Re: HYB: kitchen chemistry/pigment extraction

Different alcohols will disolve different pigments. There are some pigments that don't disolve in alcohol such as lycopene, which is oil soluble. I'm not aware of any water based pigments that don't disolve in alcohol , but that doesn't mean there isn't any, just that I've never heard of them.
Any water based pigment that doesn't disolve in alcohol won't be in the alcohol, any oil based pigment that doesn't disolve in alcohol won't be there. Anything that disolves in alcohol is either polar (water based) or non-polar (oil based). There is no third category of solvents. There isn't anything that is disolveable in alcohol that is neither water based nor oil based. Alcohol molecules are structured so one end is polar and the other end is non-polar, thus they can disolve both oil and water based chemicals, but not all oil based (non-polar) chemicals eg: lycopene.

In addition isopropyl alcohol, as rubbing alcohol, is usually 70% alcohol, the other 30% being water. Thus it would disolve any water based pigments. It is one of the weaker alcohol solvents.

Some anthocyanins undergo a chemical transition in alcohol, more so in Methanol. This chemical change can be stopped by acidifying the alcohol, and if not too far advanced, reversed by adding alcohol. A chemical reaction, not just a ph change.

Thus alcohol is a one step extraction, with oil being added to the solution after extraction, you can seperate out oil and water based pigments. Otherwise you can extract first with water , then with oil. Alcohol extracts the pigments better then either. The best solvent for biology is benzene. Toulene and acetone are also good. Alcohol is safest to use in a kitchen lab. Some sacrafice of efficency for safety and cost.

Chuck Chapman

Date: Mon, 16 May 2005 21:24:12 -0400
From: Linda Mann <lmann@volfirst.net>
Subject: [iris] Re: HYB: kitchen chemistry/pigment extraction

Mystery solved.

I had never seen such a lovely turquoise blue color in the extractant
before, & suspected it was a contaminant affecting pH.

No pH meter here, but a drop of white vinegar turned these lovely
turquoise colored extractions the same ol boring shade of reddish purple
all the others have been.

Not entirely sure why this most recent batch of extractions is higher
p

H.  Limestone spring water from the tap could change, but not the
bottled isopropyl alcohol.  Maybe water remaining in the tissue from all
the water rinses was enough to tip pH of the alcohol.

Anyway, great fun to have little mysteries of chemistry mixed in with
the wonders of bloom season.

Re: solvents and varying chemistry of pigments:  From what I read last
winter, depending on the pigments, it isn't all one bucket or the other
(water vs oil), there were some differences related to something or
other that made certain types of alcohols dissolve some water soluble
pigments and not others.  Ditto for some types of oils and some types of
oil soluble pigments.

I think..

- --
Linda Mann east Tennessee USA zone 7/8

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