[ldanielrosa]

There's great coolness factor in making my own acid/base indicator from red cabbage, but it doesn't store very well.  Does anyone have a lead on how to remove the digestible portions so that it won't rot?  This isn't such a problem with curcumin from turmeric (which I discovered by accident while searching), as it is extracted with alcohol.  Is alcohol the way to go with cabbage too?

[pantone159]

Is alcohol the way to go with cabbage too?

I like to prepare the indicator with alcohol, my current recipe is to put 50 g of red cabbage + 50 g of 95% EtOH in a blender, blend, then filter the result.  Perhaps this keeps better than if made from H2O, it might last a couple of months, but still goes bad pretty soon.

This link on Sciencemadness
http://www.sciencemadness.org/talk/viewthread.php?tid=2464
talks about some attempts to isolate the indicator from the other junk.  Apparently, the indicator part of the molecule is bound to various sugars.  One suggestion is to try and break this bond by refluxing with acid.  I have not tried this, however.

It sure would be nice to make a stable indicator, the stuff is otherwise totally cool.

[pantone159]

You also get a cleared extract, that produces more vivid colors, when you extract cabbage with EtOH, rather than water.
The vegetable contains some junk that dissolves well in H2O but not EtOH, and you minimize this with an alcoholic extraction.