staff was assembled and the laboratory com- 

 menced operations early in 1966. (I was the 

 research chemist in charge and later the Acting 

 Laboratory Director.) This introduction gives 

 an account of what has been accomplished pri- 

 or to the current studies; the latter covers some 

 aspects of premortem stress and postmortem 

 changes in skipjack tuna and the effects of 

 these changes on the quality of the canned 

 product. 



The General Problem* 



The tuna industry has experienced substan- 

 tial losses of raw fish for many years. In 1966, 

 the losses from the U.S. fleet rejected at the 

 cannery for all causes was 1.98% of the land- 

 ings (Alverson, 1967). This was lower for 

 the temperate tunas, being 0.7% for bluefin 

 and 0.4% for albacore. It was higher for the 

 tropical tunas which are carried for longer 

 times from distant waters, being 1.8% for yel- 

 lowfin and 3.8% for skipjack. Prorating these 

 figures for the same year, the total loss to the 

 U.S. fleet was estimated to be over $1 million 

 based on average prices during the period. This, 

 is the only year for which reliable loss figures 

 have been computed; it is known that the losses 

 vary considerably from year to year. The pri- 

 mary cause of losses is believed to be inade- 

 quate refrigeration on the boat, but other ef- 

 fects are caused by the length of time between 

 catching and canning, which depends on the 

 rate of catch delays at canneries, or auctions, 

 or sometimes tie-ups due to price disagree- 

 ments, etc. Reduction in losses during recent 

 years has been achieved by some canners work- 

 ing with individual boats to identify the causes 

 and to eliminate them. 



In addition to direct losses, the tuna pack 

 shows a considerable variation in quality. 

 There is little doubt that, while some of 

 this may be due to natural factors such as 

 the dark color typical of very large fish, there 

 is a considerable lowering of quality in a num- 

 ber of instances through inadequate refriger- 

 ation prior to arrival at the cannery (Finch, 

 1967a) . In order to reduce losses and improve 

 quality, it is important to identify which qual- 

 ity changes result from natural causes and 

 which can be attributed to unsatisfactory han- 

 dling. Methodology had to be established for 



the measurement of quality in tuna and the ef- 

 fects of refrigeration and some aspects of the 

 chemistry of tuna in relation to quality of the 

 canned product had to be examined. 



Quality in Tuna 



Since "quality" means many things to many 

 people, it was important to define this term at 

 the outset. The laboratory's tuna research pro- 

 gram concentrated its attention on the quality 

 of tuna as it appears in the can. It is canned 

 tuna which is offered for sale and which com- 

 petes on the shelf and in the kitchen for the 

 consumer's dollar. So it is the quality of 

 canned tuna, rather than that of the raw fish, 

 which must form the basis for study. The 

 apparent quality of the raw tuna as judged by 

 appearance and odor is important, but it does 

 not guarantee a good canned product. It is 

 possible to have raw tuna of apparently high 

 quality which shows only average quality when 

 canned. It is also possible to find raw tuna 

 which appears to be of poor quality to sensory 

 judgment that makes an excellent canned pro- 

 duct (Crawford and Finch, 1968). 



So the questions are: First, what is quality? 

 Second, how can it be measured? By quality 

 the canner means those attributes or properties 

 of canned tuna such as color and flavor which 

 a consumer likes and which persuade her to 

 continue to buy the product. In the absence 

 of any comprehensive survey, it was deduced 

 which of these attributes are important and 

 what are their relative importance. It is known 

 that preferences are different in different 

 countries — probably based on traditional ac- 

 ceptance of local species. For instance, large 

 bluefin, which may be regarded as too dark in 

 color by the U.S. consumer, is acceptable in the 

 Mediterranean, where it has been commonly 

 caught for years. It is known that consistency 

 in quality is important. A mixture of good 

 and indifferent quality tuna in a can or even 

 in different cans of the same lot produces a 

 critical reaction when examined concurrently 

 (Loewe, 1967). 



There had been two main sources of infor- 

 mation as to the consumers' likes and dislikes. 

 One was the accumulated experience of can- 

 ners and their distributors who have sold more 

 than 210 million cases in the last 20 years; 



