1 82 THE ARTIFICIAL SOURING OF CREAM 



never as chains. The optimum temperature is 23 C. Its acid-producing powers 

 are so slight that the milk is never coagulated. The aroma developed in the milk 

 is initially delicate, but becomes progressively stronger, and finally (after a lapse 

 of several weeks) resembles that of fine cheese. As a result of further researches 

 published in 1896, CONN (II.) was led to conclude that acidification and the 

 production of aroma are independent phenomena. He considers that aroma is 

 developed by the activity of peptonising bacteria which separate volatile bodies (of 

 agreeable or offensive smell and taste) from the albuminoid constituents of the 

 cream. 



143. Defects in Butter. 



The advantages offered by this artificial method of souring cream are only 

 appreciated at their true value when its application cures certain defects in butter, 

 to which we will now refer, and which were formerly attributed exclusively to 

 bad fodder. In this case also bacteriologists have been able to confute erroneous 

 opinions and render valuable assistance to practice. 



There is probably not a single dairy in North Germany or Denmark whose 

 butter has not at some time or other been " oily," i.e. exhibited a flavour 

 recalling that of mineral oil. This malady appears with particular frequency in 

 dairies deficient in appliances for keeping the souring cream and finished butter 

 sufficiently cool. Weigmann showed that both the acid generator (prepared by 

 spontaneous acidification) and the butter-milk of such dairies are very impure, 

 in a bacteriological sense, and he was invariably successful in remedying the 

 complaint by the introduction of artificial souring. 



A second and not less injurious defect is the so-called turnip flavour. Butter 

 suffering from this complaint has a repulsive sweet taste, recalling that of 

 turnips. To throw the responsibility on the latter is an obvious, but not always 

 justifiable, procedure, since cases are known where neither the cows nor any of 

 the dairy appliances had come into contact with turnips, notwithstanding which 

 the flavour still made its appearance in the butter. C. 0. JENSEN (I.) discovered, 

 in 1891, in the milk of several Jutland dairies where this complaint had long 

 been rife, a microbe which he named Bacillus fcetidus lactis, and which was 

 recognised as the cause of the malady. This motile bacillus has a breadth of 

 0.4-0.6 ft, its length varying usually between o.y and 1.5 /*, and often attaining 

 5.5 ft. No spore- formation has been detected, and the organism does not liquefy 

 nutrient gelatin. As its second name implies, this bacillus gives rise to stinking 

 decomposition in milk, but is not the only species producing the same complaint, 

 Jensen himself having grouped along with it a number of others possessing the 

 same power, among them being several species of micrococcus (not more 

 definitely named), a Merismopedium, &c. The employment of pure cultures of 

 lactic acid bacteria gave satisfactory results, producing a pure and fine-flavoured 

 butter in place of the previously almost unsaleable article. 



A third evil which is probably (though not yet indubitably) attributable to 

 bacteria, is the so-called fishy or train-oil flavour in butter. Other defects, such 

 as greasy, tallowy, cheesy butter, have their origin in the inferior chemical com- 

 position of the cream ; whilst for the third group of complaints, e.g. stable smell 

 and smoky smell, the uncleanliness of the milker is responsible. 



How firmly the injurious bacteria settle themselves in the rooms of the 

 infested dairies is evident from the observations made by Ronneberg, according 

 to whom the beneficial results accruing from the employment of pure cultures 

 of acid bacteria in infested dairies are only temporary, and disappear if fresh 

 supplies of the invigorating pure culture are not introduced in good time. 



The advantages of this new method are so numerous that its employment 

 should not be delayed until the maladies in question appear ; in fact, the method 



