Compared digestibility of plant protein isolates by using the INFOGEST digestion protocol

The structure-function relationships and techno-functions of β-conglycinin

β-conglycinin (β-CG) is a prominent storage protein belonging to the globulin family in soybean (Glycine max) seeds. Along with other soybean proteins, it serves as an important source of essential amino acids and high-quality nutrition. However, the digestibility and nutritional value of β-CG are key factors affecting the nutritional profile of soy-based foods. The heterotrimeric, secondary, and quaternary structures of β-CG, particularly the spatial arrangement of its α, α', and β subunits, influence its functional properties. Considering these aspects, β-CG emerges as a significant protein with diverse applications in the food and health sectors. Therefore, this review explores β-CG's composition, structure, function, health implications, and industrial uses. Salient discussions are presented on its molecular structure, nutrition, digestibility, allergenicity, and techno-functions including emulsification, solubility, gelling, and structure-function complexities. Overall, the multifaceted potential of β-CG in the healthcare sector and the food industry is evident.

Fermented blend from sunflower seed press-cake and bovine sweet whey: Protein breakdown during in vitro gastrointestinal digestion

Sustainable food production implements circular economic system, valuing side streams and minimizing waste. This study was aimed to develop a new food by fermenting a blend of dehulled sunflower seed protein powder (SSPP) and reconstituted bovine sweet whey powder (RSWP). Blends were inoculated with Lactococcus lactis B12 alone or in association with Saccharomyces cerevisiae L12, and fermentation proceeded until reaching pH 4.8. After in vitro static gastrointestinal digestion, RSWP and SSPP proteins were highly proteolyzed and the soluble nitrogen content was 69-71% of total nitrogen. In digests, 42-75 unique peptides were identified, and most of them weighed 500-1000 Da. Free amino acids accounted for 202-228 mg/g protein in digests. Few bioactive peptides derived from RSWP were identified. These findings demonstrated strong degradability of RSWP and SSPP proteins during digestion and shed light on nutritional properties exploitable for food applications of the developed fermented blend.

Study on gastric digestion behavior of phytase-treated soybean protein: A semi-dynamic digestion method

The digestive characteristics of plant proteins are crucial for their nutritional value and utilization efficiency. In this study, an in vitro semi-dynamic digestion model was employed to investigate the gastric digestion process of soybean protein after treatment with phytase. The results found that phytase treatment reduced the phytate content in soybean proteins (22.83 ± 0.09 to 8.72 ± 0.07 mg/g), shifted its isoelectric point towards the alkaline range by 1 pH unit, and significantly improved its solubility at pH 4.0. Particularly for protein sample treated with phytase after acid precipitation, the formation of aggregates during digestion was weakened, resulting in a significantly higher digestion rate compared to untreated SPI, with digestion being at least 15 min faster than SPI. This study provides a strategy for preparing soybean protein with faster digestion and weaker clot-forming ability during digestion, which offers insights for the application of soybean protein in clinical nutrition products and specialized medical foods.

Influence of InVitro Digestion on Dipeptidyl Peptidase-IV (DPP-IV) Inhibitory Activity of Plant-Protein Hydrolysates Obtained from Agro-Industrial By-Products

This study investigates the production of protein hydrolysates with dipeptidyl peptidase-IV (DPP-IV) inhibitory activity from agro-industrial by-products, namely olive seed, sunflower seed, rapeseed, and lupin meals, as well as from two plant protein isolates such as pea and potato. Furthermore, the effect of simulated gastrointestinal digestion on the DPP-IV inhibitory activity of all the hydrolysates was evaluated. Overall, the lowest values of IC50 (1.02 ± 0.09 - 1.24 ± 0.19 mg protein/mL) were observed for the hydrolysates with a high proportion of short-chain [< 1 kDa] peptides (i.e., olive seed, sunflower seed, and lupin) or high content of proline (i.e., rapeseed). Contrarily, the IC50 of the pea and potato hydrolysates was significantly higher (1.50 ± 0.13 - 1.93 ± 0.13 mg protein/mL). In vitro digestion led to an increase in peptides <1 kDa for almost all hydrolysates (except olive and sunflower seed meals), which was noticeable for rapeseed, pea, and potato hydrolysates. Digestion did not significantly modify the DPP-IV inhibitory activity of olive, sunflower, rapeseed, and potato hydrolysates, whereas a significant decrease in IC50 value was obtained for pea hydrolysate and a significant increase in IC50 was obtained for lupin hydrolysate. Thus, this work shows the potential of agro-industrial by-products for the production of protein hydrolysates exhibiting DPP-IV inhibition.

The role of fiber in modulating plant protein-induced metabolic responses

The rising consumption of plant protein foods and the emergence of meat alternatives have prompted interest in the health benefits of such products, which contain fiber in addition to protein. This review investigates the effect of fiber on plant-based protein metabolism and evaluates its contribution to gut-derived health impacts. Plant proteins, which often come with added fiber, can have varying health outcomes. Factors such as processing and the presence of fiber and starch influence the digestibility of plant proteins, potentially leading to increased proteolytic fermentation in the gut and the production of harmful metabolites. However, fermentable fiber can counteract this effect by serving as a primary substrate for gut microbes, decreasing proteolytic activity. The increased amount of fiber, rather than the protein source itself, plays a significant role in the observed health benefits of plant-based diets in human studies. Differences between extrinsic and intrinsic fiber in the food matrix further impact protein fermentation and digestibility. Thus, in novel protein products without naturally occurring fiber, the health impact may differ from conventional plant protein sources. The influence of various fibers on plant-based protein metabolism throughout the gastrointestinal tract is not fully understood, necessitating further research.

