## 3 Results and Discussion  
### Moisture and Water Activity  
Moisture content in the fresh apple samples was in the range of 83.97 \(\pm\) 0.08% ('Starkrimson' cultivar) to 86.27 \(\pm\) 0.31% ('Florina' cultivar). In the case of fresh samples from the 'Golden Delicious' cultivar, the moisture content was determined as 86.03 \(\pm\) 0.06%. These values are close to those reported in other papers. For example, [PERSON] et al. [53] obtained the following values for apple moisture content: 83.04 \(\pm\) 0.87% 'Starkrimson' cultivar, 86.12 \(\pm\) 1.35% 'Florina' cultivar and 84.61 \(\pm\) 0.58% 'Golden Delicious' cultivar. After drying in the oven, the following moisture values were obtained for the apple samples: 6.63 \(\pm\) 0.01% ('Florina' cultivar), 6.83 \(\pm\) 0.03% ('Golden Delicious' cultivar) and 7.08 \(\pm\) 0.04% ('Starkrimson' cultivar). The moisture content of apple chip samples dried inthe dehydroxtor ranges between 5.06 \(\pm\) 0.03% ('Florina' cultivar) and 6.29 \(\pm\) 0.03% ('Golden Delicious' cultivar). For samples of the 'Starkrimson' apple cultivar dried in a dehydroxtor, an average moisture of 5.55 \(\pm\) 0.05% was obtained. These values are close to those reported by [PERSON] et al. [33] who obtained, by conventional drying, apple chips with moisture values between 5.17 \(\pm\) 0.23 and 6.04 \(\pm\) 0.31%, from fresh 'Idared' apples with 88.7 \(\pm\) 3.9% water content. Water activity shows how closely the water in an apple slice is bound. If _aw_ values are less than 0.8, it means that the food has low water activity, and the most enzymatic reactions are slowing down. It is considered that the target value of dried products is _aw_ = 0.6, which is the general level limit for the growth of molds, yeasts and bacteria [13; 54; 55; 56]. In Figure 2 are illustrated the _aw_ values obtained for fresh and dried apple chip samples. The _aw_ of dried apple chip samples was investigated also at 7, 14 and 21 days during storage at room temperature. The highest value of _aw_ (0.910) for the fresh apple sample was obtained for samples from the 'Golden Delicious' cultivar, followed by samples from the 'Starkrimson' cultivar with a mean value of 0.906. The _aw_ mean value obtained for samples from the 'Florina' cultivar is slightly lower than those obtained for the samples of the other two cultivars. The water activity values for the oven-dried apples range from 0.544 to 0.650 with the highest value obtained for samples from the 'Starkrimson' cultivar and the lowest for the samples from the 'Florina' cultivar. In the case of apple chips dried in the dehydroxtor, it was observed that the highest mean value (0.426) was obtained for samples from the 'Golden Delicious' cultivar, while the lowest value (0.374) was determined for samples from the 'Starkrimson' cultivar. According to the results obtained, the water activity is below 0.6 for almost all samples of dried apple chips, with one exception. The obtained values are close to those reported by [PERSON] et al. [55] for osmo-convectively-dried 'Idared' apple samples (_aw_ = 0.542) and [PERSON] et al. [17] (2021) who dried 'Gala' apples using hot air drying (_aw_ = 0.345) and non-thermal ultrasound contact drying (_aw_ = 0.386). It can also be observed that the samples dried in the dehydroxtor have lower water activity values than those dried in the oven. Over time, up to 21 days, the _aw_ values of dried apples vary, and it was observed that _aw_ increases by about 41% and 10% in the case of 'Starkrimson' cultivar samples dried in a dehydroxtor and oven, respectively. The  
Figure 2: Water activity (_aw_) evaluation of fresh and dried apple chips during storage under ambient conditions (S1—apple chips ‘Starkrimson’, oven; S2—apple chips ‘Starkrimson’, dehydroxtor; G1—apple chips ‘Golden Delicious’, oven; G2—apple chips ‘Golden Delicious’, dehydroxtor; F1—apple chips ‘Florina’, oven; F2—apple chips ‘Florina’, dehydroxtor). Notes: 0—-fresh apple samples, 0—dried apple samples.