Intestinal Phase Of Digestion Research Articles

Encapsulation in β-lactoglobulin-chlorogenic acid complexes enhances digestibility and enzyme inhibitory activity of curcumin

Polyphenols could effectively prevent and alleviate many chronic diseases. However, the low solubility, poor stability, and bioaccessibility of certain bioactive ingredients have limited the development of functional foods. In this study, ultrasonication, free radical and their combination (ultrasonication/free radical) were used to prepare β-lactoglobulin (LG)-chlorogenic acid (CA) complexes. The complex was used as a shell to encapsulate curcumin (Cur), forming a ternary complex through anti-solvent method. Moreover, the digestive properties of the delivery system were evaluated by in vitro digestion simulation. Encapsulation by LG/LG-CA resulted in a controlled release of Cur which decreased Cur release in the oral and gastric phases while increased Cur release in intestinal digestion phase. In addition, LG-CA-Cur complex significantly inhibited the enzymatic activity of α-amylase and α-glucosidase. These findings indicated the potential of LG-CA complexes as an efficient carrier for Cur delivery and could be further used to develop functional dairy products with hypoglycemic activity.

Constructing stable emulsion gel from gelatin and sodium alginate as pork fat substitute: Emphasis on lipid digestion in vitro

This study aimed to develop a gelatin-sodium alginate (G-SA) emulsion gel that can efficiently hold corn oil, as a substitute for pork fat while controlling the digestive behaviors of lipids in vitro. UV, fluorescence, and circular dichroism spectra and surface hydrophobicity measurements of the G-SA mixtures indicated that gelatin and sodium alginate primarily form aggregates through hydrogen bonds and hydrophobic interactions, and the optimum gelatin-to-sodium alginate w/w ratio was identified as 1.9. The final emulsion gel contained 3.15% gelatin and 1.65% sodium alginate (w/w) with a corn oil content of 40% (w/w). G-SA emulsion gel had a higher proportion of polyunsaturated fatty acids (PUFAs, 53.95 g/100 g) than pork fat (15.17 g/100 g). In addition, the G-SA emulsion gel exhibited stable viscoelastic properties without storage and loss moduli changes at increasing shear rates. The G-SA emulsion gel had a higher melting temperature (42.63 °C) than pork fat (35.07 °C). In vitro digestion studies showed that corn oil had a higher free fatty acid release (40.32%) compared to the G-SA emulsion gel (12.66%) and pork fat (8.53%) (P<0.05), indicating that the digestibility of corn oil was reduced in the G-SA emulsion gel. Calcein release experiments revealed that G-SA emulsion gel released the least amount of calcein (P<0.05) during digestion at a slow rate. The G-SA emulsion gel, similar to pork fat, contained evenly distributed digestive particles encapsulating corn oil after in vitro gastric digestion, with the smallest particle size among the treatments. After the in vitro small intestinal digestion phase, the G-SA emulsion gel maintained small droplet sizes with bridging flocculation. The in vitro digesta of the G-SA emulsion gel contained a significantly higher proportion of PUFAs compared to pork fat (P<0.05). Consequently, the G-SA emulsion gel can be a potential substitute for pork fat, offering higher proportions of PUFAs, lower fat content, and controlled lipid digestion with reduced lipid digestibility.

In vitro Bioaccesibility of Phenolic Compounds from the Halophytes Suaeda Edulis and Suaeda Esteroa: Opportunity for the Development of Novel Foods

Halophytic plants grow in high salinity environments and present phytochemicals with antioxidant properties, such as phenolic compounds; due to the uncertain availability of healthy foods, there is a growing interest in their nutritional potential. However, their bioactive compounds with beneficial health effects are limited in their bioaccessibility. The objective of this study was to subject S. edulis and S. esteroa to an in vitro digestion process to evaluate the bioaccessibility and total antioxidant capacity of phenolic compounds during three phases of digestion. We determined phenolic compounds, flavonoids, and antioxidant capacity by colorimetric methods and phenolic composition by UHPLC-DAD. Total phenols, total flavonoids, and total antioxidant capacity by DPPH and TEAC in the three phases of digestion (oral, gastric, and intestinal) of S. esteroa were higher than in S. edulis, founding 4.84 % higher in total phenol content, and 0.05 % in total flavonoid content; also, and 28.94 and 23.93 % higher in total antioxidant capacity by DPPH and TEAC, respectively in the intestinal digestion phase. The bioaccessibility of S. edulis was higher than in S. esteroa; the intestinal was the phase reflecting more bioaccessible compounds. The bioaccessibility percentages of total phenols and flavonoids were 590.16 and 1012.93 %, and the percentage recovery of total antioxidant capacity by DPPH and TEAC were 181.37 and 139.74 %. We identified phenolic acids ferulic, p-Coumaric, and synaptic (hydroxycinnamic), gallic and protocatechuic (hydroxybenzoic), the flavonoids catechin (flavan-3-oles), myricetin and ruthin (flavonols), naringenin and naringin (flavonones). S. esteroa presented bioactive compounds in higher concentrations than S. edulis due to the stress imposed by its habitat; nevertheless, the determined bioactive compounds of S. edulis showed a higher bioaccessibility because it was managed under local improvement.

