龙眼高温热泵干制过程中主要活性成分变化研究

Changes of Main Active Compounds of Longan During High Temperature Heat Pump Drying Process

以干燥过程中龙眼酚类物质及多糖为研究对象,考察其含量和抗氧化活性在热泵干燥过程中的变化规律。结果表明,干燥过程中,龙眼游离酚、总酚和多糖的含量显著下降,分别下降了27.61%、23.94%和73.17%。结合酚含量显著升高,升高了111.11%。指数衰减模型能有效地拟合干燥过程中龙眼游离酚、总酚和多糖的含量变化曲线,S曲线则更适合于描述结合酚含量的变化规律。龙眼游离酚、结合酚和多糖的DPPH自由基清除能力在干燥过程中分别呈现下降、上升和下降的趋势。其中多糖的DPPH自由基清除能力的下降主要集中在干燥24 h和30 h之间。干燥过程中,龙眼中游离酚、结合酚、总酚及多糖的含量与其对应的抗氧化性均呈显著正相关。

Changes of the contents of phenolic compound and polysaccharide of longan, as well as the corresponding antioxidant activities, were investigated during the high temperature heat pump drying process. Results showed that the contents of free phenolic compounds, total phenolic compounds and polysaccharide declined during the drying process, reaching 27.61%, 23.94% and 73.17% of the initial value, respectively. The contents of bound phenolic compounds gradually increased to 111.11% of the content before drying. Exponential decay model was the best fitting kinetics model for changes of the contents of free phenolic compound, total phenolic compound and polysaccharides, while S curve model was more suitable for the changes of the contents of bound phenolic compounds. During the drying process, the changing trends of DPPH free radical scavenging capacity of free phenolic compounds, bound phenolic compounds and polysaccharide were decreasing, increasing and decreasing, respectively. The major changes of the DPPH free radical scavenging capacity of polysaccharide appeared between the drying time of 24 h and 30 h. There were positive correlations between the contents of free phenolic compounds, bound phenolic coumpounds, total phenolic compounds, polysaccharide and the corresponding antioxidant activities in the drying process.