FISHERY INDUSTRIES OF THE UNITED STATES, 1»:}3 9 



cause a broakdown in the protein coniijosinii; the (ish tissue. This 

 method is based on the absoii)tion oi a standard aeid sohition by the 

 ])rotein. It was found that an accurate index of tlie condition of the 

 flesh was indicated by measuring!; ehH-tronietrically the (juantity of 

 acid abso]])ed. Hathk)ci< was the species of fish upon wliich this test 

 was first apphed. After inakint; tests on a series of several hundred 

 samples, it was possible to tabulate the results in such a way that a 

 table for general use was evolved. It was found that it would be 

 necessary to prepare a table of this nature for each species of fish since 

 the property for absorbing acid by the protein varies slightly in dif- 

 ferent species. At present, tables are being prepared for use with cod, 

 pollock, and mackerel. Some tests have also been made on Pacific 

 coast salmon. 



Other problems connected with the freezing and storage of fishery 

 products are being studied. There are a great number of variable 

 factors and combinations which arise in the consideration of problems 

 of this nature. Although the technologists are making an effort to 

 solve each of these problems as they arise, the variable conditions 

 make progress difhcult and slow. 



Our technologists are investigating the technique of freezing several 

 varieties of shellfish, and the effect of storage and fluctuations of 

 temperature in the storage room. With these studies are included 

 such conditions as the effect of freezing and storage upon the keeping 

 quality of the product after it has been defrosted and displayed for 

 sale, and the rate of increase of bacteria during this same period. 

 Oysters and shrimp are given immediate attention since these two 

 species compose the greater portion of shellfish being marketed. 

 The change of weight over short and long periods of time is included 

 in the study of the effect of packing fishery products in ice for ship- 

 ment. The results, which are apparent at the present time, indicate 

 that the weight of some species of fish increases for a short period then 

 gradually decreases until at the end of approximately 10 days a 

 decided loss in weight is noted. It has been observed that dift'erent 

 species of fish show different rates of decrease in weight when packed 

 in ice for shipment. 



The development of lactic acid is the cause of the well-know^n "rigor 

 mortis" which occurs in the flesh of all animals immediately subse- 

 ciuent to death. The effect of the further development of lactic acid 

 in fish muscle is receiving attention. Attempts are being made to 

 correlate the presence of dift'erent quantities of this acid with the 

 different changes which occur when fish are frozen and placed in 

 cold storage rooms. It is believed that the presence of lactic acid 

 in the flesh of fresh fish, which are being frozen for storage, may have a 

 A'ery definite effect upon the keeping quality and flavor of them when 

 they reach the hands of the ultimate consumer. In making studies of 

 this nature, it has been necessary for the technologists to make trips 

 in some of the small boats and bring in live fish, keeping them alive 

 in a t;;nk in the laborntor}^ until they were needed. When the neces- 

 sary prcpnratioi.s had been made, the fish were killed and tests made 

 immediately for lactic acid. This method permits a study of the 

 development of lactic acid in the fish muscle at frequent intervals as 

 it increases to a maximum, then decreases until it disappears. Sam- 

 ples containing a known percentage of lactic acid are frozen and the 

 results of these various concentrations upon the keeping quality 

 observed. 



