Evaluation of the Physicochemical, Nutritional, and Antioxidant Activities of Acorn from Quercus spp.: A Comparative Study Between Algerian and Tunisian Varieties

The Mediterranean basin's abundance of oak trees yields a considerable quantity of acorns in the woodlands each year.

This study evaluates and compares the physicochemical, nutritional, and antioxidant activities of acorns from four Quercus species: two Algerian varieties, Quercus suber and Quercus ilex (QSA, QIA), and two Tunisian varieties, Quercus suber and Quercus ilex (QST, QIT).

For the Algerian varieties the physicochemical compositions, phytochemical compositions, and antioxidant capacity are as follows: total sugars (76.01–52.78%), proteins (7.70–6.72%), fat (13.95–4.15%), total phenolic (516.36–397.79 mg GAE/g DM), condensed tannins (4.64–6.05 mg CE/g DM), (DPPH IC₅₀ = 0.01–0.015 mg/mL, ABTS IC₅₀ = 0.008–0.02 mg/mL, FRAP = 798.5–123.3 mmol Fe(II)/mL DM, and TAC = 38.1–21.8 mmol AAE/mL DM), respectively in Quercus suber and Quercus ilex species. However, corresponding values the Tunisian varieties were as follows: total sugars (59.62–64.22%), proteins (5.01–7.58%), fat (8.05–5.23%), total phenolic (287.23–460.91 mg GAE/g DM), condensed tannins (5.34–6.78 mg CE/g DM), (DPPH IC₅₀ = 0.013–0.02 mg/mL, ABTS IC₅₀ = 0.016–0.014 mg/mL, FRAP = 68.4–133.3 mmol Fe(II)/mL DM, and TAC = 13.7–22.3 mmol AAE/mL DM), respectively in Quercus suber and Quercus ilex species. According to Principal Component Analysis, the Quercus Suber Algerian (QSA) displays distinct characteristics compared to other Quercus species. These findings suggest that an excellent source of naturally occurring physicochemical and bioactive compounds is the acorn oak tree.

This study makes a significant contribution to acorn valorization. New uses for these acorn extracts, such as in the nutraceutical or food industries, may be explored.