Patent Application
20230074344
The present invention relates to a process for the manufacturing of a fermented dairy product, e.g., yogurt or yogurt beverage, substitute, or a homogenized emulsion for the preparation thereof.
Yogurt is a cultured dairy product generated by fermentation of milk inoculated with lactic acid bacteria (LAB) to form a 3D protein network. Protein content in dairy based yogurt usually range from 4-10% making it a contributing source to the daily protein consumption. In addition, yogurt is considered as a major health promoting probiotic product.
The demand for alternatives to milk-based yogurt, i.e., yogurt substitutes, is increasing due to both allergic and intolerance responses to milk components, and the rich scientific data regarding improved health for consumers of vegetarian and vegan diets. Yet, plant-based dispersions often suffer from techno-functional limitations such as poor aqueous solubility, anti-nutritional components, off-flavor, color, physical instability, etc., limiting the utilization of most plant-based sources for the development of yogurt alternatives.
Currently, there is a very limited number of industrial plant-based yogurt substitutes. Usually, they are either based on soy protein, which is a known allergen, or utilize stabilizers such as starch, gums, and carrageenan. In many cases, the protein content of existing non-dairy products is generally lower than in dairy analogues, and in some cases is minimal (e.g., in most milk-like products currently available, i.e., almond-, oat-, and even soy-based products, the protein content is near zero).
In one aspect, the present invention relates to a process for the manufacturing of a fermented dairy product substitute, or a homogenized emulsion for the preparation thereof by fermentation, said process comprising:
provided that a sugar is added either to the aqueous solution or dispersion obtained in step (ii) prior to step (iii), or in addition to said oil added in step (iv).
The high-pressure homogenized emulsion obtained by the process disclosed above (herein also referred to as “the partial process”) may be used for the preparation of a fermented dairy product substitute, starting by inoculating said emulsion with fermentative bacteria, a lactose fermenting yeast, or fungi of the genus Saccharomyces; and fermenting the inoculated emulsion. Particular such fermented dairy product substitutes include, e.g., sour milk-, sour cream-, yogurt-, hard or semi-hard cheese-, kefir-, butter milk-, and ice cream-substitutes. For example, the homogenized emulsion may be used for the preparation of a yogurt- or yogurt beverage-substitute, by inoculating with lactic acid bacteria and fermenting the inoculated emulsion.
Thus, in a particular such aspect, the process disclosed above is for the manufacturing of a yogurt- or yogurt-beverage-substitute, and further comprises the steps of (vi) inoculating the high-pressure homogenized emulsion obtained in step (v) with a lactic acid bacteria; and (vii) fermenting the inoculated high-pressure homogenized emulsion to obtain said yogurt- or yogurt beverage-substitute. In other words, further disclosed herein is a process for the manufacturing of a yogurt- or yogurt beverage-substitute (herein also referred to as “the full process”), said process comprising:
provided that a sugar is added either to the aqueous solution or dispersion obtained in step (ii) prior to step (iii), or in addition to said oil added in step (iv).
In another aspect, the present invention provides a homogenized emulsion for the manufacturing of a fermented dairy product substitute, obtained by the partial process disclosed herein. Particular such emulsions are based on a potato, pea, lupine, chick-pea, rice, algae, lentil, rapeseed, sunflower, hemp, soy, or sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof, wherein the concentration of said protein in said emulsion is below, equal, or higher than 3%, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% (w/w); and/or the concentration of said oil in said emulsion is below, equal, or higher than 5%, e.g., about 5%, 6%, 7%, 8%, 9%, or 10% (w/w).
In a further aspect, the present invention provides a fermented dairy product substitute, obtained by, first, inoculating a homogenized emulsion as disclosed herein with fermentative bacteria, a lactose fermenting yeast, or fungi of the genus Saccharomyces, and fermenting the inoculated emulsion. Examples of such fermented dairy product substitutes include local and traditional sour milk-, sour cream-, yogurt-, hard or semi-hard cheese-, kefir-, butter milk-, and ice cream-substitutes.
In a particular such aspect, the invention provides a yogurt- or yogurt beverage-substitute, obtained by the full process disclosed herein. Particular such yogurt- or yogurt beverage-substitutes are based on a potato, pea, lupine, chick-pea, rice, algae, lentil, rapeseed, sunflower, hemp, soy, or sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof, wherein the concentration of said protein in said yogurt- or yogurt beverage-substitute is below, equal, or higher than 3%, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% (w/w); and/or the concentration of said oil in said yogurt- or yogurt beverage-substitute is below, equal, or higher than 5%, e.g., about 5%, 6%, 7%, 8%, 9%, or 10% (w/w). The yogurt- or yogurt beverage-substitutes provided may have a pH in a range of 3.7-4.5, and/or a concentration of at least 5×107-5×109 (e.g., at least 108) colony forming units of said lactic acid bacteria per gram.
The process disclosed herein enables the preparation of fermented dairy product substitutes, e.g., yogurt- or yogurt beverage substitutes, having high-protein content, more specifically a protein content of up to about 10%. In yet another aspect, the present invention thus provides a fermented plant protein-based dairy product substitute, more specifically a yogurt- or yogurt beverage substitute, comprising a non-soy plant protein at a concentration of from about 3% to about 10% (w/w), wherein said yogurt- or yogurt beverage substitute is free of (i) an additive selected from a stabilizer, emulsifier, and thickener; and (ii) an oil, fat or fat alternative having a melting temperature higher than 10° C., and wherein the ratio between carbohydrates excluding sugars, i.e., mono- and di-saccharides, and protein in said yogurt- or yogurt beverage substitute is not higher than 1:1, respectively, by weight. Particular such products are based on a potato, pea, lupine, chick-pea, rice, algae, lentil, rapeseed, sunflower, hemp, or sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof, wherein the concentration of said protein in said yogurt- or yogurt beverage substitute is about 3% or more, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% (w/w); and/or the concentration of oil in said yogurt- or yogurt beverage substitute is below, equal, or higher than 5%, e.g., about 5%, 6%, 7%, 8%, 9%, or 10% (w/w). More particular such products are potato protein-based yogurt- or yogurt beverage-substitutes.
Plant based proteins are usually physically unstable, i.e., sediment with time. Some industrially developed proteins concentrates/isolates such as potato protein isolates show better stability; yet they still do not show full solubility and stability at high concentrations. In addition, their color is usually grey and non-attractive. The fermentation required to produce yogurt is time consuming (˜6 hours or more). If during this time the instability phenomena governs, the oil phase will separate and/or particles will sediment. Otherwise, if sufficient stability is provided to allow the yogurt matrix to form by the microorganisms, the gel matrix itself will provide further support against phase separation.
(Ultra) high-pressure homogenization ((U)HPH) is a non-thermal continuous technology that may provide, in a single process, the advantages of both homogenization and pasteurization, retain microbial safety, form and stabilize emulsions, and directly and indirectly improve some nutritional aspects of processed liquid foods during shelf life. (U)HPH allows reaching homogenization at pressures of up to 400 megapascal (MPa), wherein pressures below 200 MPa are considered HPH, and pressures of 200 MPa or above are considered UHPH. During (U)HPH processing, a linear temperature increase ranging from 16.6-19.5° C. per 100 MPa occurs with the increase in pressure. In addition to the effects of (U)HPH on the homogenized solution, the structural changes in the emulsion can also result in a modification of the fermented product obtained downstream in the process. For example, homogenization of milk at 75 MPa prior to inoculation was reported to increase the viscosity index and gel firmness of bovine milk yogurt due to changes in the binding between the denatured whey proteins with water and fat globules, and changes between casein-casein and casein-fat interactions (Massoud et al., 2016). Functional properties of proteins, such as solubility, gelation, emulsification, foaming binding, coagulation, and water holding capacity, can be affected by (U)HPH. During (U)HPH, protein molecules experience not only high pressure but also the combined force-induced phenomena of cavitation, shear, turbulence, and temperature rise simultaneously over a short period of time (Bouaouina et al., 2006). A former study reported that (U)HPH, up to 300 MPa, improved the foaming properties of whey proteins as a result of the dissociation of large aggregates, and the foaming capacity of bovine serum albumin due to protein conformational changes. Another study, which examined the effect of (U)HPH on soybean globulins, reported that the treatment led to unfolding and aggregation and suggested that there might be an optimal treatment pressure around 150-200 MPa for which emulsifying properties of the proteins are enhanced (Bouaouina et al., 2006). To the best of our knowledge, few studies examined the utilization and the influence of (U)HPH on the production of yogurt substitutes from different plant-based sources such as oat, soy, coconut, cashew, almond, hemp, lupine, pea, and quinoa (Brückner-Gühmann et al., 2019; Cruz et al., 2009; Ferragut et al., 2009; Grasso et al., 2020; Grobben et al., 1997; Hickisch et al., 2016; Klost and Drusch, 2019; Lorusso et al., 2018; Mårtensson et al., 2000; Zannini et al., 2018), but none of them studied the utilization and influence of (U)HPH on yogurt substitutes made from novel plant-based protein isolates in general, and potato protein isolates in particular.
