|MadSci Network: Agricultural Sciences|
Food pigments using have one color for acid and another (or colorless) for base. You can usually only get one color change (either to acid or to base), depending on the initial pH of the indicator. If you would like to make a food pigment indicator for base, you should use a food which is colored when acidic, and look for the color change. A variety of foods would suit the purpose, including strips of paper dipped in beet juice, blueberry juice, apple peel juice, etc. The pigment involved is anthrocyanidin, which has different colors for acid and base pHs.
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