External factors such as nutrition may temporarily exchange the mix of bacteria in adults. But the composition of flora in grownups is remarkably stable over time. Consuming probiotics has short-term effects on the flora composition and thereby balances the number of ‘good’ (lactobacilli, bifidobacteria and so on) and ‘bad’ bacteria (such as Salmonella and E. coli) in the intestines. ‘However, encapsulation does not resolve all technological bottlenecks,’ Dr Saarela says. ‘The benefits of these techniques depend on several factors, including the type of bacteria and the food that they are applied to.’ Stress treatments to improve viability of probiotic bacteria show potential. ‘By gently exposing probiotics to acid or hot environments, the stress treatment activates genes in the bacteria that make them more resistant to acidity and heat,’ she says. The University of Helsinki and VTT Biotechnology have had promising results from their research on stress treatment—viability can be improved up to 10,000-fold. According to both Prof Isolauri and Dr Saarela, the most interesting future applications of probiotics are in specific target groups, such as children with allergies, and older people. ‘[The] elderly are more susceptible to infections and more sensitive to side-effects of medicines,’ Prof Isolauri says. She expects that in the next two decades most of the remaining questions on probiotics, such as host-microbe interactions, working mechanisms and long-term effects, will be answered. ‘By then, we may have a multifunctional “probiotic cocktail” with components that are released at optimum locations in the gastrointestinal tract.’ she says. *LISETTE DE JONG IS A REPORTER FOR OUR SISTER MAGAZINE, FOOD ENGINEERING & INGREDIENTS