## 3 Results and Discussion
### Evaluation of Volatile Organic Compounds  
The volatile profiles of the WR and P samples grouped into compound families are shown in Table 3. In both processed rice samples, the largest group was aldehyde compounds. This group decreased with cooking time (from 72.6 to 36.9% for WR, and from 36.4 to 13.8% for P), which can be related to a decrease in the wet cereal aroma of cooked rice, since most aldehydes are associated with positive aromas. [PERSON] et al. [28] indicated that octanal and nonanal aldehydes, among others, were the principal volatile compounds that give cooked rice its aroma. Furthermore, [PERSON] et al. [29] showed that aldehydes such as hexanal, octanal, nonanal, etc., probably contribute the most to the overall flavor because of the low odor threshold. Hydrocarbon compounds, which were the second largest group, are also related to positive aromas [30], and their content decreased with treatment time (from 22.4 to 2.9% for WR and from 5.4 to 0.5% for P). In both cases of aldehyde and hydrocarbon compounds, higher contents were obtained for WR compared to P. This is due to the influence of other aromas from the ingredients added in P, such as vegetables, garlic and shellfish related to sulfutrous compounds [31], which were not found in WR. These sulfutrous compounds appear in greater proportion in P1 (52.5%), and decrease with the processing time up to P4 (15.8%). They decrease due to the appearance of other aromas related to socarrat formation. Furan compounds, related to negative aromas such as roasted and woody [31], appear with greater intensity in the last sampling times for WR and P. Similarly, pyrazine compounds are related to roasted aromas [32], and high-fired aromas [33] and their contents increase with processing time. Regarding the alcohol group, it can be related to different aromas such as toasted [34], shellfish [35] and floral sweets [36]. In general, the content of alcohol compounds increases with processing time, which is mainly due to the appearance of toasted aromas. In paella rice this increase is more significant (from 4.5 to 23.3% for P1 to P4) than white rice (from 5.0 to 12.3 for WR1 to WR4), which is possibly due to the socarrat formation that is associated with the formation these aromas. Finally, ketone and furanone compounds appear in appreciable amounts for  
Figure 1: Acrylamide content (expressed in ng g\({}^{-1}\)) of white rice (WR) and paella (P) submitted to different thermal treatments (1–4) during the cooking process. Results are expressed as mean \(\pm\) SD of five sample replicates. Different lowercase letters mean a significant difference between each elaboration process (WR and P) submitted to different thermal treatments. Different uppercase letters mean a significant difference between white rice and paella in each thermal treatment. the last processing time. This is in accordance with the roasted and pungent aromas [37] provided by ketones, as well as bitter-caramel aromas [38]. A total of 33 volatile compounds were analyzed (Table 3). In the alcohol group, heptane and o-xylene, which are related to sweet [39] and petroleum-like [40] aromas, appeared in WR but decreased with the heat treatment time. However, they did not appear in P, probably due to other ingredients that mask these aromas. D-limonene, which is related to a sweet orange aroma [41], appeared in both rice samples.