| Microwave assisted extraction (MAE), as a green extraction method, was employed to extract polysaccharides and lutein from pumpkin in this research. The solvent used for extraction was safety and edible, and was no pollution and harm for product.The effect of extraction temperature, time and liquid-solid ratio on polysaccharides yield was studied using single factor experiments. Based on the results of this, quadratic regression model was based to study reciprocal influence between different factors, and to determine the optimal extraction process parameters. The optimum MAE conditions for highest polysaccharides yield 16.76% were obtained with extraction temperature of 79℃, extraction time of 30min and a liquid-solid ratio of 22.50mL/g. The liquid-solid ratio is the most important factor on polysaccharides yield, followed by extraction temperature, and the extraction time is the least important.Then the highest lutein yield was 2.61mg/g, through the second MAE on remainder, which had already been first extracted for polysaccharides.Comparing to the effect of different solvent on lutein yield, absolute ethyl alcohol was the solvent for extracting lutein. Process parameters of extraction temperature, extraction time and liquid-solid ratio was studied using single factor and combination test method. The quadratic regression models were developed based to optimise processing parameter. The optimization parameters combination was obtained as 80℃of the extraction temperature, 70min of the extraction time and 24mL/g of the liquid-solid ratio. Under the optimum processing parameter, the highest lutein yield was 1.06mg/g. The effect of liquid-solid ratio on lutein yield is the most significant, followed by the extraction time, and extraction temperature is the least. And the yield second extraction for polysaccharides was 5.85% using the remainder that had been extracted for lutein.There were two technics combination methods for extraction of polysaccharides and lutein from pumpkin. One was first MAE for polysaccharides, and second MAE for lutein. The other was first MAE for lutein, and second MAE for polysaccharides. Comparing to the two methods, the yield of first MAE for polysaccharides (16.76%) was higher second MAE for polysaccharides (5.85%), and the yield of first MAE for lutein (1.06mg/g) was lower second MAE for lutein (2.61mg/g).To gain high product of polysaccharides and lutein, a resonable MAE extraction process for pumpkin was developed with the first extraction of polysaccharides, then followed by the extraction of lutein.According to the classical theory of chemical kinetics, the relationship among extration temperature, extration time and product concentration was studied. The reaction order, rate constant and activation energy that parameter of kinetics were obtained based on experimental analysis, which could express the rate of reaction system. Both of the reaction order of polysaccharides and lutein were 1. Under the temperature of 323K, 333K and 343K, the rate rate constant of MAE for polysaccharides was 0.077075, 0.088264 and 0.114828, respectively. And the activation energy for polysaccharides was 18.314kJ/mol. Under the temperature of 313K, 323K and 333K, the rate constant of MAE for lutein was 0.029814, 0.03053 and 0.034853, respectively. And the activation energy for lutein was 6.733kJ/mol. In the same temperature, the rate constant of MAE for polysaccharides was higher than that of lutein. And the activation energy of MAE for polysaccharides was higher than lutein, which shows that more energy is supplied for extration polysaccharides than lutein. The relationship between the diffusion coefficient of solute in water and temperatuer was deterimined as follow: DW×1018=0.0488-T13.781. And the relationship between the diffusion coefficient of solute in absolute ethyl alcohol and temperatuer was deterimined as follow: DA×1015=0.0258T-6.7632. |
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