Patent Application
20230338298
The present invention relates to plant-based microcapsules for the efficient encapsulation and retention of water-soluble ingredients, as well as the efficient co-encapsulation of water-soluble and water-insoluble ingredients. The present invention also relates to compositions comprising the microcapsules, a method of making the microcapsules and compositions, and to uses of the microcapsules and compositions.
The development of biocompatible materials has attracted much interest in recent years. The demand for biocompatible materials with functional characteristics is particularly significant in applications where such materials come into contact with the human body, including in cosmetics, food and pharmaceuticals. However, the stability and functionality of a wide range of active compounds is limited in the bulk solution, where degradation and loss of function occur rapidly. In this context, the main advantages of encapsulation are in protecting sensitive or unstable compounds from degradation under adverse conditions, such as exposure to chemicals, air and light, and to allow control of the bio-accessibility and bioavailability of the encapsulated compounds. While several encapsulation techniques are currently available, these commonly rely on the use of synthetic polymers, which may not be suitable as carriers in pharmaceutical and food applications or may have limited permitted exposure levels in cosmetic applications. Furthermore, synthetic polymer shell materials can lead to the formation of microplastics, which are detrimental to the environment.
Alternatively, naturally-derived polymers such as chitosan or gelatine can be used in encapsulation techniques but the stability of such naturally-derived shell materials can be severely affected by processing conditions normally present during final product manufacturing processes (such as exposure to high temperatures and high shear conditions) or by the food or pharmaceutical product composition (pH, presence of chelating agents, cross-interaction with other ingredients etc.). To overcome this, covalent cross-linking strategies are often employed, which may lead to the presence of harmful unreacted cross-linking agents in the final product. Additionally, the use of animal-derived polymers such as chitosan or gelatine means the final product would not be suitable for vegetarian/vegans.
Furthermore, whilst the encapsulation of oils, or oil-soluble ingredients can be achieved using standard encapsulation approaches, the inherent shell permeability of microcapsules prepared from naturally-derived polymers does not allow for the efficient encapsulation of small water-soluble compounds and their retention within the microcapsules, particularly in an aqueous environment. It thus remains a challenge to generate a microencapsulation system from a naturally-derived polymer that can efficiently encapsulate small water-soluble ingredients, as well as withstand standard industrial manufacturing processing conditions without compromising the capsule stability.
Viewed from a first aspect, the present invention provides a microcapsule comprising:
Viewed from a further aspect, the present invention provides a composition comprising at least one microcapsule as hereinbefore described and an external phase.
Viewed from a further aspect, the present invention provides a method for preparing a microcapsule as hereinbefore described, comprising:
Viewed from a further aspect, the present invention provides a microcapsule prepared according to the method as hereinbefore described.
Viewed from a further aspect, the present invention provides a method for preparing a composition as hereinbefore described, comprising:
Viewed from a further aspect, the present invention provides a composition prepared according to the method as hereinbefore described.
Viewed from a further aspect, the present invention provides a food, beverage, cosmetic, home care product, personal care product, pharmaceutical, medical device, biomaterial, or agrochemical incorporating a microcapsule or a composition as hereinbefore described.
Viewed from a further aspect, the present invention provides the use of a microcapsule as hereinbefore described or a composition as hereinbefore described to produce a food, beverage, cosmetic, home care product, personal care product, pharmaceutical, medical device, biomaterial, or agrochemical.
As used herein, the term “water soluble” refers to a substance having a solubility in water, measured at ambient temperature (e.g. 25° C.±2° C.) and at ambient pressure (e.g. 1013 mbar), at least equal to 1 gram/litre (g/L).
As used herein, the term “hydrophilic phase” refers to a phase in which a water-soluble ingredient is capable of dissolving.
As used herein, the term “oil soluble” refers to a substance having a solubility in in oil or organic solvent, measured at ambient temperature (e.g. 25° C.±2° C.) and at ambient pressure (e.g. 1013 mbar) at least equal to 1 gram/litre (g/L).
As used herein, the term “lipophilic phase” refers to a phase in which an oil-soluble ingredient is capable of dissolving.
As used herein, the term “primary emulsion” refers to a system wherein a hydrophilic phase is dispersed in an immiscible lipophilic phase.
As used herein, the term “double emulsion” refers to a primary emulsion, which has itself been dispersed in a further immiscible phase, e.g. a plant-based protein solution.
As used herein, the term “triple emulsion” refers to a double emulsion, which has itself been dispersed in a further immiscible phase, e.g. a lipophilic phase.
As used herein, the term “oil-soluble surfactant” refers to a compound that can lower the surface tension of a lipophilic phase.
As used herein, the term “multicore morphology” is used to describe a complex emulsion composed of several inner droplets dispersed in an immiscible middle phase, which is itself dispersed in an outer phase.
As used herein, the term “single core morphology” is used to describe a double emulsion composed of a single inner drop surrounded by a shell that is composed of a second, immiscible liquid, which is itself dispersed in an outer phase.
As used herein, the abbreviation “W/O” stands for “water-in-oil”.
As used herein, the abbreviation “W/O/W/O” stands for “water-in-oil-in-water-in-oil”.
The present invention provides a microcapsule comprising:
The microcapsules of the present invention can be used to encapsulate a variety of substances and find various industrial applications, including in cosmetics, food use, household product use, agrochemical use and pharmaceutical use.
In preferred microcapsules of the present invention, the hydrophilic phase comprises water.
The microcapsules of the present invention comprise a water-soluble ingredient. Suitable water-soluble ingredients for use in the microcapsules of the present invention are described below. The concentration of the water-soluble ingredient in the hydrophilic phase will vary depending upon the solubility of the specific water-soluble ingredient being employed and/or on the amount of water-soluble ingredient desired in the final microcapsule product.
Suitable water-soluble ingredients include Vitamin B1, Vitamin B2, Vitamin B3, Vitamin B5, Vitamin B6, Vitamin B7, Vitamin B9, Vitamin B12, Vitamin C, panthenol, α-hydroxy acids, water-soluble minerals salts, water-soluble plant extracts and yeasts, enzymes, antibiotics, oligopeptides, proteins and protein hydrolysates.
Suitable water-soluble ingredients include Vitamin B1, Vitamin B2, Vitamin B3, Vitamin B5, Vitamin B6, Vitamin B7, Vitamin B9, Vitamin B12, Vitamin C, panthenol, α-hydroxy acids, β-hydroxy acids, polyphenols, polysaccharides, water-soluble minerals salts, water-soluble plant extracts and yeasts, enzymes, antibiotics, oligopeptides, proteins and protein hydrolysates.
