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I'm trying to make a fudge inspired by some I have seen made in a fudge shop here in the UK (although it is an American-style fudge, not the softer British kind). The recipe the shop uses substitutes cream for the butter in traditional recipes, and uses pure corn syrup as the sugar. They manage to get the fudge to stay completely white, without it browning at all, yet when I try to replicate this at home I always get a pale brown colour with a toffee flavour that isn't present in the shop-made fudge. The process I'm using is this:

  • Mix milk, cream and corn syrup
  • Heat to 112C
  • Add vanilla
  • Pour into a cold tray to cool
  • Stir and stretch for the final phase of cooling

Any suggestions what might be going wrong?

Jules
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  • What corn syrup are you using? – ElendilTheTall Jun 25 '13 at 10:59
  • Are you sure it is 112 C and not 112 F? Or why do you heat it to 112 C? – Mien Jun 25 '13 at 11:13
  • The corn syrup is a korean corn syrup (the only reasonably-priced syrup I can purchase locally). I'm not quite sure, therefore, what type of syrup it is. I can eliminate the presence of oligosaccharides (as discussed in the comments of the answer below) because the syrup's nutritional info states 72g/100ml carbohydrates, of which 72g sugar. From the clear colour, I presume it is not a high fructose syrup (all of which I've seen before have a golden brown colour). But beyond these deductions I do not know the exact composition. – Jules Jun 27 '13 at 16:51

1 Answers1

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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.

SAJ14SAJ
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  • Did not know that about fructose. It might be best to do most of the heating in a double boiler (100°C), so as to minimize time on the hob when bottom of pan is exposed to full burner temperature. – Wayfaring Stranger Jun 25 '13 at 13:09
  • @WayfaringStranger Sorry, fudge (and candy in general) cannot generally be made in a double boiler as they *depend* on getting hotter than the boiling point of plain water. – SAJ14SAJ Jun 25 '13 at 13:46
  • @SAJ14SJ My point was that it can be started, heated to 100°C, on a double boiler. You're right in saying you can't finish it wo putting it straight on the burner and getting it up above 100°C, but any time on the burner exposes the material at the bottom of the pan to high temperatures, even if you stir hard. Minimizing the amount of time that can happen will minimize caramelization. – Wayfaring Stranger Jun 25 '13 at 13:56
  • @WayfaringStranger The thing is, this whole recipe is not making sense in terms of the chemistry and desired outcome. A well structured recipe should not require resorting to such strange workarounds. – SAJ14SAJ Jun 25 '13 at 14:00
  • @SAJ14SJ True, then again the shop the recipe came from might have a dedicated fudge cooking setup with a precise temperature controller that'll be hard to replicate at home. – Wayfaring Stranger Jun 25 '13 at 15:13
  • @WayfaringStranger I suspect there are multiple additional unknown factors behind this recipe. – SAJ14SAJ Jun 25 '13 at 15:20
  • Are you sure about the presence of fructose in corn syrup? My understanding was that corn syrup was entirely fructose-free, and was essentially pure glucose syrup except for trace impurities. – Jules Jun 25 '13 at 16:45
  • @Jules Now that you questioned it, I looked, and evidently there are multiple products labelled corn syrup, some of which do not contain fructose. Many HFCS (high fructose corn syrup) varieties are of course *defined* by the presence of fructose. Since the OP is complaining of toffee flavors and color, this indicates unexpected caramelization. Only fructose fit with the temperature specified in the recipe, so I had to assume it was present. – SAJ14SAJ Jun 25 '13 at 16:57
  • Looking into the composition of non-high-fructose corn syrups in more detail, it seems at least some contain oligosaccharides of unspecified type; this may (or may not) be oligofructose, which I believe may decompose to fructose at high temperatures (it seems hard to find hard data about this). This could be the problem. It looks like what I ideally want is a high-maltose corn syrup, which will have had all the oligosaccharides converted to maltose, which does not caramelize at low temperatures. – Jules Jun 25 '13 at 17:05
  • What you want is confectionary grade glucose syrup. In the US, home cooks commonly substitute light Karo brand corn syrup because it is the only brand that does not include HFCS in it's blend. Other brands and "Corn syrups" from other countries likely contain HFCS and will not be suitable for this recipe as @SAJ14SAJ has pointed out. In the UK look for Dr. Oetker Liquid Glucose (http://www.oetkeronline.co.uk/products/Liquid-Glucose.html) – Didgeridrew Jun 29 '13 at 18:40