Probiotic bacteria in fermented foods: product characteristics and starterorganisms

Probiotic bacteria are sold mainly in fermented foods, and dairy products p lay a predominant role as carriers of probiotics. These foods are well suit ed to promoting the positive health image of probiotics for several reasons : 1) fermented foods, and dairy products in particular, already have a posi tive health image; 2) consumers are familiar with the fact that fermented f oods contain living microorganisms (bacteria); and 3) probiotics used as st arter organisms combine the positive images of fermentation and probiotic c ultures. When probiotics are added to fermented foods, several factors must be considered that may influence the ability of the probiotics to survive in the product and become active when entering the consumer's gastrointesti nal tract. These factors include 1) the physiologic state of the probiotic organisms added (whether the cells are from the logarithmic or the stationa ry growth phase), 2) the physical conditions of product storage (eg, temper ature), 3) the chemical composition of the product to which the probiotics ate added (eg, acidity, available carbohydrate content, nitrogen sources, m ineral content, water activity, and oxygen content), and 4) possible intera ctions of the probiotics with the starter cultures (eg, bacteriocin product ion, antagonism, and synergism). The interactions of probiotics with either the food matrix or the starter culture may be even more intensive when pro biotics are used as a component of the starter culture. Some of these aspec ts are discussed in this article, with an emphasis on dairy products such a s milk, yogurt, and cheese.