## 4 Discussion  
### Physicochemical and Barrier Properties of Used Packaging Materials  
Table 2 shows the results of analyzing the packaging material's properties (thickness, transparency, transmittance, permeability to water vapor, and water vapor transfer rate). According to \(T_{600}\) the most transparent material was LDPE, followed by BOPP, while the least transparent was PA/PE. Results are similar to what was previously given in LDPE (with \(T_{600}\) of 3.05 and transmittance of 86.9%), OPP (\(T_{600}\) of 1.67 and transmittance of 89.1%), and PLA (with a transmittance of 90%) [36; 37]. According to [PERSON] et al. [17], the  
Figure 8: Antioxidant capacity of nettle leaves packed in different packaging materials and stored for 14 days, (a) results with regard to the combination of factors, (b) results with regard to individual factors. Values are represented as means of three replicates \(\pm\) standard deviation. Different superscript letters (a–h) indicate statistically significant differences between samples at \(p\leq\) 0.05.  
acceptable limit of transparent packaging polymer materials is approximately 80%, and materials with transmittances above 90% are considered highly transparent. Therefore, only PA/PE used in this study can be considered as not well transparent. Good transparency is indeed a property of BOPP, LDPE, and PLA that are widely used in the packaging industry, contributing to the visibility of the packed content as an important factor [38; 39]. The determination of transparency and transmittance is important, as they enable a visual inspection of the contents and an assessment of the freshness and appearance of the food. In addition, materials with extremely high transparency and transmittance that allow too much light to penetrate can accelerate the degradation of bioactive compounds due to light exposure; therefore, storage in dark conditions is recommended. Measurements of the permeability of films to water vapor (_WVP_) and the rate of water vapor transfer through the films (_WVTR_) shown in Table 2 indicate that PLA material used in this study was less permeable to water than previously reported (approximately \(1.8\cdot 10^{-11}\)[40] and \(2.3\cdot 10^{-11}\) g m/s m\({}^{2}\) Pa [41]. In general, the water vapor barrier performance of biodegradable polymers is much lower than that of some synthetics, such as LDPE, which is therefore suitable for the short-term protection of plant materials against water [42]. Water vapor permeability and transmission of packaging films are important parameters as they determine the rate of moisture exchange between the packaged food product and the surrounding environment. Too high-water permeability can lead to moisture and weight loss, and texture degradation of packed fresh fruits and vegetables. On the other hand, low-water permeability of the packaging material can lead to condensation of moisture on the inner surface of the film, which favors microbial growth, but it also helps maintain optimal moisture levels, preventing dehydration and wilting [42; 43; 44]. The water vapor permeability of polymer packaging materials is therefore important for maintaining the quality, freshness, and shelf life of packed vegetables. By carefully selecting materials with the appropriate permeability, it is possible to control moisture levels, reduce spoilage, and ensure the vegetables reach consumers in optimal condition. Low _WVP_ is considered desirable for packaging leafy vegetables [46], therefore, it is important to test permeability to water vapor and choose proper packaging films for specific plant materials. The results of the permeability coefficient (\(P\)) of tested materials to O\({}_{2}\) (\(PO_{2}\)) and CO\({}_{2}\) (\(PCO_{2}\)) shown in Figure 1 indicate large differences between tested materials. These differences in the gas permeability would influence the exchange of gases through the films used in MAP packaging and, therefore, the quality of oxidation-sensitive and respiring food products, as is the case with the nettle used in this study.