Impact of leaching on the nutritional composition of acorn species

Historically, acorns have been used as a food source; however, nowadays, they are neglected despite their nutritional value. One of the barriers is their high tannin content, which leads to bitterness, reduced nutrient absorption, and may prevent digestion and liver toxicity. This study explored the impact of leaching on the nutritional and physicochemical properties of three endemic Portuguese species ( Quercus pyrenaica , Quercus rotundifolia , and Quercus robur ). The findings revealed that leaching significantly affected flour’s pH, acidity, water activity, and macronutrient profile, which overall leads to reductions in these parameters. Moreover, although rich in insoluble fiber, with potential gut health benefits, substantial fiber losses occurred. Fatty acid analysis showed high oleic, linoleic, and palmitic acid levels, with favourable atherogenic and thrombogenic indices, indicating high fat quality. Leaching also significantly decreased soluble sugars and reduced mineral content by approximately 90 %. Overall, these findings emphasise the acorn's potential as a sustainable and nutritious food source. Although leaching reduced soluble sugars, minerals, and part of the fiber and lipid fractions, key macronutrients and a favourable fatty acid profile were preserved, supporting the use of acorn flours in functional food applications. • Leaching affected acorns’s pH, acidity, water activity, and macronutrient profile. • Leached acorns remained a good source of fiber and maintained a favourable Na/K ratio. • All leached acorn samples showed high levels of oleic, linoleic, and palmitic acids. • Overall, a favourable nutrient profile was maintained after leaching.