## 3 Results and Discussion
### Changes in Instrumental Texture
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**C**} & \multicolumn{4}{c}{**65 \({}^{\circ}\)C**} & \multicolumn{4}{c}{**70 \({}^{\circ}\)C**} & \multirow{2}{*}{**SEM**} & **P** & **P** & **P** \\ \cline{3-3} \cline{5-10}  & & **12 h** & **18 h** & **24 h** & **12 h** & **18 h** & **24 h** & **(T)** & **(t)** & **(T’t)** \\ \hline Shear force (N) & 52.64 \({}^{\circ}\) & 50.72 \({}^{\text{ab}}\) & 44.65 \({}^{\text{ab}}\) & 36.36 \({}^{\text{b}}\) & 50.57 \({}^{\text{ab}}\) & 44.45 \({}^{\text{ab}}\) & 35.70 \({}^{\text{b}}\) & 3.426 & 0.9080 & 0.0012 & 0.9969 \\ Hardness (N) & 165.78 & 142.72 & 151.83 & 130.29 & 158.79 & 131.98 & 140.66 & 10.984 & 0.8164 & 0.4217 & 0.2607 \\ Cohesiveness & 0.45 \({}^{\text{a}}\) & 0.37 \({}^{\text{bc}}\) & 0.41 \({}^{\text{ab}}\) & 0.38 \({}^{\text{bc}}\) & 0.41 \({}^{\text{abc}}\) & 0.38 \({}^{\text{bc}}\) & 0.36 \({}^{\text{c}}\) & 0.012 & 0.6640 & 0.0889 & 0.0108 \\ Springiness (cm) & 0.76 \({}^{\text{b}}\) & 0.89 \({}^{\text{ab}}\) & 0.73 \({}^{\text{b}}\) & 0.95 \({}^{\text{a}}\) & 0.87 \({}^{\text{ab}}\) & 0.94 \({}^{\text{a}}\) & 0.93 \({}^{\text{a}}\) & 0.036 & 0.0217 & 0.0074 & 0.0003 \\ Gumminess (N) & 76.64 \({}^{\text{a}}\) & 54.24 \({}^{\text{abc}}\) & 67.77 \({}^{\text{abc}}\) & 49.93 \({}^{\text{abc}}\) & 74.44 \({}^{\text{ab}}\) & 47.91 \({}^{\text{bc}}\) & 46.05 \({}^{\text{c}}\) & 6.417 & 0.8334 & 0.0690 & 0.0212 \\ Chewiness (N) \({}^{\text{NS}}\) & 56.76 & 52.78 & 48.81 & 46.46 & 66.28 & 44.65 & 40.87 & 6.672 & 0.8281 & 0.0711 & 0.3289 \\ MFI & 41.15 \({}^{\text{b}}\) & 50.75 \({}^{\text{ab}}\) & 50.78 \({}^{\text{ab}}\) & 47.59 \({}^{\text{ab}}\) & 55.03 \({}^{\text{a}}\) & 56.71 \({}^{\text{a}}\) & 52.49 \({}^{\text{a}}\) & 2.413 & 0.0145 & 0.2789 & 0.9405 \\ \hline \hline \end{tabular} \({}^{\text{NS}}\) Non-significant. C, control (boiled at 72 \({}^{\circ}\)C for 40 min). \({}^{\text{a}\text{}\text{}\text{}\text{}\text{}\text{}\text{}\text{}\text{}\text{ }\text{}\text{}\text{}\text{}\text{}\text{}\text{}\text{}\text{}\text{}\)}\) Means within the same row with different superscript letters differ significantly (\(p\) < 0.05). SEM, standard error of means. T, temperature. t, time. T’t, The interaction between cooking time and temperature.  
\end{table} 
Table 3: Instrumental texture parameters (shear force values and TPA) and MFI of horse loin cooked sous vide at different conditions. Meat tenderness during cooking is associated with heat exposure. Heat solubilizes connective tissue, thereby increasing meat tenderness; however, the denaturation of myofibrillar proteins may result in tough meat [39]. Additionally, water loss from the muscle tissue upon heating contributes to meat toughening. The transition from a viscoelastic material to an elastic material also influences texture changes during heating [12]. Raw meat is difficult to chew because of the high viscosity flow between fibers, but heating to 65 \({}^{\circ}\)C improves tenderness, as sarcoplasmic proteins bind together to form a gel, making it accessible for chewing [12]. However, temperatures exceeding 65 \({}^{\circ}\)C up to 80 \({}^{\circ}\)C result in tough meat due to an increased elastic modulus [40]. After 6 h, the residual collagenolytic activity at 60 \({}^{\circ}\)C may explain the tenderness of meat cooked at these temperatures for extended periods [12]. Our study observed a tendency for the hardness and shear force to decrease with a prolonged cooking duration. This phenomenon could be attributed to the increased solubilization of collagen during extended cooking duration, whereas myofibrillar shrinkage may have already reached its maximum and showed no further significant increase over increased durations. The enhanced tenderness observed during the extended cooking of horse loin in our study, as indicated by the shear force and TPA values, may be attributed to the extensive breakdown of the perimysium surrounding the muscle bundles [12].