# Effect of Ultrasonic Treatment on Taste and Flavor Quality of Japonic Rice
## 3 Results
### GC-MS Data Analysis
#### 3.5.3 Analysis of Aroma Compounds  
To evaluate the contribution of each volatile compound to the total change in the cooked rice aroma following ultrasonography treatment [31], the roAV obtained by dividing the concentration of an aroma compound by its odor threshold in air was used in addition to the concentration analysis. Compounds that significantly contribute to the aroma, i.e., compounds with rOAVs \(\geq\) 1 (Table 2), were screened and analyzed [32; 33]. Numbers in parentheses below represent the change in rOAVs of the aroma compounds without and after ultrasound treatment. Although hydrocarbons constituted most of the aroma substances, most of them exhibited high thresholds and contributed less to the aroma of cooked rice. In contrast, aldehydes, heterocyclics, and alcohols exhibited low thresholds and mainly contributed to the cooked rice aroma. Straight-chain alkanes, such as tridecane and tetradecane, exhibited low rOAVs and contributed less to cooked rice aroma. 2-Pentylfuran (5.47-41.46) had a fruity, nutty, and caramelized aroma [29]. Among the detected aldehydes, hexanal (2.83-20.89), octanal (3.30-32.90), nonanal (96.5-254.44), decanal (12.35-47.06), trans-2-octanal (1.23-12.26), trans-2-nonenal (82.58-205.58), and trans, trans-2,4-decadial (3.09-21.40) had rOAVs greater than 1, indicating their significant contribution to the aroma of cooked rice, with a significant range of variation. In addition, trans-2-decenal (0.51-1.63), undecanal (0.20-3.58), and trans-2-dodecenal (0.31-3.31) had rOAVs ranging from below to above 1. Aldehydes significantly affected the change in cooked rice aroma after ultrasound, and the ultrasound treatment promoted the oxidative decomposition process of aldehydes during rice cooking. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Aroma Compounds** & **Aroma Characteristics** & **Odor Threshold (\#g/kg)** & \
\begin{tabular}{c} **Before** \\ **Ultrasound** \\ **rOAV** \\ \end{tabular} &
\begin{tabular}{c} **After** \\ **Ultrasound** \\ **rOAV** \\ \end{tabular} \\ \hline
1 & Pentanal &
\begin{tabular}{c} Almond, malt, \\ pungent \\ \end{tabular} & 20 & \textless{}1 & \textless{}1 \\
2 & Hexanal & Grass & 5 & 2.83 & 20.89 \\
3 & Heptanal & Fat, citrus, rancid & 6 & 0.61 & 1.31 \\
4 & Pyridine & Sour, fishy & 2000 & \textless{}1 & \textless{}1 \\
5 & 2-Pentylfuran & Beany & 5.8 & 5.47 & 41.46 \\
6 & 1-Pentanol & Sweet bread & 150.2 & \textless{}1 & \textless{}1 \\
7 & Styrene & Floral & 65 & \textless{}1 & \textless{}1 \\
8 & Octanal & Citrus & 0.8 & 3.30 & 32.90 \\
9 & (E)-2-Heptenal & Fresh, green & 3.75 & 2.97 & 7.41 \\
10 & 6-Methyl-5-heptene-2-one & Citrus & 59 & \textless{}1 & \textless{}1 \\
11 & Tridecane & Sweet & 42,000 & \textless{}1 & \textless{}1 \\
12 & 1-Hexanol & Fruity & 5.6 & 3.50 & 5.08 \\
13 & Nonanal & Citrus & 1.1 & 96.5 & 254.44 \\
14 & (E)-2-Octenal & Cucumber & 3 & 1.23 & 12.26 \\
15 & Decanal & Citrus & 3 & 12.35 & 47.06 \\
16 & (E)-2-Nonenal & Cucumber & 0.19 & 82.58 & 205.58 \\
17 & 1-Octen-3-ol & Raw mushroom & 1.5 & 2.97 & 6.16 \\
18 & (E)-2-Decenal & Citrus & 17 & 0.51 & 1.63 \\
19 & Undecanal & Sweet, floral & 12.5 & 0.20 & 3.58 \\
20 & (E)-2-Dodecenal & Citrus, waxy & 7.3 & 0.31 & 3.31 \\
21 & Geranyl acetone & Fresh, fruity & 186 & \textless{}1 & \textless{}1 \\
22 & (E,E)-2.4-DecaI & Citrus & 2.3 & 21.40 & 3.09 \\
23 & n-Hexadecanol & Floral & 1100 & \textless{}1 & \textless{}1 \\
24 & 2-Pentadecanone & Celery & 7 & 0.44 & 3.55 \\
25 & Pentadecanal & Waxy & 1000 & \textless{}1 & \textless{}1 \\
26 & 2-Methoxy-4-vinylphenol & Smoky & 12.02 & 2.39 & 7.01 \\
27 & Indole & Floral & 40 & 0.38 & 9.48 \\ \hline \hline \end{tabular} Note: The odor threshold is referenced in a book called _Odor Threshold Compilation in Air, Water, and Other Media (Second Edition Expanded and Revised)_. Aroma characteristics accessed from [[http://flavornet.org/flavornet.html](http://flavornet.org/flavornet.html)]([http://flavornet.org/flavornet.html](http://flavornet.org/flavornet.html)) (accessed on 18 February 2025).  
\end{table}