Sustainable Co-Extraction of Starch and Tannins from Quercus robur Acorns Using Pulsed Electric Field Technology and Evaluation of Starch Gelatinization Properties

Pulsed electric field (PEF) technology was used as a green extraction method for the simultaneous recovery of starch and polyphenols from acorns using water as extraction solvent, and the gelatinization properties of the extracted starch were compared with those of a starch obtained via alkaline extraction. Results showed that the electric field intensity had a significant negative quadratic effect on the antioxidant activity and hydrolyzable tannin content, whereas it had a positive quadratic effect on the starch yields. Time had no significant effect on the starch yields but had a negative quadratic effect on the phenolic and hydrolyzable tannin contents and antioxidant activity. The extraction condition that allowed the highest starch and polyphenol contents with the greatest antioxidant activity was 0.1 kV/cm for 63.3 µs, with a desirability of 87%. In comparison to alkaline extraction, PEF increased tannin extraction by 11-fold, highlighting its potential to produce tannin-rich extracts suitable for leather manufacture. Although the starch yield was 30% lower than that obtained via alkaline extraction, the PEF-isolated starch is a cleaner and safer ingredient for human consumption. The alkaline starch had a significantly higher solubility than the PEF-isolated starch, but both had similar swelling power.