Physicochemical Characterization of Acorn Flour (Quercus spp.) for Its Potential Application as a Natural Pharmaceutical Excipient

Background/Objectives: Acorn flour has attracted attention as a potential starch-based excipient, yet comprehensive data on its powder properties and compaction behaviour remain limited. This study aimed to characterise the physicochemical properties and tableting performance of raw acorn (Quercus spp.) flour and to critically assess its viability for direct compression. Methods: Native flour was characterised for particle size distribution, moisture content, bulk and tapped densities, and flowability. Tablets of pure flour and binary mixtures containing 10% w/w paracetamol were compressed at 10 kN. Tablet quality was evaluated in terms of hardness, friability, disintegration time, and dissolution profile. Results: The flour exhibited particle size distributions of d10 = 13 µm, d50 = 54 µm, and d90 = 413 µm, with a loss on drying of 5.67% w/w. Flow properties, however, were unfavourable: Carr’s index of 35.9% and Hausner ratio of 1.56 classify the material as having very poor flowability, effectively precluding direct compression without modification. Pure flour compacts achieved moderate hardness (60–70 N at 10 kN) but failed friability testing, with values exceeding the pharmacopoeial limit of 1%. Conclusions: Overall, raw acorn flour displays cohesive behaviour under compression but suffers from inadequate flow properties and insufficient tablet mechanical strength. These findings indicate that substantial formulation or processing interventions are required before acorn flour can be considered a viable excipient for direct compression applications.