A Bacteriological Study of Curdled Milk (Dahi)

Curdled milk or milk fermented by the action of certain bacteria has been used for many centuries in different parts of the world. The yoghurt of the Balkans, the busa of Turkestan, the kefir and the kourniss of Russia and the lebuvi of Egypt are examples of curdled milk. These milk products are of great dietetic value and have been regarded as miraculous remedies for many ills. The fact that so many races make soured milk and use it copiously is by itself an excellent testimony to its usefulness. It was, however, largely owing to Metchnikoff that a great impetus was given to the multiplication of laboratory preparations containing cultures of lactobacilli. According to Metchnikoff, lactobacilli inhibit the growth of intestinal putrefactive organisms and thus prevent digestive troubles, rheumatism and generally prolong life. Considering the claims which were made on its behalf it is no wonder that Lactobacillus milk came into demand in all civilized countries and people ate not only curdled milk but swallowed lactobacilli tablets which frequently contained no viable bacilli. In India curdled milk (dalii) or one of its preparations has been used from time immemorial. In the earliest days of medicine, centuries before the Christian era, the great physician Sushruta drew attention to the great value of curdled milk and described in detail several different methods of preparation with their respective properties. The curdled milk is usually prepared by boiling the milk, cooling it to about 40?C. and then inoculating it with a small amount of curdled milk which contains the group of organisms known to yield a suit-