The utilization of high-pressure homogenization (HPH) together with plant proteins isolates/concentrates allows to provide a sufficiently stable emulsion for the formation of plant-based yogurts. In addition, both the emulsification and the fermentation processes provide a “whiter” color more similar to the color of regular dairy-based yogurt.
In the studies described herein, HPH was used to form a potato protein isolate (PPI) fermented yogurt substitute by lactic acid bacteria fermentation, while examining the influence of this treatment on both the PPI emulsions' and gels' characteristics and physical properties. As found, the HPH strongly affected the particle size distribution (PSD) of the emulsion, and surprisingly, by subjecting the PPI solution to a pre-processing HPH step an improved PPI solubility was achieved. The increase in homogenization pressure resulted in a reduction in the particle size, and the formation of finer and whiter emulsion with minimal sedimentation; and improved the physical stability against separation. As a direct result, the formed emulsions and gels showed more physical stability against phase separation. The PPI yogurt substitutes were received at the same time frame as milk yogurt; and had a gel-like behavior indicating that at all the examined pressures, the storage modulus (G′) was higher than the loss modulus (G″), and a lightness value similar to those reported for commercially available plant-based yogurt substitutes. HPH can therefore be used to obtain plant-based, e.g., PPI-based, yogurt- and yogurt beverage-substitutes with improved physical properties.
High-pressure homogenized emulsions based on pea protein isolates were prepared as well and showed physical properties similar to those of the PPI-based emulsions.
In one aspect, the present invention thus relates to a process for the manufacturing of a fermented dairy product substitute, or a homogenized emulsion for the preparation thereof by fermentation, said process comprising:
provided that a sugar is added either to the aqueous solution or dispersion obtained in step (ii) prior to step (iii), or in addition to said oil added in step (iv).
The term “plant protein concentrate/isolate” as used herein refers to any plant-based protein concentrate/isolate, or a partial hydrolysate thereof, either commercially available or obtained by a process based on extraction of said protein from a fresh or dry plant material, utilizing any procedure and/or technique known in the art, and optionally hydrolyzation thereof. Non-limiting examples of commercially available plant protein concentrates/isolates include potato protein concentrate/isolate, pea protein isolate, hemp protein isolate, and faba protein concentrate.
The process disclosed herein requires that the plant protein concentrate/isolate utilized is water-soluble; yet it may be not fully water-soluble, i.e., partially soluble. The term “soluble- or partially soluble-plant protein concentrate/isolate” as used herein thus refers to a plant protein concentrate/isolate as defined above, which upon dissolving or dispersing in water to form a solution or dispersion containing about 3% (w/w) of said protein concentrate/isolate, and centrifuging the solution or dispersion thus obtained at about 12,000 g for about 15 min at room temperature (e.g., 25° C.), not more than 40% of said protein concentrate/isolate aggregates.
Potato, Solanum tuberosum, is one of the broadest food crops in the world, and besides direct use as food, it is used to produce potato starch. Potato protein is extracted from the byproduct potato juice after removal of the potato starch, and generally considered as GRAS (safe food ingredients) and non-allergenic protein (U.S. FDA, 2013). Potato protein contains high levels of the essential amino acids lysine, threonine, methionine, and tryptophan (Waglay and Karboune, 2016), and was therefore suggested as nutritionally equivalent to the egg white protein, lysozyme. Yet, according to other publications, its true digestibility is slightly lower compared to that of both whey and soy proteins.
Potato proteins are often classified into three main groups: patatin, protease inhibitors, and high-molecular-weight proteins. Patatin, constituting about 40% of the soluble protein in the tuber, is a family of glycoproteins having a molecular weight of 40-45 kDa and a suggested isoelectric point at 5.25 or pH=4.9. Patatin exists in a solution as a dimer and tends to coagulate by heat. Protease inhibitors are a more heterogeneous group of proteins constituting 30-40% of the total soluble protein in the tuber, and having a molecular weight of 5-25 kDa, which tend to be more hydrophilic compared to patatin and to coagulate by heat. According to the literature, potato proteins have antimicrobial and antioxidant properties, as well as lower allergenicity compared to proteins from other sources. In addition, potato proteins were suggested to have several techno-functional properties such as emulsification, foaming, and gelation attributes, which may improve and broaden their utilization in the food industry.
In certain embodiments, the plant protein concentrate/isolate provided in step (i) is a potato protein concentrate/isolate (e.g., Solanic®200), pea protein concentrate/isolate, lupine protein concentrate/isolate, chick-pea protein concentrate/isolate, rice protein concentrate/isolate, algae protein concentrate/isolate, lentil protein concentrate/isolate, rapeseed protein concentrate/isolate, sunflower protein concentrate/isolate, hemp protein concentrate/isolate, soy protein concentrate/isolate, sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof. In particular embodiments, the plant protein concentrate/isolate is a potato protein concentrate/isolate such as such Solanic 200 (Avebe, Veendam, the Netherlands), a pea protein concentrate/isolate, or a partial hydrolysate thereof.
Aqueous solutions or dispersions of plant protein concentrates/isolates can be prepared by any suitable technique known in the art, e.g., by dissolving or dispersing the plant protein concentrate/isolate in water, e.g., distilled- or double distilled water.
In certain embodiments, the amount of the plant protein concentrate/isolate in the aqueous solution or dispersion prepared in step (ii) is determined such that the concentration of said plant protein in the homogenized emulsion prepared, and consequently in the dairy product substitute prepared from said homogenized emulsion, is below, equal, or higher than 3% (w/w). In particular embodiments, the amount of the plant protein concentrate/isolate in said aqueous solution or dispersion is determined such that the concentration of said plant protein in the homogenized emulsion, and consequently in the dairy product substitute, is about 3% (w/w) or more, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% (w/w), or more. Since the homogenized emulsion is prepared from a water solution or dispersion, the plant protein concentration in said homogenized emulsion (and in certain cases also in the dairy product substitute prepared from said emulsion, e.g., wherein the dairy product substitute is a yogurt- or yogurt beverage-substitute), when presented as weight/volume (w/v), would be similar.
In certain embodiments, the oil added in step (iv) is a vegetarian oil, i.e., oil extracted from seeds or other parts of fruits. Examples of vegetarian oils include, without being limited to, palm oil, coconut oil, canola oil, soybean oil, sunflower oil, olive oil, rapeseed oil, cottonseed oil, sesame oil, avocado oil, as well as any combination/mixture thereof. As shown herein, the utilization of HPH allowed the production of a stabilizer-free and non-allergenic PPI yogurt substitute with higher protein content, having low (1.5%), medium (3%) and high (10%) oil concentrations. Thus, in certain embodiments, the amount of the oil added to the high-pressure homogenized solution or dispersion in step (iv) is determined such that the concentration of said oil in the homogenized emulsion prepared, and consequently in the dairy product substitute prepared from said homogenized emulsion, is below, equal, or higher than 5% (w/w). In particular embodiments, the amount of oil added is determined such that the concentration of said oil in the homogenized emulsion, and consequently in the dairy product substitute, is about 5% (w/w) or more, e.g., about 5%, 6%, 7%, 8%, 9%, 10% (w/w), or more.
