## 3 Results
### Oxidative Stability
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & & \multicolumn{6}{c}{**Time (days)**} \\ \hline  & & **7** & **14** & **21** & **28** & **35** & **42** \\ \hline Aldehydes & FFA & 71.3 \(\pm\) 3.2 & 60.2 \(\pm\) 2.0 & 56.6 \(\pm\) 1.8 & 52.6 \(\pm\) 1.3 & 53.8 \(\pm\) 1.5 & 50.6 \(\pm\) 1.6 \\  & IFA & 80.1 \(\pm\) 2.8 & 58.7 \(\pm\) 1.8 & 49.1 \(\pm\) 1.1 & 49.7 \(\pm\) 1.4 & 49.7 \(\pm\) 1.3 & 45.8 \(\pm\) 1.4 \\ \hline Ketones & FFA & 2.4 \(\pm\) 0.5 & 6.6 \(\pm\) 0.8 & 4.1 \(\pm\) 0.5 & 3.3 \(\pm\) 0.6 & 3.4 \(\pm\) 0.6 & 3.6 \(\pm\) 0.5 \\  & IFA & 11.9 \(\pm\) 1.0 & 16.2 \(\pm\) 1.0 & 24.0 \(\pm\) 1.0 & 23.6 \(\pm\) 0.9 & 23.8 \(\pm\) 0.9 & 26.3 \(\pm\) 1.0 \\ \hline Alcohols & FFA & 12.6 \(\pm\) 1.1 & 11.8 \(\pm\) 0.9 & 12.7 \(\pm\) 0.9 & 12.0 \(\pm\) 0.8 & 11.8 \(\pm\) 0.7 & 10.3 \(\pm\) 0.1 \\  & IFA & 6.0 \(\pm\) 0.5 & 4.0 \(\pm\) 0.4 & 5.3 \(\pm\) 0.1 & 5.4 \(\pm\) 0.2 & 4.9 \(\pm\) 0.4 & 4.5 \(\pm\) 0.1 \\ \hline Alkylfurans & FFA & 2.9 \(\pm\) 0.3 & 5.8 \(\pm\) 0.5 & 6.0 \(\pm\) 0.2 & 5.6 \(\pm\) 0.1 & 4.9 \(\pm\) 0.5 & 5.2 \(\pm\) 0.2 \\  & IFA & 0.8 \(\pm\) 0.0 & 8.7 \(\pm\) 0.3 & 9.7 \(\pm\) 0.3 & 10.2 \(\pm\) 0.3 & 9.8 \(\pm\) 0.3 & 13.1 \(\pm\) 0.5 \\ Hydrocarbons & FFA & 0.5 \(\pm\) 0.0 & 1.6 \(\pm\) 0.5 & 2.5 \(\pm\) 0.5 & 1.8 \(\pm\) 0.5 & 1.7 \(\pm\) 0.2 & 3.3 \(\pm\) 0.3 \\  & IFA & 1.2 \(\pm\) 0.1 & 7.2 \(\pm\) 0.7 & 5.2 \(\pm\) 0.2 & 4.6 \(\pm\) 0.5 & 5.7 \(\pm\) 0.3 & 6.1 \(\pm\) 0.4 \\ \hline Carboxyl acids & FFA & 0.7 \(\pm\) 0.0 & 1.5 \(\pm\) 0.4 & 2.7 \(\pm\) 0.1 & 7.2 \(\pm\) 0.3 & 6.7 \(\pm\) 0.4 & 9.2 \(\pm\) 0.6 \\  & IFA & - & - & - & - & - & - \\ \hline Others’ & FFA & 9.7 \(\pm\) 0.9 & 12.5 \(\pm\) 1.0 & 15.6 \(\pm\) 1.1 & 17.3 \(\pm\) 1.2 & 17.5 \(\pm\) 1.2 & 17.8 \(\pm\) 1.2 \\  & IFA & - & 5.2 \(\pm\) 0.4 & 6.7 \(\pm\) 0.5 & 6.4 \(\pm\) 0.5 & 6.2 \(\pm\) 0.4 & 4.2 \(\pm\) 0.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main categories of volatile compounds in FFA and IFA during heating (area percentage, mean value \(\pm\) SD). Figure 4: Peroxide values (PV, mean value \(\pm\) SD) of FFA (free fatty acid; OLLn) and IFA (intercalated fatty acid; MgAl-OLLn) series during heating. Among alcohols, 1-penten-3-ol and 1-pentanol, typical autoxidation products of linoleic and \(\alpha\)-linolenic acids [8], were produced during the heat treatments of FFA and IFA, whereas 3-exen-2-one and 3,5-ocatadien-2-one were detected among ketones in both series. The results of Table 2 show that the maximum value for the aldehyde category was observed after seven days of treatment, both for FFA and IFA series; then, this value decreased with the increase in the heating time (42 days). Figure 5 shows the aldehydes grouped as saturated (S), monounsaturated (M), and polyunsaturated (P) for FFA and IFA series. It can be observed that monounsaturated aldehydes are the most represented in the FFA category, whereas saturated aldehydes are the most represented in the IFA category. Aldehydes, among all the compounds derived from the oxidation process, are considered the most important breakdown products and the largest contributors to flavor [33; 34]. It has been reported that saturated aldehydes are more stable than unsaturated aldehydes [35], and that unsaturated aldehydes can be further oxidized and additional volatile products may be formed [34]. Regarding the aldehydes in both FFA and IFA series, hexanal, octanal, nonanal, and decanal were detected among saturated aldehydes, whereas 2-butenal, _trans_-2-pentenal, _trans_-2-2-pentenal, _trans_-2-ocrenal, _trans_-2-nonenal, _trans_-2-decrenal and _trans_, _trans_-2,4-esadienal, _trans_, _trans_-2,4-epatdienal and _trans_, _trans_-2,4-nonadienal were the main unsaturated aldehydes. Propanal, pentanal, and heptanal were detected among the compounds identified in saturated aldehydes from IFA. Propanal is a typical volatile compound from \(\alpha\)-linolenic acid oxidation, whereas pentanal and heptanal originated from the decomposition of linoleate 13- and 11-hydroperoxides.