PASTEURISED MILK

New Zealand Herald, Volume LXXIII, Issue 22579, 18 November 1936, Page 17

PASTEURISED MILK

Sir. —Your correspondent "Safety First" says that I made a number of incorrect statements in my previous letter 011 the above subject. I maintain that they are correct and based on scientific authority. (1) I said nature intended that bacteria (microorganisms) should be present in milk, but "Safety First" says:—"Milk from a healthy cow is quite sterile and contains no bacteria." If such were the case, fresh milk would be a dead inorganic fluid —devoid of cells and devoid of vitamins. But we know milk to bo a "live" food, with organised cells and teeming with vitamins. The only way to render milk "sterile." entirely free of bacteria, is by prolonged beating and evaporation, which kills tho bacterial life and vitamins, and converts the milk into condensed milk or into evaporated milk, in which condition it will keep indefinitely without fermenting. (2) I mentioned_ pasteurisation at 1(50 degrees to I<o degrees Fahrenheit, but "Safety First ' says (hat "Mo degrees Fahrenheit is seldom exceeded in pasteurising milk." Nevertheless the practice varies in different countries. It all depends upon the climate and the object aimed at, i.e., how long it, is required that the milk should keep after pasteurisation and the temperatures vary irom as low as 1 ,'U degrees Fahrenheit to as high as 175 degrees Fahrenheit. The higher the pasteurising temperature and the longer it is maintained, the greater is the destruction of bacterial life and the longer the milk will Jveep without tormention. (.'!) 1 said that curds and whey, junket, koumiss or yogurt are all products of successive stages in the fermentation of milk, but "Safety First" says that "these sjbstanccs are produced by enzymes from other sources and have nothing to do with bacteria." I entirely disagree and maintain that the lactic fermentation of milk is due to the very rapid multiplication ol the lactic bacteria always present iu small amounts even in fresh milk. Nothing need be added to the milk to .start this fermentation, although the addition of some previously prepared lactic milk culture increases both the rapidity and intensity of the fermentation. If freshly drawn milk, still at blood boat, is placed in a closed receptacle and wrapped in a blanket to keep in the heat and to keep out the air, and kept continuously warm, tho lactic fermentation starts and ends at the preliminary stage, the milk separating into curds and whey with a small lactic acid content. If this product is then added to other fresh milk and the same process repeated and again repeated two, three or four times, the fermentation becomes even more rapid and the final product is koumiss or yogurt with a high lactic acid content —a most nutritious food, now in great demand at the milk bars in London. Thomas A. F. Stone.