Gastric Digestion Research Articles

Ultrasonic-Assisted Extraction and Gastrointestinal Digestion Characteristics of Polysaccharides Extracted from Mallotus oblongfolius

The polysaccharides were extracted from the leaves of Mallotus oblongifolius (MO) using an ultrasonic-assisted extraction method in this study. The main variables affecting the yield of polysaccharides extracted from Mallotus appallatus (MOPS) were identified and optimized while concurrently investigating its antioxidant capacity, hypoglycemic activity, and digestive properties. The results indicated that the optimal ultrasound-assisted extraction of MOPS involved an ultrasound power of 200 W, a liquid-to-solid ratio of 25:1 (mL:g), an extraction temperature of 75 °C, and an ultrasound time of 45 min, leading to an extraction yield of (7.36 ± 0.45)% (m/m). The MOPS extract exhibited significant scavenging activity against DPPH and ABTS radicals with IC50 values of (25.65 ± 0.53) μg/mL and (100.38 ± 0.38) μg/mL, respectively. Furthermore, it effectively inhibited the enzymatic activities of α-glucosidase and α-amylase with IC50 values of (2.27 ± 0.07) mg/mL and (0.57 ± 0.04) mg/mL, respectively. The content of MOPS remained relatively stable in the stomach and small intestine; however, their ability to scavenge DPPH radicals and ABTS radicals and exhibit reducing power was attenuated, and the inhibition of α-amylase and α-glucosidase activity was diminished. In conclusion, the ultrasonic extraction of MOPS showed feasibility and revealed antioxidant and hypoglycemic effects. However, the activities were significantly reduced after gastric and small intestinal digestion despite no significant change in the MOPS content.

Effect of pH on the soybean whey protein–gum arabic emulsion delivery systems for curcumin: Emulsifying, stability, and digestive properties

A novel curcumin (CUR) delivery system was developed using soybean whey protein (SWP)-based emulsions, enhanced by pH-adjustment and gum arabic (GA) modification. Modulating electrostatic interactions between SWP and GA at oil/water interface, pH provides favorable charging conditions for stable distribution between droplets. GA facilitated the SWP form a stable interfacial layer that significantly enhanced the emulsifying properties and CUR encapsulation efficiency of the system at pH 6.0, which were 90.15 ± 0.67%, 870.53 ± 3.22 m2/g and 2157.62 ± 115.31%, respectively. Duncan's test revealed significant improvements in thermal, UV, oxidative, and storage stabilities of CUR (P < 0.05). At pH 6.0, GA effectively protected CUR by inhibiting SWP degradation during gastric digestion and promoting the release of CUR by decreasing steric hindrance with oil droplets during intestinal digestion, achieving the highest CUR bioaccessibility (69.12% ± 0.28%) based on Duncan's test. The SWP-GA-CUR emulsion delivery system would be a novel carrier for nutrients.

In vitro gastrointestinal digestion of cow’s and sheep’s dairy products: Impact of species and structure

Sheep’s milk (SM) is known to differ from cow’s milk (CM) in nutritional composition and physicochemical properties, which may lead to different digestion behaviours. This work aimed to investigate the impact of the species (cow vs sheep) and the structure (milk vs yogurt) on the digestion of dairy products. Using an in vitro static gastrointestinal digestion model, CM, SM, cow’s milk yogurt (CY) and sheep’s milk yogurt (SY) were compared on particle size evolution, microscopic observations, degree of lipolysis, degree of proteolysis, specific protein degradation and calcium bioaccessibility. Species and structure affected particle size evolution during the gastric phase resulting in smaller particles for yogurts compared to milks as well as for CM products compared to SM products. Species impacted lipid composition and lipolysis, with SM products presenting higher short/medium-chain fatty acids content and higher intestinal degree of lipolysis. Proteolysis was influenced by structure, with milks showing higher intestinal degree of proteolysis compared to yogurts. Caseins were digested faster in CM, ⍺-lactalbumin was digested faster in SM despite its higher concentration, and during gastric digestion β-lactoglobulin was more degraded in CM products compared to SM products and more in yogurts compared to milks. Lastly, SM products released more bioaccessible calcium than CM products. In conclusion, species (cow vs sheep) impacted more the digestion compared to the structure (milk vs yogurt). In fact, SM was different from CM mainly due to a denser protein network that might slow down the accessibility of the enzyme to its substrate which induce a delay of gastric disaggregation and thus lead to slower the digestion of the nutrients.

