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Is it possible to remove sugar from a drink (for example, juice) using common household equipment?

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    $\begingroup$ I suspect what you're ultimately asking is whether there is a way to "unsweeten" a drink, i.e. a way to selectively remove sugars from a complicated aqueous solution? That would probably preclude the usage of any sort of technique which involves strong/prolonged heating, as it could change the flavour of the juice. $\endgroup$ – Nicolau Saker Neto Nov 18 '15 at 13:13
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    $\begingroup$ One way that technically would work in some rather constrained conditions is to add a large amount of pure ethyl alcohol to the juice, in which sugar is poorly soluble but most flavourful compounds would still stay dissolved, then filter off the precipitated sugar and evaporate the excess alcohol (if you want...) $\endgroup$ – Nicolau Saker Neto Nov 18 '15 at 13:13
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    $\begingroup$ It's unlikely you'll be able to evaporate all the alcohol, especially not quickly. Since ethyl alcohol is somewhat more volatile than water (pure ethanol boils at 78 ºC), you could heat the juice mildly for a while to remove a portion of it. You could also bubble air through the juice for a prolonged period, though that could oxidize some of the flavour compounds, which I think may cause some souring. If you happen to have a good vacuum pump and a rotary evaporator in your house, that would be most effective, and also very cool. $\endgroup$ – Nicolau Saker Neto Nov 18 '15 at 13:50
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    $\begingroup$ Also, as I mentioned before, this process only works technically. The resulting juice would have a fairly high alcohol content. Also, I really need to point out that pure ethanol for domestic use is almost always sold as denatured ethanol, which is not drinkable. Denatured ethanol usually contains a very bitter substance added to it (often toxic, too), and you don't want to drink any of that. $\endgroup$ – Nicolau Saker Neto Nov 18 '15 at 13:57
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    $\begingroup$ Yeah, the real answer to the question "Can I make this beverage less sweet?" is 'no, not really'. Just try to make it less sweet next time. But if you ask a bunch of science nerds if you can separate the water from a sugar solution, then we will think of (impractical) methods to do so. $\endgroup$ – Jason B. Nov 18 '15 at 20:57
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Why not add yeast to your juice and allow it to ferment? This will depend on the juice having pH and sugar concentrations; look at commercial wine making kits which provide the proper equipment and recipes. If you conduct the fermentation properly without introduction of air, the sugar will be converted to alcohol, which later can be boiled off (see above) to give the sugar-free version of your juice. Otherwise, with air present, the fermentation will go on to form acetic acid and give the juice a vinegary taste.

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  • $\begingroup$ What can I use to precipitate the acid ? $\endgroup$ – R S Nov 20 '15 at 9:04
  • $\begingroup$ I don't know of any way to precipitate acetic acid from dilute solution. You are far better off controlling the fermentation in the absence of air, so the acid does not form in the first place. $\endgroup$ – iad22agp Nov 20 '15 at 12:28
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Just add yeast under anoxic conditions and wait a few weeks, then fractional distillation to remove the ethanol. Also if reverse osmosis removes salt, it should also remove a larger compound like sucrose.

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Technically @Kyle is correct (the best kind of correct), in that boiling the sugar water solution will drive off the water. But any candy maker will tell you that as the water boils off, the temperature of the boiling solution increases, and you just have a more and more concentrated solution. If you keep adding heat then the remaining sugar will burn (my poor caramel!!)

By boiling you can drive off most of the water, but not all. Evaporation at room temp is a way to get rid of all the water, and it can happen faster under application of a vacuum.

I imagine there are also high-pressure microfilters that you can use to separate them as well.

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  • $\begingroup$ Nicolau Saker Neto is closer to what I want than @Kyle, heating will kill the taste. $\endgroup$ – R S Nov 18 '15 at 13:36
  • $\begingroup$ Well, adding a large amount of ethanol to an overly sugary liquid definitely is one way to make it more palatable..... $\endgroup$ – Jason B. Nov 18 '15 at 13:42
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Yes, this is a physical separation. Since sugar ($\ce{C12H22O11}$) has a boiling point of around $\pu{205^\circ C}$ and water boils at $\pu{100^\circ C}$, you can evaporate the water by heating your drink over a stove at any temperature between $\pu{100^\circ C}$ and $\pu{205^\circ C}$ (preferably about 3/4 between, closer to the sugar boiling point).

Depending on your drink you may have to do some other separations (boiling orange juice won't remove pulp). You should be left with sugar in your pot.

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It is possible to remove sugar partially by decantation. Sugar solution is nothing more that a dispersion of the sugar molecules in water due to hydrogen bonding. However, the solution is not perfectly stable since the molecule of sucrose is quite large, therefore we can let it sit on the table for a few hours where most of the denser sugar sink and rest at the bottom. Slowly we can decant the less populated solution into another vessel to have a less concentrated form of juice.

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    $\begingroup$ It's not a suspension: it's a solution. Solutions don't separate on standing. $\endgroup$ – matt_black Jun 1 '16 at 16:24
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    $\begingroup$ Matt is right.. A solution won't separate by sitting. $\endgroup$ – King David Nov 6 '16 at 7:25

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