EFFECT OF ADDED LIPASES OF PSYCHROTROPHIC YERSINIA, ENTEROBACTER AND CITROBACTER SPP ON THE KEEPING QUALITY OF MILK AND FAT RICH MILK-PRODUCTS

Cell-free filtrates of psychrotrophic Yersinia sp. M18, Enterobacter s p. M31 and Citrobacter sp. M33 containing lipase activities were preci pitated with ammonium sulphate and the precipitates after dialysis wer e introduced separately into aseptically drawn milk, pasteurized cream , butter and ghee, and stored at 7 degrees C. A6-fold increase in FFA content in refrigerated milk containing added Yersinia lipase, and ran cidity were observed from 10th day of storage. in refrigerated milks c ontaining Enterobacter and Citrobacter lipases there was no appreciabl e increase in FFA content nor the samples exhibited rancidity even aft er 18 days of storage. Addition of Yersinia lipase to cream resulted i n 2-fold increase in oleic acid content and showed rancidity after 14 days of storage at 7 degrees C. While addition of lipases of Enterobac ter and Citrobacter through increased the oleic acid content but did n ot show rancidity even at the end of 16 days storage period. In butter . Enterobacter lipase produced highest oleic acid content followed by lipases of Citrobacter and Yersinia. But none of the ghee samples cont aining Yersinia, Enterobacter and Citrobacter lipases exhibited rancid ity during storage period nor caused an appreciable increase in oleic acid content.