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.

The differential non-covalent binding of epicatechin and chlorogenic acid to ovotransferrin and the enhancing efficiency of immunomodulatory activity.

Seeking safe and environmentally friendly natural immunomodulators is a pressing requirement of humanity. This study investigated the differential binding characteristics of two polar polyphenols (PP), namely epicatechin (EC) and chlorogenic acid (CA), to ovotransferrin (OVT), and explored the relationship between structural transformations and immunomodulatory activity of OVT-PP complexes. Results showed that CA exhibited a stronger affinity for OVT than EC, mainly driven by hydrogen bonds and van der Waals forces. Complexation-induced conformational variations in OVT, including static fluorescence quenching, increased microenvironment polarity surrounding tryptophan and tyrosine residues, and the transition from disordered α-helix to stable ß-sheet. Furthermore, the structural conformation transformation of OVT-PP complexes facilitated the enhancement of immunomodulatory activity, with the OVT-CA (10:2) complex demonstrating the best immunomodulatory activity. Principal component analysis (PCA) and Pearson correlation analysis revealed the immunomodulatory activities of the OVT-PP complexes were influenced by surface hydrophobicity (negatively correlated), ß-sheet percentage and polyphenol binding constants. It could be inferred that PP complexation increased the surface polarity of OVT, consequently enhancing its immunomodulatory activity by promoting cell membrane affinity and antigen recognition. This study provides valuable guidance for effectively utilizing polyphenol-protein complexes in enhancing immunomodulatory activity.

Cell-Free Supernatant of Lactiplantibacillus plantarum 90: A Clean Label Strategy to Improve the Shelf Life of Ground Beef Gel and Its Bacteriostatic Mechanism.

Lactic acid bacteria metabolites can be used as a clean-label strategy for meat products due to their "natural" and antibacterial properties. In this study, the feasibility of using cell-free supernatant of Lactiplantibacillus plantarum 90 (LCFS) as a natural antibacterial agent in ground beef was investigated. The sensitivity of LCFS to pH, heat and protease, as well as the changes of enzyme activities of alkaline phosphatase (AKP) and Na+/K+-ATP together with the morphology of indicator bacteria after LCFS treatment, were analyzed to further explore the antibacterial mechanism of LCFS. The results showed that the addition of 0.5% LCFS inhibited the growth of microorganisms in the ground beef gel and extended its shelf-life without affecting the pH, cooking loss, color and texture characteristics of the product. In addition, the antibacterial effect of LCFS was the result of the interaction of organic acids and protein antibacterial substances in destroying cell structures (cell membrane, etc.) to achieve the purpose of bacteriostasis. This study provides a theoretical basis for the application of LCFS in meat products and a new clean-label strategy for the food industry.

Gel properties of okara dietary fiber-fortified soy protein isolate gel with/without NaCl.

BACKGROUND: Soy protein isolate (SPI) is widely used as an alternative to animal-based protein, and its gelling property is essential for producing plant protein-based foods. Insoluble dietary fiber has been used to improve the properties of protein gels. RESULTS: Effects of partial replacement of SPI by okara dietary fiber (ODF) on the gelling properties of ODF-fortified SPI gels with and without 0.1 m NaCl were investigated. The presence of ODF hindered the SPI self-aggregation and reduced the surface hydrophobicity of SPI. The presence of ODF reduced the hydrophobic interaction and improved the proportion of disulfide bonds in the gels. In the microstructure, the swollen ODF promoted the local aggregation of SPI at 0.1 m NaCl. Texture profile analysis showed that 5% and 10% ODF improved the SPI gel hardness in the absence of NaCl, whereas only 5% ODF improved the gel hardness at 0.1 m NaCl. The results of low-field nuclear magnetic resonance imaging revealed that ODF shortened the T2 relaxation time of the free water in the gel. The gel of ODF-10 had the highest storage modulus. CONCLUSION: Using an appropriate amount of ODF to replace SPI could improve the quality of SPI gel and increase the dietary fiber content in the product. In addition, the appropriate ratio of ODF/SPI varied in different solution environments. © 2022 Society of Chemical Industry.

Influence of soybean dietary fiber with varying particle sizes and transglutaminase on soy protein isolate gel.

