## 3 Results and Discussion
### Changes in Organoleptic Characteristics of Apple before and after Storage in CA
#### 3.2.2 Changes in Apple Peel and Flesh Firmness  
Consumers seek to obtain fruit with good appearance and optimal texture and firmness [39]. Overripe and mechanically damaged fruits soften, and, thus, the fruit firmness index is important as a fruit quality criterion that allows the selection of good quality fruit suitable for consumption [34]. Determining the firmness index of the fruit is important in  
Figure 2: Changes in coordinates measured in NBS units in apple peel before and after storage in CA: (**a**) color saturation (C*) co-ordinate; (**b**) lightness (L*) co-ordinate. assessing the mechanical firmness of apples during both storage and transportation [34]. The values of firmness indices of the peel and flesh of apples of different cultivars were determined at the beginning of the experiment and after 8 months of storage in a controlled atmosphere of various compositions. The evaluation showed that the firmness of apple peel before storage varied from 165.7 \(\pm\) 41.3 N cm\({}^{-2}\) to 310.3 \(\pm\) 39.8 N cm\({}^{-2}\) in different cultivars (Table 5). Apple peel of 'Connel Red' and 'Ligol' cultivars was found to be the firmrest, at 310.3 \(\pm\) 39.8 N cm\({}^{-2}\) and 307.9 \(\pm\) 38.4 N cm\({}^{-2}\), respectively (Table 5). The evaluation also showed that, before storage, apple samples of the 'Connel Red' cultivar had the firmrest flesh (82.9 \(\pm\) 15.9 N cm\({}^{-2}\)) (Table 5). [PERSON] et al. pointed out that the firmness of 'Granny Smith' apples varied from 80 N cm\({}^{-2}\) to 98 N cm\({}^{-2}\), while, in apples of the 'Golden Delicious' cultivar, it was up to 53 N cm\({}^{-2}\)[39]. The peel of 'Spartan' apples kept under chamber VIII conditions was found to have softened by 38.25% (Table 5). Meanwhile, the flesh of 'Spartan' apples stored in chamber I conditions softened by as much as 47.40% (Table 5). Apple peel samples of the 'Sampion' cultivar stored in chamber I and III-VI conditions were found to have increased firmness compared to that before the storage (Table 5). The results of our study were confirmed by [PERSON] et al., who found that apple samples may soften by 32.00 to 47.00% during storage, but also presented data showing that the firmness of the apple samples of 'Antonovka Kamenitschka' and 'Antonovka Pamtorutka' cultivars increased, respectively, from 95.1 to 107.9 N cm\({}^{-2}\) and from 92.2 to 101.0 N cm\({}^{-2}\) during storage [56]. [PERSON] and [PERSON] pointed out that the firmness of apples during storage depended on the characteristics of the apple cultivar [40]. As fruit shelf-life increases, apples soften due to changes in the pectin content of the cells [57], decreased water content, and intensified respiration [47]. Mechanical damage to carrot roots has been found to increase ethylene production, which intensifies sugar use during the respiration process [58]. During this process, the fruit becomes less sweet and a bitter taste appears. The bitter taste changes the organoleptic properties of the apples and reduces their commercial value. In scientific literature, we did not find any research results on the strength of the correlation between changes in the chemical composition of apples and the firmness indices in samples of apples grown in Lithuania, stored in a controlled atmosphere of different compositions. We calculated Pearson's correlation coefficients between changes in the content of soluble solids and the firmness values in apples during storage. The content of soluble solids in apple samples weakly (r = 0.072 and r = 0.291) and moderately strongly (from r = 0.300 to r = 0.365) positively correlated with the firmness values of apples before storage (Figure 3). We analyzed the strength of the correlation between the content of soluble solids and the changes in the firmness values in apples stored under chambers I to VIII conditions.