In preferred microcapsules of the present invention, the hydrophilic phase further comprises a rheology modifier (e.g. a hydrocolloid), which acts to stabilise the hydrophilic phase. Preferably, the rheology modifier is selected from acacia gum, alginic acid, pectin, xanthan gum, gellan gum, carbomer, dextrin, gelatin, guar gum, hydrogenated vegetable oil category 1, aluminum magnesium silicate, maltodextrin, carboxymethyl cellulose, microfibrillated cellulose, polymethacrylate, polyvinyl pyrrolidone, sodium alginate, starch, zein, water-insoluble cross-linked polymers such as cross-linked cellulose, cross-linked starch, cross-linked CMC, cross-linked carboxymethyl starch, cross-linked polyacrylate, and cross-linked polyvinylpyrrolidone, talc, silica, and expanded clays such as bentonite and laponite.
In preferred microcapsules of the present invention, the lipophilic phase comprises an oil. Preferably, the oil is selected from plant-based oils (e.g. vegetable oils) and synthetic oils.
In preferred microcapsules of the present invention, the lipophilic phase further comprises an oil-soluble surfactant. Preferably, the oil-soluble surfactant is selected from sucrose fatty acid esters such as sucrose stearic acid ester, sucrose palmitic acid ester, sucrose oleic acid ester, sucrose lauric acid ester, sucrose behenic acid ester, and sucrose erucic acid ester; sorbitan fatty acid esters such as sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, and sorbitan sesquioleate; glyceryl fatty acid esters such as glycerol monostearate and glycerol monooleate; and polyglyceryl fatty acid esters such as diglyceryl tetraisostearate, diglyceryl diisostearate, diglyceryl monoisostearate, and polyglycerol polyricinoleate. A particularly preferred oil-soluble surfactant is polyglycerol polyricinoleate.
Without wishing to be bound by theory, it is thought that the presence of an oil-soluble surfactant in the microcapsules of the present invention allows for the formation of a more stable primary emulsion because the oil-soluble surfactant can lower the surface tension of the lipophilic phase.
In preferred microcapsules of the present invention, the concentration of the oil-soluble surfactant in the lipophilic phase is in the range 0.01% w/w to 10% w/w, preferably in the range 0.1% w/w to 5% w/w, more preferably in the range 0.5% w/w to 2% w/w.
In preferred microcapsules of the present invention, the lipophilic phase further comprises an oil-soluble ingredient. Suitable oil-soluble ingredients for use in the microcapsules of the present invention are described below.
Further oil soluble ingredients include fatty acids; triglycerides or mixtures thereof; omega-3 fatty acids, such as a-linolenic acid (18: 3n3), octadecatetraenoic acid (18: 4n3), eicosapentaenoic acid (20: 5n3) (EPA) and docosahexaenoic acid (22: 6n3) (DHA), and derivatives thereof and mixtures thereof; fat-soluble vitamins, such as Vitamin A, Vitamin D, Vitamin E and Vitamin K; Antioxidants, such as tocopheryl and ascorbyl derivatives; retinoids or retinols; essential oils; bioflavonoids, terpenoids; synthetics of bioflavonoids and terpenoids and the like.
In preferred microcapsules of the present invention, the plant-based protein hydrogel shell is a self-assembled plant-based protein hydrogel shell.
The plant-based protein hydrogel employed as a shell in the microcapsules of the present invention is preferably made by a method comprising:
Any suitable plant-based proteins may be used. Suitable plant sources include soybean, pea, rice, potato, wheat, corn zein, sorghum, and the like. Particularly preferable plant proteins include soy proteins, pea proteins, potato proteins, rapeseed proteins and/or rice proteins, more preferably soy proteins and/or pea proteins.
Suitable plant-based proteins further include:
Abyssinian mustard or Abyssinian cabbage, Brassica elongate: elongated mustard, Brassica fruticulosa: Mediterranean cabbage, Brassica hilarionis: St Hilarion cabbage, Brassica juncea: Indian mustard, brown and leaf mustards, Sarepta mustard, Brassica napus: rapeseed, canola, rutabaga, Brassica narinosa: broadbeaked mustard, Brassica nigra: black mustard, Brassica oleracea: kale, cabbage, collard greens, broccoli, cauliflower, kai-lan, Brussels sprouts, kohlrabi, Brassica perviridis: tender green, mustard spinach, Brassica rapa (syn. B. campestris): Chinese cabbage, turnip, rapini, komatsuna, Brassica rupestris: brown mustard, Brassica tournefortii: Asian mustard
For the avoidance of doubt, the plant-based microcapsules of the present invention do not encompass plants in their natural state, e.g. naturally formed plant cells, organelles or vesicles are not plant-based microcapsules of the present invention.
In the method described above, the plant-based protein hydrogel is formed by adding the plant-based protein into a solvent system, wherein the solvent system comprises two or more miscible co-solvents as defined herein.
The first co-solvent increases solubility of the plant-based protein(s). The first co-solvent may be considered a solubilising co-solvent. There may be one or more solubilising co-solvent(s) and the solubilising co-solvent(s) may fully or partially solubilise the plant-based protein(s).
Examples of solubilising co-solvents are organic acids. An organic acid is an organic compound with acidic properties. Suitable organic acids include acetic acid or an α-hydroxy acid. Suitable organic acids include acetic acid, an α-hydroxy acid, or a β-hydroxy acid. Suitable α-hydroxy acids include glycolic acid, lactic acid, malic acid, citric acid and tartaric acid. Suitable β-hydroxy acids include β-hydroxypropionic acid, β-hydroxybutyric acid, β-hydroxy β-methylbutyric acid, 2-hydroxybenzoic acid and carnitine. Preferred organic acids are acetic acid and lactic acid. Using an organic acid enables solubilisation of the plant protein and also allows for mild hydrolysis of the protein. For example, without wishing to be bound by theory, the solubility of plant-based proteins in organic acid is possible due to: i) the protonation of proteins and ii) the presence of an anion solvation layer which contributes to a reduction of hydrophobic interactions. Once initially dissolved in organic acid, the protonation of plant-based proteins can help to stabilise them in its non-solvent, for example water.
Preferably, the first co-solvent is an organic acid.
The second co-solvent has decreased solubility of the plant-based protein(s), as compared to the first co-solvent. The second co-solvent may be considered a de-solubilising co-solvent. There may be one or more de-solubilising co-solvent(s).
