Can the vitamin c concentration in fresh orange juice increase after being boiled?

Question

So I'm doing an experiment in Chemistry class for my assignment. The experiment is to boil orange juice at 2 minutes, 4 minutes and 8 minutes and investigate the vitamin concentration by titrating it. Given the research online, I expected the vitamin c concentration to decrease, but this was not the case. Some information about the experiment:

- we covered the beaker's top that contained orange juice with a paper towel so the steam wouldn't escape

- when titrating it, we put distilled water with the orange juice

- we used iodine in the burette

 

The result of titrating fresh raw orange juice was around 14ml of iodine

When we boiled it at 2 min, the result was 16

And this gradually increased the longer our orange juice was boiled.

 

Why is this happening?

 

Thanks

 

Answer 1

Claudia, 

that is strange, you would expect lower concentrations when orange juice is boiled

Orange juice contains different acids: most important ascorbic acid (Vit C), citric acid but also malic acid and oxalic. Maybe some acids are bonded in orange juice and are released when the orange juice is heated/boiled. So, that in the end the final concentration of acids increases.

 

interesting topic,

good luck