Use of different impregnation methods with chitosan oligosaccharide to improve the quality of ultrasound-assisted immersion frozen sea bass (Lateolabrax maculatus)

This study investigated the effect of chitosan oligosaccharide (COS) as a cryoprotectant on the water holding capacity (WHC), myofibrillar proteins (MPs), and quality of sea bass frozen by ultrasound-assisted immersion freezing (UIF), and also investigated the effect of different impregnation methods: vacuum impregnation (VI), ultrasound-assisted impregnation (UI), and ultrasound-assisted VI (US-VI). The results indicated that compared with general impregnation in deionized water (GWI) samples, the samples impregnated with COS had lower thawing loss, higher whiteness, lower carbonyl content, more stable secondary and tertiary structures, and smaller ice crystal pore size. These results indicate that COS impregnation of sea bass can reduce large ice crystals and decrease proteins aggregation, resulting in better quality. In addition, US-VI in COS (US-VCI) resulted in improved WHC, whiteness, sulfhydryl content, and Ca²⁺-ATPase activity of sea bass because of the joint action of ultrasound and vacuum, as well as more stable secondary structure and fine ice crystals.