In certain embodiments, the sugar added during the process of the invention, either to the aqueous solution or dispersion obtained in step (ii) prior to step (iii), or in addition to the oil added in step (iv), is a carbohydrate allowing fermentation by fermentative bacteria, e.g., lactic acid fermentation by lactic acid bacteria.
The term “carbohydrate” refers to a molecule consisting of carbon, hydrogen and oxygen atoms, usually with a hydrogen-oxygen atom ratio of 2:1, which can be cyclic or linear, saturated or unsaturated, and substituted or unsubstituted. As used herein, this term particularly refers to a monosaccharide such as fructose, galactose, glucose, D-mannose, and sorbose; or a disaccharide such as sucrose, maltose, lactose, trehalose, and cellobiose. In particular embodiments, the sugar added during the process of the invention is a monosaccharide such as glucose or fructose, or a mixture thereof.
In certain embodiments, the process of the invention is carried out such that the sugar is added to the aqueous solution or dispersion obtained in step (ii) prior to step (iii). In other embodiments, the sugar is added to the high-pressure homogenized solution or dispersion in step (iv), together with said oil, before forming the emulsion.
The sugar added to the process of the present invention is aimed at allowing fermentation of the high-pressure homogenized emulsion obtained in step (v) by fermentative bacteria, after inoculating said emulsion with said bacteria, e.g., lactic acid fermentation of said homogenized emulsion. The amount of sugar added during the process of the invention is thus calculated taking into consideration, at least, the volume of the homogenized emulsion prepared and the desired concentration of said fermentative (e.g., lactic acid) bacteria in the final product (e.g., yogurt- or yogurt beverage-substitute) prepared. Yet, it should be understood that the amount of sugar added might be higher than that required for a sufficient and complete fermentation process, so as to obtain a sweetened final product, e.g., a yogurt- or yogurt beverage-substitute containing a desired concentration of sugar.
Alternatively, to obtain a sweetened final product, one or more artificial sweeteners, i.e., sugar substitutes, may be added (in addition to the sugar required for the fermentation process), either to the aqueous solution or dispersion obtained in step (ii) prior to step (iii), or together with said oil in step (iv).
Similarly, the high-pressure homogenized emulsion obtained in step (v), and consequently the dairy product substitute prepared by fermentation of said emulsion, may be enriched with one or more probiotics, and/or health promoting compounds.
The term “probiotics” as used herein refers to live microorganisms, e.g., Lactobacillus such as Lactobacillus acidophilus and Lactobacillus casei, and Bifidobacterium such as Bifidobacterium bifidum, B. longum, B. infantis, and B. breve, which when administered in adequate amounts confer a health benefit on the host, generally by improving or restoring the gut flora. According to the present invention, such probiotics may be added to the high-pressure homogenized emulsion obtained in step (v) in addition to the Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophiles commonly used for yogurt production.
The term “health promoting compound” as used herein refers to a compound/component having one or more health promoting action affecting human health (Brandt et al., 2004), i.e., reported to be able to either maintaining or promoting the health and wellbeing, in accordance with the WHO definition of wellbeing that goes beyond the absence of a disease. Examples of health promoting compounds include, without limiting, prebiotic compounds, colorants, betalains, antioxidants, carotenoids, lipophilic vitamins, and polyphenols.
The term “prebiotic compound” as used herein refers to a compound capable of inducing the growth or activity of beneficial microorganisms such as bacteria and fungi, and may thus be added to food so as to alter the composition of microorganisms in the gut microbiome. Dietary prebiotics are typically non-digestible carbohydrates such as oligo- or polysaccharides, or sugar alcohols, which are not degraded or absorbed in the upper digestive tract, and stimulate the growth or activity of advantageous bacteria that colonize the large bowel by acting as substrate for them. Known prebiotics include β-glucans (β-D-glucose polysaccharides), β-fructans (polymers of fructose molecules), e.g., fructooligosaccharides and inulin, galactans (polysaccharides consisting of polymerized galactose) including galacto-oligosaccharides, soluble and insoluble fiber.
In order to enrich the high-pressure homogenized emulsion obtained in step (v) with one or more probiotic, or health promoting compounds, said probiotic(s), or health promoting compound(s) may be added during the process in parallel to said sugar and optionally said sugar substitute(s), i.e., to the aqueous solution obtained in step (ii) prior to step (iii), or together with said oil in step (iv).
In order to nutritionally enrich the high-pressure homogenized emulsion or the dairy product substitute, or to improve the techno-functional properties (like color, texture etc.) thereof, small lipophilic or hydrophilic compounds may be added before emulsification to the oil (lipophilic) or to the protein-sugar aqueous solution (hydrophilic). Such lipophilic compounds may include, e.g., lipophilic vitamins such Vitamin E, lipophilic antioxidants such as carotenoids, lipophilic polyphenolic compounds such as flavonoids, fatty acids, extracts, etc. Examples of hydrophilic compounds include, without limiting, vitamins such as vitamins belonging to B group, hydrophilic polyphenols such as anthocyanins, betalains, and minerals.
In certain embodiments, homogenization of the plant protein concentrate/isolate-containing solution or dispersion in step (iii) is carried out under a high-ultra high pressure in the range of about 50 MPa to about 400 MPa, e.g., under a pressure of about 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 275, or 400 MPa. Alternatively, and as found in accordance with the present invention, the pressure utilized in this step may be lower than 50 MPa, e.g., about 15, 30 or 45 MPa, provided that more than one, e.g., 2, 3, 4 or more, cycles of homogenization under said pressure are performed.
In order to minimize protein sedimentation during emulsification of the aqueous solution or dispersion prepared in step (ii) and increase the content of the plant protein capable of emulsifying an oil, i.e., maximize the solubility and emulsification capacity of the specific plant protein concentrate/isolate used, high-pressure homogenization of said aqueous solution or dispersion is carried out in step (iii) such that the temperature developed in the solution or dispersion during the high-pressure homogenization process is lower, e.g., by about 5° C. or more, than the temperature at which thermal aggregation of said protein concentrate/isolate in said solution or dispersion, under normal pressure, i.e., atmospheric, conditions occurs. In this respect, it should be noted that the temperature developed in the solution or dispersion during the high-pressure homogenization process depends on both the inlet temperature, i.e., the temperature of the solution or dispersion entering the process, and the pressure utilized, wherein a linear temperature increase of 16.6-19.5° C. per 100 MPa occurs with the increase in pressure. For example, in case the inlet temperature is 20° C. and a pressure of 200 MPa is utilized, the temperature developed during the process is approximately 20+2×(16.6-19.5°) C., i.e., 55.2-59° C., and such conditions will therefore be relevant only if said calculated temperature is lower than the temperature at which thermal aggregation of said protein concentrate/isolate in said solution or dispersion, when no pressure is utilized, occurs. Furthermore, it should be noted that different protein concentrates/isolates of the same plant might have different solubility and may thus require different inlet temperature and pressure conditions.
The high-pressure homogenization of the emulsion performed in step (v) is aimed at preventing oil separation (i.e., separation of the oil added in the preceding step) during fermentation, e.g., lactic acid fermentation, of the homogenized emulsion thus obtained, thereby increasing the physical stability of the dairy product substitute, e.g., yogurt- or yogurt beverage-substitute, resulting from said fermentation, or during storage of said homogenized emulsion.
In certain embodiments, homogenization of the emulsion in step (v) is carried out under a high-ultra high pressure in the range of about 50 MPa to about 400 MPa, e.g., under a pressure of about 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 275, or 400 MPa. Alternatively, and as found in accordance with the present invention, the pressure utilized in this step may be lower than 50 MPa, e.g., about 15, 30 or 45 MPa, provided that more than one, e.g., 2, 3, 4 or more, cycles of homogenization under said pressure are performed.
In certain embodiments, the addition of oil to the high-pressure homogenized solution or dispersion (while homogenizing the mixture) to form an emulsion, and the high-pressure homogenization of said emulsion, i.e., steps (iv) and (v) of the process disclosed herein, are carried out as a single step.
The high-pressure homogenized emulsion obtained by the partial process disclosed herein, according to any one of the embodiments above, may be stored, e.g., under refrigerated or freezing conditions, and sold (optionally along with a starter culture); or may be used for the preparation of a fermented dairy product substitute, starting by inoculating said emulsion with fermentative bacteria and fermenting the inoculated emulsion. For example, the homogenized emulsion may be used for the preparation of a yogurt- or yogurt beverage-substitute, by inoculating with lactic acid bacteria and fermenting the inoculated emulsion.
