Short Research Communication: Production of Yogurt by locally isolated starters Streptococcus thermophilus and Lactobacillus bulgaricus

Abestract: The aim of this study was to produce yogurt using isolated native starters Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus  salivarius subsp. thermophilus. The native starters were isolated, purified and identified according to Bergey's manual of determinative bacteriology. Yogurt was made by two methods, the first method was made by the combination of L . bulgaricus and  S. thermophilus in equal ratios and which were inoculated directly into a pasteurized milk. The second method was done using the isolated bacteria that was prepared from the culture media MRS and M17 respectively, through two transfers in 10% skimmed milk medium overnight, and then 3% of these cultures were inoculated into milk separately. The mixture was incubated at 42?C for 6-8 hours and coagulation was observed. Yogurt PH and volume were measured of and our results indicate that the first method was better than the second one. It is well known that yogurt production using native starter cultures instead of commercial ones is beneficial in respect of both economic and organoleptic aspects. Our results indicate that the isolated native yogurt starters can be used in yogurt manufacturing in an industrial large scale.