Peptides in rainbow trout (Oncorhynchus mykiss) muscle subjected to ice storage and cooking

Although proteolysis during post mortem storage is an important factor affecting fish texture, little is known about degradation end-products. This study was performed to investigate the occurrence of low molecular weight peptides (<5 kDa) in post mortem rainbow trout muscle, during ice storage, and to evaluate their stability during cooking. It combined quantitative (amino acid analysis) and qualitative approaches (mass spectrometry). The results showed that muscle of trout was poor in peptides. These were mainly anserine and glutathione. Their concentration was almost unaffected by the seven days of ice storage and vacuum cooking for 5 min at 70 °C. MS analysis revealed a limited but highly reproducible appearance of small peptides in trout muscle during the ice storage and after cooking. The compounds detected by MS analysis remain to be characterised.