4, 6, 8 and 10) are presented in
Emulsifying Activity and Emulsifying Stability
The emulsifying activity (EA) and emulsifying stability (ES) of 1% (w/v) fish gelatine solutions at pH range from 2 to 10 are presented in
Enzyme Hydrolysis
The degree of hydrolysis (DH) of SOP1 and SOP2 gelatine sample solutions is presented in
After molecular weight cut-off (MWCO), using 3 kDa membranes the SOP1 and SOP2 papain hydrolysates had yields of 42.1±0.54% and 43.2±1.67%, respectively, while the alcalase hydrolysates of gelatines from SOP1 and SOP2 yielded 3 kDa hydrolysate fractions of 10.9±0.89% and 9.3±0.61% respectively.
Amino Acid Composition
The total amino acid composition of SOP1 and SOP2 gelatine samples and their papain hydrolysates are presented in Table 10. The main amino acids detected included glycine (190.4 to 210.6 g/Kg), glutamic acid (78.7 to 84.6 g/Kg), alanine (72.7 to 80.5 g/Kg) and proline (76.6 to 86.7 g/Kg). The sum of the total amino acids ranged from 749.9 g/Kg (SOP2 papain hydrolysate) to 800.9 g/Kg (SOP1 papain hydrolysate), which accounted for 74.9% and 80.1% of the total sample weights, respectively.
The results of ACE-1 inhibition assay are presented in
MS Analysis
MS analysis of the 3 kDa fractions generated from gelatines isolated using SOP1 and SOP2 and hydrolysed with papain are presented in Table 11. A total of 81 peptides were identified in the papain gelatine hydrolysate made using gelatine isolated with SOP1, while 90 peptides were identified in the hydrolysate generated using papain and gelatine isolated with SOP2. All the identified peptides were identified as novel when checked against the BIOPEP database of known peptides.
partitus]
partitus]
partitus]
erythrolophus]
erythrolophus]
erythrolophus]
kowalevskii]
kowalevskii]
floridanum]
floridanum]
belcheri]
belcheri]
mansoni]
mansoni]
azteca]
marmoratus]
sabaeus]
fortis]
kowalevskii]
deceptionensis]
familiaris]
furzeri]
erythrolophus]
erythrolophus]
belcheri]
belcheri]
calcarifer]
porosus]
grahami]
fortis]
corporis]
laevis]
milii]
domesticus]
domesticus]
cellulosum]
1Amino acid nomenclature: A, ala, alanine; C, cys, cysteine; D, asp, aspartic acid; E, glu, glutamic acid; F, phe, phenylalanine; G, gly, glycine; H, his, histidine; I, Ile, isoleucine; K, lys, lysine; L, leu, leucine; M, met, methionine; N, asn, asparagine; P, pro, proline; Q, gln, glutamine; R, arg, arginine; S, ser, serine; T, thr, threonine; V, val, valine; W, trp, tryptophan; Y, tyr; tyrosine; X, undetermined amino acid.
