94 MILK 



rennet tablet in 150 c.c. of distilled water, and various amounts of 

 acid : 



INFLUENCE OF ACIDS ON RENNET ACTION 



This table shows clearly that with an increasing quantity of 

 acid the time required for coagulation decreases. It also shows 

 that the accelerating effect of different acids is not the same. 

 Acetic acid is at the head of the list, while the following acids 

 exert a smaller accelerating influence in the order given in the 

 table. 



The usual explanation of the accelerating action of acids is given 

 as the formation of the solution of insoluble calcium salts, thus 

 activating the enzym. Even a weak acid like CO 2 favors rennet 

 action. Alkalies and alkaline salts have an inhibitory effect on 

 rennet action. 



3. The Presence of Salts and Other Chemical Compounds. 

 The effect of salts and other chemical compounds on rennet action 

 may be favorable or otherwise. Acid salts are favorable, while 

 alkaline salts retard and ultimately inhibit rennet action. Chlo- 

 rids of alkalies inhibit in quantities of 0.5 per cent, and more. 

 In smaller quantity there is slight acceleration. Sodium chlorid 

 accelerates in quantities up to 0.9 per cent. Sodium chlorid and 

 ammonium sulphate retard rennet action, while citrates and oxa- 

 lates inhibit. The chlorids of calcium, strontium, and barium 

 accelerate rennet action in quantities of one-tenth to one-thou- 

 sandth normal solution. 



The chlorids of zinc and aluminum also accelerate rennet ac- 

 tion, although in smaller amounts than other chlorids. Mag- 

 nesium chlorid accelerates in quantities of one-fiftieth to one- 

 tenth normal solution, but retards below this amount. Salts of 

 barium, calcium, strontium, beryllium, aluminium, and zinc have 

 slightly accelerating action in minute amounts. Salicylic and 

 benzoic acids also accelerate in small amounts (one-fiftieth nor- 

 mal). Alcohol, glycerin, thymol, and formaldehyd retard, while 

 H 2 02 accelerates rennet action. Ultraviolet rays act unfavorably 

 on rennet coagulation. 



The influence of calcium chlorid on rennet action when minute 

 amounts of rennet are used is given by Hammarsten as follows 

 ("Sommerfeld's Handbuch") : 



