14 DAIRYING 



mentations they contain have developed from the bacteria that 

 get into milk, cream, etc., during the usual handling of these, 

 products. Excellent starters are often made from selected whole 

 milk. Several sterilized milk bottles, provided with covers, as 

 previously described, are two-thirds filled with milk from differ- 

 ent cows, or from different herds; each bottle is labeled and 

 placed in the incubator at a temperature of about 80 degrees 

 Fahrenheit until the milk sours. The sour milk in each bottle 

 is then carefully inspected, and those in which the curd is solid 

 with no holes and have a pleasant, but acid, taste*, are the safest 

 ones to use for making a starter. This kind of a starter pos- 

 sesses the advantage of being easily changed in case the butter 

 flavor becomes unsatisfactory. In some places bottles of milk 

 are collected daily for the purpose of selecting a new starter 

 from them whenever wanted. 



540. It is claimed that milk from a fresh cow, or early in 

 the milking period, is much better for starter-making than the 

 milk of a stripper. If the udder of such a cow is carefully 

 washed and dried just before milking, and the first few jets of 

 milk kept separate from the remainder of her milk, which is 

 then milked directly into sterilized bottles, a very satisfactory 

 starter may be built up by setting such bottles of milk in the in- 

 cubator to sour, and then adding this sour milk to a larger quan- 

 tity of pasteurized skim milk. Three to four pounds of sour 

 milk, added to 100 pounds of pasteurized skim milk, will gener- 

 ally become sour enough to add to cream, if kept at about 65 

 degrees Fahrenheit for twenty-four hours. 



541. Buttermilk or sour cream are not usually recommended 

 as starters for ripening cream, because a churning of cream may 



* Milk is sterilized when all bacteria and spores in it are killed. This 

 Is a very difficult thing to do, and is only accomplished in laboratories 

 where facilities are provided for repeated boiling's for periods of at least 

 one-half hour long. Between boilings at least twenty minutes should 

 elapse and the milk allowed to cool to about 80 degrees Fahrenheit in order 

 to develop those spores which have lived through the first boiling. When 

 these have matured they will be killed by the subsequent boiling. From 

 three to five days are generally needed to sterilize milk completely. 



It is not possible for butter makers with the ordinary dairy or cream- 

 ery appliances to sterilize milk. They may pasteurize it, however; and 

 this is the name that should properly be given to the ordinary heating 

 f milk for starter making. The temperatures used in pasteurizing are 

 not sufficiently high or prolonged to destroy all germs and spores in milk, 

 but in many cases, over ninety-nine per cent, of the bacteria may be kill 

 by pasteurization. 



