The Chemistry of Chocolate

CHEMISTRY AND CHOCOLATE! THE 2 BEST THINGS IN THE WORLD!

Sorry physics. And Johnny Marr. And The Cure. Sorry…

IT CAN'T BE THAT COMPLICATED CAN IT?

You’d be surprised! Chocolate is an incredibly versatile thing!

BUT ALL CHOCOLATE IS LITERALLY THE SAME...

Sure, they are ‘all the same’ to you because chocolate is mainly sold in bars and that’s what people mainly eat, and those chocolate bars are mainly made from the same type of chocolate. The aim of chocolate bars is to be a solid at room temperature, but to melt in your mouth. Making this type of chocolate involves some cool chemistry.

CHEMISTRY? BUT CHOCOLATE IS A FOOD...

So what? Literally everything is chemistry anyway. Moving on though, everything starts with the cocoa bean in the cocoa pod on the cocoa tree. If you were to try a cocoa bean (not suggested) you would find that it tastes nothing like chocolate at all.

This is because there are a number of chemical changes that need to occur within the beans to get the flavours going. This starts with picking all the pods and then literally throwing them on the ground in a pile to rot and ferment for two weeks.

CHOCOLATE IS ... FERMENTED?!?!

Yep, you bet. During the fermentation stage, the pile of pods begins to heat up, which ‘kills’ the seeds so they don’t germinate into cocoa plants :(.

More importantly though, it chemically changes the chemicals in the cocoa beans to give rise to our beloved chocolate flavours. These chemicals are fruity tasting esters that are created from alcohols and acids that are created by enzymes acting inside the cocoa beans. These reactions are dependant on a huge number of factors from the weather to the air temperature and even the general weather and height of the piles.

These are of course closely guarded secrets (shh). This is why decent chocolate costs a bunch, because to make a decent chocolate, you need a great cocoa farm with a nice temperature and all sorts of different factors need to be controlled to get the best flavour.

SO CHOCOLATE IS JUST A FERMENTED COCOA BEAN BRICK? EWW

Umm no if it was like that then no one would eat it.

After the pods have been fermented, the pods are whacked (ouch) with a hammer and the beans are removed. They’re then dried and roasted, just like coffee. Again, the roasting sets of more chemical reactions (I told you everything is chemistry) that give rise to the nutty, earthy and almost meaty flavours of chocolate.

This happens because the carbohydrates within the beans begin to decompose (fall apart) because of the intense heat. This is basically the same thing as what happens when you put sugar in a pan, it caramelises (yum). In the case of the cocoa bean though, this reaction happens inside the bean, turning it brown like what happens when you roast coffee beans. This reaction creates nutty, caramel flavours.

SO WHERE DOES THE MEATY FLAVOUR COME FROM? I SWEAR CHOCOLATE DOESN'T TASTE MEATY

The meaty flavour happens because of yet another reaction, this time at a higher temperature. This temperature is called the Maillard reaction, which occurs when a sugar reacts with a protein. Cocoa beans actually contain a large amount of protein because they’re seeds, they’ve got to provide all the proteins for the baby cocoa plant (that has now been roasted 🙁 ) up and running.

When the beans are roasted in temperatures above 160 degrees C, the proteins and sugars react with the esters and acids produced earlier in the fermentation process, to form a whole load of nutty and meaty flavour molecules (yum!).

SO CHOCOLATE IS JUST A FERMENTED ROASTED BEAN BRICK? HMM...

Nah. If you grind up these beans, and add it to hot water you have the first drinking chocolate ever made. A Dutch company (yay) then thought hey, lets press this powder to make it finer for drinking. When they did this, a whole bunch of cocoa butter came out which is an ingredient you might recognise from the ingredients of your average chocolate bar.

From this pressing, thy also got a nice find cocoa powder which was much nicer than before. Then they thought hey, what if we mixed the cocoa butter and cocoa powder back together, add a heap of sugar and make it into a bar?

YOU LIED, THERE ISN'T THAT MUCH CHEMISTRY IN CHOCOLATE 🙁

Nope I didn’t lie you just didn’t read till the end (tsk tsk).

Even though the chocolate bar had been invented, it hadn’t been perfected yet, even with 30% sugar content it was still too bitter, and was missing a key ingredient, milk.

This key ingredient is the reason why chocolate tastes different in different countries around the world. The Americans remove some of the fat from their milk with enzymes, so their chocolate tastes cheesy and almost rancid. The British do it differently, adding sugar to milk and creating a sugary milk concentrate that is then added to chocolate. Other European countries add milk powder, giving their chocolate a fresh dairy taste with a more powder texture (and all because of milk!).

OK SO WHERE'S THE CHEMISTRY??? >:(

Ok ok ok!!!! The cool chemistry comes in when you look at the crystal structure of chocolate.

Chocolate is full of cocoa butter, one of the finest of all vegetable fats. It also happens to contain natural antioxidants which makes the cosmetic people happy, but also means that cocoa butter has quite a long shelf life.

This cocoa butter has a lot to do with the texture and melting point of the chocolate. The main components of cocoa butter are triglycerides, and they readily form crystals which are what give chocolate its mechanical strength.

As in other compounds, the molecules of triglyceride have a bunch of different options on how to arrange themselves into crystals. Type I and II crystals are soft and mechanically soft and unstable and if given the chance, will transform into denser type III and IV crystals. Type I and II crystals are mainly used to make chocolate sauces because of their low melting point. Type III and IV crystals are soft and crumbly. If you’ve ever left a chocolate bar in your bag and eaten it later, you’ll find it’s probably soft and crumbly :(.

Chocolate makers want to avoid these type III and IV crystals because they don’t snap, and will melt in your hand (not ideal). Unfortunately for them, they’re the easiest crystals to make. Type V is the ideal crystal that you’ll find in any well treated chocolate bar. It’s the densest type of crystal that has a melting point of 34 degrees C which is ideal.

IF TYPE V CRYSTALS ARE THE HARDEST TO MAKE, HOW TO CHOCOLATIERS MAKE THEM?

Black magic. Nah just kidding.

The crystals are made in a process called tempering, where the molten (or melted??) chocolate is poured into a mold with a ‘seed’ of type V crystals. The chocolate solidifies onto this seed, and rapidly forms type V crystals before type III and IV even get a chance to get going.

THAT'S IT FOR NOW!

Hopefully you enjoyed this post! I’m planning to write a second post on the psychoactive components of chocolate, another interesting bit of chemistry. Don’t go eating chocolate bars hoping to get a high from them, you’d have to eat 12 chocolate bars to get the same effects as just drinking a cup of coffee. You’d probably die from diabetes before you got high. Anyway.