Thus, in one particular such aspect, the process of the invention is for the manufacturing of a yogurt- or yogurt-beverage-substitute, and further comprises the steps of (vi) inoculating the high-pressure homogenized emulsion with a lactic acid bacteria; and (vii) fermenting the inoculated high-pressure homogenized emulsion to obtain said yogurt- or yogurt beverage-substitute. In other words, further disclosed herein is a full process for the manufacturing of a yogurt- or yogurt beverage-substitute, which comprises:
provided that a sugar is added either to the aqueous solution or dispersion obtained in step (ii) prior to step (iii), or in addition to said oil added in step (iv).
As described above, yogurt- or yogurt-beverage-substitutes manufactured according to the process disclosed hereinabove may have oil concentration that is below, equal, or higher than 5% (w/w), e.g., about 5%, 6%, 7%, 8%, 9%, 10% (w/w), or more.
The term “lactic acid bacteria” (LAB) refers to an order of gram-positive, low G+C, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and milk products, produce lactic acid as the major metabolic product of carbohydrate fermentation. The genera that comprise the LAB are at its core Lactobacillus such as L. acidophilus and L. casei, Bifidobacterium such as B. bifidum, B. longum, B. infantis, and B. breve, Leuconostoc, Pediococcus, Lactococcus, and Streptococcus, as well as the more peripheral Aerococcus, Carnobacterium, Enterococcus, Oenococcus, Sporolactobacillus, Tetragenococcus, Vagococcus, and Weissella. In a particular embodiment, the LAB used in the process disclosed herein is a mixture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus.
In certain embodiments, the high-pressure homogenized emulsion obtained in step (v) is inoculated in step (vi) with said lactic acid bacteria to obtain a final concentration of 105-107, e.g., about 106 or more, colony forming units of said lactic acid bacteria per gram of said emulsion.
In certain embodiments, and in order to enrich the high-pressure homogenized emulsion obtained in step (v) with one or more probiotics and/or health promoting compounds, one or more probiotics or health promoting compounds, each as defined above, is added to the emulsion together with said lactic acid bacteria.
In certain embodiments, the inoculated high-pressure homogenized emulsion is fermented in step (vii) until a final pH in a range of 3.7-4.5, and/or a final concentration of at least 5×107-5×109, e.g., at least 108, colony forming units of said lactic acid bacteria per gram of emulsion, are obtained.
In certain embodiments, the inoculated high-pressure homogenized emulsion is fermented in step (vii) at a temperature, or temperature range, compatible with said lactic acid bacteria, i.e., optimal for the growth and reproduction of said bacteria. Yet, in other embodiments, and depending on the specific protein concentrate/isolate provided and/or features of the final product desired, said emulsion is fermented at a temperature, or temperature range, that is lower or higher, but preferably lower, than that compatible with said lactic acid bacteria. For example, in the process exemplified herein, a potato protein isolate and standard thermophilic lactic acid bacteria were used; however, the fermentation was carried out at 37° C. rather than at 40-45° C. that is the temperature compatible with said bacteria, because as observed, at a temperature higher than 37° C., the thermal gelation of said isolate is faster than the gelation due to fermentation, leading to a non-typical acid formation.
In particular embodiments, disclosed herein is a full process as defined above, for the manufacturing of a yogurt- or yogurt beverage-substitute, wherein said plant protein concentrate/isolate is a potato protein concentrate/isolate, a pea protein concentrate/isolate, or a partial hydrolysate thereof; said aqueous solution or dispersion is prepared in step (ii) by dissolving or dispersing said protein concentrate/isolate in water in an amount such that the concentration of said protein in said dairy product-substitute or said homogenized emulsion is below, equal, or higher than 3% (w/w); said high-pressure homogenizing in step (iii) is carried out at an inlet temperature in a range of 10-25° C., e.g., at an inlet temperature of about 15° C. and under pressure of about 75, 100, 125, 150, 175, or 200 MPa; and the vegetarian oil added in step (iv) is canola oil. In more particular such embodiments, lactic acid fermentation of the homogenized emulsion obtained, after inoculating with lactic acid bacteria, is carried out at a temperature of about 37° C.
In another particular such aspect, the process of the invention is for the manufacturing of a local or traditional sour milk-, sour cream-, yogurt-, hard or semi-hard cheese-, kefir-, butter milk-, or ice cream-substitute, or an intermediate product for the preparation thereof, and further comprises the steps of: (vi) inoculating the high-pressure homogenized emulsion with a bacteria selected from Lactobacillus, Leuconostoc, Pediococcus, Propionibacterium, Streptococcus, Bifidobacterium, or Acetobacter; a lactose fermenting yeast; or a fungi of the genus Saccharomyces; and (vii) fermenting the inoculated high-pressure homogenized emulsion to obtain said local or traditional sour milk-, sour cream-, yogurt-, hard or semi-hard cheese-, kefir-, butter milk-, or ice cream-substitute, or said intermediate product for the preparation thereof. In certain embodiments, the inoculated high-pressure homogenized emulsion is fermented in step (vii) at a temperature, or temperature range, compatible with, i.e., optimal for the growth and reproduction of, said bacteria, lower than that compatible with said bacteria, or higher than that compatible with said bacteria.
In certain embodiments, the product manufactured by the process disclosed hereinabove is the dairy product substitute desired, e.g., a sour milk, while in other embodiments, the product manufactured is, in fact, an intermediate product from which the desired dairy product substitute may be prepared after additional steps known in the art including, e.g., further fermentation, pasteurizing, sterilizing, mixing/blending, renneting, centrifuging, pressing, curding, ripening, drying, etc.
In another aspect, the present invention provides a homogenized emulsion for the manufacturing of a fermented dairy product substitute, obtained by the partial process disclosed herein according to any one of the embodiments above. Particular such emulsions are based on a potato, pea, lupine, chick-pea, rice, algae, lentil, rapeseed, sunflower, hemp, soy, or sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof, wherein the concentration of said protein is below, equal, or higher than 3%, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% (w/w), or more; and/or the concentration of said oil is equal to or higher than 5% (w/w).
In a further aspect, the present invention provides a fermented dairy product substitute, obtained by, first, inoculating a homogenized emulsion as disclosed herein with fermentative bacteria, and then fermenting the inoculated emulsion.
In one particular such aspect, the present invention provides a yogurt- or yogurt beverage-substitute, obtained by the full process disclosed herein according to any one of the embodiments above. Particular such yogurt- or yogurt beverage-substitutes are based on a potato, pea, lupine, chick-pea, rice, algae, lentil, rapeseed, sunflower, hemp, soy, or sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof, wherein the concentration of said protein is below, equal, or higher than 3%, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% (w/w); and/or the concentration of said oil is equal to or higher than 5% (w/w). Such yogurt- or yogurt beverage-substitutes may have a pH in a range of 3.7-4.5, and/or a concentration of at least 5×107-5×109 (e.g., at least 108) colony forming units of said lactic acid bacteria per gram.
In another particular such aspect, the present invention provides a fermented dairy product substitute, obtained by, first, inoculating a homogenized emulsion as disclosed herein with a lactose fermenting yeast, or fungi of the genus Saccharomyces, and then fermenting the inoculated emulsion. Examples of such fermented dairy product substitutes include sour milk-, sour cream-, hard or semi-hard cheese-, kefir-, butter milk-, and ice cream-substitutes. Particular such dairy product substitutes are based on a potato, pea, lupine, chick-pea, rice, algae, lentil, rapeseed, sunflower, hemp, soy, or sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof, wherein the concentration of said protein is below, equal, or higher than 3%, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% (w/w); and/or the concentration of said oil is equal to or higher than 5% (w/w).
The process of the present invention, starting from a soluble- or partially soluble-plant protein concentrate/isolate in a dried form, and utilizing high-pressure homogenization of both the protein solution prior to emulsification and the emulsion formed after the addition of an oil to said high-pressure homogenized solution, enables the preparation of fermented dairy product substitutes, e.g., yogurt- or yogurt beverage substitutes, having high-protein content, more specifically a protein content of up to about 10%.
