2.5.3. X-ray Diffraction (XRD)

X-ray diffraction (XRD) analysis of the HPIDF/F-HPIDF was conducted according to the previous method [20], with some slight modifications. The diffraction patterns were recorded using a Rigaku Ultima IV (X-ray, Rigaku Corporation, Tokyo, Japan) operating at a voltage of 40 kV, an incident current of 40 mA, an anti-diffusion slit of 2/3, with Cu-Ka radiation (1 μ = 0.154 nm), and a scan speed of 1π/min in the range of diffraction angle from 10 to 80◦.

#### 2.5.4. Particle Size and Specific Surface Area

The BT-9300HT laser particle sizer (Bettersize Instruments Ltd., Dandong, China) was used to analyze the particle size and specific surface area of HPIDF/F-HPIDF in which the concentration of the suspension is 4% (*m*/*v*).

#### *2.6. Monosaccharide Composition of Okara-HPIDF before/after Fermentation and the Hydrolyzed*

The monosaccharide compositions of HPIDF/F-HPIDF referred to the methods of the preliminary study [16]. The monosaccharide composition of the hydrolyzed was analyzed after freeze-drying by PMP pre-column derivatization and LC-10ATvp & SPD-10AVD HPLC system (Shimadzu, Tokyo, Japan) [21].
