exBEERiment | Impact Irish Moss Hydration Has On An American Light Lager

Author: Steve Thanos

Despite the recent popularity of Hazy IPA, clear beer is still something some find desirable, and there are numerous ways brewers can achieve this quality. While larger commercial breweries often rely on mechanical filtrations, smaller outfits including homebrewers tend to use less cumbersome and expensive methods, one of which involves adding a unique product called Irish moss to the boiling wort.

Technically known as Chondrus crispus, Irish moss is a species of red algae that contains a notable amount of carrageenan, a negatively charged agent that attracts positively charged particulates. When added to boiling wort, Irish moss attracts haze causing proteins, forming clumps that are heavy enough to drop to the bottom of the kettle, thus resulting in clearer wort in the fermenter.

I’ve used Irish moss extensively in my own brewing, adding a small amount directly to the wort during the last 5 minutes of the boil, which has been shown to have some effect on beer clarity. However, I recently read that Irish moss works best if it’s hydrated prior to being added to boiling wort, something I’d never even considered in the past. Curious of the impact hydration of Irish moss has on beer clarity and other perceptible characteristics, I designed an xBmt to test it out!

| PURPOSE |

To evaluate the differences between an American Light Lager fined with dry Irish moss and one fined with hydrated Irish moss.

| METHODS |

With the hope of emphasizing any perceptible differences, and also wanting a crisp lager on tap, I went with an American Light Lager recipe for this xBmt.

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After collecting 2 sets of water and lighting the flame to get them heating up, I weighed out and milled the grains.

Once the water for each batch was adequately heated, I incorporated the grains then checked to make sure both were at the same target mash temperature.

While the mashes were resting, I prepared the kettle hop additions.

Once each 60 minute mash was complete, I removed the grains and brought the worts to a boil. As the worts were heating up, I hydrated the recommended 1 teaspoon of Irish moss in a small amount of cool water, then with 5 minutes left in each boil, I added they hydrated Irish moss to one batch and the same amount of dry Irish moss to the other batch.

When the boils were complete, I quickly chilled the worts before taking hydrometer measurements showing they achieved the same target OG.

The filled fermenters were placed in my chamber and left to finish chilling to my desired fermentation temperature of 52°F/11°C for a few hours before I pitched a pouch of Imperial Yeast L17 Harvest into each.

With signs of fermentation activity absent after 2 weeks, I took hydrometer measurements showing the beers had reached the same FG.

At this point, I transferred the beers to separate kegs and placed in my keezer where they were left to lager for 4 weeks before they were ready to serve.

| RESULTS |

A huge thank you to Werk Force Brewing Company for allowing me to conduct triangle tests in their brewery. A total of 20 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the beer made with hydrated Irish moss and 2 samples of the beer made with dry Irish moss in different colored opaque cups then asked to identify the unique sample. While 11 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, just 5 did (p=0.85), indicating participants in this xBmt were unable to reliably distinguish an American Light Lager fined in the kettle with hydrated Irish moss from one that was fined with dry Irish moss.

My Impressions: Out of the 5 semi-blind triangle tests I attempted, I correctly identified the odd-beer-out just once, though that was admittedly a lucky guess. To my senses, these beers were identical in every way including clarity.

| DISCUSSION |

In its natural state, Irish moss is a fuzzy green plant that covers stones and old walls on the Atlantic coasts of Europe and North America. However, brewers are familiar with dried version of this carrageenan-rich algae, as it has been used for centuries as a tool for improving beer clarity. While it’s recommended Irish moss be hydrated prior to adding it to boiling wort, many opt to toss it in dry. Interestingly, tasters in this xBmt were unable to reliably distinguish an American Light Lager fined with hydrated Irish moss from one that was fined with dry Irish moss.

In addition to tasters’ inability to tell these beers apart on aroma, flavor, and mouthfeel, objective observations over time demonstrated no differences in clarity, suggesting the hydrated Irish moss was equally as effective as the dry Irish moss. It’s possible that hydration of Irish moss occurs rapidly enough to render pre-hydration with water moot, though perhaps doing so ensures the fining agent will do as it is expected.

Having added dry Irish moss to hundreds of batches, I was not at all surprised by the fact neither tasters nor I could tell these beers apart in the triangle test, and that their clarity was essentially identical. That said, for as easy as the hydration step is, I may start doing it as a form of insurance, though it’s certainly not something I’m going to stress about.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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