Thursday, August 2, 2012
Grand Ballroom
Rubus fruits (raspberry and blackberry) generally contain high amounts of anthocyanins as the dominant pigment. Some yellow fruited raspberries contain little or no anthocyanin. Carotenoids are present in these fruits but only in tiny amounts. However, carotenoids may play an important role as precursors of flavor volatiles, especially the ionones. The purpose of our research was to determine the types and relative content of carotenoids in ripe fruit of cultivars and species of raspberry and blackberry. Freeze dried fruits were crushed and sieved to exclude seeds, then fruit tissue ground to a particle size of less than 40 µm. About 0.5 g dry tissue was extracted with hexane:ethanol:acetone, 6 ml of the hexane layer dried under nitrogen, and resuspended in one ml methanol. Aliquots were injected onto high performance liquid chromatography equipped with photodiode array. We found that the content of alpha carotene in red raspberry ranged from 20 to 80 and beta carotene ranged from 40 to 160 µg/g dw. In black raspberries, the content of beta carotene was much higher, exceeding 200 µg/g dwt. Yellow, pink, or red/yellow raspberries exhibited a range of carotenoids, with high levels of beta carotene; most of these had at least one quarter R. parvifolius. Blackberry fruit were similar in carotenoid composition to black raspberry. Seeds of either blackberry or raspberry had detectable amounts of zeaxanthin and/or lutein. Alpha tocopherol and lutein represented large amounts of total carotenoids in raspberry and blackberry fruit tissue. Our results show that the carotenoid profile of raspberry is highly variable and depends on species background as well as phenotypic fruit color. In contrast, seeds had little carotene content but were high in zeaxanthin and lutein. Overall, the contribution of tochopherols, lutein, or carotenoids in raspberry or blackberry to dietary health is small. The relative role of carotenes to raspberry flavor remains to be determined.