From Forest to Table: Optimizing the Nutritional Value of Acorns through Effective Tannin Extraction

The acorn, a fruit of the Quercus genus, is abundant in Portugal and offers a high nutritional content, including essential minerals and vitamins, unsaturated fatty acids, and bioactive compounds like tannins, phenolic acids, and flavonoids ^[1]. Despite their antioxidant properties, excessive consumption of tannins can cause health problems due to their effect on protein bioavailability ^[2]. This study evaluates two extraction techniques: water immersion at room temperature for seven days and thermal hydrolysis via boiling for 30 minutes and their effects on acorn's tannin and mineral content. The results reveal that both extraction methods are viable options for extracting tannins. However, they also reduce some important minerals, such as potassium (K), zinc (Zn), calcium (Ca), and iron (Fe). In conclusion, while acorns hold potential as a nutritious food source, effective tannin extraction methods like water immersion must be employed to maximize their health benefits and minimize potential risks.

Acknowledgments: This work received financial support from REQUIMTE/LAQV-UIDB/50006/2020, UIDP/50006/2020 and LA/P/0008/2020, financed by FCT/MCTES.

References:

[1] A. Pasqualone et al., “Effect of acorn flour on the physico-chemical and sensory properties of biscuits,” Heliyon, vol. 5, no. 8, 2019, doi: 10.1016/j.heliyon.2019.e02242.

[2] M. M. Mostafa, E. Ali, M. Gamal, and M. A. Farag, “How do coffee substitutes compare to coffee? A comprehensive review of its quality characteristics, sensory characters, phytochemicals, health benefits and safety,” Food Bioscience, vol. 43. Elsevier Ltd, 2021. doi: 10.1016/j.fbio.2021.101290.