ABSTRACT
The primary species of lactobacilli used as starter cultures in the manufacture of cultured milk products are homofermentative. Lactobacillus bulgaricus and L. lactis are the species most often encountered. Products in which these are used include yogurt, Swiss cheese, Italian cheese, Emmental cheese, Bulgarian buttermilk, kefir, and koumiss. While the lactobacilli must possess at least some proteolytic activity in order to grow in a product such as milk, they are not sufficiently proteolytic to be so classified with regard to identity characteristics. They also are considered to be nonlipolytic. Taxonomically, the lactobacilli are not considered to be proteolytic, although in order to grow in milk they must be sufficiently proteolytic in order to obtain the needed nitrogen from the milk proteins. The proteolytic activity of these microorganisms may well contribute to the texture and flavor properties of cultured milk products in which they are used as starter cultures.
