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Beer is under attenuated, what now?

I brewed a Patersbier that had an OG of 1.044. It’s been in the primary for 20 days; I took a gravity reading on day 13 and it was 1.017. I took another one yesterday at day 20 when I racked to secondary and it was still 1.017. Needless to say, fermentation is done and this beer is under attenuated (3.54 % ABV). I tasted it, and it tastes pretty good considering the low ABV, and I’m fine with leaving it as is if need be, but I’d like to get a few expert opinions on this before I do (or don’t do) anything else.

What would you do in this situation?

Best bet is to rouse the yeast and raise the temp a bit and see if that helps. Probably won’t this late in the game though. You could also try pitching more yeast, but that also is unlikely to help. Now that the oxygen is used up (and you don’t want to re-aerate at this point, you’d just oxidize the beer) and the readily available sugars are gone, getting new yeast to take off rarely works. Generally speaking the mistake was made early on - not enough yeast was pitched, or aeration was insufficient for adequate yeast growth. Its also always possible that the wort just wasn’t that fermentable. If you think you did everything right, and assuming this was an extract beer, you can try a fast ferment test with a wort of the same OG made with the same extract. A fast ferment test is when you deliberately pitch way too much yeast to a small amount of wort, ferment it at a warm temperature, and see what you get for a final gravity. This will show you the absolute maximum attenuation you will get with a particular wort.

Edit: you can of course do a fast ferment taste with an all grain wort too, its just that you would want to set aside some wort for the test at the start. After the fact you are unlikely to be able to regenerate exactly the same wort composition.

Is this is an extract brew ? They can be hard to get much lower attenuation. You can try to repitch but I have gotten some funky flavors doing that. I would say just go ahead and package it and enjoy.

This was an extract batch. I have noticed that the majority of my extract brews finish on the high end (usually above 1.01), but I’m pretty sure I underpitched this batch. I used one smack pack of WY 3787, which I activated a good 5 hours prior to pitching. This pack hardly inflated by the time I pitched it, and I’m not sure if it’s because of the yeast strain being a slow starter, or the fact that the pack was pretty old (manufactured on 12/13/13, viability of 35%).

In any case, I messed it up by not making a starter. Lesson learned, I guess. :?

Add a half pound of sugar. Boil it in a little hot water for about 10 minutes, then cool, then add it in. This will jack up your effective original gravity, but once it is fermented out the final gravity should stay exactly the same. Then you’ve got the alcohol you were missing. You could also add more extract in the same manner if you like, but that will raise the final gravity. Either way will help. Keep it between 50-65 F so it can ferment out again. Give it another couple weeks and you should be good to go.

Good to know, and thank you for the advice. I’ve already racked it off the yeast cake, so I’m not sure if I would get the same attenuation anymore. At the same time, if I decided to just go ahead and bottle, would I have any issues with the carbonation (i.e. bottle bombs, under or over carbonation, etc…), provided of course I use the recommended amount of priming sugar? As I mentioned before, the flavor is still pretty good despite the low ABV, so I might just go ahead and bottle it.

Probably will be okay but low alcohol of course. Check gravity again before you bottle. If the gravity decreased by just one single point, then it’s still fermenting and you should give it another week or two to finish up. In that case, warm it up a few degrees to help the remaining yeast finish the job. But if the gravity is still 1.017 after all these days, then fermentation is done and you should be safe to bottle.

Good luck and enjoy.

If it is under pitched you may get a sweet beer adding more sugar?

Doesn’t generally work that way. Unless the beer has sat a very long time and all the yeast has flocculated out, there is enough present to eat up an addition of sugar. Same as priming.

To the OP: did the beer experience temperature swings during the first couple weeks? An underpitch will generally still ferment out fine, but is more vulnerable to problems of stalling if it gets a temperature drop or similar.

Under pitching does not result in high FG.

Doesn’t generally work that way. Unless the beer has sat a very long time and all the yeast has flocculated out, there is enough present to eat up an addition of sugar. Same as priming.

To the OP: did the beer experience temperature swings during the first couple weeks? An underpitch will generally still ferment out fine, but is more vulnerable to problems of stalling if it gets a temperature drop or similar.[/quote]

No temp swings during fermentation. I kept it in my basement which stays at a consistent 65 to 67 degrees. It did take a while to get down to pitching temps on brew day however. When I brewed it, the outside temp was about 19 degrees. Since it was too cold to hook up my hose and wort chiller, I had to rely on the external air temp to bring it down below 80 degrees. It took about two hours to do so, but it eventually got there.

On a side note, I think I’m going to be bottling it today. Does anybody have a recommended volume of co2 for a patersbier?

I think I went with somewhere around 2.8-3.0 volumes on my one and only (so far) patersbier, and I was pretty happy with it.

Time to chill shouldn’t matter for attenuation. There is debate about if the beer will clear better if it is chilled fast, and it is likely that it will have a better shelf life is chilled fast, but I’ve never heard anyone say that would have an effect on attenuation.

Monitor this beer closely just in case you had a stuck fermentation which takes off again in the bottle. Be prepared to stick the whole batch in the fridge to arrest that if needed.

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