Chemical interactions and gel properties of black carp actomyosin affected by MTGase and their relationships

Effects of native starch and modified starches on the textural, rheological and microstructural characteristics of soybean protein gel

The effects of native starch (NS), acetylated starch (AS), and acetylated distarch phosphate (ADSP) on the gel properties of soybean protein thermal gel were investigated using texture analysis, low-field nuclear magnetic resonance (LF-NMR) spectroscopy, dynamic rheometry and scanning electron microscopy. The results of the textural profile analysis showed that 10% ADSP increased the hardness and chewiness of the mixed gel, while NS and AS led to decreases in the textural properties. The results of the LF-NMR analysis indicated that the AS improved the water-holding capacity of the mixed gel due to the transformation of weakly bound water to strongly bound water. During heating and cooling, the rheological profiles of the elastic (G') and viscous modulus (G″) of all the samples exhibited a two-stage pattern of decrease and then increase, and the final values of G' and G″ reached maxima when the ADSP content was 10%. The scanning electron microscopy images showed that the ADSP granules dispersed in the gel network. The integrity of the starch granules was crucial for regulating the properties of the soybean protein gel. These results provided information about the further design and preparation of soybean protein foods containing modified starch.

Physicochemical property, antioxidant activity, and cytoprotective effect of the germinated soybean proteins

Appropriate germination can improve the nutritional value and bioactivity of soybeans; however, few studies have assessed the effect of germination on soybean proteins. This study examined the physicochemical property, antioxidation, and cytoprotective effect of the germinated soybean proteins (Gsp). Gsp was extracted from soybeans which germinated for 0-3 days using the method of alkali-solution and acid-isolation extraction. The results showed that germination could digest soybean proteins into the smaller molecules; enhance the degree of hydrolysis, emulsifiability, and foaming capacity; increase the removal rate of ABTS, DPPH, O 2 - ˙, and ˙OH radical; and decrease the reducing power and lipid peroxidation of Gsp. Additionally, Gsp was able to protect HL-7702 human hepatocyte cells against benzo(a)pyrene (BaP)-induced cytotoxicity through mediating the cell cycle arrest, suppressing apoptosis, and increasing reactive oxygen species (ROS) levels. This work demonstrated that germination could enhance the physicochemical property and antioxidant activity of Gsp, which also displayed the remarkable cytoprotective effect. This study provided a fundamental basis for substantiating dietary of Gsp used for resistance to oxidation and hepatic injury.

Effects of cornstarch on the gel properties of black bean protein isolate

The effects of common starch (CS) and high amylopectin starch (HAS) from corn on the properties of heat induced black bean protein isolate (BBPI) gels prepared by heating at 95°C for 30 min were investigated by using dynamic oscillatory rheometer, texture analyzer, and scanning electron microscopy (SEM). Compared with BBPI alone, the presence of cornstarch (1-4%, wt/vol) could improve storage modulus (G') and textural properties of BBPI (10%, wt/vol) gels. The mixed system of BBPI and 4% (wt/vol) HAS exhibited the highest G' and formed the gel faster and more easily, which resulted in firmer and more elastic gel than BBPI-CS at all starch concentrations. It was possible that HAS had lower pasting temperature and higher viscosity than CS, which was beneficial to the formation of BBPI gel network and strengthened the stability of network structure. Moreover, it might also be related to the synergistic effect between protein and starch. The CS and HAS existed in the BBPI gel network could bind water, leading to the increase in the water-holding capacity (WHC) of mixed gels, especially 4% (wt/vol) HAS, which was related to homogeneous and compact microstructure with small pores.

Rheological Enhancement of Pork Myofibrillar Protein-Lipid Emulsion Composite Gels via Glucose Oxidase Oxidation/Transglutaminase Cross-Linking Pathway

Porcine myofibrillar protein (MP) was modified with glucose oxidase (GluOx)-iron that produces hydroxyl radicals then subjected to microbial transglutaminase (TGase) cross-linking in 0.6 M NaCl at 4 °C. The resulting aggregation and gel formation of MP were examined. The GluOx-mediated oxidation promoted the formation of both soluble and insoluble protein aggregates via disulfide bonds and occlusions of hydrophobic groups. The subsequent TGase treatment converted protein aggregates into highly cross-linked polymers. MP-lipid emulsion composite gels formed with such polymers exhibited markedly enhanced gelling capacity: up to 4.4-fold increases in gel firmness and 3.5-fold increases in gel elasticity over nontreated protein. Microstructural examination showed small oil droplets dispersed in a densely packed gel matrix when MP was oxidatively modified, and the TGase treatment further contributed to such packing. The enzymatic GluOx oxidation/TGase treatment shows promise to improve the textural properties of emulsified meat products.