Why is Corn Syrup a key ingredient to Peanut Brittle?

I have been told that light corn syrup is good for delaying the crystallization of sugar.

Additionally, it has been clarified to be perfectly clear and is often favoured with vanilla. This means using light corn syrup will taste a little different and will make your brittle clearer.

Corn syrup or glucose are added to recipes to stop the re-crystalization of the sugar in the finished product. Butter Tarts being an example. john

another reason is that corn syrup is a liquid sweetner consisting of water, a vegetable gum called dextrin, and various sugars primarly dextrose(glucose) the vegtable gum helps it keep its good strong shape and give you a crisp crack. and also it it aids in retaining moisture.

OK, but what about caramel. What happens there? No syrup in that. Does it remain soft or will it also harden at 300F?

Just trying to understand.

The longer you cook sugar solutions, more water is evaporated. If you want a soft caramel, you stop the cooking at a lower temperature. As others have stated, the corn syrup is added to sugar solutions to inhibit crystallization. You are starting with a saturated solution of rather pure sucrose in water and are further concentrating it by boiling off the water. Eventually the sugar molecules will want to form very large crystals and result in an undesirable texture. Glucose has a different crystal shape than sucrose. Putting some glucose (or other sugar) in with the sucrose helps prevent the crystals from forming. If you had a big bag of wooden block that you continually drew closed with a draw string, eventually a lot of the blocks would touch and form large cubes (crystals) made of many smaller blocks. If you started with blocks and added a bunch of tennis balls, when the bag constricted, the blocks wouldn't be able to join into large units (crystals) because the tennis balls would be randomly interspersed.

Another approach to the problem of crystallization is to add some acid to the pot. When sucrose is heated with acid, some of it turn into fructose. You might take a look at "Cookwise" by Shirley O. Corriher. She does a good job of explaining these things.

...when you add an acid to a sucrose(sugar) solution that is being heated you dont get fructose. what happens is some of the sucrose breaks down into equal parts dextrose and levulose which in baking is called invert sugar. this sugar mixture now resists crystalization and provides you with a smoother less grainy candy. this is why an acid like cream of tater is added to sugar syrups...

Sorry. You are right about that.

no problem,