Author: Marshall Schott

One of the cheapest and most often recommended ways to increase the likelihood of producing a clear beer is by adding a teaspoon of a red marine algae known as Irish moss to boiling wort in the last 5-15 minutes. If you’re like me, using Irish Moss or a similar carrageenan-containing kettle fining occurs as a matter of course, purchased by the pound and used in every batch without hesitation. I hadn’t really considered how exactly Irish moss works until a recent brew day when, after adding some to boiling wort, I watched the chunky clumps of protein form almost immediately, something I’d witnessed hundreds of times before. I immediately thought about the fact Irish moss is referred to as a kettle fining, meaning it’s used to produce clearer wort, which made me wonder if it had any impact during fermentation. And what about the results of the trub xBmt where more kettle trub in the fermentor produced the clearer beer? I hit the interwebs and found a plethora of articles on Irish moss including one from the AHA titled Take the Luck Out of Clear Beer With Irish Moss, which explained:

A majority of the Irish moss plant consists of carrageenan, which is key to clarify beer during the boil. Carrageenan has a negative electrostatic charge. Protein clumps from the boiling wort’s hot break are positively charged. Because of the attraction between proteins and carrageenan, larger clumps of hot break material form, making them more likely to precipitate out of suspension in a faster manner. Ultimately the clumps will not make it into the fermenter. (John Palmer, September/October 2003 Zymurgy)

Aha, I wasn’t totally wrong! The sole purpose of Irish moss is to make it easier to rack clearer wort to the fermentor, which presumably leads to brighter beer based on the axiom, clear wort leads to clear beer. Since this didn’t totally jibe with my personal experience of transferring trub-ridden wort to the fermentor, I started questioning how big of an impact Irish moss actually has and decided it best to put it to the test.

But first…

I am certainly not the first to experiment with Irish Moss. In the 6/10/2010 episode of Basic Brewing Radio, James and crew discussed the results of their own BYO/BBR collaborative experiment that seemed to suggest a fairly significant observable difference in clarity when compared to beers made without the fining agent. However, the results of listeners who performed their own experiments were more mixed, with some going as far to say Irish moss is a waste of money. Additional research led me mostly to concerns about the flavor impact of using too much Irish moss and speculation that its use reduces head formation and retention. Agog was I!

| PURPOSE |

To investigate the differences between a beer fined with Irish moss and one that was not.

| METHOD |

I had been chatting with my buddy and Brulosophy contributor, Ray Found, about American Red Ales, as style I enjoy but haven’t brewed in some time. I thought it’d be a fine style for this xBmt and threw together the following recipe.

American Red Ale Batch Size Boil Time IBU SRM OG FG ABV 11 gal 60 min 33.4 13 1.063 SG 1.014 SG 6.5 % Fermentables

Name Amount % Domestic 2-Row 15 lbs 15 oz 72.6 Gambrinus Munich 10 3 lbs 13.7 Crystal 10 1 lbs 4.6 Victory Malt 1 lbs 4.6 Crystal 120 8 oz 2.3 Pale Chocolate Malt 8 oz 2.3

Hops Name Amt/IBU Time Use Form Alpha % German Magnum ~17 IBU 60 min Boil Pellet 12.2 Willamette 60 g/6.5 IBU 15 min Boil Pellet 5.4 Centennial 80 g/8.4 IBU Flameout w/ 15 min stand Boil Pellet 9.9 Willamette 60 g/1.9 IBU Flameout w/ 15 min stand Boil Pellet 5.4 Centennial 30 g in each fermentor 4 days Dry hop Pellet 9.9

Yeast Name Lab Attenuation Ferm Temp SafAle US-05 Fermentis 76% 58°F

Despite my opinions of the Chico strain, I chose to use US-05 for this xBmt because, well, it’s the most popularly used strain in the universe and hence I believed it might be the most applicable. I also happened have a couple fresh sachets lying around that I wanted to use up.

Since manipulation of the independent variable in this xBmt would occur during the boil, I thought it might be fun to try a novel (to me) approach when it came to brewing this beer– rather than perform separate mashes, I would mash a single batch then split the resultant wort into 2 kettles. Utilizing the batch sparge method, I got to mashing.

