NUTRITIVE VALUE OF FISH AND SHELLFISH 509 



individual items in this table were assembled from a great variety 

 of sources, it will not be possible to give credit to the individual 

 investigators. 



In the case of salmon — ^which is the most important sea food 

 canned, amounting in value (to the packer) to some $50,000,000 a 

 year — -there are few changes in the manufacturing process except 

 that due to the addition of salt. On the other hand, in the case of 

 sardines, tuna, and products of that sort, the fish are usually pre- 

 cooked, fried, steamed, or dried before being packed, and then olive 

 oil, cottonseed oil, or tomato sauce may be added just before the can 

 is sealed. In the case of canned salmon the food value is quite high 

 for most species because of their fat content. All species of canned 

 fish have a considerable percentage of protein, and that, of com'se, 

 is the main constituent that makes them valuable. Wliere additional 

 oil Ls added, as in the case of sardines and tuna, the food value is 

 naturally very high, in terms of calories, because of the added oil. 

 As salt is always used in canning, it will appear in analyses under 

 the heading of "ash," except in those cases where particular pains 

 were taken to determine the salt separately from the rest of the ash 

 constituents. 



In regard to the percentage of solids or moisture in canned fish 

 it should be noted that those products that are put into the can 

 in the raw state, like canned salmon, undergo shrinkage and elimi- 

 nation of water during the high temperatures of sterilization, so that 

 the composition of canned salmon is more like that of cooked fresh 

 fish unless all the liquids in the can, which were cooked out, are 

 mixed with the fish when prepared for the table. In the analytical 

 work reported above, Shostrom, Clough, and Clark (1924) analyzed 

 the edible contents of the can, including the liquid, so the food values 

 of the drained salmon as usually eaten would be considerably higher 

 than those given in the table. 



The most complete data we have on any canned fishery product 

 is that of Shostrom, Clough, and Clark (1924) on the Pacific coast 

 salmon, given in the above table. In connection with tliis work 

 some 786 separate cans of salmon were analyzed. Many of these 

 cans consisted of identical cuts of individual salmon so as to elimi- 

 nate variation in composition due to different parts of the same fish 

 being canned. The average number of calories per pound for all 

 species and grades of salmon from aU districts was 738 in the special 

 packs just described and 768 for the commercial packs that were 

 analyzed and in which no special pains were taken to secure uni- 

 formity of the section of the fish analyzed. The steelhead trout, 

 while not a salmon, is a fish of considerable economic importance on 

 the Pacific coast, and its food value when canned was found to aver- 

 age about 972 calories per pound. A few samples of Atlantic coast 

 salmon were analyzed and were found to have an average fuel value 

 of 920 calories per pound. This agrees very closely with the fuel 

 value of the Pacific coast chinook salmon, which is 928 calories, 

 althou'jh the Atlantic and Pacific species are entirely distinct. 



Of all the ways of preserving fish there is none more important than 

 canning. The great development of the salmon-canning industry on 

 the Pacific coast shows that canned fish is a staple article in the 

 United States and certain other countries like Great Britahi, Canada, 