Impact of age on the digestion of cream cheese formulated with opposite caseins to whey proteins ratios: An in vitro study

Ageing leads to changes in the functionality of the digestive tract but the effect of age on digestion and absorption of nutrients remains unclear. The objective of this study was to investigate in vitro the digestion of two high-protein dairy products similar to cream cheese (24 % w/w proteins, 20 % w/w lipids) with opposite casein to whey protein ratios, 80:20 (WP-20), and 20:80 (WP-80). The new static digestion model adapted to the general older adult population (≥65 y.) proposed by INFOGEST was used, as well as the standard version of the protocol. Kinetics of proteolysis and lipolysis were compared between both models for each product, in the gastric and intestinal phases of digestion. In both cream cheeses, the degree of protein hydrolysis (DH-P) was significantly lower for older adults than for young adults at the end of the gastric phase (−19 % for WP-20, and −44 % for WP-80), and at the end of the intestinal phase (−16 % for WP-20, and −20 % for WP-80). The degree of lipid hydrolysis (DH-L) was also significantly lower for older adults than for young adults at the end of the digestion for WP-20 (−30 %), but interestingly it was not the case for WP-80 (similar DH-L were measured). Free fatty acids were also released faster from WP-80 than from WP-20 in both digestion conditions: after 5 min of intestinal digestion DH-L was already ≈32 % for WP-80 against 14 % for WP-20. This was attributed to the opposite casein to whey protein ratios, leading to the formation of different gel structures resulting in different patterns of deconstruction in the gastrointestinal tract. This study highlights the fact that it is essential to carefully consider the composition, structure, and digestibility of foods to develop products adapted to the specific needs of the older adult population.

Release profile of amino acids encapsulated in solid lipid particles during in vitro oro-gastrointestinal digestion

Some amino acids are known to mediate immune responses through gut microbiota metabolism in both humans and monogastric animals. However, through the diet, most free amino acids are absorbed in the small intestine and only a small quantity reaches the microbiota-rich colon. To enhance microbial metabolism of amino acids and their potential health benefits, encapsulation strategies are developed for their protection and delivery to the colon. So far, the main encapsulation systems for amino acids are based on solid lipid particles, but their fate within the digestive tract has never been fully clarified.In this study, we investigated the release of various amino acids (branched-chain amino acid mixture, or lysine, or tryptophan) loaded in solid lipid particles during in vitro oro-gastrointestinal digestion mimicking the piglet. The loaded solid lipid particles were fully characterized for their composition, thermal behavior, molecular structure, crystalline state, surface morphology, and particle size distribution. Moreover, we investigated the effect of particle size by sieving solid lipid particles into two non-overlapping size fractions.We found that amino acid release was high during the gastric phase of digestion, mainly controlled by physical parameters, namely particle size and crystalline state including surface morphology. Large particle size and/or smooth ordered particle indeed led to slower and lower release. Although lipid hydrolysis was significant during the intestinal phase of digestion, the impact of the crystalline state and surface morphology was also observed in the absence of enzymes, pointing to a dominant water/solute diffusion mechanism through these porous solid lipid particles.

