Why did the sugars in my rum crystallize and fall out?

[cteavin]

Hi,

This summer I made a huge batch of candied pineapple ending with 70% sugar saturation. I had a bit more than I needed, so I brought the last container down to 80% saturation. After a few days in the container the batch at 80% crystallised. I remelted it twice, but always, after a few days, it crystallised.

I dislike wasting. I put the crystallised syrup and pineapples into a 4 litter container and poured 2 litres of Myer's Rum over it. To help it dissolve I closed the container and put it in a hot water bath for an hour. The next day I tasted it and it was perfect.

A week later, today, I opened up the cupboard where that batch of pineapple rum is stored and all of the crystals fell out of the rum in a thick layer on the bottom with the pineapple on top. The rum tastes of pineapple, but it's no longer sweet. What happened? I'm curious about the science of what's gone on. I'd also like to know if there's a way to permanently keep it in suspension without adding water. Any suggestions on what to do with it (filter it, remelt it before serving, etc)?

Thanks,

[HungryC]

Sugar precipitated because the solution was supersaturated: more sugar was dissolved in the liquid at a heated temp than can remain in solution at room temp. The pineapple may have encouraged nucleation, as it changes the pH of the sugar syrup.

Invert sugar (mix of glucose & fructose) is typically used to reduce crystallization.

[keychris]

80% shouldn't be enough for it to be considered supersaturated (for sugar, that is). But there's still a heck of a lot of sugar sitting in solution and it wouldn't take much to cause it to start precipitating out.

[minas6907]

Why wouldnt 80% be considered a super saturated solution? Isnt the saturation point for sugar at room temp around 62-63% brix? Also, was there any glucose included in the syrup used to candy the fruit?

[keychris]

I think I messed up my thought process for the calculation, 200g sucrose + 100g water is about 66% which is close enough to your number that I'm happy to say I was incorrect

unless I'm completely misremembering those numbers from chemistry, many years ago!

[minas6907]

Hahaha no worries, I thought something sounded funny. I thinkbthebonly reason its fresh in my mind is I went through a candied fruit phase not too long ago!