Powder Technology, Vol.339, 560-568, 2018
Effect of vibrating-type ultrafine grinding on the physicochemical and antioxidant properties of Turkish galls in Uyghur medicine
We evaluated the influence of a vibrating-type ultrafine grinding treatment on the physical and chemical properties and antioxidant activity of Turkish gall powder (TGP) with particle sizes of >450, 400-250, 250-100, 100-50, and < 50 mu m. The physical properties were analyzed and we found that the small particle size of the TGP increased the bulk (from 0.68 to 0.32 g/cm(3)) and tapped densities (from 0.83 to 0.70 g/cm(3)) and increased the repose (from 35.43 degrees to 56.28 degrees), slide (from 35.54 degrees to 59.23 degrees), and crash angles (from 35.68 degrees to 42.91 degrees). The total ash content (from 2.34% to 1.75%) decreased, but the moisture index and water solubility index were improved. The extract of TGP with a particle size of <50 mu m indicated that highest gallic acid content (9.47 mg/g), methyl gallate content (34.78 mg/g) and ellagic acid contents (0.79 mg/g) accompanied with the best DPPH, hydroxyl radical, and superoxide. radical scavenging activities (p < .05). Moreover, the FUR analysis suggested that the ultrafine grinding did not damage the main structure of the components as the particle sizes decreased. The SEM images demonstrated the shape of the TGP with different particle sizes and surface morphology. The microscopic identification exhibited the vessels, oil cells, starch grains, and cluster crystals, which provided referential information in evaluating the Turkish gall quality. (C) 2018 Published by Elsevier B.V.