EXPLORING THE POTENTIAL OF QUERCUS ROBUR KERNEL AND SHELL FOR NOVEL FOOD APPLICATIONS

Despite their abundance in Portugal, acorns remain underutilized, with only 1% used in human diets. As sustainable, gluten-free, and nutrient-rich food, acorns align well with current consumer trends. Additionally, acorn by-products contain valuable bioactive compounds (e.g., phenolics) with health-benefiting properties, presenting opportunities for waste upcycling. This work aimed to characterize the kernel and shell of an endemic Portuguese species - Quercus robur - provided by LandraTech, with the goal of fostering acorns valorization through innovative food applications, towards circular economy.

Kernel (KF) and shells (SF) flours from Quercus robur were analyzed for physicochemical, nutritional, and antioxidant properties, revealing distinct differences between them. The kernel and shell pH were 5.01 and 4.95, respectively, with acidity at 0.089±0.002 g H₂SO₄/100 g dry weight (DW) for KF, and 0.051±0.002 g H₂SO₄/100 g DW for the SF. Mineral analysis showed KF had higher potassium (713.06±58.47 mg/100 g DW), phosphorus (71.87±5.47 mg/100 g DW), and magnesium (39.06±5.07 mg/100 g DW) contents, while SF was richer in potassium (588.91±41.51 mg/100 g DW), calcium (245.92±12.28 mg/100 g DW), and magnesium (66.34±5.60 mg/100 g DW) levels. The samples had similar humidity (SF:10.98±0.00%; KF:9.58±0.01%) and ash content (SF:1.64±0.05% DW; KF:1.95±0.20% DW). KF showed higher protein and lipid content (6.09±0.22% and 6.08±0.78% DW) than SF (2.49±0.16% and 1.67±0.79% DW), while SF had more carbohydrates (83.22±0.00% vs. 76.3±0.00% DW). The total phenolic compounds were slightly higher in KF (2.83±0.19 mg GAE/mL) than in SF (0.95±0.08 mg GAE/mL). Both ABTS and DPPH assays showed greater antioxidant activity in KF aqueous extracts (21.24±2.59 and 24.76±1.99 µmol TE/mL, respectively) than in SF (7.76±0.95 and 5.51±1.08 µmol TE/mL, respectively).

         Concluding, Quercus robur by-products valorization highlights these raw materials’ potential for sustainable and innovative food applications. This work emphasizes the importance of exploring underutilized residues as viable resources for the food industry, promoting circular economy.