In yet another aspect, the present invention thus provides a fermented plant protein-based dairy product substitute, more specifically a yogurt- or yogurt beverage substitute, comprising a non-soy plant protein at a concentration of from about 3% to about 10% (w/w), e.g., at a concentration of about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% (w/w), wherein said yogurt- or yogurt beverage substitute is free of (i) an additive selected from a stabilizer, emulsifier, and thickener; and (ii) an oil, fat or fat alternative having a melting temperature higher than 10° C., and wherein the ratio between carbohydrates excluding sugars, i.e., mono- and di-saccharides, and protein in said yogurt- or yogurt beverage substitute is not higher than 1:1, respectively, by weight. Particular such products are based on a potato, pea, lupine, chick-pea, rice, algae, lentil, rapeseed, sunflower, hemp, or sesame protein concentrate/isolate, a partial hydrolysate thereof, or a combination thereof, wherein the concentration of said protein in said dairy product substitute is about 3% or more, e.g., about 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% (w/w); and/or the concentration of oil in said dairy product substitute is equal to or higher than 5% (w/w). More particular such yogurt- or yogurt beverage substitutes are potato protein-based yogurt- or yogurt beverage-substitutes. Particular such yogurt- or yogurt beverage-substitutes have a pH in a range of 3.7-4.5, and/or a concentration of at least 5×107-5×109 (e.g., at least 108) colony forming units of lactic acid bacteria per gram.
In sharp contrast to yogurt- or yogurt beverage substitutes currently available or disclosed in the art, wherein the physical structure of the product results, at least in part, from the addition of an additive such as a stabilizer/emulsifier/thickening agent, or an oil, fat or a fat alternative, having a melting temperature higher than 10° C. (i.e., solidifying under refrigerated conditions, e.g., at a temperature of about 2-10° C.); or from a very high fibers and/or starch content, i.e., wherein the weight ratio between the protein and the overall carbohydrates excluding sugars in said product is higher than 1:1, respectively, the yogurt- or yogurt beverage substitute of the present invention comprises neither an externally added stabilizer/emulsifier/thickener nor an oil, fat or fat alternative solidifying under refrigerated conditions, and its physical structure results from the protein 3D network only.
The term “additive” as used herein refers to a compound externally added to the product during the process for the preparation thereof, aimed at stabilizing or structuring, i.e., enhancing or promoting gelation of, said product. Such additives are classified by different agencies into several categories including stabilizers, emulsifiers, and thickening agents (thickeners), although most of them may be listed in more than one of these categories.
The term “stabilizer” as used herein refers to a compound capable of controlling, retaining, and intensifying the texture of a food product (Lal, O'Connor, & Eyres, 2006). According to the present invention, the stabilizer is selected from dextrin, roasted starch; acid-treated starch; alkaline-treated starch; bleached starch; oxidized starch; enzyme-treated starch; mono-starch phosphate; di-starch phosphate; starch acetate; phosphated di-starch phosphate; acetylated di-starch phosphate; acetylated oxidized starch; acetylated di-starch adipate; hydroxypropyl di-starch phosphate; hydroxypropyl starch; starch sodium octenyl succinate; alginic acid or a salt thereof such as sodium alginate, potassium alginate, ammonium alginate, and calcium alginate; propane-1,2-diol alginate; propylene glycol alginate; agar; carrageenan; processed eucheuma seaweed; arabinogalactan; locust bean gum; carob gum; guar gum; tragacanth; tragacanth gum; acacia gum; gum Arabic; xanthan gum; karaya gum; tara gum; gellan gum; gum ghatti; sorbitol; sorbitol syrup; curdlan; konjac flour; polyoxyethylene sorbitan monolaurate, polysorbate 20; polyoxyethylene sorbitan mono-oleate, polysorbate 80; polyoxyethylene sorbitan monostearate, polysorbate 60; olyoxyethylene sorbitan tristearate, polysorbate 65; tamarind seed polysaccharide; pectin; sucrose acetate isobutyrate; glycerol esters of wood rosins; cyclodextrin alpha-; cyclodextrin gamma-; cyclodextrin beta-; cellulose; microcrystalline cellulose (cellulose gel); powdered cellulose; methyl cellulose; hydroxypropyl cellulose; hydroxypropyl methyl cellulose; ethyl methyl cellulose; carboxy methyl cellulose (cellulose gum); ethyl hydroxyethyl cellulose; crosslinked sodium carboxy methyl cellulose; sodium carboxymethyl cellulose enzymatically hydrolyzed (cellulose gum, enzymatically hydrolyzed); sodium, potassium and calcium salts of fatty acids; magnesium salts of fatty acids; mono- and diglycerides of fatty acids; acetic acid esters of mono- and diglycerides of fatty acids; lactic acid esters of mono- and diglycerides of fatty acids; citric acid esters of mono- and diglycerides of fatty acids; tartaric acid esters of mono- and diglycerides of fatty acids; mono- and diacetyltartaric acid esters of mono- and diglycerides of fatty acids; sucrose esters of fatty acids; polyglycerol esters of fatty acids; sodium stearoyl-2-lactylate; calcium stearoyl-2-lactylate; sorbitan monostearate; sorbitan tristearate; sorbitan monolaurate; and sorbitan monooleate.
The term “emulsifier” as used herein refers to a compound capable of helping products containing immiscible food ingredients (like oil and water) to combine, preventing phase separation, and extending shelf life. According to the present invention, the emulsifier is selected from lecithin; octenyl succinic acid (OSA) modified gum Arabic; cassia gum; polyoxyethylene sorbitan monopalmitate, polysorbate 40; superglycerinated hydrogenated rapeseed oil emulsifier; ammonium phosphatides; sucroglycerides; polyglycerol polyricinoleate; propane-1,2-diol esters of fatty acids; thermally oxidized soya bean oil interacted with mono- and diglycerides of fatty acids; sorbitan monopalmitate; beeswax; and cadelilla wax.
The term “thickening agent” or “thickener” as used herein interchangeably refers to a compound capable of increasing the viscosity of an aqueous preparation such as a food product, without affecting other properties of said preparation. According to the present invention, the thickening agent is selected from starch aluminum octenyl succinate; bakers yeast glycan; oat gum; glycerol; and ethyl cellulose.
Examples of oils that oils having a melting temperature higher than 10° C. include, without being limited to, coconut oil, palm oil, and mixtures thereof. Examples of fat alternatives having a melting temperature higher than 10° C. include, without limiting, oleogels and hydrogenated oil.
The yogurt- or yogurt beverage substitute disclosed herein is further characterized in that the ratio between the carbohydrates excluding sugars, and protein, in said yogurt- or yogurt beverage substitute is not higher than 1:1, respectively, by weight. The term “sugars” as used herein means a mono- or di-saccharide, including glucose, fructose, and galactose, as well as lactose, maltose, cellobiose, and sucrose. The phrase “carbohydrates excluding sugars” as used herein thus in fact refers to the overall fibers (including externally added) and starch present in said yogurt- or yogurt beverage substitute.
Unless otherwise indicated, all numbers expressing, e.g., protein and oil concentrations, lactic acid bacteria concentrations, pressures, and temperatures, used in this specification, are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification are approximations that may vary by up to plus or minus 5% depending upon the desired properties to be obtained by the present invention.
The invention will now be illustrated by the following non-limiting Examples.
Materials. The commercially available potato protein isolate (PPI), Solanic 200 (protein content 90.5%), was purchased from Avebe (Veendam, the Netherlands). D (+)-glucose anhydrous (purity ≥99%) was obtained from Fluka Chemie Gmbh (Buchs, Switzerland). Sunflower oil and ultra-high temperature (UHT) bovine milk were purchased from a local supermarket (Haifa, Israel). Lee's agar was purchased from Himedia Laboratories Pvt. Ltd. (Mumbai, India).
