Solids, Liquids, and Gases
The Theme of Agriculture in Solids, Liquids, and Gases
The Chemistry of Chocolate
Ahh, everyone's favorite subject: chocolate. Who knew chocolate is not only delicious, but educational. Chocolate comes to us from Central America.8 One of the earliest reports of chocolate consumption dates back to the 1500s when the Aztec ruler Montezuma served a cocoa drink to Cortez. Cortez fell in love with the bitter snack and brought it back to his native Spain where it became a popular and expensive luxury. Only the wealthy could afford chocolate until the mid-nineteeth century. Imagine the protests today if only the rich could snag up some M&Ms? The horror.
Why does chocolate melt in your mouth? Chocolate is a homogeneous mixture of ingredients, mainly cocoa and cocoa butter. At room temperature the mixture is a solid, but as soon as the temperature is elevated, it melts. Turns out the temperature of our bodies is high enough to melt chocolate. Why? The main component of cocoa butter is a fat that melts at near body temperature. Sorry M&Ms, but chocolate melts in our mouths as well as our hands.
During the mixing process at the factory, chocolate is a liquid. The cocoa butter in the melted chocolate coats the solid particles of the cocoa, sugar, and milk solids. If the solid particles are too large the chocolate will have a gritty texture—and nobody likes gritty chocolate. The particle size is also directly related to how much cocoa butter must be added. As particle size decreases, surface area increases. A larger surface area means more cocoa butter required to coat all of the solid surfaces.
If the chocolate does not contain enough cocoa butter between the other particles, the candy will be too thick and will not flow into a mold. Manufacturers can fix the problem by either adding more fat to the mixture or adding an emulsifier, which helps keep two mixed things, mixed.
The last chemical aspect of chocolate is crystallization. All chocolate goes through a tempering process. Tempering is a process of heating and cooling candy to prepare it for dipping and molding. This process ensures that cocoa butter in chocolate hardens in a uniform crystal structure. When chocolate is not properly tempered, crystals form that will create crappy crystals. This un-tempered chocolate will be cloudy, gray, lumpy and will remain sticky at room temperature. Tempered chocolate on the other hand is perfect in all ways: shiny, smooth, and delicious.