**2. Results**

#### *2.1. Standard Curves of Zearalenone (ZEN) and Ochratoxin A (OTA)*

The linear correlation between the peak area and concentration (0.5–5.0 and 0.1–1.0 μg/mL) was clarified on the basis of the standard curves of ZEN and OTA (Figure 1). The regression equations of the ZEN and OTA standard curves are marked in Figure 1. R<sup>2</sup> represents the square of the correlation coe fficient, and the determination coe fficient R<sup>2</sup> is a relative index of goodness of fit between the regression line and the observed value of the sample, reflecting the proportion of the fluctuations of the dependent variable that can be explained by the independent variable. The closer R<sup>2</sup> is to 1, the better the goodness of fit. R<sup>2</sup> of the regression equations in the ZEN and OTA standard curves were 0.9999 and 0.9998, respectively, indicating a high degree of linear regression.

#### *2.2. Degradation Rates of ZEN and OTA by Ozone*

The degradation rates of 2 mL of 50 μg/mL ZEN standard working solution (a) and 2 mL of 5 μg/mL OTA standard working solution (b) by ozone under di fferent treatment time periods are shown in Figure 2. The degradation rate of ZEN at 1 s was higher than 50%. The degradation of ZEN slowed down with the increase in treatment time. No ZEN was detected in the solution at 10 s. The degradation curve of OTA from 0–180 s was a reverse S-shaped curve. The degradation rate of

OTA increased during the first 30 s and decreased between 30–60 s, but it increased gradually between 60–180 s and reached the peak (34%) at 180 s.

**Figure 1.** High-performance liquid chromatography (HPLC) standard curves of zearalenone (ZEN) (**a**) and ochratoxin A (OTA) (**b**).

**Figure 2.** Degradation curves of ZEN (**a**) and OTA (**b**) by ozone at different treatment time periods.

*2.3. Degradation of ZEN and OTA by Electron Beam Irradiation (EBI)*

#### 2.3.1. Degradation of ZEN by EBI

The degradation curves of 1.0 μg/mL ZEN in methanol and acetonitrile solution under different EBI doses (i.e., 0, 2, 4, 6, 8, 10, 12, 14, and 16 kGy) are shown in Figure 3. The degradation rate of ZEN in the acetonitrile solution was higher than that in the methanol solution under 0–6 kGy. However, the degradation rate of ZEN in acetonitrile decreased gradually with the increase in dose, higher than that in acetonitrile at an irradiation dose exceeding 6 kGy. The degradation of ZEN slowed down in methanol with the increase in irradiation dose. The degradation rates of ZEN in methanol and acetonitrile were 92.76% and 72.29%, respectively, at 16 kGy. Methanol was conducive to the degradation of ZEN by EBI at high irradiation doses. According to the literature, EBI possesses unique advantages in degrading fungal toxins, and considerable development of this approach has been complicated. Liu et al. processed AFB1 in sewage by EBI [23]. The 1 and 5 μg/mL toxin samples were degraded completely at 8 kGy. Peng et al. irradiated OTA in different solvent systems by electron beams and disclosed the degradation rates of OTA under the same concentration as follows: water > acetonitrile > methanol–water (60:40, v/v) [24]. Therefore, EBI can also degrade ZEN in a methanol solution.

**Figure 3.** Degradation curve of ZEN in methanol (Met) and acetonitrile (Ace) at different electron beam irradiation (EBI) doses. Data are presented as means ± standard deviation (SD). \*\*\* *p* < 0.01, \*\* 0.01 < *p* < 0.05, and \* *p* > 0.05.

#### 2.3.2. Degradation of OTA by EBI

The degradation of 1 μg/mL OTA in methanol and acetonitrile solution at different EBI doses (i.e., 0, 2, 4, 6, 8, 10, 12, 14, and 16 kGy) is shown in Figure 4 with S-shaped curves, indicating that the contents of the active substances (such as free radicals and active oxygen), which can react with OTA in the solvent system, initially increased and then decreased. In the irradiation dose range of 0–6 kGy, the degradation rate of OTA in the two solvent systems gradually increased and slowly degraded at 6 kGy. The degradation rates of OTA in methanol and acetonitrile at 16 kGy reached the maximum values of 84.16% and 91.56%, respectively.

**Figure 4.** Degradation curve of OTA in Met and Ace at different EBI doses. Data are presented as means ± SD. \*\*\* *p* < 0.01, \*\* 0.01 < *p* < 0.05, and \* *p* > 0.05.

#### 2.3.3. Effects of Solvents on Degradation of ZEN and OTA by EBI

Methanol is a common protic solvent and ·OH and *e*−*aq* quencher [25]. Acetonitrile is a common aprotic polar solvent. Both are widely used as solvents of fungal toxins. The acetonitrile solutions of ZEN and OTA after EBI application turned yellow, with its color deepening as the radiation dose increased. In contrast, the methanol solution remained transparent. The acetonitrile solutions of ZEN and OTA after EBI (i.e., 0, 4.0, 8.0, 12.0, and 16.0 kGy) are shown in the order from left to right in Figure 5a,b, respectively. Kameneva et al. irradiated acetonitrile molecules in a solid inert gas matrix by x-ray [26]. The Fourier infrared spectrum detection showed that acetonitrile molecules generated CH3NC, CH2CNH, and CH2NCH molecular polymers and free radicals such as CH2CN and CH2NC.

**Figure 5.** Degradation samples of ZEN (**a**) and OTA (**b**) treated with EBI in Ace.
