The Effects of Premortem Stress, Holding Temperatures, and 



Freezing on the Biochemistry and Quality of 



Skipjack Tuna 



By 



LADELL CRAWFORD, Chemist' 



National Marine Fisheries Service 



Technological Laboratory 

 Terminal Island, California 90731 



ABSTRACT 



This experiment was designed to determine if there were differences (biochem- 

 ical 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 can- 

 ning for measurements of glycolytic and purine degradation products. These measure- 

 ments 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 mea- 

 sured 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. 



INTRODUCTION 



The canned sea food industries have been 

 pioneers in the area of convenience foods. 

 Canned tuna, a quarter billion dollar industry, 

 has been and is the leader in this large and 

 rapidly growing enterprise. This product con- 

 tains 20 to 25% well-balanced protein with 

 generous amounts of essential fatty acids, vi- 

 tamins, and minerals. Canned tuna provides 



' Now Research Chemist, Poultry Laboratory, Agri- 

 cultural Research Service, Western Marketing and 

 Nutrition Research Division, U.S. Department of Agri- 

 culture, Berkeley, CA 94710. 



one of the cheapest sources per pound of qual- 

 ity protein. 



Wider consumption of canned tuna and other 

 fishery products could play an important role 

 in reducing malnutrition found in many low- 

 economic groups in the United States. 



The Terminal Island Technology Laboratory 

 was set up by the Bureau of Commercial Fish- 

 eries (now the National Marine Fisheries Ser- 

 vice) to assist in solving some of the technical 

 quality problems which the tuna industry had 

 experienced for a number of years. The solv- 

 ing of these problems could result in a higher 

 quality pack and increased yields. A small 



