Effects of Drying Temperature on Flavonoids Extraction Rate from Young Stems and Leaves of Two Cassava Varieties

To improve flavonoids resources utilization level of young cassava stems and leaves, using cassava varieties SC09 and SC205 as ob jects, investigated the effect of different drying temperatures(40~120℃)on the flavonoids extraction rate(FER)and their stability in 120 d storage period after drying, explored a right drying storage method for postharvest young cassava stems and leaves. The research showed that total FER rised first, and then fell and rised again with the increase of drying temperature. During 40~80℃, the total FER was obviously in fluenced by variety and temperature, but only temperature was main factor affecting total FER during 90~120℃. Extract degree of flavonoids include rutin, amentoflavone or catechin, kaempferol, hesperidin, quercetin minished in order; the effect of cassava variety on the extraction rate of catechin and hesperidin was greater than that of drying temperature, but that contrary to other 4 flavonoids. Variety and temperature had a maximum impact respectively on catechin and rutin extraction rates. Whereas both of variety and temperature had a minimum impact on kaempferol extraction rate. FER reached higher levels of 1.42%and 1.53% respectively in SC09 after 120℃drying and SC205 after 110℃drying, and had best stability during 120 d storage period. The extraction rate of hesperidin increased after drying storage, and that of other 5 ingredients were changing with different varieties and temperatures; the coefficient variation(CV=1.03%~6.86%)of kaempferol was minimum and its stability was best; extraction rates of rutin and kaempferol in SC205 after 110℃drying were maximum, whose increasing rates were 44.89%and 7.27%respectively with a small separate degree(CV were 6.94%, 4.59%)and good extraction stability. Maximum in creasing rates of catechin, amentoflavone, quercetin and hesperidin were 211.60%，17.60%，186.39% and 538.08% respectively. However,their stabilities of extraction efficiency were poor(CV=18.47%~50.03%)during storage. A right drying temperature after picking young cassava stems and leaves as flavonoids resource to be utilized depended on the target composition and cassava varieties