*2.7. X-ray Diffraction (XRD)*

XRD (D8 Advance, Bruker, Karlsruhe, Germany) was used to determine the crystallinity of PoS and PoS-PPC complexes, based on a previous paper [28]. The scanning range of the diffraction angle (2θ) was 4◦–40◦. The relative crystallinity was computed by an integral using the Origin software (3):

$$\text{Relative } crystail limity \text{ (\%)} = \frac{A\_c}{A\_c + A\_a} \times 100 \tag{3}$$

here *Ac* and *Aa* stand for the crystal and amorphous areas, respectively.

### *2.8. In Vitro Digestion*

The in vitro digestibility of PoS and PoS-PPC compounds was analyzed in accordance with the preceding literature, with some modifications [29,30]. A total of 200 mg of starch or starch-PPC mixture samples was dissolved in 5 mL water, fully gelatinized, cooled, and added with 15 mL phosphate buffered solution (pH = 5.2). Subsequently, 5 mL of mixed digestive enzyme fluid (13 U/mg porcine pancreatic α-amylase, 260 U/mg glucoamylase) was added to the PoS or PoS-PPC mixtures, and then incubated at 37 ◦C. Other steps refer to previous studies. The contents of rapidly digested starch (RDS), slowly digested starch (SDS), and resistant starch (RS) in starch fractions were computed with the Equations (4)–(6) below:

$$RDS\ \left(\%\right) = \frac{G20 - FG}{TG} \times 0.9 \times 100\tag{4}$$

$$\left(SDS\ \left(\%\right)\right) = \frac{G120 - G20}{TG} \times 0.9 \times 100\tag{5}$$

$$RS\ \left(\%\right) = \frac{TG - \left(RDS + SDS\right)}{TG} \times 100\tag{6}$$

Here, *G*20 and *G*120 refer to the contents of glucose generated at 20 and 120 min of the hydrolysis process, respectively. *FG* is the content of free glucose in samples, and *TG* is the total amount of starch in the original sample.

#### *2.9. Statistical Analyses*

The data were represented as the means ± standard deviation (SD) conducted in triplicate analyses. Duncan's test was carried out in SPSS 24.0 statistical software, and at *p* < 0.05, the significant difference was set.