Evaluation of PPI fractions using SDS-PAGE. Qualitative evaluation of the protein fractions of the commercially available PPI was conducted by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). PPI samples were diluted with sample buffer (50% glycerol, 10% SDS, 0.5M tris, 10 mM EDTA, bromophenol blue, and 13% double distilled water (DDW)) and 0.5M DL-dithiothreitol (DTT). Then, the samples were heated for 10 min at 70° C. and centrifuged before loading on the gel (10% acrylamide). The molecular weight of the PPI fractions was evaluated using molecular weight marker, 10 kDa-250 kDa (PageRuler plus pre-stained protein ladder, Thermo Scientific, Lithuania). The running conditions were based on those previously disclosed. The gels were stained with 0.25% Coomassie brilliant blue (R-250) in 50% ethanol, 10% acetic acid and 40% DDW, and then destained in 14% acetic acid [ethanol: acetic acid: DDW, 29:14:57 (v/v/v)].
PPI emulsion preparation. For the pre-processing step, a solution of 5% (w/v) PPI and 5% (w/v) glucose in sterile distilled water (DW) was homogenized at 200 MPa at Tin=15° C. in one cycle using a Stansted high-pressure homogenizer (model FPG 12800, Stansted Fluid Power Ltd., Essex, United Kingdom). After pretreatment, 3% (v/v) sunflower oil was added to the solution, and the emulsion was prepared in two processing steps. First, a coarse emulsion was formed using an Omni general laboratory homogenizer (OMNI International Inc., Waterbury, Conn., USA) operated for 30 s at ˜4,000 RPM, and the fine PPI emulsion was then produced by homogenization at a pressure range of 30-200 MPa at Tin=25° C. in one cycle.
Set type yogurt substitute preparation. The experimental protocol used for the preparation of a set type yogurt substitute is shown in
PPI solubility. The changes in solubility of PPI in the solution after the pre-processing step was estimated based on known methods. 10 ml of 5% (w/v) PPI solutions, with and without the pre-processing step, were centrifugated at 12,000 g for 15 min at 25° C., and the protein content was determined in both the supernatant and the original suspension of the PPI solution by the Bradford dye-binding method (Bradford, 1976; Chang and Zhang, 2017). 200 μl of diluted Bradford reagent in water (HPLC grade) (1:4) was added to 800 μl diluted PPI samples and the absorbance was read at 595 nm. Protein solubility was expressed as the protein content in the supernatant (soluble protein, after centrifugation) divided by the protein content in the original suspension (before centrifugation). Six different samples were measured for each protein solution.
pH measurements during LAB fermentation. The pH value was measured using a pH meter (HI5221, Hanna Instrument Inc., Woonsocket, R.I., USA), a calibrated pH probe designed for semi-solid materials (FC210B, Hanna Instrument Inc.), a temperature compensating probe (HI7662-W, Hanna Instrument Inc.), and HI92000 software (Hanna Instrument Inc.). The measurements of the gels were done in duplicate.
Particle size distribution (PSD). The influence of the homogenization pressure on the PSD and emulsion droplet size of PPI emulsion was measured by static light scattering measurement (Mastersizer 3000, Malvern Instruments, United Kingdom) equipped with a medium volume automated dispersion unit (Malvern Hydro MV, United Kingdom) as described before. The values of particle refractive index of PPI emulsions (based on actual measurements with analog Abbe refractometer (KRUSS, Hamburg, Germany)) and milk, and particle absorption index were 1.46, 1.4, and 0.001, respectively. The dispersant refractive index (water) was 1.330. The background and sample integration times were 20 s and 10 s. Samples were dispersed in DW at 1200 RPM until the obscuration of 6-8% was obtained. Before measuring PPI solutions not treated with the pre-processing step, those solutions were centrifuged at 2500 g for 4 min (Thermo Fisher SL 16R, Thermo Scientific, PA, USA) to separate and remove some of the non-water soluble and high molecular weight particles. All samples were done in duplicate, and each of the repetitions was measured five times.
Lightness measurement. Lightness evaluation of emulsions and gels was carried out according to the CIELAB scale using a Minolta CR-300 chroma meter (Konica Minolta Sensing Americas, NJ, USA) as previously described (Grasso et al., 2020) with some changes. The CIELAB scale enables to determine the L* value (100=white; 0=black), which describes the black-white component (the luminosity) and the lightness of the sample. Samples of milk and PPI emulsions and gels were measured in a 50 ml sterile plastic conical centrifuge tube with a 2.8 cm diameter covered with an aluminum foil. For milk and PPI gels, inoculated solutions were incubated at 37° C. for 16 h, cooled at 4° C. for 24 h, and then L* values were measured. Two different samples were measured for each emulsion and gel type.
Stability against the separation of emulsions and gels. The physical stability of milk and PPI emulsions and gels (yogurts) was evaluated using an analytical centrifugal analyzer (LUMisizer, L.U.M GmbH, Berlin, Germany) This method measures the time and space resolved transmission extinction profile of the analyzed sample under analytical centrifugation and enables qualitative comparison between samples as previously suggested for emulsions, particulate systems and gels. 400 μl of milk and PPI emulsions were loaded onto rectangular polycarbonate cuvettes, and the transmission extinction profile was recorded at 2000 rpm, 20° C. for 11 h. For milk and PPI gels, 400 μl of the inoculated samples were loaded onto rectangular polycarbonate cuvettes, incubated at 37° C. for 16 h, cooled at 4° C. for 24 h, and the transmission extinction profile was then recorded at 2000 rpm, 20° C. for 13 h. All gel and emulsion samples were done in duplicate, and each of the repetitions was loaded onto the LUMisizer in duplicate. The percentage of separation of PPI gels in the cuvettes after the analysis was measured and presented as the relative height of the separation divided by the initial sample height in the cuvettes.
Microbiological analysis. The growth of LAB in the inoculated sample, milk and PPI emulsions, at different homogenization pressure, was evaluated using Lee's agar designed for the enumeration of yogurt starter bacteria as suggested before in pour plate with double layer forming an anaerobic condition. All samples were tested at 0, 3, 6, and 16 h of fermentation. Until seeding, samples were stored at 4° C. For determining colony-forming units (CFU), samples were serially diluted by 0.1% (w/v) peptone solution. Petri dishes were incubated at 30° C. for 24 h. All samples were done in duplicate.
Texture profile analysis (TPA). Texture profile analysis was performed based on accepted practices. 30 ml of inoculated milk and PPI emulsions were loaded onto a 50 ml sterile conical plastic centrifuge tube with a 2.8 cm diameter. After incubation at 37° C. for 16 h, the samples were kept at 4° C. for 24 h before the analysis. The mechanical properties were measured by textile profile analysis using a TA1 texture analyzer (Lloyd Instruments Ltd., AMETEK, Berwyn, Pa. USA) equipped with a 20 mm cylindrical probe. Force distance curves were obtained operating at a constant speed of 30 mm min−1 until 30% of the sample depth was penetrated. The texture profiles of gels were analyzed using NEXYGEN Plus 4.0 data analysis software and the following parameters were obtained from the texture profile: hardness (the peak force in the first compression cycle), cohesiveness (the work area during the second compression divided by the work area during the first compression cycle), and adhesiveness (the work necessary to upstroke the probe from the sample). Six different samples were measured for each gel type.
Rheological properties—frequency sweep analysis. The viscoelastic properties of the gels were studied using a frequency sweep analysis using an MCR 302 rheometer (Anton Paar, Graz, Austria). Frequency sweep measurements were performed at 4° C. and 0.01-10 Hz with a maximum strain of 0.1% using 25 mm sandblasted parallel plate geometry and gap settings of 1 mm Measurements were conducted within the linear viscoelastic range (LVR) determined by a stress sweep test from 0.001 to 1 Pa. 10 ml of inoculated milk and PPI emulsions were poured onto a 5 cm sterile Petri dishes, incubated at 37° C. for 16 h, and cooled at 4° C. for 24 h. Then samples were transferred to the pre-cooled rheometer lower plate (4° C.) using a plastic spatula, the upper plate was lowered, the sample was cooled for 5 min at 4° C., and analysis was then initiated. The storage modulus (G′) and loss modulus (G″) were determined as a function of frequency. All samples were measured in triplicate.
