*2.8. Samples Preparation for Proton Nuclear Magnetic Resonance (1H NMR) Spectra Acquisition*

Freeze-dried QPI (20.0 mg) was placed in a 2 mL sample tube with 1000 μL CD4O aqueous solution (CD4O:D2O = 1:1, *v:v*; TMSP 0.5 mM). The mixed solution was placed in a tissue grinder for 300 s (70 Hz), repeated 2 times and then centrifuged (10 min, 12,738× *g*) 2 times. The supernatant (540 μL) was transferred into a nuclear magnetic tube for 1H NMR test on a 600 MHz nuclear magnetic resonance spectrometer (AVANCE III Brook (Beijing) Technology Co., Ltd., Beijing, China). The test conditions were: constant temperature of 298 K (25 ◦C), pulse interval D1 of 4.00 s, spectral width of 12,335.526 Hz, and 64 samples, using a ZGPR pulse sequence to suppress the water peak. The raw spectra were imported into MestReNova software for segment integration and normalization at 0.51 ppm [28].

#### *2.9. In Vitro Simulation of Gastrointestinal Digestion of QPI*

#### 2.9.1. Preparation of Simulated Gastrointestinal Fluid

Simulated gastricfluid (SGF) and simulated intestinalfluid (SIF) were prepared following the harmonized protocol [29]. SGF: pepsin (0.3 g), NaCl (2.0 g) and HCl (12 M, 0.7 mL) were mixed and made up to 100 mL, and the pH of the solution was adjusted to 1.2. SIF: After KH2PO4 (0.68 g) was completely dissolved in deionized water (25 mL), NaOH solution (0.2 m, 19 mL), deionized water (40 mL) and trypsin (4.0 g) were successively added, and the volume was fixed to 100 mL. The pH of the solution is 7.5.

#### 2.9.2. In Vitro Gastrointestinal Digestion

After the heat-treated QPI solution (Treatment at 90 ◦C and 121 ◦C for 30 min respectively), SGF and SIF were incubated at 37 ◦C for 10 min, equal volumes of QPI solution and SGF were taken into a centrifuge tube. The centrifuge tube was placed in a water bath shaker at 37 ◦C, and the digested products with reaction times of 0, 30, 60, 90 and 120 min were respectively taken into the test tube, and immediately boiled at 100 ◦C to kill the enzyme and cooled for later use. The pH of the remaining solution in the centrifuge tube was adjusted to 7.5, an equal volume of SIF was added, and the centrifuge tube was placed in a water bath shaker at 37 ◦C, and the digested products with reaction times of 150, 180, 210, 240 and 270 min were respectively taken into the test tube, and immediately boiled at 100 ◦C to kill the enzyme and cooled for later use [30].
