干燥方式对红枣片动力学及挥发性成分的影响

Effect of drying methods on kinetics and volatile components of red jujube slices

采用热风干燥(HAD)、真空冷冻干燥(VFD)和微波真空干燥(MVD)对红枣片进行干燥处理,结合顶空固相微萃取-气相色谱-质谱(HS-SPME-GC-MS)和电子鼻对红枣片挥发性成分进行了分析,并对比了3种干燥方式对红枣片色泽、动力学和挥发性成分的影响。结果表明,HAD和MVD对红枣片色泽影响较大,VFD能够更好地保持原始色泽;Page模型为预测红枣片3种干燥方式干燥特性最适合的数学模型;干燥对红枣片挥发性成分种类及相对含量影响显著,其中干燥前后相同的挥发性成分有20种。挥发性物质主要有酸类、酯类、醇类、醛类、酮类、烃类、杂环类和其他类化合物,干燥过后红枣片中酸类和烃类挥发性成分相对含量显著增加,醛类和杂环类物质相对含量显著降低。干燥后红枣片香气特征与新鲜红枣片有较大的区别,HAD样品和MVD样品香味特征较为接近,MVD样品的焦甜香特征更为明显。MVD干燥效率较高、能耗较低、周期较短,更适于制备干燥红枣片。

Red jujube slices were dried through hot air drying(HAD), vacuum freeze drying(VFD) and microwave vacuum drying(MVD). The volatile components of red jujube slices were then analyzed using headspace solid-phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS) and electronic nose, followed by investigation on the effects of drying methods on the color, kinetics and volatile components of dry jujube slices. The results showed that HAD and MVD displayed greater effect on the color of red jujube slices, while VFD better maintained the original color. Page model was found to be the most suitable mathematical model for predicting the drying characteristics of three drying methods.Drying also showed significant influence on the types and relative contents of volatile components in red jujube slices. A total of 20 volatile components, including acids, esters, alcohols, aldehydes, ketones,hydrocarbons, heterocyclic substances and other compounds, were identical in red jujube slices before and after drying, while the relative contents of acids and hydrocarbons increased significantly after drying, and aldehydes and heterocyclic substances decreased significantly. Meanwhile, the aroma characteristics of the dried red jujube slices were different from those of fresh, with similar aroma characteristics between HAD and MVD, and a more prominent caramel aroma of red jujube slices dried by MVD. Compared with HAD and VFD, MVD exhibited higher drying efficiency, lower energy consumption and less time consuming,thus more suitable for red jujube slices drying.