Drying characteristics, quality changes, parameters optimization and flavor analysis for microwave vacuum drying of garlic (Allium sativum L.) slices

The influence factors such as microwave power, vacuum degree and temperature were investigated using the color L*, thiosulfinate content, rehydration ratio and comprehensive score of garlic slices as responses. The microwave vacuum drying (MVD) parameters of garlic slices were optimized by response surface methodology. The electronic nose was used to compare the flavor differences between fresh garlic and dried garlic slices. The results showed that the drying curve and rate curve of MVD garlics accorded with the drying characteristics of foods, the optimum MVD conditions of garlic slices were microwave power 260 W, vacuum degree 81 kPa, and temperature 49.5 °C. Under these conditions, the color L*, the thiosulfinate content, the rehydration ratio and the comprehensive score of garlic slices were 82.26, 3.0378 mg/100 g, 2.796 and 0.9265, respectively. The principal component analysis results of electronic nose demonstrated that there was no difference in the composition between the dried garlic slices and fresh garlic, while the linear discriminant analysis of electronic nose could distinguish them. There was no significant difference in the volatile components of dried garlic slices under different drying conditions. Therefore, MVD process could be an effective drying method and quite suitable for garlic.