2.1. Plant material and sample preparation
About 20 kg of fresh oranges (Citrus sinensis) of Maltese variety were collected in March 2012 from Manzel Bouzalfa (Nabeul,Tunisia) in their commercial maturity. All fruits were of eating quality, and without blemishes, or damage. On arrival at the laboratory, the orange fruits were immediately washed using tap water, and peeled. The remaining orange peel accounted for approximately 40% of the total fruit. The peels were stored at −80◦C before any further treatments. Orange peels were dehydrated using a freeze dryer (CHRIST Alpha 1-2 LD, France)for 72 h (at −50◦C and 0.001 m bar) and then finely ground using a coffee grinder (Moulinex®, France) to achieve a standard sizeof particles of ∼0.315 mm. The orange peel powder was placed in vacuum packaging bags and stored in a freezer maintained at 4◦C before experiments.