In this study, soybean dietary fiber (DF) was used as nutritional supplement and gel enhancer in soy protein isolate (SPI) gels. The effects of DF particle sizes (100-mesh, DF100; 200-mesh, DF200), DF content and transglutaminase (TGase) addition on the gel properties of DF-enriched soy protein isolate (DSPI) gels were studied. The results showed that 10 % DF100 was beneficial for improving gel hardness (from 137.61 to 148.86 g), but caused the declined gel cohesiveness (from 0.87 to 0.80). with the use of 10 % DF200, the gel cohesiveness was improved from 0.80 to 0.83. However, the water holding capacity of DSPI gels containing DF200 was poor and the ionic and hydrogen bonds were reduced. When 20 % DF100 was added, the overall gel quality decreased. The effect of TGase depended on situations. When DF was well wrapped, the addition of TGase improved the textural property and the ß-turn proportion (from 40.22 % to 42.88 %) of DSPI gels owing to the enhanced protein cross-linking. While when SPI was separated by excessive amount of DF, the addition of TGase caused the deteriorated gel properties because TGase-induced local protein aggregation destroyed the gel continuousness. This research will guide the rational application of DF in gel products.

Study on gel properties of lysozyme-free egg white before and after Lactiplantibacillus plantarum fermentation.

BACKGROUND: Isolation of lysozyme from egg white (EW) using ion exchange resin adsorption method generates large quantities of lysozyme-free egg white (LFEW) with poor gelling property. To maximize the applications of LFEW, the effect of Lactiplantibacillus plantarum fermentation on the gel properties of LFEW was investigated in this study. RESULTS: The fermentation efficiency of LFEW with lysozyme removed was significantly improved, and the sugar removal rate (2 g kg-1 Lactiplantibacillus plantarum, 37 °C, 7 h) was more than 90%. Removal of lysozyme resulted in increased stability and surface hydrophobicity of EW. After Lactiplantibacillus plantarum fermentation, the stability of EW decreased, and the average particle size and surface hydrophobicity increased. In addition, by comparing the gel properties of EW and LFEW before and after fermentation at different pH, it was found that the hardness, elasticity, and water holding capacity (WHC) of EW gel increased significantly. The removal of lysozyme effectively improved the WHC and springiness of the EW gel and promoted the formation of a denser network structure with smaller pores. After Lactiplantibacillus plantarum fermentation treatment, LFEW gel hardness decreased, with loose and porous network structure, no browning occurred after autoclaving. CONCLUSION: This study provided the direction and theoretical basis for producing a fermented LFEW gel with pleasing texture and appearance. © 2022 Society of Chemical Industry.

Enhancing gelling properties of high internal phase emulsion-filled chicken gels: Effect of droplet fractions and salts.

Effects of high internal phase emulsion (HIPE) stabilized by egg yolk-modified starch complex on the gelling properties of chicken gels with or without sodium chloride (NaCl)/sodium tripolyphosphate (TP) were studied. The addition of 30 % HIPE increased the hardness from 376 g to 590 g. The NaCl addition further improved textural and viscoelastic properties compared with the gels without NaCl. 30 % HIPE-filled gels with salts (NaCl and TP) has the highest hardness (3562 g) and the lowest cooking loss (3.41 %). Fourier transform infrared spectra (FTIR) revealed that salts, especially TP, could promote the transition of α-helices to ß-sheets structure. Moreover, the chicken gels with TP had higher acyl chain disorder. In summary, the co-addition of HIPE and salt (NaCl/TP) has a positive effect on the formation of chicken gel, thereby providing potential applications in comminuted meat products.

Dual role (promotion and inhibition) of transglutaminase in mediating myofibrillar protein gelation under malondialdehyde-induced oxidative stress.

This study investigated the effects of transglutaminase (TGase) on the properties of myofibrillar protein (MP) and its heat-induced gels under malondialdehyde (MDA)-induced oxidation. The physicochemical characteristics, protein aggregation and rheological properties of MP were assessed. The gelling behaviours of MP were analysed with measurements of gel strength, cooking loss, microstructure and secondary structure. Under varying degrees of MDA oxidation, the addition of TGase always led to changes in the tertiary structure, loss of free amine and thiol groups, crosslinking of the myosin heavy chain, and decreasing solubility. However, the effect of TGase on MP gel quality differed. At 6 mmol/L MDA, the addition of TGase reduced the quality of MP gels by increasing cooking loss. However, at 12 mmol/L MDA, TGase reduced both the cooking loss and gel strength.

The gelation properties of myofibrillar proteins prepared with malondialdehyde and (-)-epigallocatechin-3-gallate.

Impact of malondialdehyde (MDA) and (-)-Epigallocatechin-3-gallate (EGCG) on gelling properties of myofibrillar proteins (MPs) was investigated. Addition of 6 mM MDA enhanced molecular interactions of proteins, thus the strength and elastic modulus (G') of gel were improved. EGCG addition aggravated gel quality deterioration due to further modification of MPs induced by EGCG. Addition of 12 mM MDA jeopardized gel quality according to the increasing of strength and G', but the decreasing of water-holding capacity (WHC), and the collapse of microstructure. Nevertheless, EGCG reacted with MDA forming EGCG-MDA adducts, hence improved gel quality, which was supported by the decreasing of strength, but the increasing of WHC, and the repaired microstructure of gel at 12 mM MDA. Addition of 24 mM MDA severely jeopardized gel quality, which became even worse due to EGCG addition. This work is helpful to understand the impact of MDA and polyphenols on the gel-forming capacity of MPs.

