干燥方式对红枣动力学及挥发性成分的影响

Effect of drying method on kinetics and volatile components of red date

摘要:

采用热风干燥、真空冷冻干燥和微波真空干燥对红枣进行干燥处理，结合顶空固相微萃取-气相色谱-质谱（headspace solid-phase microextraction-gas chromatography-mass spectrometry，HS-SPME-GC-MS）和电子鼻对枣片挥发性成分进行了分析，并对比了3种干燥方式对红枣色泽、动力学和挥发性成分的影响。结果表明，热风干燥和微波真空干燥对枣片色泽影响较大，真空冷冻干燥能够更好的保持原始色泽；对动力学方程进行拟合，发现Page 模型为预测红枣3种干燥方式干燥特性最适合的数学模型；干燥对枣片挥发性成分种类及相对含量差异显著，其中干燥前后相同的挥发性成分有19种。挥发性物质主要有酸类、酯类、醇类、醛类、酮类、烃类、杂环类和其他化合物，干燥过后枣片中酸类和烷烃类挥发性成分相对含量显著增加，醛类和杂环类物质显著降低。电子鼻结果表明干燥后枣片香气特征与新鲜红枣有较大的区别，热风干燥和微波真空干燥香味特征较为接近，微波真空干燥枣片的焦甜香特征更为明显。相较于热风干燥和真空冷冻干燥，微波真空干燥效率较高、能耗较低、周期较短，更适于制备干燥枣片。

Abstract:

Drying red dates through hot air drying, vacuum freeze drying and microwave vacuum drying, the volatile components of date slices were analyzed using headspace solid-phase microextraction-gas chromatography-mass spectrometry and electronic nose, and the effects of the three drying methods on the color, kinetics and volatile components of date slices were compared. The experimental results showed that hot air drying and microwave vacuum drying have greater influence on the color of date slices, and vacuum freeze drying can better maintain the original color; by fitting the kinetic equations, the Page model was found to be the most suitable mathematical model for predicting the drying characteristics of the three drying methods of date slices; significant differences in the types and relative contents of volatile components of date slices by drying, there were a total of 19 volatile components that were identical in date slices before and after drying. The volatile substances mainly included acids, esters, alcohols, aldehydes, ketones, hydrocarbons, heterocyclic substances and other compounds, and the relative contents of volatile components of acids and alkanes in date slices increased significantly after drying, while aldehydes and heterocyclic substances decreased significantly. The electronic nose results showed that the aroma characteristics of the dried date slices were different from those of fresh red date, and the aroma characteristics of hot air drying and microwave vacuum drying were closer and caramel aroma characteristics of date slices dried by microwave vacuum was more prominent. Compared with hot air drying and vacuum freeze drying, microwave vacuum drying is more suitable for preparing dried date slices because of its higher efficiency, lower energy consumption and less time consuming.