Analysis: how the chocolate industry relies on the right scientific recipe to keep customers happy

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By Olivia Schmidt, UCC; Naghmeh Kamali, UCC and Sheila Fitzgerald, RCSI

It is the season for chocolate. Across the nation, perfectly wrapped squares of chocolate line the shelves in shops just waiting to be devoured. Whether it is the purple packaging which engulfs the nation's favourite bar, Cadbury, or the perfectly made chocolates available from Butler’s chocolatiers, we all have our favourite. Chocoholics wear the term with pride and it’s no wonder as the Latin for cocoa tree, Theobroma cacao translates to "food of the gods".

Believe it or not, the art of making chocolate is now a science, one that chocolatiers experiment on all over the world. The journey starts with the humble cocoa bean which grows on trees in areas of high rainfall and humidity, predominantly in Central and South America, as well as parts of Africa.

The production of chocolate from these beans follows an intricate manufacturing process. Once harvested, the beans are fermented, whereby the yeast in the white pulp of the bean breaks down sugars and other key carbohydrates, leading to the development of the bean’s flavour precursors. After the fermentation process, the beans are dried to reduce the moisture content, further enhancing the flavour.

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Adding to the chocolate taste is the roasting of the beans which releases the cocoa nib. The nib is the main fat storage of the bean and contains cocoa butter, a core ingredient in chocolate. This is a vital step to understand as fat molecules in chocolate can orient themselves in different positions relative to each other, forming different crystal structures. The ability to form crystalline structures is referred to as polymorphism and is a crucial factor in many areas of chemistry. This is vital as chocolate can exist in six different polymorphs, each with different textures, tastes and melting points. Imagine if chocolate didn't melt in your mouth! Among all those polymorphic forms, Form V is most highly regarded with it’s glossy and luxurious finish, melt in the mouth sensation and satisfying snap.

However, chocolate may not stay in this perfect form forever. If you have ever left a chocolate bar near heat or in the sun, you may have noticed that it doesn't taste the same anymore. This is because a different polymorph has been formed due to a melting and reforming process. This new crystal structure has changed the internal chemistry and therefore, the taste of the chocolate.

Such changes in crystal structure or polymorphism can occur due to impurities, temperature and pressure. This is a big problem in warmer countries. To prevent changes to the crystal structure in warmer climates the chocolate recipe has been reconfigured to contain less crystallised fat so they are not as susceptible to melting. The fat is often replaced with sugar. This is one of the reasons why people complain that chocolate does not taste as good when they travel abroad. 

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Indeed chocoholics from different countries have varying tastes. Dark chocolate is very popular in other nations, but milk chocolate is more of a hit in Ireland, the UK and United States. For milk-based chocolate, there are a variety of different dairy ingredients that are used to produce the final product. Of particular note here is "chocolate crumb", a compound made from a blend of milk, sugar and cocoa liquor. The three ingredients are mixed and vacuum dried to form a powder that can be easily incorporated into manufacture.

The drying process of the chocolate crumb is a key determinant in the development of the desired flavour in the chocolate. Through a sequence of heating and drying steps, the resulting caramel and fruity flavours we all know and love start to develop. The aromas released during this process are recognised by our smell receptors to leave our mouths watering! 

Once the crumb has been successfully produced, it undergoes conching, where the flavour is further modified. A process developed by Rodolphe Lindt, conching evenly distributes the ingredients within chocolate throughout the mixture. Essentially, chocolatiers use conching as a way to ensure that all components in chocolate are covered in the cocoa butter, giving the final product a better taste.

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At this stage, manufacturers may add chocolate to the liquid crumb and remove water or acids, such as acetic acid, a key ingredient in vinegar. The final chocolate product is then formed through a melting and reforming process known as tempering. This involves the formation and alignment of crystalline structures of cocoa butter, forming thermodynamically stable polymorphic characteristics that provide a glossy appearance and an enhanced shelf-life. 

Now all that is left for chocolatiers and companies to do is package and sell the chocolate. This doesn't seem to be that difficult of a task as it seems the world is addicted to chocolate and chemistry may be able to give an insight why. There are three compounds present in chocolate which can give consumers an "eater's high". 1,3,7-trimethylxanthine, more commonly known as caffeine, is a widely used central nervous system drug which is present in low amounts in chocolate. Caffeine activates receptors in the brain which create pleasure producing chemicals.

But this isn’t the only type of drug present in chocolate. 9-Tetrahydrocannabinol is closely related to the active ingredient present in marijuana and has also been found in chocolate. Similarly to caffeine, the effects of this compound are initiated in the brain. Phenylethylamine can also be found. Known as the "love drug", the effects of this compound is similar to that of amphetamines. The presence of this compound has led many to believe that chocolate is an aphrodisiac, originating from the Aztec ruler Montezuma who believed that by drinking copious amounts of their cocoa drink (known as Xocoat) that he would obtain enough stamina for his sexual conquests.

There are three compounds present in chocolate which can give consumers an "eater's high"

However, because there are only trace amounts of the above mentioned drugs present in chocolate, their sale and consumption is not regulated like the sale of drugs, alcohol and other products that are classified as addictive. Yet it seems we are addicted, as many people can't get through the day without a chocolate fix. Indeed, it pays to get the formula right as chocolate is a multi-billion dollar industry, one that relies on getting the right scientific recipe to keep customers happy.

Olivia Schmidt is a PhD researcher with SSPC, the SFI Research Centre for Pharmaceuticals, at UCC. Dr Naghmeh Kamali is a Postdoctoral Researcher at UCC. Sheila Fitzgerald is a PhD researcher with SSPC at the RCSI.

The views expressed here are those of the author and do not represent or reflect the views of RTÉ