Study on Some Rheological and Frictional Properties of Yam Flour (dioscorea Rotundata)

This study investigated the influence of moisture content (3–13% wet basis) and surface material on the rheological and frictional properties of yam (Dioscorea rotundata) flour. Rheological properties were analyzed using a Rapid Visco Analyzer (RVA), while sliding friction and angle of repose were measured on aluminum, wood, metal, and glass surfaces. Moisture content significantly altered rheological behavior: pasting temperature decreased significantly (p< 0.05) from 84.94°C (3% moisture) to 74.76°C (13% moisture). Peak viscosity also declined significantly (p < 0.05) from 1886 RVU (3% moisture) to 1401 RVU (13% moisture). Trough viscosity similarly decreased (1072 to 919 RVU, p < 0.05). However, apparent viscosity (2153 to 1985 RVU) and shear viscosity (1298.50 to 1210.00 RVU) showed no significant differences (p> 0.05). Frictional properties were unaffected by surface type: sliding friction angles for aluminum, wood, metal, and glass were statistically similar (8.22°, 8.50°, 9.01°, and 8.09°, respectively; p > 0.05). The angle of repose remained high (87.95°–88.25°) across all surfaces and moisture levels, indicating poor flowability. Results demonstrate that moisture content critically impacts pasting properties, while surface material has minimal effect on friction. Maintaining moisture below 15% is recommended to preserve functional quality and enhance flow during handling.