144 American Fisheries Society 



valuable results to accrue from work on this problem as have 

 accrued from the work already described. 



Fats consist of a combination of glycerin with fatty acids. 

 In the absolutely pure state, which is scarcely attainable in fact, 

 they would be colorless, odorless and tasteless. They usually 

 contain a greater or smaller quantity of coloring matter dis- 

 solved; under certain conditions the combination, glycerin- 

 fatty acid may be broken down, free glycerin and free fatty 

 acid resulting. Free fatty acid has both taste and odor, in 

 fact, our choicest fishes such as salmon, shad and mackerel, 

 owe much of their peculiarly palatable flavor to the small 

 amount of free fatty acid present. But free fatty acid, on 

 exposure to air and light, readily oxidizes, developing during 

 the process a darker color and an unpleasant odor and taste 

 which we call rancidity. Once fats have become rancid they 

 can never be restored to their original sweetness. 



What conditions promote rancidity? First, the* fat must 

 be decomposed or "split" into glycerin and free fatty acid. 

 Next it must oxidize. Just as fish contain autolytic enzymes 

 that decompose protein, so they also contain fat-splitting 

 enzymes. These enzymes require moisture and warmth for 

 their activities. Fat that has been removed from the tissue 

 that produced it may be kept, under proper conditions, for 

 a long time, because only a small amount of fat-splitting 

 enzyme goes with the oil, but when the fat is not removed 

 from the original source, all the enzyme is present and avail- 

 able to produce decomposition. So in salt fish the fat is in the 

 presence of moisture and an abundance of enzyme, and 

 the necessary warmth is usually present also, ideal conditions 

 for decomposition. The fat having been split to fatty acid, 

 there are two factors, so far as known, namely, air and light, 

 which promote oxidation. 



Some little study has been devoted to the effect of salts, 

 such as sodium chloride and calcium chloride on the splitting 

 of fats, but not enough is known about the effect of these 



