How to Brew Belgian-style Beers, Like a Monk

I recently finished reading Brew Like a Monk by Stan Heironymus, which is a book I strongly recommend if you want to brew a great Belgian-style beer.  The author spoke with many experts in Belgium about their brewing practices, recipes, equipment, ingredients, and history.  As a fan of Belgian beers styles, I learned a lot from the book.  I'll share some of that here.

The most important thing to learn is that Belgian brewers try things that brewers in other parts of the world would not.  They'll experiment with grains, adjuncts, yeast, fermentation chamber geometry, and more, in a quest to make a beer they enjoy.  Many breweries, in fact, create a number of beers that are popular and "pay the bills" while creating a few that are intended only to satisfy the curiosity or taste of the brewmaster.

One interesting point in the book is that the Belgian brewmasters recommend that Americans not try to create a carbon copy of an existing Belgian beer, but instead to brew a beer intended for American beer drinkers that uses elements from the Belgian brewing playbook.  It's not that they view us as competition, but more that this is what they are doing in Belgium - creating beers that match the Belgian palate and sensibility.  They recommend that Americans do the same.

General Brewing Tips for Belgian-Style Beers

As you read the book, you'll see two things.  First, that each Belgian brewery, brewmaster, and beer has some elements to its ingredients, brew process, brewing equipment, etc., that are unique to it. This means that no single set of guidelines and methods will allow you to produce a beer that is identical to your favorite Belgian ale (assuming that is your goal).  Still, as you read the book and consider the recipes and techniques within it, you'll realize that there actually are some generalizations and similarities between the various Belgian breweries and what they do.  Recognizing these could help you produce a much better Belgian-style beer.

Here are some of the patterns I noted in my reading (you might discover more):

• Belgian brewers tend not to be slaves to specific formulations, mashing schedules, etc.  They treat what they're doing as a form of art and focus more on what they want for an end result (e.g., the flavors, color, mouthfeel, aroma) than what goes into the beer and how it's made.
• Most bottled Belgian Trappist ales are refermented in the bottle.  The beer is usually given both fresh sugar and fresh yeast during bottling.  In some cases, this yeast is the same as used to brew the beer initially.  In others, it's a different yeast, often a wine yeast.  
• It's common for yeast to be cropped during high krausen and used to referment and/or to produce the next batch.  The thinking here is that the yeast becomes accustomed to a particular recipe or style and will ferment better.  Eventually though, fresh yeast is used.
• For lighter-colored beers, sucrose is often used in place of the candi sugar rocks commonly seen in the USA.  Belgian brewers don't believe it changes the flavor.  Sugar is used primarily to "dry out" the beer and offset the malt sweetness to make the beer more "digestible" by consumers, as well as higher in alcohol content.
• Sucrose (table sugar) adds gravity and lightens the body of a beer.  Caramelized sugar adds dark beer flavors like rum that dark sugar alone can't.  Turbinado sugar can add some of those same notes.
• Most Belgian brewers start fermentation in a temperature range near 68 degrees Fahrenheit and allow it to climb as high as 84.  Usually they try to pitch on the low end of the yeast's tolerance. While some do put temperature control in place, many let the yeast "go wild" and do what it will, driving temps up or down as it goes.  Brewers who use temperature control generally step the temperature up gradually during fermentation.
• Many have a secondary fermentation stage that takes place in low temperatures (like 32-50 Fahrenheit) over a period of weeks.
• The most common hops varieties used are Czech Saaz, Hallertau, Styrian Goldings.  Others appear occasionally, but are far less common.  Brewers generally view the hops as a balancing element in the flavor, not a dominant one as American brewers tend to do.
• The higher the level of malt extract (LME, DME) in your recipe, the less sugar you should add to the wort.
• Most Trappist beers have a BU:GU (Bitterness Units to Gravity Units) ratio of 1:2 or less.  It's recommended that you aim for a 3:8 ratio for most beers, higher for a tripel and lower for the darker styles.
• Most Belgian beers use only noble hops for aroma.  Some don't use aroma hops at all.

As I noted earlier, these are generalities gleaned from reading all the stories in the book about the Belgian breweries.  If you read each case in the book by itself, you'll find that not all of the above statements are true for every brewery and beer discussed in the book.  My goal above is to give you some general suggestions that you can use in any Belgian-style brewing effort.  You'll have to discard or adjust the guidelines based on your needs and results.

More Tips

The following tips from from a BYO Magazine article I read some time after this book.  The following advice comes from Grady Hull at New Belgium Brewing Company in Fort Collins, Colorado:

• New Belgium ferments their stronger Belgian style beers in the mid 60's (Fahrenheit) based on the flavor profile of their yeast. High-gravity beers with Belgian yeast strains tend to produce high levels of fruity esters.  High fermentation temperatures and lack of oxygen accentuate that.
• New Belgium adds oxygen at the time of yeast addition, as well as a small amount of zinc and yeast nutrient.
• Hull doesn't recommend homebrewers use oxygen stones or bubbling air through the wort unless you have a sterile way to do it.

The following comes from Phil Linehart of Brewery Ommegang in Cooperstown, New York:

• Ommegang tries to keep its fermentations around 79F (26C) because this is the temperature their yeast ferments best at and they want good ester production.  Linehart recommends that homebrewers ferment the beer in a room that is not too cool and remains at a consistent temperature.
• Linehart recommends yeast starters to ensure good yeast health.
• Ommegang's recommended pitch rate is 1 million cells per milliliter per degree Plato of original gravity.  For example, if pitching a wort with an OG of 19, pitch 19-20 million cells per milliliter.
• Linehart says that most of the higher-gravity Belgian style beers are brewed using a large amount of highly fermentable sugars like dextrose or candi sugar.  This boosts fermentability and results in a drier, more drinkable beer.

