Variation of Volatile Compounds of Chinese Dates During Toast

Fresh ripe Tuan date，a kind of Chinese date, was gradually toasted between 25℃ and 75℃. The furnace temperature program including a step-up period from 25℃ to 50℃ within 4h, then temperature increases at 5℃/4h from 50℃to 75℃. Fresh date of 100 g and the samplings of 100 g taken every 5℃ beginning with 50℃ was soaked in 95% ethanol respectively. After distillation of ethanol the residue was extracted by using ethyl ether (3×60 mL) and dried with sodium sulfate. The volatile compounds were obtained by distillation of ethyl ether and analyzed by GC-MS. The results showed that the volatile compounds were mainly 13 esters, including ethyl palmitoleate, ethyl myristoleate, ethyl lipoleate, ethyl palmitate, ethyl oleate, ethyl laurate, and ethyl myristate, etc. The contents of those esters were decreased as the furnace temperature was increased. Otherwise, the content of 5-hydroxymethyl-2-furancarbonaldehyde, 5-hydroxyl-5,6-dihydrogen-meltol found begining with 55℃ and 2-furancarbonaldehyde found begining with 65℃ was increased as the furnace temperature was increased. 3-hydroxyl-2-on-butane, ethyl malate and ethyl decanoate are possible to contribute to fresh date smell, and 5-hydroxymethyl-2-furancarbonaldehyde, 5-hydroxyl-5,6-dihydrogen-meltol and 2-furancarbonaldehyde to the special charred smell. The dried date toasted at 65℃ was provided with best quality. The furnace temperature should not be higher than 70℃ during the toast process.