Protein oxidation and tandem mass tag-based proteomic analysis in the dorsal muscle of farmed obscure pufferfish subjected to multiple freeze-thaw cycles

The objective of this study was to determine the oxidative stability and proteome profile of dorsal muscle of frozen obscure pufferfish subjected to repeated freeze-thaw cycles (FTC). Twenty frozen fish were filleted (2 cm x 2 cm x 2 cm) and subjected to FTC. Protein oxidation, lipid oxidation, antioxidant enzyme activities (AEA), and proteome profile were assessed. The results showed that the carbonyl content and TBARS value increased (p <.05), while sulfhydryl content and AEA decreased (p <.05) as FTC increased. SDS-PAGE analysis revealed that FTC induced significant alterations in disulfide linkage and fragments. There were significant (p <.05) correlations between lipid oxidation, AEA, and protein oxidation. A total of 19 differentially abundant proteins were identified, of which L-lactate dehydrogenase and other proteins could be potential biomarkers for pufferfish subjected to FTC. Bioinformatic analysis revealed that these proteins are mainly involved in membrane structure, respiratory chain, and apoptosis. Practical applications Pufferfish is popular in many Asian countries for its palatable flavor and frozen storage is the most common way for its preservation. However, repeated freeze-thaw cycles (FTC) remain a core issue in frozen products, which lead to various changes in protein and consequently have a serious impact on food quality. In this study, the extent of protein oxidation (PO) and proteomic changes in pufferfish muscle subjected to FTC was investigated. The initiation of PO correlates with increased lipid oxidation and decreased antioxidant enzyme activity, which may be used to control the PO. The differentially abundant proteins identified may be used to distinguish the frozen products subjected to different FTC. Understanding the molecular mechanism of protein changes induced by FTC will enable us to achieve the target-control and to preserve the frozen aquatic products with better quality.