Complementary to an efficacy trial carried out under the vitamin A for Africa Partnership, the retention of β-carotene in boiled, mashed orange-fleshed sweet potato (OFSP), variety Resisto, was evaluated. The OFSP contained almost exclusively trans-β-carotene. Studies were done to establish and evaluate the analytical procedure and to assess the natural variability of the β-carotene content of OFSP. Because it was more efficient than other solvents, tetrahydrofuran:methanol (1:1) was chosen for extraction. The high-performance liquid chromatographic method established showed good reproducibility. No loss of β-carotene was observed in chopped/grated raw OFSP allowed to stand for 4 h, indicating that it was not prone to enzymatic oxidation. The β-carotene content of medium-sized OFSP from the same harvest batch ranged from 132 to 194 μg/g. True retention (TR) was assessed using paired samples and a formula that compensated for loss or gain of moisture and soluble solids. TR was 92% when medium-sized OFSP covered with water was boiled for 20 min in a pot with the lid on; without the lid, boiling took 30 min and TR was 88%. When OFSP of different sizes were boiled 30 min, covered with water in a pot with the lid on, TR was 70-80%. Although degradation occurred, the β-carotene content of boiled/mashed OFSP was still substantial.
Journal of Food Composition and Analysis (2006) 19 (4) 321-329 [doi: 10.1016/j.jfca.2004.10.007]