618 MILK 



micrococci begin to peptonize the casein. The pepsin ferment 

 contained in rennet is activated by the acid, and other enzyms — 

 galactase, for example — produce proteolytic decomposition. In 

 hard cheese the casein is decomposed in lesser degree than in soft 

 cheese. The latter ultimately may become semihquid. The de- 

 gree of decomposition is measured chemically by determining the 

 relative quantities of soluble nitrogen, amino-acids, and am- 

 monia. The amount of acid present is an important factor influ- 

 encing protein decomposition in cheese. As soft cheese contains 

 much whey, there is a large quantity of acid in the central portion, 

 and ripening is slower here than at the outside. When the outer 

 portion has become transparent through proteolysis, the inner 

 part is still opaque and white for some time. Decomposition of 

 cheese is carried on by liquefying aerobic micrococci, lactobacilli, 

 and molds. It was thought formerly that anaerobic and aerobic 

 spore-forming bacteria were active, but these have been found to 

 be of little or no consequence. The digestion of protein in cheese 

 frequently leads to the formation of amino-acids. In Emmen- 

 thaler cheese a large number of amino-acids have actually been 

 demonstrated, and the cheese owes its sweetish taste to their 

 presence. 



Dox found the following substances in Camembert cheese: 

 Caseoglutin, protocaseoses, deuterocaseoses, peptones, histidin, 

 arginin, lysin, glutaminic acid, tyrosin, and leucin. He did not 

 find paranuclein, tryptophan, indol, skatol, mercaptan, hydrogen 

 sulphid, and phenols. There is, therefore, no putrefaction in 

 Camembert cheese unless ripening is allowed to go too far. The 

 author concludes that the digestion is an ereptic one, and that the 

 enzjmi isolated from Camembert mold is a vegetable ereptase. 



The fat is but sUghtly broken up in some cheeses, while in 

 others decomposition is pronounced. Volatile acids are formed, 

 and these are responsible for flavor. The decomposition of fat 

 may go so far as to impart a rancid taste and odor to the cheese. 

 Fat decomposition is carried on by aerobic bacteria or molds. It 

 commences, therefore, on the outside. If a mild cheese is desired, 

 cheese is ripened in large bulk, so as to offer a relatively small 

 surface to the air. The rind is sometimes specially protected 

 against the air by a coat of paraffin. In Edam cheese the same 

 object is sought by drying the ripe cheese in the sun, rubbing it 

 with linseed oil, and coloring with Berlin red or annatto. If a 

 strong taste is desired cheese is ripened in small pieces and thus 

 a large surface exposed to the air. Among the products of fat 

 decomposition are: alcohols, esters, acetic, butyric, propionic, 

 caprionic, valeric, formic, and acetic acids. Volatile acids impart 

 the characteristic cheese odor. Currie decided that the peppery 



