73-6 |
Viability of bifidobacteria in commercial yogurt products in North Carolina |
J. P. CARR1, S. A. Ibrahim1, A. Bynum1, C. W. Seo1, G. Shahbazi2, and M. Worku3. (1) Food Science and Nutrition, North Carolina Agricultural and Technical State University, 171 B carver hall, Food Safety Microbiology laboratory, Greensboro, NC 27411-1064, (2) Food Bioprocess Engineering, North Carolina Agricultural and Technical State University, (3) Animal Biotechnology, North Carolina Agricultural and Technical State University Today, approximately 30-50% of refrigerated yogurt products in the US contain viable bifidobacteria and lactobacillus acidophilus. However, during processing and storage, the number of viable cells tends to decline due to severe conditions such as oxygen and acid. There are few scientific studies reporting the viability of bifidobacteria in commercial yogurt products in the U.S. The purpose of this work is to screen the yogurt products in North Carolina for viable yogurt cultures, specifically bifidobacteria, and to test these isolates for probiotic properties including antimicrobial ability and b-galactosidase activity. Fifty-eight commercial yogurt products (containing bifidobacteria in addition to the traditional yogurt culture) were obtained from local stores in Greensboro, NC. Experiments were performed within 24 h of purchase. MRS and G M17 were used for the enumeration of Lactobacillus bulgaricus and Streptococcus thermophilus, respectively. Modified BIM-25 was used for the enumeration of bifidobacteria. All plates were incubated for 72 h at 37oC. Isolates of bifidobacteria were examined for phenotypic and genotypic characteristics. Isolates were also examined for antimicrobial ability and b-galactosidase activity. Our results showed that the bacterial counts ranged from 5.0 to 9.89 log10CFU/ml, 6.6 to 9.48 log10CFU/ml, for Streptococcus, and Lactobacillus respectively. The counts for bifidobacteria were varied among the tested samples ranging from 0 to 5.0 log10CFU/ml. Of the 58 products claiming the inclusion of Bifidobacteria in their product, 44 (75.9 %) contained viable cultures. None of the tested products the number of bifidobacteria exceeded 5 log. Results showed that products made by only 2 manufacturers contain viable number of bifidobacteria in yogurt products. The effect of storage at 4oC had little effect on the viability of all microorganisms. The b-galactosidase activity for bifidobacteria isolates ranged between and. Few isolated strains showed antimicrobial activity against E. coli and Micrococcus lutus. The PCR fingerprinting procedure indicated that bifidobacteria were closely related. North Carolina’s regulation on viable probiotic bacterial counts should be more restrictive to ensure that products deliver a sufficient amount of viable bifidobacteria.
Session 73, Dairy Foods: Probiotics and bioactive components in milk
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