## 4 Discussion
### Characteristics of Fresh and Packed Nettle Leaves
#### 4.4.3 Photosynthetic Pigments  
Photosynthetic pigments play a crucial role in the development of plants, but they are also considered important nutrients in the human diet with therapeutic properties [74]. In packaged products, the chlorophyll content might vary depending on the specific combination of gases, temperature, and other factors within the packaging. By limiting O\({}_{2}\) levels, enzymatic processes are inhibited, including those that lead to chlorophyll degradation, while also oxidative processes can be slowed down, thereby maintaining chlorophyll and carotenoid content [75]. Since the degradation of photosynthetic pigments can be the result of oxidative processes in plant cells, CO\({}_{2}\) can help to mitigate oxidation by scavenging reactive oxygen species (ROS), while increased CO\({}_{2}\) levels reduce the degradation of pigments. More importantly, high atmospheric CO\({}_{2}\) levels generally increase the photosynthetic rate of plants [76] and thus ensure the preservation of photosynthetic pigments. However, it should be emphasized that an extremely low level of O\({}_{2}\) or a high level of CO\({}_{2}\) can lead to side effects and increase the degradation of photosynthetic pigments. The effect of O\({}_{2}\) and CO\({}_{2}\) content inside the packages of the different types of packaging materials used in this study (Figure 5a,b) clearly indicates that the packaging material of lower gas permeability (PA/PE) with extremely high CO\({}_{2}\) content and low O\({}_{2}\) content favored the degradation of photosynthetic pigments, so that this type of packaging generally had the lowest content of all photosynthetic pigments analyzed, which is consistent with other literature data [2; 77]. On the other hand, the highest content of photosynthetic pigments was found in nettle leaves packed in BOPP material during both 6 and 14 days of storage (Figure 5a). When monitoring the gas composition during the storage period, the lowest O\({}_{2}\) content and higher CO\({}_{2}\) content than in LDPE and PLA were found in the mentioned package, which was obviously a suitable level for the preservation of the content of photosynthetic pigments, and at the same time, it explains the crucial role of the proportion of atmospheric gases during the storage period in certain packaging materials. [PERSON] et al. [77] concluded that the low level of O\({}_{2}\) in packaged Chinese cabbage played a major role in maintaining the chlorophyll and carotenoid content, which correlates with our data.  
While observing days of storage as individual factors (Figure 5b), photosynthetic pigments were best preserved after 6 days of storage, whereby 89% of TChl and 84% of TCA remained preserved compared to fresh nettle leaves. During the subsequent storage period, i.e., over a total period of 14 days, the degradation of the photosynthetic pigments continued, with the content of TCh decreasing by approx. 28% and TCA by approx. 11% compared to the samples stored for 6 days, regardless of the packaging material (Figure 5b). Chlorophyll degradation is a natural process influenced by various internal and external factors that occur in plant green organs, particularly during senescence [78], and the degradation of photosynthetic pigments during time was also recorded for other leafy vegetables [57; 79]. It was therefore expected that the pigment content in leaves packed in different packaging materials would be degraded over time as a result of the plants' natural senescence process.