After an hour, during which I stirred the mash a few times for efficiency’s sake, I collected the first runnings of sweet wort.

A measured amount of 175°F (80°C) sparge water was added to the grains, stirred, then the second runnings collected and added to one of my 14 gallon kettles.

I stirred the single volume of sweet wort for approximately 5 minutes to ensure complete homogenization of the first and second runnings, after which I collected half and added it to my other brew kettle.

I checked the SG of each wort 3 times to make they were the same, which they were. The boil proceeded as usual with hops being added at their scheduled times. I used my precision blade scale to weigh out 5 grams of Irish moss, which is equivalent to approximately 1 tsp, the recommended amount for a typical 5 gallon batch of homebrew. The Irish moss was then added to one kettle with 10 minutes left in the boil, while the other kettle received none.

Using the King Cobra IC with my wonderfully cool groundwater (58°F/14°C), I chilled each batch to my target pitch temp in under 4 minutes, allowed them to sit for about 10 minutes to keep things as fair as possible, then racked them to 6 gallon PET carboys. Rather than immediately move the fermentors into the temp controlled chamber as I usually do at this point, I set a timer for 10 minutes to intermittently document any observed differences.

I always trusted Irish moss had some sort of coagulative effect, but honestly, the differences I observed surprised the hell out of me. After pitching yeast and moving the carboys to the ferm chamber, I collected some of the leftover wort in hydrometer flasks and let them sit out while I finished cleaning up. As predicted, the Irish moss batch was noticeably clearer with a much thicker trub layer than the non-fined sample.

Both beers were fermenting nicely just 12 hours post-pitch.

I came back a day later to discover a fairly drastic difference in the way each krausen looked, with the Irish moss batch much more recognizable than the other.

The brownish layer on the non-fined batch persisted for about 1 more day, after which both beers took on a very similar appearance. I bumped the temp to 70°F to encourage complete attenuation, taking an initial FG sample 1 week post-pitch; specific gravity was the same for both.

The beers appeared to be of equal haziness at this point.

I let them hangout in the warm chamber for a few more days, both ultimately finishing at 1.014 SG. While I’ve made it standard practice to fine my beers with gelatin, I forwent this step due to the overwhelming preference expressed by Brülosophy readers on a recent survey.

I crashed the beers to 32°F for 3 days prior to being kegged, a tad longer than usual due to the fact I didn’t fine with gelatin.

After a few days in the keezer, they were ready to be served and I was awkwardly excited to observe the changes in clarity that might occur over the time they remained on tap. What follows is a temporal look at the beers over a course of about 5 weeks, the one fined with Irish moss is on the left in each one.

You may have noticed slightly less haze in the Irish moss beer starting at about week 3, though to be fair, it took a lot of finagling to get the proper lighting and angle to achieve these results. The only consistent difference I noticed in appearance, starting from that first pour, was the head retention.

The beer fined with Irish moss actually seemed to produce a creamier and stickier foam than the non-fined batch, which I found pretty interesting, as it’s the exact opposite of what I’d heard.

I decided to give these beers more conditioning time than I usually do before presenting them to the tasting panel, spending 4 weeks in my keezer before data collection began.

| RESULTS |

I was invited to chat with James Spencer about this xBmt on an episode of the fantastic Basic Brewing Radio podcast, it was a great time. Cheers to Olan from HomeBrewDad.com for taking the time to evaluate these beers as well!

I convinced a total of 15 people to participate in this xBmt, each was served 1 sample of the Irish moss fined beer and 2 samples of non-fined beer in different colored opaque cups then instructed to identify the unique sample. In order to reach statistical significance, 9 tasters would have had to accurately select the odd-beer-out, though only 8 were able to so so (p<0.05; p=0.09), indicating participants in this xBmt were unable to reliably distinguish a beer fined with Irish moss from one that received no kettle fining.

Prior to analyzing the data, I was convinced I’d discover that the majority who correctly chose the different beer would also report appearance as being noticeably different when comparing only the 2 different beers. Nope, 6 of the 8 correct respondents (75%) perceived appearance between the beers to be exactly the same. The only 2 participants who perceived the appearance to be different were James and Steve from Basic Brewing Radio, both endorsing the beer fined with Irish moss as having better appearance. But even James admitted they almost missed it. Initially, this made me wonder if perhaps some of the blind participants simply paid less attention to appearance than the others. If this were the case, and given the fact significance was nearly reached, one might assume some other factor contributed to the perceived difference between the 2 beers. Let’s have a look!

