## 3 Results and Discussion
### Evaluation of Apple Weight Loss and Quality during Storage
As the light intensity and ambient temperature increase, the amount of carotenoids that determine the yellow color increases in the fruit, while, in lower temperatures and in the acidic medium, apples produce more anthocyanins that produce the red color of the fruit [71]. During storage, apples tend to change color because organic cells release organic acids from the vacuoles in the fruit cells, which interact with enzymes that hydrolyze pigments [24; 73]. [PERSON] and [PERSON] found that, during apple storage, apple browning was influenced by temperature, pH value, changes in the qualitative and quantitative composition of phenolic compounds, and a decrease in the mechanical resistance of apple skin [4; 50]. Our study showed that the color lightness of the apple samples of 'Alva', 'Lodel', and 'Noris' cultivars kept under low oxygen (1%) and high carbon dioxide (3%) conditions was close to that of fresh fruit. Our study showed that the storage conditions determined the color of the apples, as well as its saturation and intensity, and allowed for maximizing apple storage duration with minimal changes in color and commercial appearance. Determining the firmness index of fruit is important in assessing the mechanical resistance of apples during both storage and transportation [34]. We investigated the firmness of apple peel and flesh during their storage. We found that the firmness of 'Sampion' apple peel samples stored in chambers I and III-VI increased compared to that recorded before storage. There was also an increase in the firmness of the flesh of apple samples of 'Auksis', 'Noris', 'Cornel Red', and 'Lodel' cultivars stored in chamber III and VI conditions. [PERSON] et al. found that the firmness of 'Antonovka Kamenitschka' and 'Antonovka Pamtorutka' apple samples during storage increased from 95.1 to 107.9 N cm\({}^{-2}\) and from 92.2 to 101.0 N cm\({}^{-2}\), respectively [56]. Storage conditions affecting the firmness of apple peel and flesh may in part reduce changes in physical properties and prolong the shelf life of apples. The characteristics of apple cultivars determine not only the organoleptic and physical properties or the chemical composition, but also the mass of the fruit [62]. In our study, we evaluated changes in apple fruit mass during storage. The study showed that apple samples of 'Spartan', 'Ligol', and 'Cortlend' cultivars stored in chamber II (5% of O\({}_{2}\), 1% of CO\({}_{2}\), and 94% of N\({}_{2}\)), III (5% of O\({}_{2}\), 3% of CO\({}_{2}\), and 92% of N\({}_{2}\)), and V (5% of O\({}_{2}\), 7% of CO\({}_{2}\), and 88% of N\({}_{2}\)) conditions were found to have the lowest quality losses of 3.90, 3.00, and 3.50%, respectively. [PERSON] and [PERSON] found that increasing the storage of apples to 4 months or 5 months increased the percent weight loss of apples by 4.05 or 4.53%, respectively [40]. In our studies, apples were stored for a longer period of 8 months, and, thus, twice the loss of apple weight was found. The results also showed that the mass of the apples determined their quality during storage. During the study, we found that the organoleptic and physical properties, as well as the chemical composition of apples, varied between samples of different cultivars and depended on the composition of the atmosphere used during the storage. By choosing the optimal conditions of a controlled atmosphere, it is possible to minimize changes in the chemical composition and physical and organoleptic properties of the apples, which determine their quality and commercial value.