Control of protein digestion under simulated gastrointestinal conditions using biopolymer microgels

Influence of hydrophilic polysaccharide fat replacers on the in vitro digestibility of protein in emulsion-type sausage

Hydrophilic polysaccharides have been widely applied as fat replacers in meat products, but their effects on the digestibility of meat proteins has seldom been studied. Replacement of backfat in emulsion-type sausage with konjac gum (KG), sodium alginate (SA) and xanthan gum (XG) were found to reduce the released amino group (-NH₂) during simulated gastric digestion and initial intestinal digestion. The suppressed gastric digestibility of protein was verified by the denser structures of protein gastric digests and reduced generation of peptides in gastric digestion when a polysaccharide was added. After the whole gastrointestinal digestion, high level of SA and XG resulted in larger digests and a more obvious SDS-PAGE band between 5 and 15 kDa, and KG and SA significantly reduced the total release of -NH₂. Additional of KG, SA and XG were found to the increase the viscosity of the gastric digests mixture, which could account for the reduced hydrolysis efficiency of pepsin during the gastric digestion, as evidenced in the pepsin activity study (decreased by 12.2-39.1%). This work highlights the influence of polysaccharide fat replacer on the digestibility of meat protein by changing the matrix characteristics.

Food biopolymer behaviors in the digestive tract: implications for nutrient delivery

Biopolymers are prevalent in both natural and processed foods, serving as thickeners, emulsifiers, and stabilizers. Although specific biopolymers are known to affect digestion, the mechanisms behind their influence on the nutrient absorption and bioavailability in processed foods are not yet fully understood. The aim of this review is to elucidate the complex interplay between biopolymers and their behavior in vivo, and to provide insights into the possible physiological consequences of their consumption. The colloidization process of biopolymer in various phases of digestion was analyzed and its impact on nutrition absorption and gastrointestinal tract was summarized. Furthermore, the review discusses the methodologies used to assess colloidization and emphasizes the need for more realistic models to overcome challenges in practical applications. By controlling macronutrient bioavailability using biopolymers, it is possible to enhance health benefits, such as improving gut health, aiding in weight management, and regulating blood sugar levels. The physiological effect of extracted biopolymers utilized in modern food structuring technology cannot be predicted solely based on their inherent functionality. It is essential to account for factors such as their initial consuming state and interactions with other food components to better understand the potential health benefits of biopolymers.

Gene network analyses of larvae under different egg-protecting behaviors provide novel insights into immune response mechanisms of Amphioctopus fangsiao

Amphioctopus fangsiao was a representative economic species in cephalopods, which was vulnerable to marine bacteria. Vibrio anguillarum was a highly infectious pathogen that have recently been found to infect A. fangsiao and inhibit its growth and development. There were significant differences in the immune response mechanisms between egg-protected and egg-unprotected larvae. To explore larval immunity under different egg-protecting behaviors, we infected A. fangsiao larvae with V. anguillarum for 24 h and analyzed the transcriptome data about egg-protected and egg-unprotected larvae infected with 0, 4, 12, and 24 h using weighted gene co-expression networks (WGCNA) and protein-protein interaction (PPI) networks. Network analyses revealed a series of immune response processes after infection, and identified six key modules and multiple immune-related hub genes. Meanwhile, we found that ZNF family, such as ZNF32, ZNF160, ZNF271, ZNF479, and ZNF493 might play significant roles in A. fangsiao immune response processes. We first creatively combined WGCNA and PPI network analysis to deeply explore the immune response mechanisms of A. fangsiao larvae with different egg-protecting behaviors. Our results provided further insights into the immunity of V. anguillarum infected invertebrates, and laid the foundation for exploring the immune differences among cephalopods with different egg protecting behaviors.

