# The Effect of Hybrid Drying Methods on the Quality of Dried Carrot
## 3 Results  
The relationship between the drying method and the water activity (\(\mathrm{a_{w}}\)) parameter was assessed. As a result of the research, the average content of water activity of dried carrots was shown in Figure 2. The lowest value of the examined parameter was characteristic of freeze-dried carrot (F), the water activity of which was 0.176. In turn, the dried material obtained as a result of microwave (M) and convection (K) drying was characterized by the highest water activity, respectively, \(\mathrm{a_{w}}\) = 0.390 and \(\mathrm{a_{w}}\) = 0.300, and the differences are statistically significant (Table 2). The combination of freeze-drying with convection-drying (F-K (freeze-drying-convection), K-F (convection-freeze-drying)) and microwave-drying (F-M (freeze-drying-microwave), M-F (microwave-freeze-drying)) results in obtaining water activity with a much higher value and statistically significant difference than in the case of freeze-drying (F). An intermediate \(\mathrm{a_{w}}\) value was obtained for samples from drying, where the first freeze-drying method (F-K, F-M) was used, the duration of which was much shorter than that of the freeze-drying process. The influence of the drying method on the dry matter content of dried carrots was also investigated (Figure 3) (Table 3). It was shown that all drying methods allowed us to obtain dried material with a dry substance content exceeding 94%. The highest value was observed for freeze-dried carrots (F)-98.36%. The dried material obtained by convection-drying (K) \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Count** & **Average** & **Standard Deviation** & **Coeff. of Variation** \\ \hline K-F & 3 & 0.329333 & 0.00321455 & 0.976078\% \\ K & 3 & 0.299667 & 0.0023094 & 0.770657\% \\ F-M & 3 & 0.262 & 0.0043589 & 1.6637\% \\ F & 3 & 0.175667 & 0.0109351 & 10.8359\% \\ F-K & 3 & 0.335 & 0.0069282 & 2.06812\% \\ M-F & 3 & 0.312 & 0.0155242 & 4.9757\% \\ M & 3 & 0.39 & 0.00866025 & 2.22058\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The results of the analysis of the variance of water activity for dried carrots depend on the drying method. Statistical significant differences at \(p<0.05\). Designations in Table 1.  
Figure 2: The impact of the type of drying method on the water activity of dried carrots. The same letters (a–e) in individual columns indicate the absence of a statistically significant difference between the samples (significance level 0.05). Designations in Table 1.  
was characterized by a dry matter content of 94.95%. The combination of freeze-drying with convection-drying allowed us to obtain dried samples with the following dry substance content: 95.68% (F-K), 94.11% (K-F), while in microwave-drying 96.47% (F-M), 94.47% (M-F), respectively. All these values of the dry matter content are lower than in the case of freeze-drying at 98.36% (F). On the other hand, combined drying methods using freeze-drying as the first technique (F-K; F-M) did not differ significantly in terms of dry matter content. The freeze-dried sample with microwave-drying (F-M) was characterized by a similar level of dry matter content to the control sample, which was freeze-dried (F). Carrot samples in which freeze-drying was used as a drying step (M-F, K-F) did not differ in the dry matter content. Figure 4 shows the results of the apparent density of dried carrots for various drying methods. It was shown that the type of drying method used had a statistically significant effect on the apparent density of the material (Figure 4) (Table 4). The freeze-dried (F) carrot sample obtained the lowest density. The samples subjected to convection (K) and microwave (M) drying were characterized by the highest density. All samples using methods combined with freeze-drying (F-K, F-M, K-F, M-F) had a higher density value compared to the control sample (F), but lower than for convective dried (K) and microwave-dried (M).