exBEERiment | Impact Grain Crush Size Has On A Helles Bock

Author: Martin Keen

Wort is the sweet liquid that results from the mash, a process where malted grains are steeped in warm water, during which enzymes convert starches into sugars that can be fermented by yeast. In order for this to occur, the malt has to be crushed to allow the water to access those starches. A fairly commonly talked about factor when it comes the mash has to do with how fine to crush the grain, and modern opinions on the matter are rather mixed.

Favored by those who use the Brew In A Bag (or Basket) method, a finer crush is associated with higher and more consistent conversion efficiency, but can cause problems with lautering, and some claim the shredded husks increase the risk of tannin extraction. While a coarser crush has the benefit of creating a more effective filtration bed, hence the reason it’s recommended for those who fly/continuous sparge, this comes at the expense of a few specific gravity points.

I brew on an electric all-in-one system where the grains are mashed in a mesh basket that gets removed from the sweet wort, so I don’t worry about the grain acting as a filtration bed. Moreover, the mesh on the grain basket is such that even the finest grain particulate is easily retained. Curious of claims that too fine of a crush can lead to an astringent beer, I designed an xBmt to test it out for myself!

| PURPOSE |

To evaluate the differences between a Munch Helles where the grains were crushed coarsely and the same beer with a fine grain crush.

| METHODS |

For this xBmt, I came up with a simple Helles Bock recipe that I hoped would allow any impact of the variable to shine through.

I’ve Got My Spine

I started my brew day by adding the same volume of RO water to separate Clawhammer Supply 240v electric systems and adjusting them to my desired mineral profile. While the waters were heating up, I weighed out 2 identical sets of grain then ran both through my mill with the rollers set to a coarse crush of 0.055 in/1.4 mm.

I then changed the setting on my mill to reduce the roller gap, leading to a finer crush, and ran just one of the sets of already crushed grain through it again.

There was a very obvious difference in how the crushed grain looked at this point.

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

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

When each 60 minute mash was complete, I removed the grains then boiled the worts for 60 minutes before chilling them with my CFC.

Refractometer readings showed the wort made from coarse crushed grains had a notably lower OG than the wort made from fine crushed grains.

Identical volumes of wort from each batch were transferred to separate fermenters that were connected to my glycol chiller. When the worts stabilized at my desired fermentation temperature of 54°F/12°C, I pitched a pouch of Imperial Yeast L13 Global into each.

After a few days, I raised the temperature of the beers to 68°F/20°C and let it sit for a week before taking hydrometer measurements showing they finished at the same FG.

At this point, I pressure-transferred the beers to CO2 purged kegs that were placed in my keezer and left on gas for 2 weeks before they were ready for evaluation.

| RESULTS |

Major thanks to the White Street Brewers Guild in Wake Forest, NC for allowing me to collect data for this xBmt at a recent monthly meeting!

A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the beer made with coarse crushed grains and 1 sample of the beer made with fine crushed grains in different colored opaque cups then asked to identify the unique sample. While 12 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, 13 did (p=0.007), indicating participants in this xBmt were able to reliably distinguish a Helles Bock made with coarse crushed grains from one made with fine crushed grains.

The 13 participants who made the accurate selection on the triangle test were instructed to complete a brief preference survey comparing only the beers that were different. A total of 5 tasters reported preferring the beer made with coarse crushed grains, 7 said they liked the beer made with fine crushed grains more, and 1 had no preference despite perceiving a difference.

My Impressions: Out of the 5 semi-blind triangle tests I attempted, I was unable to correctly identify the odd-beer-out, choosing the wrong sample every time. Obviously, I felt these beers were identical in every way, and thoroughly enjoyed drinking them.

| DISCUSSION |

When it comes to milling grain prior to the mash, brewers are often encouraged to refrain from crushing too fine, as the consequent shredding of the husks can lead to astringency causing tannin extraction. While coarser crushes are preferred by those who fly sparge since it creates a more effective filtration bed, full volume BIAB brewers tend to crush finer as a way to increase conversion. The fact tasters in this xBmt were able to reliably distinguish a Helles Bock made with coarse crushed grains from one made with fine crushed grains suggests crush size may have a perceptible impact on beer.

It’d be easy, perhaps even understandable, to presume these results were a function of the beer made with fine crushed grains being more astringent the coarse crushed grain version, but in follow-up conversations, this never came up. While numerous past xBmts have shown that people struggle to distinguish beer based on differences in alcohol, that may very well have played a role here, or it could be something else entirely. What can be said with confidence is that a finer grain crush led to notably better conversion efficiency, which confirms the anecdotal reports of many.

Based on past experiences, I expected the coarser grain crush to result in a lower OG, so that didn’t surprise me much. However, after failing to get a single triangle test attempt correct despite knowing the variable, I was sure tasters wouldn’t be able to tell a difference either, but clearly I was wrong. Given my own inability to distinguish these beers, as well as the fact more than half of the tasters who were accurate on the triangle test preferred the one made with fine crushed grains, I’ll be milling my grains finer from now on.

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

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