BUTTER DEFECTS 509 



high a temperature, heating too slowly, holding at pasteurizing 

 temperature too long, or not cooling rapidly enough. 



The acid in sour cream changes the casein to casein lactate, 

 and precipitates it into very fine flakes, or particles of curd. Van 

 Slyke and Hart 1 found that the casein is changed to casein lac- 

 tate, when the amount of lactic acid in cream exceeds .5 per cent. 

 In sweet cream the casein is largely in the form of calcium casein 

 and some free casein. 



When this sour cream is heated for a prolonged period of 

 time, as is often the case in the holding process of pasteurization, 

 these particles of curd contract, expel much of their moisture, 

 become firm and dry and give both the cream and the resulting 

 butter a mealy texture. The mealiness is noticeable in the 

 hot cream, and in the cream after cooling, quite as much as in 

 the butter. Mealy cream always makes a mealy butter. 



Mealiness of this type does not occur in sweet or slightly 

 sour cream, because in such cream the casein is present in its 

 original and unchanged form. It has not been acted upon by 

 the acid, it has not been precipitated. However, acid alone does 

 not make cream and butter mealy. The particles of curd in the 

 raw sour cream are soft. It is only in the presence of very high 

 heat or upon prolonged exposure to heat, that sour cream be- 

 comes mealy and makes mealy butter. 



Mealiness resulting from the above causes can be avoided 

 by shortening the time required to heat the cream to the pas- 

 teurizing temperature, by not exceeding 145 F. in the holding 

 process, by holding for 30 minutes only and by cooling rapidly. 

 Under proper conditions, such as adequate steam supply, ample 

 size of steam and water pipes leading to the vat pasteurizer and 

 adequate heating surface, the heating to 145 F. can usually be 

 done in about 15 minutes. Experience has shown that, where 

 the temperature can be raised to 145 F. in 15 minutes, there is 

 very little danger of the cream and butter becoming mealy. If 

 the time required to heat to 145 F. exceeds 30 minutes it is 

 more difficult, and under certain conditions impossible, to avoid 

 mealiness. 



Mealy butter is also almost invariably produced from sour 



* Van Slyke & Hart, "The Proteids of Butter in Relation to Mottled Butter/* 

 New York State (Geneva) Agr. Bxpt Station Bull. 263, 1905. 