Experimental Protocols Used to Mimic Gastrointestinal Protein Digestion: A Systematic Review

Bioactive peptides derived from native proteins modulate physiological processes in the metabolic pathways. Given that multiple protocols in the literature mimic the digestion of dietary components, gathering studies that use such models directed at protein digestion processes is critical. This systematic review aimed to gather evidence that adopted adequate experimental models to simulate human protein digestion. The databases searched were PubMed, Web of Science, ScienceDirect, Embase, Virtual Health Library, and Scopus. A total of 1985 articles were found, resulting in 20 eligible in vitro studies. The Office of Health Assessment and Translation was used to evaluate methodological quality. Seven studies used plant-based protein sources, twelve used animal protein sources, and one used both. The duration of the oral phase varied, although 60% of the studies employed a protein digestion period of 120 min. Amylase, pepsin, and pancreatin enzymes were utilized in 40% of the studies, with pH levels of 7, 3, and 7, respectively, during the oral, gastric, and intestinal phases. The INFOGEST harmonized static model was adopted by 65% of the studies; INFOGEST is the most effective model for simulating gastrointestinal protein processes in humans and can be used to answer several research questions because it describes experimental conditions close to the human physiological situation.

Assessing the Protein Quality, In Vitro Intestinal Iron Absorption and Human Faecal Microbiota Impacts of Plant-Based Mince

The nutritional quality of plant-based meat analogues compared to traditional meat products has been questioned in recent commentary, particularly in relation to protein quality and micronutrient bioavailability. However, the attributes of specific products within this category are unclear. We therefore undertook a comprehensive assessment of the compositional and functional attributes of v2food® (Sydney, Australia) plant-based mince, including an assessment of the effects of reformulation, including the addition of amino acids, ascorbic acid, and different forms of elemental iron. The protein digestibility and protein quality of v2food® plant-based mince were comparable to beef mince in the standardized INFOGEST system, and favourable effects on microbiota composition and short-chain fatty acid (SCFA) production were demonstrated in an in vitro digestion system. The use of ferrous sulphate as an iron source improved in vitro intestinal iron absorption by ~50% in comparison to other forms of iron (p < 0.05), although levels were ~3-fold lower than beef mince, even in the presence of ascorbic acid. In conclusion, the current study identified some favourable nutritional attributes of plant-based v2food® mince, specifically microbiota and SCFA changes, as well as other areas where further reformulation could be considered to further enhance the bioavailability of key nutrients. Further studies to assess the effect of plant-based meat analogues on health measures in vivo will be important to improve knowledge in this area.

Aggregation structure induced by heat treatments mediated the gastric digestion behavior of soybean protein

The common belief that heat treatment enhances the gastric digestion of proteins is largely based on findings from animal proteins and may not apply to all proteins, particularly plant proteins. Here, we compared the digestion characteristics of soybean protein isolates (SPI) in an in vitro semi-dynamic digestion model and found distinct effects of heat treatment on the digestion properties of plant proteins. The results revealed that heat-treated SPIs formed clots during the early stages of digestion, although the clots gradually became smaller and looser as digestion progressed, the systems remained turbid at the end of gastric digestion, indicating the lag in their emptying. Furthermore, heat treatment altered the rheological properties of SPI, resulting in increased viscosity and slower gastric emptying. These effects became more pronounced with increasing heat treatment temperatures. The fluorescence spectrum analysis indicated that heat treatment altered its conformation. This led to protein unfolding and exposure of hydrophobic groups, facilitating the formation of larger aggregates during digestion. Additionally, heat treatment exposed more cleavage sites for gastric proteases, increasing the extent of hydrolysis. Elevated levels of free amino acids and a smaller molecular weight distribution further corroborated these findings. These findings contribute to a deeper understanding of the gastric digestion characteristics of plant proteins and the relationship between protein aggregation structure and the digestion process.

Plant-Based Meat Analogues in the Human Diet: What Are the Hazards?

Research regarding meat analogues is mostly based on formulation and process development. Information concerning their safety, shelf life, and long-term nutritional and health effects is limited. This article reviews the existing literature and analyzes potential hazards introduced or modified throughout the processing chain of plant-based meat analogues via extrusion processing, encompassing nutritional, microbiological, chemical, and allergen aspects. It was found that the nutritional value of plant-based raw materials and proteins extracted thereof increases along the processing chain. However, the nutritional value of plant-based meat analogues is lower than that of e.g., animal-based products. Consequently, higher quantities of these products might be needed to achieve a nutritional profile similar to e.g., meat. This could lead to an increased ingestion of undigestible proteins and dietary fiber. Although dietary fibers are known to have many positive health benefits, they present a hazard since their consumption at high concentrations might lead to gastrointestinal reactions. Even though there is plenty of ongoing research on this topic, it is still not clear how the sole absorption of metabolites derived from plant-based products compared with animal-based products ultimately affects human health. Allergens were identified as a hazard since plant-based proteins can induce an allergic reaction, are known to have cross-reactivities with other allergens and cannot be eliminated during the processing of meat analogues. Microbiological hazards, especially the occurrence of spore- and non-spore-forming bacteria, do not represent a particular case if requirements and regulations are met. Lastly, it was concluded that there are still many unknown variables and open questions regarding potential hazards possibly present in meat analogues, including processing-related compounds such as n-nitrosamines, acrylamide, and heterocyclic aromatic amino acids.

