As a taster, it’s important to know that compared with sour or salty, bitterness is slow to affect our palates. The first two are very simple chemical phenomena and require only the simplest of cellular mechanisms to fire off their signals to the brain. Bitterness, like sweetness and umami, requires an intermediate molecule, something called a G-coupled protein. It takes a little longer to do its thing, and this time dimension of tasting is something that you always need to pay attention to.
If you taste a moderately bitter beer of, say, 40 IBUs against the same beer spiked with perhaps triple that, the first 10 seconds will feel exactly the same. It takes a while for the bitterness to grow on your tongue, and it will build and build for nearly a minute. You almost have to watch the clock as you try this and force yourself to pay attention for far longer than you are probably accustomed. I recently sat in a room full of people as we blindly tasted two otherwise identical beers of 40 and 130 IBUs without an upfront explanation and watched close to half the room fail to tell them apart. It’s harder than you think.
That bitterness provides a bit of roller-coaster experience as it clack-clack-clacks its way up to the maximum, then lingers a moment and begins the long glide down. All that time, other beer flavors are weaving in and out: acidity up front, then sweetness and any astringency weaving together with the bitterness, pleasantly or otherwise. You have probably noticed that bitterness really blasts your palate, so after a massively hoppy beer or two, it may take a while for your palate to recover.
It’s also important to separate hop aromas from the pure bitterness on your tongue. Although they are caused by entirely different chemicals and distinct systems of sensory cells, aroma and taste do not live in entirely separate silos in our brains, so it takes some effort to pull them apart. In another torture test, judges were blindly given similarly bittered beers spiked with different levels of hop aroma oils, and most of us mistook the enhanced aroma for added bitterness.
Even trained tasters have some difficulty identifying a specific level of bitterness. Our accuracy in this task may be no better than about 20 percent, so a 40 IBU and 50 IBU taste pretty much the same. In addition, many of the IBU levels printed on beer labels are based on a brewery’s calculations rather than an actual analysis, and those may be off by an equally wide margin. The other thing to keep in mind is that the bitterness is always in context with the rest of a beer, so if you compare two equally hopped beers, the one with a lot of maltiness may seem a good deal less bitter that the one without. Brewers know this when seeking balance in their recipes. We tasters should be aware of this as well and be wary of relying on numbers to tell us how we should feel about any given beer.
Bitterness in beer comes from five hop chemicals known as alpha acids, which are extracted and chemically transformed, or isomerized, by the heat of boiling. All hops produce a similar bitter sensation, albeit in varying degrees. However, those with a higher proportion of one alpha acid, cohumulone, are reputed to have a coarser bitterness, although this is hotly debated. When offered to the market, the bittering power of hops is stated in an analysis that is a simple percentage of alpha acids, with values ranging from about 2 percent to 20 percent.
In theory, hops used purely for bittering should all taste about the same after their unique oil profiles are blown away by the hour of vigorous boiling typical of a brew. Brewers have a hunch that’s not the case and typically choose bittering hops that complement the character of their aroma hops. However, I recently specified 80 IBUs of Cluster hops, an old American heritage variety infamous for coarse flavors, and the beer turned out quite delicious once some fine aroma hops were added late in the boil. So the theory may be true, or not.
As we creative brewers engage in a bitterness arms race, we are starting to run up against real limits. The solubility of hops decreases as the concentration increases, making it difficult to reach super-high levels, especially with the high price of hops these days. Common wisdom in the industry once held that 100 IBUs was pretty much the max, but some recent beer analyses have come in well beyond that. However, there is some debate about the linearity of the common assays used and what they are actually detecting way up at the high end of the scale. We can safely say that there will never be a 1,000 IBU beer, although I know people who are probably trying. It’s also an open question about what the upper level for our taste buds might be. Above a certain level, more hop bitterness simply might not be tasteable.
Whether you’re a raging hophead or one who prefers a more balanced approach, bitterness is a valued flavor component that contributes to beer’s unique charms. Bitterness quenches thirst, brings balance, tames rich foods and just flat-out tastes great in beer. As you raise that next glass of IPA, you might whisper a quiet toast: Here’s to the power of subverting our inner fears to more pleasurable ends.
This column appears in the July 2014 issue of All About Beer Magazine. Click here for a free trial of our next issue.