Abstract: In this study, we investigated the effect of jet milling frequency (100, 200 and 300 Hz) on the physicochemical properties and antioxidant activity of ultrafine powder of Aronia melanocarpa pomace, aiming to support the valorization of the pomace. The particle size distribution of the powders was measured, and they were further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging assays. Particle size analysis showed that crude A. melanocarpa pomace powder (CAMP) had a significantly larger particle size than ultrafine A. melanocarpa pomace powder (UPAM), with UPAM-300 Hz exhibiting the smallest size (7.96 μm) and the best dispersibility. XRD results revealed that all samples had core diffraction peak deviations < 0.02°, indicating unchanged phase composition. Compared with CAMP, UPAM-300 Hz showed a 1.5%–6.2% decrease in core peak intensity, with 95.1% crystallinity, exhibiting the most prominent grain refinement. SEM indicated that CAMP had an irregular blocky morphology, whereas UPAM-300 Hz showed a flaky morphology, with optimal dispersibility, the highest number of surface cracks, and the largest specific surface area. FTIR spectroscopy showed that UPAM-300 Hz had two new peaks at 778 and 1 281 cm–1, with the most extensive exposure of O–H/C–O functional groups and the highest proportion of hydroxyl radicals. TGA/DSC demonstrated that UPAM-300 Hz had a mass loss of 67.61%, the highest content of highly stable components, and a high-temperature exothermic enthalpy of 6.54 J/g. NMR confirmed that all samples retained the “aliphatic saccharide” skeleton with intact active component frameworks. The UPAM-300 Hz sample had significantly higher DPPH radical (95.00%) and ABTS radical cation (92.13%) scavenging activity than the other samples. In conclusion, UPAM-300 Hz performs best across various indicators and is suitable for applications in food and health products, providing technical support for efficient pomace utilization.

Key words: Aronia melanocarpa pomace ultrafine powder; jet milling; characterization; antioxidant activity