Effects of feeding olive leaf powder on the chewiness of yellowtail meat

Yellowtail Seriola quinqueradiata raised on a diet supplemented with 2% olive leaf powder (OLP) was subjected to an analysis of the breaking properties of ordinary muscle. The force-strain curve showed that the slope of the OLP-diet fish curve was higher than that of control-diet fish that were raised on a diet without OLP. There was no significant difference in breaking force value, while the breaking strain value of OLP-diet fish muscle was 24% lower than that of the muscle of control-diet fish. Chemical analysis showed that collagen content was 22% higher in OLP-diet fish than in control-diet fish. These results suggest that the difference in collagen content is the cause of the difference in textural property between OLP-diet fish and control-diet fish. The breaking force of the muscles refrigerated for 3 days was 40% higher in OLP-diet fish than in control-diet fish, suggesting that muscle softening of OLP-diet fish was slower than that of control-diet fish. Electron microscopic observation of the muscles refrigerated for 3 days showed that OLP-diet fish had a more robust endomysium structure than control-diet fish. The present study suggests that the ordinary muscle of OLP-diet fish is high quality in terms of textural property.