FISHERY INDUSTRIES OF THE UNITED STATES, 1934 85 



DETERMINATIONS FOR THE RELATIVE FRESHNESS OF FISH 



For many years, there has been a need for a standard method for 

 determining the rehxtivo freshness of fish or conversely for determin- 

 ing: the stao;es of decomposition in fresh fish. A method has been 

 desired by such oovcrnmental authorities as pubhc health inspectors, 

 pure food inspectors, frrading; inspectors, and the like, as well as 

 many members of the fishery industry. The usual practice has been 

 to determine freshness by an organoleptic test of the product, some- 

 times accompanied by bacteriological analysis. The former tests 

 oftentimes have resulted in as many verdicts as to the quality as 

 there are judges and the latter requires considerable time as it is 

 necessary to make a culture from the bacteria obtained from the fish. 

 It, therefore, appeared that a need existed for a test that could be 

 used with uniform results by the layman and one which could be per- 

 formed Ax-ith a minimum of delay. In order to aid in this direction, 

 a series of technical studies have been conducted by members of the 

 technological stall' which resulted in the development of an electro- 

 metric method for the detection of the relative freshness of haddock. 

 This method, which was described in brief in last year's report of 

 this division, consists in measuring electrometrically the quantity of ai 

 standard acid absorbed by the protein in a given quantity of the 

 flesh of the fish and checking results with a previously developed 

 chart of standardized values. 



As the property for absorbing acid by the protein varies slightly 

 in dift'erent species, it would be necessary to develop a technique 

 for the various species. In view of this, studies were conducted, 

 during the past year, for determining the relative freshness of cod, 

 pollock, and mackerel. While these have not progressed to the point 

 where a chart can be prepared against which to check the tests, they 

 do indicate that this type of test is applicable to all species of nonoily 

 fish, such as cod and pollock, but that possibly a different technique 

 vnll need to be developed for such oily fish as mackerel. It appears 

 that the technique for the oily fish will need to include a test for 

 determining the relative rancidity of the oil in such fish. 



CANNING AQUATIC FOODS 



At the present time, only about 20 of the 160 varieties or species 

 of fish and shellfish taken in our waters are canned (hermetically 

 sealed in tin cans or glass jars) on a commercial scale. This has been 

 due largely to the economic factors of supply and price. However, 

 during late years, there has been a demand on the part of housewives, 

 home economic and relief workers, and others for information on 

 methods for canning aquatic foods. With this in mind, a series of 

 technological and bacteriological investigations have been undertaken 

 during the past several years, to develop methods for canning these 

 products which could be safely and easily used in the home as well as. 

 by home economic and relief workers in community kitchens or in 

 commercial establishments. This work has been conducted toward 

 three principal goals. First, toward the selection of species taken in 

 the fishery harvest which would be suitable for canning from the 

 standpoint of availability and adaptability. Second, toward the 

 determination of proper cooking temperatures to create sterility. 



