MGSU The pH touchy Nature of Anthocyanin Pigments Essay

ACID & BASE LAB
Acids turn blue litmus red, and Bases turn red litmus blue and Neutrals does not show any change on the
litmus paper.
Background information
In a plant anthocyanin serve as key antioxidants and contribute to the color of
flowers. Anthocyanins are pH dependent. When the acidity changes, the color
changes. Anthocyanin pigments can be found in red/purplish fruits and vegetables,
including purple cabbage, blackberries, blueberries, cherries, raspberries and
purple grapes.
The amount of anthocyanin can affect the color change.
.
Many flowers, fruits and vegetables contain chemical substances that change color in solutions
of different pH such as hibiscus, turmeric, and red cabbage.
Steps
1. Rub fresh red or purple rose petals over two A4 pieces of plain paper – like coloring with a
crayon.
2. Cut one of the white papers completed rose sheets into small test strips.
3. Cut the other rose sheets into two – paint one all over with a solution of bicarbonate of soda
and allow to dry.
4. Then cut into small test strips.
5. Paint the remaining sheet with lemon juice and allow to dry.
6. Cut into small test strips.
7. Using a cotton bud and test strip, dot on samples of acidic and alkaline solutions.
8. Record the results.
9. Try the same test with other plants and see which make good pH indicators.