Evaluation of particle size on the physicochemical properties of Moringa oleifera Lam. stem powder

Moringa oleifera Lam. stem (MOS) has been used for beneficial dietary and medicinal purposes. In this work, MOS samples of six different particle sizes were produced using sieve-based mechanical grinding to investigate the impact of varying particle sizes on the physicochemical properties of MOS powder. Scanning electron microscopic images revealed the destroyed fiber structures after grinding. The color turned greener and less yellow with decreasing particle size. The angle of repose significantly decreased from 70.36º to 60.25º, as the particle size declined, demonstrating the increasing fluidity of granules. The applied mechanical treatment did not alter the primary conformational properties of MOS except for destructing the intramolecular hydrogen bonds of cellulose and hemicellulose, thereby decreasing the crystallinity and thermal stability. Surface element analysis demonstrated more carbon-rich extractives on the particle surface as the particle size reduced. This study provided reasons behind improved dissolution and bioavailability of functional ingredients in plant-based granular materials by reducing particle size.