Water holding capacity (WHC). The water holding capacity (WHC) was determined based on methods previously described (Kocher and Foegending, 1993; Serra et al., 2009) with several changes. 500 μl of inoculated PPI emulsion at different homogenization pressure and inoculated milk were loaded on a special centrifuge filter unit composed of a 2 ml micro-centrifugal tube equipped with nylon filter (0.45 μm) (Micro-Centrifugal Filters (F2517-4), Thermo Scientific, USA). All the tubes were incubated at 37° C. for 16 h, and cooled at 4° C. for 24 h. Then, the stored samples were centrifuged at 5000 g for 20 min at 25° C. Centrifuge tubes, filter, gels samples and water loss were weighted (mg), and the WHC (%) was determined based on the following equation:
where W1 is the initial weight of the sample (mg), and W2 is the weight of the pellet after centrifuge (mg). Two replicates were examined for each PPI and milk gel sample.
Statistical analysis. The significance of the influence of (U)HPH on PPI emulsions and gels properties were calculated using a one-way ANOVA test with post-hoc Tukey (Honestly Significant Difference) by Origin 2019 (OriginLAb, USA), with a significance of p<0.05. The significant differences between PPI and milk gels and emulsion were calculated using a t-test (Excel, Microsoft 2016) with a significance of p<0.05.
Potato protein has three main groups of proteins clearly distinguished in their molecular weight: patatin (˜40 kDa), protease inhibitors (5-25 kDa), and high molecular weight proteins. Potato protein fractions of the commercially available PPI were characterized by SDS-PAGE and presented in
In order to investigate the effect of (U)HPH on PPI techno-functional properties, the effect of (U)HPH as a pre-processing step on the protein itself was studied, hypothesizing that a preliminary (U)HPH step applied for the PPI solution before the addition of oil can contribute to stabilization against sedimentation of the protein in the emulsion systems due to improved solubility or dispersibility of the protein. Protein solubility is critical to many protein functional properties such as emulsification and gelation (Yang and Powers, 2016). As previously reported, improving protein solubility and surface hydrophobicity of food derivatives, including protein isolates, could result in improved functionalities by influencing the charge of the proteins, reducing the molecular weight, and improving surface activity by exposure of the hydrophobic domains. In this work, we studied the effect of (U)HPH as a pre-processing step by examining different inlet temperatures (Tin) and homogenization pressures, and the optimal solution is presented—homogenization at 200 MPa and Tin=15° C. PPI solubility with and without the pre-processing step was estimated and expressed as the ratio of the protein content in the supernatant to the protein content in the original suspension (
The formation of emulsions consists of deformation and breakup of liquid droplets, followed by adsorption of surface-active molecules (e.g., proteins), creating a fine colloidal dispersion. Elongation or deformation of droplets is a requisite for breakup since the average diameter of droplets entering the gap is much larger than the gap itself. The newly created emulsion droplets can collide between them due to Brownian motions and hydrodynamic interactions, leading to the formation of larger droplets, coalescence, which is avoided by the addition of stabilizers. HPH has received intense attention as a physical mean for achieving stable suspensions (solid in liquids). Emulsification utilizing HPH is a dynamic process controlled by numerous factors starting with the HPH process itself (homogenization pressure and flow rate, flow conditions, valve design and configuration, geometry, number of passes) and ending with the properties of emulsifying agents, including type and concentration of emulsifiers and stabilizers, viscosity, density, and interfacial properties. The PSD of the PPI emulsions treated with a pre-processing step or not was examined as a function of the homogenization pressure, hypothesizing (based on previous work conducted on soy protein) that the particle size of the PPI emulsions will reduce as homogenization pressure increases (Cruz et al., 2007), and the results are shown in
The color of a food product is an essential sensory attribute affecting the acceptance of the product by the consumers. Although a protein solution is usually of grey/brown color, the application of (U)HPH allowed the formation of whiter colored emulsions due to increased light scattering of the oil droplets. Lightness value, L*, describes the light reflecting or transmitting the capacity of an object. As shown in
Emulsions are thermodynamically unstable and tend to breakdown over time due to various physicochemical mechanisms including Ostwald ripening, coalescence, flocculation, gravitational separation, particle coalescence, and phase separation (i.e., creaming) If the emulsion separates before a yogurt-like structure is formed, poor textural yogurt properties will be received. Thus, their physical stability against separation is an essential parameter indicating the shelf life of emulsions and their separation. One of the methods for testing the physical stability of an emulsion is by analytical centrifugation and based on the time and space-resolved transmission extinction profiles to quantify the phase separation (creaming) velocity of emulsions. As previously reported, creaming tends to be the main destabilization mechanism in plant (such as soy, rice, and oat)-based milk substitutes (Durand et al., 2003; Sethi et al., 2016).
The physical stability of PPI emulsions and milk was measured in an analytical centrifuge (LUMisizer), and the creaming velocity was calculated and shown in
In the present work, we imitate the fermentation process of milk yogurt by inoculating the homogenized PPI emulsions with LAB. As previously reported, the protein content of plants-based yogurt substitutes varies from 0.6 g/100 g to 7.9 g/100 g, wherein the commercial products reported have a protein content of 5.1 g/100 g (Grasso et al., 2020). In this work, we chose to investigate the gels obtained from PPI emulsions with protein content similar to that of the commercial products.
The pH value was monitored during the development of the fermentation for 16 h at 37° C. for inoculated milk, and 200 MPa PPI emulsion (
Moreover, fermentation progress was also monitored by the growth of LAB during the fermentation at 4-time points, and the results are presented in
Gels play an important role in food texture and are formed mostly by proteins, starch, and polysaccharides. Therefore, understanding the rheology and microstructure of food is an important tool for improving consumer satisfaction. The storage modulus G′ represents the elastic behavior of the network and strength of the structure contributing to the 3D network. The loss modulus G″ represents the viscous behavior of a sample (Doucet et al., 2001; Gunasekaran and Ak, 2000; Tabilo-Munizaga and Barbosa-Canvas, 2005). Therefore, if the storage modulus is higher than the loss modulus, the sample can be regarded as a solid-like material such as a gel. The rheological properties of PPI yogurt-like structure obtained from emulsions homogenized at different pressures and milk yogurts were characterized by frequency-dependent dynamic oscillatory measurement, and a typical curve is presented in
The dependence of the storage modulus as a function of frequency can be expressed by the Equation 2 (Arogundade et al., 2012):
G′=K(ω)n or log G′=n log ω+k Equation 2:
where G′ represents the storage modulus, to represents the oscillation frequency, n represents the slop in a log-log plot, and K is a constant. The parameters n and k, providing information regarding the gel structure and its characteristics, can be an additional tool for identifying the difference between physical gels, entanglement networks, and covalently cross-linked gels. The n and k values may represent the nature of the gel network and the strength of the molecular interactions of the tested system, respectively (Arogundade et al., 2012; Gunasekaran and Ak, 2000; Zhang et al., 2017). The k values reflect the levels of molecular interactions in the gel matrix. As k values increase, the molecular interactions are higher. The n and k parameters were calculated based on Equation 2 and are presented in Table 1.
Both milk yogurt and all PPI yogurt-like structures showed a gel-like behavior, indicating that the storage modulus was higher than the loss modulus (not shown) at all frequencies range, i.e., the elastic contribution was more than the viscous thus a gel state can be determined (a gel-like behavior). A reduction in the network strength can be observed in the decrease in G′ and G″ curves (Gabriele et al., 2001). The G′ and G″ curves of PPI curves were higher than those of milk yogurt. This result could imply a reduced network strength in milk gels compared to PPI gels, yet mainly likely originating from the higher content of protein in PPI emulsion, contributing to network structure strength (Tunick, 2000). Gelation process is achieved due to a fine balance between repulsive and attractive forces between proteins both in their native and unfolded forms. Gel formation depends on the formed aggregates—too large or rapidly growing aggregates can result in precipitation or an inhomogeneous structure, while too small or fewer aggregates will not be able to form a 3D network (Creusot et al., 2011). Grygorczyk and Corredig (2013) described the acid gelation of soy proteins by LAB, the driving forces behind acid-induced gelation is the non-covalent bonds such as salt bridging, hydrogen bonding, and Van der Waals forces. During LAB fermentation, the proton gradually neutralized the surface charges until the point that the net charge reaches zero and the soy proteins destabilized, aggregated, and formed a gel network. The rate of acidification has an influence on the protein rearrangement—the slower the pH reduction, the more time for proteins to rearrange and interact with each other (Grygorczyk and Corredig, 2013). It was described that after acidification, soy drink treated with heat treatment favored hydrophobic interactions in the gel network formation while soy drink treated with (U)HPH treatments led to a gel that was stabilized by hydrogen bonds, thus improving gel characteristics in refrigerated conditions (Cruz et al., 2009). Most food gels are considered as physical gels due to their frequency-dependent behavior (Basu et al., 2017; Renard et al., 2006). All the examined gels have an n>0 (Table 1), indicating that the formed gels are physical gels, as previously reported for milk yogurt (Gabriele et al., 2001). K constant values are increasing with the rise in homogenization pressure, wherein the highest K value was obtained for the 200 MPa PPI gel, and the lowest was for milk, indicating that the molecular interactions in PPI gels may be stronger than in milk.
