The Chemistry of Chocolate

The “Blissful Joy” of chocolate is one enjoyed by mostly everyone. Ever since childhood people have been enraptured with its rich creamy taste and it has become a staple buy for people’s presents, children’s parties, cooking, dining and many more. This substance although it was first brought back by Christopher Columbus, has more recently formed a booming, multi billion pound industry with almost 660,900 tonnes of chocolate consumed in Britain each year.

Although seemingly simple, Chocolate making is a complex process containing a large amount of Chemistry. The main (and most expensive) ingredient of Chocolate is cocoa butter which is made up of triglycerides such as “1,3-distearoyl-2-oleoylglycerol”, more commonly known as “SOS”.

SOS forms 6 crystalline structures and it is crucial in chocolate making that only one of these structures (a structure known as “B(V)” )  is made. To get over this problem, producers use a method called “tempering” which effectively controls the temperature at which the crystal structure forms. Since each type of crystal is formed at a different temperature, this is a way of controlling and forming B(V). The cocoa butter is heated to a very high temperature in order to break down all 6 crystalline structures. Then the mixture is cooled to below 34 degrees (B (V)’S melting point) and kept at around 30 degrees to stop other crystals forming at lower temperatures. It is this particular Crystalline structure in chocolate that allows for its smoothness and texture, in fact you will notice that if you melt chocolate when cooking that the product you obtain when cooled will be different from the starting chocolate in taste as well as texture and this is because of the different crystalline structure that will have formed.

However, there is more than just heating to obtain the perfect structure needed for Chocolate. B(V) is not the most stable of structures and will often want to change to a lower energy state such as B(IV). This is obtained when other triglycerides that derive from palmitic acid (POP and POS) join in with the crystalline structure of SOS. These triglycerides are a lot shorter than SOS and are often built into the crystal so as to leave gaps. The Chocolate crystal will then readily change to the more stable crystal form “B(IV)” so as to reduce these gaps so producing a different structure and changing the chocolate. This is sometimes known as “fat bloom” and can be clearly seen when cheap chocolate is left for a long time. However it is also known that there are less electrostatic forces holding the B(V) crystals together then in B(IV) so showing that B(IV) is the more stable crystal that Cocoa butter will try to obtain.

Unlike with other food sources such as curries and peppery foods which contain specific molecules which give it its specific flavour, chocolate has no particular molecule to give it its addictive taste. Some may argue that it is the bitter taste of the alkaloid “theobromine” which gives the chocolate its characteristic bitter taste, however it is more likely that the taste and addictive nature of chocolate can be attributed to the amount of glucose present in each bar and the caffeine molecules which are also present.

Developing new and cheaper ways to obtain the perfect structure of cocoa crystals is still needed and the process requires novel ways of forming the B(V) with ease. Of course, with cocoa butter being so expensive it may be more profitable to use research to find a replacement substance or chemical for cocoa butter so as to maximise profits and decrease the amount of farm land needed for cocoa beans. 

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