You may have noticed some of the obvious high IBU beers on the list, like the American IPA or Double IPA. What usually comes as some surprise is the high IBU count on some of the sweeter beers, not associated with a hoppy bitter flavor, like American Barley Wine. For those of you not familiar with this beer style, it is known for its malty sweetness with caramel or toffee-like aroma, not bitterness. So why do some beers have high IBUs, but don’t taste bitter? This is due to what is called “perceived bitterness.”
What is perceived bitterness, and why is it important?
Perceived bitterness is the bitterness we actually taste. This is complex as the bitterness level tasted changes by the individual and sweetness. The IBU scale is not based on perceived bitterness but the iso-alpha acids present. Hops are just one ingredient in beer, and the bitterness they provide can be masked by other flavors in the beer, like malt, which is sweet. For this reason, looking at the IBU number alone doesn’t always help identify how bitter a beer will taste.
As the beer’s malt profile increases so do the amounts of residual sweetness in the beer. This sweetness balances out the bittering acids, making it taste, well, less bitter. Think of this like a cup of black coffee. Black coffee can be perceived as bitter; as you add sugar, it balances out the bitterness. The coffee still contains the original level of bitterness; it’s now just masked by the sugar’s sweetness. This concept is why an American Pale Ale with 40 IBUs and a minimal malt character taste significantly more bitter than an Oatmeal Stout with 40 IBUs and a higher malt profile.
Now that we covered the basics of IBU, we know that its scale can be used as a general guideline to gauge a beer’s potential hoppiness or bitterness. We also know that we must take the beer’s style into account, as other flavors can enhance or mask the bitterness level in both directions. We hope this helps, and please put any questions you may have in the comment section below.