By name and by nature, chocolate is worshipped the world over. But what is it, how is it made and why do we love it so much? Here's the chemistry to explain the obsession.

So, what IS chocolate?

The main ingredients of chocolate come from the cacao plant, Theobroma cacao. Theombroma translates to 'food of the gods'.

The plants grow in tropical regions and sprouts an odd-looking fruit or 'pod' about the size of a small football. Inside the pod there are cacao beans, which, after some farming and processing, become the key ingredient inside the foil at Easter, or whenever the urge grabs us.

Mr Mick Moylan, from the University of Melbourne, says chemistry features throughout the chocolate production process, starting at the farm.

"After the pods are cracked open, wild yeast and bacteria ferment the cacao pulp surrounding the beans," says Mr Moylan, the Chemistry Outreach Fellow in the School of Chemistry.

"The reactions are similar to those in brewing and yoghurt making. Ethanol, acetic acid (found in vinegar) and lactic acid (in yoghurt and sore muscles) are produced and seep into the beans, developing the chocolate flavours."

Processing at the factory starts with roasting and Mr Moylan says the main chemical change in this step is called the Maillard reaction.

"This reaction occurs between amino acids and sugars. The reaction produces molecules that are often brown-coloured, with strong, pleasant aromas. One of these molecules is known as 2-acetlypyrroline, and is part of the delicious smell of freshly made toast, roasted coffee beans and steaks.

Your nose can detect a billionth of a gram of this aromatic molecule.

What's the deal with raw cacao?

The latest superfood fad is unpressed raw cocoa. Apart from a vowel switcheroo, the difference between cacao and cocoa comes down to heat and pressure.

"Cacao becomes cocoa powder after it's been roasted and pressed to have the cocoa butter extracted," says Mr Moylan.

White chocolate isn't really chocolate, right?

That depends.

If you are eating good quality white chocolate, it will contain cocoa butter, which comes from the fatty lining of the cacao bean. But most of the stuff we call 'white chocolate' has no cocoa butter in it, so it's not really chocolate.

"After roasting, the cocoa beans are ground, shelled and pulverised. It can then be separated into cocoa butter and the cocoa powder, or ground further into chocolate," says Mr Moylan, who presents the chocolate workshop From Bean to Bar at Melbourne's Victoria Market each year during National Science Week.

"The grinding process breaks down the solid protein, fibre and starch particles so that their grittiness is too small for the tongue to detect – around 0.02mm."

Why does old chocolate get that yucky white coating?

It's the cocoa butter separating from the rest of the chocolate mixture.

Chocolate is made up of fatty substances (either cocoa butter or milk fat) and non-fatty substances (cocoa powder and sugar). Like oil and water, they naturally don't mesh well together. During the production process, lecithin, a binding agent, is added which helps to fix this problem. The other key step is tempering.

"Tempering arranges the fat molecules in a way that creates chocolate that is delicious, hard and glossy," says Mr Moylan.

"For example, dark chocolate is held at 29-30 degrees celsius for around five minutes, then heated to 31-32 degrees, then cooled and set."

Unfortunately, when chocolate melts and hardens again, the specially arranged fat molecule structure breaks down. The fat rises to the surface of the chocolate, like oil above water, and creates a white 'bloom'.

Why does cheap chocolate taste so awful?

A number of reasons. How it is made and what it is made of both lead to that overwhelming sense of 'cheap'.

"Ingredients from the cacao plant are expensive, so substitutes are often used, like milk fat in place of cocoa butter, which melts at a higher temperature and so doesn't taste as nice," says Mr Moylan.

"If the ingredients aren't ground for as long, they taste bitter and grainer, and not nearly as smooth. Tempering is also a factor. If the fat molecules aren't arranged in the right way, the chocolate doesn't melt in the same way, so it doesn't taste as nice."

Is chocolate really that bad for dogs?

Yes.

Mr Moylan says that chocolate contains the stimulant theobromine, which acts in the same way as nicotine, morphine, caffeine and quinine. It gives us that chocolate 'buzz', but sometimes causes dogs to have a heart attack.

So definitely no chocolate for Rover. Ever.

Chocolate is also one of the richest sources of antioxidants, which are important to our health as they stop or repair the damage caused by free radicals. Chocolate also contains a lot of caffeine.

One hundred grams of dark chocolate has about the same amount of caffeine as a cup of coffee.

So, at the weekend at least, you might get away with skipping the café line and getting your morning fix of caffeine from half a block of good quality, well-tempered chocolate.

After all, it's good enough for the gods.

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