Trouble with Fudge

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mumu

Senior Cook
Joined
Feb 14, 2012
Messages
347
am i doing something wrong....it says in a pan combine the ingr. sugar,sour cream and butter cook over medium heat until sugar is dissolved .Bring to a rapid boil cook and stir until candy ther. is at a soft ball stage. For some reason cant get it to the soft ball stage right. Question,I do leave it on medium heat when i am bringing it to the rapid boil,right?
 
I helps to understand what's happening. The boiling point of a sugar solution is determined by the percentage of sugar. The more sugar that's is actually in solution (not just in the pot), the higher the boiling point. If you remember the thing about boiling points, the solution can't get any hotter than its boiling point, no matter how much heat you apply or how long you boil it.

But here, we're changing the concentration of sugar by boiling off water. The soft ball stage is 235 to 240F. To be able to achieve that temperature, you have to cook off enough water to bring the concentration of sugar in solution up to 85%, and only when that concentration is reached will you be able to get the temperature that high.

Now, the other thing that's at work in this is that you can't dissolve that concentration of sugar in cold water. You could carefully measure water and sugar by weight so that the mix would be 85% sugar, but it wouldn't dissolve. But it will at 238F. You don't want to start off with 85% sugar, because as you heated it, you would cook off some water and drive the concentration (and the boiling point) too high.

So, you kind of sneak up on it by letting the thermometer tell you when you've boiled off enough water. You know, because you can then get the solution up to that temperature. Then, the science part happens. You remember that you have to have it up to 238F to make make an 85% solution, but now you're cooling it, and a cooler solution can't handle that sugar in normal solution. But if things work properly, the mix becomes supersaturated with sugar, and the sugar stays in solution.

This is a critical moment. If you stir it at this point, or if any particle of anything, like a speck of sugar, falls in, or you failed to brush down the sides of the pot above the mixture and left sugar crystals clinging, you get a particle floating free in the mixture, and the supersaturation of sugar will crystalize around it, and your fudge will be grainy. Same with scraping the bottom of the pot when you pour the mix out to cool. Don't do it. If there's a hardened chunk of something on the bottom, it will become the seed for crystals. Good fudge is what scientists call a supercooled liquid. A supercooled liquid is one that has cooled below the temperature where it becomes a solid, but without crystallizing, because we deprived it of a seed to crystallize around. That's why proper fudge is shiny like the surface of glass. Bad fudge is grainy from the sugar that fell out of solution or was excess that couldn't go into solution.

The bottom line on this is that you have to be patient. It just has to boil until enough water boils off. It can't fail, because the water will indeed begin boiling off after you pass 212F. (Actually, it will start a bit higher, because there's already some sugar in solution, making the boiling point a little higher.) If your recipe is a little light on sugar, it will take longer, and the temperature rise may seem agonizingly slow, but it WILL rise eventually. And better to start light than to start with an excess of sugar that won't go into solution until it's at a harder stage.
 
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thanks,i didnt know that. So, i am right to leave it on medium heat for the rapid boil....dont kick it up any?
 
Terms like "medium" and "medium-high" mean different things on different ranges. I would think in terms of something less than "high" and take care that it's not so high that you can't prevent burning. If you feel a clean bottom without feeling a sticky thick layer that's building, you're probably about right. I'd opt for taking longer over taking a chance of burning. The "can't get it higher than boiling point" thing doesn't mean the bottom of the pot isn't getting a lot hotter than that.

All the time you're heating it, more sugar is going into solution as it heats, and the upper limit of how hot it can get increases as more sugar goes into solution. At some point, all the sugar goes into solution. From that point on, you're just interested in the water cooking off and the rising temperature that tells you low much water is coming off. For instance, when you pass 230F, you're at about 80% sugar. So, if the solution is boiling, a hotter burner isn't going to do anything but increase the risk of burning the bottom. I find that I can cut the burner way back and let it boil. There isn't much water to boil off, so there isn't much of that action to carry off heat in water vapor. Doesn't take much burner to hold the heavy solution at boiling.

I always think it should be a peaceful, pleasant experience,without any frantic juggling of burner controls and anxiety over the thermometer. Keep it boiling. Stir it calmly but diligently. And have faith that (1) it will get to temperature, and (2) it won't suddenly shoot past the target if you glance away. It cannot fail to become fudge, and whether it's good fudge or bad fudge depends on what happens AFTER the cooking's done.
 
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