EXPERIMENT STATION BULLETINS. 207 



BACTERIA IN BUTTEEMAKING. 



Sweet cream makes an insipid butter, unmarketable and undesirable. 

 We have always been accustomed to butter made from soured cream, 

 and unless we have an evolution in taste, butter made from soured cream 

 will always be in demand. We know from our discussions so far that 

 there is always a possibility of having bacteria present which will induce 

 within the cream abnormal changes. It 'sn therefore a matter of import- 

 ance to secure if possible only those bacteria which will produce 

 the desired change in the cream. In seeking these bacteria, it should 

 be the aim to select those varieties which will give rise to that peculiar 

 acid flavor coming from soured cream, as well as the nutty flavor arising 

 from the aroma and to yield a biftter of good keeping qualities. Having 

 once gained such a species of bacteria, we shall then be able to obtain 

 a uniform product. As to the acid flavor in butter, there is some ques- 

 tion. Dr. Conn makes the claim that acid-producing bacteria are not 

 essential in the production of rich flavored butter. His experience with 

 bacteria in the ripening of cream commands consideration, but there 

 are those who positively affirm that acid-producing bacteria are abso- 

 lutely essential to a highly flavored butter. Inference would lead us to 

 suppose that one's taste is accustomed to the acid flavor, and of 

 course, would demand it. On the other hand, there is no doubt that the 

 non-acid variety of bacteria will give delicate shades of tastes which 

 would be very pleasing to a connoisseur. It cannot be expected, how- 

 ever, that the laity will cultivate their tastes to these delicate shades. 

 When we bear in mind that the keeping quality of butter is a very neces- 

 sary property, we are led to believe that the acid-producing bacteria are 

 the more desirable. Out of thirty or forty bacteria isolated from milk, 

 it will be noticed that those which form acid stop their growth when 

 the acid has reached such an amount as to inhibit their growth. The 

 acid formed is usually sufficient to inhibit the growth of other bacteria 

 for a considerable length of time, barring out certain species. The non- 

 acid producing bacteria generally at first curdle the milk, then continue 

 their action by peptonizing the casein giving rise many times to dis- 

 agreeable products. If this latter class of bacteria, should be used in 

 ripening cream, we should expect a continuous change in products from 

 the very beginning of the ripening process to the final decomposition 

 products of butter, hence the keeping qualities would be lowered. 



Therefore to obtain a good flavored butter, a good keeping butter and 

 a uniform product, it is necessary to resort to "starters," of the proper 

 kind established only by experimentation. 



There are several kinds of starters in use: a sour milk starter, a 

 buttermilk starter, a ripened cream starter and a pure culture starter. 



The sour milk starter has been used commonly by dairymen of late and 

 it has furnished satisfactory results in those cases where it has been 

 impossible to obtain pure cultures of bacteria. Close attention, however, 

 must be given to the appearance of the soured milk. It is conceded 

 that a truly loppered milk is best for this purpose, for it represents the 

 typical action of the lactic acid bacteria. It is obtained usually by allow- 

 ing the cream to rise by the gravity system and after the cream is 

 removed, the skim-milk is utilized as a starter. This starter mav be 