Producing mixed-soy protein adsorption layers on alginate microgels to controlled-release β-carotene

In this study, the effects of soy protein isolate (SPI) on the morphology, encapsulation efficiency, storage stability, swelling behavior, and in vitro digestion behavior of calcium alginate (CA) microgels were investigated. CA and calcium alginate-SPI (CAS) microgels with encapsulated β-carotene were prepared by extruding a mixture of alginate and SPI using a co-extrusion technique, followed by cross-linking with Ca²⁺. All microgels exhibited homogeneous sizes and spherical shapes, and CAS microgels showed high levels of protein loading efficiency. The encapsulation efficiency and storage stability of β-carotene within CAS microgels were higher than those within CA microgels. The introduction of SPI into CAS microgels resulted in a higher degree of gel size shrinkage in gastric fluid and a lower degree of swelling in intestinal fluid compared to CA microgels. In vitro digestion was conducted to investigate the effects of the addition of SPI on the release behavior of CA and CAS microgels. Results obtained showed that CAS microgels were more resistant to simulated gastric fluid than CA microgels. Cryo-scanning electron microscopy (cryo-SEM) and confocal laser scanning microscopy (CLSM) observations indicated that the release behavior was dependent on the porosity of the CA and CAS microgels, and the porosity was influenced by the concentration of SPI. This study showed that the introduction of SPI to CA microgels can lead to the development of an effective controlled release delivery system.

Recent advances in cellulose microgels: Preparations and functionalized applications

Microgels are soft, deformable, permeable, and stimuli-responsive microscopic polymeric particles that are now emerging as prospective multifunctional soft materials for delivery systems, interface stabilization, cell cultures and tissue engineering. Cellulose microgels are emerging biopolymeric microgels with unique characteristics such as abound hydroxyl structure, admirable designability, multiscale pore network and excellent biocompatibility. This review summarizes the fabrication strategies for microgel, then highlights the fabrication routes for cellulose microgels, and finally elaborates cellulose microgels' bright application prospects with unique characteristics in the fields of controlled release, interface stabilization, coating, purification, nutrition/drug delivery, and bio-fabrication. The challenges to be addressed for further applications and considerable scope for development in future of cellulose microgels are also discussed.

Fish Processing and Digestion Affect Parvalbumins Detectability in Gilthead Seabream and European Seabass

Consumption of aquatic food, including fish, accounts for 17% of animal protein intake. However, fish consumption might also result in several side-effects such as sneezing, swelling and anaphylaxis in sensitized consumers. Fish allergy is an immune reaction to allergenic proteins in the fish muscle, for instance parvalbumin (PV), considered the major fish allergen. In this study, we characterize PV in two economically important fish species for southern European aquaculture, namely gilthead seabream and European seabass, to understand its stability during in vitro digestion and fish processing. This information is crucial for future studies on the allergenicity of processed fish products. PVs were extracted from fish muscles, identified by mass spectrometry (MS), and detected by sandwich enzyme-linked immunosorbent assay (ELISA) after simulated digestion and various food processing treatments. Secondary structures were determined by circular dichroism (CD) after purification by anion exchange and gel filtration chromatography. In both species, PVs presented as α-helical and β-sheet structures, at room temperature, were shown to unfold at boiling temperatures. In European seabass, PV detectability decreased during the simulated digestion and after 240 min (intestinal phase) no detection was observed, while steaming showed a decrease (p < 0.05) in PVs detectability in comparison to raw muscle samples, for both species. Additionally, freezing (−20 °C) for up to 12 months continued to reduce the detectability of PV in tested processing techniques. We concluded that PVs from both species are susceptible to digestion and processing techniques such as steaming and freezing. Our study obtained preliminary results for further research on the allergenic potential of PV after digestion and processing.

Bioactive and health-promoting properties of enzymatic hydrolysates of legume proteins: a review

This study comprehensively reviewed the effect of controlled enzymatic hydrolysis on the bioactivity of pulse protein hydrolysates (PPHs). Proteolysis results in the partial structural unfolding of pulse proteins with an increase in buried hydrophobic groups of peptide sequences. The use of PPHs in a dose-dependent manner can enhance free radical scavenging and improve antioxidant activities regarding inhibition of lipid oxidation, ferric reducing power, metal ion chelation, and β-carotene bleaching inhibition. Ultrafiltered peptide fractions with low molecular weights imparted angiotensin-I converting enzyme (ACE) inhibitory effects during in vitro simulated gastrointestinal digestion and in vivo conditions. Ultrasonication, high-pressure pretreatments, and glycosylation as post-treatments can improve the antiradical, antioxidant, and ACE inhibitory activities of PPHs. The electrostatic attachment of pulse peptides to microbial cells can inhibit the growth and activity of bacteria and fungi. Bioactive pulse peptides can reduce serum cholesterol and triglycerides, and inhibit the formation of adipocyte lipid storage, allergenic factors, inflammatory markers, and arterial thrombus without cytotoxicity. The combination of germination and enzymatic hydrolysis can significantly increase the protein digestibility and bioavailability of essential amino acids. Moreover, the utilization and enrichment of bakery and meat products with functional PPHs ensure quality, safety, and health aspects of food products.