In vitro protein digestibility of RuBisCO-enriched wheat dough: a comparative study with pea and gluten proteins

Growing demand for sustainable, plant-based protein sources has stimulated interest in new ingredients for food enrichment. This study investigates the nutritional and digestive implications of enriching wheat dough with RuBisCO, in comparison to pea protein-enriched and gluten-enriched doughs. The protein quality and digestibility of these enriched doughs were analysed through dough characterization, in vitro digestion experiments and biochemical analysis of digesta. Our findings indicate that an enrichment at 10% of RuBisCO or pea proteins improves the chemical score and the in vitro PDCAAS (IV-PDCAAS) score of wheat dough as compared to the control dough. Digestibility assays suggest that RuBisCO introduction modifies the protein hydrolysis kinetics: the nitrogen release is lower during gastric digestion but larger during intestinal digestion than other samples. The analysis of the protein composition of the soluble and insoluble parts of digesta, using size-exclusion chromatography, reveals that the protein network in RuBisCO-enriched dough is more resistant to gastric hydrolysis than the ones of other doughs. Indeed, non-covalently bound peptides and disulfide-bound protein aggregates partly composed of RuBisCO subunits remain insoluble at the end of the gastric phase. The digestion of these protein structures is then mostly performed during the intestinal phase. These results are also discussed in relation to the digestive enzymatic cleavage sites, the presence of potential enzyme inhibitors, the protein aggregation state and the secondary structures of the protein network in each dough type.

Examination of Primary and Secondary Metabolites Associated with a Plant-Based Diet and Their Impact on Human Health

The consumption of plant-based diets has become a burgeoning trend, and they are increasingly consumed globally owing to their substantial energy intensity and dietetic advantages. Plants possess numerous bioactive components that have been recognized to exhibit manifold health-promoting assets. Comprehension of the synthesis of these primary and secondary metabolites by plants and their method of action against several chronic illnesses is a significant requirement for understanding their benefits to human health and disease prevention. Furthermore, the association of biologically active complexes with plants, humans, disease, medicine, and the underlying mechanisms is unexplored. Therefore, this review portrays various bioactive components derived from plant sources associated with health-promoting traits and their action mechanisms. This review paper predominantly assembles proposed plant-derived bioactive compounds, postulating valuable evidence aimed at perceiving forthcoming approaches, including the selection of potent bioactive components for formulating functional diets that are effective against several human disorders. This meticulous evidence could perhaps provide the basis for the advanced preemptive and therapeutic potential promoting human health. Hence, delivery opens possibilities for purchasers to approach the lucrative practice of plants as a remedy, produce novel products, and access new marketplaces.

Improved in vitro gastrointestinal digestion protocol mimicking brush border digestion for the determination of the Digestible Indispensable Amino Acid Score (DIAAS) of different food matrices

The Digestible Indispensable Amino Acid Score (DIAAS) is the new gold standard method for the assessment of protein nutritional quality. The DIAAS is evaluated with in vivo models, that are complex, constraining and costly. There is still no established method to assess it in vitro. In this study, we proposed to add a jejunal-ileal digestion phase to the standardized in vitro gastrointestinal digestion protocol developed by the International Network of Excellence on the Fate of Food in the Gastrointestinal Tract (INFOGEST protocol) to mimic brush border digestion and to enable DIAAS assessment in vitro in a more physiologically relevant manner. This jejunal-ileal digestion phase was performed with a porcine intestinal aminopeptidase as an alternative to brush border membrane extract, which is more difficult to obtain in a standardized way. This modified INFOGEST protocol was applied to various food matrices (faba bean, pea and soy flours, whey protein isolate and caseins) and the results were compared to published in vivo data to assess the model's physiological relevance. The addition of the jejunal-ileal digestion phase lead to a significant (p < 0.05) increase of 31 and 29 % in free and total amino acid digestibility, respectively, and of 83 % on average for the in vitro DIAAS values for all food matrices. Although the in vitro DIAAS remained underestimated compared to the in vivo ones, a strong correlation between them was observed (r = 0.879, p = 0.009), stating the relevance of this last digestion phase. This improved digestion protocol is proposed as a suitable alternative to evaluate the DIAAS in vitro when in vivo assays are not applicable.

Comparative structural, digestion and absorption characterization of three common extruded plant proteins

Extruded plant proteins, also known as textured vegetable proteins (TVPs), serve as vital components in plant-based meat analogue, yet their structural and nutritional characteristics remain elusive. In this study, we examined the impact of high-moisture (HM) and low-moisture (LM) extrusion on the structures, digestion and absorption of three types of plant proteins. Extrusion transformed plant proteins from spherical to fibrous forms, and formed larger aggregate particles. It also led to the disruption of original disulfide bonds and hydrophobic interactions within protein molecules, and the formation of new cross-links. Intriguingly, compared to native plant proteins, TVPs' α-helix/β-sheet values decreased from 0.68 to 0.69 to 0.56-0.65. Extrusion increased the proportion of peptides shorter than 1 kD in digesta of TVPs by 1.44-23.63%. In comparison to unextruded plant proteins, TVPs exhibited lower content of free amino acids in cell transport products. Our findings demonstrated that extrusion can modify protein secondary structure by diminishing the α-helix/β-sheet value, and impact protein tertiary structure by reducing disulfide bonds and hydrophobic interactions, promoting the digestion and absorption of plant proteins. These insights offer valuable scientific backing for the utilization of extruded plant-based proteins, bolstering their role in enhancing the palatability and nutritional profile of plant-based meat substitutes.

In vitro digestibility of proteins from red seaweeds: Impact of cell wall structure and processing methods

This study aimed to assess the nutritional quality and digestibility of proteins in two red seaweed species, Gelidium corneum and Gracilaropsis longissima, through the application of in vitro gastrointestinal digestions, and evaluate the impact of two consecutive processing steps, extrusion and compression moulding, to produce food snacks. The protein content in both seaweeds was approximately 16 %, being primarily located within the cell walls. Both species exhibited similar amino acid profiles, with aspartic and glutamic acid being most abundant. However, processing impacted their amino acid profiles, leading to a significant decrease in labile amino acids like lysine. Nevertheless, essential amino acids constituted 35-36 % of the total in the native seaweeds and their processed products. Although the protein digestibility in both seaweed species was relatively low (<60 %), processing, particularly extrusion, enhanced it by approximately 10 %. Interestingly, the effect of the different processing steps on the digestibility varied between the two species. This difference was mainly attributed to compositional and structural differences. G. corneum exhibited increased digestibility with each processing step, while G. longissima reached maximum digestibility after extrusion. Notably, changes in the amino acid profiles of the processed products affected adversely the protein nutritional quality, with lysine becoming the limiting amino acid. These findings provide the basis for developing strategies to enhance protein quality in these seaweed species, thereby facilitating high-quality food production with potential applications in the food industry.

