The effect of multiple freeze–thaw cycles on protein oxidation and quality of Trachurus murphyi

Abstract

In this study, we investigated the changes in protein oxidation and quality of Trachurus murphyi due to repeated freezing and thawing (F-T) during refrigerated storage using physicochemical and texture profile analysis. The results showed that protein oxidation occurred through the formation of carbonyl groups and reduction in sulfhydryl content and Ca2+-ATPase activity. The oxidative modifications in myofibrillar protein gels were evaluated using SDS-polyacrylamide gel electrophoresis that observed along with a decrease in the intensity of the 75, 48, and 35 kDa bands. Color, water migration, and texture profile were used to evaluate the quality of T. murphyi. As shown by the Atomic force microscopy analysis (AFM) results, the length of myofibrils in the sample increased with freeze–thawing from 1.08 µm at the second cycle of the freezing and thawing (F-T 2) to 1.54 µm at the eighth cycle of the freezing and thawing (F-T 8), whereas the height of myofibrils decreased from 111.8 to 74.87 nm. Raman spectroscopy further revealed that the α-helix content was reduced, along with the contents of β-turns, β-sheets, and random coils of myofibrillar protein with increasing freeze–thaw cycles. These results indicated that multiple freezing–thawing decreased T. murphyi quality during refrigerated storage. Practical applications The study was performed to investigate the effect of freeze–thaw cycles on the protein oxidation and quality of T. murphyi. We provided the method of the evaluation for the oxidation and the quality of freeze and thaw fish, and a theoretical basis for freezing and thawing fish products.