酶法制备甘油二酯与甘油三酯的结晶特性研究

Crystallization behaviors of diacylglycerol and triacylglycerol prepared by enzymatic catalysis

采用Lipozyme RM IM催化大豆油和棕榈油硬脂(熔点45℃)混合油与单甘酯(由大豆油、棕榈油硬脂和甘油合成)酯交换合成甘油二酯,并以此酶催化大豆油和棕榈油硬脂(熔点45℃)酯交换合成甘油三酯。采用差示扫描量热仪、脉冲核磁共振仪和偏光显微镜测定甘油二酯、甘油三酯以及甘油三酯中添加不同比例甘油二酯(10%、30%、50%和70%)的混合物的结晶和熔化性质。结果表明:脂肪酸组成接近的甘油二酯,初始结晶温度(28.14℃)和熔点(48.26℃)比甘油三酯初始结晶温度(8.51℃)和熔点(30.58℃)高。添加50%和70%的甘油二酯能够提高甘油三酯的熔点和初始结晶温度,而添加10%和30%的甘油二酯对其结晶影响较小。随着甘油二酯添加比例的增大,混合物的固体脂肪含量逐渐增加。添加50%和70%甘油二酯的混合物,在熔点温度附近时晶体为针状。

Lipozyme RM IM was used as catalyst in the synthesis of diacylglycerol （DAG） by the transes- terification of soybean oil mixed with palm stearin （ melting point 45 ℃ ） and monoacylglycerol （ MAG, prepared by soybean oil, palm stearin and glycerol）, and in the synthesis of triacylglycerol （TAG） by the transesterification of soybean oil and palm stearin. Crystallization and melting behaviors of the DAG, TAG and TAG added with different proportions （ 10% ,30% ,50% and 70% ） of DAG were determined by differential scanning calorimetry （DSC）, pulsed -nuclear magnetic resonance （pNMR） and polarized microscopy. The results showed that with similar fatty acid compositions, the initial crystallization temper- ature （ 28.14 ℃ ） and melting point （48.26 ℃ ） of DAG was higher than the initial crystallization tempera- ture （8.51 ℃ ） and melting point （ 30.58 ℃ ） of TAG. By adding 50% and 70% of DAG, the melting point and initial crystallization temperature of TAG increased. In comparison, adding 10% and 30% of DAG had less impact on the crystallization of TAG. The solid fat content of the mixture gradually improved with the increase DAG. Acicular crystals with 50% and 70% of melting points. of addition proportion of in the mixtures added DAG were found near