Bitter Milk. 



Porcelain vessels and bottles made from glass free of lead are 

 most suitable for the preparation of buttermilk, since the butter- 

 milk may extract lead from enameled earthenware and from pots 

 whose glazing contains lead in its composition. 



According to Chlopin . 84 mg. of lead was extracted from 100 

 gm. lactobacillin-buttermilk ; in a second portion (300 gm. butter- 

 milk) which was five days old, the amount reached 7 . 86 mg. Briick- 

 mann obtained similar results : 300 gm. of ordinary buttermilk con- 

 tained after four days 4.2 mg., and after six days 5.7 mg. of lead, 

 when this product had been prepared in pots with lead-containing 

 glazing. 



Defects of Milk. 



Bacteria produce certain modifications in milk which partly 

 on account of their frequency are designated as normal processes, 

 or again others appear which are less frequently observed, occur- 

 ring only under special conditions and therefore are known as 

 milk defects. The modification, as has been seen, may be even 

 desirable, as for instance in cream souring and cream ripening 

 for butter making, or in the preparation of Kefir, Yoghurt, and 

 buttermilk, or it may be undesirable and injurious, spoiling the 

 milk, and having a disturbing influence on milk utilization, espe- 

 cially in its use for drinking purposes. 



Among the changes in milk there are those which appear fre- 

 quently, and others which are very rare. 



Under conditions which favor propagation of peptonizing 

 bacteria (staphylococci, sarcina, anthracoides, mycoides, mesen- 

 tericus varieties, fluorescens, pyocyaneus, etc.), the milk attains a 

 bitter taste. 



For instance if uncooled milk is filled into cans which are 

 immediately closed it " suffocates," acquiring a strong stable 

 odor which may even reach a putrid character, causing a solution 

 of the casein by reason of which- the milk no longer coagulates ; or 

 the appearance of a bacterial rennet produces a rennet-like pre- 

 cipitation of the casein, and the milk coagulates without turning 

 sour. It is "sweet-coagulating." By the action of peptonizing 

 micrococci, which in part are psychrophilic the development of a 

 bitter taste may occur in thoroughly cooled, and even in excessive- 

 ly cooled milk. The bacteria of the colon group when the condi- 

 tions of their propagation are favorable may produce an odor in 

 milk ranging from aromatic to rancid, or some varieties of this 

 group which have grown on mangels may confer the odor of man- 

 gels to the milk. 



A bitter taste in milk may also occur from the feeding of foods 

 containing bitter substances, thus for instance from the feeding 

 of lupins, vetches, mangels, camomile, beet leaves, wood-fern, raw 

 potatoes, mouldy or spoiled hay, straw, etc. It may however be 

 accepted that the development of a bitter taste in milk usually 



