Gel Digestion Research Articles

Unveiling the slow digestion and peptide profiles of polymerised whey gel via heat and TGase crosslinking: An in vitro/vivo perspective

Polymerised whey is widely used in dairy products and can affect digestibility when its high-molecular-weight aggregates and gel structure are modified. This study investigated the digestibility, peptide profiles and satiety of modified whey protein isolate (MWPI) pre-heated with transglutaminase. Results showed that 43.06 % of MWPI was digested during the 4-h in vitro digestion, indicating a slow digestion rate. Compared with whey protein isolate (WPI), MWPI yielded 103 peptides with higher abundance following in vitro digestion, including 17 angiotensin-converting enzyme inhibitors and 1 dipeptidyl peptidase-4 inhibitor. Visual analytics indicated differential peptides located at distinct α-helix and β-sheet of β-lactoglobulin, α-lactalbumin and bovine serum albumin. MWPI gavage extended stomach retention time, decreased intestinal propulsion rate from 75.60 % (WPI group) to 33.72 % in 30 min and enhanced satiety within 120 min compared with WPI. Overall, whey polymerisation modulates protein–enzyme interactions, releasing different peptides and enhancing satiety.

Extraction technology determines the properties of bamboo shoots dietary fiber concentrate and its application in chicken mince gels: Systematic analysis

This study investigated how physical, chemical, and enzymatic extraction technologies affected the physicochemical properties of bamboo shoot insoluble dietary fiber (IDF). Additionally, the effects of IDF extracted by these techniques on the gel properties, water retention, microstructure, and digestibility of chicken mince gels were evaluated. Results showed that IDFs extracted by physical (P-IDF), chemical (C-IDF), and enzymatic (E-IDF) exhibited a typical cellulose polysaccharide structure and strong water and oil retention capabilities, with the highest values reaching 14.18 g/g and 6.74 g/g, respectively. Compared to P-IDF, C-IDF and E-IDF displayed a rougher porous structure and stronger adsorption capacities for glucose (409.91 mg/g and 604.95 mg/g), cholesterol (54.46 mg/g and 64.06 mg/g), sodium cholate, and nitrite. The addition of IDF improved the water retention, water stability, texture, and rheological properties of chicken mince gels, and had no negative effect on the digestion of chicken mince proteins. On the one hand, the hydrophilic groups exposed in IDF absorb water and fill the gel networks, reducing the formation of water channels in the gel and improving water stability. Furthermore, the hydrophilic groups on the glucose unit that makes up the IDF interacts with the proteins through the hydrogen bond and the transformation of protein β-structure to α-structure, promoting the formation of gel network structure and improving gel texture and rheological properties. E-IDF and C-IDF showed better overall gel performances, but E-IDF had better dry matter digestibility, protein digestibility, and gastrointestinal digestive effects. Therefore, IDF prepared by enzymatic hydrolysis is more suitable for chicken mince processing.

Understanding of formation, gastrointestinal breakdown, and application of whey protein emulsion gels: Insights from intermolecular interactions.

Whey protein emulsion gel is an ideal model food for revealing how the multilength scale food structures affect food digestion, as their structure and mechanical properties can be precisely manipulated by controlling the type and intensity of intermolecular interactions between protein molecules. However, there are still significant understanding gaps among intermolecular interactions, protein aggregation and gelation, emulsion gel formation, gel breakdown in the gastrointestinal tract (GIT), and the practical use of whey protein emulsion gels, which limits their GIT-targeted applications. In this regard, the relationship between the structure and digestion behavior of heat-set whey protein emulsion gels is reviewed and discussed mainly from the following aspects: (1) structural characteristics of whey protein molecules; (2) how different types of intermolecular interactions influence heat-induced aggregation and gelation of whey protein in the aqueous solutions and the oil-in-water emulsions, and the mechanical properties of the final gels; (3) functions of the mouth, the stomach, and the small intestine in processing of solid foods, and how different types of intermolecular interactions influence the breakdown properties of heat-set whey protein emulsion gels in GIT (i.e., their respective role in controlling gel digestion). Finally, the implications of knowledge derived from the formation and gastrointestinal breakdown of heat-set whey protein emulsion gels for developing controlled delivery vehicles, human satiety enhancers, and sensory modifiers are highlighted.

