My daughter is a student at the Boston School of Herbal Studies. She came home from a weekend class excited about making violet flower tea. She collected a handful of violet flowers from our lawn and placed them in a jar. Then she poured boiling water over them and let it sit for 24 hours. The concoction turns a lovely shade of blue that can be sweetened with sugar.
I told my sister about it, and she said my daughter would need to explain the color change chemically. Oh, my sister is the chemistry teacher for my two homeschooled teens. So, research was done and a little presentation was made that impressed my sister too. Here is my daughter’s explanation:
There are pigment molecules called anthocyanins in the violet’s cell vacuoles that cause the violet tea to appear blue. Changing the structure of these molecules changes the color. We added lemon juice to turn it pink because lemon juice is very acidic (as well as yummy.) To understand how the acids change the structure, it’s helpful to know a bit about color and acids.
Color: Different colors of light have different amounts of energy. For example, violet light has twice as much energy as red light. Molecules of high energy absorb high energy light and molecules of low energy absorb low energy light. High energy molecules are molecules that have lots of room for the electrons to move around freely. In low energy molecules, the electrons are confined.
Acids, to put it very simply, give lots of free hydrogen to the solution. Adding the lemon juice added hydrogen to the anthocyanins. This changed the molecular structure to make it more confined, thus changing the type of light it absorbs. That is why the violet syrup turns pink.
While the violets are still around in Spring, pick some and make magic (chemistry) yourself!