*5.2. Experimental Methods*

#### 5.2.1. Preparation of Standard Stock and Working Solutions of ZEN and OTA

ZEN was dissolved in a methanol solution, and OTA was dissolved in an acetonitrile solution to prepare 100 and 10 μg/mL standard stock solutions, respectively. The solutions were stored at −20 ◦C. A certain amount of ZEN standard stock solution was collected and dried using nitrogen. Then, methanol and acetonitrile were added for secondary dissolution to prepare 1.0 μg/mL ZEN/Met and ZEN/Ace standard working solutions, respectively. The solutions were stored at 4 ◦C for EBI. A certain amount of ZEN standard stock solution and methanol was used to prepare 50 μg/mL of standard working solution and stored at 4 ◦C for subsequent ozone treatment. A certain amount of OTA standard stock solution was obtained and dried by nitrogen. Then, methanol and acetonitrile were added for secondary dissolution to prepare 1.0 μg/mL OTA/Met and OTA/Ace standard working solutions, respectively. The solutions were stored at 4 ◦C for EBI. A portion of OTA standard stock solution and acetonitrile was used to prepare a 5 μg/mL working solution and stored at 4 ◦C for subsequent ozone treatment.

#### 5.2.2. Measurement of ZEN and OTA Contents

An Agilent 1260 HPLC with a G1321B fluorescence detector was employed. The chromatographic column was a ZORBAX SB-C18 column (4.6 mm × 150 mm). The filling diameter and column temperature were 5 μm and 35 ◦C, respectively. The injection volume was 20 μL. The flow phase of ZEN was methanol/water (60/40, v/v) with the flow rate set at 1.0 mL/min. The detection wavelength was 274 and 440 nm for the excitation and emission wavelengths, respectively. The flow phase of OTA was water/acetonitrile/acetic acid (56/43/1, v/v/v), and the flow rate was 0.9 mL/min. The detection wavelength consisted of 333 and 477 nm for the excitation and emission wavelengths, respectively.

#### 5.2.3. Drawing of Standard ZEN and OTA Curves

Several ZEN and OTA standard stock solutions were selected. ZEN (i.e., 0.5, 1.0, 2.0, and 5.0 μg/mL) and OTA standard working solutions (i.e., 0.1, 0.2, 0.5, and 1.0 μg/mL) were prepared by the flow phase. The relation curves between the absorption peak area in the liquid chromatograph and concentration of solutions were drawn and the standard curves of ZEN and OTA were drawn according to these relation curves.

#### 5.2.4. Degradation of ZEN and OTA by Ozone

Ozone was generated by a high-pressure discharger from an ozone generator connected with an external oxygen source. Ozone concentration was adjusted by controlling the current of the ozone generator, and changes in ozone concentration were monitored online by ozone concentration detectors. The excess ozone was eliminated by the decomposition of the ozone destroyer.

A total of 2 mL ZEN (50 μg/mL) and OTA (5 μg/mL) working solutions were dissolved in a piece of 10 mL polyethylene centrifuge tube, which was supplied with ozone. The ozone treatment conditions for ZEN were as follows: concentration = 2.0 mg/L, flow rate = 1.0 L/min, and treatment time = 0, 1, 2, 3, 5, and 10 s. The ozone treatment conditions for OTA were as follows: concentration = 50.0 mg/L, flow rate = 1.0 L/min, and treatment time = 0, 10, 30, 60, 90, 120, and 180 s. After the ozone treatment, nitrogen was supplied for 3 min, and then the reaction was terminated. Subsequently, 1 mL flow phase was used for secondary dissolution.

#### 5.2.5. Degradation of ZEN and OTA by EBIs

A total of 2 mL ZEN and 2 mL OTA working solutions were placed in a 5 mL polyethylene centrifuge tube. Irradiation doses were 0, 2, 4, 6, 8, 10, 12, 14, and 16 kGy. The accelerated electron energy was 5 MeV, and the electron beam current was 20 mA with a 1000 mm scan width. The dose rate was 2 kGy/s. The samples were dried by nitrogen after irradiation, and a 1 mL flow phase was used for secondary dissolution.

## 5.2.6. Data Processing

Sample processing and detection were repeated at least three times. One-way analysis of variance was performed by the Statistical Package for the Social Sciences version 17.0. *p* < 0.05 was considered to be statistically significant. *p* >0.05 was not statistically significant.

**Author Contributions:** Conceptualization, K.Y. and K.L.; Data curation, K.Y. and L.P.; Formal analysis, K.L.; Funding acquisition, K.Y.; Investigation, L.P. and X.L.; Methodology, K.Y. and L.P.; Project administration, X.L.; Resources, K.Y. and X.L.; Software, K.L., J.X., Y.Z. and Z.C.; Supervision, J.X. and L.W.; Validation, K.L. and J.W.; Visualization, L.W.; Writing—original draft, K.Y.; Writing—review & editing, K.Y., R.W. and Z.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was financially supported by the National Key Research and Development Program of China (2017YFC1600904), the Jiangsu Agriculture Science and Technology Innovation Fund CX(17)1003, the China Agriculture Research System (CARS-02-32), the Open Foundation of Beijing Advanced Innovation Center for Food Nutrition and Human Health (20182014), the National Natural Science Foundation of China (31771898), and the National Top Youth for Grain Industry (LQ2018302).

**Conflicts of Interest:** The authors declare no conflict of interest.
