Odwalla Pomegranate Juice

I’ve been really curious about the UV/Vis Spectrum of Pomegranate juice, so I finally broke down and ran the spectrum.  I bought commercially available Odwalla Pomegranate Juice from Safeway and diluted 0.50 mL of this juice in 100 mL (+/- 1 mL) of distilled H2O.  It is approximately 200 to 1 dilution. This commercial juice is also mixed with Chokecherry, Elderberry, Blueberry, Black Currant, and Apple juices, as well as a bit of citric acid. I’m going to try to get plain pomegranate juice for comparison.

I took a bit of the diluted soln and added some metals to it to see if there were any shifts in peak wavelength.  The two shoulders (~250 and ~350 nm) were unchanged in wavelength and extinction, but the extinction of the peak at 193 nm was increased. The metals were SnCl2, ZnCl2, FeCl3, and MnOAc2.  The Mn(II) Acetate has a fair extinction at ~195 nm but drops sharply at ca 200 nm. In all cases the shoulders remained. I would have to run a control to see if the consistent uptick in extinction at 193 nm is due to the metal ions.

When the dilute juice soln was treated with a few grains of NaIO4, the shoulders disappeared and the soln promptly took a clear yellow color. So it should be possible to follow the oxidative degradation of these solutions by UV/Vis.  Since the juice is a complex mix of chromaphores, there is no telling what species are involved and what exactly is being oxidized.  I’m sure that someone has sorted out what is in pomegranate juice. 

This is what I did with a saturday afternoon.