The effect of grinding on the physicochemical properties of olive mill waste

Abstract

Olive mill waste is a by-product of olive oil production, and its disposal poses serious environmental challenges; it can surprisingly serve as a possible source of functional ingredients. This study investigates the impact of grinding on the physicochemical and functional properties of dried OMW powders, aiming to enhance their applicability in food systems. The oven-dried OMW was ground and sieved into two particle size fractions (1.0 mm and 0.8 mm), which were tested to evaluate color parameters (L*, a*, b*), water activity (aw), bulk and tapped density, Carr’s Index, Hausner ratio, particle density, porosity, angle of repose, wettability, and both water and oil holding capacities. Particle size emerged to influence multiple properties. The finer 0.8 mm powder showed higher bulk density, water and oil holding capacities, and improved wettability, while it was less flowable, as indicated the higher angle of repose and Carr’s Index values. The water activity values were low, pointing to high microbial stability for both fractions. Statistically significant differences were found in such main parameters as brightness (L*), density, wettability, and hydration behaviors, thus confirming the influence of grinding on powder performance. The research underscores the potential for particle engineering to customize OMW powders for specific, functional uses in food formulations. By optimizing grinding parameters, olive mill waste would cease to be an environmental burden, becoming rather a high-value, bioactive-rich ingredient, thus meeting circular economy standards and sustainable food innovation.