The study also identifies the chemical compounds present in acorns, which could help determine which are best for consumption, thus boosting the consumption of an underutilized and undervalued food.

The holm oak is one of the most representative trees of Mediterranean forests and of the dehesa wooded pastureland system. Its fruit, the acorn, is used mainly to feed Iberian pigs. However, acorns continue to be an underused and often undervalued food, despite boasting nutritional properties making them highly valuable for human consumption. They stand out for their high starch content, a fatty acid profile similar to that of olive oil, an absence of gluten, and significant amounts of fiber and iron. They also contain a wide variety of phenolic compounds and other secondary metabolites with recognized antioxidant, anti-inflammatory, and antimicrobial activity, which underscores their potential as a healthy and functional food. This has been verified—consistent with previous studies—by the AGR-164 research group at the University of Cordoba, in collaboration with the Agroindustry and Food Quality group at the IFAPA Alameda del Obispo center, after analyzing the nutritional and nutraceutical profile of acorns of 14 specimens of holm oak.

Despite the favorable properties that acorns feature, they also present high variability, as the holm oak is a species that has not been domesticated. This is why there are as many types of acorns (bitter, sweet, large, small) as there are holm oaks. Because it is difficult—based on size or flavor alone—to identify the acorns most suitable for consumption, the team used various holistic and targeted techniques for the phytochemical characterization and identification of bioactive compounds in holm oak acorns.

Using several techniques—such as near-infrared spectroscopy (NIRS), colorimetric reactions, high-performance liquid chromatography (HPLC), and mass spectrometry (LC-MS/MS)—and despite having worked with a limited number of specimens, the team identified two main groups of acorns: large ones lacking bitterness, and medium-sized ones that are highly bitter. Among their most noteworthy characteristics are their high starch content, a predominance of unsaturated fatty acids, and elevated levels of calcium and sodium. Their metabolomic profiles proved to be highly specific to each tree, and several recently reported compounds with potential bioactive properties were detected.

A considerable number of metabolites of microbial origin were also identified, demonstrating the presence of a diverse microbiome associated with the seeds, which could even influence the acorns’ bitterness levels.

The study, published in the journal Future Foods and forming part of the doctoral dissertation by Marta Tienda Parrilla, marks a step toward facilitating the consumption of acorns as a human food source. Several lines of inquiry remain open, however. For example, researchers could evaluate which compounds found in acorns are beneficial to human health by determining their biological activity, or develop a catalogue of holm oaks with notable characteristics. Based on these selections, it would be possible to design domestication programs to produce trees with favorable genetic profiles, capable of yielding acorns suitable for human consumption in the future. This domestication would not entail selecting certain species at the expense of others, or eliminating genetic variability, but rather creating a catalogue of varieties accepted for consumption or for industrial use.

Reference

Marta Tienda-Parrilla, Cristina López-Hidalgo, Mónica Sánchez-Parra, José Luis Ordóñez-Díaz, José Manuel Moreno-Rojas, María-Ángeles Castillejo, Jesús V. Jorrín-Novo, María-Dolores Rey, “Phytochemical and metabolomics analysis of Quercus ilex acorns reveals substantial intraspecific variation, high nutritional and nutraceutical potential and rich associated microbiome,” Future Foods, Volume 12, 2025, 100754.