Pea protein soften surimi gels and improve in vitro digestibility: Potential high protein foods for elderly

As the fastest growing fraction of the global population, the creation of high protein foods for the elderly has become increasingly urgent and important. While surimi gels are a good source of concentrated myofibrillar proteins, their elastic texture makes swallowing of these gels difficult, which current studies have focused on maintaining or enhancing. As such this study aimed to better understand how to reduce surimi gelation which would allow us to better control gel texture by partially replacing surimi with pea proteins. With an increasing proportion of pea proteins, the hardness, cohesiveness and adhesiveness of the gels was progressively reduced. This was due to the increase in pea protein aggregate formation, as characterised by the increase in β-structures and hydrophobic interactions which reduced the viscoelasticity and time stability of the gels. When comprising of less than 60% pea proteins, pea aggregates were dispersed within the continuous crosslinked surimi gel network, but above that the aggregates dominated the gels, disrupting the network structure, forming coarse gels with larger pores. Hence, mixed protein gels with 60% and above pea proteins had modified textures suitable for consumption by those with swallowing difficulties. Gel structure and texture also positively influenced the in vitro digestibility of the gels, as the higher pea protein ratio and softer texture allowed for increased proteolysis, solubilisation, and amino acid release. Thus, this study provides a basis for modulating the texture of mixed surimi and pea protein gels by understanding protein interactions and their effects on gel structure and digestibility.

Impact of microstructure of whey protein gels on in vitro gastric protein digestion is sustained after oral structural breakdown by mastication

Gastric protein digestion can be influenced by food micro- and macrostructure. Understanding the interplay between microstructure and macrostructural breakdown during oral processing is crucial to enhance the nutritional value of protein-rich foods. This study compared the in vitro gastric protein digestion of whey protein gels differing in microstructure before and after mastication. Whey protein isolate was mixed with κ-carrageenan to obtain heat-induced gels differing in microstructure (homogeneous, coarse stranded, protein continuous, bi-continuous). Gel boli were collected from 14 participants. The number, size and total surface area of bolus fragments were determined. In vitro gastric protein digestion was quantified following the INFOGEST 2.0 protocol with minor modifications. Before mastication, coarse stranded gels showed the highest digestion rate (1.07 mmol L−1∙g dry matter−1/h), while homogeneous, protein continuous and bi-continuous gels showed lower and similar digestion rates (0.82–0.87 mmol L−1∙g dry matter−1/h). After mastication, the total surface area of coarse stranded gels increased 7.9-fold leading to a 1.9-fold increase in digestion rate. In contrast, a 3.4-fold increase in total surface area of bi-continuous gels caused a 2.8-fold increase in digestion rate. The total surface area of homogeneous and protein continuous gels increased 3.1- to 3.6-fold upon mastication resulting in a 1.7- to 1.9-fold increase in digestion rate. The increase in protein hydrolysis did not correlate with the degree of structural breakdown after mastication across gels differing in microstructure. We conclude that the impact of microstructure of whey protein gels on in vitro gastric protein digestion is sustained after oral structural breakdown by mastication.

