## 3 Results and Discussion
### Volatile Profiles of Raw and Cooked Rice Samples
Although the perceived aroma of particular rice after cooking is the outcome of the combined effects of all the aromatic volatiles present, the odor predominance may be skewed towards the effect of the most dominant volatile compounds present. Amongst the rice varieties studied here, 2-AP was the most dominant compound found only in Pusa 1652 (Improved Kala Namak) and Kala Namak 2. Given the unique potential of Pusa 1652 (Improved Kala Namak), as a novel source of enhanced aroma due to the detection of very high levels of 2 AP and other volatile signatures found in this improved Kalanamak variety, the genetics of improved aroma signatures of Pusa 1652 need to be deciphered  
Figure 2: Principal component analysis (PCA) score plots of volatile compounds in (**a**) raw and (**b**) cooked rice samples of ten different traditional and improved varieties. in future studies. The second dominant compound in these two rice samples was ethyl hexanoate and 1-hexanol, characteristic for a fruity apple and green herbaceous woody odor, respectively. Four of the rice varieties studied, Pusa Basmati-1, Kala Jeera, Kala Namak-1, and Kala Nuniya, had 1-hexanol as the most dominant volatile compound, whereas two others, Pusa Basmati 1509 and Govind Bhog, had ethyl hexanoate as the most dominant volatile compound. The findings of this study collectively confirmed that several of the aromatic traits of traditional varieties exhibited a Basmati-like aroma which was equivalent to or superior to Basmati rice. Jeera 32 is the only rice variety studied that stood unique, with ethyl benzoate present as the most dominant volatile compound. These results point out the importance of deploying the targeted and untargeted metabolomics techniques to identify the important donor lines with very high level of 2 AP and unique aroma signatures to be deployed for future breeding to diversify aroma and to maintain the stability of aroma. It would be interesting to see if a descriptive sensory panel-based study will categorize these rice varieties in a manner similar to the differentiation based on the effect of dominant volatile compounds present after cooking. The heatmap of the correlation matrix was plotted to understand the relationship between volatile compounds in raw and cooked rice samples (Figure 3). In the correlation heatmap, red-colored squares indicate positive corrections, and compounds in blue-colored squares showed negative or non-significant correlations. A strong positive correlation was found in raw rice samples between 1-hexanol and ethyl 3-hydroxybutyrate, nonanoic acid, ethyl ester, and 2,3-butanediod, 2-AP and 1-octen-3-ol (Figure 3a). These findings showed that with 2-AP, 1-octen-3-ol might contribute to the perceived scent of raw aromatic rice samples, as reported in the previous study [28]. Conversely, a strong negative correlation was observed among tetradecanoic acid, ethyl ester, and phenylethyl alcohol. Figure 3: Heatmap of correlation matrix of the volatile compounds in (**a**) raw rice and (**b**) cooked rice of ten different traditional and improved varieties. Red-colored squares indicate positive correlations and blue-colored squares denote negative correlation. A strong positive correlation was observed between ethyl benzoate and ethyl benzeneacetate in cooked rice, which indicates they may be formed together during the cooking process. 2-AP showed moderate to high correlations with ethyl benzoate, ethyl benzeneacetate, ethyl butyrate, ethyl 3-methylbutanoate and phenylethyl alchohol, ethyl 3-hydroxybutyrate, and indole, which demonstrates the role of these volatile compounds to the perceived aroma of cooked aromatic rice samples (Figure 3b). The observed moderate to the high correlation of 2-AP with ethyl benzoate, benzene acetic acid, ethyl ester, ethyl butyrate, ethyl 3-methylbutanoate, and phenylethyl alchohol, ethyl 3-hydroxybutyrate, and indole in cooked rice suggests the role of these compounds in the overall perceived characteristic Basmati-like aroma in cooked rice.