(-)-Epigallocatechin-3-gallate-mediated formation of myofibrillar protein emulsion gels under malondialdehyde-induced oxidative stress.

The quality of meat products is influenced by protein oxidation. Understanding the effects of antioxidant polyphenols and oxidizing lipoperoxides on myofibrillar proteins is essential for controlling the quality of meat products. This study was designed to investigate the epigallocatechin-3-gallate (EGCG)-mediated formation of myofibrillar protein emulsion gels under malondialdehyde (MDA)-induced oxidative stress. Low MDA concentrations (3 and 6 mM) improved the water-holding capacity, strength, elasticity, and emulsifying properties of gels due to the enhanced protein-protein interactions via MDA. The addition of EGCG reduced the overall properties of the emulsion gel due to further modification of the proteins. At a high concentration of MDA (12 mM), there was excessive cross-linking and unfolding of myofibrillar proteins, which led to a compact gel structure, and reduced the overall properties of the gel. In this situation, the addition of EGCG protected myofibrillar proteins from modifications induced by MDA and improved the quality of emulsion gels.

Inhibition of Epigallocatechin-3-gallate/Protein Interaction by Methyl-ß-cyclodextrin in Myofibrillar Protein Emulsion Gels under Oxidative Stress.

Nowadays, natural antioxidants abundant in polyphenols have been widely used to substitute synthetic antioxidants in meat products. In general, high doses of natural antioxidants are required to provide comparative antioxidant effects as synthetic antioxidants. Noticeably, the qualities of meat products can be jeopardized due to interactions between polyphenols and myofibrillar proteins (MPs). In this study, methyl-ß-cyclodextrin was used to increase the polyphenol loading amount by preventing interactions between polyphenols and proteins. Solubility, electrophoresis, fluorescence spectroscopy, and surface hydrophobicity analyses indicated that methyl-ß-cyclodextrin could dose-dependently inhibit epigallocatechin-3-gallate-induced attacks on MPs under oxidative stress. Gel strength, cooking loss, confocal laser scanning microscopy, dynamic rheological testing, and Raman spectrum during gelation were further analyzed to investigate the effects of methyl-ß-cyclodextrin on the qualities of epigallocatechin-3-gallate-treated emulsion gel. Methyl-ß-cyclodextrin addition prevented modification of the secondary structure of MPs caused by epigallocatechin-3-gallate. In consequence, the gel and emulsifying properties of MPs were significantly improved. Moreover, ß-cyclodextrins could partly inhibit oxidative attacks on MPs and thus increase their solubility. These results indicated that methyl-ß-cyclodextrin addition effectively enhanced epigallocatechin-3-gallate loading capacity in meat products.

Inhibition of interaction between epigallocatechin-3-gallate and myofibrillar protein by cyclodextrin derivatives improves gel quality under oxidative stress.

High levels of polyphenols can interact with myofibrillar proteins (MPs), causing damage to a MP emulsion gel. In this study, ß-cyclodextrins were used to reduce covalent and non-covalent interaction between epigallocatechin-3-gallate (EGCG) and MPs under oxidative stress. The loss of both thiol and free amine groups and the unfolding of MPs caused by EGCG (80 µM/g protein) were significantly prevented by ß-cyclodextrins, and the structural stability and solubility were improved. MP emulsion gel treated with EGCG (80 µM/g protein) had the highest cooking loss (68.64%) and gel strength (0.51 N). Addition of ß-cyclodextrins significantly reduced cooking loss (26.24-58.20%) and improved gel strength (0.31-0.41 N) of MP emulsion gel jeopardized by EGCG under oxidative stress. Damage to the emulsifying properties of MPs caused by EGCG was significantly prevented by addition of ß-cyclodextrins. ß-cyclodextrins reduced interaction between EGCG and MPs in the order Methyl-ß-cyclodextrin > (2-Hydroxypropyl)-ß-cyclodextrin > ß-cyclodextrin. In absence of EGCG, addition of ß-cyclodextrins partly protected MPs from oxidative attack and improved its solubility. It is concluded that ß-cyclodextrins does not markedly reduce the antioxidant ability of EGCG according to carbonyl analysis, and can effectively increase EGCG loading to potentially provide more durable antioxidant effect for meat products during processing, transportation and storage.