Chemical compositions, bioactive compounds, and physicochemical properties of different purple sweet potato flours

Abstract

The difference in growing conditions, cultivated techniques or genotypes resulted in various quality of purple sweet potatoes. The objective of this study was to determine chemical compositions, bioactive compounds (total anthocyanin content, total phenolic content and total flavonoid content) and physicochemical properties (swelling index, water solubility index, and pasting properties) of flours prepared from purple sweet potatoes grown at 5 villages in Dong Thap and Vinh Long provinces. In term of dry basis, the chemical compositions of different purple sweet potato flours consisted of 1.08-3.09% of protein, 0.17-0.41% of lipid, 2.49-2.78% of ash, and 93.94-95.92% of total carbohydrate. Purple sweet potato grown at Phu Long village (Chau Thanh district, Dong Thap province) had the highest total anthocyanin content (6.8 mg cyanidin-3-glucoside/100 g flour (dry basis, db)), total phenolic content (202.2 mg FAE/100 g flour (db)), total flavonoid content (85.6 mg RE/100 g flour (db)) and water solubility index (13.6%) as compared to other purple sweet potato flours. Nevertheless, the paste of purple sweet potato from Hoa Tan village (Chau Thanh district, Dong Thap province) had the highest swelling index (7.5 g water/g flour) and manifested the greatest resistance against retrogradation, gel consistency and hot paste stability among other flours. The results of this study provided the useful information about the quality of purple sweet potatoes grown at different locations.