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Recipe: Koyt, medieval Dutch beer

Medieval brewing

Medieval brewing

For my next brew I’ve decided to do a Koyt, also known as Kuit or Kuyt bier.

Not many people will be familiar with the style. Koyt, also known as Kuit or Kuyt is a beer brewed since the middle ages and is indigenous to my home country the Netherlands. Haarlem brewer Jopen revived the style based on a recipe from 1407 a few years back. Since then there has been a bit of a small renaissance of the style going on. Strangely enough  I could not find any existing recipes. I decided to piece together whatever information I could find and create my own.

Roughly there are two camps in the discussion how to brew a Koyt. One camp brews the style without any hops. Instead they add a bittering herb mix which is known as gruit. Because gruit was taxed in the Netherlands and brewers slowly started to discover the preservative qualities of hops the style moved away from gruit to adding hops. My impression is that this hoppenbier is more often known as Koyt and the version with gruit is known as Gruit Koyt or simply Gruit. Since I’d like to recreate a Koyt, I will be going the hop route for this recipe.

The basis to recreate the style are descriptions and guidelines. This is how Brewers Association 2014 Beer Style Guidelines describes the beer:

Dutch-Style Kuits (Kuyt, Koyt) are gold to copper colored ale. Chill haze and other haze is allowable. The overall aroma character of this beer is grain emphasized with a grainy-bready accent. Hop aroma is very low to low from noble hops or other traditional European varieties. The distinctive character comes from use of minimum 45% oat malt, minimum 20% wheat malt and the remainder pale malt. Hop flavor is similar to aroma very low to low from noble or other traditional European varieties. Hop bitterness is medium-low to medium in perceived intensity. Esters may be present at low levels. Very low levels of diacetyl are acceptable. Acidity and sweet corn-like DMS (dimethylsulfide) should not be perceived. This style of beer was popular in the Netherlands from 1400-1550. Body is low to medium.


This is a description by D. Walsh (10 jan, 2013) that summarised the guidelines for making a Koyt.

The grain bill must contain a minimum of:
– A minimum of 45% by wt. of oats, oat flakes or oat malt
– A minimum of 20% by wt. of wheat or malted wheat
– A maximum of 35% by wt. of Pilsner or Pale Ale malt.

The original gravity / stamwort of the beer must be between 1.050 and 1.080 s.g. / 12.40 – 19.30 ° Plato.

The alcohol content must be between 4,7 and 7,9 vol% (based on a brew house efficiency of approx. 65% and an apparent degree of fermentation of approx. 74%).

The colour of the beer must be between 10 EBC (blond) and 25 EBC (gold/amber). A colour above 15 EBC can be attained using a long boil over an open fire (as done in the middle ages) and not from the grains or malts.

The beer must be fermented with a neutral ale yeast (e.g. not with a Bavarian Wheat beer strain).

The beer is relatively bitter however, hop aroma should stronger than hop bitterness.

Only the following older European (noble) hop varieties may be used:
Hallertau Mittelfrüh, Saaz, Tettnang, Spalt, East Kent Goldings

Hop bitterness must be between 25 and 35 EBU.

No herbs, spices, fruits or other foodstuffs (other that the ingredients listed above) may be used.

The beer may be slightly hazy in clarity.

The beer must have at least a thin layer of stable foam.


The following information over brewing Oat beers has been extracted from ‘The Use of Oats in Brewing’ in Monatsschift fur Brauwissenschaft March/April, 2005 article:

It is recommended to use a (thin) mash thickness of at least 4L/kg. to prevent clumps of dry grain forming during mashing.

The following mash schedule (tested on 100% by wt. oat beers) delivered optimal results:
35° C for 20 min,
45° C for 20 min,
52° C for 15 min,
62° C for 5 min,
72° C for 10 min,
78° C for 5 min.

Sparging/filtration should normally present no difficulties except for the fact that the total spent grains volume will be slightly larger than for normal mashes.

The extract for oats is approx. 20% lower than for barley malt.

The flavour is unique and conjures up associations with: mint, grainy bitterness and paper.

Protein haze will result in a beer that will appear (and remain) slightly cloudy.