Comparison of protein digestibility of human milk and infant formula using the INFOGEST method under infant digestion conditions.

Many improvements have been made to bring infant formula (IF) closer to human milk (HM) regarding its nutritional and biological properties. Nevertheless, the protein components of HM and IF are still different, which may affect their digestibility. This study aimed to evaluate and compare the protein digestibility of HM and IF using the infant INFOGEST digestion method. Pooled HM and a commercial IF were subjected to the infant INFOGEST method, which simulates the physiological digestion conditions of infants, with multiple directions, i.e. the curd state, gel images of SDS-PAGE, molecular weight distribution, free amino acid concentrations and in vitro protein digestion rate. HM underwent proteolysis before digestion and tended to have a higher protein digestion rate with finer curds during gastric digestion, than the IF. However, multifaceted analyses showed that the protein digestibility of HM and IF was not significantly different after gastrointestinal digestion. In conclusion, the infant INFOGEST method showed that the digestibility of HM and IF proteins differed to some extent before digestion and after gastric digestion, but not at the end of gastrointestinal digestion. The findings of this study will contribute to the refinement of IF with better protein digestibility in infant stomach.

Yeast protein: In vivo gastrointestinal digestion and biochemical characteristics

In this study, the digestion of yeast protein in the gastrointestinal tract of rats, and its effects on the blood biochemical parameters at different time points were investigated. Yeast protein was digested into peptides by pepsin in the stomach, broken down into dipeptides or amino acids by trypsin in the small intestine, and then absorbed by the rats or entered the colon. The peptide levels in gastric, small intestinal, and large intestinal digesta reached the highest level at 4 h, 2 h, and 8 h, respectively. Intact yeast protein in the gastric tract was found within 4 h, and no intact protein was present in intestinal digesta. Compared with gastric digesta, yeast protein intestinal digesta had much less distinguish and distinct stripes. Yeast protein ingestion increased the levels of immunoglobulin, high-density lipoprotein, and uric acid, and decreased the levels of total cholesterol, triglycerides, and low-density lipoprotein, while it did not significantly affect the levels of globulin, albumin, aspartate aminotransferase, and alanine aminotransferase in serum. This study demonstrated the digestion kinetics of yeast protein in the gastrointestinal tract of rats, and its beneficial effects on the blood biochemical parameters of rats and provided scientific evidence for yeast protein as an efficient and sustainable alternative protein source.

Physiochemical changes, metabolite discrepancies of brown seaweed-derived sulphated polysaccharides in the upper gastrointestinal tract and their effects on bioactive expression

Brown seaweed-derived polysaccharides, notably fucoidan and laminarin, are known for their extensive array of bioactivities and physicochemical properties. However, the effects of upper digestive tract modification on the bioactive performance of fucoidan and laminarin fractions (FLFs) sourced from Australian native species are largely unknown. Here, the digestibility and bioaccessibility of FLFs were evaluated by tracking the dynamic changes in reducing sugar content (CR), profiling the free monosaccharide composition using LC-MS, and comparing high-performance gel permeation chromatography profile variation via LC-SEC-RI. The effects of digestive progression on bioactive performance were assessed by comparing the antioxidant and antidiabetic potential of FLFs and FLF digesta. We observed that molecular weight (Mw) decreased during gastric digestion indicating that FLF aggregates were disrupted in the stomach. During intestinal digestion, Mw gradually decreased and CR increased indicating cleavage of glycosidic bonds releasing free sugars. Although the antioxidant and antidiabetic capacities were not eliminated by the digestion progression, the bioactive performance of FLFs under a digestive environment was reduced contrasting with the same concentration level of the undigested FLFs. These data provide comprehensive information on the digestibility and bioaccessibility of FLFs, and shed light on the effects of digestive progression on bioactive expression.

