92 BULLETIlSr 433, U. S. DEPARTMENT OF AGEICULTI7RE. 



The conduct of this constituent in these experiments was entirely 

 in harmony with the fact that the amino nitrogen, for the most 

 part, represents the accumulation of amino acids, the end products 

 of the autolysis of muscle proteins, and that, within certain limits, 

 the extent of the autolysis increases as its duration and the tem- 

 perature at which it occurs are increased. Although the enzym 

 erepsin is probably most directly concerned in the splitting off of 

 amino acids, yet undoubtedly all classes of proteolytic enzyms pres- 

 ent in muscular tissue participate either directly or indirectly in 

 bringing about the increase in amino nitrogen, so that the increase in 

 this constitutent is theoretically the best index of the extent of 

 proteolysis in muscular tissue. 



In each of the cold-stored quarters of beef the relative increase 

 in amino nitrogen was large, varying from an average of 16.57 to 

 103.22 per cent of the amount present in the fresh material. Like- 

 wise, the actual amounts present, though not really large, formed a 

 considerable proportion of the total nitrogen, varying from less than 

 3 per cent to more than 7 per cent of the total nitrogen, according 

 to the duration and temperature of storage. As the error involved 

 in the determination of these amounts of amino nitrogen in meats is 

 relatively small, the increase in this constituent undoubtedly affords 

 not only the best theoretical, but also the best practical, measure of 

 the extent of autolysis in cold-stored meats. 



Am/moniacal nitrogen. — In general the behavior of ammoniacal 

 nitrogen in this series of experiments was much the same as that of 

 amino nitrogen, although the increases that occurred in ammoniacal 

 nitrogen did not correspond as closely to the time and temperature 

 of storage as did those in amino nitrogen, but involved an additional 

 factor. It may be recalled that in the autolysis experiment the for- 

 mation of ammoniacal nitrogen during the incubation of the beef 

 took place less rapidly as this product accumulated in the material, 

 even though the retarding agency, in all probability, was not the 

 ammonia itself. Similar relations are to be observed in some cases 

 in the cold-storage experiments. 



The way in which ammoniacal nitrogen increases with the time of 

 storage when the temperature of storage remains constant may be 

 seen by comparing the results of Experiments Nos. 1 and 2 on the 

 one hand, and Experiments Nos. 3, 4, and 7 on the other hand. The 

 retarding effect of a lower temperature may be seen by comparing 

 the results of Experiment No. 6, with its 54:-day storage period, with 

 those obtained during shorter periods of storage at higher tempera- 

 tures. The slower rate of ammonia production that is observed when 

 the amount of preformed ammonia is relatively large, can be seen 

 by comparing the ammonia increases of Experiment No. 3 with those 

 of Experiment No. 2, and the increases in the loins of Experiments 

 Nos. 4 and 5. 



