Hop Creep
Let’s Get Creepy!
A homebrewer’s guide to understanding and managing hop creep
By Tim Murray
This beer has diacetyl. These four words, to any homebrewer, are a dagger. They conjure up insecurities and feelings of failure. Imagine watching someone go through the five stages of grief in less than 30 seconds. That’s what it’s like watching a brewer hear these four words. It can be horrifying.
Now, imagine what it’s like to hear Vinnie Cilurzo, Owner and Brewmaster at Russian River Brewing Company (and brewing legend), say these four words...to you. I witnessed such a horror at a recent meeting of my fellow homebrewers from the Diablo Order of Zymiracle Enthusiasts (“DOZE”) homebrew club. The brewer, who actually just won a medal at the National Homebrew Competition, was mortified! But, there was a silver lining for all of us. First, Vinnie was at our homebrew club meeting - a true definition of these being crazy times. Second, it got Vinnie on the topic of hop creep.
It turns out, Vinnie, amongst other professional brewers and a few academics, have put a lot of time, money and other resources into understanding the concept of hop creep. Vinnie is so passionate about the topic he was willing to come to another DOZE meeting and spend a considerable amount of time educating us on the topic. The remainder of this article focuses on the key points of that presentation, with an emphasis on the practical implications for homebrewers. So without further ado, let’s get creepy.
What in the world is hop creep? Simply speaking, hop creep is the restart of fermentation during the dry hopping phase of an otherwise finished beer. During dry hopping, enzymes associated with the hops begin breaking down unfermentable dextrins left behind after primary fermentation. Any remaining yeast in the finished beer can metabolize these newly liberated sugars, producing alcohol and CO2. It’s a little like bottle conditioning your beer, only instead of the brewer adding the priming sugar, the dry hops are doing it for them.
Table 1: Beer attributes impacted by hop creep and the level of importance to homebrewers.
Before we jump right to managing hop creep, let’s discuss some of the factors that influence hop creep. To restate the obvious, hop creep only occurs if you dry hop your beer. For a more detailed look at dry hopping techniques, check out this article [Dry hopping]. Many of the dry hopping factors that impact flavor and aroma also impact hop creep:
Time: the longer the hops mingle with the beer, the more their enzymes will break down the dextrins left behind by primary fermentation. In turn, active yeast will convert these sugars to alcohol, CO2 and other chemical bi-products, some of which are bad (e.g., the precursor responsible for diacetyl).
Temperature: higher temperatures, generally, lead to higher levels of fermentation activity by yeast. These warmer temperatures may also coax sleepier, less healthy yeast cells back into fermentation mode.
Hopping Rate: more hops equals more enzymes to break down the dextrins. Pretty simple.
Hop Format: hops come in several formats including whole cones, pellets, powders, liquid extracts, etc. Interestingly, studies on hop creep have identified that most of the dextrin seeking enzymes reside in the leafy, vegetal, portion of the hop cone. So logically, the more leafy components that make it into the beer, the greater the potential for hop creep.
Hop Processing: before hops are distributed to brewers they go through a process of dehydration or ‘kilning’. This process keeps the hops from spoiling during distribution and storage. It involves the application of heat to the hops for a period of time. If the heat is high enough, and applied for the correct amount of time, most of the enzymes responsible for hop creep will be denatured. The primary argument against higher kilning temperatures is the potential loss of oils that can volatilize at higher temperatures.
Hop Variety: just like the fact that different hop varieties have different levels and compositions of oils, enzymatic activity varies from hop variety to hop variety.
The Beer Itself: dry hopping a beer with a high amount of residual sugar in time will produce more fermentable sugars from hop creep. In other words, an IPA that finishes primary fermentation at 1.010 specific gravity would have a lower potential for hop creep than one that finishes at 1.020, all else being equal.
Remedies That Can Help Reduce (Not Eliminate!) Hop Creep
By now we have a reasonable understanding of hop creep - what it is, the havoc it can wreak on our beer, and some of the factors that determine its level of intensity. Let’s now consider some of the potential strategies that homebrewers can use to help reduce hop creep.