Study on the fabrication and controlled release behavior of N-Acetylneuraminic acid-loaded hydrogels stabilized by gelatin/whey protein isolate

Gelatin (GEL), pectin (PEC), carboxymethyl cellulose (CMC), and whey protein isolate (WPI) were employed to formulate hydrogels for stabilizing N-Acetylneuraminic Acid (NeuAc). GEL/WPI-NeuAc hydrogels, irrespective of the ratio, exhibited a flexible and smooth surface with a continuous three-dimensional network structure internally. Porosity of the three types of hydrogels increased from 3.69% to 86.92% (GEL/WPI), 41.67% (PEC/WPI), and 87.62% (CMC/WPI), rendering them suitable as carriers for NeuAc encapsulation. The dynamic swelling behavior of all hydrogels followed Schott's second-order kinetics model. The degradation performance of GEL, PEC, and CMC/WPI-NeuAc hydrogels was optimal at a 5: 5 ratio, with degradation rates of 80.39 ± 1.26%, 82.38 ± 1.96%, and 81.39 ± 1.57%, respectively. GEL, PEC, CMC/WPI-NeuAc hydrogels demonstrated decreased release rates of 44.56%, 31.04%, and 41.26%, respectively, compared to free NeuAc, post gastric digestion. The present investigation suggests the potential of GEL/WPI hydrogels as effective carriers for delivering NeuAc encapsulation.

Screening of glucosinolates degrading lactic acid bacteria and their utilization in rapeseed meal fermentation

Rapeseed meal is a promising food ingredient, but its utilization is limited by the presence of some potentially harmful ingredients, such as glucosinolates. Fermentation is a cost-effective method of detoxication but a food-grade starter culture with glucosinolates degradation capacity is required. In this study, 46 strains of lactic acid bacteria from traditional paocai brines were screened for their ability to glucosinolate degradation. The results showed that more than 50% of the strains significantly degraded glucosinolates. Two strains of Lactiplantibacillus (p7 and s7) with high capacity of glucosinolates degradation through producing enzymes were identified. Then, an optimized condition for rapeseed meal fermentation by p7 was established to degrade glucosinolates, which can achieve about 80% degradation. UPLC/Q-TOF-MS analysis showed that the degradation rate of individual glucosinolates was different and the degradation rate of gluconapin and progoitrin in rapeseed meal can reach more than 90%. Meanwhile, fermentation with p7 can improve safety of rapeseed meal by inhibiting the growth of Enterobacteriaceae and improve its nutritional properties by degrading phytic acid. The in vitro digestion experiments showed that the content of glucosinolates in rapeseed meal decreased significantly during gastric digestion. Meanwhile, fermentation with p7 can greatly improve the release of soluble protein and increase the contents of free essential amino acids, such as lysine (increased by 12 folds) and methionine (increased by 10 folds).

Nanosupplements based on protein-polysaccharide coacervates loaded with essential oils: Evaluation of antioxidant and antidiabetic properties

Essential oils (EOs) have demonstrated potential in food products to prevent complications related to diabetes. Nevertheless, the physicochemical characteristics of pure EOs, including high volatility and low chemical stability, face significant challenges when considering their utilization as functional ingredients. Thus, this study aimed to develop nanosupplements based on protein-polysaccharide coacervates loaded with EOs, thyme (THY) and oregano (ORE), and to evaluate their colloidal, antioxidant, and α-glucosidase and α-amylase inhibitory properties following an in vitro gastrointestinal digestion process. First, heat-induced egg white protein nanoparticles (EWPn) were used to encapsulate both EOs as nanocomplexes. Second, the process to obtain nanosupplements involved the electrostatic deposition of high methoxyl pectin (HMP) onto the surface of pre-formed nanocomplexes, resulting in the production of EWPn-THY-HMP and EWPn-ORE-HMP powders through a freeze-drying process. The effects of in vitro digestion on particle size, zeta potential, stability, and bioaccessibility of systems were analyzed. HMP exhibited a slight ability to protect EWPn from gastric digestion, while encapsulation within the EWPn-HMP system prevented the chemical degradation of EOs during gastrointestinal digestion. Subsequently, the antioxidant properties and the inhibitory effects of digested systems on α-glucosidase and α-amylase activities were examined. After in vitro digestion, EWPn-THY-HMP and EWPn-ORE-HMP systems showed higher ABTS+ radical scavenging than pure EOs (around 70% vs. 30%, respectively). Additionally, reducing power activities (expressed as mg of ascorbic acid equivalents-AAE mL−1) of EWPn-THY-HMP and EWPn-ORE-HMP systems were higher (1.6 ± 0.0 mg and 1.8 ± 0.1 mg of AAE mL−1, respectively) compared to pure THY and ORE (approximately 1.5 mg of AAE mL−1 for both) after in vitro digestion. The α-glucosidase inhibitory activity of EOs decreased upon encapsulation within EWPn-HMP system from an IC50 value of 0.3–1.0 μg mL−1, approximately. However, the effect of encapsulation on α-amylase inhibitory activity was EOs-dependent, and it was higher for the EWPn-ORE-HMP system, with an IC50 value of 8.6 ± 0.2 μg mL−1. The results highlight the potential of EOs encapsulation within EWPn-HMP coacervate nanosupplements as a promising strategy to facilitate their incorporation into food matrices while preserving their antioxidant and α-glucosidase and α-amylase inhibitory properties.

