Antioxidants are substances that may protect cells from the damage caused by unstable molecules known as free radicals. Antioxidants such as beta-carotene, lycopene, vitamins C, E, and A interact with and stabilize free radicals and may prevent some of the damage free radicals cause. Antioxidants are capable of inhibiting the oxidation of other molecules, therefore they are reducing agents. In thisresearch, Au (III) was used as oxidizing probe to explorer the reducing capability of antioxidants in different natural food and compare them with processed food. Natural food including fresh carrot, kiwi, orange, strawberry, cranberry, ginger, tomato, apple, juniper berries and Persian lime juices were reacted with Au (III) to produce Gold in form of nanoparticles. When a particle of gold metal is similar in size to wavelengths of visible light (400�750 nm), it interacts with light in interesting ways ranking from orange to deep red color. In these experiments, a solution of 0.1 mM HAuCl4 brought to boiling temperature and then a microfiltered pure and fresh solution fruit juice wasadded to the gold solution along with stirring until it turned to a deep red color. The antioxidants in fruit juice reduce the Au(III) ions to nanoparticles of metallic Au which forms nanoparticle. Similar experiments were done with 100% pure bottled juices. In conclusion the volumes of freshly squeezed juices to reduce certain amount of Au(III) to Gold nanoparticles were less than the volumes of bottled juiced suggesting that the fresh fruits and juices have more antioxidants than the bottled ones.

From food antioxidants to gold nanoparticles: Determination of antioxidants in natural and processed food by gold

243rd National Meeting (2012)

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