## 4 Conclusions  
The addition of apple and sweet chestnut flours significantly improved the rheological properties of wheat dough, particularly in terms of dough stability and development time, indicating their positive technological potential in bread formulations.  
Farinographic analysis showed that increasing apple flour levels reduced water absorption, which was attributed to the lower water-binding capacity of apple starch and fibre compared to gluten-rich wheat flour.  
Colour measurements demonstrated that apple and sweet chestnut flours had a less intense darkening effect than acorn and horse chestnut flours, with red oak flour producing the darkest crust due to its high phenolic content.  
Textural analysis revealed that sweet chestnut flour maintained crumb elasticity and springiness, while higher levels of acorn and horse chestnut flours increased crumb hardness and adhesiveness.  
Sensory evaluation confirmed that apple and sweet chestnut flour additions (especially at 10-15%) resulted in high consumer acceptability, enhancing flavour, aroma, and crust appearance, while higher levels of acorn flour negatively affected taste due to bitterness.  
Up to 15% apple or sweet chestnut flour can be successfully used in wheat bread production to improve nutritional value and sensory attractiveness without compromising technological quality.  
Acorn flour at 5% substitution can be considered a viable ingredient for rustic or wholegrain-style breads, where darker colour and denser texture are desirable, but higher levels should be avoided due to taste issues.  
The use of flours obtained from underutilised plant materials enables the partial replacement of wheat flour in a sustainable and health-oriented manner, supporting the development of clean-label, fibre-enriched bakery products aligned with current consumer trends.  
Among all the tested additions, the most acceptable substitution levels were 10-15% for sweet chestnut and apple flour, while the use of acorn flour should be limited to 5%, as higher doses negatively impacted flavour and crumb structure due to increased compactness and bitter notes.  
Conceptualization, F.S. and I.O.; methodology, F.S., I.O., M.S. and R.I.; software, F.S.; validation, F.S., I.O., M.S. and R.I.; formal analysis, F.S., I.O., M.S. and R.I.; investigation, I.O.; resources, F.S. and I.O.; data curation, F.S.; writing--original draft preparation, F.S., I.O., M.S. and R.I.; writing--review and editing, F.S. and I.O.; visualisation, F.S.; supervision, I.O.; project administration, I.O. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the State Forests Forest Fund in cooperation with Wolinski National Park and by a grant from the West Pomeranian University of Technology (No. 518-07-014-3171-03/18).  
Ethical review and approval were waived for this study due to its nature as a food technology and formulation research project. This study did not involve human participants, animal subjects, or the collection of personal or health-related data. Sensory evaluation was conducted by trained panellists under standard food testing conditions without health interventions.  
Not applicable.  
All results presented in this publication were developed based on original data available from the authors upon reasonable request.  
The authors declare no conflicts of interest.