Peptidomic profile and α-glucosidase inhibitory activity of cooked and gastrointestinal digested legumes

Legumes are a good source of bioactive compounds, including peptides with antidiabetic potential. The α-glucosidase inhibitory activity of simulated gastrointestinal digested (GID) soybean, chickpea, green pea, and navy bean was determined after using three different household cooking methods (conventional, pressure, and microwave cooking). Samples were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC), and the fractions responsible for the α-glucosidase inhibitory activity were isolated. Lastly, peptides were identified by mass spectrometry in tandem (MS/MS) and in silico analyses were done to hypothesise potentially bioactive sequences. The results indicated that all legume extracts exert α-glucosidase inhibitory activity after thermal treatment and GID. Peptide profiles obtained by RP-HPLC showed the highest generation of peptides after the intestinal digestion phase, with small changes between thermal treatments. Best α-glucosidase inhibitory activity was observed in fraction 2 of all gastrointestinal digested samples, with values between 40 % and 62 % inhibition. In soybean, green pea, and navy bean, conventional-cooked samples showed the highest activity, while the pressure-cooked treatment resulted in significantly higher activity in chickpea samples. Finally, 48 peptides were identified by MS/MS and 13 were found as potentially bioactive using in silico tools, expanding previous knowledge on antidiabetic peptides derived from legumes.

In Vitro Gastrointestinal Release of Chlorogenic Acid and Curcumin Co-Encapsulated in Double Emulsions with the Outer Interface Stabilized by Cellulose Nanocrystals

A Pickering double emulsion (DE) with an outer (O:W2) interface stabilized by cellulose nanocrystals (DE-CNC) was designed as a co-delivery systems for chlorogenic acid (CA) and curcumin, then compared with a control DE emulsion with an O:W2 interface stabilized with sodium caseinate (DE-NaCas). DE-CNC was more resistant to creaming during storage (6.79%, day 42) and showed higher encapsulation efficiency (EE) of CA (&gt;90%). Conversely, both DEs exhibited similarly high EE for curcumin (&gt;97%). The ζ-potential values were highly negative in both DEs, but tended to be lower in DE-CNC due to the highly negative charge of the CNCs. DE-CNC allowed for a steady release of CA during the oral, gastric, and intestinal phases of digestion, while a total release of CA was already observed in the gastric phase in case of DE-NaCas. The bioaccessibility of CA was similar in both DEs (~57–58%). Curcumin was mainly released in the intestinal phase with both DEs, reaching slightly lower bioaccessibility values with DE-CNC. The use of CNCs as a stabilizer for the outer interface of DEs is a promising strategy to increase the stability and EE of these systems, providing oral co-delivery vehicles capable of releasing significantly bioactive compounds during the intestinal phase of digestion.

Investigation of the antioxidative potential of Meretrix meretrix L. derived peptides from simulated gastrointestinal digestion: In vitro and in silico insights

This investigation sought to identify antioxidative peptides derived from Meretrix meretrix L. (MML) throughout simulated gastrointestinal digestion (SGD) via in vitro and in silico strategies. The study demonstrated that hydrolysates from MML captured at various SGD phases showcased robust antioxidative activity. These hydrolysates also displayed a protective role against hydrogen peroxide-induced stress in Raw 264.7 cells. Notably, hydrolysates sourced from the intestinal phase of digestion (MMLHs-I) markedly inhibited the reduction of cell viability, limited the generation of reactive oxygen species under oxidative stress conditions, and promoted the activity of key antioxidant enzymes including superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, thus amplifying the cells' antioxidative defense system. Through nLC-MS/MS analysis, 105 peptides tracing back to 18 parent proteins were pinpointed in MMLHs-I, with 18 of these peptides previously reported in the BIOPEP-UWM database. Subsequent in silico analysis, alongside empirical antioxidant activity assays, pinpointed the peptide WLV as an exceptional antioxidative agent, demonstrating an IC50 of 0.125 mg/mL in the ABTS assay and an impressive 15.18 μmol Trolox/mg in the ORAC assay. The outcomes highlight MML's promise as a novel source of antioxidative peptides, positioning peptide WLV as a potentially valuable addition to functional foods designed to combat oxidative stress.

Nutritional, Textural, and Sensory Attributes of Protein Bars Formulated with Mycoproteins.

