Effect of flour processing on the proximate composition, polyphenolic content, and antioxidant activity of 19 Philippine sweet potato cultivars

Abstract

Nineteen sweet potato cultivars (white-, yellow-, and purple-fleshed) were investigated for the effects of flour processing on their proximate and mineral composition, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities in terms of oxygen radical absorbance capacity (ORAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Significant (p < .05) variations for all parameters were observed among the cultivars. Flour processing also significantly affected these properties but varied depending on the cultivar. Contributions of phenolics and flavonoids to the antioxidant activities of sweet potato were indicated by the strong positive correlations among TPC, TFC, ORAC, and DPPH assays. Flour produced from the purple-fleshed cultivar (SG-08-09-11) consistently exhibited the highest value in terms of TPC (128.03 mg GAE/100 g), TFC (95.04 mg CE/100 g), ORAC (4099.37 μmol Trolox/100 g), and DPPH (10302.74 μmol TE/100 g). It also exhibited the highest dry matter assuring high flour yields, hence, it can be recommended as an alternative flour source with health benefits. Practical applications The increasing demand for major flours and the growing interest for functional foods drive the need to tap alternative sources of flour ingredients with health benefits. Several positive attributes of sweet potatoes including its low cost and high nutritional value make it a good alternative source of flour; however, flour processing affects its nutritional and bioactive compounds and antioxidant activities. Characterization of sweet potato cultivars and its flours in terms of these parameters will help determine superior cultivars for flour processing with the highest nutritional capacity. This study will also aid farmers and breeders in developing suitable breeding programs for less superior cultivars. In addition, this will add information to the limited knowledge of Philippine sweet potato cultivars.