Moisture Sorption Isotherm and Rheological Characteristics of Ethiopian Potato ( Plectranthus edulis ) Starch and Flour

This study examines the moisture sorption isotherms and rheological properties of indigenous Ethiopian potato (EP) starch and flour to address knowledge gaps. Moisture sorption isotherms were determined at 20°C using saturated salt solutions, with equilibrium moisture content (EMC) plotted against a w . Five models (Guggenheim–Anderson–de Boer [GAB], Modified GAB, BET, Oswin, and Peleg) were applied, with BET and modified GAB best describing the sorption behavior. Rheological properties were analyzed using Bingham plastic, power‐law, Herschel–Bulkley, Robertson–Stiff, and Prandtl–Eyring models. The power‐law model best fit starch, while Prandtl–Eyring was optimal for flour. Both exhibited pseudoplastic behavior, with flow index ( n ) values below 1. Dynamic frequency sweep tests showed that storage modulus ( G ′) exceeded loss modulus ( G ″), indicating elasticity. The complex viscosity ( ƞ ∗ ) decreased with angular frequency and was lower in starch (289.92 Pa.s) than flour (346.24 Pa.s). Tan δ values (0.13 for starch, 0.18 for flour) suggested stronger elastic behavior. This study demonstrates that EP starch and flour exhibit good moisture stability and favorable rheological properties, supporting their use in food processing like thickening, gelling, and gluten‐free food products.