Mechanical grinding alters physicochemical, structural, and functional properties of tobacco (Nicotiana tabacum L.) leaf powders

Abstract Utilizing tobacco industrial waste can increase added value without increasing the environmental burden. The physicochemical, structural, and functional properties of tobacco leaf powders produced by coarse and superfine grinding treatments with different particle size were investigated. The particle size was significantly reduced by superfine grinding to micron scale (10.3 μm), and the specific surface area sharply increased. With decreasing particle size, the bulk density, tap density, angles of repose and slide increased, but water and oil holding capacities decreased, indicating the worse flowability and hydration property. The increasing lightness and yellowness but decreasing redness were observed after superfine grinding. Differential scanning calorimetry curves showed that superfine grinding insignificantly affected the conformation stability and denaturation degree of proteins. Fourier transform infrared spectroscopy proved unchanged main structure and decreased chain length of polysaccharide polymer. Morphology revealed that the shape of superfine ground sample was changed from an irregular polygon to spherical-like, and surface roughness was reduced. All cell walls were disrupted after superfine grinding, but the dissolution yields of nicotine and total phenolic, and antioxidant activities were not enhanced. The median particle size of 93.9 μm was the most effective for the ingredient dissolution and antioxidant capacity. This study was expected to supply new insights in guiding the development of discarded tobacco in practice.