The Effect of Premortem Stress, Holding Temperatures, and Freezing on the Biochemistry and Quality of Skipjack Tuna

Book excerpt: This experiment was designed to determine if there were differences (biochemical and/or organoleptic) before and after canning rested and stressed skipjack tuna. The live fish were captured off Oahu and were placed in shoreside tanks in Honolulu, Hawaii. After having been under observation for 24 hr, the fish were sacrificed in a rested or stressed condition. Stress was induced by forcing fish to swim around a tank until they showed signs of exhaustion. The rested fish were kept in a separate tank and were agitated as little as possible before being sacrificed. Some of the sacrificed tuna were canned immediately to serve as controls. Others were held in 32°, 60°, and 78° F seawater (SW) for 6 hr, and some were held in 78° F SW for 9 hr before canning. An equal number of fish from all treatments were brine frozen (for 20 hr), then thawed and canned. Sample wedges were taken before canning for measurements of glycolytic and purine degradation products. These measurements together with organoleptic evaluation were also determined on the canned product. There were no commercially discernible differences between rested and stressed skipjack subjected to various time-temperature treatments. The relation of the measured biochemical parameters to the treatment of the fish and the subsequent relation to the quality of the canned product were studied. There were not sufficiently defined relations on which to base quality predictions.