Role of sodium pyrophosphate and catechin in the enzymatic hydrolysis of oxidatively damaged myofibrillar protein gels in vitro: Mechanistic insights

This study investigated the effects of sodium pyrophosphate (SPP) and catechin (C) on the in vitro enzymatic digestion of oxidatively damaged myofibrillar protein (MP) gel. The results indicated that SPP increased the β-sheet content and the gastric digestibility of the MP gel, while C hindered the transition from α-helix to β-sheet structure, leading to decreased digestibility. Notably, neither compound significantly affected intestinal digestibility. Furthermore, SPP and C significantly enhanced the antioxidant activity of MP gel digestion products. Notably, their synergistic hydrolysis products, simulating both gastric and gastrointestinal stages, chelated 91.4 % and 89.1 % of Fe2+ and scavenged 59.4 % and 77.6 % of hydroxyl radicals, respectively. Moreover, the final digestion products of the MP gel treated with SPP and C exhibited the highest content of negatively charged amino acids and absolute Zeta potential values. Overall, this study demonstrated that incorporating SPP and C could positively impact the digestion of oxidatively damaged MP gels.

Impact of konjac glucomannan with varied deacetylation degrees on plant-based meat analogue: Study on the gel properties, digestibility, and microstructure

Polysaccharides are widely used to improve the quality of plant-based meat analogue (PMA). In this study, four kinds of konjac glucomannan (KG) with different deacetylation degrees (DD) were prepared, namely KG1 (native KG, DD = 0.00 %), KG2 (DD = 41.40 %), KG3 (DD = 80.01 %) and KG4 (DD = 89.07 %), and their effects on the quality of PMA were studied. Results manifested that KG3 improved the hardness (from 3017.16 g to 3307.16 g) and protein digestibility (from 49.65 % to 53.01 %) of PMA without reducing the P21, KG2 and KG4 were less effective than KG3, while KG1 led to a significant decline in the hardness and protein digestibility of PMA. The rheological properties and intermolecular force analysis showed that the partially deacetylated KG was more conducive to improving the G' of the protein system during heating and the proportion of covalent bonds in PMA. These findings suggested that partially deacetylated KG was more promising than native or highly deacetylated KG in PMA. Furthermore, scanning electron microscopy revealed that the morphology of KG gradually changed from fine filaments, to coarse filaments, short filaments and granules as DD increased. This study provides a theoretical basis for the application of partially deacetylated KG in PMA.

Development of pea protein nanoparticle/hydrolyzed rice glutelin fibril emulsion gels for encapsulation of curcumin

The potential of using emulsion gels stabilized by binary plant protein nanoparticle mixtures for the encapsulation and delivery of lipophilic nutraceuticals was evaluated. The particle characteristics, physical stability, water diffusivity, microrheology, large amplitude oscillating shear (LAOS) properties, and in vitro digestion of emulsion gels prepared by different ratios of hydrolyzed rice glutelin fibrils (HRGFs) and pea protein nanoparticle (PNP) were characterized. The emulsion gel with P/H = 2:1 (0.84 μm) exhibited the best storage stability and freeze-thaw stability, as seen by the smaller oil droplet size (1.02 and 1.42 μm, respectively). Low-field pulsed NMR indicated that the majority of water in samples was highly mobile. All the samples were predominantly elastic-like materials. The P/H 2:1 emulsion gel had the lowest FI value (6.21 × 10−4 Hz), the highest MVI value (5.57 s/nm2), G′/ G″ values and enclosed area, showing that it had denser 3D network structures, higher stiffness values, and a high sensitivity to changes in strain. Additionally, P/H 2:1 emulsion gel had a relatively high lipid digestibility (96.1 %), curcumin bioaccessibility (58.9 %), and curcumin stability (94.2 %). This study showed that emulsion gels stabilized by binary protein nanoparticle mixtures (PNP/HRGF) have potential as edible delivery systems for lipophilic nutraceuticals.