Gastrointestinal Fate and Fatty Acid Release of Pickering Emulsions Stabilized by Mixtures of Plant Protein Microgels + Cellulose Particles: an In Vitro Static Digestion Study

The present study aims to investigate the in vitro intestinal digestion fate of Pickering emulsions with complex dual particle interfaces. Pickering oil-in-water emulsions (PPM-E) stabilized by plant (pea) protein-based microgels (PPM), as well as PPM-E where the interface was additionally covered by cellulose nanocrystals (CNC), were designed at acidic pH (pH 3.0). The gastrointestinal fate of the PPM-E and free fatty acid (FFA) release, was tested via the INFOGEST static in vitro digestion model and data was fitted using theoretical models. Lipid digestion was also monitored using lipase alone bypassing the gastric phase to understand the impact of proteolysis on FFA release. Coalescence was observed in the PPM-stabilized emulsions in the gastric phase, but not in those co-stabilized by CNC. However, coalescence occurred during the intestinal digestion stage, irrespective of the CNC concentration added (1–3 wt % CNC). The presence of CNC lowered the lipolysis kinetics but raised the extent of FFA release as compared to in its absence (p < 0.05), due to lower levels of gastric coalescence, i.e., a higher interfacial area. The trends were similar when just lipase was added with no prior gastric phase, although the extent and rate of FFA release was reduced in all emulsions, highlighting the importance of prior proteolysis in lipolysis of such systems. In summary, an electrostatically self-assembled interfacial structure of two types of oppositely-charged particles (at gastric pH) might be a useful strategy to enable enhanced delivery of lipophilic compounds that require protection in the stomach but release in the intestines.

Impact of the Structural Modifications of Potato Protein in the Digestibility Process under Semi-Dynamic Simulated Human Gastrointestinal In Vitro System

The raising consumer demand for plant-derived proteins has led to an increased production of alternative protein ingredients with varying processing histories. In this study, we used a commercially available potato protein ingredient with a nutritionally valuable amino acid profile and high technological functionality to evaluate if the digestibility of a suspension with the same composition is affected by differences in the structure. Four isocaloric (4% protein, w/w) matrices (suspension, gel, foam and heat-set foam) were prepared and their gastrointestinal fate was followed utilizing a semi-dynamic in vitro digestion model. The microstructure was observed by confocal laser scanning microscopy, protein breakdown was tested by electrophoresis and free amino acids after intestinal digestion was estimated using liquid chromatography/triple-quadruple-mass spectrometry (LC-TQMS). The heat-treated samples showed a higher degree of hydrolysis and lower trypsin inhibitory activity than the non-heat-treated samples. An in vitro digestible indispensable amino acid score was calculated based on experimental data, showing a value of 0.9 based on sulfur amino acids/valine as the limiting amino acids. The heated samples also showed a slower gastric emptying rate. The study highlights the effect of the food matrix on the distribution of the peptides created during various stages of gastric emptying.

Characterization and gelling properties of a bioactive extract from Ascophyllum nodosum obtained using a chemical-free approach

The bioactivity and gelling properties of a carbohydrate-rich algal extract obtained from locally harvested Ascophyllum nodosum seaweed using a chemical-free approach were investigated for its potential interest in food applications. Physicochemical characterisation and compositional analysis of the extract, using FTIR, biochemical methods and monosaccharide analysis, confirmed the presence of alginates and fucoidans, although the main polysaccharide present in it was laminarin. Significant amounts of phenolic compounds (~9 ​mg phloroglucinol/100 ​mg sample) were also detected. As a result, the extract exhibited good antioxidant activity. It also showed promising prebiotic potential, promoting the growth of beneficial Lactobacillus sp. and Bifidobacteria sp. when compared with commercial prebiotics, but not that of pathogenic bacteria such as E. coli or P. aeruginosa. The gelling properties of the raw extract were explored to optimize hydrogel bead formation by external gelation in CaCl₂ solutions. This was enhanced at neutral to alkaline pHs and high extract and CaCl₂ concentrations. The mechanical strength, nano- and microstructure of the hydrogel beads prepared under optimised conditions were determined using compression tests, synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS) and scanning electron microscopy (SEM). It was concluded that the raw algal extract at neutral pH had potential for use as a gelling agent, although further enrichment with alginate improved the mechanical properties of the obtained gels. The advantages and disadvantages of applying the non-purified algal extract in comparison with purified carbohydrates are discussed.

