80 BULLETIN 908, U. S. DEPARTMENT OF AGRICULTURE. 



water present in the fish and to the number of times the packed goods 

 are frozen. Mustard sardines, however, are very seriously damaged 

 by freezing and thawing, even once, particularly if improperly dried 

 before packing. The texture of the flesh is destroyed, the appear- 

 ance injured, and the taste lost. 



The desirability of storing sardines at a low, even temperature was 

 demonstrated by these experiments. 



Detinning of Sardine Cans. 



effect of sulphur in skin of fish. 



More or less blackening or detinning of the inner surface of the 

 unlacquered sardine cans always occurs on standing. It was sug- 

 gested by a former packer that this might be due to the action of 

 some compound in the skin of the fish, as from his experience skinned 

 fish when packed did not cause detinning. Sulphur was first con- 

 sidered as a possible cause of the detinning. A difference in the quan- 

 tity of sulphur in the skin of the fish and hi the flesh, provided the 

 skinned fish did not attack the tin, would indicate that sulphur was 

 an important factor in this phenomenon. 



A small pack was made of skinned and unskmned fish from the 

 same source which had been the same length of time in pickle. 

 Part of the fish were skinned and then steamed, dried, and packed. 

 The other portion was dried and packed without removing the skin. 

 Both lots were packed in oil at the rate of less than § gallon per case, 

 and were sterilized for If hours in a boiling water bath. In all re- 

 spects, except for the skinning of part of the fish, the packs repre- 

 sented actual commercial conditions. Representative samples of the 

 skin and flesh of the fish composing this pack were analyzed, with 

 the results shown in Table 34. 



Table 34. — Composition of shin and flesh of sardines. 



Determination. Skin. 



Water 



Fat 



Total nitrogen (N) 



Protein (N X6.25) 



Salt(NaCl) 



Total sulphur (S) 



Total sulphur (water and fat free basis) 



Total sulphur (water, fat, and salt free basis). 



Flesh. 



er cent. 



Per cent. 



63.60 



70.76 



14.62 



3.56 



2.85 



3.90 



17.81 



24.38 



4.05 



1.79 



0.207 



0.260 



0.95 



1.01 



1.17 



1.09 



The amount of sulphur in the skin was practically the same as that 

 in the flesh of these fish. A marked difference in the extent of de- 

 tinning between cans packed with the skinned and those packed with 

 the unskinned fish would not, then, be due to the quantity of sulphur 

 present, although it might be due to its form of combination. No 

 work, however, was done to determine the form in which sulphur 



