Author: Brian Hall

Aroma is one of the first things noticed when enjoying a beer. Brewers of hoppy beers have long sought to pack as much flavor and aroma into their product, which they try to protect by whatever means necessary. When it comes to the New England IPA, a massive hop aroma is a signature characteristic of the style, some would say more so than any other component.

Freshness, hop layering, and minimization of oxygen ingress are considered to be imperative to achieving quality aromatic characteristics in IPA, particularly those of the New England variety. Some paranoid brewers worry that CO2 blowoff can lead to decreased hop aroma, an issue of particular concern when it comes to kegging beer. Brewers looking to limit post-packaging oxygen exposure have long been known to purge the headspace of their fill kegs of oxygen by hitting it with CO2 and relieving the pressure multiple times. While advocates laud this method for its ability to reduce oxygen ingress, many also claim sacred aromatic compounds leave the keg during the purging process as well, meaning they don’t end up in the drinkers glass.

Having brewed many batches of NEIPA over the last few years, I’d never worried much about massive aroma loss due to purging my kegs and tend to purge 6 times for each beer. However, when a reader recently commented they felt they were losing hop aroma from such a process, I was inspired to put it to the test.

| PURPOSE |

To evaluated the differences between a New England IPA that had the headspace in the keg purged multiple times with CO2 and one where the headspace was not purged.

| METHODS |

I went with a NEIPA for this xBmt due to the supposed sensitivity to oxidation of this style.

The First Purge

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 32.9 IBUs 5.8 SRM 1.062 1.018 5.9 % Actuals 1.062 1.016 6.1 % Fermentables Name Amount % Lamonta American-style Pale Malt (Mecca Grade) 9 lbs 67.92 Oats, Malted (Thomas Fawcett) 3 lbs 22.64 Vanora Vienna-style Malt (Mecca Grade) 1.25 lbs 9.44 Hops Name Amount Time Use Form Alpha % Magnum 7 g 60 min Boil Pellet 12 Citra 28 g 5 min Boil Pellet 12 Enigma 28 g 5 min Boil Pellet 16.5 Citra 43 g 1 min Boil Pellet 12 Enigma 43 g 1 min Boil Pellet 16.5 Citra 57 g 6 days Dry Hop Pellet 12 Enigma 57 g 6 days Dry Hop Pellet 16.5 Notes Water Profile: Ca 117 | Mg 3 | Na 10 | SO4 84 | Cl 168 Download Download this recipe's BeerXML file

I started my brew day by collecting the full volume of water for two 5 gallon batches in a single kettle, adjusting it to my desired profile, then hitting it with my heat stick.

With the water heating up, I weighed out two identical sets of grain.

I returned a couple hours later to heated water and milled the grain.

Using the full volume BIAB method, there wasn’t room for a 10 gallon/38 liter batch in my 15 gallon kettle, so I brewed two batches of wort that would later be combined. With the water appropriately heated, I stirred the grains in and checked to make sure both were at the same mash temperature.

Each mash was left alone for 60 minutes before I removed the grain bags and let them drip until the same pre-boil volume was reached.

I then combined the worts in a single kettle.

While the wort was heating, I measured out the kettle hops.

The wort was boiled for 60 minutes with hops added at the times stated in the recipe.

At the end of the boil, I quickly chilled the wort to my desired fermentation temperature.

A hydrometer measurement showed I hit my expected OG dead nuts.

After racking identical volumes of wort to separate Brew Buckets, I pitched a pack of Imperial Yeast A38 Juice into each batch.

Each beer was then hit with an equal dose of pure oxygen before being placed in my fermentation chamber set to 66°F/19°C. I let the beers ferment for 24 hours before returning to add the dry hop charge, at which point both were at high kräusen.

The beers were left alone to finish fermenting. Hydrometer measurements a couple weeks later showed both had reached the same FG.

The warm beers were racked to CO2 purged kegs that were placed in my keezer. I hit one of the kegs with CO2 a total of 8 times, purging between each delicious smelling dose before keeping the gas attached at high pressure for burst carbonation. For the other batch, I attached the high pressure gas and left it alone.

I returned the following day to reduced the pressure in both kegs, meaning the non-purged batch did get a single small purge. The beers were left to cold condition for another week before they were ready for data collection.

| RESULTS |

A total of 16 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the beer served from a purged keg and 2 samples of the beer served from a non-purged keg in different colored opaque cups then asked to identify the unique sample. At this sample size, 9 tasters (p<0.05) would have had to identify the unique sample in order to reach statistical significance, though only 4 (p=0.83) made the correct selection, indicating participants in this xBmt could not reliably distinguish beers served from either a keg purged 8 times after packaging or one that was not purged.

My Impressions: I couldn’t tell a difference at all between these beers and guessed on the 3 triangle tests I attempted, out of which I happened to choose the odd-beer-out once. With my knowledge of the variable, I focused intensely on aromatic differences between the beers and noticed none, they smelled and tasted identical. For anyone looking for a NEIPA recipe, this is my all time favorite so far, likely due to the reasonable amount of hops I used!

| DISCUSSION |

The idea that aroma could be lost during the keg purging process seems reasonable on the surface– anyone who has ever purged a keg of hoppy beer is well aware of how heavenly it smells. However, the amount of gas that actually ends up escaping the keg is pretty damn small, to the point of seeming inconsequential, despite how good it might smell. And the results from this xBmt showing tasters could not reliably distinguish NEIPAs served from either a keg that was purged multiple times or one that was not purged suggests the practice may not make all that big of a difference.

It’s likely brewers of hyper-hoppy, oxygen sensitive beers experience some internal conflict when it comes to packaging their product– purge to eliminate oxygen and risk losing some aroma, or keep all the aroma in the keg and risk oxidation? Given these findings, I’m compelled to think that purging the headspace is likely more beneficial than harmful, particularly for those unable to pre-purge their kegs of oxygen.

The specific purpose of this xBmt was to evaluate if purging a filled keg had a noticeable impact on aroma, hence the decision to rack the beers into kegs that had already been purged with CO2. Given how sensitive NEIPA seems to be to oxygen, and with data suggesting purging doesn’t seem to reduce aroma, I’m interested in whether or not a beer racked to a keg that hasn’t been pre-purged of oxygen might benefit from purging the headspace of the filled keg with CO2. Does bottom filling a non-purged keg force oxygen out, leaving it only in the headspace, which can then be purged? Add it to the list!

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

Support Brülosophy In Style!

All designs are available in various colors and sizes on Amazon!

Follow Brülosophy on:

If you enjoy this stuff and feel compelled to support Brulosophy.com, please check out the Support page for details on how you can very easily do so. Thanks!

Advertisements

Share this: Facebook

Twitter

Pinterest

Tumblr

Email



Like this: Like Loading...