Influence of Pre-drying and Drying Treatments on the Physicochemical and Functional Properties of Purple Sweet Potato Flour

The study was conducted to determine the effects of pre-drying and drying treatments on purple sweet potato flour's physicochemical, functional, antioxidant activity, and phytochemical components (PSPF). The flours were prepared from purple-fleshed sweet potato slices soaked in water, 1% citric acid solution, and steamed for 15 min before drying. The steaming process increased the antioxidant activity of raw purple-fleshed sweet potato roots by 28.56% and produced PSPF with intense color attributes, an almost neutral pH, the highest total soluble solid content, highest water absorption index, water-soluble index, swelling capacity, gelation capacity, and antioxidant activity but lowest fat absorption capacity values compared to other pre-drying treatments. pH was lowest, and total phenolic, flavonoid, and anthocyanidin contents were highest in samples soaked in 1% citric acid solution before drying. Based on b*/a* ratios, all flours were red dominant and were more peonidin rich. Therefore, the best quality flour was produced when sweet potato slices were steamed before drying.