Category Archives: Yeast

Yeast

Liquid yeast: why do I even bother?

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The rising costs of ingredients is not just something professional brewers are struggling with, homebrewers also notice the price increases. And ironically, the ingredient that is the smallest by weight is often the most expensive one: yeast.

When I started homebrewing over 10 years ago, dry yeasts were still considered kind of inferior, with a relatively small choice in yeast strains compared to nowadays, they were thought of as sub-standards products because cold chains weren’t considered as crucial as with liquid yeast, and there was a general association with “that homebrew flavour”, probably also because of improper storage.

Liquid yeast on the other hand was thought to be the gold standard, with a large variety in strains, all with their own unique, interesting flavours and aromas that would give homebrewers a key ingredient to push their beer from lackluster to amazing.

It’s March 2024, and I spent €11.49 on a pack of liquid yeast, allegedly the Pilsner Urquell “D” strain, for which I had to create a starter using malt extract to multiply its cell count and improve its vitality. What really happened though was that the yeast was dead, completely dead, and I only noticed it when the starter did not elicit any fermentation activity whatsoever after more than 24 hours on the stir plate.

Instead, I had to resort to my backup plan and rehydrated and pitched two sachets of W-34/70, probably the most widespread bottom-fermenting yeast strain these days. Full disclosure: I got these two sachets for free from a friend who in turn had gotten them at BrauBeviale last December, but if I had had to buy it myself, it would have cost me €9.98. Not much cheaper, but a lot less hassle, because that W-34/70 was rehydrated and noticeably very active in less than 40 minutes, and after pitching it got past the lag phase in something like 24 to 32 hours (no signs of CO2 production at 24 hours, but happily burping away at 32 hours after the pitch).

Now why do I even bother? In the last 5 years of homebrewing, I’ve been mostly brewing bottom-fermented beers, I tried out a number of dry yeast strains, and they were good, with maybe one exception that I found a bit too fruity (and that is a common criticism). Thinking back about all the different bottom-fermenting liquid yeast strains that I used, there was only one that really stood out, and that was Wyeast 2001 (allegedly the Pilsner Urquell “H” strain) due to its very prominent diacetyl note (perfect for a Pilsner Urquell clone). All the others produced beers where the yeast character was just a standard neutral, bottom-fermented flavour, i.e. not much at all.

Every time I picked a specific yeast strain, I chose it for some expected specific flavour element, or “authenticity”, because clearly, a Czech style requires a Czech yeast strain, no? Really, actually, no. One thing I learned in the last few years was that there is so little difference in the yeast strains, you just won’t taste the difference. My Czech Dark Lager, probably the best beer I ever brewed, was fermented with harvested yeast from a German industrial brewery in its 2022 version, and with Fermentis S-189 in its 2023 version, both of them decidedly not Czech yeast strains, and yet both batches tasted exactly like a Czech beer.

So why should I bother about liquid yeast? I probably shouldn’t. The dry yeast strains I’ve had the most success with were Fermentis W-34/70 (a yeast strain is basically an industry standard in its own right, given how ubiquitous it is), Fermentis S-189 (I couldn’t even describe the differences of it to W-34/70, because they absolutely miniscule), and LalBrew Diamond (again, very similar to the others). Fermentis S-23 is also popular, but I found it a bit too fruity, so not exactly my favourite.

With that many similarities, it all boils down to personal preference and maybe price. At my homebrew store of choice, an 11g sachet of LalBrew Diamond costs €4.14, while 11.5g sachets of Fermentis S-189, W-34/70 and S-23 are sold for €4.83, 4.99 and €4.49, respectively. In my experience, two sachets are usually enough for a 20 liter batch of normal-strength beer.

After the frustrating experience with liquid yeast last weekend, I decided for myself that I simply won’t bother with it anymore. Should I ever have the urge of using a pack of liquid yeast, you will definitely hear about it here.

Yeast

The History of Modern Baking Yeast

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Since the beginning of The Event (remain indoors!), people have been panic-buying flour. Lots of flour. More recently, some people on Twitter have also complained about how ordinary baking yeast is unavailable at the moment. For myself, that’s not an issue, as I have a healthy sourdough culture (named Penelope) that I now use more regularly to bake some delicious bread for both fun and sustenance. But others aren’t so lucky, so a question asked by many is whether brewers yeast is an acceptable substitute for baking yeast.

