Hydrophobic/disulfide bonds-driven self-assembly hydrogels of sarcoplasmic protein recovered from surimi rinsing...

Surimi processing generates large amount of rinsing water abundant in sarcoplasmic protein(SP); its recycling is crucial for national low-carbon strategies. This study recovered SP through distinct methods: heating-induced flocculation(HSP), pH-shifting flocculation(PHSP), and pH-shifting/chitosan-assisted flocculation(PHCSP), and investigated their textural and rheological characteristics. The results showed that all SP samples formed aggregates or gel networks. Specially, PHCSP had the strongest gel strength(333.26 ± 89.66 g·cm), due to the aggregation of protein molecules induced by chitosan-protein interaction to form a more stable three-dimensional network, which also improved the water-holding capacity of the hydrogel(92.29 %). The rheological data revealed that three SP aquatic systems were non-Newtonian fluids, and the dynamic entangled network was destroyed and the shear-thinning behavior was more pronounced as the shear rate increased. PHCSP showed higher storage modulus and apparent viscosity than others, indicating better elasticity and viscosity. Moreover, based on Winter-Chambon scaling law, the gel transition concentrations were simulated to be 28 mg/mL(HSP), 25 mg/mL(PHSP), and 22 mg/mL(PHCSP), indicating PHCSP formed gels more easily. Additionally, PHCSP had more disulfide bonds and hydrophobic interactions as the main forces than other samples, possibly attributed to the addition of chitosan. PHCSP and PHSP gels had similar ionic and hydrogen bonds and stronger than HSP, due to PHCSP and PHSP undergoing an acid shift to increase ionic strength, while HSP undergoing heat treatment to decrease the aforementioned bonds. These results elucidate how recovery methods influence protein gelation properties, laying a foundation for SP recycling and advancing surimi processing toward green and low-carbon objectives.