Question

how would you make anthocyanin pH paper with a greater amount of pigment than just plain soaking and drying? how could you make it dark?

Answer 1

Red Cabbage has a pigment known as anthrocyanin. Anthrocyanin can change its color depending in the H+ ions concentration in water. Thus, it acts as a pH indicator. One method of making a pH indicator paper is to cut the cabbage, soak in boiling water, and filter the juice. Blotting paper is soaked in the juice, dried, and stored.

In order to increase the concentration of anthrocyanin in the pH paper, the cabbage can be cut and mixed in ethanol in a ratio of 1:3 (weight:volume) for 30 minutes. The solution is filtered through filter paper and poured in petriplates. The petriplates are placed in a laminar airflow to dry the pigment. The dried pigment is dissolved in 1:10 weight by volume ratio. Blotting paper is soaked in pigment solution, dried, and used. Methanol, water acidified with acetic acid and ethanol in hydrochloric acid medium can be used in place of ethanol. However, methanol and hydrochloric acid are more toxic than ethanol an organic acids.