Oleic acid and whey protein reduced the digestion of oxidized and/or hydroxypropyl starches by changing their properties and microstructure

Fatty acids and protein play a crucial role in reducing starch digestion. To investigate the effect of oleic acid (OA) and whey protein (WP) on the digestion of oxidized and/or hydroxypropyl starches and its mechanism, the changes on digestion, properties and microstructure of starch before and after complexation with OA and WP were analyzed using rapid viscosity analyzer (RVA), rheometer, scanning electron microscope (SEM), Fourier transformation infrared spectroscopy (FT-IR) and X-ray diffractometer (XRD). Results showed that starches with OA and WP showed cooling peaks in RVA curve due to starch-OA-WP complexes formation. Additionally, OA and WP had synergistic effects on the increase of storage modulus (G′), the decrease of gel pore size and digestion of starches. OA and WP had a greater effect on digestion of oxidized hydroxypropyl starch (OHPS) than that of hydroxypropyl starch (HPS) and oxidized starch (OS). Specifically, resistant starch content in HPS, OS and OHPS was increased by 82.41%, 58.67% and 279.18%, respectively, due to OA and WP incorporation. This was attributed to the decrease of solubility and increase of order degree of OHPS caused by OA and WP. Therefore, the appropriate hydrophilic and lipophilic properties of OHPS was helpful to complex with OA and WP.

Digestion of mixed protein gels using elderly static in vitro digestion model: Impact of microstructure on bioaccessibility of vitamins B12 and D3

The intake of food products that provide adequate amounts of nutrients is a strategy to deal with the changes in physiological functions that occur during aging that can lead to malnutrition. In this work heat-set mixed protein gels (MPG) composed of soy protein isolate (SPI) and whey protein isolate (WPI) are developed, with different SPI:WPI ratios (15 g protein isolate/100 g gel) and enriched with vitamins D3 and B12. Different protein ratios formed gels with different microstructures and rheological properties. The gel containing 70 % of WPI had a more homogeneous microstructure. The influence of the MPG microstructure on the digestion and bioaccessibility of proteins and vitamins using elderly static in vitro digestion was evaluated. An important result is that mixing SPI and WPI increased the proteolysis. Regarding vitamins bioaccessibility, vitamin D3 became more bioaccessible after the intestinal phase, and there was no difference in vitamin B12 concentration in the intestinal and gastric phases. Therefore, mixing SPI and WPI to produce MPG resulted in improved digestion of proteins, as well as higher bioaccessibility of the vitamins. The results indicated the MPG are promising protein matrices to be used in food products for the elderly.

Effect of Multi-Mode Divergent Ultrasound Pretreatment on Hardness, Microstructure and Digestion of Acid-Induced Whey Protein Gels.

Whey protein was pretreated with multi-frequency ultrasound in mono-, dual-, and tri-frequency modes. The effect of multi-frequency ultrasound pretreatment on the hardness, chemical forces, and microstructure of acid-induced whey protein gel was investigated. Whey protein gels pretreated with dual- and tri-frequency ultrasound showed higher hardness (p < 0.05) and a denser network than mono-frequency ultrasound and control. Moreover, they had higher hydrophobic interaction and lower disulfide bonds than the control (p < 0.05). The effect of gel properties on digestion was evaluated using an in vitro static model. Whey protein gels pretreated with dual- and tri-frequency ultrasound had a higher proportion of large fragments in the oral boluses than in the control. Large fragments (>3.35 mm) in those samples were resistant to gastric digestion. Moreover, the tri-frequency ultrasound pretreatment of whey protein gel released the least free amino group during gastric digestion. In contrast, whey protein gel with the mono-frequency ultrasound pretreatment released the highest amount of free amino acid group during intestinal digestion. Findings from this study suggests that gel hardness and network density could modulate the digestion behaviors of protein gels.

Microstructure and in vitro digestion of mixed protein gels of soy and whey protein isolates

