## 3 Results and Discussion
### Colour of Fruit Fibres and Pomace  
Colour is the most important quality attribute regarding food products because it directly impacts consumer choices and the assessment of the acceptability of food. Therefore, its evaluation is crucial for food application due to the impact on the final product's colour, i.e., snack bars or biscuits when pomace or fibre replaces flour. The results of the colour analysis showed that the apple fibre was characterised by the highest value of the parameter \(L^{\star}\), which is responsible for brightness. The value of this parameter for apple fibre was 69.08. Currant and chokeberry fibres showed a lower value for this parameter, which was 48.18 and 42.16, respectively. Among the pomace, apple pomace had the brightest colour, of which the value of the \(L^{\star}\) parameter reached 57.35. The darkest colours were the chokeberry and currant pomace, of which the values of the \(L^{\star}\) parameter equalled 36.54 and 37.71. It was also found that the fibres had a higher \(L^{\star}\) parameter than pomace derived from the same fruits. The difference between fibre and chokeberry pomace was 5.61; in fibre and apple pomace, 11.73; and in fibre and currant pomace, 10.47. The proportion of the colour parameter \(L^{\star}\) in individual pomace and fibres is shown in Table 4. The currant fibre characterised the highest parameter, \(a^{\star}\), representing red colour. The value for this material reached 14.41. Chokeberry fibre, second in descending order regarding this parameter, reached a value of 12.70. On the other hand, apple fibre had the lowest share of parameter \(a^{\star}\), which, in this case, was only 8.05. Comparing the results of pomace colour, it was observed that those obtained from currant, just as in the case of the fibres, reached the highest value of the \(a^{\star}\) parameter. This means that the highest proportion of the colour red characterises both fibre and currant pomace. The lowest share of this parameter was characterised by chokeberry pomace, which reached a value of 8.53. Parameter \(b^{\star}\) is equivalent to the yellow colour. The highest proportion of the described parameter was observed in apple fibre. The value of parameter \(b^{\star}\) was equal to 24.29. Chokeberry fibre and fibre had a much smaller share of yellow colour. The values of parameter \(b^{\star}\) of the tested fibres reached 4.73 and 5.37, respectively. It was also observed that the fibres, compared to pomace extracted from the same fruits, are characterised by a higher proportion of the \(b^{\star}\) colour parameter. Apple pomace showed a similar value of the \(b^{\star}\) colour parameter compared to the fibre of the same origin. The described parameter was \begin{table}
\begin{tabular}{c c} \hline \hline
**Sample** & **Water Activity** \\ \hline
**chokeberry fibre** & 0.424 \(\pm\) 0.000 \\
**apple fibre** & 0.341 \(\pm\) 0.000 \\
**currant fibre** & 0.324 \(\pm\) 0.000 \\
**chokeberry pomace** & 0.321 \(\pm\) 0.000 \\
**apple pomace** & 0.327 \(\pm\) 0.000 \\
**clack currant pomace** & 0.364 \(\pm\) 0.000 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Water activity in the tested fibres and fruit pomace. equal to 21.81. Chokeberry pomace reached a value of 4.38, while the lowest value, 3.91, was characterised by currant pomace. [PERSON] et al. [22] studied the colour parameters of apple pomace. The material analysed in the cited work was brighter, as indicated by a 20.50 higher value of the \(L^{\star}\) colour parameter. A lower proportion of red colour also characterised the apple pomace, as the \(a^{\star}\) parameter reached a value of 2.60, while in the present work, the value was equal to 9.22. In contrast, both pomaces were characterized by a very similar proportion of yellow colour. The \(b^{\star}\) parameter measurement result for the material [PERSON] et al. [22] studied was 2.50, while the extrudate studied in the present work was 21.81.