## 3 Results and Discussion
### Dry Matter, Water Activity, and Tissue Density Changes after Pretreatments and Drying
During drying, tissue shrinkage occurred, leading to a decrease in the specific surface area of the sample, an increase in apparent density, and a decrease in porosity. Blanching resulted in a minor reduction in material shrinkage, approximately 3 percentage points compared to untreated tissue. However, an increase in pretreatment duration generally led to increased tissue shrinkage, except for ultrasound treatment at \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{4}{c}{**After Pretreatments**} & \multicolumn{4}{c}{**After Pretreatments and Drying**} \\ \cline{2-9}  & **Dry Matter** & **Water Activity** & **Density** & **Dry Matter** & **Water Activity** & **Density** & **Shrinkage** \\  & **Content [\%]** & **a\({}_{\textbf{w}}\)[-]** & **[g/cm\({}^{3}\)]** & **Content [\%]** & **a\({}_{\textbf{w}}\)[-]** & **[g/cm\({}^{3}\)]** & **[\%]** \\ \hline Untreated & 14.85 \(\pm\) 0.1 & 0.997 \(\pm\) 0.001 & 0.993 \(\pm\) 0.007 & 92.0 \(\pm\) 1.4 & 0.377 \(\pm\) 0.008 & 1.386 \(\pm\) 0.182 & 83.5 \(\pm\) 0.1 \\  & d \({}^{*}\) & b & c & b & bc & cd \\ Blanched & 12.77 \(\pm\) 0.16 & 0.992 \(\pm\) 0.002 & 0.984 \(\pm\) 0.011 & 92.9 \(\pm\) 0.4 & 0.374 \(\pm\) 0.005 & 1.007 \(\pm\) 0.084 & 81.0 \(\pm\)0.1 \\  & abc & a & abc & b & c & ab & b \\ Soaked 10\({}^{*}\) & 12.87 \(\pm\) 0.07 & 0.991 \(\pm\) 0.001 & 0.954 \(\pm\) 0.004 & 93.3 \(\pm\) 0.4 & 0.379 \(\pm\) 0.003 & 0.971 \(\pm\) 0.082 & 81.6 \(\pm\) 0.2 \\  & abc & a & ab & a & bc & a & b \\ Soaked 20\({}^{*}\) & 12.43 \(\pm\) 0.015 & 0.991 \(\pm\) 0.001 & 0.978 \(\pm\) 0.003 & 93.6 \(\pm\) 0.4 & 0.333 \(\pm\) 0.001 & 1.204 \(\pm\) 0.128 & 84.0 \(\pm\) 0.1 \\  & a & a & abc & a & abc & bc & cd \\ Soaked 30\({}^{*}\) & 13.06 \(\pm\) 0.01 & 0.991 \(\pm\) 0.001 & 0.919 \(\pm\) 0.006 & 93.7 \(\pm\) 0.1 & 0.361 \(\pm\) 0.012 & 1.134 \(\pm\) 0.014 & 83.7 \(\pm\) 0.2 \\  & bc & a & a & a & abc & bc & cd \\ US 21 kHz 10\({}^{*}\) & 13.95 \(\pm\) 0.42 & 0.993 \(\pm\) 0.001 & 0.977 \(\pm\) 0.009 & 93.5 \(\pm\) 0.6 & 0.377 \(\pm\) 0.005 & 1.062 \(\pm\) 0.101 & 81.7 \(\pm\) 0.3 \\  & d & a & bc & b & c & b \\ US 21 kHz 20\({}^{*}\) & 13.26 \(\pm\) 0.53 & 0.994 \(\pm\) 0.001 & 0.986 \(\pm\) 0.013 & 94.6 \(\pm\) 0.6 & 0.328 \(\pm\) 0.0017 & 1.017 \(\pm\) 0.195 & 82.9 \(\pm\) 0.1 \\  & c & a & bc & b & abc & bc & c \\ US 21 kHz 30\({}^{*}\) & 14.06 \(\pm\) 0.06 & 0.993 \(\pm\) 0.001 & 0.989 \(\pm\) 0.013 & 93.7 \(\pm\) 0.3 & 0.349 \(\pm\) 0.014 & 0.995 \(\pm\) 0.225 & 75.3 \(\pm\) 1.5 \\  & d & a & bc & b & abc & bc & a \\ US 35 kHz 10\({}^{*}\) & 12.50 \(\pm\) 0.28 & 0.993 \(\pm\) 0.001 & 0.949 \(\pm\) 0.009 & 94.1 \(\pm\) 0.3 & 0.319 \(\pm\) 0.012 & 1.030 \(\pm\) 0.108 & 83.2 \(\pm\) 0.1 \\  & ab & a & abc & a & ab & bc & c \\ US 35 kHz 20\({}^{*}\) & 12.56 \(\pm\) 0.15 & 0.991 \(\pm\) 0.001 & 0.970 \(\pm\) 0.014 & 93.8 \(\pm\) 0.9 & 0.319 \(\pm\) 0.020 & 1.032 \(\pm\) 0.147 & 84.5 \(\pm\) 0.1 \\  & ab & a & abc & a & bc & bc & de \\ US 35 kHz 30\({}^{*}\) & 12.25 \(\pm\) 0.42 & 0.992 \(\pm\) 0.001 & 0.981 \(\pm\) 0.011 & 95.5 \(\pm\) 0.4 & 0.294 \(\pm\) 0.005 & 1.057 \(\pm\) 0.095 & 85.3 \(\pm\) 0.1 \\  & a & a & c & a & a & bc & e \\ \hline \hline \end{tabular}  
* \({}^{*}\)a–e–homogeneous groups are presented next to mean values (mean \(\pm\) standard deviation) as different letters within the same column, which indicate statistical significance (\(p<0.05\)).  
\end{table} 
Table 1: Basic physical properties after pretreatments (blanching, soaking, ultrasound) and after infrared–hot air drying. a frequency of 21 kHz. In this case, material exposed to ultrasound at a frequency of 21 kHz for 30 min exhibited the lowest shrinkage at 75.3 \(\pm\) 1.5%. Additionally, there was no significant effect of ultrasound time and frequency on material shrinkage.