It’s no secret that when brewers try Low Oxygen Brewing, one of the main things the comment on is how the hops seems to “pop” or have more presence than in previous versions of the same beer. They have a certain brightness and clarity of bitterness, aroma and flavor. This isn’t specific to dry hops either, as there is a “clarity” (actually being able to smell and taste delicate nuances) to a 60 minute bittering addition, and anything later than a 30 minute addition typically adds too much hop flavor for a beer like a Pilsner. But why is that? What does Low Oxygen Brewing bring, specifically, that would affect hop character? Lets talk about it.
Let’s go back to the fundamental building blocks of what we are trying to do, i.e. lower dissolved oxygen on the Hot and Cold sides and limit thermal stress on our wort. This doesn’t need to be long and drawn out discussion, as the concepts will seem pretty obvious after a short discussion. In fact, this discussion goes hand in hand with one of our most talked about attributes: lingering fresh grain flavor.
Where does the lingering fresh flavor come from? Well, we know it comes from natural antioxidants inherent in the grain, things like AAO (Ascorbic Acid Oxidase, etc.). We know that removing oxygen from the Hot and Cold side of our process allows us to preserve, and taste in the final beer, these desirable fresh grain flavors.. Why would hop character be different? Hops have notable antioxidant properties, as well as polyphenols. In professional German brewing textbooks they talk about using hops in the mash to reduce HSA (Hot Side Aeration), so it’s certainly not a secret. At this point, you may be saying to yourself:
“Wait. Don’t we add hops (mostly) to boiling wort? Doesn’t that wort hold little to no oxygen? How are we oxidizing hops doing that?”
In reality, we may not actually be oxidizing the hops during this stage in the process. Processes immediately downstream of the boil are our likely culprit, and we need to discuss those stages in the cool down phase and Cold side of our process to fully understand the impacts.
We already know the benefits of a nice soft boil, trub seperation, and spunding. However, we focus so much on those topics as they relate to fresh lingering grain flavors, that we tend to forget about what it does to hop character. Excluding dissolved oxygen helps preserve fresh lingering grain by preserving natural malt antioxidants. Those same processes preserve natural hop antioxidants as well, thereby preserving hop aroma, flavor, and overall presence concurrent with fresh grain flavors. Let’s briefly discuss some of the major bullet points associated with this concept:
- Soft Boil with Proper pH – This ensure help don’t “over extract” hop substances, specifically vegetal or raw hop flavors
- Trub Seperation – Oxidation can occur without the presence of oxygen. This can happen in a number of ways, but trub (Specifically hot break) is a VERY large contributor. Essentially, you could every molecule of oxygen from your beer (obviously not possible) and still have oxidized beer. Oxidation without molecular oxygen is largely driven by melanoidins and polyphenols, the latter which we know the hops possess.
- Spunding for Carbonation – This shouldn’t warrant discussion at this point, but CSA (Cold Side Aeration) is paramount in all beer making. One thing ALL brewers can agree on is the limiting of oxygen in all stages of the cold side of the process.
In closing, we have one very important takeaway: The better you are at limiting oxidation Hot and Cold side of the process, the better, more vibrant, and characterful your beers hop profile will be. If you are not oxidizing natural hop antioxidants, which most likely contain highly volatile flavors they are normally evaporated, they are staying in the beer, just like similar grain flavors we strive so hard to retain. But don’t just take my word for it. It was just part of this discussion on the MBAA (Master Brewers Association of the Americas) forum, where a very large and notable East coast brewery had this to say: