Effect of hot air, solar and sun drying treatments on provitamin A retention in orange-fleshed sweetpotato

Abstract

Different drying treatments, cross flow, greenhouse solar, and open air-sun, were applied to an American orange-fleshed sweetpotato variety. Trans- β-carotene losses in flour made from dried chips varied between 16% and 34% in all treatments. Hot air cross flow drying retained significantly more provitamin A than sun drying. Solar and sun drying were not significantly different in terms of provitamin A retention. The shape of the sweetpotato pieces (chip or crimped slice) influenced provitamin A retention during sun drying; crimped slices retained more provitamin A. Other minor provitamin A compounds in fresh sweetpotato included 13- cis- and 9- cis- β-carotene and β-carotene 5, 6 epoxide. No significant increase in the cis-isomers was observed after drying. Vitamin A activity in flours was found to be greater than 1,500 RE ( β-carotene:retinol; 13:1) per 100 g including in sun-dried samples. Flour from orange-fleshed sweetpotato therefore has potential as a significant source of provitamin A.