Peanut Butter Fudge

Fructose is one of the sugars in corn syrup. The problem is that 112 C is above the caramelization temperature of fructose, which is 110 C (230 F); this is uniquely low among the various common sugar molecules, most of which begin to caramelize around 160 C (320 F).

The toffee flavor that you are getting is due to the caramelization components.

However, without seeing your exact recipe it is hard to know what to change. I would suggest using table sugar with its much higher caramelization temperature instead of corn syrup would be the most appropriate solution.

It should dissolve the dairy, so you should not need to make a syrup.

However, sucrose (table sugar) has different crystallization properties than fructose and corn syrup, so after you get the main part of the candy mixture up to temperature and then cooled some, you might wish to add a tablespoon or two of corn syrup to help reduce the likelihood of graininess.

You could also try reducing the temperature to say 108 C, but this may affect the final ratio of water to sugar as less water will have been evaporated off, which would change the crystallization pattern in the confection, and thus is texture. It could end up quite sticky or even gooey.

It will probably be easier to search for a recipe for this confection that is already tuned to do what you want, as modifying candy recipes is very tricky; you must get the science and technique just right.

Note: fudge by its very nature is a a solid suspension of very tiny sugar crystals embedded in a dairy/syrup phase. The cooling and beating in traditional fudge recipes are to control the growth of the sugar crystals, so that they are numerous and very, very tiny (which gives the smooth silky texture) as opposed to larger and fewer (which gives a grainy texture).

As fructose and corn syrup tend to resist crystallization, it is odd to have a fudge like recipe with corn syrup as its main sugar component.

It's a somewhat long shot, but if I were you, I'd give it a try again, using another form of vanilla (maybe precook a pod in the milk, then scrape out the seeds and add them), no corn syrup at all, and pay attention to using sweet butter, not cultured butter.

Fudge is all about forming the right size crystals in the supersaturated sugar solution. From your description, no crystals form at all. This could happen if you inadverently invert your sugar (= split it into glucose and fructose). In home cooking, this is usually done on purpose with acid when making non-crystalized candy. So, just in case that either your butter or your vanilla extract contains some acid, I'd use the versions guaranteed not to have any, vanilla pods and sweet butter. It's not sure that they are doing something wrong, because butter in the supermarket is rarely cultured, and vanilla extract doesn't contain acid normally, but it's better to make sure.

On an industrial level, invert sugar is created with enzymes. While corn syrup starts out as starch and not sucrose, I can imagine their enzymes being able to split the fructose off the sucrose in your sugar too. I don't know what they do to the syrup exactly, and maybe the heat will deactivate the enzymes anyway, but I think it is worth a try to make it with pure sugar, so there is no source for enzymes to land in your fudge and invert it.

If none of these is the culprit, then I'm afraid the next likely explanation is the mechanics of the beating. But maybe it's not about the hand vs. mixer beating as such. It's possible that you've been stopping too early, or that changing the attachment used for beating will change the outcome.