###### Abstract  
The increasing interest in fibre-enriched and functional bakery products has led to the exploration of novel plant-based ingredients with both technological functionality and consumer acceptance. This study evaluates the effects of incorporating flours derived from apple (_Malus domestica_ cv. Oberlander Himbeenerpfel), sweet chestnut (_Castanue sativa_), horse chestnut (_Aesculus hippocampusatum_), and red, sessile, and pedunculate oak (_Quercus rubna_, _Q. petraea_, and _Q. robur_) into wheat bread at 5%, 10%, and 15% substitution levels. The impact on crumb structure, crust colour, textural parameters (hardness, adhesiveness, springiness), and sensory attributes was assessed. The inclusion of apple and sweet chestnut flours resulted in a softer crumb, lower adhesiveness, and higher sensory scores related to flavour, aroma, and crust appearance. In contrast, higher levels of oak- and horse-chestnut-derived flours increased crumb hardness and reduced overall acceptability due to bitterness or excessive density. Apple flour preserved crumb brightness and contributed to warm tones, while oak flours caused more intense crust darkening. These findings suggest that selected non-traditional flours, especially apple and sweet chestnut, can enhance the sensory and physical properties of wheat bread, supporting the development of fibre-rich, clean-label formulations aligned with consumer trends in sustainable and functional baking. alternative flours; acorn supplementation; sweet chestnut powder; apple flour; crumb texture; consumer acceptance 2025  
17 July 202518 July  
with animal feed. However, for thousands of years, they constituted a significant component of traditional diets across various cultures. For example, acorns were consumed in Sardinia, Spain, Turkey, Asia, North America, and Poland, prepared in the form of pyridges, bread, cakes, oils, and beverages [4; 5; 6; 7; 8]. Similarly, edible chestnuts and fruit by-products such as apple pomace played an important role in traditional diets and are now regaining attention in the context of sustainable food processing and the circular economy [9; 10]. Flours produced from acorns (_Quercus_ spp. ), sweet chestnuts (_Castanae sativa_), horse chestnuts (_Aesculus hippocastanum_), and apples (_Malus domestica_) possess high nutritional value, and their application in baking aligns with current health-oriented trends. All these raw materials are rich in dietary fibre, phenolic compounds, antioxidants, and essential minerals [11; 12; 13]. Chestnut flour contains substantial amounts of complex carbohydrates as well as vitamins and volatile compounds that enhance the flavour and aroma of bread [14; 15]. Apple flour, particularly that derived from apple pomace--a by-product of juice production--is naturally gluten-free and represents a valuable ingredient in the manufacture of functional baked goods [3]. Acorn flour, in turn, aside from its high phenolic and starch content, may exhibit a characteristic astringent aftertaste due to the presence of tannins [16]. Acorn flour is obtained from the nut after removing the hard seed coat (pericarp), which constitutes up to 34% of the fruit's mass and is not used in processing [17; 18; 19]. To date, no studies have addressed the use of whole acorns, including the pericarp, in flour production, despite their potential to promote the more complete utilisation of the raw material [20]. Globally, fruit juice production generates several million tonnes of apple pomace annually. In some countries, such as India, only about 1% of this residue is utilised as animal feed or dried product. The vast majority is discarded in landfills or spread on fields, which may lead to serious environmental issues and soil contamination [10]. In this context, the incorporation of apple flour into bakery products represents an important strategy for waste valorisation and the sustainable use of agro-industrial by-products.