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Crystallization Behavior of Diacylglycerol-Rich Oils Produced from Rapeseed Oil

Saitou, Katsuyoshi, Mitsui, Yuki, Shimizu, Masao, Kudo, Naoto, Katsuragi, Yoshihisa, Sato, Kiyotaka
journal of the American Oil Chemists' Society 2012 v.89 no.7 pp. 1231-1239
crystallization, diacylglycerols, differential scanning calorimetry, filtration, gas chromatography, microscopy, oleic acid, rapeseed oil, stearic acid, temperature
We examined the crystallization behavior of high-melting fractions in liquid oil containing high concentrations of diacylglycerols (DAG >80%) (hereafter referred to as DAG-rich oil). By differential scanning calorimetry and optical microscopy at moderate cooling rates, crystallization in the DAG-rich oil was detected at around 6 °C. It was found that the crystallization extent increased with decreasing temperatures of crystallization below 0 °C. A gas chromatographic analysis was performed on the crystallized fractions, which were separated by filtration at different periods of isothermal crystallization at 3 °C. The results indicated that at earlier crystallization periods, the concentrations of 1,3-disaturated DAG such as palmitic and stearic acid moieties (15 min) and 1,3-saturated–unsaturated mixed-acid DAG including oleic acid, palmitic, and stearic acid moieties (15 min–3 h) were predominant. However, the concentrations of 1,3-diunsaturated DAG including oleic acid moiety increased after a crystallization period of 6 h. To clarify the sequential crystallization process of DAG, we examined the binary mixing behavior of principal DAG components occurring in the rapeseed-based DAG-rich oil. It was evident that 1,3-disaturated DAG, 1,3-saturated–unsaturated mixed-acid DAG, and 1,3-diunsaturated DAG exhibited immiscible behavior. From these data, basic information on the precipitation processes in DAG-rich oils at chilled temperatures was obtained.