Probiotics must be consumed at a level of 10^7CFU/mL for successful colonization of the gut. In yogurts containing beneficial cultures, the survival of probiotic strains can quickly decline below this critical concentration during cold storage. The inclusion in yogurt of beta-glucan, a possible prebiotic for bifidobacteria also known to have heart-healthy effects, would increase the healthfulness of yogurt. We hypothesized that beta-glucan would increase the viability of bifidobacteria strains in yogurt during cold storage. Yogurts were produced containing 0.44% beta-glucan (concentrated or freeze-dried) extracted from whole oat flour and/or 1.33% corn starch, and bifidobacteria (B. breve or B. longum) at a concentration of at least 10^9 CFU/mL. All yogurts were stored at 4yC. Bifidobacteria and yogurt cultures, S. thermophilus and L. bulgaricus, were enumerated from undisturbed aliquots before fermentation, after fermentation, and once a week for five weeks. S. thermophilus and L. bulgaricus maintained a concentration of at least 10^8 CFU/mL in yogurts containing concentrated or freeze-dried beta-glucan regardless of starch addition, and in the control with no added beta-glucan or starch. Similarly, the probiotic, B. breve, survived above a therapeutic level in all treatments. The addition of beta-glucan prolonged the survival of B. longum at a concentration of at least 10^7 CFU/mL by up to two weeks on average beyond the control. Further, the inclusion of concentrated beta-glucan in yogurt improved survival of B. longum above 10^7 CFU/mL by one week longer than did freeze-dried beta-glucan. Study results suggest that beta-glucan has a protective effect on bifidobacteria in yogurt when stressed by low-temperature storage. The combined benefits of the heart-healthy effects from beta-glucan and of the gut-health effects from bifidobacteria should provide the food industry with information needed to formulate more healthful yogurt products.
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