exBEERiment | Impact Gas Hopping Has On A Blonde Ale

Author: Alex Shanks-Abel

Two competing demands have grown over the last couple decades in brewing – hop flavor and sustainability. Unsurprisingly, the need for more hops requires increased agricultural resources such as land, water, fertilizer, and so on. The impact goes beyond the hop fields, however. Large dry hop doses also reduce efficiency in the brewhouse, as hop pellets absorb more than ten times their weight in beer, which amounts to around 1 gallon per pound of dry hops in standard a 5-gallon batch.

Researchers at the Berlin Institute of Technology proposed a method to transfer dry hop aroma into beer without adding dry hop matter. By heating a sealed vessel of hops infused in an aqueous solution, a temperature gradient is created that causes hop compounds from the hops to volatilize and rest in the headspace; this hop saturated gas then gets pushed out of that vessel in a closed system into the bottom of a vessel containing beer such that it bubbles up and absorbs into the beer. Not only does this reduce beer loss, but it prevents the hops from adding undesired polyphenols and diastatic enzymes.

I can’t say I’ve ever tasted a gas hopped beer, much less brewed one myself. However, I’m keen to employ any brewing method that can save me a few liters of beer while reducing the risk of issues like hop creep and polyphenol extraction, especially when it involves a convolutedly fun setup. Curious of the impact this unique gas hopping method might have on a beer, I designed an xBmt to test it out!

NOTE: There appears to be little consensus on best practices when it comes to gas hopping, with some brewers preferring to keep the hops dry in the initial vessel, while others opt for the aqueous solution as was done in this xBmt, a technique that has also been referred to as liquid-to-gas-to-liquid (LGL) flavor transfer. For the purposes of this article, and until we receive further clarification, we’re viewing both options as different gas hopping approaches. 

| PURPOSE |

To evaluate the differences between a Blonde Ale that was gas hopped and one that was not gas hopped.

| METHODS |

For this xBmt, I went with a simple Blonde Ale recipe with the hope that any differences caused by the variable would be easily noticeable.

Patience, Young Gas Hopper

After collecting identical volumes of water in separate kettles, adjusting each to the same mineral profile, and flipping the switches on my controllers to get them heating up, I weighed out and milled the grains.

Once the waters were heated, I incorporated the grains then checked to ensure they were at the same target mash temperature.

While the mashes were resting, I prepared the kettle hop additions.

Once each 60 minute mash was complete, I removed the grains then boiled the worts for 60 minutes before chilling them and taking refractometer readings showing they were at the same OG.

After transferring identical volumes of wort from each batch to sanitized fermentation kegs, they both received a pouch of Imperial Yeast A07 Flagship.

Following 2 weeks of fermentation at 68°F/20°C, I took hydrometer measurements showing the beers were at the same FG.

With fermentation complete, I cold-crashed the beers overnight then pressure transferred each to CO2 purged serving kegs that were placed in my keezer and left alone for a few days. At this point, I prepared for gas hopping by using a heat-stick to heat up a water batch in a spare cooler. While waiting on that, I filled a sanitized keg with RO water then added the hops before sealing it and placing it in the hot water bath where it was left until it reached 147˚F/64˚C.

I then connected a line from the gas post on the gas hop keg to the liquid post on the beer keg, as well as from the liquid post on the gas hop keg to the gas post on the beer keg – a completely closed system where the pressure built-up in the gas hop keg from being heated pushed the hoppy gas in the headspace to the bottom of the beer keg such that the it travelled up through the beer.

After letting this run for 120 minutes, I disconnected the gas hop keg from the beer keg and placed both filled beer kegs on gas in my keezer where they were left for 3 weeks before they were ready to serve to tasters.

| RESULTS |

A total of 19 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the beer made using the gas hopping method and 2 samples of the beer that were not gas hopped in different colored opaque cups then asked to identify the unique sample. While 11 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 6 did (p=0.65), indicating participants in this xBmt were unable to reliably distinguish a Blonde Ale that was gas hopped from one that was not gas hopped.

My Impressions: Out of the 5 semi-blind triangle tests I attempted, I correctly identified the odd-beer-out ever time. Although the flavor of the beers were identical to my senses, I felt the gas hopped batch smelled like the bottom of a bag of Citra that was absent in the one made without using this technique. Given the similarities in flavor and the fact the gas hopped beer’s aroma was incongruous with its flavor, my preference was for the non-gas hopped version.

| DISCUSSION |

There’s no denying that modern beer drinkers love hops, and this has led to the development of various methods for imparting beer with the most pungent hop character possible. One such method that hasn’t received much attention is gas hopping that, simply put, involves bubbling hop saturated gas through finished beer in place of dry hopping, thus reducing the risk of polyphenols and hop creep while increasing yield. Interestingly, tasters in this xBmt were unable to reliably distinguish a Blonde Ale that was gas hopped from one that was not gas hopped.

Blonde Ale being a fairly neutral canvas for experimenting with, it seems unlikely other characteristics of this beer distracted tasters from being able to tell them apart. One possible explanation for this result could be that participants were more focused on flavor differences than they were on aroma differences, as gas hopping was designed primarily to emphasize the latter. It’s also possible that my own semi-blind triangle test performance was just a fluke and that there really wasn’t much of a perceptible difference between these beers.

Going into this xBmt, I was optimistic that gas hopping would have a meaningful effect, and when I was able to consistently tell the beers apart, my optimism was validated. Then I saw the blind taster data and I was a bit stumped – not even a full one-third of tasters identified the unique sample in the triangle test. What gives? Either way, despite my preference for the beer that was not gas hopped in this xBmt, I’m now more curious than ever to see how this technique works on a hoppy style and I look forward to exploring it more in the future.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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