CHAPTER XXIV. 

 CHEESE. 



I. Rennet. For the coagulation of the caseinogen of 

 milk in the manufacture of cheese the salted and dried 

 inner membrane of the so-called " fourth " or true digestive 

 stomach of very young calves is frequently employed 

 under the name of rennet. 



Such material contains a coagulase or coagulating 

 enzyme, termed rennin or ckymosin, and also a certain 

 amount of pepsin, the former precipitating paracasein 

 in milk, while the latter in acid solutions breaks down the 

 curd into simpler proteins. 



Rennin is found in the stomachs of most young 

 mammals, and commercial extracts are prepared from 

 those of dogs and pigs, as well as calves. 



A similar coagulase is present in certain seeds, in the 

 leaves and stems of Bedstraw (Galium verum, L.),and in 

 the flowers of the Artichoke (Cynara Scolymus, L.). 

 Fitz and Hueppe showed that it is possessed by Bacillus 

 butyricus ; Warrington found it in Bs. fluorescens lique- 

 faciens, and Vignol proved its existence in Bs. vulgatus. 

 Certain varieties of Proteus, Bs. prodigiosus, and some of 

 the lactic acid organisms have the power of coagulating 

 caseinogen and subsequently dissolving it by means of 

 a pepsin which they secrete, the former action being 

 most in evidence in cultures kept at 20 to 25 C, while 

 their peptonizing property is most active at 37 C. 



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