Changes in the structure and functional properties of soybean isolate protein: Effects of different modification methods.

Soybean protein isolate (SPI) is an important plant protein in food processing; however, its spherical structure prevents the exposure of its hydrophobic residues and affects its functional properties. In this study, we elucidate the effects of deamidation, phosphorylation, and glycosylation on the structure (Fourier-transform infrared spectroscopy, circular dichroism, fluorescence, and scanning electron microscopy) and functional properties (solubility, emulsifying activity index (EAI), and emulsifying stability index (ESI)) of SPI. The zeta potentials of the deamidated, phosphorylated, and glycosylated (DSPI, PSPI, and MSPI, respectively) samples decreased significantly (p < 0.05) relative to those of SPI. The functional properties of the modified SPI samples were improved, with MSPI-2 showing the best solubility (86.73 ± 0.34%), EAI (118.89 ± 0.73 m2/g), and ESI (273.33 ± 0.59 min). Moreover, the effects of the three modifications on the SPI functional properties increase in the order MSPI > PSPI > DSPI. These results provide a theoretical understanding the relationship between the modifications and SPI structure.

Construction and characterization of Pickering emulsions stabilized by soy protein hydrolysate microgel particles and quercetin-loaded performance in vitro digestion.

Food-grade Pickering emulsions stabilized by protein microgel particles have received increasing attentions owing to their potential applications in the food industry. Herein, soy protein hydrolysate microgel particles (SPHMs) produced at various pH (3, 5, 7, and 9) with and without ultrasonication were used to stabilize Pickering emulsions. Compared with those prepared using ultrasonication at pH 3-7, SPHMs prepared using ultrasonication at pH 9 showed excellent amphiphility at the oil-water interface and a superior ability to reduce interfacial tension. The Pickering emulsion stabilized by the latter SPHMs displayed a small particle size and a high net charge on the droplet surface, formed a dense honeycomb network interfacial layer with high viscoelasticity and adsorbed protein content, and experienced no visually detectable creaming during storage for 21 days, i.e., exhibited optimum colloidal stability. Furthermore, the above emulsion featured a quercetin encapsulation efficiency of 89.45 % and was capable of sustainable release, achieving a low free fatty acid release efficiency of 61 % and a relatively high quercetin bioaccessibility of 65 % in in vitro simulated digestion experiments. Thus, this work inspires the use of SPHMs in emulsion-based functional foods.

Whey protein isolate-phytosterols nanoparticles: Preparation, characterization, and stabilized food-grade pickering emulsions.

The preparation of whey protein isolate (WPI) particles by heat induction usually reduces both protein nutritional value and functionality. In this study, WPI and phytosterols (PSs) were used to prepare whey protein isolate-phytosterol (WPS) nanoparticles as stabilizers of oil-in-water Pickering emulsions, and the effects of PSs on the structure and function of the nanoparticles were studied. The results showed that the WPI and PSs combine through non-covalent bonding, which alters the nanoparticle structure and function. When the WPI/PSs mass ratio was 25:2, the nanoparticles (WPS-4) exhibited excellent interfacial wettability, emulsification stability, and antioxidant activity. The nanoparticles formed thick and dense interfacial films on the droplet surfaces to protect them, and the emulsion stabilized with the WPS-4 nanoparticles exhibited the best storage stability and oxidation stability. The emulsion can also reduce the digestion of lipids. These results provide a theoretical basis for the application of WPS nanoparticles.

Effects of inducer type and concentration on the formation mechanism of W/O/W double emulsion gels.

Insulin (INS, hydrophilic) and quercetin (Q, hydrophobic) have broad biological benefits; however, their application is limited because of their instability and poor bioaccessibility. Thus, in this study, water-in-oil-in-water (W/O/W) double emulsion gels based on black bean protein-sodium alginate Maillard conjugate-stabilized double emulsions were fabricated using three different inducers. The water holding capacity (WHC), intermolecular interaction forces, INS and Q encapsulation efficiencies (EEs), rheological and textural properties, microstructures, and structures were influenced by both inducer type [CaCl2, glucolactone (GDL), and glutamine transaminase (TGase)] and concentration. The addition of each inducer significantly increased the WHC, INS, and Q EEs, and textural properties of the emulsion gel. Moreover, the rheological behavior analysis showed that all the emulsion gels exhibited marked elastic behavior. These results will help develop an emulsion gel functional carrier based on a black soybean protein-carbohydrate-stabilized W/O/W double emulsion for the targeted and sustained release of drugs.

