146 Influence of Low Temperatur es upon Enzymes [March, 



with 3, 6 and 9 ounces of rennet per 1000 pounds of milk, and were 

 permitted to ripen at temp. of 15°, 33°, 40°, 50° and 60° F. for 

 periods of 6, 10, 12, and 14^ months. Total soluble nitrogen in- 

 creased progressively in the cheese held at each of these temp., the 

 increase being more marked at any given time in a cheese kept at a 

 higher temp. than in one held at a lower temp. A marked increase 

 in soluble protein was noted even in cheese stored at a temp. below 

 freezing (15° F.). At a given temp. and in given time, a greater 

 rise in the total soluble nitrogen occurred v^hen larger quantities of 

 rennet had been used in the process of manufacture. This influ- 

 ence of the rennet was due to the pepsin content of the latter, and 

 was observed in the samples held at 15° and 33° F. as well as in 

 those stored at higher temp, 



The action of the galactase at all the temps., including 15° and 

 33° F. was absolutely demonstrated by progressive increase in 

 amino-acid nitrogen, This increase was independent of the quan- 

 tity of rennet used in the process of manufacture, and became more 

 marked as the cheese were carried at a higher temp. 



Ravenel, Hastings and Hammer (23) held a sample of "barn 

 milk," the best milk obtainable, and one of a fair grade of dairy 

 milk at — 9° C. for 203 days. At the end of that period the water 

 soluble nitrogen, expressed as percent of the total nitrogen of each 

 sample, was: barn milk, 17.97 percent; dairy milk, 22.38 percent; 

 while the average for fresh milk is 10 percent, The higher per- 

 centage in the milks subjected to prolonged holding at this low 

 temp. is Said to be due, probably, to the action of galactase, 



Pennington, Hepburn, St. John, Witmer, Stafford and Burrell 

 (10) held a milk, rendered bacteriologically sterile by formalde- 

 hyde (o.i percent), at 0° C. for 35 days, and studied the partition 

 of the nitrogen at intervals of 7 days, The nitrogen present as 

 lactalbumin and syntonin, and as peptone, tended to decrease but 

 the caseose nitrogen and the amino-acid nitrogen increased, the 

 casein nitrogen remaining practically constant, Proteolysis was 

 due mainly, if not entirely, to the action of galactase, 



Urease, Van Slyke (27) demonstrated that the urease of the 

 soy bean hydrolyzes urea at temperatures as low as 0° C, The 

 temperature coefficient of the reaction was found to be 2.80 for 