A comparative study of the digestion behavior and functionality of protein from chia (Salvia hispanica L.) ingredients and protein fractions

Protein derived from chia (Salvia hispanica L.), characterized by a balanced amino acid composition, represents a potentially healthier and environmentally friendly alternative poised for innovation within the plant-based food sector. It was hypothesized that the growing location of chia seeds and processing techniques used might influence protein digestion patterns, which in turn could affect the biological functions of the digestion products. To examine this hypothesis, we assessed the gastrointestinal fate of degummed-defatted flour (DDF), protein concentrate (PC), and isolated albumin (Alb) and globulin (Glo) fractions. Furthermore, we compared the antioxidant and anti-inflammatory activities of the resulting digesta by means of in vitro and cellular assays. Post-gastrointestinal digestion, the PC exhibited elevated levels of soluble protein (7.6 and 6.3 % for Mexican and British PC, respectively) and peptides (24.8 and 27.9 %, respectively) of larger molecular sizes compared to DDF, Alb, and Glo. This can be attributed to differences in the extraction/fractionation processes. Leucine was found to be the most prevalent amino acids in all chia digesta. Such variations in the digestive outcomes of chia protein components significantly influenced the bioactivity of the intestinal digestates. During gastrointestinal transit, British Glo exhibited the best reactive oxygen species (ROS) inhibition activity in oxidative-stressed RAW264.7 macrophages, while Mexican digesta outperformed British samples in terms of ROS inhibition within the oxidative-stressed Caco-2 cells. Additionally, both Mexican and British Alb showed effectively anti-inflammatory potential, with keratinocyte chemoattractant (KC) inhibition rate of 82 and 91 %, respectively. Additionally, Mexican PC and Alb generally demonstrated an enhanced capacity to mitigate oxidative stress and inflammatory conditions in vitro. These findings highlight the substantial potential of chia seeds as functional food ingredients, resonating with the shifting preferences of health-conscious consumers.

Modulation of soy protein immunoreactivity by different matrix structures of lactic acid bacterium-induced soy protein gels: Epitope destruction during in vitro gastroduodenal digestion and absorption

Soy allergy is a common health problem. Food structure may change the gastroduodenal digestion and absorption of soy proteins, thus leading to the modulation of the immunoreactivity of soy proteins. In this study, lactic acid bacterium (LAB)-fermented soy protein isolates (FSPIs) were prepared at four concentrations (0.2 %-5.0 %, w/v) to present various matrix structures (nongel, NG; weak gel, WG; medium gel, MG; and firm gel, FG) and subjected to in vitro dynamic gastroduodenal digestion model. The results of sandwich enzyme-linked immunosorbent and human serum IgE binding capacity assays demonstrated that FSPI gels, especially the FSPI-MG/WG digestates obtained at the early and medium stages of duodenal digestion (D-5 and D-30), possessed greater potency in immunoreactivity reduction than FSPI-NG and reduced to 1.9 %-68.3 %. The transepithelial transport study revealed that the immunoreactivity of FSPI-MG/WG D-5 and D-30 digestates decreased through the stimulation of interferon-γ production and the induction of dominant Th1/Th2 differentiation. Peptidomics and bioinformatics analyses illustrated that compared with FSPI-NG, the FSPI-gel structure promoted the epitope degradation of the major allergens glycinin G2/G5, β-conglycinin α/β subunit, P34, lectin, trypsin inhibitor, and basic 7S globulin. Spatial structure analysis showed that FSPI-gel elicited an overall promotion in the degradation of allergen epitopes located in interior and exterior regions and was dominated by α-helix and β-sheet secondary structures, whereas FSPI-MG/WG promoted the degradation of epitopes located in the interior region of glycinin/β-conglycinin and exterior region of P34/basic 7S globulin. This study suggested that the FSPI-gel structure is a promising food matrix for decreasing the allergenic potential of allergenic epitopes during gastroduodenal digestion and provided basic information on the production of hypoallergenic soy products.

Transglycosylation catalysed by Caco-2 membrane disaccharidases: A new approach to understand carbohydrates digestibility

Under appropriate experimental conditions, some glycoside hydrolases can catalyze transglycosylation reactions; a hypothesis associated with this is that the glycosidic linkages formed will be preferentially hydrolyzed under optimal conditions. Therefore, the hydrolytic and transglycosylation activities of isolated membranes from differentiated Caco-2 cells on sucrose, maltose and isomaltulose were evaluated. After the enzymatic reactions, the di- and trisaccharides obtained were identified by gas chromatography coupled to a mass spectrometer. Differentiated Caco-2 cell membranes exerted hydrolytic and transglycosylation activities towards the studied disaccharides. The obtained di- and trisaccharides were detected for the first time using human cell models. Due to the absence of maltase-glucoamylase complex (MGAM) in Caco-2 cells, and the known hydrolytic activity of sucrase-isomaltase (SI) towards sucrose, maltose and isomaltulose, it is plausible that the glycosidic linkages obtained after the transglycosylation reaction, mainly α-glucosyl-fructoses and α-glucosyl-glucoses, were carried out by SI complex. This approach can be used as a model to explain carbohydrate digestibility in the small intestine and as a tool to design new oligosaccharides with low intestinal digestibility.

