Phenotypic Diversity And Technological Properties Of Yogurt Cultures Isolated From Traditionally Produced Turkish Yogurts With Comparison To Commercial Starter Cultures

Abstract

Sixty Streptococcus thermophilus and 111 Lactobacillus delbrueckii subsp. bulgaricus isolates from traditionally produced Turkish yogurts were biochemically identified and examined for their technologically important features. Acidification profiles of the isolates were examined. Isolates with acidification rates comparable to those of commercial isolates were also tested for final pHs and acetaldehyde production after 24-h incubation. Selected isolates were also examined for their bacteriophage resistance and proteolytic activity. Twenty-five L. bulgaricus and 22 S. thermophilus isolates were selected based on their technological properties other than bacteriophage resistance. Bacteriophage resistance experiments revealed that all L. bulgaricus isolates except two were sensitive to the bacteriophages, while S. thermophilus isolates were resistant to most of the bacteriophages. The results show that yogurt bacteria isolated from traditional Turkish yogurts have significant phenotypic diversity and the technological properties of these isolates are comparable to tested commercial cultures.