146 MILK [vin 



by the fact, that certain bacteria have the power of 

 acting upon the curd and dissolving it ; hence it is 

 advisable to use rennet in such a manner that it will 

 produce its coagulation as quickly as possible. 



Form in which Rennet is used. Formerly a 

 solution of rennet was always used. This was of 

 home manufacture, and was made in small quantities 

 for immediate use. Now, however, rennet is largely 

 manufactured on the commercial scale, either in the 

 form of a solution or in a powder. These solutions 

 generally contain, in addition to the active principle 

 of the rennet, small quantities of pepsin, an unorgan- 

 ised ferment which produces lactic acid, and com- 

 paratively large quantities of slimy matter and other 

 organic matter, the composition of which is unknown. 

 They also contain salt or alcohol, and sometimes 

 other preservatives, such as boracic acid, salicylic 

 acid, benzoic acid, etc. All these substances increase 

 the keeping qualities of the rennet solution, but this 

 is effected at the expense of its strength, since they 

 render a portion of the rennet ferment inactive. 



Extracts of rennet should be clear in appearance, 

 and should not possess a disagreeable smell. Their 

 coagulating properties should not lose, in the course 

 of a year, by more than 25 per cent. Rennet 

 powders are more concentrated than rennet solutions ; 

 they should be almost entirely white, and devoid of 

 smell, and should almost completely dissolve in 