Examples of de-solubilising second co-solvent(s) are an aqueous buffer solution. In a further embodiment, the second co-solvent may be water, ethanol, methanol, acetone, acetonitrile, dimethylsulfoxide, dimethylformamide, formamide, 2-propanol, 1-butanol, 1-propanol, hexanol, t-butanol, ethyl acetate or hexafluoroisopropanol. In a particularly preferred embodiment, the second co-solvent is water and ethanol. In a further particularly preferred embodiment, the second co-solvent is water.
Preferably, the solvent system comprises a co-solvent ratio of about 20-80% v/v, preferably about 20-60% v/v, about 25-55% v/v, about 30-50% v/v, about 20%, about 30%, about 40% about 50% or about 60% v/v, most preferably about 30-50% v/v. Preferably, the concentration of plant-based protein(s) in the solvent system is 25-200 mg/ml, more preferably 50-150 mg/ml. The ratio of organic acid may vary depending on protein concentration, e.g. using a higher organic acid ratio with increasing protein concentration.
Preferably, the degree of protein hydrolysis is controlled to modify the properties of the resultant hydrogel. For example, increasing the acid concentration present during formation will increase the degree of protein hydrolysis. Higher degree of protein hydrolysis leads to the formation of less rigid hydrogels.
In order to form the solution comprising one or more plant-based protein(s), it may be necessary to apply physical stimulus to the protein/solvent system mixture to enable dissolution of the protein. Suitable physical stimulus includes heating, ultrasonication, agitation, high-shear mixing or other physical techniques. A preferred technique is heating, optionally with subsequent ultrasonication.
Preferably, the protein/solvent system mixture is subjected to a physical stimulus which is heating, wherein the solution is heated to about or above 70° C. More preferably, the protein/solvent system mixture is heated to about or above 75° C., about or above 80° C., about or above 85° C. or about 90° C. Even more preferably, the protein/solvent system mixture is heated to 85° C.
Preferably, the protein/solvent system mixture is subjected to a physical stimulus which is heating fora period of about 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, or greater than 30 minutes. A preferred heating time period is about 30 minutes. The heated protein/solvent system mixture is optionally subjected to subsequent ultrasonication (e.g. for a period of up to 60 minutes, more preferably for a period of up to 10 minutes).
The protein solution is then heated such that the liquid solution is held above the sol-gel transition for the protein(s). By modifying the solvent system (for example through selection of the choice of organic acid, the ratio of organic acid to further solvent or through further means) it is possible to modify the sol-gel transition temperature for the protein(s). Through appropriate selection of conditions, it is possible to carefully control the sol-gel transition of the protein thereby controlling the formation of the hydrogel. Preferably, the protein solution is heated to about or above 70° C. More preferably, the protein is heated to about or above 75° C., about or above 80° C., about or above 85° C. or about 90° C. Even more preferably, the protein is heated to 85° C.
The protein solution may be held at elevated temperature for a time period of about 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 45 minutes or 1 hour. A preferred time period is at least 30 minutes to enable the proteins to fully solubilise. It is possible to hold the protein solution at an elevated temperature for a longer period of time. This may be useful for a commercial batch process or for use in a fluidic processing step where it is necessary to retain the protein solution in liquid form for higher periods of time.
Having heated the protein solution to above the sol-gel transition temperature of the protein solution, the temperature of the protein solution can be reduced to a second temperature below the sol-gel transition temperature to facilitate formation of the hydrogel. The second temperature may be room temperature. The protein solution may be held at the reduced temperature for a time period of about 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or about 30 minutes. A particular reduced time period is about 5 minutes. However the method described above allows the protein to remain in solution for long periods of time. As such, depending on need, the protein solution can be kept above the sol-gel transition temperature for as long as required to retain the protein in liquid form. This could be hours, days or more, but is preferably of the order of minutes or hours. Also, since the reaction is reversible, a solution could, for example be kept at a lower temperature (for example room temperature) where a hydrogel will form but thereafter heated to above the sol-gel transition temperature to return the solution to a liquid state for further processing. Protein hydrogels in this way could be stored for hours, days, weeks, months or years as the hydrogel remains stable for a long time.
The particular temperatures will depend on the properties of the protein source, the solvent conditions used and therefore the sol-gel transition temperature. Alternatively, the elevated and reduced temperatures may be relatively fixed (for example about 85° C. then about room temperature) and the co-solvent mixture conditions are adjusted to ensure a suitable sol-gel transition temperature for the selected plant-based protein.
Without wishing to be bound by theory, it is believed that when the plant protein is added to the solvent system the plant protein form a highly viscous dispersion of insoluble colloidal protein aggregates.
Further, it is believed that the application of mechanical agitation, for example ultrasonication, disrupts large colloidal protein aggregates into smaller ones, as well as disrupting protein intermolecular interactions. Using this approach, the size of the protein aggregates can be significantly reduced, before gelation, to particle sizes below 100 nm. Preferably, the method described above comprises protein aggregates with an average size less than 200 nm, preferably less than 150 nm, less than 125 nm, less than 100 nm, less than 90 nm, less than 80 nm, less than 70 nm, less than 60 nm, less than 50 nm, less than 40 nm, or less than 30 nm.
Aggregate size may be measured by Dynamic Light Scattering (DLS). Suitable apparatus to measure aggregate size is a Zetasizer Nano S (Malvern).
Further, it is believed that upon heating the protein solution in the presence of a co-solvent system to above the sol-gel temperature, the plant proteins partially unfold, resulting in the exposure of hydrophobic amino acids initially buried within the protein native structure. Once partially unfolded, the co-solvents are able to interact with the unfolded protein molecules. For example, an organic acid has greater access to protonate amino acid residues, as well as enabling the formation of anion salt bridges that stabilise hydrophobic interactions. Also, upon heating at elevated temperatures, protein-protein non-covalent intermolecular contacts are disrupted. Further, it is believed that upon cooling the protein solution to below the sol-gel temperature, protein-protein non-covalent intermolecular contacts are enabled, thus promoting the self-assembly of plant protein molecules into a network of supramolecular aggregates.
After gelation, the aggregates may be fine stranded. The aggregates may have a median average length of between 50 to 500 nm. The aggregates may have a mean average length of between 50 to 500 nm. 80% of the aggregates may have an average length of between 50 to 500 nm. The aggregates may have a median height of between to 50 nm. The aggregates may have a mean average height of between 5 to 50 nm. 80% of the aggregates may have an average height of between 5 to 50 nm. In a preferred embodiment, the aggregates have a median average length of between 50 to 500 nm and/or a median average height of between 5 to 50 nm.
