SELECTIVE DISTRIBUTION OF SATURATED FATTY-ACIDS INTO THE MONOGLYCERIDE FRACTION DURING ENZYMATIC GLYCEROLYSIS

Four triglyceride fats and oils (beef tallow, lard, rapeseed oil and soybean oil) were reacted with glycerol while using lipase as the catalyst. For all fats examined, at reaction temperatures above the critical temperature (T(c)), the fatty acid compositions of the monoglyceride (MG) and diglyceride (DG) fractions and of the original fat were similar. A relatively low yield of MG was obtained (20-30 wt%). When the reaction was carried out with beef tallow or lard at a temperature below the T(c) (40-degrees-C), the concentration of saturated fatty acids in the MG fraction was 2 to 4 times greater than that in the DG fraction. Correspondingly, the concentration of unsaturated fatty acids in the DG fraction was more than two times greater than that in the MG fraction. At 5-degrees-C, a similar trend was observed for rapeseed oil and soybean oil. Direct analysis of partial glycerides during glycerolysis by high-temperature gas-liquid chromatography showed that below T(c) the content of C16 MG increased relatively more than C18 MG. C36 DG and C54 TG were apparently resistant to glycerolysis. Preferential distribution of saturated fatty acids into the MG fraction was accompanied by a high yield of monoglyceride (45-70 wt%) and solidification of the reaction mixture. It is concluded that during glycerolysis below T(c), preferential crystallization occurs for MGs that contain a saturated fatty acid.