Co-delivery of insulin and quercetin in W/O/W double emulsions stabilized by different hydrophilic emulsifiers.

Insulin (hydrophilic) and quercetin (hydrophobic) have broad biological benefits; however, their rapid hydrolysis (via protease degradation) during digestion hinders their stability and delivery for absorption before degrading. In this study, we encapsulated insulin and quercetin using a self-assembled water-in-oil-in-water (W/O/W) double emulsion. We prepared the co-delivery emulsion by two-step emulsification and investigated the effects of the type of hydrophilic emulsifier for the outer water phase on the physicochemical properties, stability, and digestive properties. The black-bean-protein-stabilized W/O/W double emulsion had a higher absolute zeta potential value (52.80 mV), higher encapsulation efficiency (insulin: 95.7%, quercetin: 93.4%), lower viscosity, better emulsifying properties (EAI: 122.26 m2/g, ESI: 224 min), and lower levels of hydroperoxides (0.86 mmol/L) and TBARS (25.80 µmol/L) than emulsions stabilized by other hydrophilic emulsifiers. The emulsion yielded a 2.60- and 4.56-fold increase in the bioaccessibility of insulin and quercetin, respectively, while increasing their chemical stability and solubility under simulated gastrointestinal conditions.

Effect of carbohydrate type on the structural and functional properties of Maillard-reacted black bean protein.

Protein from black beans (Phaseolus vulgaris L.) has good solubility, emulsification, and antioxidant properties, with significant potential applications in the food industry. Maillard-reaction-mediated dry-heat glycosylation is a relatively safe modification method to improve the functional properties of black bean protein (BBP). Here, Maillard-reacted conjugates were prepared by applying 24-h dry-heating to induce a reaction between BBP and one of three carbohydrates (dextran, chitosan, and sodium alginate) at 70°C and 79% relative humidity. The resulting Maillard conjugates were designated as BBP-Dex, BBP-Ch, and BBP-SA, respectively. The formation of each Maillard conjugate was characterized by analyzing the grafting degree, free sulfhydryl (SH) groups content, and surface hydrophobicity, as well as the results of Fourier-transform infrared (FTIR) spectroscopy and fluorescence spectroscopy. The FTIR and fluorescence spectroscopy results provided information on the formation of the Maillard conjugates. The BBP-SA conjugate had a higher grafting degree and SH group content than the other two conjugates. The solubility, emulsifying properties, and antioxidant properties of the BBP were significantly improved after the Maillard reaction (p < 0.05). Moreover, the physicochemical and functional properties of the conjugates were superior to those of the BBP-carbohydrate mixtures, indicating that covalent interactions may be stronger than noncovalent interactions. This study provides theoretical guidance for future research on protein-carbohydrate conjugates. PRACTICAL APPLICATION: This study has great potential applications in the development of new multi-functional food ingredients and the realization of functional factor homeostasis, and provides scientific and theoretical bases for the application of protein-carbohydrate conjugate in the field of functional food.

Chaetochromones A and B, two new polyketides from the fungus Chaetomium indicum (CBS.860.68).

Chaetochromones A (1) and B (2), two novel polyketides, were isolated from the crude extract of fungus Chaetomium indicum (CBS.860.68) together with three known analogues PI-3(3), PI-4 (4) and SB236050 (5). The structures of these compounds were determined by HRESI-MS and NMR experiments. Chaetochromones A (1) and B (2) are a member of the polyketides family, which might originate from a similar biogenetic pathway as the known compounds PI-3 (3), PI-4 (4) and SB236050 (5). The biological activities of these secondary metabolites were evaluated against eight plant pathogens, including Alternaria alternata, Ilyonectria radicicola, Trichoderma viride pers, Aspergillus niger, Fusarium verticillioide, Irpex lacteus (Fr.), Poria placenta (Fr.) Cooke and Coriolus versicolor (L.) Quél. Compound 1 displayed moderate inhibitory rate (>60%) against the brown rot fungus Poria placenta (Fr.) Cooke, which causes significant wood decay. In addition, the cytotoxic activities against three cancer cell lines A549, MDA-MB-231, PANC-1 were also tested, without any inhibitory activities being detected.