Composition, structure, and physicochemical properties of sweet potato starches isolated by sour liquid processing and centrifugation

The proximate composition, structure, and physicochemical properties of sweet potato starches prepared by sour liquid processing (SLPS) and centrifugation (CFS) in the laboratory, and those of commercial grade starches, were examined and compared. The total amylase activities (α‐, β‐amylase) of the sour liquid and starch supernatant were also determined. The apparent amylose, Al, Mg, Fe, and Zn contents, granule size, XRD crystalline peak intensities, gelatinization enthalpy, peak viscosity, and setback ratio of SLPS were lower than those of CFS, whereas the protein, lipid, ash, phosphorous, K, and Ca contents, L* value, swelling power (55–95°C), solubility (55–95°C) and stability ratio of SLPS were higher than those of CFS. The surfaces of SLPS granules appeared corroded, showing pits and fissures, whereas the surfaces of CFS granules appeared smooth. In addition, the total amylase activity of the starch supernatant was 150.83 units/100 mL, and reached a maximum value of 214.28 units/100 mL in the sour liquid after 4 h of fermentation.