[Thermal inactivation of milk lipoprotein lipase]. / Teplovaia inaktivatsiia lipoproteidlipazy moloka.

The kinetics of thermal inactivation of cow's milk lipoprotein lipase (LPL) was studied. LPL inactivation can be described by the first order q equation. Thermodynamic parameters of LPL inactivation were calculated. In the range of physiological temperatures LPL existed as two conformers. The temperature of conformation conversion was 41.5 degrees C. Glycerol increased thermal stability of milk, whereas water dilution of milk, pH shift to the acid or alkaline zone, and glycine addition to milk decreased it. It is suggested that casein micellae stabilize milk LPL.

[Lipolytic activity of microorganisms isolated from different sources]. / Lipoliticheskaia aktivnost' mikroorganizmov bydelennykh iz razlichnykh istochnikov.

From different natural sources (samples of raw and pasteurized milk, fresh and melted butter, cheese, industrial and nonindustrial sewage containing fats and surface active substances) 650 microorganisms were isolated. Measurements of their lipolytic activity on milk fat (20% cream), tristearin and olive oil indicated that 27 microorganisms had no lipolytic activity on either substrate. A hundred cultures showed the highest activity. Out of them 40 most active cultures belonging to different systematic groups (fungi, yeast, bacteria) were identified as representatives of certain genera or species. Lipolytic activity varied significantly in microorganisms belonging to the same species. The use of several substrates (cream, tristearin, olive oil) helped to discriminate microorganisms that preferentially hydrolyzed either substrate.