What's The Meaning Of IBU?

The rate of bittering is an important influence on taste, as the success in the marketplace of the Dogfish Head 60 Minute IPA and 90 Minute IPA has demonstrated. But an IBU scale is more accurate for measuring bitterness than any method based on the rate of hops addition.

IBU is an abbreviation for the International Bitterness Units scale, a gauge of beer's bitterness. What IBUs measure are the parts per million of isohumulone found in a beer. To further define it, IBUs quantify the bitterness of beer by measuring the concentration of bittering compounds such as isomerized and oxidized alpha acids, polyphenols and other bittering chemicals.

Isohumulone is the acid found in hops that gives beer its bitter bite to the taste buds. Though the IBU scale can be used as a general guideline for taste, with lower IBUs corresponding to less bitterness and vice versa, it's important to note that malt and other flavors can mask the taste of bitterness in beer.

IBUs As a Chemical Measurement

Therefore, a beer with 20 IBUs and a minimal malt character may have significantly more bitter taste than a beer with 60 IBUs and a powerful malt profile.

This has led to some debate among the craft community about how useful the IBU scale really is. IBUs aren't always reliable indicators of how beer tastes, depending on the style and ingredients. And the scale itself doesn’t account for a variety of factors that affect the actual taste of bitterness in a brew.

As a Gravity/Hops Ratio chart shows, the more malt that is used in brewing, the higher the gravity will be, or the amount of fermentable sugar in the brew. The higher the gravity, the more hop bitterness will be masked. Also, no two brewing setups are the same, meaning the utilization, or rate at which flavor and bittering elements of hops dissolve into beer is never the same.

Other variables include hop varietals used, the age of the hops, and length of time boiled.

The IBU scale also fails to take into account any other bittering agents – some malts, especially black malt can impart acidity, as can a slew of herbs and spices. In fact, before hops were incorporated into the brewing process, a combination of spice and herb known as gruit was the only way achieve the desired acerbic quality.

Unabbreviated and unexplained, IBUs are little more than a number for the consumer to sink their teeth into. And in the hop-centric American market, bigger and bolder are often equivocated with being better, making a high IBU rating juicy pieces of fruit -- a built-in talking point for all parties.

Beer Bitterness Wars?

The pursuit of hoppiness has created a literally bitter rivalry between breweries.

Flying Monkeys Brewery of Ontario currently leads the pack with “Alpha Fornication,” which clocks in at 2500 IBUs, blowing runner-up Mikkeller’s “Hop Juice X 2007 IBU” out of the water.

What none of these breweries explicitly state is that the human palate can only distinguish up to around 110 IBUs when perceiving the bitterness level of a beer before it tucks into its shell and retreats down the esophagus. While finding cheap beer might be hard, this website makes it easy with their coupons.

It could be argued that IBUs have become as much a marketing ploy as a tool to better help beer drinkers understanding the beverage they are consuming. So if IBUs aren’t entirely useful to the common drinker, is there a better scale?

“I do think IBUs can be overstated, and therefore can be misleading to the consumer” said Kevin McNerney, co-founder of SweetWater Brewing Co. and brewmaster at Glover Park Brewery.

McNerney suggests an accompanying scale to define hop aroma, but in the end, “What’s in the bottle is most important.”

John Isenhour, Associate Professor of Brewing Science at Kennesaw State University, agrees that the best way to measure a beer’s qualities are with the five senses.

“With taste preferences and abilities all over the map, I'm not sure that IBUs in the current state of craft brewing tells the consumer an awful lot. My advice: just try a sample at the right temperature.”

To the brewer, beer is art, and art cannot be quantified. Treat IBUs like an art critique: a resource for insight and appreciation. But take them with a grain of salt. After all, beauty is in the eye of the beer-holder.

Beer Styles and Their IBU Ranges

Different styles of beer all have different IBU levels and perceived bitterness levels to drinkers. Check out this list of popular beer styles and their respective IBU ranges.

Light Lager: IBUs - 10-20

American Lager: IBUs - 5-10

Wheat Beer/Hefeweizen: IBUs - 10-15

Blonde Ale: IBUs - 15-30

Amber Ale: IBUs - 20-40

India Pale Ale (IPA): IBUs - 40-70

Hazy IPA: IBUs - 30-70

Double IPA: IBUs - 60-100

American Pale Ale: IBUs - 30-50

Imperial Stout: IBUs - 50-90

Belgian Tripel: IBUs- 20-45

Pilsner: IBUs - 25-45

Porter: IBUs - 25-50

Does ABV Affect IBUs?

The short answer is no, alcohol content in a beer does not explicitly impact IBUs. However, when evaluating the bitterness of a beer, it's crucial to consider both the ABV (alcohol by volume) and IBU (international bittering units). A higher ABV can offset the bitterness caused by a high IBU count. The presence of malts in a beer reduces its bitterness by adding sugar content, which raises its sweetness and also increases the alcohol level. As a result, beers with high IBU and high ABV scores should be evaluated in tandem, rather than relying solely on one or the other, to determine their overall taste profile.

Bittering Compounds in Beer and How They Affect Flavor

Chemical compounds in beer contribute to its bitterness and flavor. The brewing process involves preparing barley, breaking it down, and producing wort. Hops are added during boiling to add bitterness and flavor. Alpha acids in hops degrade to form iso-alpha acids, which contribute most of the bitterness. Beta acids provide a harsher bitterness. Both alpha and beta acids have antiseptic properties and affect the beer's shelf life. Essential oils from hops add aroma and flavor, with myrcene, humulene, and caryophyllene being the main oils. Esters, formed through reactions during brewing, contribute fruit-like flavors. Many compounds work together to create the unique taste of beer.

How Fermentation Lowers Bitterness

During fermentation, the perceived bitterness of beer decreases due to various factors. One main reason is the decline in the concentration of iso-alpha acids, which occurs as a result of factors such as their attachment to yeast cells and beer-contact surfaces, precipitation with sediment, and interaction with fermentation foam. Furthermore, the decrease in pH levels during fermentation contributes to a reduced perception of bitterness in the beer.

Bottom Image Courtesy Facebook/Stray Dog Brewing Co.