Sunday, May 18, 2014

Chocolate Chemistry: Emulsifiers

Since cacao beans have fats in them called "cocoa butter," when you try to mix them with a liquid, the fats and the waters want to separate. To get them to combine smoothly, you need an emulsifier such as lecithin. Lecithin is a natural substance found in egg yolks, and it's the same thing that emulsifies mayonnaise. We spent a day learning about emulsions; here are some resources:

Emulsion experiment---pictured above. You mix oil and vinegar in one bowl (on the right), oil and vinegar with an egg yolk in the other (on the left). You can see how the egg yolk acts as an emulsifier to get the fats to stay suspended in the vinegar instead of separating out into their own little blobs.

This is a very good video that talks more about emulsifiers and chocolate.

You can also see the oil-water separation at work when chocolate "blooms," which we talked about when we studied the process of Tempering Chocolate.

When you are melting solid chocolate and adding liquid (like in a ganache), you have to stir in the liquid carefully and add enough of it to maintain the emulsion. If you are just melting chocolate to use for dipping, you have to be very careful not to even get a drop of water in the melted chocolate, or the chocolate will seize, like this:
Seizing means the emulsion has been broken and the chocolate becomes grainy and clumpy. It can't be rescued for dipping, although you can still use it by adding a large amount of liquid to it (like adding milk and making a cup of hot chocolate). (More about seizing here.) Seizing can also happen if the chocolate is heated to too high a temperature and "burns."

In spite of the well-known rule that chocolate and water don't mix, we made a very interesting chocolate-water mousse on another day! The guy talks about it in the video I linked above.
To see another emulsion in action, we used these instructions to make homemade mayonnaise. We used our immersion blender and it worked beautifully! It was really fun, too---the moment the liquids suddenly morph into this creamy mixture, it's like magic! It tasted yummy, but if I were making it again, I'd adjust the ingredients just a little. That's the beauty of making it at home, I guess.

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