When it comes to aroma, 3 and 5 of the participants said the beers were not at all and somewhat similar, respectively. Huh. Every person who correctly chose the different beer during the triangle test experienced the 2 different beers as being aromatically distinct. In terms of preference, it was split down the middle, with 4 each preferring the Irish moss and the non-fined sample. Ratings on flavor similarity were slightly different with 6 tasters perceiving the 2 samples as tasting only somewhat similar while the other 2 perceived them to be not at all similar. Furthermore, 5 preferred the flavor of the non-fined beer, while the other 3 thought the Irish moss batch tasted better. Still, no one perceived them as being the same. Regarding mouthfeel, 5 thought they were somewhat similar, 2 reported them as being exactly the same, and only 1 perceived them as being not at all similar. When asked which beer was preferred overall, a small majority (5) selected the beer that was not fined with Irish moss.

Toward the end of the survey, participants who accurately chose the different beer in the triangle test were informed of the nature of the xBmt and asked to pick the beer they thought was fined with Irish moss. I was certain at this point, the beers slightly warmer and each person knowing the variable being tested, everyone would be able to pick the correct beer. Again, I was wrong– 3 people incorrectly chose the non-fined beer.

My Impressions: I sampled these beers side-by-side more than I usually do xBmt beers only because they were on tap so much longer than usual, I couldn’t smell or taste a difference at all. My impressions on what I observed in terms of clarity are best summed in the photos above– the Irish moss beer was clearer than the non-fined batch, though not by much. I’m compelled to believe the differences reported in flavor, aroma, and mouthfeel by participants are a function of expectation bias, at least to some extent. But perhaps I’m wrong, perhaps my inability to perceive those differences has more to do with my shitty palate, perhaps Irish moss really does have an impact on characteristics other than clarity. I don’t know.

| DISCUSSION |

From a strictly statistical standpoint, these xBmt results suggest Irish moss does not significantly impact beer. From a purely observational standpoint, as you can clearly see in the photos above, the Irish moss beer did eventually develop better clarity than the non-fined beer. The fact the very characteristic Irish moss is purported to affect, appearance, is the only one the majority of tasters agreed was exactly the same as the non-fined batch fascinates me, but not because I believe each person’s observations were accurate. I don’t. I’m actually of the opinion participants simply didn’t pay that much attention to appearance, both beers looked “similar enough,” and hence this xBmt was the final push for me to make a change in the way I approach data collection. From now on, participants will be served each sample in opaque cups, an idea I toy’d with before and recently learned is the way it’s done on a professional level.

Nearly every brewer I know uses either Irish moss or Whirlfloc on the belief it will increase the clarity of their beer. At this juncture, I’m fully comfortable saying it may not be necessary, though it would appear to have some impact. I mean, how many times have you forgotten to toss Irish moss into the boil only to end up with perfectly clear beer a few weeks later? I absolutely plan to repeat this xBmt using gelatin to fine post-fermentation and, should the results be as I expect, I’ll likely ditch the practice of using Irish moss altogether. In fact…

Once the data was collected for this xBmt, I thought it’d be fun to play around with gelatin a little bit. This was admittedly uncontrolled, observation-only, fully biased, and totally anecdotal. I transferred the 2 or so gallons from the non-fined keg to the Irish moss keg, which had a similar volume remaining, added the gelatin solution, and pulled a sample just a couple days later.

The beer tasted as I remember it– slightly toasty, slightly roasty with a noticeable caramel malt note that didn’t overwhelm the Centennial hops. I won’t be brewing this beer again, not that it was terrible, I just didn’t like it all that much. Had I fermented it with a different yeast, something like WLP090, it’s possible I would have formed a different opinion.

What do you think? Have you experimented with kettle finings? Maybe you’ve never used Irish moss and your beers always come out bright. Whatever it is, please share your experience in the comments section below. Cheers!

***If you haven’t already, please consider contributing to our understanding of what the modern homebrewer looks like by complete the Brülosophy General Homebrewer survey. Results will be discussed in detail in an upcoming article.

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