Biochemical characterization of abnormally softened sardine “soggy meat” during the spring spawning migration

Abstract “Soggy meat”, which is abnormally softened crushed sardine meat, is often detected in canned sardines seasoned with tomato chili sauce. As soggy meat represents lysed and decomposed tissue, we examined protease activity in the sardine meat during the spawning season. Abnormally soft sardine meat is often found in canned sardine meat from fish caught during the spring and landed at Choshi Fishing Port in Japan, located on the Pacific Ocean. We measured cathepsin L activity in the muscle and protein, lipid, and moisture, as well as the trace elemental concentrations. High cathepsin L activity was detected in February and March during the Pacific sardine spawning season. In addition, 4 of 20 fish had extremely high protease activity of more than 30 units/g. Cathepsin L activity in the muscle was negatively correlated with selenium, protein, and lipid concentrations, indicating that sardines in the spring were starving during their spawning migration. Therefore, starved physiological conditions during the spawning season may be responsible for soggy meat.