The effects of different drying methods on essential oils and flavonoids from orange peels

The effects of different drying methods(sun drying,shade drying,hot air drying,vacuum drying)on the content and compositions of essential oils and flavonoids of orange peel were studied. The results showed that the highest essential oil yields were obtained by hot air drying(2.11%),followed by sun drying(1.91%),vacuum drying(1.95%),shade drying(1.65%). Twenty-three different components were identified in essential oils of fresh and dried orange peels and the main component was D-limonene. All those volatiles components were clustered into the following families:terpenes,alcohols,aldehydes,phenols,ethers and benzene. The content of flavonoids in orange peels decreased after drying. The highest content of flavonoids was dried by shade,followed by hot air drying,which were 15.73 mg/g and 15.49 mg/g,respectively. By comprehensive comparison of the four drying methods,the time of hot air drying was shortest and not affected by the weather easily. Meanwhile,the essential oils and flavonoids dried by hot air drying was relatively high,which would more suitable for orange peels drying.