Comparison of protein quality and digestibility between plant-based and meat-based burgers

Nowadays, consumers are increasingly inclined toward plant-based meat analogues for sake of food security, safety, and sustainability. This growing interest, not only from consumers but also from food companies, brought the offer on the market to be wide and vast. From our previous study it emerged that the market supply, especially the Italian one, is diversified both in terms of protein sources and nutrient content. Although these products are increasingly consumed, for most of the meat analogues today on the market, little is still known about their actual protein quality and digestibility. To fill this gap, in this study different commercial plant-based burgers (2 soy-based and 2 pea-based) were selected and compared to two beef burgers, as controls, in terms of protein quality and digestibility. The findings of this study demonstrated the essential amino acidic profile lacks lysine for almost all burgers (including the meat-based ones) compared to the amino acid scoring pattern set by FAO/WHO (for older children and adults), even if the sum of essential amino acids was within the range of sufficiency. All samples showed good initial protein integrity with low hydrolysis (above 6%) and percentage of D-enantiomers (above 15%). The study of the digestibility, performed by the validated INFOGEST in vitro model, showed better protein solubilisation in the case of meat burgers (63 ± 3% and 61 ± 8%), but a good digestibility also in the case of plant-based ones (from 55% to 40%). The degree of hydrolysis of the solubilised proteins was very high in all samples (from 65% to 40%) indicating a very good protein accessibility to digestive enzymes. The analysis of the peptide fraction of digestates indicated a high prevalence of collagen proteins in beef burgers and of reserve proteins in plant-based burgers. This study showed that the differences between these products are mostly dependent on the quality of the raw materials used, rather than on the vegetal or animal protein source. Therefore, to have a product with a good protein quality and digestibility, independently from the protein origin, the consumer needs to make an accurate choice, carefully reading the ingredient list.

Enhancing Bioaccessibility of Plant Protein Using Probiotics: An In Vitro Study

As plant-based diets become more popular, there is an interest in developing innovations to improve the bioaccessibility of plant protein. In this study, seven probiotic strains (Bifidobacterium animalis subsp. lactis B420, B. lactis Bl-04, Lactobacillus acidophilus NCFM, Lacticaseibacillus rhamnosus HN001, Lacticaseibacillus paracasei subsp. paracasei Lpc-37, Lactiplantibacillus plantarum Lp-115, and Lactococcus lactis subsp. lactis Ll-23) were evaluated for their capacity to hydrolyze soy and pea protein ingredients in an in vitro digestion model of the upper gastrointestinal tract (UGIT). Compared to the control digestion of protein without a probiotic, all the studied strains were able to increase the digestion of soy or pea protein, as evidenced by an increase in free α-amino nitrogen (FAN) and/or free amino acid concentration. The increase in FAN varied between 13 and 33% depending on the protein substrate and probiotic strain. The survival of probiotic bacteria after exposure to digestive fluids was strain-dependent and may have affected the strain's capacity to function and aid in protein digestion in the gastrointestinal environment. Overall, our results from the standardized in vitro digestion model provide an approach to explore probiotics for improved plant protein digestion and bioaccessibility of amino acids; however, human clinical research is needed to evaluate the efficacy of probiotics on amino acid absorption and bioavailability in vivo.

Sunflower and Palm Kernel Meal Present Bioaccessible Compounds after Digestion with Antioxidant Activity

Sunflower (Helianthus annuus L.) and African palm kernel (Elaeis guineensis Jacq.) are among the most cultivated in the world regarding oil extraction. The oil industry generates a large amount of meal as a by-product, which can be a source of nutrients and bioactive compounds. However, the physiological effects of bioactive compounds in such matrices are only valid if they remain bioavailable and bioactive after simulated gastrointestinal digestion. This study evaluated the chemical composition and antioxidant and prebiotic potential of de-oiled sunflower (DS) and de-oiled palm kernel (DP) meal after in vitro digestion. The DS sample had the highest protein content and the best chemical score, in which lysine was the limiting amino acid. Digested samples showed increased antioxidant activity, measured by in vitro methods. The digested DS sample showed a better antioxidant effect compared to DP. Moreover, both samples managed to preserve DNA supercoiling in the presence of the oxidizing agent. The insoluble fractions after digestion stimulated the growth of prebiotic bacterium, similar to inulin. In conclusion, simulated gastrointestinal digestion promoted in both matrices an increase in protein bioaccessibility and antioxidant capacity, pointing to a metabolic modulation favorable to the organism.

Does sourdough bread provide clinically relevant health benefits?

During the last decade, scientific interest in and consumer attention to sourdough fermentation in bread making has increased. On the one hand, this technology may favorably impact product quality, including flavor and shelf-life of bakery products; on the other hand, some cereal components, especially in wheat and rye, which are known to cause adverse reactions in a small subset of the population, can be partially modified or degraded. The latter potentially reduces their harmful effects, but depends strongly on the composition of sourdough microbiota, processing conditions and the resulting acidification. Tolerability, nutritional composition, potential health effects and consumer acceptance of sourdough bread are often suggested to be superior compared to yeast-leavened bread. However, the advantages of sourdough fermentation claimed in many publications rely mostly on data from chemical and in vitro analyzes, which raises questions about the actual impact on human nutrition. This review focuses on grain components, which may cause adverse effects in humans and the effect of sourdough microbiota on their structure, quantity and biological properties. Furthermore, presumed benefits of secondary metabolites and reduction of contaminants are discussed. The benefits claimed deriving from in vitro and in vivo experiments will be evaluated across a broader spectrum in terms of clinically relevant effects on human health. Accordingly, this critical review aims to contribute to a better understanding of the extent to which sourdough bread may result in measurable health benefits in humans.

