title: Viability of bifidobacteria strains in yogurt with added oat beta-glucan and corn starch during cold storage.
abstract: Probiotics must be consumed at a level of 10(7) CFU/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. 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% modified corn starch, and bifidobacteria (B. breve or B. longum) at a concentration of at least 10(9) CFU/mL. All yogurts were stored at 4 degrees C. Bifidobacteria and yogurt cultures, Streptococcus thermophilus and Lactobacillus delbureckii subsp. bulgaricus, were enumerated from undisturbed aliquots before fermentation, after fermentation, and once a week for 5 wk. 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, Bifidobacterium breve, survived above a therapeutic level in all treatments. The addition of beta-glucan prolonged the survival of Bifidobacterium longum at a concentration of at least 10(7) CFU/mL by up to 2 wk 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 1 wk 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.
authors.affiliation: Dept. of Food Science and Human Nutrition, Iowa State Univ., Ames, Iowa 50011, USA.
authors.forename: Valerie
authors.initials: V
authors.lastname: Rosburg
authors.forename: Terri
authors.initials: T
authors.lastname: Boylston
authors.forename: Pamela
authors.initials: P
authors.lastname: White
mesh_terms: D018554:Avena; D001644:Bifidobacterium / Q000254:growth & development*; D003080:Cold Temperature; D015169:Colony Count, Microbial; D005285:Fermentation; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D050296:Microbial Viability; D013213:Starch; D015014:Yogurt / Q000382:microbiology*; D003313:Zea mays; D047071:beta-Glucans
chemical_list: D047071:beta-Glucans; C067858:beta-glucan, (1-3)(1-4)-; D013213:Starch