Influence of frozen storage and defrosting on the chemical and nutritional quality of sardine (Clupea pilchardus)

Studies were carried out on the changes in solubility in SDS + beta-mercaptoethanol, the -SH group content, the amino acid and the fatty acid compositions, and nutritional quality of the muscle protein following freezing, storage at -20 degrees C and conventional defrosting of sardines (Clupea pilchardus). During the processes, 8% of the total SH- group content was lost and there was a slight drop in solubility in SDS + beta-mercaptoethanol. The amino acids which dropped to the greatest extent were the S-amino acids, followed by histidine, tyrosine, leucine, lysine and phenylalanin. The C22:6/C16:0 ratio dropped and this was considered to be related to oxidation phenomena. The digestibility of protein, biological value and net protein utilization (NPU) also dropped as a result of the processes studied.