# Effect of Microwave-Assisted Processing of Acorn Flour on Muffin Quality
## 1 Introduction  
According to statistical data, the global population is steadily increasing. In 2024, it reached 8.16 billion, and projections indicate that it may rise to 10.18 billion by 2100 [1, 2]. When considered in the context of the ongoing climate crisis--which negatively impacts primary food production and poses a significant threat to global food security [3]--it becomes evident that substantial changes to the current global food system arenecessary [4; 5]. The use of unconventional food sources has been identified as one potential approach to addressing food security challenges [6]. Oak fruits (_Quercus_ spp.) represent an example of such unconventional food sources. They are rich in starch and also contain considerable amounts of dietary fiber, minerals, and bioactive compounds [7; 8; 9; 10]. Historical and archaeological studies suggest that acorns were consumed from prehistoric times through the 19 th and 20 th centuries, typically prepared using relatively simple methods adapted to specific cultural and regional contexts [11; 12; 13]. Despite their historical significance, acorns are rarely used in the modern food industry [9]. However, increasing interest in functional foods--defined as foods that provide additional health benefits beyond their basic nutritional value--and the revival of traditional processing methods have renewed attention to acorns as a potentially valuable dietary component [13]. One of the primary factors limiting the consumption of acorns is their high content of tannins--phenolic compounds responsible for their characteristic astringent and bitter taste. These compounds are natural plant defense compounds that deter herbivores and inhibit premature seed germination [14; 15]. Tannins remain controversial among plant bioactive compounds due to their antinutritional effects and potential health risks when consumed in excessive amounts [15; 16]. Nevertheless, growing evidence supports their preventive and therapeutic roles in human health [14; 17; 18; 19]. Due to their high tannin content, raw acorns are generally unsuitable for direct consumption. However, several traditional methods have been developed to reduce their bitterness. These include prolonged soaking in water, which facilitates tannin leaching, and fermentation processes that promote tannin degradation [12]. Thermal treatments such as roasting, boiling, and drying also contribute to the reduction in tannins but may simultaneously affect the nutritional profile of acorn-based products, including acorn flour [20; 21; 22]. Recent studies have focused on the application of modern processing techniques, such as microwave treatment, in the production of various flours to improve their properties, e.g., whole wheat flour [23], rice flour [24], chickpea flour [25], flaxseed flour [26], and pumpkin flour [27]. Unlike conventional heating methods, microwave heating is volumetric in nature--heat is generated internally throughout the material rather than transferred from an external surface [28; 29]. This process influences the structure and chemical composition of food through several mechanisms, including protein denaturation, structural modification of polysaccharides (affecting digestibility), thermal degradation or release of phenolic compounds, alterations in starch and fiber structures, and a reduction in enzymatic activity, which may slow undesirable reactions such as lipid hydrolysis [29; 30; 31]. The scientific literature reports various effects of microwave processing on tannin content in plant-based raw materials. For example, [PERSON] et al. [32] found that microwave heating for 1-2 min at 9295 MHz reduced tannin content in oilseeds (peanut, sesame, soybean, sunflower, and sunflower) by 8.8% to 24.4%, depending on the material and processing duration. [PERSON] et al. [25] observed a reduction in tannin content ranging from 4.0% to 38.9% in chickpea flour (sattu) treated with microwave power from 450 to 900 W for 5-30 min, accompanied by an increase in total phenolic content from 72.1 to 239.1%. [PERSON] et al.