EFFECT OF INCUBATION TEMPERATURE ON ACID AND FLAVOR PRODUCTION IN MILK BY LACTIC ACID BACTERIA1

The effect of incubation temperature on acid and flavor production by 8 lactic starter cultures was studied. Higher titratable acidity was produced at 22 than at 30 C by Streptococcus cremoris, while a reverse trend was observed with Streptococcus diacetilactis. With Streptococcus thermophilus, Lactobacillus casei, and Lactobacillus helveticus, increasing the incubation temperature from 37 to 42 C retarded acid production by 8.54, 31.8, and 37.4%, respectively. Volatile acidity increased at higher incubation temperatures in some cultures, while in others, a significant decrease was observed. Higher diacetyl production was noted when S. diacetilactis was incubated at 22 C, as compared to 30 C, while the reverse occurred with S. thermophilus. Acetoin production by S. diacetilactis was enhanced 7-fold by increasing the incubation temperature from 22 to 30 C. No significant difference was noted in proteolytic activity of all cultures, regardless of incubation temperature.