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.
Lamentations on Chemistry 
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January 7, 2007 at 1:08 pm
Ψ*Ψ
I always thought photostability studies were fun. I’d much rather do them with juice than solutions of colored things in 1,2-dicholorobenzene, though. Juice smells infinitely better.
January 7, 2007 at 5:04 pm
wrw
1. 1 to 200 looks concentrated, why the low absorbance? Of course it all depends on the concentration of the chromophores in the juice.
2. Sounds like a steam distillation might be useful here.
3. Then I’d do a LC-MS, or if I didn’t have one a GC-MS.
What does Cranberry Juice look like?
January 7, 2007 at 10:31 pm
gaussling
I’ve only done a few runs of this material. Honestly, I expected higher absorbance in the visible range, given the apparent high extinction observed in a glass on the breakfast table in the morning sunlight. But it might be a matter of scaling. The concentration was chosen so as to keep the most intense peak on scale (at less than A=3). Some detail in the visible band might pop up if I just scanned from 400 nm to 800 nm with a more concentrated sample.
The product is “Flash” Pasteurized- hard telling if the antioxidant molecules are degraded with aerobic heat treatment.
I’m a bit annoyed with Odwalla for labeling the product as Pomegranate juice, but diluting it with the other juices. Pomegranate juice is potent and a little astringent- their taste testing groups probably lead them to offer this composition for better consumer approval.
All you rich guys with your LC-MS.
Other juices and some fine Merlot will have to wait for the next weekend.
January 8, 2007 at 7:45 am
gaussling
Actually, one brand- Pom- has considerable sediment on standing. The juice should be filtered prior to dilution. Part of the notably high extinction of this juice could be due to turbidity. Didn’t think of that. It’d be interesting to see of the sediment has components that are soluble in CH2Cl2 or some other solvent.
June 15, 2007 at 8:13 pm
Tyler
There are only two known labs in Europe that are capable of such testing. US labs do not have the reference specs to give you good data.
Some comments from above:
You can label Pomegranate juice and still have white grape and water present. Once you make the claim that it is 100 percent Pomegranate you can only add Pomegranate, or Pomegranate Conc and distilled water.
Flash is just a marketing lingo for the bottle, all juices must be heat pasteurized 186 F or above, to comply with HACCP and Kosher standards. Testing past 165 days of shelf life did not show much difference in Antiox levels even after Pasteurization. That goes for steam Past as well.
Some sediment is just part of the Pomegranate which was used, and it also depends how long your bottle has been sitting.
Ty
September 15, 2007 at 11:06 pm
JM
Would you be interesting in seeing at least seven lab reports showing products labeled as 100% pomegranate juice but actually have little or no pomegranate juice and some with added sugar?
September 16, 2007 at 5:58 am
gaussling
That would be interesting.
October 3, 2007 at 12:08 am
Tyler
JM,
Again you can still legally claim 100% Pomegranate Juice with Pomegranante Puree concentrate with added white grape and water.
Ty
October 3, 2007 at 12:11 am
Tyler
Also Pomegranate which is reconstituted from Pomegranate Concentrate is predominately water, since the brix on the concentrate is 65.
Ty
October 3, 2007 at 5:42 am
gaussling
Hi Tyler- Thanks for the comments. Are you in the juice business?
October 7, 2007 at 7:43 pm
Tyler
Yes I am, currently employed by PepsiCO.
October 7, 2007 at 8:24 pm
gaussling
Wow. PepsiCo. How do you like it there? Doesn’t Pepsi give off a notorious greenhouse gas? \;-)
I would like to devise a simple test to measure the anti-oxidant capacity of this juice. I wrote another post on this topic as well.
https://gaussling.wordpress.com/2007/02/25/uv-vis-spectrum-of-pom-pomegranate-juice/
There is some complex method out in the literature. It must have been devised by biochemists.
October 13, 2007 at 12:42 pm
Tyler
The traveling is nice. We are working on that.
Ty
December 8, 2008 at 4:30 pm
Lila
I bought a box of “100% pomegranate juice” that had a very fine black sediment in it. Can anyone tell me what this could be? I drank some of the juice just after opening the box and before noticing the black sediment. After that, I felt nauseous for about a month.
December 8, 2008 at 5:22 pm
gaussling
Hi Lila,
It is really hard to say what it was. I do know that pomegranate juice does have fine sediment in it resulting from the pressing process. In this case it would be solids from the rind of the fruit that are darkly dyed by the juice.
It is hard to identify what the material was that you describe. Did you save any of the material from the package?
December 12, 2008 at 11:54 pm
Lila
Hi, gaussling,
Thank you very much for your answer. Sorry for not answering before, but in the last few days I had a bad case of cystitis. I never had this before and I am wondering if it could be from the juice as well. (Can’t stop worrying)
I filtered the juice through a cloth and also kept the box but so far have done nothing with it. I don’t know where I should take it to be tested. Thanks again!