Microbes such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it into curd. During growth, such bacteria produce acids (mainly lactic acid) that coagulate and partially digest the milk proteins. A small amount of curd, known as starter, is added to the milk and kept at suitable temperature, where lactic acid bacteria multiply in millions and convert milk into curd that also improves its nutritional quality by increasing vitamin . They also check growth of disease causing microbes in the stomach.