Apple Oxidation Experiment of Science
Apples Not Red Anymore!
It is a common-day occurrence and something that even preschoolers can observe – cut an apple, and it starts to turn brown within minutes. This process is called oxidation of the apple. The phenomenon does not take hours – though different types of apples take anywhere between a few minutes to a few hours to turn brown. Today, we will carry out an easy-to-do apple oxidation experiment of science to keep apples safe from turning brown!
We will observe what happens when the apple pieces are submerged in different kinds of liquids and which one is effective and how. If you wish to know more about such simple science experiments that help your kids understand the different natural, chemical and everyday physical reactions, this could be a great start!
Why Does it Turn Brown?
When we cut an apple set in a biochemical reaction, which is also called enzymatic browning, it happens because the oxygen in the air reacts with a natural enzyme present in the apple’s flesh called PPO or Polyphenol Oxidase. This reaction causes a chemical reaction to convert the amino acids present in the apple to melanins. The melanin is brown in colour.
We will now conduct the apple oxidation experiment. If you wish to know more interesting facts and help your kids understand through simple experiments, follow the instructions properly.
Performing the Apple Oxidation Experiment
Materials required to conduct the apple browning experiment
- Zip lock bags
- An apple
- A knife
- Citric acid solution
- Black marker
Step 1: Take five ziplock bags and use the marker to mark each of them with the words ‘No liquid,’ ‘Water,’ ‘Milk,’ ‘Lemon juice,’ and ‘Citric acid.’
Step 2: Take each of the bags and pour the liquid that has been labelled on the top. So, fill water in the zip-lock that is marked as ‘water,’ milk in the pouch labelled as ‘Milk,’ lemon juice in the pouch marked as ‘lemon,’ and citric acid solution zip-lock marked as ‘Citric acid.’ The one that has been labelled ‘no liquid’ contains nothing.
The presence of this bag in the apple experiment scientific method is essential because it helps kids compare the reaction taking place in the bag with only air with that of the other bags. Fill all the bags with the respective liquid to more than half of the zip-lock.
Step 3: Time to cut the apple into ten equal pieces now. Place two apple pieces in each ziplock bag and seal the bags.
Step 4: Let the apples now soak in the liquids for a few minutes. If there is any extra liquid, then you need to drain out the excess liquid. Reseal the pouches.
Keep the apples in this form for a few hours now and regularly check the cut apples’ status after every half-an-hour.
Observations of the Apple Oxidation Experiment
Observation 1: The apple slices in the ziplock marked ‘no liquid’ start to turn brown almost immediately, and after a few hours, you will find the upper surface having a dark brown coating. The oxygen present inside the pouch has completely oxidised these slices.
Observation 2: The slices in the water turn brown too – it was slower than the oxidation in the first pouch marked ‘no liquid.’
Observation 3: The slices dipped in milk are no different. These two also start to brown and follow the same pattern as water. After a few minutes, you can see the oxidation reaction happening.
Observation 4: In this zip-lock, something different is happening. You will find that, for the most part, the slices have not turned brown. They may not look very fresh, but the browning or the oxidation process has not happened.
Observation 5: This pouch has the best results. The slices of apple retain their original colour and have not undergone any percentage of oxidation.
What do the Results of the Apple Oxidation Experiment Mean?
Water and milk could not delay or even influence the oxidation process of the apple slices dramatically. Both these compounds do not have any acidity that can prevent the oxygen from reacting with the PPO. However, compared to the first pouch – ‘No liquid’ – the reactions were much slower. It means that you can soak the apple slices in water or milk to keep it from oxidation for a few minutes – ten to fifteen minutes.
Lemon is acidic, and hence it could delay the process of oxidation in apples. The acidic constituent of the lemon reacts with the oxygen and keeps it away from the apple flesh. Therefore, the citric acid solution is more acidic and effective in preventing the apple slices’ oxidation.
However, it is essential to mention in this apple oxidation experiment that lemon and citrus acid will influence the taste of the apple, and after some time, the pieces become inedible. One effective way to prevent apples’ oxidation is to soak the cut pieces in a saltwater solution for ten minutes.