This study aimed to evaluate the microstructure and in vitro digestion of soy protein isolate (SPI) and whey protein isolate (WPI) mixed gels. Heat-set gels with different SPI/WPI mass ratios (0/100, 25/75, 50/50, 75/25 and 100/0) were produced. Regarding microstructure, the presence of SPI led to the formation of protein agglomerates resembling microgels, with micrometric average sizes. SPI proteins arranged in a highly branched structure, not particulate as WPI-only gel, probably due to a gelation process highly limited by diffusion of protein chains. The variety of network morphologies indicated the high complexity of the interactions among different proteins. The results of small deformation rheology showed the WPI proteins tended to interact preferably with soy proteins, resulting in the early increase in G’. However, this results in a poor soy protein network formation, as reflected in a lower G’ at the end of the cooling process. As for in vitro digestion, data of size exclusion chromatography showed the gastric phase was insufficient to break up the proteins and peptides present in the gel protein networks. The gastric conditions probably caused the “opening” of the protein structures but was limited by the mass transfer due to steric hindrance in the gel network. Regarding the intestinal step, a more rapid digestion was observed, which may be related to the structure of the protein matrices containing SPI, i.e. more porous than the strands of particulate WPI proteins, which probably made the proteins in SPI-containing gels more accessible to the pancreatic enzymes.

Effect of polyphenols from Ascophyllum nodosum seaweeds on the rheology and digestion of corn starch gels and gluten-free bread features

The main objective of this work is to study the effect of polyphenols, from the brown seaweed Ascophyllum nodosum, on the structure and digestion behaviour of gels at two corn starch concentrations (1.95 and 5.00% w/w) as well as the structure, color and texture features of crumbs from gluten-free breads. Adsorption isotherms of polyphenols on native and gelled starches were carried out and modelled by means of Langmuir and Henry models, respectively. The formation and characteristics of tested gels were rheologically monitored by means of heating ramp, time sweep at high temperature, cooling ramp and frequency sweep at 25 °C. Elastic modulus values decreased with the presence of polyphenols. Additionally, the polyphenols significantly decreased the digestion rate, measured by both chemical and rheological procedures, and the final concentration of digested starch. Finally, the presence of polyphenols in breads increased the hardness and chewiness values and decreased the cohesiveness and resilience values as well as the crumb hardening during storage.

Effect of polyphenols on the rheology, microstructure and in vitro digestion of pea protein gels at various pH

Polyphenols exist widely in plants and interact with plant proteins distinctly depending on the environmental pH. This could potentially affect the gelling property of plant proteins and their digestion. In the present study, pea protein suspensions containing 0 %, 0.5 % and 1 % green tea polyphenols (GTP) were heated to form gels at pH5, pH7, and pH8.5. A strain amplitude sweep showed that the storage modulus (G’) and critical strain of pea protein gels decreased with increased GTP concentration at all examined pH. Gelation dynamic showed gelling of pea protein-GTP was delayed at pH7 and pH8.5 compared to the control. Differential scanning calorimetry showed that pea proteins became less heat resistant in the presence of GTP at pH5 and pH7, but not at pH8.5. Ultra-small and small-angle X-ray scattering showed that the radius of gyration of small- and medium-sized aggregates in pea protein gels was increased ∼10–16 % and 22–30 % at pH7 and pH8.5, respectively when 1 % GTP was present. Under such pH conditions, the proportion of structure with a radius of ∼10–200 nm was increased in pea protein-GTP gels based on the volume size distribution. In vitro digestion found the soluble protein content of digesta of pea protein-GTP gels had a 5–8.5 % decrement with the presence of larger peptides when compared to pea protein gels.

Effects of different plant polysaccharides as fat substitutes on the gel properties, microstructure and digestion characteristics of myofibrillar protein

This study aimed to investigate the effects of different plant polysaccharides (inulin, κ-carrageenan, and konjac glucomannan) as fat substitutes on the gel properties, microstructure, and digestion characteristics of myofibrillar protein (MP). The results revealed that incorporating inulin, κ-carrageenan, and konjac glucomannan significantly improved the water holding capacity, texture profiles, and rheological behavior of MP gels while limiting water fluidity. Among them, the MP-konjac glucomannan gel (1%, w/w) showed superior water retention and gel strength, demonstrating the most notable restriction on water translocation. Microstructural analysis observed that the MP gels with inulin, κ-carrageenan, and konjac glucomannan displayed a dense and well-clustered network structure, resulting in a more even distribution and compact gel structure. However, including 1.5% and 2% konjac glucomannan in MP mixed gels resulted in block-like clustering and larger agglomeration. Furthermore, the protein digestibility assessment indicated that polysaccharides incorporation significantly reduced the digestibility of MP, with konjac glucomannan demonstrating higher digestibility compared to inulin and κ-carrageenan groups. Overall, incorporating konjac glucomannan at a 1% incorporation (w/w) can effectively serve as a fat substitute in muscle food. This study will provide valuable insights for utilizing konjac glucomannan as a fat substitute in meat products.

