The Chemistry of Chocolate? Eggcellent.*

Part I

With Easter coming up, and so many people giving up their sweet tooth for Lent, it seems like chocolate is on everyone’s mind. So what better topic for my first blog post for Science Brainwaves than the science of chocolate…

The first record of chocolate dates back to around 1500 BC, when the Aztecs and Mayans began drinking a cold, bitter mixture of cocoa and water. They named this cacaoatl, which literally translates to “foamy water”. Delicious. Three thousand years later, chocolate reached the European mainland, and from then on, there was no stopping it. By 1831, John Cadbury was selling drinking chocolate, and in 1876, Nestle released the first bar of milk chocolate onto the market.

Despite the huge variety of chocolate on offer in the shops, the basic recipe is very simple – cocoa butter, sugar, cocoa solids and milk solids. The difference in taste comes mainly down to different amounts of each ingredient, although dark chocolate has no milk solids (which is why it tastes less “creamy”) and white chocolate has no cocoa solids, which explains the pale colour.

The way cocoa beans are processed are the key to how the end result will taste. After being picked, they’re fermented for about a week, dried for a fortnight and then transported to a factory. Fermenting the beans adds around 30 new chemicals to the mix, some useful and some not, so at the factory, the beans undergo a process known as the Maillard reaction. It has at least 9 steps, and converts the amino acids in the cocoa beans (which don’t taste of anything) to aldehydes (which generally taste great).  Depending on how hot the reaction is, how acidic you make it and how long you run it for, you can get over 1000 different tastes from the Maillard reaction, including coffee, caramel and roasting meat.

Next, cocoa solids (made from grinding the beans) are conched. This means warming them up, grinding them with sugar and blowing air over the top. The heat removes any volatile (easily evaporated) chemicals from the beans, and the air whisks them away. The main thing removed from the beans is acetic acid, which is more commonly known as household vinegar.

Conching the cocoa solids decides what quality the chocolate is. The smaller they get, the better the chocolate – anything greater than 0.03mm (0.003cm, or three hundred thousandths of a metre) wide and the chocolate will feel gritty in your mouth. European chocolatiers, like the Belgians and Swiss, prefer very, very fine particles, which makes it melt more slowly in your mouth, and explains why European chocolate is more expensive.

A useful tip is to never store chocolate anywhere too warm or too cold. If you leave it in a warm room, you get a “fat bloom” – the white powder you sometimes find when you keep an Easter egg for too long, or forget about the Dairy Milk in your handbag. The increased heat means the fat rises to the top where you can see it. You can get rid of the bloom by gently warming it, then letting it cool down slowly, but it’s tricky to get it right without ending up with a puddle of chocolate. If you keep your chocolate in the fridge, you’ll get a “sugar bloom”. Any water vapour inside the fridge or the packet will collect on the surface of the chocolate as it cools down, dissolving any sugar it can reach. This eventually crystallizes on the top, giving you a gritty layer of sugar on your chocolate. There’s no way to undo this, so store your KitKat at room temperature for the best taste and texture.

* Well done if you made it past the pun! The alternative was “The Easter Bun(ny)sen.” In part II, I’ll be looking at why chocolate makes you feel good, and how it can help you stay awake. Title suggestions gratefully received!


2 thoughts to “The Chemistry of Chocolate? Eggcellent.*”

  1. Hi ,
    I will definitely try this at home, this article is really brushing up my chemical science as well as home science skills 🙂

Leave a Reply

Your email address will not be published. Required fields are marked *