Empirical Assessment of the Relationship Between Milling Conditions and Rheological Properties of Nigerian Hard Wheat Flour

The rheological properties of wheat flour fundamentally determine its suitability for specific bakery applications, and the milling conditions under which flour is produced significantly influence these properties through their effects on starch damage, particle size distribution, and gluten development potential. This study empirically assesses the relationship between key milling conditions and the rheological properties of hard wheat flour in a commercial flour mill in Kano, North West Nigeria. Milling variables investigated include mill gap setting (0.05 to 0.15 mm), roller differential (1:1.25 to 1:1.75), and moisture content of conditioned wheat (14 to 17 percent). A response surface methodology with a central composite design was employed. Rheological characterisation was performed using a Brabender farinograph, extensograph, and Rapid Visco Analyser. Response variables included water absorption, dough development time, stability, extensibility, resistance to extension, ratio number, peak viscosity, breakdown viscosity, and setback viscosity. Results showed that starch damage increased with narrower mill gap settings and higher moisture content, with a consequent increase in water absorption and alteration of gelatinisation profile. Multiple regression models developed for each rheological parameter achieved R-squared values above 0.85. The study contributes quantitative empirical data linking milling parameters to flour functionality, filling a gap in the Nigerian flour milling literature. Findings provide direct guidance for mill operators and bakery quality departments in optimising raw material performance. Keywords: wheat flour, rheology, milling conditions, starch damage, response surface