Comparing Dry-Hopping vs. Hopzoil™ Additions

Guest Blogger: Adam Paugh

Technical Brewing Director – Glacier Hops Ranch, Inc

Technical Abstract  

We’ve been comparing split batch A/B testing of a traditional dry-hopping method vs. Hopzoil™ post-fermentation treatment, with some interesting results I would like to share.

What we have created for ourselves is a fascinating stack of questions to which the answers will be the focus of ongoing testing and research. Of primary focus in our initial test batches was to determine basic differences in the flavor and aroma profiles of two finished beers. Continued testing will seek to study measured changes in IBUs and hop flavor due to CO2 scrubbing, reduction of hop flavor and aroma due to introduced oxygen and degree of turbidity in final packaging. We speculate that most traditional dry hopping techniques introduce both oxygenation and nucleation sites into a closed system.


The bane of many a commercial brewery’s existence, post-fermentation oxidation is known to have a negative impact on overall flavor stability of beer, reducing shelf-life and leading to profit losses. Brewers go to great lengths using myriad methods to reduce oxygen ingress at packaging, believing that doing so will extend the freshness of their beer and preserve the hop character.

So how and when is oxygen going to be introduced into your beer after fermentation finishes? There are two principle ways so long as you are using proper brewing equipment and not aging for long periods of time.  The first potential culprit for O2 ingression is from racking. For the second, brewers have created some highly inventive devices to deliver their dry hops to their fermenters in an oxygen free system. The “hop cannon or Sierra Nevada’s hop torpedo”, are two such devices that will shoot the pellets into the fermenter via CO2. Other procedures involve dry hopping in the fermenter just short of final gravity so the still active yeast will consume the remnants of any remaining O2 in the hops themselves.

IBU’S and Hop Flavor

I have recently read that Sierra Nevada begins dry hopping when the gravity is within 1-2 degrees Plato of target FG. The yeast is still active, so that CO2 dispersed from yeast can push out any oxygen within the hops. The addition of hop oils when measuring final gravity may not alter the gravity of the beer, as oil does not congregate with water and CO2.

What else is moving the dials? We know that yeast creates biotransformation of hops flavors.

The constant nucleation from fermentation scrubs away some of the hop aromas that you are trying to achieve. Some brewers, on the other hand, adds hops during fermentation, and the hardware garnered for these hop-forward beers should make any brewer re-think their approach. There are three purported reasons for this method:

This is to take advantage of the active yeast for (1) dissolved oxygen protection (2) natural mixing which we believe helps in better extraction of wanted oils and (3) biotransformation of hop oil compounds.”


We speculate that traditional dry hopping methodologies introduce two potential unwanted factors into the closed fermentation process: oxygen and additional nucleation sites in solution.

On the whole, oxygen in the post fermentation brewing process is an unwanted element. Brewers take great lengths to mitigate the re-introduction of oxygen during fermentation, racking/transferring and packaging.  Given a simple in-line injection system, Hopzoil™ being de-void of harbored carrier oxygen would prohibit this introduction. The re-introduction of oxygen post-fermentation may also be responsible for unwanted additional fermentation and yeast attenuation to commence during biotransformation of yeast left in suspension.

Hop pellets used for dry hopping break apart immediately and provide thousands of nucleation sites for CO2 to attach and come out of solution. We know this process as “CO2 stripping”. CO2 strips both hop bitterness and flavor out of solution during exit into the atmosphere.

Hopzoil being a non-vegetative material, completely dissolves in solution without the late introduction of additional nucleation sites during the post-fermentation process. This negates concerns of CO2 scrubbing of hop bitterness, flavor and aroma during the effort to achieve additional hop character in the beer.

In the end, both the experienced and novice brewer needs only to monitor specific gravity of the fermenting beer. Once the FG has been achieved, an appropriate dosage of Hopzoil will provide the need additional ‘dry hop’ aroma without concerns of changes in attenuation and oxygenation outlining during the traditional dry hopping procedure. The brewer can essentially ‘freeze the beer in time’ from the period end of fermentation to packaging.