Combination of three null mutations affecting seed protein accumulation in pea (Pisum sativum L.) impacts positively on digestibility

The presence of so-called anti-nutritional factors can reduce the bioavailability of nutrients following consumption of seeds which are otherwise an excellent source of proteins, carbohydrates and micronutrients. Among the proteins associated with negative effects on quality in pea (Pisum sativum L.) seeds are lectin, pea albumin 2 (PA2) and trypsin inhibitors (TI). Here we have investigated the impact of these proteins on protein digestibility and amino acid availability, using naturally occurring and derived mutant lines of pea lacking these proteins. The mutations were stacked to generate a triple mutant which was compared with a wild-type progenitor and a line lacking the major seed trypsin inhibitors alone. In vitro digestions following the INFOGEST protocol revealed significant differences in the degree of hydrolysis, protein profile and apparent amino acid availability among the pea variants. Proteins resistant to digestion were identified by MALDI-TOF mass spectrometry and amino acid profiles of digested samples determined. The results indicate that pea seeds lacking certain proteins can be used in the development of novel foods which have improved protein digestibility, and without negative impact on seed protein concentration or yield.

Sourdough "Biga" Fermentation Improves the Digestibility of Pizza Pinsa Romana: An Investigation through a Simulated Static In Vitro Model

Baked goods manufacturing parameters and fermentation conditions interfere with the nutrients content and affect their gastrointestinal fate. Pinsa Romana is a type of pizza that, recently, has been commercially rediscovered and that needed elucidation from a nutritional and digestibility perspective. In this study, six types of Pinsa Romana (five made with indirect method and one produced with straight dough technology) were characterized for their biochemical and nutritional features. Several variables like indirect (biga) Pinsa Romana production process, fermentation time and use of sourdough were investigated. The Pinsa Romana made with biga including sourdough and fermented for 48 h at 16 °C ((PR_48(SD)) resulted in the lowest predicted glycemic index, in the highest content of total peptides, total and individual free amino acids and gamma-amino butyric acid (GABA), and in the best protein quality indexes (protein efficiency ratio and nutritional index). The static in vitro digestion showed that the digesta from PR_48(SD) confirmed a reduced in vitro glycemic response after intake, and it showed a lower bioavailability of hydrophilic peptides. Furthermore, the inclusion of sourdough in biga enhanced the bioavailability of protein-related end-products including human health promoting compounds such as essential amino acids.

Comparative Study on Hydrolysis, Physicochemical and Antioxidant Properties in Simulated Digestion System between Cooked Pork and Fish Meat

Pork and grass carp are commonly consumed animal protein sources, classified as red meat and white meat, respectively. This study aimed to better understand the differences in digestive behavior, nutrition, and functionality during digestion between these two types of meat after fat removal. The results showed that grass carp was more easily digested than pork, with a higher degree of hydrolysis, a smaller protein particle size, and a greater release of oligopeptides and amino acids (p < 0.05). During gastric digestion, all α-helix structures were destroyed, and the effect of the whole digestion process on the secondary and tertiary structure of pork protein was greater than that of grass carp. The antioxidant properties of the digestive fluids from the two types of meat showed different strengths in various assays, but the correlation analysis revealed that TCA-soluble peptides, random coil content, and particle size significantly influenced both types of meat. These findings provide new insights into the structural state and antioxidant properties of protein in meat digestion, which contribute to our understanding of the nutritional value of pork and grass carp.

Alternations in the multilevel structures of chickpea protein during fermentation and their relationship with digestibility

This study investigated the effects of fermentation on in vitro protein digestibility of chickpeas and their relationship with the variations of multilevel structures of chickpea protein. The results showed that lactobacillus fermentation not only increased the solubility of chickpea protein but also enhanced the hydrolysis of protein during gastric and intestinal digestion by altering the multilevel structures of chickpea protein. The degree of hydrolysis, free amino acid content, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that macromolecule chickpea protein was hydrolyzed during fermentation. Raman and UV spectroscopy scans indicated that the α-helix content increased while the content of β-sheet in chickpea protein dropped significantly after fermentation. As for fermented chickpea protein, the aromatic acid residues were gradually more exposed than the unfermented chickpea protein, and the intramolecular disulfide bond was generally converted to the intermolecular form. Our findings showed that fermentation changed the multilevel structures of chickpea protein, degrading spherical structures into looser states that were more responsible for their effective hydrolysis during digestion. Furthermore, better digestibility of chickpea protein would stimulate the use of chickpea fermentation in food products.

Chemical Characterization of White Lupin (Lupinus albus) Flour Treated by Extrusion Cooking and Aqueous Debittering Processes

Lupin is a very nutritious legume with high levels of protein and fiber, but it also contains quinolizidine alkaloids which, depending on the species, can accumulate to toxic levels. The objective of this work was to evaluate the white lupin chemical composition, due to the effects of different processes (aqueous debittering, extrusion cooking, and reactive extrusion), aiming at reducing total alkaloids, preserving fibers, and increasing in vitro protein digestibility. Regarding raw material, the aqueous process reduced significantly total alkaloids (-93.87%), increased dietary fiber (+22.03%), and increased protein digestibility (+6.73%), whereas the extrusion processes were inefficient to reduce alkaloids (< -3.70%) and reduced the dietary fiber content, the reduction being more severe during reactive extrusion (-75.36%). Protein digestibility was improved by extrusion cooking (+3.07%), while the reactive extrusion reduced digestibility (-12.50%). Electrophoresis and quantification of soluble proteins and aromatic amino acids confirmed the high digestibility index, staying only the γ-conglutin fraction in the digested samples evaluated by SDS-PAGE. The aqueous process proved to be the best option, as it reduces the alkaloid content to safe levels and improves the protein digestion of white lupin flour.

