2 Kölsch Fermentation Profiles and How to Perfect Them

2 Kölsch Fermentation Profiles and How to Perfect Them

Kölsch yeast is often referred to as being hybrid: a top fermenting ale yeast that can be fermented at lower temperatures. Just like a lager.

Because of this interesting characteristic, brewers have adopted specific Kölsch fermentation profiles unique to the style.

In this post I’ll discuss two Kölsch fermentation profiles and how you can perfect them using testable hypotheses.

A classic Kölsch fermentation profile

The original method for fermenting Kölsch was in an open-topped wooden fermenter.

With the knowledge that lower fermentation temperatures led to a cleaner beer, Kölsch brewers attempted to ferment at low temperatures without stunting yeast activity (Warner 1998).

A typical, old-style fermentation profile consisted of two stages.

First, the brew would be left to ferment at a temperature of around 9c – 13c. At these temperatures, full attenuation would normally be reached within a week.

Second, the brewer would cold-age the brew in underground cellars, where it would sit at between 5c and 7c for a period of between 5 and 7 months (Warner 1998).

Indeed, these temperatures weren’t very easy to achieve without the use of refrigeration equipment. As such, Kölsch brewers used ice that they had harvested and stored in underground cellars (Warner 1998).

Although Kölsch brewers still ferment in open-topped fermentation vessels, their use has recently declined in favour of large, cylindroconical tanks.

A modern Kölsch fermentation profile

Nowadays, a similar two-stage approach is used; however, Kölsch brewers start off by fermenting at a slightly higher temperature of between 18c and 20c (Warner 1998).

Personally, I think that this temperature is too high, and suggest that you use a lower fermentation temperature of between 16c and 18c.

I normally ferment my Kölsch at around 16c with great results.

The duration of this stage will vary, and is based on factors such as yeast strain, pitch rate, health, fermentation temperature and so forth; however, full attenuation should be reached within about five to seven days.

To confirm whether full attenuation has been reached, simply take two gravity readings: one on day five and one on day seven. If the gravity hasn’t dropped during this period, you’ve reached full attenuation.

The brew is then cold-aged at a temperature of between -1 and 1c.

According to Warner, cold-aging typically lasts one to two weeks, but some breweries still age their Kölsch as long as six to eight weeks (Warner 1998).

Personally, I leave the brew to cold-age for about 4 weeks, and never drop the temperature below 1c.

Truth be told, I’ll often shorten this period a bit if I’m getting extra thirsty!

Developing your own fermentation profile

Hopefully, you’ll have noticed that there are two, key variables to consider: temperature and time.

And by changing these variables, you can develop your own unique Kölsch fermentation profile that suits your tastes.

But don’t just go ahead and randomly change ’em.

Use testable hypotheses as the basis for any changes

A testable hypothesis is an ‘educated guess’ that can be tested by changing a variable (for example, time) and recording the outcome.

By using testable hypothesis, you can easily evaluate minor changes to your Kölsch fermentation profile.

Here’s an example of how I use testable hypotheses:

 1) Develop a testable hypothesis

I recently had the opportunity to sit down and taste my latest Kölsch. It was pretty good, but the mouthfeel was off; it wasn’t as clean as I would have liked.

I reviewed my fermentation notes, and recalled that I only cold-aged for 3 weeks. I usually cold-age for longer.

I then wrote down a testable hypothesis: mouthfeel poor because I didn’t cold-age for long enough.

2) Test it

The next time I brew, I can test this hypothesis by increasing cold-aging time.

If, as I suspect, the mouth-feel is improved, I can make sure that all my future brews undergo a similar cold-age schedule.

If no improvement is noted, then I will reconsider my brewing notes and develop a new testable hypothesis to work with.

Important note: if you take this approach, make sure to only change one variable at a time. If, for example, I was to cold-age for longer and modify the recipe, it would be difficult to ascertain whether any improvement were down to the recipe change, or the time change.

As such, it’s best to work with one variable at a time.

And remember, like recipe formulation, small changes can make a big differences to your Kölsch.

Start by making subtle adjustments, and move on from there.

I’ve had incredible success using this approach, and have used it since I started brewing Kölsch. It certainly helps to take some of the ‘guess-work’ out of the mix!

So, go ahead and give it a shot. Make sure to let me know how it goes.

Do you have any tips on developing Kölsch fermentation profiles? See you in the comments!

References:

Warner, Eric. Kölsch: History, Brewing Techniques, Recipes. 1998. Print

Home brew beer fanatic and lover of all things Kölsch. Follow me on Twitter!

