102 DESCRIPTION OF IMPORTANT FISHERIES AND THEIR PRODUCTS 



be lost. Consequently, the fish may lie on deck for some hours before it 

 is put down even into cool water. When a tuna seiner makes a big set, 

 many fish die in the net and may start to spoil in the warm water even 

 before they are landed. Often a large tonnage of fish may be brought 

 aboard in a short space of time, throwing a heavy load on the refrigera- 

 tion system so that the fish may be cooled more slowly than is desirable. 

 When bacterial spoilage occurs, it follows a similar pattern to that in 

 other fish and shows up as the raw fish are first examined on the butcher- 

 ing table. ''Sour," ''stinking," and badly-broken fish are rejected at this 

 point, and being already included in the landed weight, they are 

 reweighed and charged back against the boat. 



Lengthy on-deck time also leads to "honeycomb" formation which is 

 generally believed due to enzyme action. This condition only becomes 

 apparent when the cooked fish is cleaned and consists, as its name 

 implies, of areas of pitted, spongy-looking muscle tissue, often localized 

 towards the head. Otsu^^, in a series of experiments with Hawaiian skip- 

 jack, found the extent of honeycombing to increase with the on-deck 

 time and with higher fish temperatures. 



Honeycombed tissue has not been shown to be toxic as such, but is 

 believed at times to be associated with the formation of histamine which 

 has been shown by many workers to occur under conditions of advanced 

 spoilage 1*^. Honeycombed fish is rejected at the cleaning stage, and there 

 is no record of significant amounts of histamine occurring in tuna canned 

 commercially in the United States. 



Another undesirable characteristic occurring in some individual tuna, 

 which only becomes evident at the cleaning stage, is the so-called "green" 

 or "greening." This appears as a green to green-tan tint in the cooked 

 loins. It is often accompanied by an unpleasant urine-like odor, especially 

 if the color is marked, and appears to be more prevalent in large fish. 

 There is no evidence that green tuna muscle is toxic, the objections 

 being primarily aesthetic. Brown et al.,^ conclude that the color is mainly 

 a hemichrome, probably resulting from oxidation of the natural hemo- 

 chrome which forms during cooking from myoglobin, the normal muscle 

 pigment. They were unable to connect its occurrence with any known 

 circumstance subsequent to capture. Various tests have been proposed 

 to detect this condition in the raw fish. Some of these have been critically 

 examined by Dollar et al.^ They found that certain factors, such as color 

 of kidney suspension, total heme pigments, oxidation state of the iron, 

 peroxide in fat, tended to vary with "greenness," but that the ranges 

 from fish to fish were so great that no one of these or other measure- 

 ments examined could be used as the basis of a practical test routine. 



Struvite (magnesium ammonium phosphate hexahydrate) forms in 



