Abstract: Fresh okra fruit harvested at different growth stages were subjected to hot-air drying after fixation (SHD), hot-air drying (HD), natural drying (ND) and freeze drying (FD), separately. The effects of these drying methods on the contents of ash, moisture, amino acids and volatile substances in dried products were investigated. The results showed that the moisture content of okra was relatively low after SHD and HD. But FD had less effect on flavonoids as compared with other drying methods. Dimethyl sulfide was the characteristic volatile substance of fresh okra. It was found that the four drying treatments could contribute to increased number of volatile substances to different extents and also result in changes in the relative contents of volatile substances including dimethyl sulfide. The most abundant volatile substances were alcohols and aldehydes after SHD, while the relative contents of alcohols were higher after ND. The relative content of aldehydes was higher after FD and HD. These findings suggested that the characteristic volatile substances of fresh okra fruit were retained, and at the same time new volatile substances appeared after all drying treatments. Combinations of these substances in different proportions imparted distinct aromas to okra fruit dried by?different drying methods.

Key words: okra, growth stages, drying methods, volatile substances