Properties of lignin microparticles prepared by mechanical treatment

Abstract

The present study aimed to obtain Kraft lignin microparticles by mechanical treatment and compare them with initial Kraft lignin in terms of their chemical, thermal and structural properties, as well as possible antioxidant and antimicrobial effects. Ball milling reduced the particle size from 6.6 µm to 3.1 µm. The zeta potential and polydispersity index measurements revealed greater instability of the microparticles, with a higher tendency to agglomerate, and higher homogeneity, when compared with Kraft lignin. These findings were also evidenced by scanning electron microscopy. The thermal degradation behavior was not affected by the mechanical treatment utilized in the production of microparticles. X-ray diffraction showed crystalline and amorphous regions in the particles. Infrared spectroscopy revealed that the microparticles maintained the characteristic peaks of Kraft lignin, with lower peak intensity. The samples proved high antioxidant potential, as determined by the 2,2-diphenyl-1-picryl-hydrazyl assay, regardless of the concentration studied. Therefore, the results of the study demonstrated that the obtained Kraft lignin microparticles could be suitable for the development of antioxidant food packaging.