Without wishing to be bound by theory, it is thought that the method described above allows the plant proteins to aggregate into supramolecular structures held by intermolecular hydrogen bonding interactions, and in particular between the β-strands. Thus, preferably, the hydrogels employed as a shell in the microcapsules of the present invention has high levels of β-sheet intermolecular interactions.
Preferably, the hydrogels employed as a shell in the microcapsules of the present invention have a protein secondary structure with at least 40% intermolecular β-sheet, at least 50% intermolecular β-sheet, at least 60% intermolecular β-sheet, at least 70% intermolecular β-sheet, at least 80% intermolecular β-sheet, or at least 90% intermolecular β-sheet. Preferably, the % intermolecular β-sheet content is measured by FTIR. It is believed that previous gels made from plant-based protein sources may have lower amounts of intermolecular β-sheets in the secondary structure, leading to prior art disadvantageous properties.
The plant-based protein hydrogel employed as a shell in the microcapsules of the present invention has advantageous mechanical properties. For example, the ability to reversibly change from gel to liquid upon temperature change enables advantageous manufacturing capabilities.
Preferably, the hydrogels employed as a shell in the microcapsules of the present invention have a storage modulus (G′) at 10 rad/s of greater than 500 Pa, greater than 1000 Pa, greater than 2500 Pa, greater than 3000 Pa, greater than 4000 Pa.
Preferably, the hydrogels employed as a shell in the microcapsules of the present invention exhibit shear-thinning behaviour, where the viscosity decreases upon increasing shear rates.
Preferably, the hydrogels employed as a shell in the microcapsules of the present invention are not adversely affected by processing conditions normally present during final product manufacturing processes, e.g. exposure to high temperatures (e.g. >95° C.) and/or high shear conditions. More preferably, the hydrogels employed as a shell in the microcapsules of the present invention are chemically and/or mechanically stable to such processing conditions.
Preferably, the hydrogels employed as a shell in the microcapsules of the present invention are stable under low pH conditions. More preferably, the hydrogels employed as a shell in the microcapsules of the present invention are stable at a pH of less than 3 (e.g. at a pH of less than 2). This is particularly advantageous when the microcapsules are to be employed in a food, beverage or pharmaceutical product. Preferably, the hydrogels employed as a shell in the microcapsules of the present invention exhibit a unique thermoreversible gelling behaviour. Upon heating at elevated temperatures and/or by applying mechanical agitation, the protein gels return to liquid form. This is a unique property that has not been seen with prior hydrogels, which would not upon heating return to a fully liquid state. In contrast, hydrogels employed as a shell in the microcapsules of the present invention can. Preferably, upon heating at elevated temperatures and/or by applying mechanical agitation, protein solutions may have a storage modulus lower than 250 Pa, lower than 100 Pa, lower than 50 Pa, lower than Pa. This enables the microcapsules of the present invention to have unique manufacturing capabilities.
Equally, if desired, thermoreversibility can be removed by removing the solvent system. Once the plant-based microcapsules of the present invention have been formed, the solvent system can be washed out which will stop the thermoreversible properties of the microcapsules. Thus, if the microcapsule is thereafter heated it will remain stable and will not re-melt. This enables, for example, microcapsules according to the present invention to be subjected to high temperature processes yet remain intact and stable.
Thus, the hydrogels employed as a shell in the microcapsules of the present invention have unique properties not seen in prior plant-based hydrogels. These include the ability of forming hydrogels from plant-based proteins at high concentrations (i.e. 5%-15% w/w) from commercially available sources, and the ability of keeping such highly concentrated protein solutions in the liquid state upon heat denaturation, which enables their moulding into well-defined objects.
A feature of the hydrogels employed as a shell in the microcapsules of the present invention is that it is not necessary to provide cross-linking agents as the plant proteins will self-form hydrogels. Thus, preferably the hydrogels employed as a shell in the microcapsules of the present invention do not contain or do not substantially contain a cross-linking agent.
However, in an alternative embodiment, the hydrogels employed as a shell in the microcapsules of the present invention may comprise a cross-linking agent. Suitable cross-linking agents include microbial transglutaminase, glutaraldehyde, formaldehyde, glyoxal, phenolic compounds, epoxy compounds, genipin or dialdehyde starch. Alternatively, the cross-linking agent is sodium tripolyphosphate.
Due to the porous network of the hydrogel, the solvent mixture within the hydrogel can be exchanged for another solvent mixture without compromising the mechanical stability of the hydrogel. A solvent-exchange process can be performed to remove the organic acid from the hydrogel porous network.
Preferably, the hydrogels employed as a shell in the microcapsules of the present invention can incorporate one or more plasticizers. Possible plasticizers include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, sorbitol, mannitol, xylitol, fatty acids, glucose, mannose, fructose, sucrose, ethanolamine, urea, triethanolamine; vegetable oils, lecithin, waxes and amino acids.
Preferably the hydrogel may comprise about 1% plasticiser, about 2%, about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60% or more. Alternatively, the hydrogel may comprise between about 5-50% plasticiser, about 10-50%, about 20-40% about 15-35% or about 20% plasticizer.
Adding a plasticizer can influence the mechanical properties of the material. Typically, adding a plasticiser will increase the elasticity of the material but this typically conversely reduces the strength of the resultant material.
The use of plant-based hydrogels as a shell in the microcapsules of the present invention has a number of advantages over previously used animal or petrochemical sources. Firstly, plant sources are renewable and can be efficiently obtained in an environmentally efficient manner. Secondly, plant sources are biodegradable and are therefore an environmentally sound alternative to other plastics. Thirdly, in contrast to animal derived proteins, plant-based proteins have the significant advantage that they do not introduce animal derived proteins into a human. This has positive impacts both from a pharmacological and pharmaceutical perspective where animal sourced material must undergo stringent checks and processes to ensure no adverse elements are present (for example removing prions and the like); but also because the products are suitable for vegetarian/vegans.
Since plant-based proteins are naturally present in a human (or other animal)'s diet, the plant-based hydrogels employed as a shell in the microcapsules of the present invention exhibit a higher degree of digestibility compared to other biopolymers such as polysaccharides (for example, alginates or chitosan). This makes them particularly suitable for pharmaceutical, food and/or cosmetic use.
In preferred microcapsules of the present invention, the protein content of the plant-based protein hydrogel shell is 5 to 20 g/100 g, more preferably 5 to 15 g/100 g, even more preferably 5 to 12.5 g/100 g.
In preferred microcapsules of the present invention, the Boisen protein digestibility of the plant-based protein hydrogel shell as measured according to the Boisen protocol (detailed in Animal Feed Science and Technology, 51, pp. 29-43 (1995)) is 80 to 100%, more preferably 90 to 100%, even more preferably 95 to 100%.
