Flavor volatiles and physical properties of vacuum-microwave- and air-dried sweet basil (Ocimum basilicum L.)

Basil (Ocimum basilicum L.) was dried using conventional hot air or the rec ently developed vacuum-microwave dryers. The effect of the drying method on the relative abundance of major flavor volatiles, rehydration rate, color, and structural integrity of the plant was evaluated. Dynamic headspace ana lysis of volatiles present in fresh or dried basil revealed that linalool a nd methylchavicol (estragole) were the two major headspace volatile compoun ds of the plant sample. Vacuum-microwave dehydrated basil yielded approxima tely 2.5 times the linalool and 1.5 times the methylchavicol of the air-dri ed samples. Furthermore, the vacuum-microwave-treated samples yielded more volatiles than fresh basil, due to chemical reactions during drying. Air-dr ied samples of basil had darker and fewer green hues than those prepared by vacuum microwave. Vacuum-microwave-dried samples had a higher rehydration rate, whereas the potential of the plant material to rehydrate was hindered in air-dried samples. This is likely attributed to the dramatic and pronou nced structural collapse of the air-dried cells as revealed by the scanning electron microscope.