## 3 Results and Discussion
### Effect of Independent Values on Mass Transfer Variables (a\({}_{w}\), WL, SG, and %MC)  
The interaction effect of independent variables (glycerol concentration, OD temperature, and duration of osmosis) on the response can be better illustrated by a 3-dimensional (3D) surface graph, applying a color spectrum. The highest values are represented by the dark red color, intermediate values by the yellow, and the lowest values by the dark green color. The three-dimensional response surface graphs depict the combined effect of the independent variables (time, temperature, and OD solution concentration) on the dependent variables studied. In these graphs, plots are constructed as a function of two variables while keeping the third variable constant (at the central value, as presented in Table 1). The interactions of glycerol concentration and osmosis time at 40 \({}^{\circ}\)C on %moisture content (%MC), water activity (a\({}_{\text{w}}\)), water loss (WL), and solid gain (SG) are shown in Figure 1. The graphs illustrate that %MC and a\({}_{\text{w}}\) decrease significantly as the glycerol concentration increases, with samples which were treated with 50% glycerol reaching the lowest values. Samples treated with 30, 40, and 50% glycerol showed, after 130 min of osmosis, %MC values of 66.73%, 59.79%, and 48.25% (%wb), respectively, and water activity values of 0.8978, 0.8631, and 0.7971, respectively. In general, water activity and moisture content decreased as the OD solution glycerol concentration increased, and the processing  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & **a\({}_{\text{w}}\) (CP)** & \begin{tabular}{c} **a\({}_{\text{w}}\)** \\ _(\(p\)-Value)_ \\ \end{tabular}  & **WL (CP)** & \begin{tabular}{c} **WL** \\ _(\(p\)-Value)_ \\ \end{tabular}  & **SG (CP)** & \ \begin{tabular}{c} **SG** \\ _(\(p\)-Value)_ \\ \end{tabular}  & **\%MC (CP)** & \begin{tabular}{c} **\%MC** \\ _(\(p\)-Value)_ \\ \end{tabular}  \\ \hline a\({}_{0}\) & 1.25 * & 0.00000 & 15.0 * & 0.0436 & \(-\)1.32 * & 0.0485 & 103 * & 0.00301 \\ a\({}_{1}\) & \(-\)0.0230 * & 0.00350 &  
time led to higher water removal. The same results were reported by [55] on osmotically dehydrated cheese with glycerol. Water loss and solid gain values increased during osmotic dehydration. After 130 min of osmosis, the highest WL value was 5.36 g/100 g, and the lowest value was 4.25 g/100 g, which can be observed in the samples that were treated with 50% glycerol and 30% glycerol, respectively. Correspondingly, the highest SG value were 4.05 g/100 g, and the lowest value was 2.14 g/100 g, in samples that were treated with 50% glycerol and 30% glycerol, respectively. The increase in SG and WL with the increase in glycerol concentration could be attributed to the high concentration difference between the mushroom piece and the osmotic solution. The results are in agreement with [55; 56; 57]. The interactions of glycerol concentration and osmosis time at 40% glycerol on %moisture content (%MC, wb), water activity (a\({}_{\text{w}}\)), water loss (WL), and solid gain (SG) are shown in Figure 2. It can be observed that there is no significant change on %MC as the temperature and the time increase. Small changes can be observed on a\({}_{\text{w}}\) values as the temperature changes, with the lowest values for samples that were treated at 30, 40, and 50 \({}^{\circ}\)C being 0.9199, 0.8672, and 0.8612, respectively, after 130 min. WL and SG decrease and then increase as the temperature increases. The lowest values for both WL and SG are observed in the samples treated at 40 \({}^{\circ}\)C at 130 min. Figure 1: 3D response surface graphs of the effect of OD time and glycerol concentration at constant temperature (40 \({}^{\circ}\)C) on (**a**) % moisture content (%MC, wb), (**b**) water activity (a\({}_{\text{w}}\)), (**c**) water loss (g of water/100 g, WL), and (**d**) solid gain (g of solute/100 g, SG). All mass transfer phenomena showed a rapid change in the early phase of osmosis, and then the rate decreased.