In preferred microcapsules of the present invention, the biodegradation percentage based upon O2 consumption of the plant-based protein hydrogel shell as measured according to ISO-14851 after 28 days is 70 to 100%, more preferably 80 to 100%, even more preferably 85 to 100%.
In preferred microcapsules of the present invention, the biodegradation percentage based upon CO2 production of the plant-based protein hydrogel shell as measured according to ISO-14851 after 28 days is 70 to 100%, more preferably 75 to 100%, even more preferably 80 to 100%.
In preferred microcapsules of the present invention, the hydrophilic phase is dispersed in the lipophilic phase.
In preferred microcapsules of the present invention, the hydrophilic phase and the lipophilic phase are encapsulated by the plant-based protein hydrogel shell.
In preferred microcapsules of the present invention, the hydrophilic phase and the lipophilic phase form a water-in-oil emulsion.
In preferred microcapsules of the present invention, the water-in-oil emulsion is encapsulated by the plant-based protein hydrogel shell. Such an embodiment is depicted graphically in
Preferred microcapsules of the present invention have a multicore morphology. Such an embodiment is depicted graphically in
Alternative preferred microcapsules of the present invention have a single core morphology. Such an embodiment is depicted graphically in
The microcapsules of the present invention encapsulate water-soluble ingredients. The microcapsules of the present invention optionally also encapsulate oil-soluble ingredients.
In preferred microcapsules of the present invention, the plant-based protein hydrogel shell can encapsulate any nutraceutical, cosmetic, pharmaceutical or agrochemical suitable active agent including vitamins, essential fatty acids, antioxidants, small molecules, hydrophilic small molecules, hydrophobic small molecules, proteins, antibodies, antibody-drug conjugates, fragrances and other large molecules.
Suitable encapsulated agents include one or more agents selected from:
In particularly preferred microcapsules of the present invention, the plant-based hydrogel shell encapsulates at least one vitamin or mineral. Such microcapsules have a useful application in food and beverage products, e.g. for fortification of the food or beverage, or in pharmaceutical products, e.g. for delivery of active ingredients.
Preferably, the at least one vitamin or mineral is selected from Vitamin A, Vitamin B1, Vitamin B2, Vitamin B3, Vitamin B5, Vitamin B6, Vitamin B7, Vitamin B9, Vitamin B12, Vitamin C, Vitamin D, Vitamin E, Vitamin K, magnesium, sodium, potassium, zinc, iron, calcium, iodine and phosphorous, or mixtures thereof.
As would be understood by a skilled person, the at least one vitamin may be present in the microcapsule as a pro-vitamin, which degrades to the active vitamin during use, e.g. under the conditions of the digestive system of a human or animal.
In preferred microcapsules of the present invention, the plant-based protein hydrogel shell has a thickness in the range 10 nm to 50,000 μm, preferably in the range 10 μm to 100 μm, more preferably in the range 10 μm to 50 μm, most preferably in the range 1 μm to 10 μm.
In preferred microcapsules of the present invention, the plant-based protein hydrogel shell has a thickness of about 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 30 μm, 35 μm, 40 μm, or 50 μm.
In preferred microcapsules of the present invention, the microcapsule has a size of less than 1 mm in the largest dimension, less than 900 μm, less than 800 μm, less than 700 μm, less than 600 μm, less than 500 μm, less than 400 μm, less than 300 μm, less than 200 μm, or less than 100 μm.
In preferred microcapsules of the present invention, the microcapsule releases the water-soluble ingredient and/or the oil-soluble ingredient to a surface upon application of pressure to the microcapsule (e.g. the application of pressure breaks the plant-based protein hydrogel shell). Preferably, the surface is a bio-surface. More preferably, the bio-surface is selected from hair, skin and teeth. Alternatively, the surface is a textile. The porous nature of the plant-based protein hydrogel shell allows for a controlled release of the water-soluble ingredient and/or the oil-soluble ingredient from the microcapsule.
In preferred microcapsules of the present invention, the microcapsule releases the water-soluble ingredient and/or the oil-soluble ingredient as a result of enzymatic degradation of the plant-based protein hydrogel shell. Preferably, said enzymatic degradation occurs in the digestive system of a human or animal. Alternatively, said enzymatic degradation is triggered by enzymes in the skin of a human or animal.
The present invention also provides a composition comprising at least one microcapsule as hereinbefore described and an external phase.
In preferred compositions of the present invention, the at least one microcapsule is dispersed in the external phase.
In preferred compositions of the present invention, the external phase is an external aqueous phase (e.g. an aqueous salt solution). Preferably, the external aqueous phase is a continuous external aqueous phase. In alternative preferred compositions of the present invention, the external phase is an external lipophilic phase.
Without wishing to be bound by theory, it is thought that control of the relative ionic potential inside and outside the microcapsules can allow for adjustment of the osmotic pressure across the microcapsules. In turn, this can allow for control over the release properties of ingredients from the microcapsules (e.g. controlled or delayed release of the water-soluble ingredient(s) from the microcapsules).
This structure of the microcapsules of the present invention means that the encapsulated primary emulsion is kept stable over time/on storage, e.g., the encapsulated primary emulsion can be protected from oxidation, degradation due to light, reaction with the external environment and/or evaporation etc. For example, vitamin-containing microcapsules of the present invention will remain stable over time in the food/beverage they may have been incorporated into, but once consumed can then provide controlled release of the vitamin(s) in the digestive tract.
Preferred microcapsules of the present invention encapsulate at least one vitamin or mineral, wherein at least 25%, more preferably at least 40%, even more preferably at least 50%, even more preferably at least 60% of the at least one vitamin or mineral initially encapsulated remains present inside the microcapsule after incubation in water at 20° C. for 10 days, as determined by HPLC.
Preferably, the at least one vitamin or mineral is selected from Vitamin A, Vitamin B1, Vitamin B2, Vitamin B3, Vitamin B5, Vitamin B6, Vitamin B7, Vitamin B9, Vitamin B12, Vitamin C, Vitamin D, Vitamin E, Vitamin K, magnesium, sodium, potassium, zinc, iron, calcium, iodine and phosphorous, or mixtures thereof.
As would be understood by a skilled person, the at least one vitamin may be present in the microcapsule as a pro-vitamin, which degrades to the active vitamin during use, e.g. under the conditions of the digestive system of a human or animal.
