Oxidation – definition and meaning

Oxidation occurs when a substance gains oxygen. It is the opposite of reduction, which means the loss of oxygen. Oxidation also refers to any chemical reaction in which electrons move, i.e., the oxidized substance gives away electrons.

For example, when iron reacts with oxygen we get rust. Rust is oxidized iron, or iron that has lost some electrons while the oxygen has gained some.

Magnesium is oxidized when it reacts with oxygen and subsequently forms magnesium oxide.

We call the process of reduction and oxidation redox.

Although oxygen does not necessarily have to be present, most people think it is.

Oxidation of fruit

If you cut open an apple, initially, its flesh looks fresh and appetizing. However, after an hour or so it does not. The flesh starts going brown.

The inside of the apple turns brown because of oxidation. By exposing the inside of the apple to air, which contains oxygen, it oxidizes.

In other words, substances in the inside of the apple react to the oxygen and make it turn brown. We call this browning oxidation.

Oxidation - image with explanation and example with fruit
Companies that sell fruit in cans add syrup not just to enhance the taste, but also to make it last longer. Syrup is an antioxidant. In other words, it slows down oxidation.

Antioxidants slow down oxidation

Antioxidants either slow down or stop oxidation. There is a simple experiment you can do to see the effect of an antioxidant. The information for this experiment comes from Science with Kids.

For this experiment, you need:

– One banana

– One apple

– Corn syrup

– Sugar

– Tags (labels)

– Two small plates

There are eight steps to this experiment

1: On each plate, place four tags. Label them lemon juice, syrup, sugar, and plain.

2: Cut eight apple and eight banana slices.

3: On one plate, place eight banana slices; two pieces next to each label. Do the same with the other plate, but with apple slices.

4: On the banana and apple slices, next to the label ‘sugar,’ sprinkle sugar.

5: On the apple and banana slices, next to the label ‘lemon juice,’ squirt lemon juice.

6: Place corn syrup on the slices next to the ‘corn syrup’ label. Do this on both the banana and apple plates.

7: Make sure that you have not added anything to the fruit slices next to the ‘plain‘ label.

8: Wait approximately two to four hours. Then observe the fruit slices on each plate.

You will notice that the ‘lemon juice‘ fruit slices are the freshest. The ‘corn syrup’ slices are less fresh than the ‘lemon juice’ ones but fresher than the ‘sugar’ ones. However, the ‘sugar’ slices are fresher than the ‘plain’ ones.

Lemon juice, corn syrup, and sugar are all antioxidants. Lemon juice is the most powerful antioxidant of all three.

Canned fruit companies sell their fruit either with corn syrup or without. The ones with corn syrup stay fresh longer. Consequently, canned fruits with corn syrup have a later expiry date.

Oxidation in the human body

Oxidation in our bodies damages cell membranes as well as other structures. For example, it damages lipids, cellular proteins, and DNA.

When our bodies metabolize oxygen, we create ‘free radicals.’ Free radicals steal electrons from other molecules and subsequently cause damage.

Our bodies can cope with some free radicals. However, when there are too many of them, we are more likely to suffer heart, liver, and other organ diseases. In fact, an overload of free radicals raises the risk of developing some cancers.

Smoking, alcohol consumption, sunlight, pollution, stress, and some other factors can accelerate oxidation in our bodies.

Some foods have antioxidants. If we consume them, they can neutralize free radicals. For example, vitamins A, C, and E, and the minerals zinc, selenium and copper are antioxidants.

Phytochemicals in plants and zoochemicals from animal products also have powerful antioxidants.

Put simply; antioxidants can slow down oxidation in our bodies. They can protect our health.

When we talk about ocean oxidation, we mean the increase of oxygen in the ocean. The increased oxidation of our oceans and atmospheric O2 set the stage for early animal evolution, scientists say.

Video – What is oxidation?

This video explains what oxidation is, and why oxygen is sometimes our friend, and sometimes not.