Vinnie Cilurzo of Russian River offers the following tips:

• The biggest problem Cilurzo sees is that Belgian-style beers don't finish fermenting to a low enough gravity, perhaps due to not enough yeast being pitched or not enough oxygen in the wort.
• Cilurzo recommends starting with a lower original gravity wort and having the beer finish at a lower gravity to wind up with a drier beer with the same alcohol content it would have had if it started with a higher gravity.
• Russian River ferments its Belgian style beers at 62F (17C) for the first couple of days and then lets it free rise up to the ambient room temperature.  This keeps fusel alcohol down as well as some of the bigger esters and phenolics.
• Russian River aerates their wort but doesn't use yeast nutrients.  They use oxygen rather than compressed air.  Cilurzo says that when he was a homebrewer, though, he used an aquarium pimp with a stainless steel carbination stone.

In another article from BYO by Stan Hieronymus (the author of Brew Like a Monk), the following advice is shared:

• Westmalle, Westvleteren, and Achel all use the same yeast from Westmalle.
• Achel pitches at 63-64F and increases temperature to 72-73F during fermentation in cylindro-conical tanks.
• Westmalle pitches at 64F and rises to only 68F during fermentation in closed, square fermenters.
• Westvleteren pitches at 68F and reaches 82-84F in open fermenters.  If fermentation exceeds 84F, they will try to slow the temperature increase.  Unfortunately, their strain of yeast must be treated carefully as cooling too much causes it to go into a survival mode and shut down. In such cases all you can do is pitch fresh yeast. 
• Brasserie Caracole pitches at 77F and allow the yeast to ferment as it will, getting as high as 86F in the summer and as low as 68F in the winter.
• Duvel pitches at 61-64F and lets it rise as high as 84F over 5 days.  They say that starting at a lower temperature leaves some fatty acids behind for ester production which are otherwise used by early yeast growth.
• Westmalle pitches only 5-6 million cells per milliliter for its 19.6 Plato Tripel, which is just over 0.25 million cells/mL/Plato.
• Jolly Pumpkin lets fermentation start in the upper 60s (Fahrenheit) and finish in the mid-80s.
• Allowing fermentation temperatures to gradually rise throughout fermentation helps retain esters and attenuation without getting solventy notes.
• To increase the amount of air the wort is exposed to, try using multiple fermenters. This reduces the height-to-width ratio of the wort and can reduce fermentation temperature increases.
• Chris White of White Labs said that when fermenting a Belgian style ale, "I'd go shallow, and I wouldn't even put an airlock on."
• White also says that Belgian yeasts show a low degree of flocculation and may require filtration or an extended period of conditioning time to get the beer clear.
• Beers with more than 10% of their fermentables as sugar will tend to attenuate further, and even more so at higher temperatures.
• Pitching a little less yeast will give more flavor during growth, but pitching too little causes solventy flavors.  It's important to find the right balance.

I may add more notes here as I read more.

Yeast is King

Much of the flavor in Belgian beers comes from the yeast.  Belgian yeast can give off flavors that are mistaken for various fruits and spices, when those fruits and spices are not included in the beer at all.  Therefore, one of the biggest factors in getting the "right" flavor for a Belgian-style beer is getting the yeast to produce the right flavors.  Pitch rates, fermentation temperatures, and the geometry of your fermenter all play a role in this.

Belgian breweries often pitch lower yeast cell counts than American brewers do, which can improve the production of flavors from the yeast.  This stresses the yeast slightly, causing it to generate more flavor compounds.  Cell counts can be as low as 1 million cells per milliliter of wort, This works out to around 19 billion cells in a 5-gallon batch.  A typical vial of White Labs yeast may contain 75-150 billion cells by comparison.  Most U.S. craft brewers making Belgian styles pitch 1 million cells per milliliter of wort per degree Plato, resulting in even higher cell counts.  The Belgian brewers in the book recommend that you play around with pitching rates to find what works for your recipe, but realize that you could have trouble if you under-pitch.  (Low pitch rates can cause solventy flavors or lower ester production.)

Pizza Port, an American brewery known for its Belgian beers, overpitches cell counts and undercuts oxygen at knockout, forcing the yeast to produce esters.  Fermentation starts at 64 degrees Fahrenheit and is allowed to run without any temperature controls.  If you're worried about under-pitching, this could be an option.

Fermenter Shape Influences Beer Flavor

The shape of your fermenter and the depth-to-width ratio also appears to affect ester production.  Most Belgian brewers aim for a 1:1 ratio in order to get the best from their yeast.  Some even incorporate open fermenters.  It's said that at home brewing volumes, fermenter geometry might not play much of a role, as home fermenters tend to be closer to a 1:1 ratio than commercial fermenters.  Still, this is something you could experiment with by splitting a batch into multiple fermenters to get something closer to a 1:1 ratio.

The book also mentions that cylindro-conical fermenters can reduce the production of esters.  If you're not getting the flavors you want in a conical fermenter, it may be time to switch to a bucket, carboy, or other vessel with a flat bottom.

More to Learn

What I've shared in this post is a small subset of what you'll find in this excellent book.  It shares Belgian brewing history, connections between the many famous Belgian breweries, commentary from brewmasters, recipes, analyses of popular Belgian beers like Chimay and Westvleteren, and more.  If you're a fan of Belgian beers and home brewing, you should definitely read the book.