Characterization of Korean sweet potato starches: physicochemical, pasting, and digestion properties

Abstract

Physicochemical, pasting, and digestion properties of Korean sweet potato starches were investigated. Sweet potato starch granules were oval, round, polygonal, spherical, and bell-shaped and of 10.2-15.3µm in mean particle diameter. The average particle size of Jeongmi was the highest, while Daeyumi was the lowest. Amylose content of the sweet potato starches varied from 12.3 to 17.4%. Jeongmi showed the highest values for Mw (14.6ⅹ107g/mol), whereas Daeyumi had the lowest (7.2ⅹ107g/mol). A similar chain length distribution of amylopectin was found in 11 sweet potato starches. The portion of B3 (DP≥37) correlated (r=0.66, p<0.01) with the amount of leached amylose. Thermal properties of DSC showed the high values of To, Tp, and Tc in Shinyulmi and Jeongmi, but a relatively low value in Daeyumi. All sweet potato starches exhibited a characteristic Ca-type diffraction pattern. Different patterns were revealed among the swelling factors of sweet potato starches depending on temperature. The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) in sweet potato starches ranged from 9.6 to 17.4%, 31.4 to 45.6%, 35.7 to 62.8%, respectively. Shinyulmi and Happymi had the highest SDS, and Jeongmi had the highest RS. According to the Rapid visco analyzer (RVA) viscosity profiles, differences were observed in pasting parameters such as pasting temperature, peak viscosity, final viscosity and breakdown. Happymi showed the highest breakdown, and lowest final viscosity, setback, pasting time, and pasting temperature.