Combining soy protein isolate and sorbitol as cryoprotectants for portuguese oysters (Crassostrea angulata) and investigating the effect on ice crystal damage

Abstract

Freezing and thawing often cause significant damage to the muscle tissue of seafood products, reducing their quality and shelf life. This study investigated the combined effects of soy protein isolate (SPI) and sorbitol (So) to mitigate freezing damage in portuguese oysters. A single-factor analysis was performed to determine the optimal concentrations of SPI (1 %–9 %), So (1 %–9 %), and soaking times (30–90 min) based on the steaming loss. An orthogonal experimental design further assessed the combined effects of these factors. The results demonstrated that the combination of 6.0 % SPI and 4.0 % So reduced steaming loss by 10 % and oxidative damage by 0.17 mg MDA/kg. It minimized ice crystal formation in oyster muscle tissue, reduced Ca²⁺-ATPase inactivation, and decreased total sulfhydryl group loss. These findings indicate that the SPI–So composite effectively preserves the structural and functional properties of frozen oysters, offering a promising natural cryoprotectant for the seafood industry.