The variation of the oil contait of the tuna vdth differing degrees 

 of precooking before addition of vegetable oil and before retorting 

 (middle column, table 75) is probably meaningless because each of the 

 three precook groups consisted of different individual fish of different 

 initial oil content. The data in the last column of table 75s shovdng 

 the oil content after retorting with added vegetable oil, are of more 

 significance because in this case there was an excess of free oil 

 present which tended to bring the oil content of the fish to an equili- 

 brium state regardless of the initial oil content. The canned fish which 

 received no precook had an oil content of 15 percent as compared to 19.5 

 percent for fish receiving the full precook. Thus it appears that ab- 

 sorption of added vegetable oil takes place to a greater extent, the longer 

 the fish is precooked before addition of oil. 



The moisture contait of tuna, both before and after final retorting, 

 showed a decrease as the length of precooking time increased (table 76). 

 This moisture content decrease amounted to about 6 percent regardless of 

 vAiether it was measured before or after final retorting. 



The degree of precook had a very pronounced effect on the amount of 

 aqueous fluid formed during retorting (table 77). Thus, in fish which 

 received the normal precooking time, the canned product contained only 

 3 2/3 mlo of aqueous fluid as compared to 22 ml. where uncooked fish 

 was retorted or 10^ ml. vAiere the fish received only one-half the normal 

 precook time. The percentage of dissolved solids in the aqueous phase 

 (table 77) decreased with decreasing precook time, but the total quantity 

 of such solids increased as the precook time decreased. The decrease in 

 the amount of free oil in samples receiving a longer precook time is 

 probably due, at least in part, to a greater absorption of oil by the 

 flesh of such fish (see table 75). 



The appearance and texture of the three packs differed considerably. 

 The most striking difference was the occurrence of much white curd on 

 the surface of the fish which had not been precooked. None of the samples 

 receiving one-half or full normal precooking time had any trace of curd. 

 The samples from fish receiving no precook were also of a very different 

 texture which kept the fish from flaking at all readily. A sample in 

 the can appeared as if it were one solid chunk of fish (welded together 

 at the surface by the curd), and it could be broken apart only with con- 

 siderable difficulty. Even aside from the presence of the curd, this 

 texture difference was one vdiich would sharply differentiate the fish from 

 what one normally associates with tuna. This altered texture apparently 

 acted as the main barrier to penetration of the vegetable oil into the flesh. 



319 



