*3.1. Flavor Differences in Turmeric Volatile Oil under Different Irradiation Intensities Detected by GC–IMS*

Three-dimensional topographic plots of turmeric irradiated by three different doses are shown in Figure 1A. We assessed the volatile organic compounds (VOC) in different samples from three perspectives: retention time, drift time, and peak intensity. The number of VOCs and the signal intensity of the peaks differed slightly among the three samples. With the increase in irradiation intensity, only the signal intensity of the peaks changes slightly, and almost no new compounds form.

A two-dimensional topographic spectrum (planform of the 3D plot) was also obtained for its difficulty to observe the differences between three-dimensional groups (Figure 1B). In this plot, the red vertical line at 1.0 on the left is the reaction ion peak (RIP), and the background image is blue. Each point on both sides of the reaction ion peak represents a VOC, the color depth represents the volatile-compound content, the white area represents the low compound content, and the red area represents the high compound content. Using the difference comparison mode, we select the spectrum (JH-1) of one sample as the reference, and we deduct the spectrum of other samples from the reference to obtain Figure 1C. If the volatile organic compounds of the two samples are consistent, then the background after deduction is white, while red signifies that the concentration of the substance is higher than the reference, and blue implies that the concentration of the substance is lower than the reference. It can be seen from Figure 1B,C that signals are concentrated in areas A, B, and C. The color of some compounds in areas A and C is deepened, and the color of compounds in area B is lighter, which suggests that with the increase in irradiation dose, the compound content in regions A and C increases and in the regioqualitative analysis of volatile organic compounds.

Figure 1D shows the binary spectra of all volatile substances of turmeric volatile oil under three irradiation intensities. The volatile compounds in the volatile oil of turmeric were analyzed by GC. The NIST database and IMS database built into the IMS library were according to the retention index, retention time, and ion migration time. We identified 64 volatile components shown in Table 1 from the three sample varieties in Figure 1D. The substance numbers in Figure 1D are consistent with those in Table 1.

**Figure 1.** *Cont*.

**Figure 1.** Volatile compounds analysis by GC-IMS. (**A**) 3D-topographic; (**B**) topographic plots; (**C**) topographic subtraction plots; (**D**) post-irradiation topographic plots; (**E**) volatile compounds fingerprint comparisons. Each row represents all the signals selected in a sample. Each column represents the signal of the same volatile compound. (**F**) Principal component analysis; (**G**) Fingerprint similarity analysis.

According to Tables 1 and 2, there are 64 monomers and dimers of volatile substances identified in turmeric volatile oil, including 17 alcohols and phenols, 11 aldehydes, 11 ketones, 9 terpenes, 8 esters, 4 carboxylic acids and their derivatives, 3 furans, and 1 thiophene. The chemical formula of the identified monomer and dimer is the same as the CAS number, but the form is different. The results are shown in Tables 1 and 2.


**Table 1.** Volatile substances contained in turmeric volatile oil.


**Table 2.** Area of turmeric volatile oil.