Research accumulated over the past decades has shown that mycoprotein could serve as a healthy and safe alternative protein source, offering a viable substitute for animal- and plant-derived proteins. This study evaluated the impact of substituting whey protein with fungal-derived mycoprotein at different levels (10%, 20%, and 30%) on the quality of high-protein nutrition bars (HPNBs). It focused on nutritional content, textural changes over storage, and sensory properties. Initially, all bars displayed similar hardness, but storage time significantly affected textural properties. In the early storage period (0-5 days), hardness increased at a modest rate of 0.206 N/day to 0.403 N/day. This rate dramatically escalated from 1.13 N/day to 1.36 N/day after 5 days, indicating a substantial textural deterioration over time. Bars with lower mycoprotein levels (10%) exhibited slower hardening rates compared with those with higher substitution levels (20% and 30%), pointing to a correlation between mycoprotein content and increased bar hardness during storage. Protein digestibility was assessed through in vitro gastric and intestinal phases. Bars with no or low-to-medium levels of mycoprotein substitution (PB00, PB10, and PB20) showed significantly higher digestibility (40.3~43.8%) compared with those with the highest mycoprotein content (PB30, 32.9%). However, digestibility rates for all mycoprotein-enriched bars were lower than those observed for whey-protein-only bars (PB00, 84.5%), especially by the end of the intestinal digestion phase. The introduction of mycoprotein enriched the bars' dietary fiber content and improved their odor, attributing a fresh mushroom-like smell. These findings suggest that modest levels of mycoprotein can enhance nutritional value and maintain sensory quality, although higher substitution levels adversely affect texture and protein digestibility. This study underscores the potential of mycoprotein as a functional ingredient in HPNBs, balancing nutritional enhancement with sensory acceptability, while also highlighting the challenges of textural deterioration and reduced protein digestibility at higher substitution levels.

Secretin: a hormone for HCO3- homeostasis.

Secretin is a key hormone of the intestinal phase of digestion which activates pancreatic, bile duct and Brunner gland HCO3- secretion. Recently, the secretin receptor (SCTR) was also found in the basolateral membrane of the beta-intercalated cell (B-IC) of the collecting duct. Experimental addition of secretin triggers a pronounced activation of urinary HCO3- excretion, which is fully dependent on key functional proteins of the B-IC, namely apical pendrin and CFTR and the basolateral SCTR. Recent studies demonstrated that the SCTR knock-out mouse is unable to respond to an acute base load. Here, SCTR KO mice could not rapidly increase urine base excretion, developed prolonged metabolic alkalosis and exhibited marked compensatory hypoventilation. Here, we review the physiological effects of secretin with distinct focus on how secretin activates renal HCO3- excretion. We describe its new function as a hormone for HCO3- homeostasis.

Effect of gum arabic and thermal modification of whey protein isolate on the characteristics of Cornus officinalis flavonoid microcapsules.

Whey protein isolates (WPIs) were treated at 50, 60, 70, and 80°C to obtain thermally modified WPI. Gum arabic (GA) and thermal modification of WPI were used as novel wall materials to improve the quality of Cornus officinalis flavonoid (COF) microcapsules using microwave freeze-drying technique in this study. Results showed that all the thermal modification treatment decreased emulsifying activity index of WPI, whereas the solubility and emulsifying stability index (ESI) of WPI gradually increased with the increase of heating temperature. Compared to the untreated protein, the thermal modification treatment at 70°C increased the solubility and ESI of WPI by 14.91%±0.71% and 26.70%±0.94%, respectively. The microcapsules prepared with the modified protein at 60°C had the highest encapsulation efficiency (95.13%±2.36%), the lowest moisture content (1.42%±0.34%), and the highest solubility (84.41%±0.91). Scanning electron microscopy images showed that COF microcapsules were uniformly spherical, and the sizes of the microcapsules were in the following order: 12.42±0.37µm (80°C)>11.7±0.23µm (untreated group)>9.44±0.33µm (60°C)>9.24±0.14µm (50°C)>7.69±0.29µm (70°C). In the simulated in vitro digestion experiments, the release rate of COF microcapsules in the gastric digestion phase was less than that in the intestinal digestion phase, and it reached 66.46% at intestinal digestion phase. These results suggested that heated WPI and GA could be an effective nanocarrier to enhance the stability of COF.

In vitro gastrointestinal digestion of marine oil emulsions and liposomal solutions: fate of LC-PUFAs upon lipolysis.

