The Candy Part of Rocket Candy

Shifting gears a bit, why did the sugar turn brown when I heated the Rocket Candy mixture? That process is called caramelization and is the same as what is used to make caramel candy, toffee, butterscotch, and that blow-torch induced crust on your creme brule. 

Most of us may know that much. Anyone who cooks at all probably is familiar with what happens when sugar is heated.

I thought I'd look up what is happening chemically. I had a vague feeling that hydrogens and oxygens were burning off and leaving a more carbon rich mixture behind, but I was not sure.

Apparently this process is quite complicated and not fully understood. A good definition would be the removal of water from sugar (yes!), proceeding to isomerization and polymerization of the sugars into various high-molecular-weight compounds. Huh? I think I was right about H and O being being off. After that it gets complicated. I believe what it is saying is that what is left of the sugar starts combining into other bigger molecular structures. These compounds have a characteristic color (brownish orange) and flavor. 

According to wikipedia, the brown colors are produced by three polymer groups: caramelans (C24H36O18), caramelens (with an 'e' not 'a' - C36H50O25), and caramelins (with an 'i' - C125H188O80). Those are some big molecules! Wikipedia also states that the favor comes from another smaller by-product chemical named diacetyl ((CH3CO)2) which is added to foods sometimes to impart a buttery flavor.

So this is too complicated for me to describe in the form of a reaction. I try to always mention that burning reactions are oversimplified. The reactions described in the Rocket Candy post and postscript are not going to be great models for carmelized sucrose. This may also explain why 35% sucrose is prescribed rather than the 26% that stoichiometry would specify. Some of that excess weight burns off in the form of water vapor. All of the carbons remain, as the fuel, so the overall reaction still works at a functional level.    

Note that the 26% unmelted sucrose reaction in the next post went just as planned. Perhaps if I had melted that mixture first there would have been a problem, at least in terms of how much product is useful for propulsion. 

Thanks for reading,

Paul