The antioxidant activities of both strawberries and bitter orange peels were investigated using DPPH-ESR system and conjugated diene methods. The obtained data showed both excellent antioxidant and antiradical activities of their freeze dried extracts. Bitter orange peels showed also an excellent thermal stability, followed by strawberries. Their methanolic extracts were furtherly fractionated by using GC-MS technique to identify the phenolic compounds responsible for the antioxidative properties of these previously studied materials. It is suggested that bitter orange peels could be applied as a safe natural antioxidant thereby an additional by- product could be achieved. Various methods for pretreatment and drying were tested and the most suitable processing conditions were blanching (10s) and vaccum dehydration at 40^oC for 7 hrs, then ground into a fine powder. Osmotic pretreatment and vaccum dehydration were also proved their applicability to be used for preserving the components responsible for the antioxidant activities in strawberries.