# Volatile Composition of Smoked and Non-Smoked Iranian Rice
## Results
### Volatile Compositions of Non-Smoked and Smoked Iranian Rice  
The volatile profile of non-smoked rice was dominated by only five compounds: tetradecane (32.9%), hexanal (17.6%), benzaldehyde (14.0%), \(p\)-ethylguaiacol (13.7%), and nonanal (9.9%) (Table 3); the concentrations of these compounds were higher than those in the non-smoked samples. Most of the compounds found in non-smoked rice samples were already found in California long-grain rice by [PERSON] et al. [23], as early as1988, and later confirmed in other studies [24; 25]. In this way, [PERSON] et al. also obtained similar results by concluding that the major compounds identified in Iranian rice were alkyl aldehydes [10].  
However, the application of smoking as a post-harvest unit operation significantly increased the concentrations of several compounds, including furfural (26.7%), guaiacol (11.3%), phenol (8.1%), 2-methoxy-4-methylphenol (7.0%), \(p\)-cresol (5.4%), 5-methyl-furfural (4.4%), and 2-acetylfuran (1.9%). These results agreed quite well with the data provided by [PERSON] [26], who reported that the main compounds (concentrations above 5% GC area) in the smoke flavoring from rice husk were: 2-furfural, phenol, 2-methoxyphenol, 4-ethyl-2-methoxyphenol, and 2,3-dimethoxyophenol.  
Table 4 shows the total contents (%) of the main chemical families found in non-smoked and smoked rice samples. Consequently, it can be concluded that the volatile profiles of non-smoked rice were controlled by aldehydes (46.5%) and linear hydrocarbons (33.3%), while those of smoked samples were dominated by phenol derivatives (44.9%) and furans (35.6%).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**SADOVA \({}^{\dagger}\)**} & \multicolumn{2}{c}{**Non-Smoked Rice**} & \multicolumn{2}{c}{**Smoked Rice**} \\ \cline{3-5}  & & \multicolumn{2}{c}{**Relative Abundance (\%)**} \\ \hline
2-Methylfuran & * & 0.29 \(\pm\) 0.08 \(\dagger\) b\({}^{\dagger}\) & 0.41 \(\pm\) 0.01 a \\ Hexanal & *** & 17.6 \(\pm\) 2.5 a & 2.50 \(\pm\) 0.36 b \\
3-Furfaldehyde & * & 0.11 \(\pm\) 0.02 b & 0.26 \(\pm\) 0.08 a \\ Furfural & *** & 0.14 \(\pm\) 0.03 b & 2.67 \(\pm\) 2.4 a \\
2-Heptanone & ** & 0.49 \(\pm\) 0.14 a & 0.06 \(\pm\) 0.02 b \\ Heptanal & * & 0.46 \(\pm\) 0.02 a & 0.30 \(\pm\) 0.08 b \\
2-Methyl-2-cyclopent-1-one & * & 0.06 \(\pm\) 0.01 b & 0.26 \(\pm\) 0.07 a \\
2-Acetylfuran & *** & 0.07 \(\pm\) 0.01 b & 1.91 \(\pm\) 0.24 a \\ Anisole & * & 0.17 \(\pm\) 0.07 b & 0.29 \(\pm\) 0.08 a \\
5-Methyl-furfural & *** & 0.22 \(\pm\) 0.13 b & 4.39 \(\pm\) 0.50 a \\ Benzaldehyde & *** & 14.0 \(\pm\) 2.9 a & 2.69 \(\pm\) 0.10 b \\ Phenol & *** & 0.22 \(\pm\) 0.06 b & 8.03 \(\pm\) 0.14 a \\
6-Methyl-5-hepten-2-one & NS & 0.45 \(\pm\) 0.15 & 0.38 \(\pm\) 0.09 \\
2-Amylfuran & * & 0.33 \(\pm\) 0.11 b & 1.03 \(\pm\) 0.30 a \\ Octanal & * & 0.91 \(\pm\) 0.12 a & 0.55 \(\pm\) 0.10 b \\ \hline \hline \end{tabular} \({}^{\dagger}\) RT = retention time, \(\mathrm{I}^{\dagger}\) = linear retention indexes, Exp = experimental, and Lit = Literature; \({}^{\ddagger}\) SAFC [22].  
\end{table}
Table 3: Comparative composition of volatile compounds, by GC-FID, of smoked and non-smoked Iranian rice.