Abstract
Hydrogen peroxide is considered one of the important factors that decrease the viability of the probiotic Bifidobacterium in yogurt. In the present study, we investigated the effect of hydrogen peroxide produced by yogurt starters on the viability of Bifidobacterium. We first evaluated the hydrogen peroxide productivity of 11 yogurt starter strains (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus). The amount of hydrogen peroxide produced by L. bulgaricus was five times higher than that produced by S. thermophilus cultivated in 10% (w/v) reconstituted skim milk at 37℃ for 16 h. Then, hydrogen peroxide production by L. bulgaricus under anaerobic conditions was 65% lower than that under aerobic conditions. In addition, generation of hydrogen peroxide was associated with bacterial cell counts of L. bulgaricus rather than those of S. thermophilus in a lactate buffer. These results indicate that the accumulation of hydrogen peroxide in yogurt is attributed to oxygen metabolism of L. bulgaricus. Reduction in inoculated cell number of L. bulgaricus decreased the accumulation of hydrogen peroxide and significantly improved the viability of Bifidobacterium adolescentis KH 96 in yogurt during storage.
