Influence of particle size on the color, rheological, and textural properties of sesame paste

Abstract

This study investigates the impact of particle size on the physical, rheological and textural properties of sesame paste prepared from sesame seeds by colloid milling. Four sesame paste samples (SP1–SP4) were processed with varying milling gap sizes. Particle size distribution revealed a significant reduction in particle size with smaller milling gaps, resulting in finer pastes with decreased oil separation. Finer particles enhance lightness, thereby contributing to the visual appeal of the product while also decreasing yellowness index. The finest sample exhibited the smallest D50 value. Rheological behavior was modeled using the Herschel–Bulkley model, showing that both yield stress and consistency coefficient decreased as particle size diminished. The creep test results, fitted using the four-element Burger’s model, revealed that smaller particles led to higher initial compliance (Jo), retarded compliance (J1), and retardation period (λ), indicating increased material flexibility and longer stress-relaxation period. Viscosity (η) increased significantly with reduced particle size, suggesting greater internal resistance to flow, probably because of enhanced particle interactions. The textural analysis confirmed that finer particles resulted in lower hardness and work of shear, leading to a softer and a more easily spreadable paste. In industry, optimizing particle size distribution ensures desirable product qualities, consistency, and consumer satisfaction.