WHY MILK SPOILS OR KEEPS.

Otago Witness, Issue 2660, 8 March 1905, Page 6

WHY MILK SPOILS OR KEEPS.

1 Tn an expeiiment on the relation of temperature to the keeping qualities of milk at the Connecticut Storrs (Station, the following results were found : —The bacteria 1 in milk multiplied five-fold in 24 hours -when the temperature -«as 50deg Fahr., and 7^o fold in the same time when the temperature was 70deg. Milk at 95deg curdled in 18 hours, at 70deg in 48 hours, and at 50deg in 148 hours. So iar as the keeping property of milk is concerned, low temperature is considered of more importance than cleanliness. In milk kept at 95deg, the species developing most; rapidly is the undesirable one known as the bacillus Lactis aerogencs. At a temperature of TOdeg this species develops relatively less rapidly in the majority of cases than bacillus lactis acidi, which latter is very desirable both in cream and cheese ripening. The bacteria in milk kept at 50deg mci eases slowly, and later consists of very few lactic organisms, but of miscellaneous types, including many forms that render the milk unwholesome. These bacteria continue to grow slowly day after day. but the milk keeps sw tet because the lactic oreamsms do not develop abundantly. Such milk, in the course of time, becomes far more unwholesome than sour milk, since it is filled with organisms that tend to produce putrefaction. Although the temperature of 50deg is to be emphatically recommended to dairymen for the purpose of keeping their milk sweet and in a proper condition for the market, they must be especially on their guard against the feeling that milk that is several days old is proper for market, even though it is still sweet and has not curdled. This very considerably modifies some of our previous ideas concerning milk. Old milk is never wholesome thought it is still sweet and has not curdled. It has generally been believed that so long as milk remains sweet it is in good condition for use. Quite the contrary is the case, if it has bean kept at a temperature of 50deg, or in this vicinity. It is not unlikely that it is this fact that leads to some of the cases of ice-cream poisoning so common in summer. The cream is kept at a low temperature for several days, until a considerable quantity has accumulated or a demand ha come for ice-cream, and when made into ice-cream it is filled with bacteria in great numbers, and of suspicious character. These results may be read with interest by dairy farmers, though with one conclusion arrived at it- is to be hoped fewwill be inclined to agree —viz., "That lowtemperature is of more importance in the keeping property of milk than cleanliness." It has b-?en lately ascertained by experiment in England that milk properly strained will keep 12 hours longer than that not so treated. The great difficulty hitherto has been to find means for efficient straining of milk, and no matter what care is t^aken, ordinarily a certain amount of cow-dung, cow-hair, and scurf finds its way into the pail during milking. Probably the' difficulty has been met by the invention of a patent strainer recently developed and placed on the market by Messrs Whatley and Co., Powsey, Wilts, England, which has a gauze containing 14,700 holes to the square inch, and absolutely removes all impurities. The strainer is a revolving one, the motive power being supplied by a turbine, driven by the outflow from the refrigerator. At each revolution a brush, which also revolves, sweeps all refuse into a receptacle, so that the milk always falls upon a clean surface. The Mark Lace Express says: —The need for such an invention has become imperative, and many London milk buyers are insisting on it 3 use at the dairies puichased at by them.