Red cabbage juice is the best known edible pH indicator, but there are many safe fruits, vegetables, and flowers that change color in response to acidity or alkalinity. The plant pigments responsible for the color change are anthocyanins. Most of these molecules change from red to purple to blue in response to pH. Yellow, orange, and red are also possible.
Pretty much every berry changes color. The deeply colored skins of vegetables are also good. In addition to the plants listed in the table, try acai, currant, chokecherry, eggplant, colored corn, raspberry, and blackberry. Edible flowers that change color include violets, roses, hibiscus, and butterfly pea.
How to Use Edible pH Indicators
There are a couple of ways to extract the colors from the plants in a way you can use or save for science projects, natural Easter egg dyes, or for color change food colorants.
- Dry the flower, fruit or vegetable and then use a spice grinder to make a powder.
- Finely grate the plant. Soak it in a minimum amount of boiling water to extract the color. Extract the colored water (basically a concentrated tea) by wrapping it in cheesecloth or a coffee filter and squeezing it out. You can refrigerate the liquid to use within a week or freeze it for use within a couple of months.