Crystallization Behaviors Of Diacylglycerol Prepared By Enzymatic Catalysis

Diacylglycerol is a kind of functional oil that can suppress the accumulation of body fat, decrease the concentration of TAG in serum and reduce postprandial blood glucose.In this thesis, DAG was prepared by different methods. The crystallization behaviors of these DAG products were investigated and their potential applications in food industry were discussed. The main results are as follows.Lipozyme RM IM was employed to catalyze the synthesis of DAG using soybean oil, palm stearin(45 ℃) and MAG(prepared by the glycerolysis of soybean oil, palm stearin and glycerol). The enzyme was also used to catalyze the preparation of TAG by the interesterification of soybean oil and palm stearin. Purified MAG, DAG and TAG were obtained by molecular distillation(MD). Crystallization and melting properties of the blends of TAG and DAG with different concentrations(1%, 5%, 10%, 20% and 40%,w/w), and of the TAG and MAG with different concentrations(0.1%, 0.5%, 1%, 2%,w/w) were investigated by DSC、pNMR and XRD. Results showed that the addition of2% MAG had a slight promotion effect on the crystallization of TAG. Low concentration of DAG was found to delay the nucleation and crystal growth of TAG, but high concentrations of DAG promoted it and enhanced the formation of β’ crystal form in the blends. Therefore the plastic fat(contained DAG) possessed good processing properties.Lipozyme TL IM was used to catalyze the interesterification of soybean oil and monostearin to prepare DAG. The crude product was purified to obtain the heavy phase which consisted of DAG(over 20%) and TAG, and the light phase which had different iodine value compared with monostearin. The crystallization properties of the heavy phase was investigated and these results indicated that the heavy phase was suitable for the base oil in fluid margarine.Lipozyme 435 was used to catalyze the esterification of stearic acid and glycerol to produce DAG. To obtain a purity of 80%, the esterified products were further purified by MD. The melting point of the purified DAG was around 63 °C. XRD results revealed thatcrystals were composed of β ’and β type while the former was the main crystalline form.Therefore, the DAG prepared by this method could be applied in cocoa butter and baking shortenings production.