216 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



responsibility for the financial side of the business beyond the cost of 

 manufacture. This will make it possible to carry on invcstif^ations 

 in the management and operation of a large creamery, in addition to 

 the more technical work in butter making. The Troy creamery is 

 easily accessible from Washington, thus increasing the efficiency of 

 the lield laboratory without adding to the expense of operation. 



MILK INVESTIGATIONS. 



The milk investigations have included a continuation of the work of 

 the previous year in studying the bacteria of pasteurized and raw 

 milk. The results of this study were published as Bulletin 126 of 

 the bureau. One of the most interesting facts brought out by this 

 work is that pasteurized milk ordinarily does not decompose, as it is 

 generally supposed to do, but sours in a normal way. While this 

 work was not sufficiently extensive to warrant final cc^nclusions, it 

 indicates very strongly that pasteurized milk often contains a higher 

 percentage of lactic-acid-forming bacteria in comparison with other 

 forms of bacteria than raw milk does. In this connection 300 cultures 

 were examined for fermentative ability, and a new medium has been 

 developed which promises to be of much value in milk work. This 

 study has also included the bacteria which produce alkalinit}^ in milk. 



The subjects of buttermilk and whey as by-products are under 

 investigation, and the production of an excellent massage cream by 

 means of separating the curds from buttermilk has resulted. It has 

 been found that an active culture of Bacillus hulgaricus is capable of 

 converting nearly all the milk sugar in whey into lactic acid. This 

 is particularly interest ing since about 10,000,000 pounds of lactic acid, 

 valued at $158,000, was made from glucose in this country in 1905. 



Chemical work in connection with this investigation has supplied 

 some exact information on the subject of chemical changes in milk 

 due to pasteurization. This study has developed some interesting 

 results pertaining to the proteids most likely to be coagidated by heat. 

 Milk heated for 30 minutes to 145° F. showed no change. At 150° F., 

 5 per cent of the albumin and globulin were precipitated. At 155° F. 

 12 per cent of these were precipitated, and at 160° F. 30 per cent. 

 Similar results have been obtained relative to changes in the ash, and 

 in determining the time required for coagidation with rennet. In 

 the latter case milk heated to 150° F. for 30 minutes showed no 

 change In the time required for coagulation, but when heated to 176° 

 F. for 30 minutes the time of coagulation was increased threefold. 

 Milk pasteurized at 145° F. is therefore free from the objection some- 

 times, urged against pasteurization because of the alleged precipita- 

 tion of albumen. This objection applies only when the milk is heated 

 to an unnecessarily high temperature. 



About 150 samples of goat's milk have been analyzed for moisture, 

 fats, and solids, opportunity being afforded to make these analyses on 

 milk furnished by the Animal Husbandry Division. 



The investigation relating to lactic-acid bacteria is complete and 

 the results are being prepared for publication. This investigation 

 has established the possibility of separating this group into distinct 

 and well-defined subordinate groups. An investigation of the gas- 

 forming bacteria in milk is under w ay. 



In the milk-secretion investigations carried on at Columbia, Mo., 

 in cooperation with the Experiment Station of the University of 

 Missouri, the principal Unes of work for the past year have been: 