Comparison of protein in vitro digestibility under adult and elderly conditions: The case study of wheat, pea, rice, and whey proteins

In this study an in vitro static digestion method mimicking the elderly gastrointestinal conditions was designed by adapting the physiological parameters described in the INFOGEST standardized static in vitro digestion protocol, i.e., pH, digestive phase duration, concentrations of enzymes and bile salts, to the aged GI transit. The digestibility of proteins from different sources (pea, rice, wheat, and milk whey) was then assessed. Protein digestive behaviour was monitored after gastric and intestinal phases by BCA assay and SDS-PAGE to assess protein hydrolysis both from a quantitative and a qualitative point of view. Digested samples were also analysed for physical characteristics in terms of particle size and zeta potential. Data acquired under elderly gastrointestinal conditions were compared to those obtained by using the INFOGEST protocol designed to study adult digestion. Results clearly showed that the elderly gastrointestinal conditions deeply affected proteolysis leading to a general reduction of protein digestibility in comparison to the adult model. The proteolysis extent depended on the protein source with whey and rice proteins showing about 20% reduction using the model mimicking the elderly gut, followed by pea (about 10% reduction) and wheat (about 4% reduction) proteins. The knowledge of protein digestibility under elderly gastrointestinal conditions generated in this study could be useful in the attempt to develop age-tailored products.

Legume Protein Extracts: The Relevance of Physical Processing in the Context of Structural, Techno-Functional and Nutritional Aspects of Food Development

Legumes are sustainable protein-rich crops with numerous industrial food applications, which give them the potential of a functional food ingredient. Legume proteins have appreciable techno-functional properties (e.g., emulsification, foaming, water absorption), which could be affected along with its digestibility during processing. Extraction and isolation of legumes’ protein content makes their use more efficient; however, exposure to the conditions of further use (such as temperature and pressure) results in, and significantly increases, changes in the structural, and therefore functional and nutritional, properties. The present review focuses on the quality of legume protein concentrates and their changes under the influence of different physical processing treatments and highlights the effect of processing techniques on the structural, functional, and some of the nutritional, properties of legume proteins.

Assessment of In Vitro Digestive Behavior of Lactic-Acid-Bacteria Fermented Soy Proteins: A Study Comparing Colloidal Solutions and Curds

This study investigated the effect of lactic-acid-bacteria fermentation on the microstructure and gastrointestinal digestibility of soy proteins using a digestomics approach. Fermented soy protein isolates (FSPIs) under varied fermentation-terminal pH demonstrated a colloidal solution (FSPI-7.0/6.0) or yogurt-like curd (FSPI-5.0/4.0) state. Cryo-electron microscopy figures demonstrated the loosely stacked layer of FSPI-7.0/6.0 samples, whereas a denser gel network was observed for FSPI-5.0/4.0 samples. Molecular interactions shifted from dominant ionic bonds to hydrophobic forces and disulfide bonds. The gastric/intestinal digestion demonstrated that the curd samples afforded a significantly low particle size and high-soluble protein and peptide contents in the medium and late digestive phases. A peptidomics study showed that the FSPI-6.0 digestate at early intestinal digestion had a high peptidome abundance, whereas FSPI curd digestates (FSPI-5.0/4.0) elicited a postponed but more extensive promotion during medium and late digestion. Glycinin G2/G4 and β-conglycinin α/α' subunits were the major subunits promoted by FSPI-curds. The spatial structures of glycinin G2 and β-conglycinin α subunits demonstrated variations located in seven regions. Glycinin G2 region 6 (A349-K356) and β-conglycinin α subunit region 7 (E556-E575), which were located at the interior of the 3D structure, were the key regions contributing to discrepancies at the late stage.

Characterization and Cellular Uptake of Peptides Derived from In Vitro Digestion of Meat Analogues Produced by a Sustainable Extrusion Process

Whether proteins in meat analogues (MAs) have the ability to provide equivalent nutrition as those in animal meat remains unknown. Herein, a MA was produced by high-moisture extrusion using soy and wheat proteins. The physicochemical properties, in vitro digestion, and cellular uptake of the released peptides were systematically compared between the MA and the chicken breast (CB). The MA showed a higher hardness but a lower degree of texturization than the CB. After simulated digestion, soluble peptides in the MA had a higher molecular weight and higher hydrophobicity. No observable cytotoxicity or inflammatory response to Caco-2 cells was found for both MA and CB digests. The former exhibited less permeability of peptides across Caco-2 cells. Liquid chromatography with tandem mass spectrometry found that the identified peptides in MA and CB digests contained 7-30 and 7-20 amino acid residues, respectively, and they became shorter after cellular transportation. The amino acid composition showed fewer essential and non-essential amino acids in the MA permeate than in the CB permeate.

Digestion characteristics of quinoa, barley and mungbean proteins and the effects of their simulated gastrointestinal digests on CCK secretion in enteroendocrine STC-1 cells

The demand for plant-based proteins has been rapidly increasing due to sustainability, ethical and health reasons. The present study aimed to investigate the digestion characteristics of three plant proteins (quinoa, barley and mungbean) based on an in vitro digestion model and the effect of their simulated gastrointestinal digests on satiety hormone cholecystokinin (CCK) secretion in enteroendocrine STC-1 cells. The nitrogen distribution in the digestion process, the relative molecular weight (MW) of peptides and the amino acid composition in simulated gastrointestinal digests were characterized. Quinoa protein had the highest proportion of soluble nitrogen after gastrointestinal digestion (85.79%), followed by barley protein (74.98%) and mungbean protein (64.14%), suggesting that quinoa protein was more easily digested than barley and mungbean proteins. The peptides but not free amino acids were the main components in the gastrointestinal digests of quinoa, barley, and mungbean proteins. The gastrointestinal digest of quinoa protein had a well balanced amino acid pattern, whereas that of barley protein was lacking Lys, and that of the mungbean protein was short of sulfur amino acids (Phe + Tyr) but rich in Lys. In terms of the ability to stimulate CCK secretion, the gastrointestinal digest of barley protein had a strong stimulatory effect on CCK secretion, while that of quinoa and mungbean proteins had only a weak stimulatory effect. After pretreatment with a specific calcium-sensing receptor (CaSR) antagonist NPS 2143, CCK secretion induced by the barley protein digest was greatly suppressed, indicating that CaSR was involved in barley protein digest-induced CCK secretion. These results show that quinoa protein has good nutritional quality, while barley protein is an excellent plant protein source to stimulate CCK secretion and has a potential application as a dietary supplement for obesity management.