As the formation of yogurt structure requires several hours, if the emulsion separates before the structure is formed, poor textural yogurt properties are received. Emulsions treated with higher (U)HPH pressure will have better stability against gravitational separation and flocculation. Therefore, the utilization of (U)HPH can assist in forming fermented products with no phase separation and yogurt-like consistency, firmness, and WHC. Improvement of textural properties of yogurt by HPH was also previously described for bovine milk yogurt and yogurt alternatives prepared from soy drink treated with (U)HPH (Ferragut et al., 2009; Serra et al., 2007). As described in Example 1, an emulsion with smaller particles and increased physical stability was received as the homogenization pressure increases. Upon fermentation with LAB, a yogurt-like structure was formed.
The effect of utilizing (U)HPH on the physical stability of PPI gels was examined with analytical centrifugation, and the time and space-resolved transmission extinction profiles (Glusac et al., 2018; Glusac et al., 2017; Torres et al., 2014). A typical time and space profiles of PPI gels and milk yogurt during accelerated physical stability study and the percentage of separation of PPI gels in the cuvettes after the analysis are presented in
L* values of the PPI yogurt substitutes and milk yogurt are presented in
The observed L* value of PPI yogurt-like structure was slightly higher than those of PPI emulsions. The decrease in the pH in PPI emulsion could be a possible contributing factor for the changes in the PPI gels' lightness compared to the original emulsions, as reported before, that pH affects the color of protein solutions.
Texture is an important attribute in food acceptance by consumers. A correlation between sensory evaluation to textural parameters obtained from TPA force/deformation curves has been reported and provide additional information to that obtained from rheological measurements (Chandra and Shamasundar, 2015; Pons and Fiszman, 1996). The calculated parameters, hardness, adhesiveness, and cohesiveness obtained by TPA (
Water holding capacity (WHC) is a physical property defined as the ability of a sample/product to prevent water from being released from the three-dimensional structure of said sample/product. In food matrices, it can be defined as the ability of food to hold its own and the added water during the application of forces, pressing, centrifugation, or heating. The WHC of gels, especially yogurt, is a critical parameter since it may imply on the shelf life of a product. WHC is related to syneresis due to the intrinsic properties of the gels, and water may be lost after extended storage (Cruz et al., 2009). The obtained WHC values of PPI gels (excluding 0.1 MPa) were similar to those reported for commercial plant-based yogurts substitutes (Grasso et al., 2020). As shown in
Study 2. Utilization of HPH for Plant-Protein Based Yogurt-Like Products with Different Oil Content
Particle size distribution measurements. Particle size distribution (PSD) of the PPI emulsions was measured by static light scattering measurement (Mastersizer 3000, Malvern Instruments, UK). All samples were prepared in duplicate, and each of the repetitions was measured five times.
Whiteness index evaluation. Color parameters of PPI emulsions and gels were measured using a Minolta chromameter equipped with an 8 mm-diameter measuring area, uses diffuse illumination and 0° viewing angle (CR-300, Konica Minolta Sensing Americas, Ramsey, N.J.) according to the CIELAB scale (Mclaren and Rigg, 2008). White calibration plate was used for the instrument recalibration. All samples were prepared in duplicate, and each of the repetitions was measured three times. The whiteness index (WI) was determined as follows (Vargas et al., 2008):
WI=100−√{square root over ((100−L)2+a2+b2)} Equation 3:
Accelerated physical stability of emulsion. The physical stability of PPI emulsions with three different oil concentrations was evaluated using an analytical centrifugal analyzer (LUMisizer, L.U.M GmbH, Berlin, Germany). The transmission extinction profile was recorded at 2000 rpm, 20° C. for 11 h.
In the present study, the influence of HPH on the emulsion properties of PPI-based yogurt-like products with low (1.5%, v/v) and high (10%, v/v) oil content was tested and compared to the 3% v/v oil as in study 1.
The PSD of emulsions containing PPI and different concentrations of canola oil, treated with a pre-processing step, was examined as a function of the homogenization pressure. As shown in
In yogurt, we expect a high level of whiteness index (WI) correlated with the white color. As shown in
Analytical centrifugation and the time and space-resolved transmission extinction profiles evaluated under accelerated conditions were used to quantify the phase separation (creaming) velocity of the emulsions. Among PPI emulsions, it can be visually observed (
The rheological properties of PPI yogurt-like structure obtained from varying oil concentration emulsions homogenized at different pressures were characterized by frequency-dependent dynamic oscillatory measurement. The average curves are presented in
WI of the PPI yogurt substitutes is shown in
The utilization of HPH allowed the production of a stabilizer-free and non-allergenic PPI yogurt substitute with higher protein content, with high and low oil concentrations. In the non HPH treated sample we see both the creaming effect and the color being very different from the expected from milk yogurt.
Particle size distribution measurements. The particle size distribution (PSD) of 5% PI suspensions before and after the pre-processing step at 200 MPa, Tm=15° C., was measured by static light scattering measurement (Mastersizer 3000, Malvern Instruments, UK). The values of particle refractive index of PI suspensions and particle absorption indexes were 1.52 and 0.001, respectively. The dispersant refractive index (water) was 1.330.
Accelerated physical stability of pea isolate suspensions. Physical stability under accelerated conditions of 5% PI suspension before and after the pre-processing step at 200 MPa, Tin=15° C., was measured using a an analytical centrifugal analyzer (LUMisizer, L.U.M GmbH, Berlin, Germany).
Zeta potential measurements. Zeta potential of 5% PI suspensions was determined at phosphate buffer (pH=7.0, 10 mM) before and after the pre-processing step at 200 MPa, Tin=15° C., using a Zetasizer Nano ZS (Malvern Instruments, UK).
In the present study, the effect of U(HPH) (200 MPa, Tin=15° C.) on the physical stability against separation of five different commercially available pea protein isolates (PI) (5%), more specifically Peal (Yantai Shuangta Food Co., Ltd.); C9 and B9 (Cosucra); and 85D and 85F (ROQUETTE), was tested. The physical stability was tested during time (24h).
Visually, the HPH pre-processing step of the protein suspensions increases the suspensions' physical stability immediately after the homogenization. Some isolates were separated after 1h and 24h, yet in all cases, pre-processing step provided stabilization. This was verified by other methods as well.
A bimodal distribution characterizes the PSD of the PI suspensions with and without the pre-processing step. The HPH pressure level increased, a suspension with smaller particle size is formed while keeping the bimodal distribution (
Analytical centrifugation and the time and space-resolved transmission extinction profiles evaluated under accelerated conditions were used to test the phase separation (sedimentation). In most cases, a significant difference (p<0.05) was also observed between most of the isolates before and after the pre-processing step. These results correlate with the decrease in PSD after the HPH step since the stability of suspensions and emulsions is a function of the particle size. As can also be visually observed (
The zeta potential was affected by the HPH processing step (
This application is a Continuation-in-Part of PCT Application No. PCT/IL2021/050414, filed on Apr. 12, 2021, which claims the benefit of U.S. Provisional Application No. 63/009,081, filed Apr. 13, 2020. The disclosures of the above-described applications are hereby incorporated by reference in their entirety under 37 CFR 1.57.
| Number | Date | Country | |
|---|---|---|---|
| 63009081 | Apr 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IL2021/050414 | Apr 2021 | US |
| Child | 17823933 | US |