2Accession numbers of protein of origin according to NCBI non-redundant database
3Percentage of confidence of the assigned sequence using MASCOT search engine
Yields and Proximate Composition of Gelatines
It is known that numerous factors, including fish species, quality of by-products, the pre-treatment steps and the extraction time and temperature can influence the yield of gelatine produced. In this study, the by-product consisted of a mixture of fish skin, bones and muscle left after industrial processing of blue whiting into surimi products. As can be seen from Table 8, gelatines extracted using SOP1, SOP2 and SOP4 procedures produced similar yields of gelatine (around 5%), while the yield of gelatine obtained using SOP3 was significantly lower. SOP1 and SOP2 gelatine samples also had high protein and low ash contents compared to gelatines generated using SOP3 and SOP4. Notably, the LGC of SOP1, SOP2 and SOP4 gelatines was approximately 2% (w/v), while gelatine generated using SOP3 had gelling properties only at significantly higher (8%, w/v) concentrations. Solutions of SOP1 and SOP2 gelatines had pH values closer to neutral, while gelatines generated using SOP3 and SOP4 had pH values in the range of X-X. The water activities of the samples after freeze-drying were comparable to the aw of bovine and porcine gelatines. This indicates that the gelatines are safe for use. Most pathogenic bacteria require aw value of above 0.91, and a product can be considered microbiologically stable if its Aw is under 0.6 (32). A decrease in L (lightness) parameter indicates a general darker colour, and it can be seen that SOP1, SOP2 and SOP4 samples compare favourably to the control gelatines (Table 9). The notable exception is the enzymatically pre-treated SOP3 gelatine, which shows the lowest L value of all samples, as well as highest value of b (yellowness/blueness) parameter corresponding to its strong yellow coloration. C (Chroma) value is a tool for expressing the colour intensity, and from the calculated C values it can be clearly seen that SOP3 gelatine had the most intense colouring. The SDS-PAGE (
Previously, Jellouli et al. (33) reported a yield of 5.67% gelatine from fish skins of the grey triggerfish (Balistes capriscus) when pre-treatment with 0.2 mol/L of NaOH and 0.05 mol/L of acetic acid was used, while others including Balti et al. (34), reported a lower gelatine yield (2.21%) when protease enzyme was used as a pre-treatment in the case of cuttlefish (Sepia officinalis) skin gelatine. According to the Gelatine Handbook (35) specifications, edible gelatine should normally contain between 0.3-2% ash, depending on the production process, and ash content of the samples in this study was higher than these limits. It is known that the colour of fish sourced gelatine may vary widely, depending on the fish species, raw material, pre-treatment and extraction process, although it generally does not affect its functional properties. Recently, Kittiphattanabawon et al. (30) have investigated the influence of extraction conditions on the properties of gelatine obtained from Clown featherback (Chitala ornata). Their results showed a decrease in MW bands (γ-, β- and α1-chains) intensity with the increase of extraction time and temperature. In our study, the extraction temperature and time were kept constant in all SOPs, so it can be concluded that pre-treatment conditions also show a pronounced effect on the protein distribution in extracted fish gelatines. Limitations concerning the applications of fish gelatine are mainly due to lower gel strengths and stability and lower gelling and melting temperatures in comparison to mammalian-sourced gelatines (1). These differences are especially prominent in the case of gelatines extracted from cold-water fish species, which are known to contain smaller number of imino acids (proline and hydroxyproline) and a larger quantity of higher non-polar amino acids (36). The properties of gelatines produced during our experiments are in accordance with literature reports comparing cold-water fish gelatines to warm-water species and mammalian sources [(1), (37)]. Therefore, non-modified gelatines obtained from cold-water fish species, such as blue whiting, may not be successfully used in applications where gelling at room temperature is required (e.g. production of jelly desserts).
Techno-Functional Properties of Gelatines
WHC refers to the ability of protein to absorb water and retain it against a gravitational force within the protein matrix (38). The WHC values of the SOP1, SOP2, SOP3 and SOP4 gelatines (
SOP1 gelatine had the highest OHC values for both sunflower and olive oil. SOP2 and SOP4 samples had comparable OHC, while SOP3 sample had the lowest values for both OHC and WHC of all the produced samples. Fat binding capacity depends on the degree of exposure of the hydrophobic residues inside gelatine, and therefore gelatines obtained from cold water fish species, richer in hydrophobic amino acid residues, may show a better OHC and lower WHC compared to mammalian gelatines.
Results in this study show significant differences in WHC and OHC values, implying that the products obtained from blue whiting belong to the cold water fish gelatine type, and could be potentially be utilized as food emulsifiers. The solubility of all gelatine samples (
The FC (
On the basis of the results obtained in this study, it can be concluded that pre-treatment has a considerable influence on the properties of gelatine extracted from Blue whiting by-product consisting of skin, bones and meat. The combination of alkaline, diluted mineral acid and diluted acetic acid pre-treatment in the case of SOP1 and SOP2 samples has proven to yield gelatine with best physical and chemical properties and most optimal techno-functional characteristics. Using mild organic acid (citric acid) for the tested period of time has produced a highest yield of gelatine with best colour characteristics, albeit with high mineral content and less optimal techno-functional characteristics. In the case of SOP3 pre-treatment, which consisted of enzymatic hydrolysis (using alcalase) and subsequent treatment with mineral acid, the gelatine produced had notably inferior physical and chemical characteristics, lower yield and significantly impaired techno-functional properties. This indicates an excessive level of collagen hydrolysis if alcalase is used, which was further substantiated by the results of SDS-PAGE protein analysis.