The bioaccessibility and bioavailability of dietary fatty acids depend on the lipid to which they are esterified, the organisation of theses lipids in water and their recognition by lipolytic enzymes. In this work, we studied the release of marine long-chain polyunsaturated fatty acids (LC-PUFA), depending on their presentation either in the form of phospholipids (PL) or triacylglycerol (TAG). Two formulations based on marine PL or TAG extracted from salmon heads (Salmo salar) were prepared. Lipolysis was first tested in vitro by using individual gastrointestinal lipases and phospholipases to identify the enzymes involved in the digestion. Second, the lipolysis of the prepared formulations by a combination of enzymes was tested under in vitro conditions mimicking the physiological conditions found in the GI tract, both in the stomach and in the upper small intestine, in order to evaluate digestibility of TAG and LC-PUFA-containing liposomes. The in vitro results showed that TAG emulsion was hydrolyzed by porcine pancreatic extracts (PPE) and pure pancreatic lipase (PPL) with its cofactor, colipase, and to a lesser extent by pancreatic-lipase-related protein 2 (PLRP2) and a gastric extract (RGE) containing gastric lipase while no hydrolysis was observed with purified pancreatic phospholipase A2 (PLA2) and carboxyl ester hydrolase (CEH). The PL substrate was found to be hydrolysed by PLA2, PPE and PLRP2. Their phospholipase activities on liposomes formulation was dependent on the presence of bile salts. Using a two-step in vitro digestion model, we measured the kinetics of fatty acid release from TAG and PL during the gastric and intestinal phases of digestion. The highest overall lipolysis level was obtained with liposomes (around 75%) during the intestinal phase while they were preserved during the gastric phase. The overall lipolysis level of TAG emulsion was lower (around 33%), while it started already in the gastric phase. In conclusion, liposomes appear as a better delivery system for intestinal absorption of LC-PUFA than TAG. In addition, their resistance to lipolysis under gastric condition can protect LC-PUFA and provide a gastric stable delivery system for other molecules.

High-Pressure Homogenization for Enhanced Bioactive Recovery from Tomato Processing By-Products and Improved Lycopene Bioaccessibility during In Vitro Digestion.

The principles of industrial ecology have emerged as pivotal drivers of eco-innovation, aiming to realize a "zero-waste" society where waste materials are repurposed as valuable resources. In this context, High-Pressure Homogenization (HPH) presents a promising, easily scalable micronization technology, capable of enhancing the extractability and bioaccessibility of bioactive compounds found in tomato processing by-products, which are notably abundant waste streams in the Mediterranean region. This study focuses on optimizing HPH treatment parameters to intensify the recovery of bioactive compounds from tomato pomace. Additionally, it investigates the multifaceted impacts of HPH on various aspects, including color, particle size distribution, microscopic characteristics, surface properties, bioactivity, and lycopene bioaccessibility through in vitro digestion simulations. The results demonstrate that the application of HPH under optimized conditions (80 MPa, 25 °C, 10 passes) induces a remarkable 8-fold reduction in mean particle size, reduced surface tension, improved physical stability, uniform color, increased total phenolic content (+31%), antioxidant activity (+30%), dietary fiber content (+9%), and lycopene bioaccessibility during the intestinal digestion phase compared to untreated samples. These encouraging outcomes support the proposition of integrating HPH technology into an environmentally friendly industrial process for the full valorization of tomato processing residues. By utilizing water as the sole solvent, this approach aims to yield a functional ingredient characterized by greater nutritional and health-promoting values.

Investigating the effectiveness of coacervates produced from conjugated and unconjugated Spirulina protein in delivering unstable oil to the intestinal phase of digestion

This study investigated the potential of complex coacervates produced using Spirulina protein concentrate (SPC) conjugated with maltodextrin (MD) and carrageenan (CG) for encapsulating and delivering sensitive oils. A wet-heating Maillard reaction was employed to conjugate SPC with MD, followed by coacervation with CG to form the conjugate-based coacervates. Additionally, a mixture of unconjugated SPC and MD was coacervated with CG to produce mixture-based coacervates. Both types of coacervates were utilised as wall materials for encapsulating canola oil. The in-vitro digestion of the resulting microcapsules was assessed in oral, gastric, and intestinal phases, focusing on physicochemical parameters such as droplet size, zeta-potential, microstructure, proteolysis, oil release and lipolysis. The findings revealed that microcapsules prepared using both (SPC-MD mixture)-CG and (SPC-MD conjugate)-CG coacervates were remarkably stable against gastric digestion, as evidenced by the minimal production of free amino acids (15 mM). Most of the encapsulated oil (62–67%) was released during the intestinal phase due to the breakdown of the coacervates. Notably, the microcapsules produced with (SPC-MD conjugate)-CG coacervates demonstrated a lower degree of lipolysis (41.77% free fatty acid content) compared to those prepared with (SPC-MD mixture)-CG coacervates (53.35% free fatty acid content). These results highlight the potential of complex coacervates produced using conjugated SPC as promising materials for the encapsulation and delivery of sensitive oils.

