366 MARINE PRODUCTS OF COMMERCE 



dealers in poor condition. The merchant must either sell the fish immediately or 

 keep them in refrigerators until his market demands them. Even when the retail 

 dealer disposes of his salted fish quickly, a large percentage of them must be 

 sold at a low price because of rust or taint. 



No figures are available which show what proportion of the salted fish are 

 culled out before they reach the consumer. A representative of one of the largest 

 salt-fish packing establishments in this country stated that during repacking the 

 loss of mackerel due to rusting alone varied from 10 to 25 per cent, depending 

 upon the season. Another fish-packing house which does a mail-order business 

 placed their loss due to rusting at 25 per cent of the mackerel business. Un- 

 doubtedly, the amount of salt mackerel culled out by the wholesale houses and 

 retail stores because of spoilage is very large indeed. 



Herring and alewives or river herring are even more difficult to keep than 

 mackerel. Thousands of barrels of herring are dumped overboard annually because 

 of souring and rusting. Occasionally, the entire season's output of some packing 

 houses is discarded because of improper storage. 



Cod, haddock, and other ground fish contain little fat and consequently do not 

 rust; however, even their small fat content is sufficient to cause them to turn 

 yellow with age and become rancid and difficult to rehydrate. When stored in 

 boxes these fish often redden and become unfit for consumption because of bac- 

 terial growth. 



The agencies causing spoilage of salted fish are those which cause spoilage of 

 fresh fish (viz., enzymes, bacteria, oxidation, and hydrolysis). The conditions un- 

 der which autolysis and bacterial growth occur have already been described. 

 Oxidation and hydrolysis of the fat or oil of fish occur in fresh fish, but the results 

 of their action are less easily noticed because of the slow speed at which they 

 take place. The rate at which the various fish oils take up oxygen varies consider- 

 ably. Tuna oil is one of the most active oils in this regard. Oxidation and hydrolysis 

 of fat occur most rapidly in sunlight and in the presence of a free supply of air 

 at high temperatures. These actions, therefore, take place chiefly on the exposed 

 surface of the fish. The presence of sodium chloride hastens the rate of oxidation 

 of the oils. 



Because of the danger of oxidation and hydrolysis of fat and consequent ran- 

 cidity fatty fish must be stored in a cool place, preferably at about 30° F 

 (— 1.1° C) and in the absence of air if possible. On this account mackerel, herring, 

 and alewives are usually kept under strong brines in cool storages. 



While salting reduces the rate of autolysis to a slight fraction of its original 

 speed, it does not completely stop enzyme action. The autolytic decomposition of 

 salted flesh of fish is so slow under proper storage conditions that the fish will re- 

 main in good condition for at least 2 years. Blood and viscera rapidly decompose 

 in salted fish if the temperature is permitted to rise above 68° F (20° C). There- 

 fore, great care must be taken to keep cool Scotch cured herring and other round 

 or partially cleaned salted fish. 



The storage of cod, haddock, and other ground fish is a very serious problem 

 because of reddening and the development of rancidity of the surface fat. Cool 

 storage retards both of these actions, but in shipping small lots of fish it is diffi- 

 cult to keep them cool. The danger of reddening is largely obviated by "hard- 

 drying." As this grade of cod is not liked by the domestic trade, not many fish 



