One of the properties that both molasses and corn syrup share is their resistance to crystallization. True, in rare cases molasses has been known to crystallize, though I’m betting it wasn’t blackstrap molasses that did it. There are simply too many long-chain sugars (not to mention all the other gunk) in blackstrap molasses to allow that to happen.
What is it about long chain sugars that inhibit crystal formation? If you imagine a single sucrose molecule as a little block, one that’s just waiting for another little block to come along and bond to it, a long chain sugar is like a rope that wraps itself around it, preventing other blocks from grabbing on. Sure, in a sucrose-rich syrup like molasses some sucrose molecules will manage to bond to one another. Yet the crystals they’ll form will be so small our tongues won’t be able to detect them.
Corn syrup creates a similar effect in the world of candy and icings. Say you were making up some poured fondant (a mixture of powdered sugar and water) to cover a tray of petits fours. You want an icing that’s firm enough to hold the cake and buttercream in place, yet not so rigid that it’ll crack and crumble as it dries. In other words, you want some sugar crystallization, but not so much that the entire coating becomes one big hard crystal.
Enter corn syrup with its crystal-inhibiting long-chain sugars. A little in the icing mixture allows some sugar crystal formation, yet not so much that the icing will become either gritty or hard. It works the same magic in chocolate (which, as you may recall from some of last month’s posts, is also composed of crystals…fat crystals).
Quite interesting when you get into it, isn’t it? Or am I still just a nerd?