Abstract: Mulberry pomace was modified using high-pressure homogenization (HPH, 80 MPa, 2 cycles) or ultra-high pressure (UHP, 600 MPa, 15 min). Soluble dietary fiber fractions (SDF1 and SDF2) and insoluble dietary fiber (IDF) were subsequently extracted using alkaline hydrogen peroxide. Untreated pomace (CK) served as the control. Our aim was to investigate the effects of modification methods on the yield, structural characteristics, physicochemical properties, and functional properties of SDF1, SDF2, and IDF. The results demonstrated that both HPH and UHP modifications significantly increased the yield of SDF1 (by 33.76% and 41.88%) and SDF2 (18.21% and 67.50%, respectively), and notably reduced the molecular mass of SDF2. Monosaccharide composition analysis revealed that SDF1, SDF2, and IDF all consisted of arabinose, rhamnose, galactose, glucose, xylose, mannose, galacturonic acid, and glucuronic acid. However, both HPH and UHP modifications altered the proportion of these monosaccharides. Fourier transform infrared spectroscopy (FTIR) indicated that the characteristic functional groups of SDF1, SDF2, and IDF were primarily hydroxyl, carboxyl, C–H bonds, O–H bonds, and glycosidic bonds. X-ray diffraction (XRD) confirmed that SDF1 and IDF exhibited the cellulose I crystalline structure. Scanning electron microscopy (SEM) revealed that HPH and UHP modifications significantly altered the microstructure of the dietary fibers, enhancing surface wrinkling in IDF. Regarding physicochemical properties, both HPH and UHP modifications significantly improved the thermal stability and water-holding capacity of the dietary fibers. HPH-modified SDF1, SDF2, and IDF exhibited superior performance in antioxidant activities measured by the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging and the ferric reducing antioxidant power (FRAP) assay, α-glucosidase inhibitory activity, and nitrite ion-adsorbing capacity. By contrast, UHP-modified SDF1 showed enhanced α-amylase inhibitory activity and glycocholate binding capacity. In summary, both HPH and UHP modifications effectively regulated the yield, structural characteristics, and functional properties of mulberry pomace dietary fiber. The choice of modification methods can be tailored based on specific application requirements during practical production, thereby facilitating the development of value-added dietary fiber products from mulberry pomace and extending the mulberry processing industry chain.

Key words: mulberry pomace; dietary fiber; modification; high-pressure homogenization; ultra-high pressure