Reversible bonding in thermoplastic elastomer microfluidic platforms for harvestable 3D microvessel networks.

Transplantable ready-made microvessels have therapeutic potential for tissue regeneration and cell replacement therapy. Inspired by the natural rapid angiogenic sprouting of microvessels in vivo, engineered injectable 3D microvessel networks are created using thermoplastic elastomer (TPE) microfluidic devices. The TPE material used here is flexible, optically transparent, and can be robustly yet reversibly bonded to a variety of plastic substrates, making it a versatile choice for microfluidic device fabrication because it overcomes the weak self-adhesion properties and limited manufacturing options of poly(dimethylsiloxane) (PDMS). By leveraging the reversible bonding characteristics of TPE material templates, we present their utility as an organ-on-a-chip platform for forming and handling microvessel networks, and demonstrate their potential for animal-free tissue generation and transplantation in clinical applications. We first show that TPE-based devices have nearly 6-fold higher bonding strength during the cell culture step compared to PDMS-based devices while simultaneously maintaining a full reversible bond to (PS) culture plates, which are widely used for biological cell studies. We also demonstrate the successful generation of perfusable and interconnected 3D microvessel networks using TPE-PS microfluidic devices on both single and multi-vessel loading platforms. Importantly, after removing the TPE slab, microvessel networks remain intact on the PS substrate without any structural damage and can be effectively harvested following gel digestion. The TPE-based organ-on-a-chip platform offers substantial advantages by facilitating the harvesting procedure and maintaining the integrity of microfluidic-engineered microvessels for transplant. To the best of our knowledge, our TPE-based reversible bonding approach marks the first confirmation of successful retrieval of organ-specific vessel segments from the reversibly-bonded TPE microfluidic platform. We anticipate that the method will find applications in organ-on-a-chip and microphysiological system research, particularly in tissue analysis and vessel engraftment, where flexible and reversible bonding can be utilized.

Comparative analyses of adsorbed circulating proteins in the PMMA and PES hemodiafilters in patients on predilution online hemodiafiltration.

Acute and chronic inflammation are common in patients with end-stage kidney disease (ESKD). So, the adsorption of pro-inflammatory cytokines by the hollow fiber of the dialysis membrane has been expected to modify the inflammatory dysregulation in ESKD patients. However, it remains to be determined in detail what molecules of fiber materials can preferably adsorb proteins from the circulating circuit. We aimed this study to analyze directly the adsorbed proteins in the polymethyl methacrylate (PMMA) and polyethersulfone (PES) membranes in patients on predilution online hemodiafiltration (OL-HDF). To compare the adsorbed proteins in the PMMA and PES hemodiafilters membrane, we initially performed predilution OL-HDF using the PES (MFX-25Seco) membrane while then switched to the PMMA (PMF™-A) membrane under the same condition in three patients. We extracted proteins from the collected hemodiafilters by extraction, then SDS-PAGE of the extracted sample, protein isolation, in-gel tryptic digestion, and nano-LC MS/MS analyses. The concentrations of adsorbed proteins from the PMMA and PES membrane extracts were 35.6±7.9 μg/μL and 26.1±9.2 μg/μL. SDS-PAGE analysis revealed distinct variations of adsorbed proteins mainly in the molecular weight between 10 to 25 kDa. By tryptic gel digestion and mass spectrometric analysis, the PMMA membrane exhibited higher adsorptions of β2 microglobulin, dermcidin, retinol-binding protein-4, and lambda-1 light chain than those from the PES membrane. In contrast, amyloid A-1 protein was adsorbed more potently in the PES membrane. Western blot analyses revealed that the PMMA membrane adsorbed interleukin-6 (IL-6) approximately 5 to 118 times compared to the PES membrane. These findings suggest that PMMA-based OL-HDF therapy may be useful in controlling inflammatory status in ESKD patients.

