Apparently DMS is Still a Thing

DMS-Rich Vienna. Don't let
its yummy appearance
foold you!

I've been brewing since the bad ol' days of the mid-1990s. Back then malt quality is not what it is today, so we had to use a lot of tricks to get good beer. One of these was the 90 minute boil, a necessity when using Pilsner malt (and other minimally-modified malts), to drive off DMS. DMS, for those who do not know, is a sulphur-based compound present in malts which in high enough concentrations gives your beer a cooked-corn aroma and a green-vegetable-like flavour.

Obviously, something you don't want in your beer. But, luckily for us, boiling drives it off...hence the old method of boiling lagers (and other Pilsner-malt rich beers) for 90 minutes.

The good news is that malt quality has dramatically improved over the past 20 years, and the levels of DMS precursors in malt are pretty low compared to historical norms - so low that experiments by Brulosophy found it hard to detect, even after short boils. This improvement in malt quality has led homebrewers (including myself) to do things previously unthinkable - no-boil, 100% pilsner malt sours, 60 minute boils for most lagers, etc. Some of the best lagers I've brewed, like the Vienna & Pilsner I brewed last year, used 60 minute boils with great success.

So imagine my disappointment when I brewed a Vienna this year, using all the same methods and near-identical recipe to last years brew, only to find that the resulting beer had an intense DMS aroma and flavour - probably the worst DMS off-flavour I've had in a beer since the late 1990's. The beer is not undrinkable - in fact, I served it at a recent party and received good feedback - but it is flawed and not up to my normal standards. So what went wrong?

Vienna is prepared in a similar manner to Pilsner malt, meaning it has a similar risk of DMS precursors - but should also be subject to the malting improvements over the past two decades. I've brewed beers previously made of 100% Vienna, with 60 minute boils, without issue. But there is one difference - this was my first time using Weyermann Vienna; all previous batches used Vienna malt from Breiss. Although the character of the malt from each manufacturer is very similar, slight differences in their malting process may have led to different levels of DMS precursors in one malt versus the other - this conceivably could occur even on a batch-by-batch basis within the same manufacturer. That said, a google search failed to find any suggestion that Weyermann had higher levels of DMS in their Vienna than Breiss; although I did find a few reports of DMS in Vienna-heavy beers.

A second issue may have been batch size - I did a 40L batch this year, in place of a 20L batch last year. Because I use the same pot for both sizes of brews, the recent batch had half the surface area:volume ratio, which would slow the volatilization of DMS.

A third issue may have been boil vigour; while I have an over-powered burner on my brewing rig, the larger boil volume, brewing of the beer on a cold day, plus a lot of wind on this years brew day, meant that the boil vigour and rate of boil-off were not as good on the more recent batch.

At the end of the day, I think there are a few things to be learned from this batch. The first is that I probably should return to 90 minute boils for beers brewed using malts with high potential for DMS; especially if brewing larger volumes or on a day where boil vigour may be an issue. The second issue is that I should brew mission-critical beers - e.g. those intended for parties - with a bit more lead time, to allow for additional ageing (or a brewing of an alternative beer) should issues like this arise. And lastly, this beer allowed me to relive my youth, through recreation of flavours that were common in the early years of my brewing "career".

Beer on the Brain - Where the Wild Yeasts Roam

A few days ago I posted episode 3 of my "Beer on the Brain" series. This new video looks at new science which finally identifies the wild source of Saccharomyces cerevisiae - and its not fruit or tree bark, as we long thought...

To Vrai or Not To Vrai - Another White Labs Controversy?

The Short Version

Brewing practices in both home and commercial breweries have undergone somewhat of a revolution over the past decade, leading to a cohort of brewers who approach brewing from a much more technical & microbiological perspective. As a direct consequence of this, some commercial yeast products have been revealed to be other than what the manufacturers have stated - in at least some cases, with the manufacturer themselves being unaware that their product was a yeast/bacteria different from what they believed they had. In this blog post we reveal that the yeast sold by White Labs as Brettanomyces vrai (WLP648) - ironically a yeast mis-identified previously by the same manufacturer - is, in fact, a blend of two different yeasts - both are Brettanomyces bruxellensis, but are separate strains...although strains which appear to have evolved from a recent common ancestor.

Some Background

Brewing practices have changed dramatically over the past decade, with procedures such as sour worting, wild captures, and home/brewery isolated yeasts going from rare experiments to commonplace brewing practices. This change in brewing practices has led to some issues with commercially sourced yeasts - as one example, the growth of practices such as sour worting have revealed yeast-contamination issues in packaged "pure" strains of Lactobacillus. Similarly, the more microbiology-centric practices of home and commercial brewers has led to some unexpected revelations, including identification of "Brettanomyces trois" as a unusually flavourful strain of conventional brewers yeast (Saccharomyces cerevisiae). I was part of that effort, and the results of my and others work in identifying this yeast are the subject of a previous post. According to the manufacturer, this mis-identification was due to a chance contamination of "Brett trois" by this strain of Sacc, leading to the release of the "correct" strain of Brettanomyces, under the 'vrai' (French for 'true') strain name.

But is the strain name accurate - is this truly a pure strain of Brettanomyces? Most of us assumed so, even though this strain shows some characteristics when used as a pure culture for primary fermentation that run contrary to how most Brettanomyces behave when used for primary fermentation. When used in primary fermentation, most Brettanomyces act much like Saccharomyces - they rapidly ferment the wort, usually leave some residual sugars behind, and don't evolve over ageing as much as beers do when Brettanomyces are added during secondary fermentation - e.g. there is a lack of phenol production and super-attenuation. Beers brewed with WLP648 do ferment out fairly quickly, but tend to be more highly attenuated than beers brewed with other strains of Brettanomyces as the primary yeast. In addition, beers brewed with WLP648 also show some development during ageing similar to that of beers with Brettanomyces added to secondary - i.e. emergence of phenolic "funk", and additional attenuation of the beer. So is WLP648 simply a more aggressive Brettanomyces than other common brewing strains, or is something else going on?

