## 3 Results and Discussion
### Changes in the Colour of Flour and Baked Product Crumb as Affected by Additives
Changes in the chromatic coordinates a* and b* further highlighted the visual differences caused by the tested additives. Apple flour increased both the a* and b* values, shifting the colour towards warmer yellow-red hues. In the case of the composite flour blend containing 15% apple flour, the a* value reached 3.0 and the b* value 12.7, indicating a dominance of intense yellow-orange tones. In the crumb of the baked product enriched with the same amount of apple flour, the a* value increased further to 9.4 and the b* value to 25.8, reflecting an even more pronounced shift in crumb colour towards saturated red-yellow hues. This intensified colouration is attributed to enhanced non-enzymatic browning reactions--such as Maillard reactions and caramelisation--occurring during the baking process. These results are consistent with the findings of [PERSON] et al. [37; 39], who reported that in baked bread products containing flours derived from apple pomace--rich \begin{table}
\begin{tabular}{c c c c} \hline
**Type of Flour** & **Proportion** & **Flour (L*)** & **Crumb of the Baked Product (L*)** \\ \hline Wheat flour & 100\% & 91.9 \({}^{\text{h}}\) * & 72.8 \({}^{\text{k}}\) \\ \hline  & 5\% & 88.4 \({}^{\text{fgh}}\) & 51.0 \({}^{\text{fg}}\) \\ Wheat flour + red oak & 10\% & 78.4 \({}^{\text{b}}\) & 48.3 \({}^{\text{def}}\) \\  & 15\% & 73.4 \({}^{\text{a}}\) & 43.2 \({}^{\text{ab}}\) \\ \hline  & 5\% & 87.0 \({}^{\text{efg}}\) & 55.4 \({}^{\text{h}}\) \\ Wheat flour + pedunculate oak & 10\% & 82.5 \({}^{\text{cd}}\) & 49.7 \({}^{\text{efg}}\) \\  & 15\% & 79.6 \({}^{\text{bc}}\) & 43.7 \({}^{\text{bc}}\) \\ \hline  & 5\% & 85.4 \({}^{\text{def}}\) & 55.5 \({}^{\text{h}}\) \\ Wheat flour + sessile oak & 10\% & 82.3 \({}^{\text{cd}}\) & 47.2 \({}^{\text{de}}\) \\  & 15\% & 78.1 \({}^{\text{b}}\) & 46.0 \({}^{\text{bcd}}\) \\ \hline  & 5\% & 87.2 \({}^{\text{efg}}\) & 58.8 \({}^{\text{1}}\) \\ Wheat flour + horse chestnut & 10\% & 85.2 \({}^{\text{def}}\) & 52.5 \({}^{\text{g}}\) \\  & 15\% & 82.5 \({}^{\text{cd}}\) & 40.6 \({}^{\text{a}}\) \\ \hline  & 5\% & 90.1 \({}^{\text{bh}}\) & 59.4 \({}^{\text{i}}\) \\ Wheat flour + sweet chestnut & 10\% & 88.5 \({}^{\text{fgh}}\) & 56.5 \({}^{\text{hi}}\) \\  & 15\% & 86.8 \({}^{\text{efg}}\) & 46.4 \({}^{\text{cd}}\) \\ \hline  & 5\% & 90.9 \({}^{\text{h}}\) & 68.4 \({}^{\text{j}}\) \\ Wheat flour + apple & 10\% & 89.6 \({}^{\text{bh}}\) & 58.7 \({}^{\text{i}}\) \\  & 15\% & 84.7 \({}^{\text{de}}\) & 50.6 \({}^{\text{fg}}\) \\ \hline \end{tabular} \({}^{\text{*}}\) Mean values in the same column followed by different letters indicate statistically significant differences according to NIR test (\(p\leq 0.05\)).  
\end{table} 
Table 1: L* colour parameters of wheat flour blends supplemented with 5%, 10%, and 15% of alternative flours (oak, chestnut, horse chestnut, apple) and of the **crumb** of the baked products prepared from them. in natural sugars and phenolic compounds--there was a noticeable increase in both a* and b* values. This colour shift towards red and yellow tones was attributed to the intensification of non-enzymatic browning reactions, such as Maillard reactions and caramalisation, occurring during baking. Sweet chestnut flour caused a balanced increase in a* and b* values, albeit to a lesser extent than apple flour. At a 15% concentration, the a* value reached 2.4 and the b* value 9.9, resulting in mild warm tones dominated by red-yellow hues. These colour coordinates are comparable to those observed by [PERSON] et al. (2018) in final gluten-free bread products containing chestnut flour, where similar chromatic shifts were reported as a result of flour pigmentation and baking-induced browning reactions. In contrast, oak flours--particularly red oak flour--significantly increased a* values while reducing b*, producing darker, cooler, reddish-brown tones. For flour with a 15% addition of red oak flour, the a* value increased to 7.6, while the b* value dropped to 3.3. This observation corroborated the findings of [PERSON] et al.