Comparative characterisation of structural, physicochemical and digestive properties of rice starches isolated from novel high‐amylose mutants

SummaryNovel high‐amylose rice mutants with unique starch properties were developed from a low‐amylose rice variety. The objective of this study was to explore the impacts of apparent amylose content and amylopectin structure on the physical and nutritional properties of rice starch by comparing novel mutants with conventional rice varieties. The rice mutants demonstrated a specific amylopectin characteristic, indicating an extremely lower portion of short chains (15.2%–16.5%) than the other rice varieties (27.3%–31.1%). The starch gel prepared from the rice mutant exhibited significantly higher compressive and breaking stress than the other high‐amylose rice variety with a higher apparent amylose content, indicating that amylopectin characteristics markedly influenced the starch gel structure. The rice mutant demonstrated the highest content of undigested starch after 120 min of digestion in raw starch (50.5%) and starch gel (53.0%). The starch from newly developed rice mutants were found to have markedly high resistance to digestion due to its amylopectin structure and formation of harder gel.

Modulating in vitro digestion of whey protein cold-set emulsion gels via gel properties modification with gallic acid and EGCG

Gallic acid (GA) and epigallocatechin gallate (EGCG), cooperated at varied ratios (1:0, 3:1, 1:1, 1:3, and 0:1), were employed to modify gel properties of calcium induced-whey protein emulsion gel. The effects of GA/EGCG on emulsion morphology, as well as gel properties and in vitro digestive behavior of the emulsion gels were investigated. Compared with emulsions without phenolics, GA/EGCG induced slightly smaller particle size and stronger electrostatic repulsion between emulsion droplets. Moreover, GA/EGCG, notably at a ratio of 3:1, promoted electrostatic and hydrophobic interactions between protein molecules and the formation of a compact and filamentous gel microstructure, resulting in a remarkable increment in the gel strength (up to 106 %). Furthermore, in vitro oral digestion, dynamic gastric digestion (using an artificial gastric digestive system, AGDS), and intestinal digestion of the emulsion gels were simulated. Particle size and protein hydrolysis results revealed that GA/EGCG was prone to weaken the physical disintegration of gels, reduce protein hydrolysis, and enhance the stability of emulsified oil droplets during dynamic gastric digestion. As a consequence, delayed release of oil droplets was observed in the gels and more free fatty acids were released in the intestinal digestion, particularly in the gel with GA/EGCG (3:1). These findings would provide novel strategies for application of phenolic compounds in developing protein gel-based delivery systems.

Insights into the in vitro digestibility of pork myofibrillar protein with different ionic polysaccharides from the perspective of gel characteristics.

In this work, the simulated gastrointestinal digestion of myofibrillar protein gels (MPGs) with anionic xanthan (XMP) and sodium alginate (SMP)/cationic chitosan (CSMP)/neutral curdlan (CMP) and konjac (KMP) was investigated to develop muscle-gelled foods with good qualities before and after eating. The results indicated that the neutral CMP and KMP groups had higher gel strength and protein digestibility than the CSMP group. Xanthan and sodium alginate facilitated myosin degradation in gastrointestinal digestion because of the weak wraps between protein and anionic polysaccharides, gaining plentiful peptides (1790 and 1692 respectively) with molecular weights below 2000Da. Chitosan and neutral curdlan could improve the strength of MP gel but inhibited proteolysis and resulted in low contents of released amino acids via the strong cross-linked network blocking trypsin contact. This work provides a theoretical basis for developing low-fat meat products with good qualities and digestion behaviors by simply controlling the ionic types of polysaccharides.