## 4 Conclusions  
This study highlights the need for a reliable analytical method to assess lipid peroxidation products in adult formula, a gap not addressed in prior research. By adopting a previously established method for detecting MDA and ACRL in beverages, we successfully extended it to determine six key analytes--MDA, ACRL, FCHO, ACE, MOO, and DA--in adult formulas. The method showed excellent specificity, precision, and accuracy, achieving low limits of detection and quantification. To our knowledge, this is the first occurrence study of carbonyl compounds in adult formulas. Remarkably, high-protein formulas showed the highest detectability, with 80% of samples quantifiable for MDA, FCHO, and ACRL and 60% quantifiable for ACE and MOO. Standard formulas had a 50% quantification rate for most compounds, while only one special formulation sample, intended for oral or tube feeding, had quantifiable levels of all analytes. The analysis of various adult formula samples revealed significant variations in the levels of carbonyl compounds when stored at different temperatures using HS-SPME-GC-MS. High-protein adult formulas consistently exhibited higher concentrations of these compounds than standard formulas. This suggests that higher protein content may enhance the formation of carbonyl compounds during storage, particularly under elevated temperatures. These findings suggest that the protein content and storage conditions--such as temperature and duration--are critical factors influencing the stability and degradation of these products. The untargeted determination of VOCs by HS-SPME-GC-MS identified a diverse range of compounds, including various aldehydes, ketones, alcohols, and volatile acids. The results indicated that many VOCs accumulate over time, particularly in high-protein adult formulas stored at elevated temperatures. Notably, hexanal, 2-heptanone, and other compounds showed significant increases, suggesting that storage conditions critically affect the stability of these products. The presence of these VOCs, many of which are associated with sensory attributes, emphasizes the importance of understanding their impact on product quality. The findings also suggest that monitoring VOC levels can serve as an indicator of oxidation processes in adult formulas. Our findings suggest that, once opened, adult formula should be stored in its original packaging, protected from light and moisture, and kept away from heat sources such as ovens or central heating. Formulas with higher protein content should ideally be stored in \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Level of Physical**} & **Malondialdehydedehyde** & **Formaldehyde** & **Acetaldehyde** & **Acrolein** & **Methylglyoxal \({}^{\text{a}}\)** & **Diacetyl** \\ \cline{2-13}  & \(\upmu\)g/Kg bw/day & \(\upmu\)g/Kg bw/day & \(\upmu\)g/Kg bw/day & \(\upmu\)g/Kg bw/day & \(\upmu\)g/Kg bw/day & \(\upmu\)g/Kg bw/day \\ \hline  & **M** & **F** & **M** & **F** & **M** & **F** & **M** & **F** & **M** & **F** \\ \hline Low & 53.5 \({}^{\text{*}}\) & 55.3 \({}^{\text{*}}\) & 52.9 & 69.8 & 53.8 & 55.7 & 51.8 \({}^{\text{*}}\) & 53.6 \({}^{\text{*}}\) & 49.8 & 51.5 & 52.5 & 67.7 \\ Moderate & 58.9 \({}^{\text{*}}\) & 61.4 \({}^{\text{*}}\) & 58.3 & 60.8 & 59.3 & 61.8 & 57.1 \({}^{\text{*}}\) & 59.5 \({}^{\text{*}}\) & 54.9 & 57.1 & 57.9 & 60.3 \\ High & 67.9 \({}^{\text{*}}\) & 67.5 \({}^{\text{*}}\) & 67.2 & 66.8 & 68.3 & 67.9 & 65.7 \({}^{\text{*}}\) & 65.4 \({}^{\text{*}}\) & 63.2 & 62.8 & 66.7 & 66.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average daily intake of carbonyl compounds for males and females by activity level. a refrigerator, particularly during the summer or in locations where the room temperature exceeds 25 \({}^{\circ}\)C.  
Furthermore, we assessed the potential risk of exposure to these contaminants based on the estimated consumption of adult formula.