Enzyme Hydrolysis
Enzymatic hydrolysis of food by-products is an interesting strategy for by-product utilisation. The interest of numerous researchers is particularly focused on hydrolysis of marine processing by-products, since it has been shown that many of the hydrolysis products possess various biological activities, such as antioxidant, antihypertensive, antibacterial and anti-obesity effects. Based on the overall properties of the gelatines developed in this study, gelatines generated using SOP1 and SOP2 were chosen for further hydrolysis using alcalase, and papain enzymes. Determination of the degree of hydrolysis (DH) is an important step in characterization of protein hydrolysates for use in functional food products. Also, it is known that DH has an important role in ACE-I inhibitory activity, with higher DH values principally indicating better potential bioactivity.
Although optimal conditions for the enzymatic hydrolysis were applied, the attained degree of hydrolysis differed significantly between the samples. Hydrolysis of gelatine using resulted in a DH values of 20 The DH of gelatine using alcalase was 2.54±0.12% for SOP2 derived gelatine.
Bioactivity of Papain Hydrolysates
The in vitro ACE-I inhibitory activities of the alcalase and papain hydrolysates were calculated at a concentration of 1 mg/ml and Captopril® (0.5 mg/ml) was used as positive control. The increase in bioactivity of the low molecular weight fraction is in agreement with previously reported findings implying that lower molecular weight peptides are principally responsible for ACE-I inhibition in protein hydrolysates. When alcalase was used for hydrolysis of gelatines, the differences between the ACE-I inhibitory activity of whole hydrolysates and ≤3 KDa peptide fractions were significant. This was however not the case when papain was used for hydrolysis, where whole hydrolysates had activity comparable to the purified ≤3 KDa peptide fractions. This can be explained by more complete protein hydrolysis when papain was used, which is shown by higher calculated DH values.
MS Analysis of Peptides
The ≤3 KDa peptide fractions of the papain hydrolysates were determined to have the highest ACE-I inhibitory activity and were therefore selected for MS analysis in order to determine their peptide composition. All of the determined peptides (81 in SOP1 sample and 90 in SOP2 sample) were found to be unique when compared to peptides in the BIOPEP peptide database. The amino acid composition of the hydrolysates was similar to the intact gelatine samples, and the results show that most abundant amino acids within peptide sequences were glycine (190.4 to 210.6 g/Kg), glutamic acid (78.7 to 84.6 g/Kg), alanine (72.7 to 80.5 g/Kg) and proline (76.6 to 86.7 g/Kg). It has been suggested that residues with bulky hydrophobic side-chains (proline, tryptophan, tyrosine and phenylalanine) are the most effective amino acids for inhibition of ACE-I in dipeptides, but also the N-terminal side of peptide inhibitors may benefit from small, as well as hydrophobic side chains such as leucine, valine and isoleucine (45). The peptides that were identified with ≥99.0% analytical confidence (37 in SOP1 and 39 in SOP2 sample) were checked against FASTA sequences of the corresponding proteins used for confirmation in the NCBI protein database. The structure of most identified peptides (36 in SOP1 sample and 37 in SOP2 sample) was confirmed in this manner, and the corresponding proteins show a strong correlation between amino acid sequence of identified peptides and alpha-chain collagen sequences.
The identified peptides were then searched for the potential bioactive fragments using the BIOPEP (46) analysis tools. The search resulted in numerous identified fragments with ACE-I inhibitory activity, such tripeptides GPL, PGL, GPM, DGL and dipeptides PP, PG, GG, AG, and IG in the tested peptide sequences.
