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-   -   Fermenting prune juice (http://www.homebrewtalk.com/f127/fermenting-prune-juice-183227/)

artyboy 06-20-2010 10:59 AM

Fermenting prune juice
So I keep a bottle of prune juice in the fridge for my baby. I bought it about 3 months ago. I haven't needed to give her any for a few weeks. Last time I opened the bottle I noticed that it had mysteriously become lightly carbonated. It still tasted OK so I thought nothing of it. Fast forward to this morning and I noticed that the bottle was bulging a lot. I popped the cap and it was like opening a bottle of soda. It still tastes good but now the body is much lighter, it's starting to get sour (in a good way) and it's heavily carbonated. Obviously, there's something working inside of the bottle. What would you do to try to make use of it? It's been in the fridge this entire time. For now I've just attached an airlock so I don't get a prune juice bomb.

Barc 06-20-2010 07:14 PM

It could be a lager yeast but, most likely, it is some sort of bacterial infection. Were I to use it, I'd probably try to make some sort of odd hybrid and ferment a light pilsner-style beer and then "lager" it with a culture of whatever is in your bottle.

Personally, I'd make a beer I already planned on making and then set aside a gallon of the finished beer and throw this into it and lager it. Or you could ferment some of the wort with it and let it go on its own.

Bacteria typically don't care what type of sugar is in a solution and will go after anything (and acetobacter will also go after alcohol but that's another story) so you could mash low and then use whatever residual sugars that are left in your lager phase or, if you're bolder, you could use it to carb your beer but be careful on that one.

Lots of options...

artyboy 06-21-2010 01:01 PM

I actually have a 1 gallon batch of lager fermenting right now. It's been going for about 3 or 4 days so far. Maybe I'll just fill up the head space with this stuff. There's room for a pint or two. It's my first attempt at a lager, though. I'd kinda like to make sure that I have my process down before I try anything weird. Should I just dump it in now before it finishes fermenting or should I hold off until I start to lager it?

Barc 06-21-2010 03:25 PM

I'd leave the lager alone to make sure you get it right. No point messing with it at this point. I do like you're idea of a smaller batch, though. Much less to mess up.

I would most likely make a weak starter (1.040 or so) using hops. Basically, make up a quart or so of DME and water along with enough hops to make sure no more nasties get in the mix and boil it for an hour or so. Then, I'd pour a portion of your juice into your wort after it has cooled. Treat this just as you would any fermenting beer and seal it up. If it ferments, try the resulting beer. If not, most likely the hops killed off whatever was in the juice and it wouldn't have made much anyway. If you like the result, you can decant and pitch it into a wort or into a beer that's pretty low in final gravity and let it kick the gravity on down to 0... This way, you can actually design a beer around the "juice bugs" you've got, assuming you want to do that and not risk screwing up more than a quart at first and then maybe a gallon or so on the next batch.

That is what I'm thinking, at least.

COLObrewer 06-21-2010 04:37 PM

Add more prune juice . . . . . .Prine anyone?

artyboy 06-21-2010 05:20 PM

There's another idea. The bugs should stick around if I use a portion of it in a beer and then top it up with more prune juice, right?

COLObrewer 06-22-2010 12:54 AM

Sure, you could do the one gallon batch and if it is good, use that for a starter on a 5 gallon batch, and use some more for the "prine", keep some in the fridge for the next batch(es), etc.

Barc 06-22-2010 11:35 AM

I'd make sure this is producing alcohol before stepping it up too much, but that's just me. Too many bacteria out there that produce "sour" and CO2 but no ethyl! :)

artyboy 06-22-2010 02:52 PM

I think you're right barc. I just took an SG reading and it's at 1.070. This stuff is extremely foamy, too. It tastes like slightly sour prune juice with less body. It could be the carbonation that's making it so that it doesn't seem syrupy, though. Maybe I'll just pitch some yeast and pop the airlock back on to see how it turns out.

Barc 06-22-2010 03:15 PM

Don't pitch any yeast. It could basically "kill" any bacteria / yeasts present by out-competing it and then you would lose anything you may have had. Why not try this:

Take a new bottle / jar / fermentation vessle and fill it with some of your prune juice. Pop an air lock on it and let it sit out on the counter / somewhere you can watch it for a day or 2. If it gets a little more lively, you're in luck. If not, it may never do anything.

Assuming it does ferment, keep an eye on it and let it finish up. Take a sample for gravity and for taste. You can then decide what you want to do. You may want to drink the result and make more prune "wine," decant and make a starter for a beer, or pour it down the drain, coroding your plumbing, keeping the family away from the hellish nightmare you've ripped into the fabric of the universe and hope to get the Satan's Anus taste out of your mouth while purging your mind (not to mention body) of it, hoping the memory doesn't scar you too deeply. OK, so the last might be overstating it, but not much.

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