At least two other cases of similar flavor have been known; but no cause was evident in either case. The trouble is very infrequent, at worst, and is here discussed mainly to show how easily a trouble due to one cow can be located by taking individual samples of the milk; and how cheaply gotten rid of by leaving out the objectionable product.
Bitter Flavor in Neufchatel Cheese.
An uncompleted
study.
A little better result than that in the study of fishy flavor was reached in the investigation of a bitter flavor in Neufchatel cheese; but this study also had to be left incomplete. The trouble in the factory was easily remedied; and the germ responsible for the outbreak was obtained in pure culture; but full study of the fault in all its bearings was hindered by the refusal of the herd owner to admit that the trouble was due to his milk. The investigation had to stop with the guilty herd; it did not locate the original source of infection.
Method of
detection.
This bitter flavor is not the same as the bitterness quite common in milk and cream at certain seasons of the year; as the milk itself tasted and smelled all right until well along in the process of cheese-making when the curd was being ærated and drained. The flavor was noticed in the factory in October and could not be checked, though the maker took great pains to wash and scald all his utensils and everything which touched the milk after it came from the farm. To locate the trouble, samples were taken of the milk of each patron and the cheese-making process started with each sample. In 18 hours all the samples of curd appeared normal but two, which were gassy and bad-smelling; and one of these, when drained and exposed to the air, showed a pronounced bitter flavor. This sample proved to be from the dairy which had furnished the milk for making the Neufchatel, a milk specially selected because of its high fat-content. This furnished direct proof that the fault lay in the milk, not in its factory handling; and rejection of this milk ended the trouble in the Neufchatel. As already stated, the study could not be carried into the herd to see whether one cow, wrong stable surroundings, a stagnant pool of water or contaminated dairy utensils were to blame for the trouble in the factory.
Bacteria
blamable.
Samples of this faulty milk were taken for laboratory study and various bacteria and molds were separated. This was done by diluting the milk with a sterilized fluid so that the germs were quite widely separated when the milk was poured out in flat glass dishes. Each kind of germ is marked by some peculiarity of growth which makes it possible to distinguish between them; and pure cultures can be made by transferring a little of the growing colony to a new dish of sterilized agar, gelatin or other material suited to germ life. From these pure cultures fresh milk from the Station herd was inoculated and small Neufchatel cheeses made. No bitter flavor was noticed in similar check cheeses; and the milk containing only one of the forms of germ life found produced bitter cheese. The bitterness, as in the factory, was noticed only after the curd was drained and ærated. Soft, poorly-drained curd was free from the flavor though well inoculated with the short bacillus which produced the bad flavor in well-dried curd. This shows that the germ is one which requires exposure to the air to develop the bitter compound in the cheese. Unfortunately this germ, when cultivated in milk for some time lost the power of producing bitter cheese, so the investigation came to an end.
Sweet Flavor in Cheddar Cheese.
A new cause
of cheese
faults.