Margarine Fat Analogs Through Interesterification Of Soybean Oil And Fully Hydrogenated Palm Oil

Special oil such as margarine had occupied a large market with the development of economy in China. The first margarines were made from animal fats, but today most margarines are formulated from vegetable oils. Most native fats and oils have limited applications due to their regio-chemical and stereo-chemical structures. So several technologies have been developed to modify them. Interesterification changes the position of the fatty acids and rearrangement the fatty acids on the glycerol backbone. This rearrangement modifies solid-to-liquid ratio of the fats to produce various kinds of plastic fats free of trans fatty acids. Soybean oil has gained an excellent reputation for its nutritional qualities, permanent supply, considerable economic value and high functionality. This research studied the chemical and enzymatic interesterification of soybean oil with fully hydrogenated palm oil for trans-free margarine fat analogs. The results are as follows.(1) High temperature gas chromatograph was employed to investigate the degree of interesterification. The reaction conditions using Lipozyme 435 as the catalyst was optimized by single factor experiments, giving the following optimum conditions: reaction temperature 90 °C, reaction time 4 h, enzyme dosage 4 wt%(of the total oil mass), and the mass ratio of soybean oil to fully hydrogenated palm oil 4:3. Under these conditions, the rate of random interesterification was 98.3%.(2) Box–Behnken statistical design of response surface methodology(RSM) was used to statistically optimize the reaction parameters and evaluate the effects of multiple variables. Temperature was the most significant single parameter which followed by the enzyme dosage and reaction time. The optimal conditions for enzymatic interesterfication were obtained by response surface methodology as follows: reaction temperature 95 °C,reaction time 4 h, enzyme dosage 4.29 wt%(based on the masses of the total oil).(3) The original and interesterified blends were examined for triacylglycerol composition, melting point, solid fat content(SFC), crystal structure and microstructure. Interesterification changed the position of the fatty acids and rearranged the fatty acids on the glycerol backbone, which caused the reduction of trisaturated triacylglycerol content and increase in monounsaturated and diunsaturated triacylglycerols. Compared with the original blends, the enzymatic interesterified products(EIP) displayed lowering of respective melting points(29.1~48.8 °C), reduced SFC value and β′ form prime. The EIP showed needle ball-like crystals and the sizes of crystals were about 10~25 μm in diameter. Besides, the EIP contained 9.6% SFC at high temperature(40 °C) to aid in structural formation of cake. So the EIP had the potential application as bakery margarine.(4)The reseach investigated the isothermal crystallization of interesterified blends under 30 °C, 35 °C, 38 °C by the methods of DSC. Isothermal DSC data was used to assess the kinetic parameters using Avrami equation. The results indicated that Avrami exponent of 2 represented plate-like growth and k decreased following the increase in the preset temperature.(5)Soybean oil and fully hydrogenated palm oil were catalyzed by sodium hydroxide and glycerol to obtain monoacylglycerol and margarine fat analogs. Under the optimization conditions, the results were as follows: content of 23.9% MAG was obtained in the acylglycerols mixture; the yield of DAG and TAG was 72.7%.