## 3 Results and Discussion  
### Spectral Characteristics of South Korean and Chinese Rice  
Figure 4 shows the fluorescence spectra of the South Korean and Chinese rice samples by year. The spectra of the rice samples from 2014 to 2016 show a similar trend in the entire wavelength range of 420 to 780 nm. The Chinese rice samples exhibit a higher reflectance than the South Korean rice samples at the overall spectral wavelength. Previous studies reported that the geographical origin can be discriminated by using the difference in the ratio of amylopectin to amylose in rice [23]. Generally, it has been reported that branched-chain amylopectin is identified by the crystallinity of the samples  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & & & & & \\ \cline{2-7}  & \(\mathbf{2\times 2}\) & \(\mathbf{3\times 3}\) & \(\mathbf{4\times 4}\) & \(\mathbf{5\times 5}\) & \(\mathbf{6\times 6}\) & \(\mathbf{7\times 7}\) & \(\mathbf{30\times 30}\) \\ \hline Training data set & 61,460 & 28,428 & 14,366 & 11,904 & 7170 & 4664 & 294 \\ Predicted data set & 30,730 & 14,214 & 7183 & 59 and is attenuated by the amount of amylose present [28]. In addition, a spectral difference appears owing to the apparent transparency and internal heterogeneity of the sample [29]. For the above reason, the South Korean rice samples had a higher amount of amylose compared to the Chinese rice samples, which had relatively low crystallinity; thus, the fluorescent intensity of the latter was low. The raw spectra revealed fluorescence peaks at 465 nm and 489 nm, along with the relatively higher reflectance of the Chinese rice samples compared to the South Korean rice samples. The main component that is used for discriminating Chinese and South Korean rice is a saturated fatty acid that shows a fluorescence peak from 450 nm to 500 nm [30]. This main component is influenced by the lipid constituent and acetic acid (CH3 COOH) containing hydroxyl (-OH), stearic acid reacting with -OH, glycine, \(\upiota\)-aspartic acid, and \(\upiota\)-glutamic acid monosodium salt monohydrate. The latter constituent is a type of amino acid. These components are factors that affect the rice quality and are influenced by nitrogen fertilization, the production environment, and the cultivation environment (temperature) [31]. Chinese rice is cultivated at a higher latitude (33-47\({}^{\circ}\) N) than South Korean rice, which is grown in colder regions. Therefore, it is believed that this study identified the spectral differences between the South Korean and Chinese rice samples. Chlorophyll a appeared mainly at 681 nm, and the higher reflectance of the South Korean rice samples was associated with the 681 nm peak [32; 33]. Performances of the Geographical Origin Discrimination Models for South Korean and Chinese Rice by Pixel Dimensions  
Various pixel dimensions were applied in the geographical origin discrimination models to determine the hyperspectral image pixel dimensions that could most effectively discriminate the geographical origin of the rice samples. Table 3 shows the performance of the developed PLSR model with pixel dimensions up to 30 mm \(\times\) 30 mm. At 30 mm \(\times\) 30 mm, R\({}_{\mathrm{V}}\)\({}^{2}\), RMSEV, and F of the discrimination model are 0.7601, 0.2456, and 9, respectively. The HSI pixel dimensions of 30 mm \(\times\) 30 mm produced the highest discrimination accuracy. For the pixel dimensions of 2 mm \(\times\) 2 mm, R\({}_{\mathrm{V}}\)\({}^{2}\), RMSEV, and F are 0.5752, 0.3247, and 10, respectively. The discriminative  
Figure 4: Fluorescence spectra of the South Korean and Chinese rice samples in the years (**a**) 2014, (**b**) 2015, and (**c**) 2016.  
performance is not excellent when the pixel dimensions are low. Moreover, as the pixel dimensions increase, RMSE and R\({}^{2}\) tend to increase, and optimal factor F decreases, which confirms that the model performance improved.