In vitro digestion of starch and protein aerogels generated from defatted rice bran via supercritical carbon dioxide drying

This study investigated the in vitro digestibility of starch and protein aerogels produced from defatted rice bran (DRB), an underutilized rice processing byproduct, using supercritical carbon dioxide (SC-CO2) drying. The extracted starch (i.e., purified starch), crude starch, and proteins were used for the aerogel formation at 15% (w/w) concentration and further characterized. All aerogels exhibited three-dimensional open porous structures with high surface areas of 36–47 m2/g, densities lower than 0.3 g/cm3, and porosities higher than 84%. The starch hydrolyses in starch and crude starch aerogels were 86 and 73%, respectively, while the protein hydrolysis in protein aerogels reached up to 82% after sequential oral, gastric, and intestinal digestion. Thus, the hydrolysis rates achieved in simulated digestions suggest that the developed aerogels from DRB have the potential to serve as vehicles for delivering bioactive compounds and add value to the underutilized DRB.

High-Moisture Extrusion of a Dietary Protein Blend Impairs In Vitro Digestion and Delays In Vivo Postprandial Plasma Amino Acid Availability in Humans

BackgroundIndustrial processing can alter the structural complexity of dietary proteins and, potentially, their digestion and absorption upon ingestion. High-moisture extrusion (HME), a common processing method used to produce meat alternative products, affects in vitro digestion, but human data are lacking. We hypothesized that HME of a mycoprotein/pea protein blend would impair in vitro digestion and in vivo postprandial plasma amino acid availability. MethodsIn Study A, 9 healthy volunteers completed 2 experimental trials in a randomized, double-blind, crossover design. Participants consumed a beverage containing 25 g protein from a “dry” blend (CON) of mycoprotein/pea protein (39%/61%) or an HME content-matched blend (EXT). Arterialized venous blood samples were collected in the postabsorptive state and regularly over a 5-h postprandial period to assess plasma amino acid concentrations. In Study B, in vitro digestibility of the 2 beverages were assessed using bicinchoninic acid assay and optical fluorescence microscopy at baseline and during and following gastric and intestinal digestion using the INFOGEST model of digestion. ResultsProtein ingestion increased plasma total, essential (EAA), and branched-chain amino acid (BCAA) concentrations (time effect, P < 0.0001) but more rapidly and to a greater magnitude in the CON compared with the EXT condition (condition × time interaction, P < 0.0001). This resulted in greater plasma availability of EAA and BCAA concentrations during the early postprandial period (0–150 min). These data were corroborated by the in vitro approach, which showed greater protein availability in the CON (2150 ± 129 mg/mL) compared with the EXT (590 ± 41 mg/mL) condition during the gastric phase. Fluorescence microscopy revealed clear structural differences between the 2 conditions. ConclusionsThese data demonstrate that HME delays in vivo plasma amino acid availability following ingestion of a mycoprotein/pea protein blend. This is likely due to impaired gastric phase digestion as a result of HME-induced aggregate formation in the pea protein.This trial was registered at clinicaltrials.gov as NCT05584358.

