## 4 Discussion  
### Mass Transfer and Water Activity Decrease during OD Processing  
The aim of the study was to investigate the effect of SY Whey (compared to Water) on _WL_, _SG_, and _a\({}_{w}\)_ decrease. OD caused _WL_ and _SG_, up to 11.92 g w/g i.d.m. and 1.91 g s/g i.d.m., respectively,  
Figure 4: Scores for (**a**) color, (**b**) texture, and (**c**) flavor (scale 1–9) of pumpkin cuts (in solution of SY Whey or water) (Index 1: \(\text{OD}_{\text{SY\,Whey}}\) and Index 2: \(\text{OD}_{\text{Water}}\)). Experimental points correspond to isothermal temperature conditions (**a**) 5 \({}^{\circ}\)C, (**a**) 10 \({}^{\circ}\)C, (**b**) 15; lines represent the respective model fit. for both OD\({}_{\text{SY\;Whey}}\) and OD\({}_{\text{Water}}\) samples (Figure 1a,b). In literature, the highest WL and SG value reported for osmotic dehydration of pumpkin was 3 g w. s/g (for both WL and SG; OS: starch syrup or glucose, 30 \({}^{\circ}\)C, 180 min) [42]. In the present study, the use of the multi-component osmotic solution resulted in significantly higher WL and SG values. Glycerol (40% w/w) was the main \(a_{w}\) lowering agent due to its low molecular weight and high humectant effect [43]. WL significantly increased with OD time at each processing temperature (35, 45, and 55 \({}^{\circ}\)C) (Figure 1 a\({}_{1}\)a\({}_{2}\)) (\(p<0.05\)). Higher WL increase was observed with OD temperature increase. Significant differences were calculated for OD processed samples at 35 and 55 \({}^{\circ}\)C (OD\({}_{\text{SY\;Whey}}\) and OD\({}_{\text{Water}}\)) (\(p<0.05\)). The use of SY Whey compared to water did not lead to further water loss (\(p<0.05\)). However, it caused significant increase of solid gain. This increase was more pronounced with OD time and temperature (\(p<0.05\)). Solid gain values were significantly higher for OD\({}_{\text{SY\;Whey}}\) samples at temperatures 45 and 55 \({}^{\circ}\)C (\(p<0.05\)). \(D_{ew}\) and \(D_{es}\) values obtained were similar to values reported in literature for osmotic pumpkin dehydration. According to [PERSON] and [PERSON] [42], \(D_{\text{ew}}\) and \(D_{\text{es}}\) values were in the range of 1.12-1.85 \(\times\) 10\({}^{-9}\) m\({}^{2}\)/s and 6.76-9.74 \(\times\) 10\({}^{-9}\) m\({}^{2}\)/s, respectively. [PERSON], [PERSON], [PERSON], and [PERSON] [33] studied the osmotic dehydration of pumpkin in sodium chloride solution, and observed that \(D_{ew}\) and \(D_{es}\) values (linearly) increased with OD temperature increase ranging between 0.88-1.92 \(\times\) 10\({}^{-9}\) m\({}^{2}\)/s and 1.88-4.22 \(\times\) 10\({}^{-9}\) m\({}^{2}\)/s values, respectively. In the present study, \(D_{ew}\) and \(D_{es}\) values did not present statistically significant differences at temperatures T \(<\) 55 \({}^{\circ}\)C (\(p<0.05\); Table 1). To further express the processing temperature effect on water and solids diffusion, the activation energy values (Equation (5)) were calculated. The activation energy \(E_{a}\) for diffusion during OD ranged from 13.69 (Water) to 15.00 (SY Whey) kJ/mol for water loss and from 19.42 (Water) to 24.45 (SY Whey) kJ/mol (60% w/w) for solids gain showing similar temperature effects on water and solids diffusion for OD\({}_{\text{Water}}\) and OD\({}_{\text{SY}}\) whey samples. The obtained \(E_{a}\) values indicated a low processing temperature effect (in the temperature range of this study) on the diffusion during OD of pumpkin. [PERSON] et al. [30] reported that the diffusivity values calculated during osmotic dehydration of pumpkin for the water and sucrose were similar for 50% and 65% sucrose solutions, using samples previously blanched by both stepwise and conventional means, showing greater solute gain than water loss. An increase of \(D\) values (up to 6.2% and 40.0% for \(D_{ew}\) and \(D_{es}\), respectively) was observed for OD\({}_{\text{SY\;Whey}}\) samples compared to OD\({}_{\text{Water}}\) samples.