The short answer is: yes, they’re both Saccharomyces cerevisiae.

The slightly longer answer is: yes, just be aware that the pitching rates in baking are much higher than in brewing, so if you start using dry brewing yeast, your bakes will be very expensive. A good way to deal with this is to keep some of your yeast in the form of dough, like a sourdough, except not sour, and just regularly feed it with sugar or flour. That should make it possible to propagate the yeast for quite a while, making the last pack of bakers (or brewers) yeast last for quite a while longer.

The beer historian’s answer is: yes, they’re both Saccharomyces cerevisiae, and were a focal point of cooperation between the brewing and the baking trade. In the first half of the 19th century, it was common in Vienna for bakers to use top-cropped yeast from the local breweries. It was in fact their main source of yeast. Then something happened: in late 1840, Anton Dreher in Klein-Schwechat (just outside of Vienna) starting brewing using bottom-fermented yeast. His new types of beers became an instant hit in and around Vienna, and of course, other local breweries had to react and also introduced bottom fermentation to their breweries. This change went in fact so quick that within just five years, all the Viennese breweries had switched. The bakers weren’t happy, because that changed the yeast they could get from the brewers: while top-cropped yeast was previously plenty and of good quality, the new type of yeast was harvested from the bottom of the fermentation vessel, and was full of bitter hop compounds, hop resins and cold break (coagulated proteins), which tasted bitter and looked darker than previous yeast, making it unsuitable for baking.

The bakers first tried to import fresh yeast from outside Vienna, but this turned out to be infeasible as the yeast’s quality and health would deteriorate too quickly, so they needed to find another way to get a reliable yeast source, ideally making them independent from any brewers. So the Viennese bakers’ guild started a competition in 1845, announcing that they would award a prize to the person who could produce a leaven that was suitable for completely replacing the much sought-after top-fermenting brewers yeast.

The brewer Adolf Ignaz Mautner of St. Marx brewery went on and developed a system to industrially produce and press yeast. His general approach was fairly simple: first, a mash is produced and converted into sugar, then the mash is cooled and fermented. The resulting yeast can be harvested, washed and pressed.

For the mash, kilned barley malt and rye (in a ratio 1:2) are finely crushed and mashed in with hot water (3.5 l of water for every 1 kg of grist) to rest at 70°C for two hours. This should fully convert all starches into sugar, and also allow other contents of the malt to dissolve. This thin slurry is then chilled to about 28°C using a coolship, and then inoculated with a “mother yeast”, which is basically a smaller amount of the same type of mash that has previously been inoculated with pressed yeast or top-cropped brewers yeast and left to ferment until it is in its most active state. Essentially a yeast starter.

After about 10 to 12 hours, the fermentation is active enough to be covered with a thick foam, the yeast. This yeast is then skimmed and put onto a fine sieve that is slightly submerged in water. The idea here is to dissolve the yeast in the water, while other hard matter from the mash will be caught by the sieve. Using ice, the yeast can be made to fall out of suspension. This watered yeast is then mixed with high-dried wheat or potato starch flour, put into multi-layered linen bags, and then pressed. In terms of yield, 100 kg of crushed malt and rye produce about 8 to 10 kg of yeast, to which about 2 to 5 kg of starch flour are added.

This method is now known as “Vienna Process” and after a few improvements, it won Adolf Ignaz Mautner the Viennese bakers’ guild’s prize.

In later years, more improvements and new methods were introduced, such as a switch to green malt and corn (maize) for the mash, the introduction of single strain yeasts, as well as ways of promoting more yeast budding (and therefore a greater yield), such as aerating the mash or diluting it. These improvements increased the yield from 10% in the 1840’s up to 40% in the early 20th century. But essentially, pressed bakers yeast is still produced using methods that every brewer at the time understood, just used in a way to make yeast, not beer.

Adolf Ignaz Mautner was later made a knight of the Order of the Iron Crown, receiving the hereditary title “Ritter Mautner von Markhof”. While his brewing business was merged with the breweries of Klein-Schwechat and Simmering in the early 20th century to form a public limited company, the Mautner Markhof family remained in the food business. While family sold their business to German food company Develey, Mautner Markhof still exists as a brand in Austria, for products such as mustard (and other condiments), vinegar and pressed yeast.