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Carbohydrate-rich extract from A. nodosum obtained using a chemical-free process.

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The algal extract exhibited in-vitro antioxidant and prebiotic properties.

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Beads were obtained by external gelation of the extract at neutral to alkaline pH.

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Enrichment with alginate improved the mechanical properties of the gels.

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Components of the extract acted as fillers, reducing structural changes upon drying.

Recent Progress on Polysaccharide-Based Hydrogels for Controlled Delivery of Therapeutic Biomolecules

A plethora of applications using polysaccharides have been developed in recent years due to their availability as well as their frequent nontoxicity and biodegradability. These polymers are usually obtained from renewable sources or are byproducts of industrial processes, thus, their use is collaborative in waste management and shows promise for an enhanced sustainable circular economy. Regarding the development of novel delivery systems for biotherapeutics, the potential of polysaccharides is attractive for the previously mentioned properties and also for the possibility of chemical modification of their structures, their ability to form matrixes of diverse architectures and mechanical properties, as well as for their ability to maintain bioactivity following incorporation of the biomolecules into the matrix. Biotherapeutics, such as proteins, growth factors, gene vectors, enzymes, hormones, DNA/RNA, and antibodies are currently in use as major therapeutics in a wide range of pathologies. In the present review, we summarize recent progress in the development of polysaccharide-based hydrogels of diverse nature, alone or in combination with other polymers or drug delivery systems, which have been implemented in the delivery of biotherapeutics in the pharmaceutical and biomedical fields.

Standardized methods for testing the quality attributes of plant-based foods: Milk and cream alternatives

The food industry is creating a diverse range of plant-based alternatives to dairy products, such as milks, creams, yogurts, and cheeses due to the increasing demand from consumers for more sustainable, healthy, and ethical products. These dairy alternatives are often designed to mimic the desirable physicochemical, functional, and sensory properties of real dairy products, such as their appearance, texture, mouthfeel, flavor, and shelf-life. At present, there is a lack of systematic testing methods to characterize the properties of plant-based dairy alternatives. The purpose of this review is to critically evaluate existing methods and recommend a series of standardized tests that could be used to quantify the properties of fluid plant-based milk alternatives (milk and cream). These methods could then be used to facilitate the design of milk alternatives with somewhat similar attributes as real dairy milk by comparing their properties under standardized conditions. Moreover, they could be used to facilitate comparison of the properties of milk alternatives developed in different laboratories.

Current Evidence on the Bioavailability of Food Bioactive Peptides

Food protein-derived bioactive peptides are recognized as valuable ingredients of functional foods and/or nutraceuticals to promote health and reduce the risk of chronic diseases. However, although peptides have been demonstrated to exert multiple benefits by biochemical assays, cell culture, and animal models, the ability to translate the new findings into practical or commercial uses remains delayed. This fact is mainly due to the lack of correlation of in vitro findings with in vivo functions of peptides because of their low bioavailability. Once ingested, peptides need to resist the action of digestive enzymes during their transit through the gastrointestinal tract and cross the intestinal epithelial barrier to reach the target organs in an intact and active form to exert their health-promoting properties. Thus, for a better understanding of the in vivo physiological effects of food bioactive peptides, extensive research studies on their gastrointestinal stability and transport are needed. This review summarizes the most current evidence on those factors affecting the digestive and absorptive processes of food bioactive peptides, the recently designed models mimicking the gastrointestinal environment, as well as the novel strategies developed and currently applied to enhance the absorption and bioavailability of peptides.

