National University of Singapore
Food Science & Technology
Antioxidants in Vegetables
Materials:
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2 pestle and mortar
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weighing balance (up to 0.01 g is needed to balance centrifuge tubes)
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pipettes
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deionised (DI) water
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10 blue cap tubes
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cuvettes
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spectrophotometer
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centrifuge tubes (those small ones x5)
(Top) Determination of antioxidant activitity in vegetables
Preparation of DPPH assay:
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Prepare a 0.10 mM solution of DPPH in 100% methanol
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Grind about 0.1 g fresh vegetable in 1.0 ml DI water. Centrifuge at 10 000 rpm for 10 min.
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An aliquot of 50 μl of aqueous extract is then added to 2.95 ml of the 0.10 mM DPPH. Water is used to replace the extract to act as control in this experiment.
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Pure methanol solution is used as the Blank solution.
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Incubate the extract-DPPH mixtures in the dark for 30 min at room temperature before the absorbance at 517 nm is read.
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Free radical scavenging activity is calculated as ascorbic acid equivalent per gram fresh weight vegetables by using ascorbic acid standard curve.