Interest in the role of probiotics for human health goes back at least as far as 1908 when Metchnikoff suggested that man should consume milk fermented with lactobacilli to prolong life (Hughes & Hoover, 1991; O’Sullivan, Thornton, Sullivan, & Collins, 1992). It is only recently, however, that the interrelationship between intestinal microorganisms and the health benefits deriving from it are beginning to be understood. At present it is generally recognised that an optimum ‘balance’ in microbial population in our digestive tract is associated with good nutrition and health (Rybka & Kailasapathy, 1995). The microorganisms primarily associated with this balance are lactobacilli and bifidobacteria. Factors that negatively influence the interaction between intestinal microorganisms, such as stress and diet, lead to detrimental effects in health. Increasing evidence indicates that consumption of ‘probiotic’ microorganisms can help maintain such a favourable microbial profile and results in several therapeutic benefits. In recent years probiotic bacteria have increasingly been incorporated into foods as dietary adjuncts. One of the most popular dairy products for the delivery of viable Lactobacillus acidophilus and Bifidobacterium bifidum cells is bio-yogurt. Adequate numbers of viable cells, namely the ‘therapeutic minimum’ need to be consumed regularly for transfer of the ‘probiotic’ effect to consumers. Consumption should be more than 100 g per day of bio-yogurt containing more than 106 cfu mL−1 ( Rybka & Kailasapathy, 1995). Survival of these bacteria during shelf life and until consumption is therefore an important consideration.