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Three strains of lactic acid bacteria were isolated from fish and shrimp pickles. Two strains were identified as Lactobacillus casei, and one strain as L. pentosus, respectively. All three strains were used as starters in producing yogurts. The physico-chemical characteristics of yogurts were examined. The original pH, titratable acidity, visicosity and viable cell counts of the yogurts were 4.03∼4.26, 1.049∼1.217%, 1,772∼2,232 cps and 1.4×10^9∼1.6×10^9 cfu/㎖, respectively. In evaluating buffer capacity, 12.50∼14.06 ㎖ 1.0N HCl was consumed to titrate 100 ㎖ of yogurt to pH value 2 units below the original pH value and 9.46∼13.06 ㎖ of 1.0N NaOH was consumed to pH value 4 units above the original pH value. The β-glactosidase activity reached maximum at 48 hrs, and reduced gradually during fermantation. After 2 hr incubation of yogurts at 37℃ under different pH conditions, β-glactosidase activities of three strains were reduced to 50% at pH 3.5, but there were no remaining activities neither at pH 2.5 nor at pH 1.5. Under the same pH conditions the number of viable cells decreased to 1.9×10^6∼1.8×10^8 cfu/㎖ at pH 2.5 and 1.0×10³∼2.4×10^5 at pH 1.5, respectively. However, no significant difference was found at pH 3.5.
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