Microbes from raw milk for fermented dairy products

Milk has a high nutritive value, not only For the new-born mammal and for the human consumer, but also for microbes. Raw milk kept at roam temperature will be liable to microbial spoilage. After some days, the milk will spontaneously become sour. This is generally due to the activity of lactic acid bacteria. A flora of these bacteria may develop, which can be transferred deliberately to fresh milk in order to maintain or even strengthen it. This principle is the basis for controlled acidification of milk towards products, sustainable and safe, with most often an attractive flavour. Various types of fermented milks and derived products have been developed in all parts of the world, each with its own characteristic history. Their nature depends very much on the type of milk used. on the pre-treatment of the milk, on the temperature (climate) and the conditions of fermentation and on the subsequent technological treatments. Most fermented dairy products contain lactic acid bacteria, but other bacteria, yeasts and moulds may be involved as well. In optimising the manufacturing processes, starter cultures for fermented dairy products have been developed. They are composed of selected microorganisms, propagated as multiple-strain starters consisting of a defined mixture of pure cultures or as mixed-strain starters consisting of an undefined mixture of different types of bacteria. The use of starters, on the one hand, has been tremendously positive with respect to the quality of the product, but, on the other hand, it has diminished the diversity of fermented dairy products. Since the dairy industry is keen to explore new possibilities for enhancing the diversity of its product range, there is a new interest nowadays in searching for potential starter organisms from the pool, which existed at the time of raw milk fermentation. This contribution reviews some potential opportunities and recent developments in this search. (C) 2002 Elsevier Science Ltd. All rights reserved