Table 3. --Fat and peroxide values of raw tuna flesh 



offcolor flesh, which is in agreement with the 

 postulated oxidation of fats along with the oxi- 

 dation causing greening. The increased perox- 

 ide is nnost pronounced for abnormally pink or 

 orange samples, and less so for green. 



The investigation of the fat content and 

 the peroxide values, related as they seem to be 

 to the oxidation of heme compounds, is particu- 

 larly pertinent since it is known that fish derive 

 their fat mainly, if not entirely, from dietary 

 fat. The fat is deposited in the tissues more or 

 less unchanged (Shorland 1956). Therefore it is 

 conceivable that the differences among fish, 

 which result in greenness being exhibited by 

 certain specimens, are related to differences 

 in dietary fat intake. The presence of fats that 

 are susceptible to oxidation (i.e., linoleic and 

 linolenic acid fats) would render heme pigments 

 subject to easy oxidation. 



FURTHER INVESTIGATIONS ON LEACHING 



It has been noted in previous reports 

 that on precooking, a solution was drained from 

 the fish flesh which was found to exhibit a degree 

 of pigmentation. We have referred to this proc- 

 ess as "leaching" and to the product as the 

 "leachate. " 



Solutions of all leachate pigments gave 

 noncharacterizing absorption curves when 



measured in transmission that are identical 

 with curve (b), figure 10. In addition, the resi- 

 dues left on boiling aqueous extracts of raw flesh 

 have the same color and give the same type of 

 absorption curve. As has been indicated pre- 

 viously, extracts of the hemin of precooked 

 meat with acetone or methanol- IN hydrochloric 

 acid (Briickmann and Zondek 1940), gave the 

 same types of absorption curves on measure- 

 ment in transmission as those resulting from 

 similar treatment of raw meat. In view of this, 

 one would expect to find that heme was the pig- 

 mented substance cleaved fronnthe myoglobin in 

 the tuna fie ah and leached out during precooking. 

 Repeated efforts, however, to produce the 

 rhomb- shaped crystals of "alpha-hemin" 

 (chlorohemin, hemin), which are so characteris- 

 tic of this compound when derived from mam- 

 malian blood, were not successful (Teichmann 

 test). The identification of this substance is 

 particularly pertinent because of the possible 

 relationship between the phenomenon of leaching 

 and the pronounced solubility of metmyoglobin 

 reported above. 



FISH EXHAUSTION AND 

 METMYOGL-OBIN CONTENT 



As a result of the accelerated conversion 

 of oxymyoglobin to metmyoglobin noted in the 

 absence of oxygen (nitrogen and evacuation), it 

 was hypothesized that a condition of anoxia, or 



10 