Mitochondria-targeted nanoparticles based on glycated oat protein for enhanced curcumin bioavailability and antioxidant activity

Curcumin is a hydrophobic dietary supplement and can mitigate oxidative damage. However, the low bioavailability of curcumin impedes its application in functional foods. Protein-coated nanoparticles are susceptible to environmental stress and have limited ability to reach mitochondria, where reactive oxygen species are generated. To overcome this limitation, we prepared mitochondria-targeted nanoparticles by modifying glycosylated oat protein isolate with triphenylphosphonium bromide for the efficient delivery of curcumin. In this study, the curcumin was incorporated into the spherical nanoparticles with high entrapment efficiency and loading capacity. The nanoparticles increased the stability of curcumin during heat treatment and light irradiation. The bioavailability of curcumin was improved in the nanoparticles due to their strong resistance against in vitro gastric digestion and good permeability across the Caco-2 cell monolayer. The nanoparticles realized lysosomal escape and exhibited specific accumulation in mitochondria upon internalization by Caco-2 cells. The mitochondria-targeted nanoparticles with no cytotoxicity further enhanced the antioxidant activity of curcumin by preserving mitochondrial membrane potential, increasing antioxidant enzyme activities, decreasing the concentrations of intracellular reactive oxygen species and malondialdehyde. This study highlights the potential application of glycosylated proteins in developing nanocarriers for precise delivery of hydrophobic nutrients.

In Vitro Characterization of Polysaccharides from Fresh Tea Leaves in Simulated Gastrointestinal Digestion and Gut Microbiome Fermentation.

Tea plants have a long cultivation history in the world, but there are few studies on polysaccharides from fresh tea leaves. In this study, tea polysaccharides (TPSs) were isolated from fresh tea leaves. Then, we investigated the characteristics of TPSs during in vitro simulated digestion and fermentation; moreover, the effects of TPSs on gut microbiota were explored. The results revealed that saliva did not significantly affect TPSs' molecular weight, monosaccharide composition, and reducing sugar content, indicating that TPSs cannot be digested in the oral cavity. However, TPSs were partially decomposed in the gastrointestinal tract after gastric and intestinal digestion, resulting in the release of a small amount of free glucose monosaccharides. Our in vitro fermentation experiments demonstrated that TPSs are degraded by gut microbiota, leading to short-chain fatty acid (SCFA) production and pH reduction. Moreover, TPSs increased the abundance of Bacteroides, Lactobacillus, and Bifidobacterium but reduced that of Escherichia, Shigella, and Enterococcus, demonstrating that TPSs can regulate the gut microbiome. In conclusion, TPSs are partially decomposed by gut microbiota, resulting in the production of SCFAs and the regulation of gut microbiota composition and function. Therefore, TPSs may be used to develop a prebiotic supplement to regulate the gut microbiome and improve host health.

Gastrointestinal digestion of olive leaf waste from olive mill production chain in a simulator of the gastrointestinal tract.

Currently, olive leaves are considered waste, although their high phenolic content makes them a source of antioxidants that could be used directly. The aim of this work was to study the behavior of phenolic compounds contained in olive leaf from the olive mill production chain during their gastrointestinal digestion. Phenolic compounds in the gastric digestion analyzed by high-performance liquid chromatography-diode array detection-mass spectrometry increased by 58% to 314.5% compared to the meal, while in the intestinal stage they ranged from 1.87 to 9.04 times higher. An increase of between 187% and 903% in bioaccessibility of phenolic compounds in the intestinal phase was observed, except for verbascoside. Furthermore, such compounds were fully bioavailable, except for apigenin-7-O-glucoside, which showed a bioavailability of 56%. The current study showed that the concentration of oleuropein, apigegin-7-O-glucoside, hydroxytyrosol hexoside and hydroxytyrosol contained in olive leaf continued to be extracted during the gastrointestinal digestion process. Furthermore, the results obtained with respect to their bioaccessibility and bioavailability suggest a good disposition to pass into the bloodstream where they could exert beneficial effects. Therefore, these results are promising for olive leaf becoming a consumable by-product that could be directly ingested through a simple infusion. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Blackcurrant (Fruits, Pomace, and Leaves) Phenolic Characterization before and after In Vitro Digestion, Free Radical Scavenger Capacity, and Antioxidant Effects on Iron-Mediated Lipid Peroxidation.

