176 EXPERIMENT STATION EECORD. 



the farms whore tlio fisliy tlavor was (l('vel()|)e(l was the prcsfMice of very active 

 lactu-aciil bacteria. 



"In all cases in wliicli the records were complete it was found that those 

 experimental butters wliich became fishy were made from high-acid cream. 

 Fi.shy butter was made from cream acidified with lactic and acetic acids. How- 

 ever, cream with high acidity does uot uniformly develop tishiness." It was 

 apparent that acidity although having a determining influence on the fishy 

 flavor was not its sole cause. The effect of overworking butter was next in- 

 vestigated, and it was observed that fishiness occurred only in a combination of 

 high acidity and overworlving. Further experiments in this line show^ed that 

 overworking improved rather than impaired the flavor of the unripened cream 

 butter, but evidently hastened the appearance of the fishy flavor in the ripened 

 cream butter. The increased amount of air by overworking was determined 

 with Barcroft's apparatus, a descrii)tion of w^hich is given. 



" In the o]iiuion of the writer, fishy flavor is caused by a slow, spontaneous, 

 chemical change to wliich acid is essential and which is favored by the presence 

 of small amounts of oxygen. Fishy flavor may be prevented with certainty by 

 making butter from pasteurized sweet cream. Butter made from pasteurized 

 sweet cream with a starter but without ripening seldom if ever becomes fishy.'" 



The use of starters in butter m.aking, F. W. Bouska {loiva Sta. Bui. 103, 

 pp. 217-229). — This bulletin reports experiments wath starters and contains gen- 

 eral information on their use in butter making. 



The acidity of milk, diluted milk, and milk to which milk sugar, brown sugar, 

 and glucose had been added, whey, whey and ground casein, and various mix- 

 tures of chalk, peptone, glucose. l)icarbonate of soda, and potassium hydrogen 

 phosphate are tabulated. " The whey produced about the same acidity (0..3G per 

 cent) as the sugar solution containing H to 10 per cent milk (0.2 to 0.3 per cent). 

 But the whey and curd produced nearly as much acid (0.59 per cent) as the 

 milk (0.74 per cent). Therefore the casein favors the development of acid." 

 The acidity w^as low when sugar or a base was lacking. In mixtures containing 

 sugar, protein, and a base the acidity was as high as in millv. . The casein of 

 sweet milk fulfills the office of a base. 



" The use of chalk in deep vessels of starter is not feasible because it settles to 

 the bottom. Theoretically, bicarbonate of soda seemed better suited. . . . Potas- 

 sium hydrogen phosphate was substituted for the l)icarbonate of soda to test the 

 effect of a phosphate. Six trials gave no more acid than was usually developed 

 in the same mixture without the phosphate. Glucose solutions containing small 

 quantities of sodium hydroxid did not favor the development of acid." 



Practical tests were made with glucose and condensed milk starters. " The 

 low acidity of the glucose starters gives them weak tastes. They contain about 

 as many bacteria as a milk starter and require from 2 to 3 times as much time 

 to ripen cream. The flavor of the glucose starter butter is practically as good as 

 that of milk starter butter. Reckoning milk at $2 a hundredweight and glucose 

 at 10 cts. a pound, the material for 100 lbs. of glucose starter costs 50 cts." 

 Condensed milk gave the best results when diluted with 3 to 4 parts of water. 



Starters were carried in pasteurized and in sterilized milk, but the results 

 were not conclusive. It is stated that the flat flavor frequently noticed in the 

 early stages of ripening is probably caused by euzyms acting on the casein. It 

 was found that it had been introduced accidentally by neutralizing the starter 

 with Jimmonia, and that ammonium lactate has this flat flavor. In a study of 

 overripeniug of cream it was found that the increase of O'idiuin lactis had a 

 more direct relation with bad flavors than did the numbers of putrefactive 

 bacteria. 



