Effect of different pretreatment methods on soluble dietary fiber macromolecules extracted from Korla fragrant pear (Pyrus sinkiangensis Yü): Structure, physicochemical properties, and biological activity

Herein, Korla fragrant pear (KFP) was subjected to ultrasonication (UA), microwave (MA), high-pressure humid heat (HPHH), and composite enzyme hydrolysis (CEH) pretreatments before the extraction of soluble dietary fiber. The yield, structural characteristics, and functional properties of SDF obtained after the different pretreatments were compared. All the aforementioned pretreatment methods increased the yield of SDF and decreased that of insoluble dietary fiber. The highest yield of SDF was obtained after the HPHH pretreatment (10.11 %). The SDF obtained after pretreatment exhibited loose, cracked, and porous structures, decreased crystallinity and molecular weight (M w ), and improved physicochemical and functional properties. The highest water solubility (72.35 %), cation exchange capacity (0.92 mmoL/g), glucose adsorption capacity (7.80 mmoL/g), and cholesterol adsorption capacity (11.95 and 16.59 mg/g at pH 2 and 7, respectively), in vitro antioxidant activity, and α-glucosidase inhibitory activity were achieved following the CEH pretreatment. Multivariate analysis revealed that most of the functional properties were negatively correlated with the crystallinity and M w of SDF but positively correlated with the antioxidant activities (e.g., DPPH and ABTS) and α -glucosidase inhibitory activity. These findings provide a theoretical basis for the extraction, modification, and application of SDF extracted from KFP.