Mechanical, Powder Flow, Pasting and Morphological Properties of Indian Teff Grains and Flour as Influenced by Induced Moisture

This study investigates the physical, mechanical, flow, pasting, and morphological properties of Indian Teff (Eragrostis tef) grains and flour as influenced by varying moisture content (5%, 10%, 15%, and 20% dry basis). Two teff cultivars (TGA and TGB) exhibited significant (p ≤ 0.05) increases in principal dimensions, with length expanding from 0.95 mm to 1.12 mm (TGA) and 0.80 mm to 1.07 mm (TGB), while the geometric mean diameter increased by 23.3% and 27.1%, respectively. Bulk density decreased by 7.4% (TGA) and 10.9% (TGB), while rupture force and rupture energy declined significantly, with reductions of 25.3% in TGA and 30.6% in TGB. The static coefficient of friction was lowest on glass surfaces (0.24–0.36 for TGA and 0.33–0.45 for TGB), demonstrating variation in surface interaction. For flour samples, bulk density decreased by 13.7% (TFA) and 11.01% (TFB) with increasing moisture content. Powder flow analysis revealed that increasing moisture content reduced flowability, with PFSD decreasing across all samples. TFA became highly cohesive with reduced flow stability, while TFB remained mostly free-flowing with minimal changes in cohesion and caking strength. Higher moisture (15–20%) improved viscosity, while lower moisture (5–10%) raised pasting temperature and reduced peak viscosity, delaying gelatinization. Scanning electron microscopy revealed a more pronounced lumpy and agglomerated structure, with particles forming larger clusters as moisture content increased. These findings highlight the critical role of moisture in modulating teff grain and flour properties, impacting processing efficiency, storage stability, and equipment design.