Effect of different drying sorts on the hydration and antioxidant properties of purple sweet potato flours

Influence of hot air drying, freeze drying, microwave drying and spray drying on hydration and antioxidant properties of purple sweet potato flours (PSPFs) was studied using a commercial cultivar of PSP (wanzhi 56) as a raw material. Compared with other drying methods, PSPFs prepared with freeze drying exhibited the highest water binding and water reabsorbing capacity, but the lowest solubility. Drying treatment caused an decrease (27.64%⁵2.66%) in the anthocyanins content of PSP. PSPFs prepared by freeze drying and spry drying exhibited a highest retention rate of total anthocyanins, and significant higher than the other drying methods (p<0.05) . The highest DPPH radical scavenging activity and reducing power was found in PSPFs prepared by spry drying. In addition, the lipid peroxidation inhibition activity was highest in PSPFs prepared by freeze drying.