DMS Surprise?

Aside from my 17.5% ABV barleywine (which tastes awesome), I have been brewing several session beers this Winter/Spring. Some of the most easily recognized session beers in the world are the British milds and bitters. In a previous post, I outlined the recipe for a Cain's Finest Bitter clone. The yeast for this brew was kind of special. It was Wyeast 1469 West Yorkshire yeast. If you ever brew with this yeast, you may want to decide if its description compares with your experience of its ester profile. The reason I say this is because I had a rather disconcerting experience with this yeast. Although the fermentation progressed as per usual on all three beers it fermented, even a few weeks after bottling the beer produced a rather strong creamed corn aroma and flavor.

"DMS! Oh, no!" I thought. This was a very troubling thought because I consider myself a pretty good brewer and have never had a problem with DMS (Dimethyl Sulfide). DMS is a natural component in beer, especially light colored lagers, but it should not have been a problem in these particular beers because of their dark color and because of my procedures. But the corn was unmistakable, nevertheless. What to do? After sharing and discussing with my brother-in-law without coming to any conclusions, I decided to go out on a limb and send Jamil Zainasheff an email. Here is the contents of my email and his response:

Hi Jamil,

This is Travis from Illinois. I've been brewing all-grain for around 30+ batches now, and this is the first time I've ever had any issues with DMS. I recently brewed a series of session beers (milds and bitters below 4%) pitched on a Wyeast West Yorkshire yeast cake. I did not change any of my procedures for these beers. My rolling boil was uncovered, and wort was cooled from boiling to below 70F in approx. 10 min. Fermentation began after minimal lag time and krauzen appeared normal. The beers were bottled per normal procedures (which have never yielded DMS in the past). Upon pouring, the beers have quite a strong "creamed corn" aroma and flavor. Although I wondered about infection, it seems unlikely as the smell is not of rancid or cabbage (Palmer, J.; How to Brew). I suppose it is possible that I simply did not boil vigorously or long enough, but this would surprise me as I said because my procedures were not altered. In addition, each of these (5.5 gallon) batches contained Special Roast and black malt, which I would think would go a long way to cover up any naturally occurring DMS (the base malts were pale and/or mild malts). I wonder, however, if my grain bill was not substantial enough (flavor-wise) to cover up the DMS. I know it's difficult to diagnose problems based on the information in an email, but I'm curious about your thoughts. Thanks.

Much respect and admiration,

Travis

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Travis,

I would suspect maybe the base malt? Is this a new malt you haven't used before? Other possible thoughts are it isn't DMS but something else? Is this the first time you've used the West Yorkshire? Sometimes people are thrown by the extensive ester profile of the WY yeast. Nothing else comes to mind, but like you say, it is hard to say without tasting.

JZ

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So, at that point, I was still somewhat baffled. It was also a good feeling to know that the only thing separating me from homebrewing legend and (now) professional brewer, Jamil Zainasheff, is experience. I wasn't ready to throw out three batches of homebrew, so I decided to wait. I just opened some of these last night (about 1 month after bottling), and the offending aroma and flavor had greatly diminished. Maybe it was the yeast just taking its time to drop out. I'm quite happy with the results (compared to my previous impressions) and will continue to experiment with session beers fermented by this yeast. There is a link above for the Cain's Best Bitter clone. Here is my (still developing) mild recipe:

(Not Quite) Pale Mild

5-gallon batch

OG: 1.032

ABV:  ~3.0%

Color:  14.1 SRM

18.8 IBUs

Grist:

4.75# Mild Malt (4 SRM) 86.4%

0.25# Chocolate Malt (450 SRM) 4.5%

0.50# Table Sugar 9.1% @ 15 min.

Hops:

0.25 oz. East Kent Goldings (7.2 IBU) @ 45 min.

0.75 oz. Eask Kent Goldings (11.7 IBU) @ 15 min.

Yeast:

Wyeast 1469 West Yorkshire strain

Procedures:

Mash @ 155 for 50 min.

Mash out @ 168 for 10 min.

Boil, chill, aerate, pitch yeast, ferment @ mid 60s.

As mentioned, you may want to wait several weeks to drink after bottling, or suspend judgment on their flavor and aroma if sampling early. Enjoy, and be fermentive!