Effects of different heat treatments of milk on some growth characteristics of mixed and single cell cultures of yoghurt bacteria

In this study, the growth characteristics of mixed and single cell cultures of yoghurt bacteria in milk heated at 2 different temperatures (85 degrees C for 15 min and 95 degrees C for 5 min) were determined. Raising of the heating temperature from 85 to 95 degrees C caused clear increases of acetaldehyde contents of the samples prepared with both culture groups. However, considerable decreases were observed in total volatile fatty acids and tyrosine contents of the samples. Increases in the heating temperatures from 85 to 95 degrees C did no show any distinct influence on total counts of yoghurt bacteria, but increased the counts of L. delbrueckii subsp. bulgaricus in both culture groups.