The present invention also provides method for preparing a microcapsule as hereinbefore described, comprising:
In preferred methods of the invention, said plant-based protein solution comprises one or more plant-based protein(s) in a solvent system, wherein the solvent system comprises miscible co-solvents; wherein a first co-solvent increases solubility of the plant-based protein(s), and a second co-solvent decreases solubility of the plant-based protein(s). Preferred features of the plant-based protein(s), the first co-solvent and the second co-solvent are discussed above.
In preferred methods of the present invention, the primary emulsion has a diameter that is less than or equal to 5 μm, preferably less than or equal to 4 μm, more preferably less than or equal to 3 μm, even more preferably less than or equal to 2 μm, most preferably less than or equal to 1 μm.
In preferred methods of the present invention, the double emulsion has a diameter that is less than or equal to 100 μm, preferably less than or equal to 50 μm, more preferably less than or equal to 30 μm.
In preferred methods of the present invention, the triple emulsion has a diameter that is less than or equal to 200 μm, preferably less than or equal to 150 μm, more preferably less than or equal to 100 μm.
In preferred methods of the present invention, the first and second lipophilic phases are the same (e.g. they are the same type of oil).
In alternative preferred methods of the present invention, the first and second lipophilic phases are different (e.g. they are different types of oils).
In preferred methods of the present invention, the first and/or second lipophilic phase further comprises an oil-soluble surfactant. Preferably, the oil-soluble surfactant(s) is selected from sucrose fatty acid esters such as sucrose stearic acid ester, sucrose palmitic acid ester, sucrose oleic acid ester, sucrose lauric acid ester, sucrose behenic acid ester, and sucrose erucic acid ester; sorbitan fatty acid esters such as sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, and sorbitan sesquioleate; glyceryl fatty acid esters such as glycerol monostearate and glycerol monooleate; and polyglyceryl fatty acid esters such as diglyceryl tetraisostearate, diglyceryl diisostearate, diglyceryl monoisostearate, and polyglycerol polyricinoleate. A particularly preferred oil-soluble surfactant is polyglycerol polyricinoleate.
In preferred methods of the present invention, the oil-soluble surfactants in the first and second lipophilic phase are the same.
In alternative preferred methods of the present invention, the oil-soluble surfactants in the first and second lipophilic phase are different.
In preferred methods of the present invention, said microcapsule is formed using a microfluidic device.
Preferred methods of the present invention further comprise drying the microcapsule to form a dry powder. Preferably, said drying is selected from spray drying, fluid bed drying and/or tray drying. The drying step allows for ease of handling of the microcapsules, for example by avoiding the need to transport the final microcapsules in large quantities of water.
The present invention also provides a microcapsule prepared according to the method hereinbefore described.
An alternative method for preparing a microcapsule as hereinbefore described comprises:
The present invention also provides a method for preparing a composition as hereinbefore described, comprising:
In preferred methods of the invention, said plant-based protein solution comprises one or more plant-based protein(s) in a solvent system, wherein the solvent system comprises miscible co-solvents; wherein a first co-solvent increases solubility of the plant-based protein(s), and a second co-solvent decreases solubility of the plant-based protein(s). Preferred features of the plant-based protein(s), the first co-solvent and the second co-solvent are discussed above.
In preferred methods of the present invention, the primary emulsion has a diameter that is less than or equal to 5 μm, preferably less than or equal to 4 μm, more preferably less than or equal to 3 μm, even more preferably less than or equal to 2 μm, most preferably less than or equal to 1 μm.
In preferred methods of the present invention, the double emulsion has a diameter that is less than or equal to 100 μm, preferably less than or equal to 50 μm, more preferably less than or equal to 30 μm.
In preferred methods of the present invention, the triple emulsion has a diameter that is less than or equal to 200 μm, preferably less than or equal to 150 μm, more preferably less than or equal to 100 μm.
In preferred methods of the present invention, the second lipophilic phase comprises an oil. Preferably, the oil is selected from plant-based oils (e.g. vegetable oils) and synthetic oils.
In preferred methods of the present invention, the first and second lipophilic phases are the same (e.g. they are the same type of oil).
In alternative preferred methods of the present invention, the first and second lipophilic phases are different (e.g. they are different types of oils).
In preferred methods of the present invention, the first and/or second lipophilic phase further comprises an oil-soluble surfactant. Preferably, the oil-soluble surfactant(s) is selected from sucrose fatty acid esters such as sucrose stearic acid ester, sucrose palmitic acid ester, sucrose oleic acid ester, sucrose lauric acid ester, sucrose behenic acid ester, and sucrose erucic acid ester; sorbitan fatty acid esters such as sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, and sorbitan sesquioleate; glyceryl fatty acid esters such as glycerol monostearate and glycerol monooleate; and polyglyceryl fatty acid esters such as diglyceryl tetraisostearate, diglyceryl diisostearate, diglyceryl monoisostearate, and polyglycerol polyricinoleate. A particularly preferred oil-soluble surfactant is polyglycerol polyricinoleate.
In preferred methods of the present invention, the oil-soluble surfactants in the first and second lipophilic phase are the same.
In alternative preferred methods of the present invention, the oil-soluble surfactants in the first and second lipophilic phase are different.
Preferred methods of the present invention further comprise adding suspending agents to said external aqueous phase. Preferably, said suspending agents are selected from acacia gum, alginic acid, pectin, xanthan gum, gellan gum, carbomer, dextrin, gelatin, guar gum, hydrogenated vegetable oil category 1, aluminum magnesium silicate, maltodextrin, carboxymethyl cellulose, polymethacrylate, poly vinyl pyrrolidone, sodium alginate, starch, zein, water-insoluble cross-linked polymers such as cross-linked cellulose, cross-linked starch, cross-linked CMC, cross-linked carboxymethyl starch, cross-linked polyacrylate, and cross-linked polyvinylpyrrolidone, and expanded clays such as bentonite and laponite.
In preferred methods of the present invention, said microcapsule is formed using a microfluidic device.
The present invention also provides a composition prepared according to the method hereinbefore described.
An alternative method for preparing a composition as hereinbefore described comprises:
Preferably, the alternative method further comprises:
The present invention also provides a food, beverage, cosmetic, pharmaceutical, medical device, biomaterial, or agrochemical incorporating a microcapsule as hereinbefore described, or a composition as hereinbefore described.
The present invention also provides a food, beverage, cosmetic, home care product, personal care product, pharmaceutical, medical device, biomaterial, or agrochemical incorporating a microcapsule as hereinbefore described, or a composition as hereinbefore described.
The present invention also provides the use of a microcapsule as hereinbefore described or a composition as hereinbefore described to produce a food, beverage, cosmetic, home care product, personal care product, pharmaceutical, medical device, biomaterial, or agrochemical.
