Science is not always pretty, but it never loses its fun factor! With this in mind, I bring to you; The Shrunken Apple Heads Experiment! Sounds gory, right? Well it is! But while this might creep some out, it is actually an awesome way to teach students about food preservation, bacteria and enzymes – and there’s nothing icky about that!

This is quite a versatile experiment and can be adapted to accompany many theory lessons. I will however focus it at an angle where one can learn about food preservation and why sources like salt and lemon juice can help prevent food from rotting. Whatever reason you choose to do this activity for, it's super cool for kids to do and is very likely to stimulate an interest in science.

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The Rotten Apple Heads Experiment

What you will need:

• Whole apples
• A cup of lemon juice
• Two tablespoons of salt
• A suitable carving knife (for adult use)
• Measuring cups and spoons

Instructions:

1. Start by carving faces into your apples.
2. You can leave the apple core in, or you could remove it. If you plan on eating your shrunken heads (pretty creepy right), then I would recommend removing the core.
3. Add your lemon juice and salt to a jug and gentle mix.
4. Soak your apples in the lemon and salt solution for over a minute, making sure the whole surface is covered.
5. This next step is determined by the amount of time you have on your hands. If you would like to get the experiment done quickly, then you can place them on a baking tray in a warm (not hot oven), until they start shrinking and drying out. If you would like the students/kids to witness the dehydration process and shrivelling as it occurs, then you can set the apples in a warm and dry place for a few weeks.
6. The end result will be a spongy and shrivelled apple. 

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The Lesson

Drying fruit and vegetables to keep them preserved and edible is an ancient practice. In this experiment we used salt and lemon juice as the substance which help preserve the food, but there are many other ways of preserving food stuffs, some healthy, some not so healthy! 

So how does lemon juice and salt help prevent fruits and vegetables from rotting?

When a vegetable or fruit (take an apple for instance) is sliced open, you cut into the cells and as a result, enzymes are released.

Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products. Wikipedia 

When these enzymes are released they react with the oxygen in the air and as a result, the apples and potatoes etc. start to turn brown. This is when bacteria starts to settle on the produce and decomposition starts to occur. 

Lemon juice is acidic and by adding it to the apple, you lower the pH of the apple. The acidity prevents the enzymes from reacting, and helps prevent bacteria from settling in.

Salt helps preserve food because it lessens the water available in the food for microbes to grow in. The combination of the two ingredients used in the experiment help to prevent the apples and potatoes from rotting and from remaining too wet. 

So that's one way you can learn about preserving food, although, the end result doesn't look too appetizing! Non-the-less, the kids will enjoy this activity from start to finish and will end up with a cool shrunken head which they can spook their friends and family with.

Much love - @sweetpea

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