Color-Changing Cabbage Experiment

Did you know that you can change the color of red cabbage without using any dyes? Red cabbage gets its great purple color from anthocyanins. Anthocyanins, like most plant pigments, change color based on the pH of their environment. So when red cabbage is put into an acidic or basic solution it looses its characteristic “red” color.

This experiment is really easy. All you need is a red cabbage, baking soda, vinegar and about 30 mintues.

 

Materials

• 1 cup of diced red cabbage
• 2 cups water
• 1 tsp vinegar
• 1 tsp baking soda
• pot and lid
• several bowls

 

Method

1. Put water on the stove to boil.

2.  Dice  enough red cabbage to fill approximately 1 cup.

3. Once the water is boiling, put in the red cabbage and simmer for 15 minutes.

4.  Strain the cabbage to collect the colored water.

5.  Pour the cabbage water into three different containers. In one container add the vinegar and stir. In another container add the baking soda and stir.

 

Expected Results

The originial cabbage water should be a purple-blue color. The acidic solution that has vinegar in it should look pink or red. The basic solution that has baking soda in it should be blue, turquoise or green.

 

Experiment Variations

Change the actual cabbage color by boiling the cabbage in the acidic or basic solutions. Acidic solution: 100mL water and 20mL vinegar. Basic solution: 120 mL water and 1/4 tsp baking soda. There is a lot less water (only about 1/2 cup) so make sure the cabbage doesn’t scorch.

 

Play around with the amount of vinegar or baking soda. The anthocyanins in red cabbage are very sensitive to pH changes. Because of this, red cabbage juice can be used as a pH indicator. You can tell the approximate pH of something by what color it turns cabbage juice.     CAUTION: do not mix the vinegar with the baking soda unless you want a mini volcano (another fun science experiment).

 

Other vegetables to experiment with: beets, carrots, spinach, and rice. Note: the pigments in carrots and rice don’t go into water well so do the first experiment variation method for those.

Food	Pigment	Acidic Color	Neutral Color	Basic Color
Red Cabbage	anthocyanins	pink	purple	turquoise
Carrots	carotenoids	light orange	orange	dark orange
Spinach	chlorophyll	olive green	green	kelly green
Beets	betalains	magenta	red	brown
Rice	anthoxanthins	white	white	yellow

 

Wrap Up

I had a lot of fun doing this experiment and some of the variations. I hope you do too. Let me know how it goes!

 

Images: Nathalie Dulex  and Supermartl