Blackcurrant (Ribes nigrum L.) is a berry bush widely cultivated in Europe for producing juices, jams, jellies, and syrups. In addition to berries, blackcurrant leaves and pomace, as byproducts, have also been shown to have health-promoting effects. Static digestion, simulating oral, gastric, and small intestinal digestion, was applied, and blackcurrant leaves, fruits, and pomace and the polyphenol bioaccessibility were evaluated in terms of recovery index. The results were related to sample type, and the recovery index presented higher values in the case of fruits, indicating this morphological part of blackcurrant as the most bioaccessible. The antioxidant potential of blackcurrant was evaluated using four different methods, with the leaves proving to be a significant and powerful antioxidant compared to fruits and pomace. The counteracting potential of inhibiting the oxidation process was evaluated using in vitro-induced lipid peroxidation and the inhibition potential of superoxide and hydroxyl anions. The antioxidant evaluation and the inhibition of biological and non-biological radicals indicate the leaf extract is the most powerful antioxidant studied. Also, the results proved that not only fruits but also the blackcurrant byproducts (pomace and leaves) are promising sources of bioaccessible antioxidants with potential benefits in animal nutrition.

Dynamic changes in the aggregation-depolymerization behavior of Ovomucin-Complex and its binding to urease during in vitro simulated gastric digestion

Ovomucin-Complex extracted from egg white is expected to have a barrier function similar to gastric mucin. In this study, the dynamic changes in structure, rheological properties and binding ability of Ovomucin-Complex during in vitro simulated gastric digestion were investigated. The results from HPLC and CLSM showed that extremely acidic pH (pH = 2.0) promoted Ovomucin-Complex to form aggregation. Acid-induced aggregation may hinder its binding to pepsin, thus rendering Ovomucin-Complex resistant to pepsin. Consequently, most of the polymer structure and weak gel properties of Ovomucin-Complex retained after simulated gastric digestion as verified by HPLC, CLSM and rheological measurement, although there was a small breakdown of the glycosidic bond as confirmed by the increased content of reducing sugar. The significantly reduced hydrophobic interactions of Ovomucin-Complex were observed under extremely acidic conditions and simulated gastric digestion compared with the native. Noticeably, the undigested Ovomucin-Complex after simulated gastric digestion showed a higher affinity (KD = 5.0 ± 3.2 nm) for urease - the key surface antigen of Helicobacter pylori. The interaction mechanism between Ovomucin-Complex and urease during gastric digestion deserves further studies. This finding provides a new insight to develop an artificial physical mucus barrier to reduce Helicobacter pylori infection.

Effects of Phytase and Tannase Enzyme Supplementation on in Vitro Nutrient Digestibility and Tannin Degradation of Sorghum-Based Broiler Diets

An in vitro study was conducted to assess the effects of phytase and tannase enzyme supplementation on nutrient digestibility and tannin degradability in sorghum-based broiler diets. A two-stage in vitro experiment involving simulation of gastric and ileal digestion in vivo was used. Data were analysed using Statistical Analysis System (SAS, 2011). The data were analysed for descriptive statistics and Chi-square tests were performed to check for possible associations among variables. Analysis of variance were performed to determine the effects of sorghum inclusion level as well as the effects of exogenous phytase and tannase supplementation on nutrients digestibility and tannin degradability using the GLM procedure. All tests were done at p&lt;0.05 level of significance. The results of this study indicated that phytase and tannase supplementation significantly influenced calcium, phosphorus, fat and crude protein digestibility (p&lt; 0.01). Sorghum inclusion level had no significant effect on calcium, phosphorus, fat and crude protein digestibility. Sorghum inclusion level significantly influenced tannin degradability (p&lt;0.01). Chi-square test showed that there was an association between sorghum inclusion level and tannin hence increasing sorghum level increased tannin degradability. Both enzyme supplementation and sorghum inclusion level had significant effect on crude fibre and tannin degradability.

