## 3 Results and Discussion
### Peroxide Value  
The peroxide value is a widely utilized quality parameter for the monitoring of lipid oxidation and the determination of oil quality. It provides quantitative results regarding the level of primary oxidation products present in oils and fats. In vegetable oils, the peroxide value reflects the extent of oxidation and, consequently, the degree of rancidity [57]. Table 2 illustrates the change in peroxide value observed in both the coated (E+) and uncoated samples (E-). The values exhibited a range of 0.67 to 4.99 milliequivalents of oxygen per kilogram (meqO\({}_{2}\)/kg). Regardless of the coating application, air composition, and packaging material, both increasing and decreasing trends in peroxide values were observed. The use of nitrogen gas resulted in a reduction in peroxide values for all samples, regardless of the packaging material (0.69-3.49 meqO\({}_{2}\)/kg) compared to the samples stored in an atmospheric environment (0.73-4.99 meqO\({}_{2}\)/kg). The lowest peroxide values were observed for the combined application of metalized polypropylene and nitrogen gas (MPP-N-E-). The application of nitrogen treatment was demonstrated to be the most effective method for preserving the quality of walnuts, resulting in minimal degradation across a range of storage conditions and packaging materials, particularly those composed of polyethylene (PE) and polypropylene (PP). While extract coating provides some initial protection, its effectiveness diminishes over time, particularly in PLA, where significant quality loss occurs. The most rapid deterioration in quality is observed in cases where atmospheric treatment is employed, particularly in the case of PM (metallized polypropylene), which exhibits high initial values indicating a faster rate of degradation. Over time, the differences between packaging materials become less pronounced, with polyethylene (PE) and polypropylene (PP) offering comparable levels of protection by time point 8. In conclusion, nitrogen treatment is the most reliable method for maintaining walnut quality,  
Figure 5: Fatty acid content of the PE and PLA packaging samples during storage (%). PE (polyethylene), PLA (polylactic acid), A–E- (air without edible coating), A–E+ (air, with edible coating), N–E- (nitrogen without edible coating). while extract coating and packaging material selection play a secondary role in long-term preservation. [PERSON] and [PERSON] [44] stored walnuts refrigerated and at room temperature for six months in a normal air composition and packed in nitrogen gas. The initial value was 0.24-0.28 meQ\({}_{2}\)/kg, and the maximum during storage was 1.15 meqO\({}_{2}\)/kg. Most of the walnut samples showed similar changes in peroxide values: they increased first, then decreased to a minimum in the third month of storage, and they increased again. According to [PERSON] and [PERSON] [44], it can be concluded from the results that the rate of degradation was faster than the formation of peroxides in the third month of storage. A similar fluctuating trend was observed by several researchers during the storage of walnuts. This may be due to the unstable nature of peroxides and their simultaneous formation and degradation in vegetable oils. According to [PERSON] et al. [58], the unstable lipoxygenase activity may also be the cause of the fluctuating tendency of peroxide values. [PERSON] et al. [51] investigated the peroxide value during the storage of walnut oil samples at 60 \({}^{\circ}\)C for 60 days. Their results were between 1.19-3.75 meqO\({}_{2}\)/kg. During the storage, similar changes were observed in the tendency of the peroxide value to the results of our study, i.e., increasing and decreasing phases followed each other. According to the standards of most companies, the peroxide value should be lower than 1 meqO\({}_{2}\)/kg; however, in the study of [PERSON] et al. [59] walnuts with a peroxide value of less than 3 meqO\({}_{2}\)/kg are also of acceptable quality. In addition, [PERSON] et al.