SPThirtyThree

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Hey guys,

So I brewed my first maple syrup beer last month. A buddy working on a syrup farm in the northeast shipped some grade C stuff (darker than anything in stores) and I added it after primary (because I wanted to minimize the amount of maple syrup flavor lost in fermentation bubbling), but I assumed I didn't need to boil the syrup first.

Unfortunately, somewhere along the way - probably during the syrup addition - I infected the beer. I first became suspicious when the second fermentation lasted almost three weeks with a steady 2.5" krausen cap, but when the krausen fell and left splotches of milky white on top, I was sure something was wrong. Checking the gravity confirmed my suspicion: the gravity went from 1.047 to 1.012 in the first round of fermentation (4.5% ABV - normal), and then from 1.044 all the way to 1.007 in the second fermentation. I'm no zymurgist, but I'm fairly certain there are no ale yeasts that can achieve 90% attenuation (since the adjusted OG would be ~1.079).

The beer is actually wonderful right now - woody, maple, roasted nose, and a toasted flavor full laced with hot esters and fusels, but I'm worried it will continue to sour and end up tasting too vinegar-y or phenolic or some other dominant off-flavor.

My questions:
1. Any guesses as to what bug got into the beer? Maybe Strepto?
2. Can I stop wild bug activity using practical means? I don't have a filter and I wouldn't dare boil the beer, but I was hoping a temperature drop or a "magical" additive could do the job. Thoughts?

Thanks!

babalu87

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Your beer is fine

The wort has more of an effect on attenuation than yeast.
Maple syrup is about 100% fermentable so thats why your beer is going so low.

If there was a bug in the beer you would surely taste it.

effigyoffaith

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Or if you are still worried you could dose it with sulfite.

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JoMarky

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Combining the posts of the two above: Your beer is most likely fine, but if it will ease your mind you can add sulfites.

Doing a fermentation in "stages" like you did can often have the effect of drying out a beer much more than if you started with all the sugars in the beginning.

dwarven_stout

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Sounds like your beer is probably fine. "Splotches of white" sounds like normal yeast behavior to me. What strain did you use?

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SPThirtyThree

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I agree that I would expect noticeable off-flavors, but I still have a hard time believing that a second fermentation pushed the FG a full 5 gravity points lower than the first fermentation...

And I thought sulfites were only used for stabilizing wine by stopping oxidation. In fact, in this post it's mentioned that sulfur doesn't kill yeast. In any case, I'm not sure I want to risk tainting the batch with a sulfurous flavor, so I guess I'll go ahead and bottle this batch and cross my fingers and hope y'all are right.

Has anyone actually seen the gravity drop really low like this in a second fermentation?

Thanks again.

SPThirtyThree

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The yeast is a London Ale Yeast. I've used it quite a few times and never seen anything like this on the beer. If you want, I can snap a photo.

I was also thinking it might be some non-sugar compoind from the maple tree that got orphaned during fermentation.

electric_beer

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Take a picture, but the fact you added sugar can easily drop it to 1.007. When I mash with minute rice, I've gotten even lower than that! A lot of people add adjuncts and sugar to purposefully dry a beer out.

maskednegator

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40% of your fermentables were simple sugars, it's not surprising that it dropped so low.

JoMarky

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Brewer's and winemaker's yeast are for the most part resistant to sulfites, bacteria definitely are not and I believe wild yeast are also not resistant. Although sulfites also help with oxidation, a lot of winemakers use sulfites almost exclusively as their equipment sanitizer as well.

I use secondary additions of simple sugars whenever I have a higher than normal gravity beer and want it to dry out. If I were you, I wouldn't be concerned. But if you are, then sulfite it.