Effects of rice bran rancidity on the release of phenolics and antioxidative properties of rice bran dietary fiber in vitro gastrointestinal digestion products

Rice bran (RB) as the raw material for rice bran dietary fiber (RBDF) extraction, is rapidly rancidified prior to stabilization. To enhance the RBDF utilization in food industry, effects of RB rancidity (RB was stored for 0, 1, 5, 7, and 10 d) on the bioaccessibility and bioavailability of RBDF-bound phenolics were investigated. With the increase in RB storage time, the RB rancidity degree significantly increased (the acid value of rice bran oil from 5.08 mg KOH/g to 60.59 mg KOH/g), and the endogenous phenolics content in RBDF also increased. Simultaneously, RB rancidity reduced the antioxidant activity of RBDF digestion products during the gastric digestion phase, while RB rancidity increased the antioxidant activity of RBDF digestion products during the intestinal digestion phase. In addition, in vitro gastrointestinal digestion stimulated the release of RBDF-bound phenolics. The released monomeric phenolics (especially ferulic acid and p-coumaric acid) were the major contributors to the increased antioxidant properties of RBDF digestion products. RBDF digestion products could inhibit H2O2-induced oxidative stress and apoptosis of HUVECs. In conclusion, the study found that RB rancidity could improve the antioxidant capacity of RBDF in the small intestine by promoting RB endogenous phenolics bound to RBDF release.

Effects of Lactiplantibacillus plantarum with different phenotypic features on the nutrition, flavor, gel properties, and digestion of fermented soymilk

This study evaluated the effects of four previously reported strains of Lactiplantibacillus plantarum (T1, CL80, CSK, and S-1A) with different phenotypic characteristics on the fermentation quality, flavor characteristics, and digestive properties of soy milk. The results showed that all four strains exhibited good gastrointestinal survival and Caco-2 cell adhesion probiotic characteristics. The total free amino acid content of fermented soy milk significantly increased from 27.57 mg/100 g to 41.28 mg/100 g, enriching the soy milk with acidity and increasing the volatile flavor compounds such as acetic acid, decanoic acid, and octanoic acid. The fermentation process effectively reduced the levels of volatile compounds associated with beany off-flavors, including 1-octen-3-ol, 1-nonanol, hexanal, heptanal, 2-octenal, furfural, and trans-2,4-decadienal. The gel texture and rheological analysis indicated that soy milk fermented with the viscous phenotypic strains T1 and CL80 exhibited higher water-holding capacity (95.45%, 93.64%) and apparent viscosity (916.39, 713.78 Pa s). Furthermore, in vitro dynamic digestion demonstrated that soy milk fermented with the viscous phenotypic strains was more easily digested during the gastric phase compared to the non-viscous strains. In the intestinal phase of digestion, soy milk fermented with the ropy phenotypic strains had significantly higher levels of small peptides compared to the non-ropy strains, which facilitated the transfer and absorption of nutrients. This study provides valuable insights into improving the nutritional flavor and digestive properties of soy milk through fermentation using Lactiplantibacillus plantarum strains with different phenotypic characteristics.

Stability and Digestive Properties of a Dual-Protein Emulsion System Based on Soy Protein Isolate and Whey Protein Isolate.

The stability and digestive properties of a dual-protein emulsion consisting of soy protein isolate (SPI) and whey protein isolate (WPI) have been systematically studied. The results showed that the particle size and viscosity of the dual-protein emulsion system decreased continuously with the increase in WPI, and this might be related to the large amount of electric charge on the surface of the emulsion droplets. Dual-protein emulsions with ratios of 3:7 and 5:5 showed the highest emulsion activity, while emulsion stability increased with the increase in WPI. The thicker adsorption layer formed at the interface might have contributed to this phenomenon. After in-vitro-simulated digestion, the emulsion droplet particle size increased substantially due to the weakened electrostatic repulsion on the droplet surface, especially for the intestinal digestion phase. Meanwhile, WPI accelerated the release of free fatty acids in the digestion process, which played a positive role in the nutritional value of the dual-protein emulsion. In accelerated oxidation experiments, WPI also improved the antioxidant properties of the dual-protein emulsion system. This study will provide a new insight and necessary theoretical basis for the preparation of dual-protein emulsions.

