KFFKCT f)V HIGH HKATIXG OX ]'ROi'i;RTn;S Dl- .AHLK 41 



in rrost of our up-to-date creameries to-da\" is to pasteurize 

 tlie creair, , under tlie vat or liolding ^_\"stem, to 170^ F. or abeiAT, 

 or, under tlie flasii s}'stem, to at least oSo' F. 



TIto reasein wh}- this cooked flaA'or i^ fnunrl in milk when 

 heated is not well understood. It is suj)p<i~ed to bo due to 

 the effect which heat has upon the nitro_L(eneous constituents 

 and the sugar. 



5. Precipitates Albuminoid and Ash Constituents. — When 

 milk is heated, there is a tenrlenc}- for the soluble salts and a 

 portion of the albuminoids to be thnjwn down, or changed into 

 an insoluble form. 



The higher the milk is heated, the gTeater is this tendenc}-. 

 If a sample of milk in a flask is subjected to intense heat, and 

 then allowed to stand, a fine white sediment Avill be deposited on 

 the bottom. This is Ijelieved to consist of minerals precipitated 

 from the milk. 



When milk has been heated to about 170' F., and cooled, 

 rennet is unable to precipitate the curd in a n(jrmal wa}-. The 

 curd resulting from adding rennet to pasteurized milk is flocculent 

 in nature. It does not assume that smooth and CA'cn texture 

 that curd from raw milk has when precipjitated witli rennet. 

 The behavior of pasteurized milk towards rennet can be ren- 

 dered normal b\- adding a small quantity of calcium chloride 

 (CaCl). Whetlier this would affect the c|ualit\' of cheese mate- 

 rially has not }'et been determined definiteh'. According to G. 

 Fascetti,' if pasteurized milk is used for cheese-making, the 

 cheese ripens more skjwh- than when made from raw milk. The 

 same in\'estigator also claims that a larger quantity of cheese 

 is obtained per 100 parts of milk when pasteurized milk is 

 used. 



6. Destroys Properties of Enzymes.— As was mentioned in 

 the chapter on the composition of milk, there is a substance nor- 

 mal to milk named galactase. 'Fhis is an enzyme. By heating 

 milk to about 175^ F. the properties of the enzyme are destroyed. 

 Owing to this it is easy to determine whether a certain sample of 

 milk has been pasteurized or not. Galactase is present in milk in 



' Exp. Sta. Record, A'ol. 15, X"o 10, 1Q04. 



