View Full Version : Spontaneous fermentation or something?

06-04-2013, 06:36 PM
I've taken to removing a litre from each gallon batch, before pitching, and putting it aside, so's to leave space in the demijohn for foam when aerating. Today, I went to add back in the litre I'd removed from a cyser/braggot hybrid, and noticed the bottle it was in was very firm. Upon opening, it sprayed everywhere. Presumably this was caused by some wild yeast that was in the apple juice I'd used, but I had added some sulphites which should have killed off everything. The gravity had dropped from 1.084 to 1.073.

A few of questions:
- Does wild yeast seem like the most likely culprit here, or are there other things that might have caused this?
- Assuming it is wild yeast, would it still be safe to add this back into the rest of the batch? I'm guessing I should just play it safe and top up with more apple juice and honey instead, but the rest of the batch tastes quite nice, and I don't really want to upset the balance.
- More of an observation: By my calculations, that change in gravity equates to over 7 volumes of CO2. I'm surprised the (plastic) bottle it was in didn't explode.

1.25lb Wildflower honey
0.25kg Wheat DME
4oz Special B
2L Apple juice
Water to 1gal
Yeast: 71B

Chevette Girl
06-04-2013, 08:59 PM
I had something similar happen when I made and fermented my own apple juice, after I'd sulphited it, I had one bottle of juice that dropped from 1.050 to 1.035 before I could get it mixed with the honey and fermenting with my chosen yeast :p I was using K1V-1116 though so I didn't have to worry about any negative interactions, K1V kills other yeasties. I don't think 71B does but if you think you can safely add anything to it without more explosions, you can always sulphite it and give it 24 hours for that to work, then innoculate it with some of the must with 71B and just use triple-layer of plastic wrap and a rubber band as a makeshift airlock, and let it ferment separately or store it in the refrigerator until you need it.

06-04-2013, 09:13 PM
I've got it under balloon airlock at the moment, just to prevent an explosion. I might add some EC-1118 tomorrow, let if ferment dry, and then try a bit to check if it tastes 'off' before deciding whether to combine or not. Would I need to sulphite before pitching the 1118? Also, any ideas about pitching rate? The 5g packs are intended for 23L, but I guess it would need enough to take over the existing yeast.

Medsen Fey
06-04-2013, 09:26 PM
It is either a wild yeast or something from your brewing area that managed to get in. Rather than pitch EC-1118, you might just want to let it run its course - it could turn out to be great.

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Chevette Girl
06-04-2013, 09:28 PM
EC-1118 also has a kill factor, I believe. If you choose to go that route, I'd think any more than half a pack would be way overkill for a litre.

But Medsen's got a point, it could be really nice the way it is.

06-05-2013, 07:27 AM
Hmm, could be an interesting experiment. I'd just assumed that either or the yeast would give up long before it was dry, or that it just wouldn't taste that good. May as well give it a try though.

Chevette Girl
06-07-2013, 01:10 AM
I suspect the differences from different yeast strains will be subtle, it will still turn sugars into alcohol whether it's a saccharomyces cerevisae, s. bayanus or a random candida...

06-07-2013, 03:18 AM
Check the Lalvin/Lallemand yeast list but from memory, 71B isn't very competitive. So there may be potential for conflict.

I'd just shake the hell out of it, then add a half a campden tablet, leave it a day or two shaking it a couple of times daily releasing any pressure then just top up with it.

That way any wild or otherwise yeast should be stunned, most of the sulphite should have been driven off and the 71B can get on with its job........