Balancing Bitterness in Gluten-Free Beers
The latest topic in our series on gluten-free beer and brewing is the IBU scale. Really, it’s not a topic exclusive to gluten-free brewing, but an important brewing topic with some subtleties to consider when you’re brewing gluten-free. Let’s start with the basics. Bitterness is an important part of the flavor of beer. We’ve talked previously about bitterness as one of the five basic tastes along with sour, sweet, salty and umami. In beer, bitterness is generally used to offset sweetness from residual sugar.
Bitterness is more important to the flavor profile of some beer styles than others. An IPA should be more bitter than a brown ale. Most bitterness in beer comes from hops and, as we discussed in an earlier post, it is often measured in terms of International Bitterness Units (IBUs). However, some bitterness can come from roasted grains or other ingredients, such as cacao nibs or coffee additions. The IBU rating measures the concentration of alpha acids in your beer in units of parts per million. A higher IBU rating generally corresponds to increased bitterness.
Different styles of beers have different guidelines for target IBU ratings. When developing a recipe, you can estimate your IBU’s to help match style guidelines. We’ll skip over the math in this post, but for those interested in digging into the details, this post from John Palmer does a nice job.
The inputs for calculating IBU’s include the weight of hops being added, the length of time the hops are boiled, the alpha acid content of the hops, and the gravity of your wort. Most of the inputs can be measured directly by the brewer with the exception of alpha acid content. If you are brewing with hop pellets, the alpha acid content is generally printed on the packaging.
While the IBU rating is useful for recipe development, it has several limitations. First, the IBU scale isn’t strictly linear (i.e. a 100 IBU beer will not necessarily taste twice as bitter as a 50 IBU beer). Additionally, there is an upper limit to how much alpha acid can be dissolved in a wort. I’m sure some of you hop lovers out there are already thinking “I’m going to brew a 10,000 IBU beer.” Sadly, the maximum achievable IBU rating is about 110 IBU before the wort becomes saturated. The biggest limitation to the IBU rating, however, is that it doesn’t actually do that great of a job of describing bitterness.
While it’s true that a higher IBU rating corresponds to a greater concentration of alpha acids, the actual perceived bitterness can vary widely. There are numerous other factors that need to be considered including the types of grains used in the grain bill, mash temperatures, wort gravity, and yeast strain, to name a few. Suppose we brewed two beers, both with a 100 IBU rating. The first beer is a simple, low gravity brew made with 100% pale malt. The second is a high gravity brew with lots of roasted grains and crystal malt. They both have the same IBU rating, but the first beer will most likely taste much more bitter because it’s not as balanced.
At the beginning, we mentioned that there are some subtleties to consider when brewing gluten-free. Let’s tie it all together. Gluten-free grains like millet, buckwheat, quinoa, amaranth, etc. have a different flavor profile than malted barley. The perceived bitterness in a gluten-free beer can be higher than that of an equivalent barley-based beer with the same IBU rating, but this is not a hard and fast rule. Style guidelines and target IBU ratings were all developed for barley-based beers so it’s important to make adjustments when brewing gluten-free. In our experience, following the target IBU ratings for a barley-based beer style can result in a beer that is perceived as slightly more bitter than the IBU calculation would suggest. To put it another way, we’ve found that it works best to adjust the target IBU rating downwards when trying to replicate a barley-based beer style. All this being said, as more gluten-free roasted and specialty grains become available, we anticipate that there will be more and more exceptions to this rule. The best approach is to let your palate be your guide, experiment, and drink some beer!