How can my Raspberry Vodka be Fermenting???

[SarzWix]

Yes, another thing gone wrong
I bought some cheap vodka, half filled an empty vodka bottle with raspberry pulp from the jelly bag and a couple of spoonfuls of sugar (I've done this before, with no problems) then filled it up with the voddie. Did the same with a sloe gin bottle (with Grolsch style cap) with the leftover vodka. Put it out in the utility room, and shook it daily for a week. Left it for another week with the intention of straining it today, but yesterday we heard a "POOOMPH, tinkle, tinkle" noise and went out the back to find glass & red vodka everywhere The bigger bottle had the bottom blown off! Then Jez said 'what about this little bottle?' and went to unpop the grolsch-topped one... Oh dear... The pressure must have really built up in that too, because it blew raspberry pulp round the whole room like a volcano

Now, I really don't understand HOW this could have happened Surely the alcohol content of the vodka should have been enough to prevent any fermentation from happening????!!!!! Yeast really stuggles to get much above 15% doesn't it?? I know the vodka was cheap, but it was still at least 37.5%! And the fruit had already had juice extracted from it, so it shouldn't have diluted it down that much!
Again, any suggestions gratefully received!

[di]

...no suggestions,but you've now got me worried about storing mine in a cupboard upstairs that's sat on an almost new cream carpet!!!!!

[BrideXIII]

that is some seriously determined raspberries you have had this year sarwix

[Brewer-again]

what ratio of fruit to vodka did you use and how much sugar, I suppose what I mean is what recipe did you use. Next time up the vodka.

And where did the yeast come from ????

[SarzWix]

what ratio of fruit to vodka did you use and how much sugar, I suppose what I mean is what recipe did you use. Next time up the vodka.

And where did the yeast come from ????

The fruit was only about a third of the way up the bottle, the sugar was a scant tablespoon. I sometimes add a bit extra after the fruit is strained out, but hadn't got to that point yet!
Heaven only knows where the yeast came from, or how it survived the already high alcohol content The second batch I did has had no problems at all (and I'm checking it often!)

I'm trying morello cherries and brandy too

[Hilary B]

Add the sugar to the fruit next time?

[Socks]

This is a common problem when making wines/beers from natural sources.

I imagine what happened was that the raspberry pulp contained sugar, then you added more sugar and the natural yeast bloom on the raspberries caused some secondary fermentation (similar to bottle conditioned beer). Im not sure what type of bottles you use, if you put them in thick bottles (brown real ale type) with a crown cap then you should be ok to a certain extent.

I made a elderflower wine last year and that went ape when i opened it - all over the kitchen!

Oh, and the attenuation of the yeast largely depends on what type of wild yeasts have got in, some will work even at really high alcohol %, some die - the belgians have been playing with wild yeasts for centuries - Gueze Boon being one example of a high strength lambic beer.

[SarzWix]

Thanks Socks The thing that befuddled us the most was thinking that the alcohol content of the vodka was high enough to prohibit any natural yeast from working, but the OH thinks that maybe the raspberry pulp floated and the top surface of it was above the voddie just enough to start fermenting.
Still, I've learnt from the mistake!

[Socks]

No problem.

Its still a bit puzzling, i did a sloe gin in oct and put in about 1/2 pound of sloes, half filled the bottle with sugar and then topped up with gin, no sign of any pressurisation. With sloes you can actually see the yeast bloom on the outside of the berry - a sort of purply powdery coating - and with the sugar in the drink it too ferments out but with no high pressure release. Perhaps my daily tipping and opening and sniffing and looking and ... etc. ensured the pressure was released prior to it becomming built up.

i may try raspberry vodka in the near future as i have my own raspberry canes (no vodka distillery tho) and it sounds nice!

[Mcbee]

if you are still concerned, could you not treat it like wine (put it in a demi-john with an airlock?) That way if it did ferment there would be no build up of pressure and you'd be able to see when it stopped, so you could bottle it.

[Hilary B]

When I make sloe gin (as often as I can find a decent quantity of sloes) it is 'lots of sloes, lots of sugar, add gin a few days later'. There is NO fermentation, because there is just TOO MUCH sugar for it to ferment (it draws out the juice as a syrup) and then the gin prevents fermentation as well.

[SarzWix]

It's not the sugar which prevents fermentation in raspberry vodka - the raspberries already have a natural sweetness so you don't have to add as much as sloes need. The alcohol already present in the vodka should be enough to prevent it - fermentation shouldn't occur above about 20%. This is why distilleries are needed!!

Brewer's yeast tolerate up to about 5% alcohol. Beyond this alcohol level the yeast cannot continue fermentation. Wine yeast on the other hand tolerates up to about 12% alcohol. The level of alcohol tolerance by yeast varies from 5% to about 21% depending on yeast strain.

So as long as you don't dilute the voddie too much (about a third, to just less than a half, of fruit & sugar to vodka), fermentation shouldn't be able to happen!
As I'm fairly convinced that I didn't exceed these proportions, I think the fault lies in me
a) leaving too much air-space
b) not shaking it often enough to keep the fruit covered in alcohol
c) not straining the fruit out soon enough.

As I say, I've learnt from my mistakes...