How we did it:
- 2-3 apples
- 5 bowls
- baking soda
- lemon juice
- white vinegar
Cut the apples into eight slices each. If needed, have an adult assist with this step!
Place 2-3 wedges in five separate bowls and cover the apples with each of the liquids: water, baking soda, lemon juice, milk, white vinegar. Tip: Place three spoonfuls of baking soda in water to make baking soda solution.
Make your predictions-- what do you think will happen to each of the apple mixtures? One of these solutions will prevent the apples from oxidizing (or turning brown!). Which solution do you think it is and why?
Let the apples sit, and check up on it the next day. Were your guesses correct?
What's going on?
When apples are cut, an enzyme (polyphenol oxidase), that reacts with oxygen, is released-- causing the apple to turn brown. Lemon juice is full of ascorbic acid, which will react with oxygen before the enzymes in the apple. Lemon juice also is very acidic, about 2.0 pH, and the enzyme in the apple oxidizes in environments between 5.0-7.0 pH. Can you find other acidic ingredients that could prevent apples from browning?