So I brewed the NB Rye Stout extract kit a few weeks back and I got it in the keg this past weekend. At first it was great, aside from a bit of a green beer taste, but over the past couple of days, it has developed a distinct asparagus-like odor. It hasn’t seemed to affect the flavor of the beer so far, but I have now noticed an asparagus odor to my urine after drinking this beer! I didn’t do anything differently when brewing this one, but the ingredients were over a year old. This was also my first time kegging a beer, but I sanitized everything with star san beforehand. I’m thinking there must be some contamination somewhere, hopefully just in the tap line. Has anyone else experienced this phenomenon? Any other ideas as to the source? Thanks!
If I remember correctly, it’s the sulfur-containing chemicals in asparagus that are responsible for the odor (especially in urine).
There are a few places in the brewing process that may produce sulfury aromas or flavors, most notably from DMS. This is the usually-given advice for dealing with DMS:
[quote]When boiling wort, DMS is driven off through evaporation. It is very important to
always maintain a strong rolling boil for at least one hour. Some brewers boil for
90 minutes to ensure that as much DMS is driven off as possible. Avoid letting
condensation drip back into the wort and never cover your kettle completely during
the boil. Long cooling times can also lead to excess amounts of DMS. Cool your wort
to pitching temperature as quickly as possible with a wort chiller or ice bath. Finally,
a strong fermentation with lots of Co2 production helps to clean up DMS since the
bubbles carry DMS away, so pitching high quality yeast is a must.[/quote]
[quote=“Silentknyght”]
If I remember correctly, it’s the sulfur-containing chemicals in asparagus that are responsible for the odor (especially in urine).[/quote]
Yes. One of the main organic compounds in asparagus that the body breaks down is dimethyl sulfide (DMS). That is almost certainly the culprit.
I agree that it is likely DMS. How to prevent it in the future? Boil harder and longer, without a lid. The chemical that is a precursor to DMS needs a hard boil to get it out of the wort. If you have a lid or long side walls on your boil kettle, it is possible for this DMS precursor to condense and flow right back into your beer, so keeping the lid off and kettle geometry can also be factors. And one of these can cause it. Also, pilsner malt and very pale malts are more prone to DMS, because any greater degree of kilning destroys most of the DMS precursors. Interesting stuff, eh? 8)
However… now I’m also thinking, in a dark beer like a stout, DMS would be pretty rare… are you sure it isn’t closer to a green olive sort of flavor? I’ve experienced that many times in stouts and porters. I think that is due to low acidity & too much roasted malts. In the future, keep your pH from going too acidic by adding like a half teaspoon of baking soda to your boil and you’ll be all set.
So I guess my bet is it’s one thing or the other, but I can’t be sure which one without tasting it myself. You’ll know if it tastes anything close to olives. If not then it might be DMS.
Either way… better luck next time.
Thanks, y’all. It is definitely an asparagus odor, not at all olivey, so I bet DMS is exactly the problem. I did leave the lid halfway on throughout the boil, so I will be sure to never do that again. And it is interesting stuff, dmtaylo2! Anyone learning to brew should be interested in the details. Otherwise, how would we ever get better?
Cool! Yeah, it’s the lid. Keep the lid off!
The Oregon Brewer’s Festival has been pouring a watermelon beer for years now with people lined up to taste it. They’d probably go for a asparagus beer too, for sure. 
It’s all part of keep Portland weird. :roll:
I’m so glad that I live in Vancouver. 8)
