Abstract
Oxidation and hydrolysis of lipids and autolysis in salted mackerel Scomber japonicus were investigated. Filleted mackerel which had been salted for 10 days were divided into two groups. One of them was not packaged, the other was packaged with plastic film along with an oxygen absorber, both were stored for 56 days at ambient temperature.
During the 10 days of salting, the peroxide value (POV) of lipid of the mackerel increased. However, the oxidized acid content and the fatty acid composition of the lipid did not change during the 10-day salting period. The bulk of polar lipid was hydrolyzed to release free fatty acids during salting. Contents of free amino acids in the muscle increased in varying extents due to autolysis, with some exceptional cases. Histidine and taurine decreased in the contents in the first 7 days of salting.
During storage for 56 days, moisture content in the non-packaged salted product decreased from 49% to 39%, while that in the packaged salted one remained unchanged. Lipid oxidation in the non-packaged product proceeded rapidly as judged by POV, oxidized acid content. Highly unsaturated fatty acids of lipid decreased in amount. But the packaged product underwent little lipid oxidation. Total extractive nitrogen and free amino acid contents increased slowly in the non-packaged product, but rapidly in the packaged one. These findings, show that autolysis in the salted mackerel proceeds rapidly during storage at an ambient temperature, but is inhibited markedly when the moisture content of the product decreases to some extent due to drying.