Bioavailability and bioaccessibility of food bioactive compounds; overview and assessment by in vitro methods

Oral bioavailability is the key to the bioefficiency of food bioactive ingredients; it evaluates the relationship between foods and their health benefits. The analysis of the main factors limiting the oral bioavailability (bioaccessibility, absorption, and transformation) has led to the proposal of classification systems for pharmaceuticals and nutraceuticals (Biopharmaceuticals Classification System and Nutraceutical Bioavailability Classification Scheme). Based on the relevant studies published in the last decade, this review presents the essential aspects regarding the factors limiting the oral bioavailability of the biocomponents and different in vitro methods used to investigate the mechanisms involved in the digestion, absorption, and metabolism of biocomponents, particularly encapsulated bioactive compounds. Oral bioavailability investigated by in vitro studies provides the food and drug manufacturers with information to formulate delivery systems more efficiently and to determine the dosage of biocomponents for increase the health benefits and avoid or reduce the risk of toxicity.

Human-like collagen promotes the healing of acetic acid-induced gastric ulcers in rats by regulating NOS and growth factors

Human-like collagen (HLC), the collagen produced using fermentation technology, has been demonstrated previously to promote wound healing. However, the healing property of HLC in gastric ulcers remains to be verified. In this study, we investigated the healing efficacy and healing mechanisms of HLC on gastric ulcers. To investigate whether HLC still has healing activity on gastric ulcers after gastric digestion, we simulated gastric digestion in vitro to obtain a human-like collagen digestion product (HLCP) and used it as the control drug. A chronic gastric ulcer model induced by 60% acetic acid in rats was used to evaluate the healing effect of gastric ulcers in this study. The results showed that oral administration of HLC or HLCP for 4 or 7 days promoted ulcer healing, which can be directly observed by significant reductions in ulcer area. The oral administration of HLC and HLCP significantly increased the protein expression of growth factors (EGF, HGF, VEGF, bFGF and TGF-β1) and the HGF receptor (HGFr), promoted collagen deposition, regulated the activity of NOS, and decreased pro-inflammatory cytokines (TNF-a, il-6, il-10) and endothelin-1 (ET-1) levels in gastric tissue. Moreover, cell experiments showed that the effects of HLC on cell proliferation and migration are mainly caused by its digestion products. These findings indicate that HLC may be used as a nutritional supplement or therapeutic drug to promote the healing of gastric ulcers.

Natural biopolymer-based hydrogels for use in food and agriculture

Hydrogels are important materials that are of high scientific interest and with numerous applications. Natural polymer-based hydrogels are preferred to synthetic ones due to their safety, biocompatibility, and ecofriendly properties. They have been studied extensively and implemented in various fields, such as medicine, cosmetics, personal-care products, water purification, and more. This review focuses on the applications of nature-sourced polymer-based hydrogels in food and agriculture. Different types of biopolymers and crosslinking agents, and various methods for hydrogel formation are described. The physicomechanical properties and applied activities of the resulting materials are also comprehensively discussed. Biodegradable synthetic polymers are outside the scope of this review. © 2020 Society of Chemical Industry.

Modulation of physicochemical stability and bioaccessibility of β-carotene using alginate beads and emulsion stabilized by scallop (Patinopecten yessoensis) gonad protein isolates

The colloidal delivery systems fabricated by emulsion containing natural proteins and lipids have been utilized to protect carotenoids as well as to release the carotenoids in the simulated in vitro gastrointestinal tract (GIT). In this study, β-carotene (BC) was embedded into emulsions that were stabilized by scallop gonad protein isolates (SGPIs), and the emulsion droplets containing BC were then entrapped into calcium-alginate beads. The results showed that the oil-in-water emulsions coated by SGPIs only showed good stability at pH 7-8, while the emulsion-alginate beads remained relatively intact at pH 3-8. BC encapsulated in emulsions was extremely unstable and prone to degradation when stored at the comparatively higher temperature (37 °C), whereas the stability of BC was greatly enhanced through incorporation into emulsion-alginate beads. The digestion rate and extent of lipid droplets constructed within SGPIs-stabilized emulsion-alginate beads were slower than that in emulsions during GIT. The confocal laser scanning microscopy revealed that the lipid droplets in emulsions were aggregated after exposure to the mouth and gastric phases, while the emulsion-alginate beads maintained their spherical shape after exposure to the oral and gastric phases. Moreover, the free lipid droplets in the emulsions showed a higher bioaccessibility of BC (66%) than that in the emulsion-alginate beads (38%), whereas the BC transformation was on the contrary. The findings in this study indicated that SGPIs-stabilized emulsion in alginate beads can potentially be utilized for the encapsulation and controlled release of lipophilic bioactive compounds.

