Determination of Some Aroma Metabolites of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus Isolates from Traditional Yogurt, by HPLC

This study was conducted to determine lactic acid bacteria isolated from Turkish yoghurts produced by traditional methods, amounts of usage of milk lactose in carbohydrate metabolism and formate, pyruvate, 3-hydroxy-2-butanone (acetoin), ethanol and 2,3-butandiol production amounts by HPLC. Two lactic acid bacteria species, widely used in traditional and industrial yoghurt production Streptococcus thermophilus (St. thermophilus) and Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus) were used from cultural stock. Production potentials of the above mentioned metabolites of 88 pieces of St. thermophilus and 12 pieces of Lb. bulgaricus were researched in different mediums and milk. St. thermophilus isolates were grown in anaerobic SM17, aerobic SM17, LM17 and milk and Lb. bulgaricus isolates were grown in anaerobic MRS (Man, Rogosa and Sharp Broth), aerobic MRS and milk. Amounts of formate, pyruvate, 3-hydroxy-2-butanone, ethanol and 2,3-butandiol determined by HPLC of St. thermophilus isolates were specified respectively as 0.1 +/- 0.0-77.0 +/- 0.2 mg/kg, 0.1 +/- 0.0-90.2 +/- 0.0 mg/kg, 0.1 +/- 0.0-127.0 +/- 8.4 mg/kg, 2.1 +/- 0.0-191.4 +/- 1.1 mg/kg and 1.1 +/- 0.0-130.0 +/- 5.2 mg/kg. Amounts of formate, pyruvate, 3-hydroxy-2-butanone, ethanol and 2,3-butandiol of Lb. bulgaricus isolates were specified respectively as 0.2 +/- 0.0-57.0 +/- 1.0 mg/kg, 0.1 +/- 0.0-3.2 +/- 1.0 mg/kg, 0.1 +/- 0.1-77.0 +/- 2.0 mg/kg, 9.1 +/- 3.09-5.3 +/- 5.0 mg/kg and 6.2 +/- 0.2-98.4 +/- 2.0 mg/kg. Metabolites that determined quantified ranges in study, belong to subcultures of bacteria isolated from yoghurts fermented by traditional methods. These isolates have the potential to be a starter culture for commercial yogurt industry.