## 4 Discussion
### Macronutrients
Calcium and magnesium are generally bound to the plant tissue and are not readily lost by leaching and sometimes can even be taken up by vegetables during blanching from the processing water in areas with hard water [36]. Similar observations were made by other authors [4; 36; 39] on traditionally cooked and steamed cauliflower, broccoli and Brussels sprouts. [PERSON] and [PERSON] [37], after 12-15 min of cooking, observed a decrease in the content of this micronutrient in kale by 38%, which is almost congruent with our results. Minerals compared with vitamins are more resistant to food processing. However, these components cannot tolerate alterations after exposure to light, moisture, heat or oxygen during the processing and storage of food materials. Moreover, processing can also improve accessibility of micronutrients by decreasing antinutrient levels [40]. The highest content of sodium in fresh material was noted in purple cauliflower (847.29 mg/kg dm) and lowest in kale (364.56 mg/kg dm). The results reported by the [PERSON] and [PERSON] [4] for _Romanesco_ green cauliflower were slightly higher, in comparison to those obtained in this study (760.90 mg/kg dm), while for white floret cauliflower they were much higher. This highlights even more the diversity in the content of mineral components depending on many factors, such as variety, agrotechnical factors and climate conditions. The iron contents in various _Brassica_ species, reported by other authors, were much higher [35; 36; 37; 39]. In cauliflowers grown in Bangladesh, the sodium content was significantly differentiated: 165.73 mg/100 g dm for naturally grown and 429.11 mg/100 g dm watered with waste water [9]. Blanching and cooking resulted in significant losses of this micromineral, which agrees with the findings of other authors [4; 36; 39]. The largest losses of this component under the influence of the cooking process were observed in green cauliflower (46.6%) which is rich in this ingredient, and the smallest in the kale (21.8%). _Brassica_ plants have been found to be rich in many minerals including calcium. All analyzed vegetables contained over 3300.00 mg/kg of calcium. Among analyzed _Brassica_ the highest content was observed for kale (15,968.98 mg/kg dm) and the lowest for rutabaga (3394.43 mg/kg dm) (Table 1). Interestingly, kale and cauliflower exhibit excellent calcium bioavailability. Comparing the determined calcium content of the analyzed fresh _Brassica_ vegetables with literature data, it could be concluded that they were quite similar or higher [4; 36; 37; 38; 39; 40; 41]. Results of calcium content analyses in cauliflowers originating from Bangladesh were significantly higher (730.38 mg/100 g dm) [35]. The content of calcium in rutabaga, given by [PERSON] et al. [41], was much higher compared to our results. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & **Potassium** & **Sodium** & **Calcium** & **Magnesium** & **Copper** & **Manganese** & **Iron** & **Zinc** \\ \hline \multirow{2}{*}{kale} & blanched & 24.0 & 7.6 & 6.3 & 1.3 & 4.7 & 13.5 & 12.8 & 5.5 \\  & cooked & 40.4 & 21.8 & 20.2 & 6.8 & 12.9 & 27.6 & 48.4 & 49.8 \\ \hline \multirow{2}{*}{rutabaga} & blanched & 5.9 & 5,3 & 7.5 & 5.4 & 16.3 & 5.5 & 2.2 & 0.6 \\  & cooked & 29.6 & 39.4 & 30.2 & 15.3 & 36.4 & 14.2 & 16.8 & 10.1 \\ \hline \multirow{2}{*}{green cauliflower} & blanched & 5.6 & 3.6 & 2.8 & 3.9 & 16.1 & 4.5 & 18.4 & 6.6 \\  & cooked & 45.9 & 46.6 & 18.0 & 28.2 & 36.6 & 16.4 & 49.4 & 25.8 \\ \hline \multirow{2}{*}{purple cauliflower} & blanched & 5.0 & 17.4 & 10.3 & 5.3 & 8.5 & 4.3 & 3.5 & 3.8 \\  & cooked & 41.6 & 26.3 & 19.0 & 40.9 & 27.1 & 44.6 & 22.0 & 20.4 \\ \hline \hline \end{tabular}  
* Percentage losses of compounds determined by the effects of hydrothermal processing were calculated in compliance with mass balance changes. This way of presenting data eliminated the influence of thinning the content of the element (with water), and demonstrated only the influence of the processing technique applied.  
\end{table}