Beer School

Beer Varieties: The Origins (Part Four: Bitterness)

In this series, we are looking at what characterises the hundreds of styles of beers that are available. So far we have looked at how gravities and alcohol by volume (ABV.) are calculated, and how colour is measured and named. In this article, we will examine bitterness, the counterbalance to the sweetness from the malt, which is derived mostly from the hops.

Beer Varieties: The Origins (Part Four: Bitterness)

Nothing has changed more about beer in the last 30 or so years than its bitterness. It is also one of the most misunderstood characteristics of beer. Whereas beer colours are rather self evident, and alcohol by volume is pretty straight forward, the measuring stick for bitterness, the IBU scale, while providing hard numbers, does omit many interpretations of what bitterness can be.

Image by: Jimbo’s Beerblog

IBU is an abbreviation for International Bitterness Units, which measures the parts per million of isohumulone found in a beer. Isohumulone is the chemical compound found in hops that gives beer its bitterness. It is created when the alpha acids in hops break down (isomerize) in the boil. Generally, the lower the IBUs, the less bitter the beer will taste. The scale can range from 0 to essentially infinity, however, the human palate can only distinguish amounts up to around 110-120 IBUs before it resigns. Think of your limit with hot sauce; there comes a point when the sauce is so hot, your mouth says “No mas” and the flavour of the food doesn’t exist anymore. It’s much the same with bitterness. While there are beers out there registering 2000 IBUs and more, 99.9% of the beer you will ever come across will be under 120 IBUs.


Although the IBU scale was developed in the early 20th Century as a method to assign a number, or quantify, the bitterness in beer, it has led to some debate, especially in the craft beer community, on just how useful the scale really is. The scale is limited in accounting for the multitude of factors that affect the actual bitterness in a beer, such as the variety of malt, or other additions such as herbs, spices, fruit, vegetables, and other ingredients. Most importantly, it definitely cannot indicate how a beer tastes. The hops themselves have different flavour characteristics that can range from herbal and grassy to piney or citrusy. Also, while the IBU scale will tell you how bitter the beer is, the perceived bitterness may be different for each individual style, not to mention to each drinker, depending on what ingredients are used. In a beer recipe, the more malt used, the higher the gravity will be, indicating more fermentable sugar in the brew. As the gravity goes up, the more the hop bitterness will be masked. So, for example, a 30 IBU Pilsner with a minimal malt character may taste significantly more bitter than a Barleywine with 60 IBUs and a powerful malt profile.


Image by: Brookston Bulletin


What the scale does provide is a general guideline for the consumer. Knowing a beer’s style and how many IBUs it has, will give some sort of a benchmark when comparing two beers of the same style. An IPA with 45 IBUs will almost certainly be less bitter than one with 65 IBUs. However, flavour is more than that; it’s also about the beer’s balance – a delicate descriptor that juggles just how all the beer’s ingredients interplay.



For those who like to know how the empirical IBU number is derived, the formula is (in metric):

IBU = 1000 x (W x A x U)/V

where 1000 is a conversion from milliliters to liters, W is the weight of hops in grams, A is the alpha acid content of the hop as a decimal, U is a percent utilization factor, and V is the final volume of beer in liters. Utilization depends on several factors including; the contact time of hops with the wort, the boiling temperature of the wort, its gravity and pH, what form of hops is used (whole hops vs. pellets and whether hop bags are used), the amount and age of the hops, and the type of yeast in the recipe.

In the North American craft beer market, IBUs are sometimes used as a marketing tool, proudly proclaiming that bigger is better. Believing in that hype will not necessarily lead you into a world of exceptional beers. It is more important to understand beer as the sum of its ingredients; taste the sweetness from the malt, assess the beer’s balance, and learn that hops impart a variety of flavours beyond simple bitterness. It’s all about context – the perceived or relative bitterness is more important than a simple number. Besides, most beers do not have IBUs listed on their label, so you have to judge by style, which is also not always present on the label either. As you try more beers, let IBUs be your guide, not the end point. You will then discover your palate’s happy place, and you will find more beers there than you can consume in your lifetime.


Average IBU Bitterness by Beer Style
Image by: West Coast Brewers


The next article in this series will examine the ingredients that go into beer; malt, hops, yeast, water and adjuncts. We’ll explore what they are and how they contribute to the recipes which determine the various beer styles.

More from the Beer Varieties: The Origins Series

Beer Varieties: The Origins

Beer Varieties: The Origins (Part 2: Gravity)

Beer Varieties: The Origins ( Part 3: Color)

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