Chocolate Alchemy

The chocolate tower on GBBO © BBC

The chocolate tower on GBBO © BBC

Last night on the The Great British Bake Off contestants were asked to produce intricate, show-stopping structures made of chocolate (yummy!) For many of the bakers, this meant tempering chocolate; a tricky process that involves heating to a specific temperature, then cooling, with the aim of getting a glossy finish. Watching the bake off made me think – how much chocolate cake could I eat before I became very seriously ill?* But then, once this thought past (and probably more relevant for this blog) I began to wonder exactly what goes on at a molecular level when chocolate is manipulated in this way.

With a bit of searching I came across an enlightening article by Chocolate Alchemy about the science of tempered chocolate, complete with every scientists best friend – diagrams

In order to temper chocolate, it must first be melted down. As a result of the melting process, all structure in the chocolate disappears. The AlChemist – love the name – describes the cocoa butter molecules as “a long stick”. There are many ways of arranging these stick-like chocolate molecules. However, unlike the animals on the farm, not all structures are created equal; some are stronger and more stable than others.

There are six structures, or “polymorphs” of chocolate, named (imaginatively) as forms I- VI.

It is the elusive form V that is the goal of anyone trying to temper chocolate.

After melting, the chocolate is left to cool and the crystals reform. Unfortunately, as life isn’t simple, it wont just be the desired no. 5 that is formed, but a mixture of forms I-V.

By heating and cooling the chocolate in a controlled way, it is possible to eliminate all of form I, form II, form III and form IV, leaving only perfectly tempered form V.

Sounds easy, right?

I’m sure that if I, the girl famous among lab technicians for breaking glassware, who regularly loses 99% of her product when recrystallising, were to try to temper chocolate, it would just end up as a disappointing, congealed mess at the bottom of the bowl.

I think I’ll leave it up to the professionals. Meanwhile, I will be sat at home, mouth watering, watching the insane creations take form, definitely not the least bit jealous.


*If you feel sick after eating chocolate, you need not fear! One of my professors (warwick 4lyf) has made chocolate with half the amount of fat. Read about it here

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