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My first batch started fermenting 8 days ago. The beer is still fresh and very cloudy, but I'm wondering if its possible to over-ferment a beer?

If I let it sit for another 2 weeks (or however long, the length of time is unimportant to the actual question) prior to bottling will I gain/lose anything?

Thanks!

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4 Answers

up vote 11 down vote accepted

Basically, no. Beer yeast can only eat certain kinds of sugars in wort. And once they've exhausted their food supply, they can't ferment any more and they settle to the bottom of the fermenter. What kind of sugars they eat & how much they eat is dependent on the yeast strain, the wort and the fermentation.

The one time you might 'over ferment' is if your beer gets a wild yeast infection. Wild yeast can eat more types of sugars than brewer's yeast.

But don't worry about wild yeasts right now. A cloudy beer after 8 days is not a big deal. It will probably clarify over time. It might not ever be crystal clear -- because home brewers don't filter or centrifuge their beers like many commercial brewers -- but it will still taste fine.

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Beat me to the punch! –  Pulsehead Jan 24 '11 at 15:29
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While you can't over-ferment, leaving the beer too long on settled yeast can cause off-flavors. Practice is to rack the beer to a secondary fermenter in order to allow it to ferment longer but not on settled yeast. –  Bob Banks Jan 24 '11 at 17:20
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This is not as universally accepted as it once was. I know both hosts of Brew Strong, for example, don't recommend secondary. If your yeast is healthy and your beer uncontaminated, racking to secondary can be skipped. Secondary is useful if you are actually doing a secondary fermentation or you plan to age the beer in the carboy for longer than 6ish weeks. –  Hopwise Jan 24 '11 at 18:07
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Well actually you can over-ferment. Given the right conditions your yeast can autolyze - essentially "exploding" and feeding off itself. I've had a batch do that - but it's easily avoided if you move your batch to a second stage.

With regards to your question, I think you're asking about the clarification of your beer. As the first person answered - let it sit. 3 weeks is a pretty good time to wait and you can pop it into the fridge (if you have room) which will chill it down and help with clearing.

A trick I like to use is Knox gelatin -- which is pretty cheap and you can get at any store. Boil up a cup or 2 of water, add 2 packs and dumpt into the second stage after 10 days or so. The gelatin gloms on to all kinds of particles and pulls them to the bottom - clearing things right up.

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Would using the gelatin change the flavor of the beer at all? –  Mike Fielden Jan 28 '11 at 12:32
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A quick note on how I interpret "over-fermentation":- or, "How to push a good thing as far as it will go". If you want a beer that has more A.B.V. in a bottle, than in your average 6 pack has in total, it is possible. You can force a beer into this condition. If you brew up a wort that has several pounds of malt per gallon the yeast can't ferment it. It may start to ferment it, but the alcohol produced will eventually poison the yeast and further fermentation stops. However - if you start with an average wort, around 4 or 5 % and let the fermentation become good and strong, then every day or so just keep adding dry malt in syrup form or extract malt. The yeast adapts to the slowly increasing alcohol content and it is possible to boost the A.B.V. well over 12%. The only commercial beer, I have tried, that does this is Maximator from Augustiner Brewery in Munich. There is also a Maximater brewed in Amsterdam that is 11.5%
Have a Very Hoppy Brew Year! Kiwi Bruce

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feeding a beer slowly with more fermentables is certainly one way to go. But it is possible to brew 12% beers without having to babysit the beer, but it requires careful attention to yeast pitching rates, O2 levels, nutrients and temperature. Feeding the brew during fermentation avoids all of that, so it's a good simple way to get a higher abv. –  mdma Jan 7 at 15:26
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The answer IMO is yes. While most people don't really mind what the attenuation gets to (as long as it's not too under attenuated (attenuation is the percentage of sugars converted to alcohol)). Certain beer styles are not supposed to be entirely dry (in the fermentation sense dry means well attenuated). It's all about what you want and what you are going for.

You can also get some brettanomyces in the beer by accident which is a yeast that goes well beyond the normal attenuation of the typical beer yeast (Saccharomyces) and brettanomyces produces acid which adds sourness to your beer (which tastes amazing in a lot of styles and is done on purpose more and more).

I do not necessarily disagree with the content of the other answers here, but it goes without saying, if you mean for it to go from gravity readings of 1.070 to 1.018 but it goes down to 1.010. You aren't doing what you mean to. Most yeasts will only have certain tolerances so they under normal circumstances will only attenuate to their normal limits (normally around 75%ish).

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