# Effect of Ultrasonic Treatment on Taste and Flavor Quality of Japonic Rice
## 3 Results
### GC-MS Data Analysis
#### 3.5.2 Aroma Characteristics  
To further analyze the differences in volatile compounds between samples, heat maps were plotted for 65 volatile compound contents in five samples of cooked Japonica rice under different ultrasound treatments (Figure 7). The color scale of the heat map was generated using normalized data on the horizontal axis, where blue and red represent minimum and maximum, respectively, clearly differentiating the different levels of content. Hydrocarbons were the main volatile compounds detected in ultrasound treatment cooked Japonica rice, leading to an increase in the overall concentration of volatile compounds. These hydrocarbons mainly originated from the oxidation and degradation of lipids [13]. Nevertheless, only a small number of alkanes produced distinctive aromas, which had a minimal effect on the overall aroma of cooked Japonica rice. For instance, tridecane, tetradecane, and styrene contributed to sweet aromas, floral aromas, and a blend of sweet and floral aromas, respectively [23]. However, other hydrocarbons slightly influenced the total aroma profile [24]. In addition, trace amounts of heterocyclic compounds were detected in cooked Japonica rice, with their concentrations significantly increasing as ultrasound treatment time was extended. Among the volatile compounds, 2-pentylfuran, the main alkylfuran in cooked rice, was detected in every cooked Japonica rice sample, with its concentration increasing significantly with increased ultrasound treatment time, offering a fruity, nutty, and caramel aroma [23]. Moreover, pyridine and indole were detected in the ultrasound treatment cooked Japonica rice samples, contributing floral notes, while 2,3-dihydroenzofuran was detected in the cooked rice samples, adding sweetness to the overall aroma [25]. A total of 23 aldehydes were detected in this study, among which nonanal was the highest and was found in all treated samples. The oxidative decomposition of lipids in cooked rice was the primary pathway for the formation of aldehydes. Most of them had  
Figure 7: After various ultrasound procedures in different cooked Japonica rice, heat map analysis of volatile compounds was conducted. high roAVs and contributed to the aroma of cooked rice, presenting fruity, sweet, and grassy notes. Octanal is a lipid oxidation product of linoleic and oleic acids, whereas decanal is an oxidation product of oleic acid [26]. Aldehydes primarily exhibited fruity, sweet, and grassy aromas. Hexanal and 2-butyl-2-octenal were selected as odor identification markers for cooked rice [27]. The remaining aldehydes, including benzaldehyde and trans-2, 4-decadienal, exhibited a fatty aroma and nutty aromas. These compounds significantly influenced the aroma of cooked rice. The concentration of aldehydes varied after ultrasound treatment. The increase in concentration might be attributed to the ultrasound treatment process that enhanced the dispersion of lipids in the sample and promoted certain oxidative pathways. In contrast, the decrease in concentration was attributed to the binding of lipids and starch, which inhibits their oxidative decomposition process. High concentrations of aliphatic aldehydes, such as hexanal, negatively affected the aroma of cooked rice, resulting in an unpleasant odor [27]. However, the reduction in the concentration of some aldehydes diminished their negative effect on the aroma of cooked rice. A range of alcohols and ketones were also identified within the volatile compounds extracted from ultrasonically processed cooked Japonica rice. Alcohols, which are secondary metabolites, are formed through the oxidation of unsaturated fatty acids that result from the subsequent breakdown of aldehydes. Ketones are derived from the oxidative degradation of unsaturated fatty acids and the degradation or synthesis of amino acids [28]. At different intensities of ultrasound treatment, the levels of alcohol remained relatively constant.