For l-ascorbic extraction, frozen pulverised OP peels (2 g) were mixed with 20mL of the extraction solution (3% metaphosphoric acid (Sigma–Aldrich) –8% acetic acid (Chem-Lab.) and the preparation was subjected to intensive agitation (in ice and darkness) with a four blade blender (Braun ZK100, Kronberg im Taunus, Germany) for 1min.