*2.7. Adsorption Capacity in the Colon of Okara-HPIDF before/after Fermentation* 2.7.1. Basic Characteristics of HPIDF/F-HPIDF

We chose water-holding capacity (WHC), water-swelling capacity (WSC), and oilholding capacity (OHC) as the basic characteristics of HPIDF/F-HPIDF. The determination was described by Zhang et al. [22] with minor changes. Briefly, water-holding capacity (WHC): 1.00 g sample (M1) and 20 mL of water were mixed in a dry centrifuge tube (M0). The sample was kept at RT for 24 h and centrifuged at 4000 rpm for 20 min. The supernatant was removed, and the weight (M2) was measured.

$$\text{WHC (g/g)} = (\text{M2} - \text{M0}) / \text{M1} \* 100\%$$

Water-swelling capacity (WSC): 0.10 g (M0) sample was taken into the calibration tube (V0), 10 mL water was added and let to stand for 24 h, and the volume (V1) was recorded.

$$\text{WSC (mL/g)} = (\text{V1} - \text{V0})/\text{M0}$$

Oil-holding capacity (OHC): 1.00 g sample (M1) and 20 mL of oil (soybean oil/lard) were mixed in a dry centrifuge tube (M0). The sample was kept at RT for 18 h and centrifuged at 4000 rpm for 20 min. The supernatant was removed, and the weight (M2) was measured.

$$\text{OCHC (g/g)} = (\text{M2} - \text{M0})/\text{M1} \text{ \* } 100\% \text{ \*}$$

Soybean oil represents unsaturated oil, and lard represents saturated oil.

#### 2.7.2. Heavy Metals-Adsorption Capacity (HMAC)

HMAC was measured by the methods of the previous study [16] with minor changes. The 50 μg/mL standard solution of Pb2+(Pb(NO3)2), Zn2+(Zn(NO3)2), Cu2+(Cu(NO3)2), and Cd2+(Cd(NO3)2) were prepared as the initial concentration to determine the HMAC of HPIDF/F-HPIDF. Total of 10 mL of four kinds of standard solutions were mixed with 0.1 g HPIDF (500 μg of metal ions in the system) separately, and stirred at 37 °C for 14 h before centrifuging at 4000 rpm for 20 min. The 240 Duo GFAAS (Agilent, Lexington, MA, USA) was used to detect the content of Pb2+, Zn2+, Cu2+, and Cd2+ in the supernatant according to the preinstalled methods of the workstation.

#### 2.7.3. Potentially Harmful Substances-Adsorption Capacity

Glucose-adsorption capacity (GAC), cholesterol-adsorption capacity (CAC), sodium cholate-adsorption capacity (SCAC), acrylamide-adsorption capacity (AAC), and nitriteadsorption capacity (NAC) were selected as the measurement indicators of potentially harmful substances-adsorption capacity. The details are as follows:

1. GAC 0.1 g HPIDF/F-HPIDF, mixed with 10 mL 100 mmol/L glucose solution at 37 °C for 16 h, centrifuged at 4000 rpm for 20 min, and the supernatant was taken to determine the glucose concentration using a glucose kit (hexokinase method, A154-2- 1, Nanjing Jiancheng Bioengineering Institute).


#### *2.8. Statistical Analysis*

The measurements of all samples should be repeated for at least three times and the results were expressed as the mean ± standard deviations (x ± SD). ANOVA with Duncan's test and Tukey's test was used to compare the data for the differences, *p* < 0.05 represented significant differences.MS Word and GraphPad Prism 6 (GraphPad Software Inc., San Diego, CA, USA) were used to organize the data, draw the graphs and tables.
