The effects of traditional preparation methods and drying procedures on the provitamin A carotenoid content of orange-fleshed sweet
potato (OFSP) roots was determined by a high-performance liquid chromatography (HPLC) method. All-trans-b-carotene was the major
provitamin A carotenoid and the mean content of seven improved OFSP cultivars ranged from 108 to 315 mg/g dry matter. The retention
of all-trans-b-carotene was 78% when OFSP were boiled in water for 20 min. When OFSP were steamed for 30 min the retention was
77%, whereas deep-frying OFSP roots for 10 min resulted in retention levels of 78%. Drying slices of OFSP roots at 57 1C in a forced-air
oven for 10 h reduced the all-trans-b-carotene content by 12%. Solar drying and open-air sun drying OFSP slices to a moisture content of
p10% resulted in all-trans-b-carotene losses of 9% and 16%, respectively. The cis-isomer 13-cis-b-carotene was found in noticeable
amounts in all processed samples, but not in any raw samples. The formation of 13-cis-b-carotene correlated with the original amount of
all-trans-b-carotene found in the raw OFSP root. The high content of all-trans-b-carotene in the investigated improved OFSP varieties
and the moderately low losses due to degradation and isomerization renders OFSP a suitable food source of provitamin A.
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