# Investigation of Salt and Water Diffusion During Dry Salting, Wet Curing, and Ultrasonic Wet Curing
## 3 Results and Discussion
### Diffusion Constants
#### 3.4.2 Diffusion Constant for Water  
The values of the diffusion coefficients estimated by the diffusion models for water content are given in Table 4. In this case, the model of [PERSON] et al. (2004) [14] had the smallest error (the smallest RMSE in the case of dry salting and wet curing + ultrasound and the middle RMSE in the case of simple wet curing). According to this model, the diffusion coefficient of a cylindrical long loin meat sample treated with dry salting at 20 \({}^{\circ}\)C, with a length of 80 mm and a diameter of \(\mathcal{O}\)15 mm, was 2.42 \(\times\) 10\({}^{-9}\) m\({}^{2}\)/s.  
According to all three mathematical models, the diffusion constant of water decreases by an order of magnitude (75-80%) in the case of wet processes. Due to this, the use of wet curing results in a more favorable yield than traditional dry curing. It is interesting to  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Diffusion Constant—D \(\times\) 10\({}^{-9}\) [m\({}^{2}\)/s]**} & \multicolumn{3}{c}{**RMSE**} \\ \hline  & **M** & **A** & **T** & **M** & **A** & **T** \\ \hline
**DS** & 2.18 & 2.42 & 1.63 & 0.1375 & 0.1426 & 0.1283 \\ \hline
**WP** & 0.48 & 0.50 & 0.40 & 0.1023 & 0.1199 & 0.1091 \\ \hline
**US** & 0.73 & 0.79 & 0.59 & 0.0923 & 0.0962 & 0.0906 \\ \hline \hline \end{tabular}  
* DS: dry salting, WP: wet curing, US: wet curing + ultrasound. Fitted models: M: [PERSON], A: [PERSON], T: [PERSON].  
\end{table}
Table 4: Estimation of the diffusion constant of water based on the fitted literature models.  
Figure 5: Effect of wet and ultrasonically assisted wet curing processes on improving the salt diffusion coefficient compared to dry salting (x-axis: Variation in diffusion coefficient in percent of dry salting). WP: wet curing, US: wet curing + ultrasound. Fitted models: [PERSON], [PERSON], [PERSON].  
observe that the addition of ultrasound to wet curing does not improve the favorable effect on the yield, since in this case, the diffusion coefficient only shows a decrease of about 65%.  
Furthermore, it can be said that all three models proved to be much more inaccurate than with the salt content. The reasons for this may be the following:  
1. The movement of water is not characterized by pure diffusion as salt is, but as described above, it is a two-way process, the result of which provides the driving force for the movement of water.
2. The binding of water does not only occur based on the principle of diffusion but surface binding must also be taken into account. We were prepared for this phenomenon during the measurement, which is why the removal of moisture from the surface of the cured samples was an important step. However, the removal of surface moisture cannot be carried out perfectly. On the one hand, this is because water molecules can bind more strongly to molecular chains with polar groups on the surface of the meat than to the material of the blotting paper. On the other hand, the surface of the meat cut in the direction of the grain contains a ribbed surface and grooves, due to which, some of the surface water does not even come into contact with the blotting paper during the soaking.  
Despite the inaccuracy of the individual models, similarly to the diffusion of salt, the weakening effect of wet curing processes on water diffusion compared to dry salting can be clearly seen (Figure 6).