# The Effect of Freeze-Drying on the Properties of Polish Vegetable Soups
## 3 Results and Discussion
### The Sorption Properties of Freeze-Dried Soups
It can be concluded that at the higher water activity, the pores of the dried material were filled with absorbed water and a further increase of water activity could lead to a rapid increase of the moisture content in the sample. The material was not able to bind the water due to the limited amount of solid matrix in freeze-dried cucumber soup. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Model** & **Parameter** & **Tomato** & **Beetroot** & **Pumpkin** & **C cucumber** \\ \hline \multirow{6}{*}{GAB 1} & u\({}_{\mathrm{m}}\) & 24.66 & 65.42 & 69.11 & 107.09 \\  & C & 0.33 & 0.2 & 0.17 & 0.06 \\  & k & 0.92 & 0.84 & 0.83 & 0.97 \\  & R\({}^{2}\) & 0.998 & 0.978 & 0.998 & 0.97 \\  & RMS & 14.11 & 20.05 & 15.24 & 47.35 \\  & P & 8.52 & 14.57 & 9.77 & 37.65 \\ \hline \multirow{6}{*}{BET 2} & u\({}_{\mathrm{m}}\) & 11.12 & 8.88 & 18.02 & 68.37 \\  & c & 0.8 & 2.03 & 0.53 & 0.06 \\  & R\({}^{2}\) & 0.996 & 0.96 & 0.992 & 0.972 \\  & RMS & 15.22 & 16.59 & 14.78 & 80.49 \\  & P & 9.77 & 11.78 & 8.49 & 56.34 \\ \hline \multirow{6}{*}{Lewicki 1} & F & 3.13 & 16.73 & 13.29 & 5.23 \\  & G & 1.59 & 0.89 & 0.96 & 1.78 \\  & H & \(-\)35.59 & 4.19 & 3.97 & 6.21 \\  & R\({}^{2}\) & 0.966 & 0.989 & 0.998 & 0.966 \\  & RMS & 48.08 & 18.85 & 14.01 & 35.21 \\  & P & 29.9 & 12.96 & 7.6 & 25.7 \\ \hline \multirow{6}{*}{Peleg 1} & A & 108.81 & 120.44 & 109.87 & 325.43 \\  & B & 19.12 & 5.39 & 17.86 & 2.16 \\  & D & 5.87 & 3.82 & 4.67 & 5.91 \\ \cline{1-1}  & E & 1.29 & 0.26 & 1.13 & 0.04 \\ \cline{1-1}  & R\({}^{2}\) & 0.999 & 0.976 & 0.999 & 0.989 \\ \cline{1-1}  & RMS & 13.16 & 13.14 & 11.89 & 21.31 \\ \cline{1-1}  & P & 7.63 & 9.16 & 6.44 & 16.5 \\ \hline \multirow{6}{*}{[PERSON] 1} & g & 4.12 & 5.9 & 5.48 & 3 \\ \cline{1-1}  & h & 0.77 & 0.81 & 0.81 & 0.58 \\ \cline{1-1}  & R\({}^{2}\) & 0.995 & 0.969 & 0.991 & 0.962 \\ \cline{1-1}  & RMS & 25.51 & 23.32 & 42.68 & 35.69 \\ \cline{1-1}  & P & 15.21 & 17.92 & 23.78 & 29.28 \\ \hline \hline \end{tabular} 1  
\end{table} 
Table 8: Parameters of isotherm sorption models obtained for different freeze-dried soups. The sorption isotherms of many vegetable and vegetable powders followed type II according to [PERSON]'s classification [40, 82, 83]. The procedure and Equation (12) described by [PERSON] and [PERSON] [61] was applied to classify the isotherm sorption of freeze-dried soups. The non-linear regression enabled the obtaining of classification parameters for beetroot and cucumber freeze-dried soups (Table 9). The predicted values for freeze-dried pumpkin and tomato soups were outside the interval of experimental data and the determination coefficients were lower than 0.85. In this case, regression did not lead to obtaining the equation parameters, which can be interpreted physically. The sorption isotherms with parameter \(\chi_{4}\) higher than 0.1, negative value of \(\mathrm{R_{fi}}\), positive value of \(\mathrm{D_{10}}\) and \(\mathrm{a_{wm}}\) from the range of 0-1, can be classified as type IIc, which is closer to the solution-like isotherms at higher \(\mathrm{a_{w}}\). This type of isotherms was observed in the case of fruit and vegetables [61, 84]. The values obtained for beetroot and cucumber freeze-dried soups showed that their isotherms can be classified as type IIc (Table 9). The classification of isotherms can be also performed by plotting \(\mathrm{a_{w}}/\mathrm{w}\) (ratio of water content and water content) against water activity. The shape and course of the curve may indicate the type of isotherms [61]. The curves with extremum obtained for freeze-dried beetroot cucumber soups are characteristic for type II of isotherms (Figure 5). The course of curves obtained for the freeze-dried tomato and pumpkin soup was ambiguous. The decreasing trend of water content with the increase of water activity is typical for isotherm type III, but the shape of the curve slightly deviates from isotherm type III in the range of low water activities.