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Comments

  1. Chris says

    I brew my Kolsch @ 16 C for a week or so. I do raise it on day 10 or so to 20 C. I do this because I tasted a bit of sulphur when I left it at 16 C. Those last few days @ 20 C is when I really smell sulphur when I open my keezer to see how everything is. The sulphur goes away near the end which is usually on day 21- 23. Yes, 3 weeks for an ale, but that’s how long it takes. I use Wyeast 2565 Kolsch.

    Cheers,

    Chris

    Peterborough, Ontario Canada

  2. Edward says

    Thanks for the article. I’ll be brewing my first Kolsch this weekend.
    Any advice for brewing in hot climates?
    Also, do you transfer to a secondary prior to cold aging?

    Prost!

    Edward

    Dallas, TX.

    • says

      Hi Edward

      Do you have a fermentation chamber?

      I suspect you don’t, otherwise the Texas heat wouldn’t be an issue… Let me know and I’ll try and come up with some suggestions.

      Best

      GB

  3. Edward says

    GB,
    Yes,I do have a fermentation chamber. My bigger issue is getting the wort cooled in a timely manner. It was 104f last brew day, and with my plate chiller got the boiling wort to 82f initially. However, as I continued to cool the wort the temps would slowly rise simply due to being outside in this oppressive heat! All the wort was run through the chiller in about 10 minutes, but I was near 90f by then.
    Then I’ll either give the wort a lengthy ice bath if I need to pitch right away, or, as with my last brew, put the wort in the fermentation chamber until the desired pitch temperature was reached, about 24 hours, then pitch.
    Do you see either of these approaches as an issue to brewing a great Kolsch? What is the desired pitch temperatur?
    Thanks!
    Edward

    • says

      Well, your pitch temp should be the same as the temperature you plan to ferment at.

      So, if your fermenting at 16c, your wort and your starter should both be at 16c (sorry I work in Celsius) before you pitch the yeast.

      I use a chiller made by jaded brewing company – it’s called the hydra – and it works wonders.

      I’ve never brewed in such a warm climate.. Maybe you should take a look at Jaded brewing’s products? They’re excellent quality.

      I wish I could help more, but brewing in hot climates must be a nightmare!

      GB

  4. Edward says

    The high temps make it rough in the summer. I’m going to try and start this weekends brew at 5am to help beat the heat.
    Do you transfer to a secondary before cold aging?

    • says

      No, I never have. The current view in the home brewing circles is that racking to secondary is completely unnecessary unless you plan on having the beer age for a really long time (read: months and months).

      Please let me know how it goes.

      What grain bill are you adopting?

      GB

      • Edward says

        Current grain bill for 5gallon batch:
        10# German Pilsner Malt.
        .5# German Munich Malt.

        Hops:
        Splat 4% AA 1.5oz at 60 minutes. .5oz at 15 minutes.

        Wyeast 2565.

        Your thoughts? Should some wheat malt or carapils be added?

        Making this recipe up at work without any tools/software. Hopefully I’m not too far off.

        • says

          Looks good for me. My last recipe was 95% German Pilsner, 5% carapils.

          I love building recipes without software. That’s actually the topic of my next article.

          Tell me how it goes :)

          GB

  5. Stefan Girgenrath says

    Glad I found your site, great info. And pleasantly surprised to meet a British Kolsch lover …

    Couple things, you don’t seem to mind leaving the yeast trub in the carboy during secondary. Are you not fearful of the alleged yeast autolysis? I was always wondering if there is a truth behind the belief that leaving the yeast for too long can result “in altered flavor profile of the finished product” (must have read quote somewhere, but can’t remember where).

    Staying with the spirit of this blog, setting up an experiment testing the variable “to leave or not to leave” the yeast would be worth testing on a worth split after primary fermentation. But I would not be surprised if you have done something like that already.

    Cheers,

    SG

  6. Chris says

    Not sure if you still check the old entries but I’ll ask anyway :-) It’s great to read about brewing Kölsch. I am from the Cologne area but now live far away from there. To feel more like home again I plan to brew a Kölsch soon.

    Is there any special mash schedule that you recommend? What brought you the best results?

    • says

      To be honest, single mash is fine. I’ve tried more complicated mashes, but it doesn’t make a huge difference. Go on the low side – say, 64-67 c. Sorry for the late reply I’ve been incredibly ill! Can you let me know how it goes?

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