Test Sample 1
Substitute 10 g of flour with 10 g 3 kDa fraction
Test Sample 2
Substitute 10 g of flour with 10 g 10 kDa fraction
Test Sample 3
Substitute 10 g of flour with 10 g retentate fraction
Methodology
Mix and homogenize ingredients, add water and oil and knead to obtain soft dough. The dough was rested for 15 to 20 minutes, rolled on a plate to approximately 0.5 cm thickness and cut. The biscuits were baked at 140° C. for 45 minutes in a convection oven.
Results
The colour of the biscuit was tested:
For the gelatine hydrolysate—
It can be seen that values of L (lightness) parameter ranged from 82.7 (±3.14) for SOP3 sample to 95.3 (±0.73) in the case of SOP1 sample. The b parameter (yellowness/blueness) showed a wide range of determined values, between 2.58 (±0.85) and 29.5 (±5.69) (SOP4 and SOP3 samples, respectively); similarly to calculated C value (chroma) of the samples, which was in the range between 2.62 (SOP4) and 29.62 (SOP3). A parameter (greenness/redness) of all measured samples had negative value, indicating a slight colour shift toward greenness.
Anti-Hypertensive Effect in Dogs In Vivo.
The gelatine samples were generated from the raw material using SOP2. 250 g (×3) of whole, blue-whiting H&G material was minced in a food blender for 30 seconds and subsequently added to 250 ml of distilled, deionised water. The slurry obtained was heated for 10 min at 80° C. to inactivate endogeneous enzymes. Hydrolysis was carried out at 140 rpm, 55° C., pH 8 using the enzyme Alcalase® which was added to the H&G material at the ratio of 1:100 (w:v). Hydrolysis was carried out for 4 hours. The volume of 0.1 M NaOH used to adjust the pH of the hydrolysate to 6.5 was noted and hydrolysis was terminated by heating at 95° C. for 10 min to inactivate the added enzyme. The hydrolysate was cooled to room temperature, the hydrolysate slurry was poured into trays, frozen and then freeze-dried using a Labconco freeze drier (Labconco corporation, USA) and a set programme for 48 h. The freeze-dried hydrolysates were weighed to calculate yield by-product H&G per batch and hydrolysates were subsequently analysed for protein, lipid and other components.
Formulation and baking conditions for PAW dog biscuits containing H& G whole alcalase hydrolysate or H&G gelatine papain hydrolyate or mussel whole papain hydrolyate at a concentration of 10%.
Control Recipe (for 600 g of Dough)
Experiment Recipe (for 600 g of Dough, Around 10% Added Protein):
Baking Procedure:
Mix ingredients; knead for 3-5 minutes. Roll the dough using automatic sheeter (to approx 3.5 mm thickness) and cut out biscuits using cutter. Put on non-stick baking tray and bake in pre-heated oven at 150° C. for 40 min. Water loss factor: approximately =0.76
Cookies without test ingredient marked as “Control” and cookies with test ingredients named M Cookies (Mussel papain hydrolysate cookies) and H&G cookies (Blue whiting H&G hydrolysate cookies) were used in in vivo dog studies.
The study was performed at an approved pet kennel in the Netherland (Kennel De Morgenstond). All tests carried out were non-invasive and did not harm the animals or the wellbeing of the animal. The study was executed with ten senior dogs (8-13 years old) over three weeks (21 days). A “matched pair design” format was used in this study. Experimental protocols with the animals is attached in Appendix A. 1 (2+5, where 2 days adjustment on new feed/snack, 5 days recording period). For the first week, dogs are fed with the control cookies. After the first 7 days, dogs were then on a break for 2 days and were then in the new test for 5 days. During the course of the whole study, dogs were given 500 g of Pedigree kibbles (The proximate analysis of the kibble feed is shown in table 4.1). During the control period, in addition to food, each dog was offered 2 control biscuits per day. The same procedure was repeated for the test diets.
Results
Measurement of blood pressure of the dogs showed a significant decrease in BP when the H&G (headed and gutted) gelatine hydrolysate cookie was given to dogs compared to the control (
| Number | Date | Country | Kind |
|---|---|---|---|
| 20204217.2 | Oct 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/079822 | 10/27/2021 | WO |
