Effect of starch isolation methods and ecotype on powder flowability, pasting, and thermal properties of Ethiopian potato (Plectranthus edulis) starch

Abstract : This study examined the impact of three isolation media—distilled water (DW), sodium chloride (NaCl), and sodium metabisulfite (SMS)—on starch extracted from two Ethiopian potato (EP) varieties, Chanqua and Loffo. Significant variations (P≤0.05) were observed across isolation methods and varieties. SEM revealed mostly spherical to elliptical starch granules, regardless of method. Flow properties showed porosity ranged from 27.16%–40.72%, HR from 1.04–1.20, CI from 4.11%–17.25%, and angle of repose from 23.00°–36.33°, indicating good flowability. Pasting analysis revealed CNaCl starch had the highest peak viscosity (8979.02 mPa.s) and final viscosity (5936.03 mPa.s), while Loffo starch had higher trough viscosity, enhancing paste stability. Thermal analysis showed onset, peak, and conclusion temperatures ranging from 65.20–68.80 °C, 68.06–73.91 °C, and 80.06–84.14 °C, respectively. LSMS exhibited the highest gelatinization enthalpy (7.59 J/g), indicating better thermal stability. SMS was the most effective medium, yielding starch with superior flow, thermal, and pasting characteristics • Starch from two Ethiopian potato varieties (Chanqua and Loffo) was isolated using DW, NaCl, and SMS, showing significant differences in physicochemical and functional properties. • SMS-isolated starches exhibited superior flowability, thermal stability, and higher gelatinization enthalpy, suggesting stronger crystalline structure and cooking performance. • SEM revealed similar granule morphology (spherical to elliptical) across isolation methods, while flow properties and pasting behavior showed significant variation. • Loffo starches showed higher trough viscosity and stability; CNaCl starch had the highest peak and final viscosity, indicating excellent thickening potential.