## 3 Results and Discussion
### Thermal Properties of Fruit Fibres and Pomace  
The thermogravimetric analysis (TGA) curves and their first derivatives (DTG) for the fibres are shown in Figure 6 and were studied to assess the thermal stability (Table 8). The dTG curves were shifted vertically for easier comparison. All the fibres analysed showed similar behaviour in the three main stages of weight loss (Figure 6). The first stage was observed up to 66 \({}^{\circ}\)C and was associated with the loss of adsorber and bound water. Typically, the first stage, from 25 to 200 \({}^{\circ}\)C, is assigned to the evaporation of water and molecular-weight molecules. The type of fibre influenced this stage. Apple fibre showed the highest temperature (66.88 \({}^{\circ}\)C), while currant fibre showed the lowest temperature (64.31 \({}^{\circ}\)C), associated with a lower thermal stability. Apple fibre showed the greatest weight loss (6.65%). In turn, apple fibre had the lowest weight loss (5.21%). In terms of weight loss, it can be observed that in the second stage, the lowest value was observed for chokeberry fibre (13.36%) and the highest for apple fibre (29.89%). Generally, the second stage, from 242.88 to 287.33 \({}^{\circ}\)C, is attributed to the thermal decomposition of the analysed fibres. In the third stage, all fibres showed similar low degradation temperatures, between 340.07 and 344.74 \({}^{\circ}\)C. However, the weight loss was 10.19% for apple fibre and ranged in the case of chokeberry fibre from 5.61 to 9.89% for currant fibre. In general, in the third stage, it is possible to observe the degradation of the carbon residues formed in the second stage, combined with the complex oxidation of these materials. In the fourth stage, all fibres showed similar degradation temperatures, ranging from 422.23 to 425.23 \({}^{\circ}\)C. However, the weight loss in the case of apple fibre was 5.10%, and in the case of currant fibre and chokeberry fibre, from 12.17 to 12.31%. Thermogravimetric analysis (TGA) curves and their first derivatives (dTG) for the pomace are shown in Figure 7 and were examined to assess thermal stability (Table 8). For easier comparison, the dTG curves have been shifted vertically. It can be seen that all analysed pomace showed similar behaviour in the three main stages of weight loss (Figure 7). The first stage was observed up to a temperature of 67 \({}^{\circ}\)C and was associated with the loss of adsorber and bound water. Typically, the first stage, from 25.00 to 200.00 \({}^{\circ}\)C, evaporates water and molecular-weight molecules. The type of fibre influenced this stage. The highest temperature was recorded by apple pomace (67.32 \({}^{\circ}\)C), and the lowest was recorded by chokeberry pomace (66.54 \({}^{\circ}\)C), associated with a lower thermal stability. The greatest weight loss was shown by apple fibres (3.89%). In turn, chokeberry fibre showed the lowest weight loss (6.14%). In terms of weight loss, it can be observed that in the second stage, the lowest value was observed for chokeberry pomace (14.25%) and the highest for apple fibre (24.31%). Generally, the second stage, from 242.45 to 288.30 \({}^{\circ}\)C, is attributed to the thermal decomposition of the analysed pomace. In the third stage, all pomace showed similarly low degradation temperatures, ranging from 343.32 to 453.96 \({}^{\circ}\)C. However, the weight loss in the case of currant was 7.82%, and in the case of chokeberry pomace and apple pomace, it ranged from 4.21 to 4.76%. In the fourth stage, all pomace showed similar