And that’s how baking yeast has historically been the same as (top-fermenting) brewers yeast, and how its production was turned into an own industry by a brewer using beer brewing methods.

Yeast

A List of Yeast Banks and Producers for Homebrewers

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Nowadays, homebrewers can choose from lots of different yeast strains from various producers and yeast banks. As a reference, I’m putting together all those that I know of and that explicitly cater towards homebrewers. I’m not including commercial or scientific yeast banks because they often do not sell their yeast in homebrewing quantitites for homebrewing prices. Also, if you know of any other places or companies that produce yeast for homebrewers, please let me know in the comments, and I’ll add them to the list.

Liquid yeasts:

Dry yeasts:

Update 2015-11-25:
Another dry yeast supplier I found: Brauwerkstatt

Update 2015-12-25:
Escarpment Labs has recently started making their yeasts available to homebrewers in Canada.

Update 2017-11-02:
Brewlab sells slants of a great variety of British yeast strains for GBP 6.00 per slant plus GBP 5.50 shipping within Europe (GBP 2.50 within the UK).

Brewing, Yeast

Sources of DMS in Beer

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Quite often, when I run into an issue or a question related to homebrewing that is not answered in the usual homebrewing literature or forums, I turn towards scientific literature. One great example is the Journal of the Institute of Brewing, which makes its issues freely available, with literally more than a hundred years of back issues available.

When earlier today, Brülosophy posted lab results about their DMS exbeeriment, their closing statement irritated me a bit:

But, it’s just as possible our understanding of the relationship between DMS and boil length is simply lacking, that our access to modern technology, higher quality ingredients, and better knowledge about brewing processes has reduced the likelihood of problems brewers of yore had to worry about.

That sentence really made it sound like brewing science is only in its infancy. But that’s definitely not the case. Modern brewing science is lots and lots of organic chemistry, microbiology, and even genetics nowadays, so it would be hardly believable that we knew very little about DMS. I vaguely remember seeing an article about DMS on the mentioned journal, so I dug it up, and first posted a link to it in the comment section of that Brülosophy article. But then I thought, why not write about it? Because the paper itself is great.

So, the interesting that I took out of that article is that there are actually two types of DMS precursor. The paper distinguishes them as “active” and “inactive”. Both have different properties, and come from different sources.

“Inactive” DMS precursor is coming directly from the green malt. If you were to product wort from green malt, the precursor would be decomposed, and the wort would end up with large amounts of DMS, and still a certain amount of DMS precursor. During fermentation, parts of the DMS would dissipate through the gases being given off, while the DMS precursor would be metabolized by the yeast. The yeast wouldn’t make DMS out of it, though, hence why that precursor is called “inactive”.

“Active” DMS precursor is the type of precursor that is created out the inactive precursor during the kilning process. After wort production, there would only be a small amount of DMS in the wort, but still a relevant amount of “active” DMS precursor. During fermentation, that DMS precursor is metabolized by the yeast, which makes DMS out of it. Hence the “active”.

This has some interesting consequences. If the kilning can be done in such a way that no “active” precursor is found in the wort, the yeast will not produce any more DMS during fermentation, and the total amount of DMS in the beer is limited by the amount of DMS in the wort right before pitching. It can even be assumed that some of that DMS will be lost during fermentation. The authors suggest that the amounts of DMS formation during wort production need to be controlled, though. In their experience, it is easier to control DMS levels in beer if it’s derived from DMS precursor in the wort, as the final DMS level can be controlled by using a suitable yeast that keeps DMS production low.

And I think the last bit is the crucial point in the Brülosophy exbeeriment: it’s not that a 30 minute boil vs a 60 minute boil doesn’t have any impact for DMS levels, it’s just that both the specific qualities of the malt and the specific metabolism of the employed yeast do matter, and can have a large impact. My guess is: in the exbeeriment, exactly the “right” malt was used (Bestmalz Pilsner malt, apparently), combined with a yeast strain that only produces low levels of DMS (WLP029, a Kölsch yeast strain). And that perfect combination gave a result that made a 30 minute boil indistinguishable from a 60 minute boil in terms of DMS levels. That said, I would really like to see the same experiment done with a different malt (maybe a less modified floor-malted Bohemian Pilsner malt?) and a yeast strain known for greater DMS level, like a lager yeast. W34/70 comes to mind, for example.