THE SALTING OF FISH. 31 



The kits of salted fish were immediately placed in a large, con- 

 stant-temperature vat capable of holding seven small kits. The kits 

 were held at a definite constant temperature throughout the salting 

 period. In this case the temperature of lots FA-1, FA-4, FA-5, 

 and FA-6 was held at 79° F. 



These large, constant-temperature vats were steel tanks. They 

 were about half filled with water, which was electrically heated. 

 A framework was built around them, and the space between the 

 framework and the vats was filled with sawdust. They were fitted 

 with wood covers and were also covered with paper and oilcloth. This 

 effectually thermally insulated them. Hasselbring thermoregulators 

 operated a relay system which regulated the operation of the heaters. 

 A water motor drove the stirrers, which efficiently kept the vats at a 

 uniform temperature throughout. In this experiment the tempera- 

 ture did not vary more than 1° F. from the average. 



Analysis of fish. — Samples of the fresh fish were analyzed at the 

 beginning of the experiment. It was found that uniformly cleaned, 

 fresh alewives have practically the same amino-acid content. In the 

 case of the well-cleaned and well-washed alewives this is about 0.02 

 per cent amino-acid nitrogen (fresh basis). This fact might be 

 utilized in judging freshness of fish. 



At the end of the experiment the fish, brine, and salt were weighed 

 and sampled. The samples were analyzed for amino-acid nitrogen, 

 according to the method described. The total weights of amino-acid 

 nitrogen in the brine, residual salt, and fish were calculated. These 

 were added together, and the total weight of amino-acid nitrogen 

 contained in the fresh fish subtracted from their sum. This gave the 

 total weight of amino-acid nitrogen formed. This figure was divided 

 by the original weight of the fish in kilograms. The result is the 

 weight of the amino-acid nitrogen formed per kilogram of fish. 



This work is based on the supposition that the greater the decom- 

 position of protein the greater will be the amount of amino-acid nitro- 

 gen formed, inasmuch as the chief product of autolysis is amino- 

 acid nitrogen. Where decomposition takes place so rapidly that the 

 chief action is bacterial, amino-acid nitrogen is also formed; but in 

 this case it is merely an intermediate product as the end products of 

 bacterial action are ammonia and nitrogen. In such cases am- 

 moniacal nitrogen ought also to be determined. The experimenter 

 was always limited by lack of time and facilities for elaborate 

 chemical work. This is inevitable unless the investigator has the 

 use of a complete chemical laboratory close to a large continuous 

 supply of fresh fish and has the help of a corps of assistants. 



As long as there was but little spoilage of fish in the experiment, 

 the results of the amino-acid determinations from different lots saltect 

 under identical conditions checked excellently. But when the spoil- 

 age was great enough to cause the formation of foul-smelling gases 

 and was quite evidently of a bacterial nature the amounts of amino- 

 acid formed did not show what was anticipated. Surely, in such 

 cases the ammoniacal nitrogen ought to have been determined. 

 The results of the analyses and calculations are given in Table 5. 



