|
Lactobacillus bulgaricus (KFCC 35463) and Kluyveromyres fragilis (KFCC 35458) were inoculated together in soymilk, and then growth characteristics, acid production and the conditions suitable for acid production were investigated. L. bulgaricus produced more acid and the rate of acid production was more rapid when this organism was incubated with K. fragilis in soymilk than when it was incubated singly. Studying the conditions suitable for acid production in soymilk, optimum acid production by the mixed cultures of L. bulgaricus and K. fragilis was achieved with a temperature of 35∼37℃, a 1:2 (O.D.660) ratio of L. bulgaricus to K. fragilis at inoculum, a 1.0% level of sucrose fortification or a 1.5% level of skim milk powder fortification and a culture time of 24hr. Under these conditions the amount of acid produced by the single culture of L. bulgaricus and the mixed cultures of L. bulgaricus and K. fragilis were 0.14% and 0.41%, respectively, in soymilk, 0.13% and 0.70%, respectively, in soymilk fortified with 1.0% level of sucrose. These indicate that the amount of acid produced by mixed cultures is about 2.9-fold greater in soymilk and about 5.4-fold greater in soymilk fortified with 1.0% level of sucrose than that produced by the single culture of L. bulgaricus. The amount of acid produced in soymilk fortified with 1.5% level of skim milk powder was 0.84% level for both of the single culture of L. bulgaricus and the mixed cultures of L. bulgaricus and K. fragilis after 24hr incubation. However, the amount of acid produced by the mixed culture with K. fragilis was greater than that produced by the single culture of L. bulgaricus onlv in soymilk fortified with lower levels of skim milk powder than 1.5%.
|