Antioxidant Testing

[tori__w]

The science fair experiment that I will be conducting involves testing if adding milk to tea and coffee reduces the antioxidant levels in the tea and coffee. I will test it by using the browning apple method. Do you know of another way to test for antioxidants or an accurate way to measure apple-browning? Thanks!

[SciB]

Hi Tori,

I think you have come up with a great question—to see whether milk alters the antioxidant effects of tea and coffee. Unfortunately this is a tough question to answer. The apple-browning method for antioxidants works well, but only for clear solutions like vitamin C or citric acid. If you applied tea or coffee to an apple slice it would color it brown and prevent you from accurately measuring the browning reaction.

You just might be able to use green tea and take out the tea bag while the color was still pretty light. You could do a test and see how dark the tea made the apple slice and then see how dark the apple got from browning. If the color change from browning is fairly strong, then you might be able to see a difference. You would have to first compare an apple slice dipped in water with one dipped in green tea cooled to room temperature. If there is no difference in the browning with tea treatment then your method is not sensitive enough.

There’s still one big question—how do you measure browning? Well, there are lab instruments that can measure the color intensity of a surface, but unless you have access to a research university or testing lab, you probably won’t be able to use one of these.

If you have a scanner, however, you can scan the apple slices creating a color image and then quantitate the color density using a free computer program called ImageJ [http://imagej.en.softonic.com/]. I think this would work with images of apple slices. I have only used it to analyze microscopic images but the principle is the same. There’s a bit of a learning curve in using it but I can help you with the tutorials.

The first thing to do, though, is to see whether the tea has any observable affect on browning. If the tea has enough antioxidant to inhibit browning then you will be able to see it by eye. If there’s no observable difference then you probably can’t use the apple method. There are some chemical methods that could be used but you would need access to a molecular biology laboratory.

I hope this information helps. Please keep posting and we will keep trying to steer you into a great project.

Best wishes,

Sybee