## 3 Results and Discussion
### Volatile Flavor Evaluation of Black Rice
#### 3.5.2 GC-Ms
** & **A** & **B** & **C** & **D** & **E** & **F** \\ \hline \multicolumn{1}{c}{Aliphatic/Alicyclic Ketones} & & & & & & \\ \hline Isophorone & 78-59-1 & 13.28 \(\pm\) 2.17 \({}^{\text{a}}\) & 11.30 \(\pm\) 0.84 \({}^{\text{b}}\) & 11.79 \(\pm\) 2.18 \({}^{\text{ab}}\) & 11.23 \(\pm\) 1.81 \({}^{\text{ab}}\) & 10.92 \(\pm\) 1.93 \({}^{\text{b}}\) & 11.39 \(\pm\) 1.18 \({}^{\text{ab}}\) \\ \hline \multicolumn{1}{c}{Aliphatic Aldehydes} & & & & & \\ \hline Hexanal & 66-25-1 & 148.56 \(\pm\) 32.75 \({}^{\text{a}}\) & 87.77 \(\pm\) 5.53 \({}^{\text{b}}\) & 101.70 \(\pm\) 31.22 \({}^{\text{b}}\) & 70.09 \(\pm\) 8.31 \({}^{\text{c}}\) & 67.25 \(\pm\) 10.16 \({}^{\text{c}}\) & 90.93 \(\pm\) 17.73 \({}^{\text{bc}}\) \\ Nonanal & 124-19-6 & 24.78 \(\pm\) 5.13 \({}^{\text{a}}\) & 19.17 \(\pm\) 3.19 \({}^{\text{b}}\) & 15.39 \(\pm\) 7.04 \({}^{\text{a}}\) & 12.95 \(\pm\) 1.27 \({}^{\text{c}}\) & 12.78 \(\pm\) 3.09 \({}^{\text{c}}\) & 24.63 \(\pm\) 2.56 \({}^{\text{a}}\) \\ Decanal & 112-31-2 & 3.50 \(\pm\) 1.30 \({}^{\text{a}}\) & 2.34 \(\pm\) 0.87 \({}^{\text{a}}\) & 4.50 \(\pm\) 1.94 \({}^{\text{a}}\) & 4.41 \(\pm\) 3.96 \({}^{\text{a}}\) & 2.06 \(\pm\) 0.59 \({}^{\text{a}}\) & 2.48 \(\pm\) 0.84 \({}^{\text{a}}\) \\ \hline \multicolumn{1}{c}{Aromatics} & & & & & \\ \hline p-Xylene & 106-42-3 & 655.40 \(\pm\) 94.36 \({}^{\text{a}}\) & 230.86 \(\pm\) 18.37 \({}^{\text{b}}\) & 188.26 \(\pm\) 36.98 \({}^{\text{b}}\) & 91.57 \(\pm\) 11.26 \({}^{\text{c}}\) & 51.86 \(\pm\) 7.27 \({}^{\text{c}}\) & 45.15 \(\pm\) 8.79 \({}^{\text{c}}\) \\ Furan, 2-pentyl- & 3777-69-3 & 54.84 \(\pm\) 11.20 \({}^{\text{a}}\) & 41.72 \(\pm\) 3.37 \({}^{\text{b}}\) & 47.93 \(\pm\) 10.93 \({}^{\text{ab}}\) & 30.85 \(\pm\) 5.40 \({}^{\text{c}}\) & 21.46 \(\pm\) 4.16 \({}^{\text{cd}}\) & 12.72 \(\pm\) 4.95 \({}^{\text{d}}\) \\ Phenol, 2-methoxy- (Guaicool) & 90-05-1 & 14.54 \(\pm\) 2.38 \({}^{\text{b}}\) & 15.69 \(\pm\) 2.74 \({}^{\text{ab}}\) & 19.39 \(\pm\) 4.79 \({}^{\text{a}}\) & 11.96 \(\pm\) 3.40 \({}^{\text{bc}}\) & 9.92 \(\pm\) 1.31 \({}^{\text{c}}\) & 5.51 \(\pm\) 1.46 \({}^{\text{d}}\) \\ \hline \multicolumn{1}{c}{Aliphatic Alcohols} & & & & & \\ \hline
1-Octen-3-ol & 3391-86-4 & 19.56 \(\pm\) 4.07 \({}^{\text{b}}\) & 16.67 \(\pm\) 2.25 \({}^{\text{b}}\) & 18.38 \(\pm\) 5.14 \({}^{\text{b}}\) & 16.01 \(\pm\) 3.03 \({}^{\text{b}}\) & 18.71 \(\pm\) 3.70 \({}^{\text{b}}\) & 24.93 \(\pm\) 2.23 \({}^{\text{a}}\) \\ \hline \multicolumn{1}{c}{Alikanes} & & & & & \\ \hline Tetradecane & 629-59-4 & 4.26 \(\pm\) 1.54 \({}^{\text{d}}\) & 9.00 \(\pm\) 2.27 \({}^{\text{bc}}\) & 17.60 \(\pm\) 6.22 \({}^{\text{a}}\) & 10.74 \(\pm\) 2.20 \({}^{\text{b}}\) & 7.50 \(\pm\) 1.40 \({}^{\text{b}}\) & 6.47 \(\pm\) 1.69 \({}^{\text{cd}}\) \\ Hexadecane & 544-76-3 & 3.34 \(\pm\) 1.07 \({}^{\text{c}}\) & 5.62 \(\pm\) 1.70 \({}^{\text{b}}\) & 9.47 \(\pm\) 3.00 \({}^{\text{a}}\) & 6.10 \(\pm\) 1.32 \({}^{\text{b}}\) & 4.24 \(\pm\) 1.22 \({}^{\text{bc}}\) & 4.60 \(\pm\) 1.20 \({}^{\text{bc}}\) \\ \hline \multicolumn{1}{c}{N-Containing Compounds} & & & & & \\ \hline Benzothiazole & 95-16-9 & 12.70 \(\pm\) 6.19 \({}^{\text{b}}\) & 15.88 \(\pm\) 2.55 \({}^{\text{ab}}\) & 15.10 \(\pm\) 3.39 \({}^{\text{ab}}\) & 19.77 \(\pm\) 3.85 \({}^{\text{a}}\) & 13.84 \(\pm\) 3.88 \({}^{\text{b}}\) & 14.46 \(\pm\) 1.90 \({}^{\text{b}}\) \\
2-Amino-5- & 2-Amino-5- & 44.07 \(\pm\) 6.68 \({}^{\text{bc}}\) & 35.66 \(\pm\) 5.62 \({}^{\text{c}}\) & 55.35 \(\pm\) 16.23 \({}^{\text{ab}}\) & 58.26 \(\pm\) 8.26 \({}^{\text{a}}\) & 62.62 \(\pm\) 12.00 \({}^{\text{a}}\considered key aroma components, while p-xylene, 2-pentyl-furan, and 2-methoxy-phenol were modified aroma components in cooked whole black rice (Table 6). A supervised model PLS-DA was then conducted to optimize sample separation and identify volatiles' differences (relative concentration or OAV) arising from milling degree [61]. In the analysis, the milling degree was set as classes and the model was validated by an internal validation method.