The Effect of Different Starter Cultures and Dextrose on Viability of Lactic Acid Bacteria and pH of Fermented Milk At 43 °C

Abstract The purpose of this research was to study the effect of different starter cultures and the addition of dextrose on viability of LAB and pH value of fermented milk. Streptococcus thermophilus and Lactobacillus bulgaricus, Streptococcus thermophilus and Lactobacillus plantarum IS-10506 were used as mixed starter cultures, incubated at 43°C for 8 hours, with or without the addition of dextrose. The total viable counts of LAB and pH value were assessed. Each combination of starter cultures showed significant increased on the viable counts of LAB, and decreased the pH value of fermented milk during 8 hours incubation. Addition of 2% dextrose tended to increase viable counts of LAB by 165.8 % of milk fermented with mixed starter cultures of S. thermophilus and L. plantarum IS-10506, extending log phase from 6 to 8 hours, while without 2 % dextrose tended to decreased by 40 %. No significant effect of addition of 2% dextrose on viable counts of yogurt starters in yogurt. Mixed starter cultures of S. thermophilus and L. plantarum IS-10506 is potential starter cultures of fermented milk with addition of 2 % dextrose at 43°C for 8 hours incubation time to produce probiotic based functional drink.