干燥方式对辣木叶营养活性成分、抗氧化活性及色泽的影响

Effects of Drying Methods on Bioactive Components, Antioxidant Capacity and Color of the Leaves of Moringa oleifera Lam.

以辣木叶为研究对象,考察热风干燥、真空微波干燥及真空冷冻干燥等脱水方式对辣木叶营养活性成分、抗氧化活性及色泽的影响。结果表明,不同干燥方法均会引起辣木叶酚类物质、维生素C、异硫氰酸酯、多糖类物质等营养活性成分的损失,以及色泽的劣变和叶绿素的降解,并造成美拉德反应产物5-羟甲基糠醛(5-hmf)的累积。然而,通过真空微波干燥和冷冻干燥能有效避免辣木叶氧自由基清除能力的下降。不同的干燥方式各有利弊。其中冷冻干燥能较好地保持辣木叶中的维生素C、叶绿素,真空微波干燥能较好地减少酚类物质、多糖类物质等活性成分和抗氧化活性的损失并减少5-hmf的累积。对于热风干燥,热风温度对辣木叶品质的影响显著,适宜的温度有助于γ-氨基丁酸、异硫氰酸酯、多糖类物质等活性成分的保留。综合考虑干燥方式对辣木叶品质的影响及干燥效率,选择真空微波干燥作为最适宜的辣木叶干燥方式。

The effects of hot air drying (HAD),vacuum microwave drying (VMD)and freeze drying (FD)on bioactive components,antioxidant capacity and color of the leaves of Moringa oleifera Lam.were investigated.Results showed that all drying methods led to the loss of bioactive components including phenolic compounds,vitamin C,isothiocyanates and polysaccharides.In addition,the deterioration of color,degradation of chlorophyll and accumulation of the Maillard reaction products of 5-hydroxymethylfurfural (5-hmf)were also observed in the samples treated by different drying methods.However,the oxygen radical absorbance capacity of the leaves treated by VMD and FD were well maintained.Each drying method showed different advantages and disadvantages.FD preserved the vitamin C and chlorophyll of Moringa leaves effectively.MVD was effective in reducing the loss of phenolic compounds,polysaccharides and antioxidant capacity.MVD also resulted in less accumulation of 5-hmf.As for HAD treated samples,drying temperature displayed significant influences on the quality of the leaves.Suitable temperature helped to retain the contents of bioactive components including γ-amino butyric acid (GABA),isothiocyanates and polysaccharides.Consideration the effects on quality of Moringa leaves and the drying efficiency,MVD is recommended as a viable option to produce high quality dried leaves of Moringa oleifera Lam.