## 4 Discussion
### Characteristics of Fresh and Packed Nettle Leaves  
#### 4.4.1 Water Content of Nettle Leaves  
In the chemical analysis of plant material, the first general quality indicator is the total dry matter content, as it comprises the composition of all chemical components of a raw material except water [61]. However, a particular challenge during storage, especially of green leafy vegetables, is the transpiration of the plant material, where there is a significant loss of water in the plant material, which ultimately affects the quality of the food, especially its sensory and textural properties, such as wilting, discoloration, loss of freshness, and the appearance. This is because leafy vegetables have a high surface-to-volume ratio and therefore a proportionally higher transpiration rate, i.e., water loss during storage, is greater in this raw material [62]. By selecting suitable packaging materials that are adapted to the properties of water vapor permeability and gases, the prolongation of the quality of such leafy vegetables can be significantly influenced [63; 64].  
While observing separate individual factors (Figure 4b), it can be seen that water content (W) remained equally well maintained in all packaging, with the exception of PLA, regardless of days of storage. The lowest W value in nettle leaves packaged in PLA material was to be expected, as this material has been shown to be the most permeable to water vapor (Table 2), which affects the W content of nettle leaves. Regardless of packaging material and considering days of storage, recorded data show higher W values during the first 6 days compared to the 14 days, which is also justified because plants lose moisture over time. However, it should be noted that despite the statistically justified difference, W loss did not decrease as much in the following days of storage (14 days in total), justifying the need to pack the leaves in order to minimize water loss and thus other important external characteristics of the product, which are particularly important from the consumer's point of view. Although various factors significantly influenced the W in nettle leaves, the W in leaves from this study was consistent with the values of other leafy vegetables obtained by other authors, again proving the validity of the packaging [65; 66; 67].  
Additionally, there are several studies on fresh nettle plant material, but information on packaged and stored nettle leaves has not been found. In a study by [PERSON] et al. [68], the water content of fresh nettle averaged 71.66%, which was lower than in packed leaves from this present study. [PERSON] et al. [69] reported 89-75.1%, while [PERSON] et al. reported [70] 80.3-73.7% of water content in fresh nettle leaves, which is in accordance with the results of the present study.  
The W content of packaged leaves can significantly be influenced by the choice of packaging materials with varying permeability properties, but it also depends on storage conditions, especially air humidity. Materials with high permeability generally tend to evaporate water more intensively, leading to moisture exchange between the plant material and the environment [63; 64], which was also confirmed by our results. If the outer environment is less humid than the inner packaging space, the plant material will lose water, as was the case with the nettle leaves packaged in PLA materials in this study. The high W content in nettle leaves packaged in BOPP, LDPE, and PA/PE indicates that the freshness and quality of the leaves packaged in these materials were well preserved. This is also consistent with the measurements of the _WVP_ of the materials (Table 2), which show that the selection of the appropriate polymer packaging material is important for the preservation of the water content of fresh plant material.