干燥方式对香芋片挥发性物质的影响

Effects of different drying methods on volatile substances of taro slices

目的:提高香芋片干燥技术及提取效率。方法:采用水蒸气蒸馏法及气相色谱—质谱联用技术,对比热风干燥(HAD)、直触超声强化热风干燥(CU-HAD)、远红外辐射干燥(FIRD)、直触超声强化远红外辐射干燥(CU-FIRD)和冷冻干燥(FD)香芋片的挥发性成分组成及特征差异,并进行主成分分析。结果:干燥前及不同干燥方式加工后的香芋片共检测出149种挥发性成分,其中烷烃类54种、酯类20种、苯环类16种、醇类12种、酮类11种、烯烃类11种、醛类8种、酸类4种、其他类化合物13种。不同干燥方式处理的香芋片挥发性成分以苯环类、酯类为主。以HAD处理的香芋片挥发性成分最少,仅有42种,FIRD次之,以CU-HAD处理的香芋片虽然挥发性成分较多,但多数为烃类化合物,对香芋风味贡献值较小,以CU-FIRD和FD处理的香芋片的整体成分较接近,但CU-FIRD耗时最短,结合主成分分析得出CU-FIRD对香芋片挥发性成分的保留与加工效果最好。结论:将直触超声技术和远红外辐射加热联合应用对香芋风味的保护作用要好于单一超声和单一远红外辐射的效果。

Objective: This study aimed to explore the effects of different drying methods on the volatile components of taro slices. Methods: Volatile compound composition and volatile characteristics of five different drying methods of dried taro slices were studied. Taro and the ones dried by five drying methods, i.e. hot-air drying(HAD), contact-ultrasound enhanced hot-air drying(CU-HAD), far-infrared radiation drying(FIRD), contact-ultrasound enhanced far-infrared radiation drying(CU-FIRD) and freeze drying(FD),were analyzed by gas chromatography-mass spectrometry(GC-MS) with water-vapor distillation method. Volatile components were analyzed in conjunction with principal component analysis(PCA). Results: A total of 149 volatile compounds were detected in the fresh, pretreated, and dried taro slices, including 54 kinds of alkanes, 20 kinds of esters, 18 kinds of heterocyclic groups, 12 kinds of alcohols, 11 kinds of ketones, 11 kinds of olefins, 8 kinds of aldehydes, 4 kinds of acids and 13 kinds of other compounds. Using the area normalization method, it could be concluded that the volatile components of dried taro slices with different drying methods were mainly heterocyclic compounds and esters. Taro slices treated with HAD had the least volatile components which were only 42 species, followed by the FIRD--treatments, with 46 kinds of volatile components. Although CU-HAD treated taro had more volatile components, most of them were hydrocarbons, which contributed less to the flavor of taro. Cu-FIRD and FD treated taro had similar overall components, but CU-FIRD took the shortest time. Combined with results of PCA, CU-FIRD showed the best retention and processing effect of volatile components in taro. Conclusion: The combination of direct contact ultrasound and far-infrared radiation heating had better protective effect on the flavor of taro than that of single ultrasound and single far-infrared radiation.