Now that summer is over and school has started back up I wanted to talk about an experience I had over the summer that might be interesting to readers of this blog. I spent some time in Belgium – no prizes for guessing my favorite thing there (yes, it was chocolate!) but specifically, I got a fantastic opportunity to spend a whole afternoon in a chocolate-making workshop where we used incredible ingredients to make pralines and mendiants (a flat chocolate topped with dried fruit and nuts). That was an amazing experience but the science nerd in me had so many questions about how that stuff actually worked, so I did some research and I want to share a couple of cool things with you.
Tempering
The first thing we did in the workshop was take some chocolate and “temper” it; this was done using a special heating device that would act similar to a double boiler. We slowly heated up the chocolate, stirring, until it reached ~115F and then turned off the heat stirring constantly until it reached ~85F. Then it was done. This fascinated me because I didn’t understand what was happening to cause the tempering to make chocolate snap like how it did. Essentially how tempering chocolate works is that the cocoa butter molecules in chocolate can take 6 different configurations (I’ll call them Form 1, Form 2, etc.) The first 4 forms are the ones that must be limited as they result in either gooey, matte, or crumbly finishes in chocolate, while creating as many “Form 5” formations as possible, as these create the snappy, shiny tempered chocolate we want. Having too many “Form 6” formations can also be bad, as they can result in an overly viscous chocolate. The specific temperatures and cooling of chocolate during tempering is what helps maximize “Form 5” and have less “Form 1-4”
Ganache and Emulsions
After we had tempered the chocolate, we needed to make a ganache to fill the chocolate truffles with. As we were going through the demonstration, an interesting effect took place, as the cream was added to the melted chocolate, it at first was lighter as the cream was being mixed in, but once the cream was fully mixed, the ganache was darker than the melted chocolate. This was a real puzzle! How can adding white cream to a dark substance make it darker instead of lighter?? It turns out that a ganache is an oil-in-water emulsion, with cocoa butter droplets and milk fat suspended in the water in the cream.
Figure 1a (Schramm, 2005; Tamilvanan et al. 2010).
Fat and water refract light much more similarly than the fat and sugar in chocolate, meaning the ganache scatters light less and absorbs more light causing the brown cocoa to show more and the mixture to look darker. Along with this, while melted chocolate has the cocoa coated in mainly fat, the ganache contains a higher percentage of water, which scatters light slightly less than fat leading to a darker finish as well.
