Irish Moss for clearer beer?

Most of my reading this week has been catching up on the “Exbeeriments” presented on the brilliant Brulosophy blog. Every homebrewer uses techniques and ideas that have been passed on as “what you should do” but inevitably there are a few myths and misunderstandings that have become embedded as common knowledge. The Brulosophy Exbeeriments seem to show that not all of them stand up to scrutiny.

Doing side-by-side testing of something you see as a basic truth is about the last thing that most of us think about but when someone has taken the time to do this it always makes interesting reading.  There is a limit to what you can take out of one trial of two batches of beer and a limited sample number but the results are definitely thought provoking and a few of my base assumptions about the right things to do when brewing have definitely been challenged. 30-minute boil just as good as 60-minute boil? Trub in the fermenter is good for the beer not bad for it? Lagers brewed cleanly inside 9 days? Plenty here to get even highly experienced and successful homebrewers agitated.

clear-enoughOf particular interest to me has been the topic of beer clarity. The amount you care about this will vary from brewer to brewer, and there are definitely homebrewers who say it’s not important to them. However it is always the case that (unless the style says otherwise) presenting clear beer into a competition, or to the general public, will be better received than serving up cloudy beer.  It is up to the individual how much time, effort and money gets dedicated to this goal. What I have really picked up on though is that it seems that some of the things that many brewers (including the League of Brewers brew-team) have been doing to get better beer clarity may not be having any effect at all.

For a long time our standard process to deliver beer as clear as we care about has been to add Irish Moss to the boil, at 10 minutes from boil end, followed by a strong crash cool at the end of fermentation. We have not used any fermenter finings and have never bothered with filtering. Generally speaking we get beer that is pleasingly clear, except for the first glass or so that gets served out of the keg.

There seems to be a number of people that are used to adding Irish Moss at 15min boil time. However there is growing consensus that too long in the boil denatures the ingredient and renders it ineffective. It is hard to find any sources much beyond stated opinions but the consensus seems to be that 10min boil time should be the limit, perhaps even suggesting that 5 minutes boil is optimum.

It is sensible to also extend thoughts on Irish Moss to commercial products like Whirfloc and Super Moss. Effectively these have the same active ingredient of carageenan, however the commercial products are refined and concentrated with additives to assist it dissolve. So they are performing the same task of helping reduce trub in to the fermenter, perhaps better than Irish Moss alone does, but the question remains whether this is a sensible goal in the first place.

With this in mind The Irish Moss Effect (a Brulosophy Exbeeriment on what impact Irish Moss has on beer clarity) has made me question the use of it at all. In summary, this post says that the primary purpose of Irish Moss is to make it easier to rack off clear wort to the fermenter, and if you assume that clear wort is a major contributor to clear beer then this makes a lot of sense. However, The Great Trub Exbeeriment and the follow-up Impact of Kettle Trub not only question this assumption but to some degree even suggest that more trub in the fermenter can lead to clearer beer than fermenting clear wort does.

The outcome of this Exbeeriment was to conclude that there is no statistically significant difference achieved through the use of Irish Moss. However, given that it is not expensive and that some samplers did notice a difference it is up to the individual whether this ingredient should be a regular step in their brew day.

Broadly speaking it seems the most consistent step that most brewers take to produce clear wort is to crash cool at the end of fermentation. So it is entirely possible that our satisfaction with the clarity of our beer is due to this alone. Certainly, we are now going to stop using Irish Moss for a few brews and see what happens.

In addition, if we are going to add in an extra step to get better clarity beer, then thanks to the Gelatin Effect exbeeriment it looks pretty likely that gelatin is going to be the first thing we try.


Yes, we will still stock Irish Moss, if you choose to keep using it

Yes, we do stock gelatin too!

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3 comments on “Irish Moss for clearer beer?
  1. christian says:

    I use whirfloc to ensure phenolics from the proteins are minimised, as much as anything. I know it works because of the time I forgot it and ended up with a smokey beer. I still end up with quite a bit of trub in the fermenter but it has clumped and collects on the bottom with the yeast rather than being suspended. That said, a lot of protein clumping often happens naturally in the kettle before I add the whirfloc depending on the base malt. I used to add the tablet with 15 minutes to go but now do this at 10 after doing some research.

  2. Aidan says:

    I’m a big fan of the Brulosophy blog, it has some very fascinating stuff, the type of A vs B questions that are on the tops of many home-brewer’s minds. It’s awesome that someone goes to the trouble of doing these side by side experiments and posting the results for us. The great trub exbeeriment confirmed my own experience about trub in the fermenter, it all drops out in the end. Back in October I posted my own comments on the great trub exbeeriment here:
    I hadn’t read the irish moss exbeeriment yet and I still use koppafloc as a kettle fining agent. I am under the, perhaps misguided, impression that it helps the trub drop out in the fermenter, not just in the kettle. I reckoned that I noticed an improvement in beer clarity when I went from irish moss to koppafloc but of course that could be due to some other factor. But in any case it’s such an easy step that there’s nothing to loose so I’ll probably keep on using it.

  3. lob says:

    And here’s a piece covering the pros and cons of an increasing trend in the US for commercial craft beer to be hazy:

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