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I am in high school, and I would like to do an experiment on this for a project.

I've done quite a bit of research into the different methods I could use (see 2.4.2 here) but I still cannot find enough information to formulate a hypothesis. It would be useful iff you could point me in the right direction. So, how does heat affect how much flavonoids are present in commercially available orange juice? (without pulp)

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That's an nteresting idea, but you still have to narrow your research. Do you want to study the influence of weather patterns on the production of flavonoids by a particular variety of oranges? Or how the extraction temperature influences flavonoid concentration in the juice? Or how finished product storage influences degradation of flavonoids? –  CHM Jun 28 '12 at 0:44
    
I want to test the effect of storage temperature on the degradation of flavonoids. My teacher recently bought an electronic water bath that I can use which accurately sets the temperature to +/- 0.1C. I was thinking I could heat up the orange juice for about 10-15 mins(in a test tube, ensuring the same time period for the temperatures I set) and test for the amount of flavonoids after that period of time using colorimetry. –  Adi Jun 28 '12 at 0:50
    
This should be of interest: dx.doi.org/10.1016/j.chroma.2006.01.019 –  CHM Jun 28 '12 at 1:16
    
@Adi, determination of flavonoid content seems like it should be a pretty standard food chemistry technique. The method described in the paper you linked seems unusually complex. It would help to know what instruments or equipment you have access to. Based on CHM's comment, you should be able to do this more simply with access to an HPLC with a UV-Vis detector. –  Ben Norris Jun 28 '12 at 2:36
    
Trouble is I don't have access to HPLC. I'm on a budget of a high school student, so this is the best I can do. I have access to a spectrophotometer and an electronic water bath. –  Adi Jun 28 '12 at 18:09
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1 Answer

Orange juice is often subjected to temperature variation during processing, pasteurization, storage and refrigeration at 4$^{\circ}$C. According to some research, there appears to be a dramatic decrease in the concentration of certain flavonoids at storage temperatures especially above 20$^{\circ}$C.

A variety of flavonoids found in orange juice includes didymin, eriocitrin, hespertin, narirutin, poncirin, apigenin and neoeriocitrin.

Effective analytical methods used to identify and quantify individual flavonoids include gas chromatography mass spectroscopy (GCMS) and high-performance liquid chromatography (HPLC).

Whilst chromatography is the most effective method of identifying specific flavonoids, you may be interested to know that ultra-violet spectrophotometry has been used to measure total flavonoid content before & after treatment.

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