Label-free based proteomics analysis of protein changes in frozen whiteleg shrimp (Litopenaeus vannamei) pre-soaked with sodium trimetaphosphate.

Muscle proteins in peeled shrimp (Litopenaeus vannamei) are known to be unstable and prone to denaturation affected by freezing and frozen storage. In this study, label-free proteomics were performed to explore the stabilization of frozen (30 days at -18 °C) shrimp muscle proteins when a pre-soaking treatment with distilled water (DW)- or sodium trimetaphosphate (ST) was applied; comparison to fresh samples (FS) was carried out. In total, 163 differentially abundant proteins (DAPs) were down-regulated in DW batch when compared to FS, these including ribosomal proteins, actins, myosin, paramyosin, myosin heavy chains, and tropomyosin; interestingly, most of these DAPs (181 proteins) were up-regulated in ST batch when compared to DW shrimp, mainly due to the incorporation of ST into muscle tissues. The results revealed the decreased protein degradation resulting from the reduced damage from ice-crystal growth. Gene ontology (GO) analysis suggested that these DAPs were mainly involved in catalytic activity, binding, and metabolic processes. Kyoto encyclopedia of genes and genomes (KEGG) results indicated that many pathways, including phototransduction, metabolic, and ribosomal pathways that interacted with phosphoglycerate mutase, actins, and ribosomal proteins were altered. Additionally, Eukaryotic clusters of orthologous group (KOG) results confirmed that incorporated ST maintained the stability of these DAPs in shrimp muscle, especially for cytoskeleton proteins, and retarded the degradation of muscle proteins during frozen storage.