Adult and elderly in vitro digestibility patterns of proteins and carbohydrates as affected by different commercial bread types

Carbohydrate and protein digestibility were assessed in different commercial bread types, i.e., soft, durum, and whole wheat, by applying in vitro digestion protocols mimicking adult or elderly physiological conditions. Protein digestibility was measured after the gastric and intestinal phases by the o-phthalaldehyde spectrophotometric assay (OPA). Carbohydrate digestibility was assessed by determining the incremental area under glucose curve during the intestinal phase of digestion to estimate the glycaemic index (GIe). Finally, the correlation between protein and carbohydrate digestibility was computed.Bread proteins presented a high gastric resistance, with a digestibility < 10% in all cases while after the intestinal phase, protein digestibility increased, ranging from 40 to 70%. Protein digestibility was affected both by formulation, with whole wheat bread presenting the lowest values, and by physiological conditions, with restrained digestibility under elderly conditions compared to adult ones.The GIe decreased in the order durum > soft > whole, under both adult (119, 101, and 82, respectively) and elderly (107, 93, and 65, respectively) conditions. The extent of differences under different physiological settings varied depending on the bread type, without significant changes for soft wheat bread (ΔGIe = 8), whereas elderly conditions significantly reduced GIe both for durum (ΔGIe = 12) and whole (ΔGIe = 17) wheat bread.An almost strong positive correlation between protein digestibility and GIe was observed (p = 0.69), indicating that concomitantly addressing sarcopenia and type 2 diabetes can only be pursued by a compromise solution or more desirably requires identifying technological strategies to maximize protein digestibility while restraining the glycaemic response.

Levels of nitrate, nitrite and nitrosamines in model sausages during heat treatment and in vitro digestion – The impact of adding nitrite and spinach (Spinacia oleracea L.)

Nitrite derivatives react with endogenous precursors forming N-nitrosamines associated with development of colorectal cancer. The present study aims to investigate the formation of N-nitrosamines in sausage during processing and in vitro gastrointestinal digestion after adding sodium nitrite and/or spinach emulsion. The INFOGEST digestion protocol was used to simulate the oral, gastric, and small intestinal phases of digestion, and sodium nitrite was added in the oral phase to mimic the input of nitrite from saliva as it has shown to affect the endogenous formation of N-nitrosamines. The results show that the addition of spinach emulsion, in spite of it being a source of nitrate, did not affect the nitrite content in either batter, sausage, or roasted sausage. The levels of N-nitrosamines increased with the added amount of sodium nitrite, and further formation of some volatile N-nitrosamines was observed during roasting and in vitro digestion. In general, N-nitrosamine levels in the intestinal phase followed the same trend as in the undigested products. The results further indicate that nitrite present in saliva may cause a significant increase in N-nitrosamine levels in the gastrointestinal tract and that bioactive components in spinach may protect against the formation of volatile N-nitrosamines both during roasting and digestion.

In vitro digestion of two protein-rich dairy products in the ageing gastrointestinal tract.

It is still unclear if changes in protein digestibility and absorption kinetics in old age may affect the anabolic effect of high-protein foods. The objective of this study was to investigate the digestion of two high-protein (10% w/w) dairy products in vitro: a fermented dairy product formulated with a ratio of whey proteins to caseins of 80 to 20% (WBD) and a Skyr containing mainly caseins. The new static in vitro digestion model adapted to the general older adult population (≥65 years) proposed by the INFOGEST international consortium was implemented to investigate the digestion of these products and compared with the standard version of the protocol. Kinetics of proteolysis was compared between both models for each product, in the gastric and intestinal phases of digestion. Protein hydrolysis was studied by the OPA method, SDS-PAGE, and LC-MS/MS, and amino acids were quantified by HPLC. Protein hydrolysis by pepsin was slower with the older adult model than with the young adult model, and consequently, in spite of a longer gastric phase duration, the degree of proteolysis (DH) at the end of the gastric phase was lower. Two different scenarios were observed depending on the type of dairy product studied: -10 and -40% DH for Skyr and WBD, respectively. In the intestinal phase, lower concentrations of free leucine were observed in older adult conditions (approx. -10%), but no significant differences in proteolysis were observed overall between the models. Therefore, the digestion conditions used influenced significantly the rate and extent of proteolysis in the gastric phase but not in the intestinal phase.