Cabbage Chemistry

Royal Institution At Home Science

As the nights draw in, red cabbage with sausages makes for a comforting supper. Whilst it’s cooking, learn about acids and bases by making a pH Indicator just like this one from the Royal Institution.


Red cabbageRed cabbage
Onion (red or white)Jug of hot water
Salt and pepperThree glasses or clear plastic cups
SugarBicarbonate of soda


  1. Pre-heat the oven to 190 degrees C (or 170 fan), put the sausages in an oven tray with a little oil and cook for 20 – 25 minutes or according to the pack instructions.
  2. Cook the cabbage
    • Shred about half a cabbage and chop one onion
    • Put in a microwavable dish with some salt and pepper
    • Add 2 tablespoons each of sugar, vinegar and water
    • Cover and microwave for 5 mins
    • Check, stir, re-cover and cook for a further 5 mins
  3. Cabbage chemistry
    • Chop up around a quarter of cabbage
    • Add to a jug of hot water, stir and wait a few minutes
    • Pour some of the purple liquid into each glass
    • To one glass, add some vinegar – see the colour change
    • To another glass, add some bicarbonate of soda
    • Compare these colours to the original
  4. Serve supper
    • Check the sausages are piping hot in the middle
    • Serve with the cabbage and some instant gravy (I use gravy granules mixed with hot water from the kettle)


What’s going on? The science in a sentence…
A chemical in the cabbage, called anthocyanin, changes colour depending on whether it’s mixed with an acid (like vinegar) or a base (like bicarbonate of soda).

Other ideas for supper…
If you fancy something even easier, this cabbage recipe goes well with leftover turkey, shop-bought breaded chicken or oven-baked chicken drumsticks. If you don’t eat meat then try it with some grilled halloumi cheese or vegetarian/vegan sausages. If you want to go gourmet then add some apple and spices and slow-cook the cabbage as in this recipe from BBC Good Food.

And finally….
If you want to experiment further, try using your cabbage indicator to test other things to find out if they are acid or base. You can try lemon juice, egg, washing-up liquid, cola, orange juice, coffee, toothpaste, soap and apple juice and make a rainbow like this school science club did. You can freeze your indicator liquid into ice cubes as shown here by The Science Kiddo. You can also see if you can make the cabbage indicator go back to it’s original colour (neutral pH).

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