[Kyle.2493]

I wasn't sure where to put this, feel free to move it wherever it needs to be.

I'm presenting an experiment for a group of 1st graders next week, I'm trying to find a good reagent to precipitate sugar out of something like apple juice; since their teacher has been going over some basic life functions, I think it'd be cool for them to see the product of photosynthesis come out of a mixture they're used to seeing.

Now obviously I can't use anything really dangerous, but I can probably get away with some dilute acids and heating the solution over a Bunsen burner.

Thanks for any help you guys can offer.

I'm not opposed to aggregation of the proteins being a side result, they're first graders so I could tell them it's just mostly sugars, in a pinch, something that only precipitates proteins in it could be used, I could lie to them and say it's sugar.
I could also add sugar up to the point of saturation to make the reaction occur quicker/more readily.

[Arkcon]

Hmmm... tricky.  I would like to suggest that you instead go for the chemical test for reducing sugars -- http://www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/D-Fehling-e.htm  the so called Fehling's test.  But you will want to keep these reagents away from very small children.  Precipitating sugars seems very difficult to me.  And you just want a visual.  So maybe you can do this demonstration for them.  Wow, first graders, I remember in the third grade, science class was occupied with living or non-living: rock, a ball, or a girl holding a plant.

[curiouscat]

If I may side-track you; something that changes color, forms beautiful crystals, makes a loud pop (safely!) might be more likely to catch their attention as 1st graders.

Precipitation of sugar from juice (even when done correctly) might be a little  too subtle to interest them.

[Kyle.2493]

For some reason I can't quote (posting from a smartphone), so I'll address by name.

Arkcon:
That looks perfect, that very well may be the experiment I use, I can probably safely use those chemicals, the kids won't be allowed to touch them, a partner and I will conduct the experiment at the front of the class, so theoretically they won't be touching anything.
I'm assuming it's a fairly quick reaction, since I see it's used to test urine for glucose.

Curiouscat:
I'll be visiting the school 2 more times in November, I'd like to do the lead nitrate + potassium iodide experiment later on (along with something producing an orange precipitate, to use some traditional autumn colors), as well as showing how different metals change the color of a flame.
Do you know any experiments off the top of your head that safely produce a bang? All I can think of is striking some red phosphorus, or maybe making some flash paper.