To our knowledge, it was assumed by other brewers that Brett vrai was simply a somewhat more attenuative strain of Brett - that is - until my friend and brewing collaborator (and co-author of this blog post) Devin streaked WLP648 on a wort-agar plate. Initially, the plate appeared as one would expect of a pure culture - all colonies on the plate appearing similar in size, shape and colouration. But over a longer incubation time smaller colonies began to appear between the larger colonies, leading us to speculate that there may be a second strain of yeast in WLP648.

Using a combination of classical microbiology, microscopy, gene sequencing and test batches, Devin and I explored the two strains of yeast present in WLP648, demonstrating that Brett vrai contains two unique strains of Brettanomyces bruxellensis, strains which share a relatively recent common ancestor, but are otherwise quite different in their morphology and brewing characteristics.

Experimental details can be found below the fold.

My Warm Lagering Method

I must apologise about my poor blogging output over the past year or so, but there have been some big changes behind the scenes which have got in the way of my blogging and brewing...but I've not been completely inactive.

As my regular readers may recall, I've done some test brews using a newer "lagering" method in which lager-style beers are produced using lager yeasts fermented at ale temperatures (post 1, 2, 3 and 4). Motivated by these successes, I've brewed over a dozen lagers using this method in order to refine this process, with my last two batches produced using the same refined method. The first of these was a German-style pilsner; specifically the "Myburger" Bitburger clone from "Brewing Classic Style". Not only was it delicious, but I had trouble telling it apart in side-by-side tastings from its commercial cousin. The second beer was a doppelbock, and was everything I'd expect from the style. The take-home lesson from those two brews is that you can make very good "lagers", true to style, without the need for prolonged cold fermentation. Indeed, the Pilsner was 2 weeks grain-to-glass, and a month for the doppelbock.

All the gory details are below the fold.

Necessity - The Flower Vase of Invention?

I ran into a bit of a hiccup in preparing for a brewday this weekend. I had just finished preparing my starter and was getting it setup on the stir plate. After the usual jostling, I got the stir bar engaged to the magnet in the stir plate and turning slowly. Satisfied that everything was stable, I turned up the speed on the plate, producing the usual satisfying whirlpool in the starter. No sooner than I started my next task - checking my inventory of malt - did I hear a "ping"...followed by the sound of a slow drip of liquid.

Turning around I saw, to my horror, that the plate had thrown the stir bar and cracked the flask (you can see a bit of the crack, left-side of the image). The starter was too big for my smaller flask, so looking around I came across the only available container - a flask of flowers. Long story short, the flowers have been moved to a less visually pleasing container, and a bit of bleach rendered their vase clean and sanitary. The bottom is too thick for the stir plate to work, but it makes for a pretty starter!

Adam's Pale Ale (an APA...get it?)

I've done a poor job of blogging recently, so here's my first attempt to getting back on track. Back in February I helped a friend (Adam) learn to brew on my system. This beer was designed with his tastes in mind - hoppy but not too bitter. A classical-ish American-style Pale Ale...an Adam's Pale Ale...an APA (get it, that's a beer "joke", or maybe a dad "joke"...regardless, its some sort of a joke, I swear).

Appearance: Golden with a modest white head. Sightly cloudy, although not as cloudy as it appears in the picture.

Aroma: Peaches. Lots and lots of ripe peaches...but there are no peaches in this beer.

Flavour: Overall I am happy with this flavour, although I would tweak the balance of flavours if I rebrew this beer. Upfront is a fruity hop character with a slight catty bite - courtesy of the large late addition and dry-hopping with Amarillo and Simcoe hops. Behind this was a slightly sweet, but otherwise fairly neutral, malt backbone. The hop bitterness was low - to my tastes a little too low to properly balance out the malty sweetness and hop fruitiness. Either a lower mash temp, or drawing back on the Munich malt, would give a more pleasant balance of flavours.

Mouthfeel: Modest body, accentuated by a lower level of carbonation, made for a creamy feel to the beer. Aftertaste was malt-sweetness and hop fruitiness. No lingering bitterness what-so-ever in the aftertaste.

Overall: A pretty good beer. The balance of sweet and bitter is a bit more towards the sweet than I would prefer, but its easy-drinking, hop-forward and delicious - just what Adam ordered.

Recipe below the fold.

New Mailer System!

Mailer showing dividing lines, numbering & yeast deposited
on spots 1, 3, 6, 8, 9 and 11. Click for larger image.

As many of my readers know, I run an extensive yeast bank and frequently exchange yeasts with other homebrewers from around the world. In the past I've used a simple mailer system that allows yeast to be sent by letter mail. While this system worked very well, it had two major drawbacks. Firstly, it was a lot of work to prepare the mailers, taking me about an hour to prepare enough mailers to exchange 48 or so yeasts. Secondly, they did not always pack nicely into envelopes, leading to a few envelopes being returned by the post for being too thick for letter mail.

For my last few exchanges I've used a modified form of this mailer system. It is much easier to setup than the old mailers (enough mailers for hundreds of yeasts can be prepared in the time needed to make enough of the old mailers for a dozen yeast), and packs very nicely into envelopes. The only downside is that it is a little more work on the end of the recipient, as multiple yeast are now packed onto a single card.

Full details of the new mailer system can be found below the fold.