Preparation of Internal Phase:
A water-in-oil emulsion was produced by emulsifying 200 μl of a 0.25 M CaCl2 solution in 800 μl of Miglyol 840 containing 4% (w/w) PGPR by ultrasonication for 30 seconds.
Preparation of Middle Phase:
Pea Protein Isolate was added to a 35% (v/v) lactic acid aqueous solution at a final protein concentration of 125 mg/ml. A dispersion of non-soluble protein was obtained. For solubilisation of the protein, the mixture was exposed to ultrasonication for 30 min (using a Bandelin Sonopuls HD 4200 Ultrasonic Homogeniser operating under the following parameters: High-Frequency Power Output=200 W, Frequency=20 KHz, Amplitude=20%). During this process, the sample temperature was kept at 85° C.-90° C. After 30 min, a completely translucent liquid solution was obtained. The dispersed liquid PPI phase (125 mg/ml PPI in 35% v/v acetic acid, kept at 85° C.) was loaded in a 15 ml tube and rapidly placed on a heating block at 85° C. In order to prevent the gelation of the PPI solution during transport into the microfluidic device, a custom-made silicone heater (Holroyd Components), comprising a 1/32″ ID stainless steel tubing was used to maintain the temperature of the PTFE tubing connecting the PPI reservoir and the inlet in the microfluidic device. The silicon heater temperature was controlled by a custom-built temperature controller
Preparation of External Oil Phase:
008-FluoroSurfactant was dissolved in HFE-7500 3M™ Novec™ to a final concentration of 2% (w/w).
Preparation of Microcapsules:
Non-planar microfluidic devices (droplet generators) were fabricated using standard soft lithography techniques with a negative master photoresist (SU8 3050), as described in Biomacromolecules 2017, 18, 11, 3642-3651. For the fabrication of a triple emulsion, a tandem emulsification approach was followed. The first non-planar droplet generator device was comprised of an internal channel (50×50 μm), and an external channel (100×100 μm), and was rendered hydrophilic by exposure to oxygen plasma for 500 seconds and 80 W. The second non-planar droplet generator microfluidic device was comprised of an internal channel (200×200 μm) and an external channel (300×300 μm), and was rendered hydrophobic by flushing all channels with a solution of Duxback®. Both devices were connected via a small 1/32″ OD PTFE tubing.
Droplets of −50 μm diameter were first generated by pumping the internal and middle phase into the hydrophilic device by a pressure-driven system (Elveflow OB1), thus obtaining a double emulsion. The generated droplets were transferred to the hydrophobic device and emulsified again by the outer phase, thus obtaining a triple emulsion.
Different pressure rates were tested until a uniform and continuous generation of a monodisperse population of microdroplets was achieved. Final pressure rates were 350 mbar for the internal phase, 500 mbar for the middle protein phase and 180 mbar for the external oil phase. The generated droplets were collected in a glass vial, and were kept at 10° C. for 12 h to ensure the gelation process was complete.
The formed microcapsules were then washed by a standard de-emulsification procedure: the continuous oil phase containing fluorosurfactant was first removed from the vial. For 500 ul of microcapsules, an equal volume of 10% PFO solution in HFE-7500 3M™ Novec™ was added and thoroughly mixed for 30 seconds. The 10% PFO solution in HFE-7500 3M™ Novec™ was then removed and two subsequent oil washes were performed by adding an equal volume of pure HFE-7500 3M™ Novec™. Finally, 2500 ul of a 0.1 M CaCl2 solution were added to the vial, resulting in the transfer of the microcapsules from the oil to the aqueous phase. The supernatant containing the microcapsules suspension was transferred to a separate vial.
Preparation of Internal Phase:
A water-in-oil (W/O) emulsion was produced by probe ultra-sonication. 0.03% gellan gum with 1 M Vitamin B6 solution was emulsified in Miglyol 829 oil with 4 wt % PGPR in a volume ratio of 1 part aqueous to 4 parts oil.
Preparation of Middle Phase:
500 ml of a mixture was prepared consisting of 10% (w/v) Pea Protein Isolate in 35% (v/v) lactic acid solution. The mixture was sonicated to disrupt large colloidal aggregates (Hielscher UIP1000hdT (1000 W, 20 kHz)), after which a transparent solution was obtained. The energy applied was 500 kJ over 90 minutes.
Preparation of Continuous Oil Phase:
The external continuous oil phase comprised Miglyol 840 containing 2 wt % PGPR.
Preparation of Microcapsules:
The internal phase was emulsified into the middle phase by using a membrane emulsification device (AXF-1, Micropore Ltd). The size of the droplets created are approximately 40 μm. The resultant emulsion was continuously pumped into a glass jacketed reactor containing the continuous oil phase at 55° C., and shear was applied by a Heidolph Hei-TORQUE Core overhead stirrer with a three blade marine prop impeller to generate a W/O/W/O triple emulsion. The ratio of double emulsion from the Micropore device to bulk emulsification oil was 1:4.
The continuous oil phase was maintained at a temperature of 55° C. whilst being stirred for 5 minutes at 800 rpm, after which the reactor was cooled with an ice water jacket to reduce the temperature of the completed triple emulsion to less than 20° C. The formed microcapsules were allowed to fully settle at 3° C. for 3-4 hours before decanting the continuous oil phase. A solution of 0.1 M sodium tripolyphosphate with 4 wt % Polysorbate 80 was then added to the microcapsule slurry. This mixture was left for 18 h with gentle mixing (150 rpm using an overhead stirrer). The capsules were then washed with a hard water solution (containing NaHCO3 at 192 mg/L, CaSO4·2H2O at 120 ml/L, MgSO4 at 120 mg/L, KCl at 8 mg/L) three times in order to ensure the continuous phase oil was thoroughly removed from the surface of the microcapsules.
The final microcapsules were then decanted and stored in the fridge (3° C.) in the wash solution made up to a 50 vol % slurry.
Controlled Release Experiments:
The retention of pyrirdoxine hydrochloride (Vitamin B6) in the microcapsules was followed over the course of 10 days by quantifying the concentration of non-encapsulated pyrirdoxine hydrochloride using HPLC analysis.