Production, bioactivities and bioavailability of bioactive peptides derived from walnut origin by-products: a review

Walnut-origin by-products obtained from walnut oil extraction industry are high in proteins with various physiological functions and pharmacological properties and an extensive potential for usage in producing bioactive peptides. This review presents the current research status of bioactive peptides derived from walnut by-products, including preparation, separation, purification, identification, bioactivities, and bioavailability. A plethora of walnut peptides with multiple biological activities, including antioxidative, antihypertensive, neuroprotective, antidiabetic, anticancer, and antihyperuricemia activities, were obtained from walnut-origin by-products by enzymatic hydrolysis, fermentation, and synthesis. Different bioactive peptides show various structural characteristics and amino acid composition due to their diverse mechanism of action. Furthermore, walnut protein and its hydrolysate present a high bioavailability in human gastrointestinal digestive system. Improving the bioavailability of walnut peptides is needful in the development of walnut industry. However, future research still needs to exploit energy conservation, high efficiency, environmentally friendly and low-cost production method of walnut bioactive peptide. The molecular mechanisms of different bioactive walnut peptides still need to be explored at the cell and gene levels. Additionally, the digestion, absorption, and metabolism processes of walnut peptides are also the focus of future research.

Comparing the effects of hydrostatic high-pressure processing vs holder pasteurisation on the microbial, biochemical and digestion properties of donor human milk

In this study, hydrostatic high-pressure processing (HHP), a non-thermal pasteurisation method, was used to achieve the microbiological safety of donor human milk. After HHP, no bacteria were detected in human milk processed at 400 MPa for 5 min. Activities of a selection of bioactive components, including lysozyme, xanthine oxidase, lactoperoxidase, immunoglobulin A, lactoferrin, lipoprotein lipase and bile salt-stimulated lipase, did not decrease significantly. This study further investigated the gastrointestinal digestion kinetics of HoP and HHP milk compared with raw human milk, using an in vitro static infant digestion model. After 60 min of 'gastric digestion', the microstructure and protein profile of HHP milk samples were more similar to raw milk samples than HoP milk samples. Overall, HPP showed a better retention in milk nutrients and closer digestion behavior than that of HoP.

Effect of Fractionation and Processing Conditions on the Digestibility of Plant Proteins as Food Ingredients

Plant protein concentrates and isolates are used to produce alternatives to meat, dairy and eggs. Fractionation of ingredients and subsequent processing into food products modify the techno-functional and nutritional properties of proteins. The differences in composition and structure of plant proteins, in addition to the wide range of processing steps and conditions, can have ambivalent effects on protein digestibility. The objective of this review is to assess the current knowledge on the effect of processing of plant protein-rich ingredients on their digestibility. We obtained data on various fractionation conditions and processing after fractionation, including enzymatic hydrolysis, alkaline treatment, heating, high pressure, fermentation, complexation, extrusion, gelation, as well as oxidation and interactions with starch or fibre. We provide an overview of the effect of some processing steps for protein-rich ingredients from different crops, such as soybean, yellow pea, and lentil, among others. Some studies explored the effect of processing on the presence of antinutritional factors. A certain degree, and type, of processing can improve protein digestibility, while more extensive processing can be detrimental. We argue that processing, protein bioavailability and the digestibility of plant-based foods must be addressed in combination to truly improve the sustainability of the current food system.

In vitro simulated semi-dynamic gastrointestinal digestion: evaluation of the effects of processing on whey proteins digestibility and allergenicity

The effect of thermal processing on digestibility of milk proteins should be better understood as this can greatly affect their immunoreactivity. The aim of this study was to evaluate the...

The in-vitro digestion behaviors of micellar casein acting as wall materials in spray-dried microparticles: The relationships between colloidal calcium phosphate and the release of loaded blueberry anthocyanins

Micellar casein (MC) is a natural carrier for delivering various bioactive substances, and its gastrointestinal digestion behavior has an important impact on the loaded materials. Studies have shown that the digestion behavior of MC is dominated by colloidal calcium phosphate (CCP) in micelle structure. In this paper, The MCs with different CCP levels were used as the carriers to prepare spray-dried microparticles loaded with blueberry anthocyanins (ACNs), then the release of ACNs during digestion was investigated. The results found that the microparticles with less CCP showed the faster dissolution and quicker protein hydrolysis, which caused weaker curd ability. The coagulation was believed as the critical issue to influence the digestion and release behaviors. Therefore, lowering CCP resulted in significantly more ACNs released. This study demonstrated the possibility of using CCP levels to control MC digestion behaviors, which can further determine the release of loaded bioactive substances in casein-based delivery systems.

Mechanism of low-frequency and high-frequency ultrasound-induced inactivation of soy trypsin inhibitors

In this study, the effect of ultrasonic frequency and power on the inactivation of soy trypsin inhibitors (TIs) was investigated to explore the ultrasound-induced inactivation mechanism. It was observed that 20 kHz and 355 kHz ultrasound have better inactivation efficiency than 1056 kHz. First-order rate constants for the inactivation process were obtained, which increased with increasing ultrasonic power at both 20 kHz and 355 kHz. For 20 kHz ultrasound, the formation of TI aggregates resulting from the physical effects of acoustic cavitation decreased the interactions between the active sites of TIs and trypsin, thus reducing the TI activity. For 355 kHz ultrasound, most of the methionine in the TIs was oxidised within 5 mins, resulting in a faster reduction of TI activity. Subsequent aggregation of TIs resulted in further TI inactivation. SDS-PAGE showed that neither disulphide bonds nor CC coupling were involved in the formation of aggregates.