Comparative Nutritional, Rheological, and Lipid Profiling of Acorn Flours from Seven Quercus Species: A Scientific Framework for Functional Food Applications

Acorns are an underutilized natural resource with significant potential for sustainable food systems. This study evaluates the nutritional composition and lipid profile of acorn flours from seven Quercus species (Q. pubescens, Q. ilex, Q. cerris, Q. petraea, Q. robur, Q. rotundifolia, and Q. suber) collected in the Iberian Peninsula and Croatia across different harvest years. Proximate composition, including moisture, ash, protein, lipids, total dietary fiber, sugars, and carbohydrates, was determined using standard AOAC methods, and fatty acid profiles were analyzed by gas chromatography. Rheological properties measured with a micro-visco-amylograph (MVA) revealed significant interspecific differences in viscosity and paste stability, reflecting intrinsic structural variability in the starch fraction among the studied species. The results revealed notable variability among species, sample types, and collection conditions. Acorn flours were characterized by high carbohydrate content (up to 74.8% dw), moderate lipid levels (reaching 16.9% dw in Q. pubescens flour), and low protein content, while shells exhibited markedly higher dietary fiber values (up to 77.0% dw in Q. robur shell). Lipid profiles were dominated by unsaturated fatty acids, particularly oleic (up to 63.7%) and linoleic acids. The differences observed between samples reflect cumulative variability that may be associated with species, geographical origin, harvest year, and processing conditions, although these factors remain confounded in the current study. Because of the confounded sampling design, observed differences represent combined population diversity and should be validated in future balanced trial designs. These findings highlight the high nutritional density of acorns as sustainable, gluten-free ingredients and provide a scientific framework for their industrial use in developing novel functional foods and circular economy models.