## 3 Results and Discussion
### Changes in Volatile Compounds  
Volatile organic compounds can be sorted into various categories including acids, alcohols, and aldehydes. Each of these groups contributes to the distinct flavors found in meat [46]. A total of 83 volatile compounds were detected in the sous vide-cooked horse loin and are summarized based on cooking duration and temperature in Table 5. These \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**R**} & \multirow{2}{*}{**C**} & \multicolumn{3}{c}{**65 \({}^{\circ}\)C**} & \multicolumn{3}{c}{**70 \({}^{\circ}\)C**} & \multirow{2}{*}{**SEM**} \\ \cline{3-3} \cline{5-10}  & & **12 H** & **18 H** & **24 H** & **12 H** & **18 H** & **24 H** & \\ \hline Total aerobic bacteria & 2.84 \({}^{\text{a}}\) & 0.00 \({}^{\text{b}}\) & 0.00 \({}^{\text{b}}\) & 0.00 \({}^{\text{b}}\) & 0.17 \({}^{\text{b}}\) & 0.00 \({}^{\text{b}}\) & 0.00 \({}^{\text{b}}\) & 0.00 \({}^{\text{b}}\) & 0.00 \({}^{\text{b}}\) & 0.608 \\ Coliforms & N.D. & N.D. & N.D. & N.D. & N.D. & N.D. & N.D. & N.D. & N.D. & - \\ _E. coli_ & N.D. & N.D. & N.D. & N.D. & N.D. & N.D. & N.D. & - \\ \hline \hline \end{tabular}  
* R, raw meat C, control (boiled at 72 \({}^{\circ}\)C for 40 min).
* Means within same row with different superscript letters differ significantly (\(p<0.05\)). SEM, standard error of means. N.D, not detected.  
\end{table} 
Table 4: The change in microbiology (Log CFU/g) for raw and horse loin cooked sous vide at different conditions. Figure 2: Myofibrillar protein profile (SDS-PAGE) of raw and horse loin cooked sous vide at different conditions. M, size marker. R, raw meat. C, control (boiled at 72 \({}^{\circ}\)C for 40 min). volatile compounds were categorized into the following chemical families: 7 alcohols, 24 aldehydes, 15 esters, 25 hydrocarbons, and 12 ketones. The total number of compounds detected differed slightly from those found in previous horse meat (foal) samples [47; 48]. Hydrocarbon compounds were the most abundant, with 1-octen-3-ol being the most prominent alcohol known for its distinctive aroma, which is reminiscent of fishiness, fattiness, mushrooms, and grassiness [49]. Decanal dominated the aldehyde category, imparting soap and orange-peel aromas [50], as well as a tallow-like scent. Among the esters, n-capric acid vinyl ester was the most prevalent, whereas cyclotetrasiloxane and octamethyl were the leading compounds in the hydrocarbon category. The most abundant ketone was 3,3-Dimethyl-1,2-epoxybutane. These volatile compounds originate from the breakdown of lipids (alcohols, aldehydes, hydrocarbons, and ketones) or the Maillard reaction [48]. Trends in VOCs resulting from lipid degradation exhibited similar patterns under varying temperatures and cooking conditions. For alcohols, aldehydes, and ketones, the highest values were observed in samples cooked at 65 \({}^{\circ}\)C for 18 h, and the lowest levels were observed in those cooked at 70 \({}^{\circ}\)C for 24 h. In contrast, for hydrocarbons, the highest level was found at 65 \({}^{\circ}\)C for 12 h, and the lowest at 70 \({}^{\circ}\)C for 12 h. The raw meat was also analyzed for volatile compounds to distinguish the aroma changes between before and after heat treatment. The process of heating results in the production of new molecules, mostly from lipid oxidation and Maillard browning processes, which are collectively responsible for the desired flavor of the meat. The heating and long cooking processes promote the breakdown of polyunsaturated fatty acids, including linoleic acid, resulting in the development of additional VOCs (octanal, heptanal, 2-octanone, and nonanal) during the late stages of lipid oxidation; some of these carbonyl compounds may interact with amino acids such as lysine, cysteine, and glutathione [7].