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I use a sugar and glucose syrup mixture and use it to form candies in demonstrations in front of people. When I use it it is between 80 and 90°C. This mixture is prepared ahead and then transferred to a rice cooker until hardened.

Whenever I need it, it takes about 1.5 hours to melt it back completely (rice cooker has to reach 100°C several times) and then I have to wait until it cools down around 80 - 90°C. Around one or two hours later I have to launch it again as it cools down to 70°C (the normal maintaining temperature of a rice cooker). Then I launch it again to heat it up, it gets up quickly to 100°C, and then I have to wait again until it cools down to 80 - 90°C to use it. And the cycle goes again and again.

The fluctuation of 30°C is too big so I am trying to find a different type of container that would allow me to melt down the hardened sugar mixture, then maintain it between 80 and 90°C.

As it is used for demonstrations, I need something that won't take too much space (I had a sort of electric/induction burner with temperature control, with a pot on top, but it takes some space and is too loud)

What I was thinking: Electric soup kettle, I believe the product is similar to a rice cooker, but for some there is a temperature controller (I was thinking of this one https://www.bartscher.com/en/Products/Snack/Soup-pots/Soup-kettle-54L/p/100062, you can find technical details on "downloads"). The only thing is that it is clearly said to be used for soup to be heated up, so would it change so much?

If you have any suggestions, you are very welcome to say so ! :)

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  • That soup kettle would be a right pain to calibrate - that dial might be power (in the form of duty cycle) or temperature (but how closely couple to the contents) and the temperature fluctuations for a given setpoint may be rather large, especially if there isn't much in there. You need something that's known to control temperature, and fairly precisely.
    – Chris H
    Mar 23 at 16:26
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If you need to maintain a certain temperature over time, this is the domain of sous vide cookers. They are typically made for proteins, so if you cannot find one that goes to 90 C, you can use a homemade setup instead (controller + drop-in heater + small pump). It will serve you much better than any purpose-made device, unless you can find something exactly for your use case. If you go with sous vide, don't immerse the heater or pump into the syrup, use a second container (a simple pot will work).

I would be somewhat worried about the long holding though. This is simmering temperature, and you will be losing moisture all the time, changing the ratios in your recipe. Also, I assume you are not making standard hard candy, as the temperature is too low for that. If you have other ingredients, they may not take well to being kept heated constantly, for example if you are making gummy candy, gelatin will not work well (or at all) after being kept for several hours at 90 C.

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  • A decent lid, designed to drip condensation back in (as on some enamel roasters with dimpled lids) would help with the evaporation. And/or run the whole thing on scales and top up
    – Chris H
    Mar 23 at 13:13
  • A lot of circulators will go over 90°C, but they're not designed to be immersed in syrup, so you'd need an inner container. I've repaired one that went to 95°C; Anova seem to go to 92°C. You might do it with one of the slow-cooker-as-sous-vide kits - no pump, but a controller and probe that toggles the mains to a slow cooker (a dumb one, not a fancy clever one)
    – Chris H
    Mar 23 at 16:27
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    @chrish oh yes, certainly, with an inner container. Anything thick enough to make candy with will be a problem for naked immersion. I personally have the parts-combination setup and I'm happy with it, although maybe the commercial ones are even more precise.
    – rumtscho
    Mar 23 at 18:43
  • I might have a try. As for the ingredients it is only sugar and glucose syrup, so there won't be any problem keeping it running for hours, apart from the mixture slowly caramelizing. But in that case, wouldn't electrir soup kettle be similar ? It goes up to 95°C too, so what would be the difference with a sous vide cooker ? cf. bartscher.com/en/Products/Snack/Soup-pots/Soup-kettle-54L/p/…
    – kokoto
    Mar 26 at 10:42
  • @kokoto A sous vide controller is made for one thing only: Hold the exact temperature you set, in very narrow limits. Other appliances are made for their own purpose, and it may turn out that they either treat the knob setting as a vague suggestion and actually keep a temperature far away from it, or that they use some specialized algorithm with complicated heating patterns such that most of the time, you are far away from the desired temperature, even if over enough time, the mathematical average corresponds to the setting. Or maybe the heating algorithm assumes 5 l soup, and ...
    – rumtscho
    Mar 26 at 11:27
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If your amount of syrup is not more than a few liters, you could get a laboratory hot plate (disclaimer: this was just the first link that appeared to me) with temperature control. They exist with temperature feelers, and many support magnetic stirring, too.

(I had this idea because I remember a school experiment where we created fructose-glucose syrup from sugar in exactly such a device, by letting it stir for a couple of hours with a small amount of some organic acid.)

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    If you're going down that route, you need one with a dipping thermometer - the temperature of the plate has little to do with the temperature of the solution on top of it. But then your dipping thermometer should be food-safe (must be if doing this commercially), as do your stirrer beads. Beads are normally PTFE-coated, and the thermometer is normally stainless steel so it's possible, but they're not normally specified for food use. I've got a setup like that in work (not at all food-related)
    – Chris H
    Mar 23 at 13:17
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    I'm not a chemist, but yeah, that's what I meant with the "temperature feeler". Mar 23 at 16:16
  • It might be difficult to heat up 4-5liters of the sugar mixture on a hot plate I believe, Wouldn't it take even more time ? Also, in a rice cooker, even though the heating comes from below as well, the mixture is surrounded by a sort of thermos/thermic material whereas if I put my mixture on a hot plate it would be in a classic heating container, hence the heat will go away more easily ( sorry if my english explanation is not so clear) ?
    – kokoto
    Mar 26 at 10:39
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Best? That would be The Control Freak. However, the downside is that it is fairly expensive.

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  • Dang. Now I have another “I don’t need it, but I want one” on my list.
    – Stephie
    Mar 23 at 13:20
  • @Stephie I'm with you...just can't justify the cost.
    – moscafj
    Mar 23 at 13:22
  • Way over my budget unfortunately
    – kokoto
    Mar 26 at 10:40
  • @kokoto fair point, but you did ask for the "best" solution.
    – moscafj
    Mar 26 at 11:11
  • You are absolutely right :)
    – kokoto
    Mar 29 at 9:57

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