Based on all of this I have drafted up the following recipe:

Amount Fermentable
2.5 kg Oat Malt (UK)
1.9 kg Maris Otter Pale (UK)
1.1 kg Wheat (UK)
200.0 g Rice Hulls

Amount Hop Time Use Form AA
20.0 g Magnum (DE) 60 min Boil Leaf 11.6%
15.0 g Hallertauer Mittelfrüh (DE) 20 min Boil Leaf 3.6%
15.0 g Hallertauer Mittelfrüh (DE) 10 min Boil Leaf 3.6%
15.0 g Hallertauer Mittelfrüh (DE) 5 min Boil Leaf 3.6%

Name Lab/Product Attenuation
German Ale Wyeast 1007 75.0%

Batch & Boil
Batch Size 20.0 L
Boil Time 90 min

OG 1.057
FG 1.014
IBU 30
ABV 5.6%
Color 4 SRM
Balance 0.54 – Balanced

Mash Scheme
I will use the mash scheme as proposed in the Monatsschift fur Brauwissenschaft. I will use a thin mash thickness and add rice hulls to prevent a stuck mash. The large amount of oats and wheat this make the mash the most challenging part of this brew

The most obvious deviation I have allowed myself is the colour. It’s a bit lighter than the guidelines state. Instead of adding darker malts, roasting the oats slightly or turning to techniques like decoction mashing I will accept this slight “error”. I might revisit this for a v2 if I like the results of this recipe.

Update after brewday:

My Braumeister came through like an absolute champ with the complex step-mash. Adding the rice hulls was a smart move, none of the feared glue/sticky mash or feared Braumeister fountains. It delivered the OG on the dot.

Update after brewday:
Since I did not have time to make a starter I relied on the yeast smackpack. Fermentation lagged for a bit over a day and then kicked off. I do not like smackpacks and next time I’ll try a starter, unless I want to consciously under-pitch. I kept the temperature at 19 to 19.5 degrees, and let it rise to mid/high 20.something when fermentation took off.

Update after about 9 days of fermentation:
I took a sneaky taste from the fermenter yesterday and it’s coming along really nicely. The colour is a weird light straw and hazy. Strangely enough there is a slight sourness/tart to it which I did not expect. It could be that it’s the malt base, or even some lost brett that was still in the fermenter (I did use Brettanomyces Bruxellenis in this). In any case – the result is quite amazing so far and I can’t wait to bottle and try it. I expected it to be more of a novelty beer, but I can see this one being really drinkable.

Update after 2.5 weeks in fermenter:
When I checked yesterday my FG is now at 1.008, so that’s an attenuation of around 85 percent and an ABV of 6.4%. This is more than I expected. Also there was airlock activity for quite some time.  I will bottle it somewhere this week.

The surprise is that I expected it to be overly bready, but it’s not at all.

Update after 3 weeks in fermenter:
Bottled this in the weekend, will warm conditioning it. I decided to not crash cool it as the malt base will not allow a clear beer.

The beer had a bit of a milky quality to it when I tasted some of it. The sour/tartness seems to have disappeared, but I was drinking a Magic Rock Grapefruit Highwire as my bottling beer… My taste might have been a bit off. :roll:

The milkyness/creamyness is closer to what I would expect from this amount of oats. I’m really curious how this one turns out, to be continued…

Update after 6 days of warm conditioning:
I got a bit impatient and opened one of the bottles up. I’m quite happy with the beer so far. It’s easy drinking, has an interesting malt base because of the oats and is just bitter enough. I’m hoping to take this with me to my Oxford brewers club to get some input from others. The extra few days warm conditioning should make some difference.

I’ve added a picture, still a bit yeasty and head is a  bit thin

IMG_20160415_174203 (1)

Final update:
I got some great responses from the brewers. Brewers like these revival beers. The Friday after I sat behind one of the members who did not see me. He was singing telling his friend about this tall Dutch guy who brewed this weird but really good beer. I’ll take that compliment 😉

When the beer was quite young there was a slight tang of funk on the end of the palette – but it was barely noticable. Most of the brewers did not even pick up on it. With another few weeks maturation in the bottle I can safely say there is Brett in this batch. The taste of Brett developed on the long end of the taste, a bit like an Orval.

I did not spend the care needed to prevent this after my previous batch (Orval clone) and I have no one but myself to blame. When brewing with wild yeast you need to go the extra mile with cleaning.

To be honest it made the beer really interesting. I was afraid it would be a bit boring, but instead there is a lot going on with the malt base and the horse blanket finish. My Orval clone did not work out fantastic, but this does.

It is however not how it should be. I will revisit this recipe – perhaps even use Gruit instead hops.

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