pH Indicator from Black Nightshade Berries

In my biology class this semester at school, I am required to make a pH indicator at home from purple cabbage. If the students are unable to obtain purple cabbage, the professor gave instructions on how to make a similar pH indicator from blueberries. Since the deep purple pigment anthocyanin appears to be the active ingredient in this type of indicator, it might be possible to modify the process of making the blueberry pH indicator for use with black nightshade berries. North American black nightshade (Solanum phychanthum) grows abundantly where I live in Ohio on disturbed soil and fallow agricultural land. The purple-black berries are rich in anthocyanins and edible when fully ripe. Wait for the berries to fall to the ground or come lose from the stem with a gentle tug and for the berries to be fully black-purple before harvesting them for food or for a pH indicator. Until I can get definite permission from my professor to share the procedure for making the blueberry pH indicator, I will share a YouTube video that covers essentially the same procedure:
https://www.youtube.com/watch?v=kji-FpVHUuk

Because of the importance of pH balance in several applications, this indicator might be a more accurate method of gauging pH for soap making, nixtamalizing corn, water pH testing, and pickling. There might be other applications I have not thought about yet. Once the black nightshade berries ripen later this Summer, I will attempt to test the procedure in the YouTube video to see if it also works with black nightshade berries in the process of making a batch of hominy.

In other parts of North America, other related species of black nightshade also grow. They all used to be classified as Solanum nigrum, but were separated into separate species by later taxonomists. Below are some images of Solanum ptychanthum from Wikimedia Commons and a distribution map of the species from BONAP.

Purple sprouting broccoli works as do globe artichokes as well.