Heat Treatment and Homogenization Influence the Gastric Digestion of Bovine Milk Protein in Growing Pigs as an Adult Human Model

BackgroundBovine milk processing influences the structure of the curd formed during gastric digestion, which may alter gastric protein hydrolysis and impact amino acid (AA) release into the small intestine. ObjectivesThis study aimed to determine the influence of heat treatment and homogenization on the gastric protein digestion and AA emptying of bovine milk. MethodsNine-wk-old pigs (n = 144) consumed either raw, pasteurized nonhomogenized (PNH), pasteurized homogenized (PH), or ultra-high-temperature homogenized (UHT) bovine milk for 10 d. On day 11, fasted pigs received the milk treatment (500 mL) before gastric contents were collected at 0, 20, 60, 120, 180, and 300 min postprandially. The apparent degree of gastric protein hydrolysis (based on the release of free amino groups), apparent gastric disappearance of individual proteins [based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) gel band intensity], and the gastric emptying of digested protein and AA were determined. ResultsDuring the first 60 min, the rate of apparent gastric protein hydrolysis was fastest in pigs fed UHT milk (0.29%/min compared with on average 0.07%/min in pigs fed raw, PNH, and PH milk). Differences in the apparent degree of gastric protein hydrolysis and emptying were reflected in the rate of digested protein entering the small intestine. The AA gastric emptying half-time was generally shorter in pigs fed PH and UHT milk than in pigs fed raw and PNH milk. For example, the gastric release of total essential AA was >2-fold faster (P < 0.01) in pigs fed PH or UHT milk than that in pigs fed raw or PNH milk (i.e., homogenized compared with nonhomogenized milk). ConclusionsHeat treatment and homogenization increased the apparent gastric degree of protein hydrolysis and the release of digested protein into the small intestine. However, the rate of AA entering the small intestine was mainly increased by homogenization.

Stability, Digestion, and Cellular Transport of Soy Isoflavones Nanoparticles Stabilized by Polymerized Goat Milk Whey Protein.

Soy isoflavones (SIF) are bioactive compounds with low bioavailability due to their poor water solubility. In this study, we utilized polymerized goat milk whey protein (PGWP) as a carrier to encapsulate SIF with encapsulation efficiency of 89%, particle size of 135.53 nm, and zeta potential of -35.16 mV. The PGWP-SIF nanoparticles were evaluated for their stability and in vitro digestion properties, and their ability to transport SIF was assessed using a Caco-2 cell monolayer model. The nanoparticles were resistant to aggregation when subjected to pH changes (pH 2.0 to 8.0), sodium chloride addition (0-200 mM), temperature fluctuations (4 °C, 25 °C, and 37 °C), and long-term storage (4 °C, 25 °C, and 37 °C for 30 days), which was mainly attributed to the repulsion generated by steric hindrance effects. During gastric digestion, only 5.93% of encapsulated SIF was released, highlighting the nanoparticles' resistance to enzymatic digestion in the stomach. However, a significant increase in SIF release to 56.61% was observed during intestinal digestion, indicating the efficient transport of SIF into the small intestine for absorption. Cytotoxicity assessments via the MTT assay showed no adverse effects on Caco-2 cell lines after encapsulation. The PGWP-stabilized SIF nanoparticles improved the apparent permeability coefficient (Papp) of Caco-2 cells for SIF by 11.8-fold. The results indicated that using PGWP to encapsulate SIF was an effective approach for delivering SIF, while enhancing its bioavailability and transcellular transport.

Dynamic Gastrointestinal Digestion of Bovine, Caprine and Ovine Milk Reconstituted from Commercial Whole Milk Powders.

The global dairy market has been increasingly diversified with more dairy product offerings of milk products from different animal species. Meanwhile, milk powders remain the main exported dairy product format due to their ease of transportation. In this work, we studied the structural changes, protein hydrolysis and nutrient delivery during dynamic gastric digestion and small intestinal digestion of cow, goat and sheep milk reconstituted from commercial whole milk powders. The results show that the reconstituted milks digest similarly to processed fresh milk. The digestion behaviors of the three reconstituted ruminant milks are broadly similar (gastric coagulation, kinetics of gastric emptying of protein and fat and the high digestibility in the small intestine) with some differences, which are likely contributed by the processing history of the milk powders. The delivery of individual amino acids to the small intestine differed between the early and late stages of gastric digestion, which were primarily affected by the abundance of amino acids in caseins and whey proteins but also by the difference between milk types associated with their gastric coagulation behaviors. This work showed that powdered milk is similar to fresh processed milk in digestion behavior, and the inherent differences between ruminant milks can be modified by processing treatments.