A 200 μl aliquot of washed microcapsules in a 50 vol % slurry in hard water (containing NaHCO3 at 192 mg/L, CaSO4·2H2O at 120 ml/L, MgSO4 at 120 mg/L, KCl at 8 mg/L) was added to 800 μl of hard water (solution A). To quantify the total amount of pyridoxine hydrochloride in the sample (i.e. encapsulated and non-encapsulated), a control sample of solution A was exposed to sonication using an ultrasonic homogeniser (Bandelin, HD4200) for 30 seconds at 50% amplitude in order to break all the microcapsules. The sample was then centrifuged at 14000 rpm for 15 min, and a 200 μl aliquot from the supernatant was taken for HPLC analysis to quantify the total amount of pyridoxine hydrochloride in 1 ml of sample.
To quantify the initially non-encapsulated pyridoxine hydrochloride in solution A, a 200 μl aliquot from the supernatant was taken for HPLC analysis. The amount of encapsulated pyridoxine hydrochloride in solution A could then be determined by subtraction of the measured amount of non-encapsulated pyridoxine hydrochloride from the measured initial total amount of pyridoxine hydrochloride present.
To quantify the retention of pyridoxine hydrochloride in the microcapsules, a 1 ml sample of solution A was left to incubate at 20° C. for 10 days, after which 200 μl of supernatant were taken for HPLC analysis. This provides a measure of the pyridoxine hydrochloride that has leaked from the microcapsules and is no longer encapsulated. This value is then subtracted from the initial total pyridoxine hydrochloride amount to give the encapsulated amount after a specified period of time. This can then be calculated as a percentage of the initially encapsulated pyridoxine hydrochloride amount.
HPLC quantification confirmed the retention of more than 60% pyridoxine hydrochloride inside the microcapsules after 10 days. The results are shown in Table 1.
In order to assess the digestibility of the microcapsules of the present invention, the plant-based protein hydrogel shell was subjected to a digestibility test.
Sample Preparation:
Empty microcapsules having only a plant-based protein hydrogel shell were prepared as follows:
400 ml of a mixture was prepared consisting of 12.5% (w/v) Pea Protein Isolate in 35% (v/v) lactic acid solution. The mixture was sonicated to disrupt large colloidal aggregates (Hielscher UIP500hdT (500 W, 20 kHz)), after which a transparent solution was obtained. The energy applied was 100 kJ over 15 minutes.
This solution was poured into 1 L of 85° C. Miglyol 840 oil (with 2 wt % PGPR) in a 2 l vessel, whilst the Miglyol was being stirred at 1100 rpm with an overhead stirrer. After 1 min of stirring at 1100 rpm, the speed of stirring was turned down to 500 rpm, and the mixture was cooled to 20° C. by surrounding the container with ice water.
After cooling, stirring was ceased, and the mixture was stored at 3° C. for 18 h to enable the spheres formed by the emulsification process to settle. The supernatant oil was then poured off. The spheres were then washed with a series of aqueous solutions: 0.1 M CaCl2) plus 0.5 wt % Polysorbate 80; 0.1 M CaCl2; 0.1 M Na Citrate and 20 mM sodium citrate buffer. The wash steps removed the residual oil and raised the pH to 5.4. The process yielded spheres with a mean diameter of 83 micron.
Test Method and Results:
Protein digestibility was measured by following the Boisen protocol as detailed in Animal Feed Science and Technology, 51, pp. 29-43 (1995). The measured Boisen Protein digestibility was 100.8±2.0%. The control sample (commercial Pea Protein Isolate, ProEarth, from Cambridge Commodities Ltd) had a Boisen Protein digestibility of 99.7±2.0%.
The results therefore show that the plant-based protein hydrogel shell of the microcapsules of the present invention has a digestibility that is comparable to pure pea protein. The microcapsules of the present invention therefore have a useful application in food and beverage products.
In order to assess the biodegradability of the microcapsules of the present invention, the plant-based protein hydrogel shell was subjected to a biodegradability test.
Sample Preparation:
Empty microcapsules having only a plant-based protein hydrogel shell were prepared as described in Example 4. Following this preparation, the microcapsule slurry was poured into a tray and dried in an oven at 85° C. for 3 to 4 h until the dried material reached a water activity of 0.5.
Test Method:
The dried protein microcapsules were then subjected to an aqueous aerobic biodegradability test in fresh water according to the ISO-14851 standard, using cellulose as a reference standard.
Results:
The amount of biodegradation based on O2 consumption is expressed as the ratio of the Biochemical Oxygen Demand (BOD, corrected for the control) to the Theoretical Oxygen Demand (ThOD) of the used test material.
Table 2 shows the ThOD (theoretical oxygen demand), net O2 consumption and the biodegradation percentage of the reference test and the tested microcapsules. An overview of the evolution of the biodegradation percentage (based on O2 consumption) of the two different materials is given in
After 28 days, as measured by O2 consumption, the reference sample cellulose reached a biodegradation percentage of 82.4%. The biodegradation of the tested microcapsules proceeded further, with an absolute biodegradation of 87.5% having been measured.
The biodegradation based on CO2 production is calculated as the percentage of solid carbon of the test material which has been converted to CO2.
The CO2 evolved was determined by titration. Table 3 shows the TOC (total organic carbon content), net CO2 production and the biodegradation percentage of the reference test and the tested microcapsules. An overview of the evolution of the biodegradation percentages (based on CO2 production) of the two different materials is given in
After 28 days, as measured by CO2 production, the reference sample cellulose had reached a biodegradation percentage of 84.2%. The biodegradation of the tested microcapsules proceeded with an average absolute biodegradation of 82.4% having been measured. On a relative basis, compared to cellulose, a biodegradation of 98.0% was calculated for the tested microcapsules. The 90% biodegradability requirement stipulated in the ISO-14851 standard was therefore met.
The results show that the plant-based protein hydrogel shell of the microcapsules of the present invention easily achieves the biodegradability requirements under fresh water conditions for microplastics, as stipulated by ISO-14851. Accordingly, the microcapsules of the present invention represent environmentally-friendly encapsulation technology, which is particularly suited to use in home care and personal care applications, as if the microcapsules ultimately end up in waterways/the sea they will fully biodegrade in a short amount of time.
Capsule Shell FTIR Analysis:
Structural analysis was also performed on the dried empty microcapsules. Structural analysis was performed using an FTIR-Equinox 55 spectrometer (Bruker). The samples were used without further pre-treatment and were loaded into the FTIR holder. The atmospheric compensation spectrum was subtracted from the original FTIR spectra and a secondary derivative was applied for further analysis. Each FTIR measurement was repeated 3 times. The sensitivity of the instrument was detected to be 5%. To resolve the transformation of the native structure of Pea Protein Isolate into supramolecular aggregates, vibrational changes in amide I, which is strictly correlated with protein secondary structure, were followed.
The results are shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 20195386.6 | Sep 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/074794 | 9/9/2021 | WO |