Antihyperglycemic and hypoglycemic activity of naturally occurring peptides and protein hydrolysates from easy-to-cook and hard-to-cook beans (Phaseolus vulgaris L.)

The present study was undertaken to examine the antidiabetic potential of naturally occurring peptides and hydrolysate fractions from easy-to-cook (ETC) and hard-to-cook (HTC) beans. All fractions were tested regarding their in vitro inhibitory activities against α-amylase and α-glucosidase as well as in vivo anti-hyperglycemic and hypoglycemic effects. Results evidenced that the peptide fractions with the lowest molecular weight (<3 kDa) have the highest inhibitory activities, and a 16.9%-89.1% inhibition of α-amylase and 34.4%-89.2% inhibition of α-glucosidase were observed. Regarding the antihyperglycemic activity, the fraction ETCNO3-10 showed a better performance than the positive control (acarbose). In addition, results from hypoglycemic activity evidenced that the tested peptide fractions were able to decrease the glucose levels at the same extension of glibenclamide, maintaining a constant basal glucose level without a postprandial hyperglycemia peak. Finally, it is possible to suggest that the naturally occurring peptides and hydrolysate fractions obtained from ETC and HTC common beans could be used in functional food production or pharmaceutical formulations to prevent diabetes.

Physico-Chemical Changes of Composite Whey Protein Hydrogels in Simulated Gastric Fluid Conditions

Polysaccharide blended whey protein isolate (WPI) hydrogels were developed for the delivery of black carrot ( Daucus carota) concentrate as bioactive agent in simulated gastric fluid (SGF). Pectin (PC), gum tragacanth (GT), and xanthan gum (XG) were blended as additional polymers to modulate the release characteristics of the WPI hydrogels. Experiments showed that sole whey protein (C), XG, and GT blended hydrogels possessed restricted release profiles 67%, 61%, and 67%, respectively, whereas PC samples attained higher release rates (83%) ( p < 0.05). Interactions between polymers and aqueous medium were analyzed by nuclear magnetic resonance relaxometry. C (82 ms) and GT (84 ms) hydrogels attained higher T₂ values than PC (74 ms) and XG (73 ms) samples in SGF. Hardness of only XG hydrogels increased from 1.9 to 4.1 N after gastric treatment. Physicochemical changes within hydrogels during release were also investigated, and hydrogels were proved to be appropriate for desired delivery purposes.

Protein Hydrolysates' Absorption Characteristics in the Dynamic Small Intestine In Vivo

Background: Dietary proteins are known for their wide range of nutritional, functional and biological properties. Although the total amount of proteins may be obtained from mixtures, its “availability” for absorption in the gut is in many cases quite uncertain or even varies for the same food depending on processing conditions, the presence of other components, and so on. Methods: To obtain accurate protein hydrolysate absorption data, we have developed a small intestine model (SIM) to test them. Results: The results indicated that the protein hydrolysates were absorbed rapidly during the first 15 min, and then decreased to 90 min, then they were absorbed again from 90 min to the endpoint. The protein absorption was also affected by the protein processing method used. The Enzyme + Ultrasound (EU) processing method group had a higher absorption rate than the Enzyme (E) processing method group, and the absorption of the Enzyme + Artificial gastric juice processing method (EH) and Enzyme + Ultrasound + Artificial gastric juice processing method (EUH) groups was reduced compared to the E group alone. The amino acid analysis results showed that the amino acids were reduced and absorbed by our SIM in almost all groups except for cysteine and methionine. In general, the Pearson relation value of the amino acid contents between before SIM and after SIM was 0.887, which indicated that single amino acid absorption was mainly related to its content in the whole amino acids. The single amino acid absorption ratio among different groups also displayed differences, which ranged from 31% to 46% (E group from 39% to 42%; EU group from 40% to 47%; EH group from 31% to 39%; EUH group from 35% to 41%). Conclusions: The protein hydrolysates’ varied from startpoint to endpoint, and the protein absorption was affected by processing method.