## 3 Results
### Evolution of Selected Quality Indices of OD-Treated Tomato and Spinach-Based RTE Products
#### 3.4.2 OD-Treated Spinach-Based RTE Product: Spinach Color and Texture  
A temperature-dependent color deterioration was observed in the OD-treated spinach leaves, which was more pronounced for OD-treated samples. This color change was attributed to both a reduction in sample lightness due to enzymatic browning, and to a degradation of chlorophylls to pheophytins. In fact, this deterioration is favored under acidic pH which is the case with osmotically dehydrated spinach. The evolution of the total color difference (\(\Delta E\)) in spinach samples at all treatments with storage time is presented in Figure 7a and it was found to be significantly correlated (negative correlation) with the intensity of the green color score using the Pearson s test (Table 6). Figure 7b presents the evolution of the relative burst strength of OD-treated spinach samples with storage time at all storage temperatures studied. For all treatments, it was observed that the burst strength of the spinach leaves increased with storage time. This effect was more pronounced when an OD treatment was performed with the relative burst strength of the treated leaves, almost doubling after 25 days of storage. Macroscopically, this can manifest as an increased elasticity and gumminess of the leaves, which was confirmed via the sensory evaluation of the samples. Due to the loss of water during storage (untreated samples) or dehydration (OD-treated samples), the fibers in the plant tissue become compacted, leading to an increased mechanical strength of the tissue [47]. This behavior of the relative burst strength was detected by the panelists and it was positively correlated with the intensity of the perceived gumminess score.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{4}{c}{**OD-tomatoes of the tomato-based RTE product**} \\ \hline \hline  & **Total color difference** & **Intensity of red color** & **Relative firmness (F/F\({}_{0}\))** & **Intensity of perceived** \\ \hline Total color difference (\(\Delta E\)) & & \(-\)0.854 ** & \(-\)0.803 ** & \(-\)0.289 \\ Intensity of red color & \(-\)0.854 ** & & 0.877 ** & 0.220 \\ Relative firmness (\(F/F_{0}\)) & \(-\)0.803 ** & & & \(-\)0.031 \\ Intensity of perceived firmness & \(-\)0.289 & 0.220 & \(-\)0.031 & \\ \hline \hline \multicolumn{4}{c}{**OD-spinach of the spinach-based RTE product**} \\ \hline \hline  & **Total color difference** & **Intensity of green color** & **Relative firmness (F/F\({}_{0}\))** & **Intensity of perceived** \\  & **(\(\Delta E\))** & **green color** & **(F/F\({}_{0}\))** & **gumminess** \\ \hline Total color difference (\(\Delta E\)) & & \(-\)0.697 ** & 0.720 ** & 0.630 ** \\ Intensity of green color & \(-\)0.697 & & \(-\)0.740 ** & \(-\)0.888 ** \\ Relative firmness (\(F/F_{0}\)) & 0.720 ** & \(-\)0.740 ** & & 0.786 ** \\ Intensity of perceived gumminess & 0.630 ** & \(-\)0.888 ** & 0.786 ** & \\ \hline \hline \end{tabular}  
* Significant correlation at level of \(p\) = 0.01.  
\end{table}
Table 6: Correlation matrix of Pearson coefficients of total color difference (\(\Delta E\)), intensity of red or green color, relative firmness (\(F/F_{0}\)), and intensity of perceived firmness or gumminess.  
Figure 7: Evolution of (**a**) the total color difference (\(\Delta E\)) and (**b**) the relative burst strength of OD-treated spinach samples with storage time at storage temperatures 4, 8, 12, and 20 \({}^{\circ}\)C.