Effects of Cathepsins on Gel Strength and Water-Holding Capacity of Myofibrillar Protein Gels from Bighead Carp (Aristichthys nobilis) under a Hydroxyl Radical-Generation Oxidizing System

Abstract

This study investigates the effects of cathepsins on the gel strength and water-holding capacity (WHC) of myofibrillar protein gels from bighead carp (Aristichthys nobilis) under a hydroxyl radical-generation oxidizing system. The myofibrillar proteins were divided into control group (with cathepsins) and E64 group (without cathepsins). The changes of cathepsin B and cathepsin L activities, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), protein oxidation (total sulfhydryl and carbonyl contents), and chemical interactions (nonspecific association, ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfides) of myofibrillar protein and gels, as well as the gel strength and WHC of two groups under 0–100 mM H2O2, were measured. The results indicated that mild oxidation (10 mM H2O2) made a better gel strength and WHC. Cathepsin B and L activities decreased with increasing H2O2 concentrations but their effects on myofibrillar protein degradation still existed during 0.1–50 mM H2O2, which was expressed by higher carbonyl contents and ionic bonds at 0.1 and 50 mM H2O2, higher total sulfhydryl contents at 0 mM H2O2, and a lower intensity of MHC and actin of the control group than the E64 group. Besides more protein degradation, cathepsin proteolysis also resulted in lower gel strength and WHC in control gels than E64 gels under mild oxidation, which could be explained by lower hydrophobic interaction and moderate disulfides bonds between gel protein molecules of control gels.

Effect of Faba Bean Isolate and Microbial Transglutaminase on Rheological Properties of Pork Myofibrillar Protein Gel and Physicochemical and Textural Properties of Reduced-Salt, Low-Fat Pork Model Sausages

“…The protein surface hydrophobicity is closely related to the WHC of protein structure; higher water retention tends to be associated with a higher surface hydrophobicity ( Lee and Chin, 2020 ; Zayas, 1997 ). High hydrophobicity can contribute to improve WHC and GS by binding proteins and stabilizing the three-dimensional structure of gel ( Lu et al, 2022 ). Chen et al (2023) reported that the surface hydrophobicity and WHC of MP extracted from yellow croaker increased with increasing pea protein concentration.…”

Optimizing preparation of low-NaCl protein gels from goose meat and understanding synergistic effects of pH/NaCl in improving gel characteristics

“…The synergistic effects between MgCl 2 concentration and heating temperature also significantly affect the gel's WHC. As the temperature rises, heat-treated proteins denature, unfold, and expose their internal hydrophobic groups, thereby increasing their affinity for water molecules and ensuring stability during centrifugation ( Lu, Liang, Zhang, & Wen, 2022 ). Moreover, divalent Mg 2+ ions and exposed sulfhydryl groups can form disulfide bonds, producing cross-linking structures, favoring protein aggregation, enhancing interactions between proteins, and between protein and water, and consequently, enhancing the protein network and gel strength.…”

Unrinsed Nemipterus virgatus surimi provides more nutrients than rinsed surimi and helps recover immunosuppressed mice treated with cyclophosphamide

“…Although the rinsing process causes nutrient loss, it also imparts some beneficial properties to the gel formation of surimi products. The water‐soluble proteins lost during rinsing include (i) myosin, which binds to myogenic fibronectin and thus interferes with the formation of a firm gel network, resulting in poor gelation of the surimi; 41 (ii) myoglobin and hemoglobin, which affect the appearance and gel quality of the surimi; 42,43 (iii) several proteases that affect the deterioration of surimi during gel formation; 44,45 (iv) some of the proteases that affect the deterioration of gel formation of surimi (proteasome subunit alpha type‐2, 3, 4, 5, 7, low‐molecular‐weight phosphotyrosine protein phosphatase, etc. ); 46,47 and (v) some of the enzymes associated with the oxidation of proteins during storage of surimi (glycogen phosphorylase muscle form, creatine kinase M‐type, pyruvate kinase M, fructose‐bisphosphate aldolase A) 48,49 .…”