Citra-Galaxy NEIPA: Bioconversion
There has been passionate discussion about hop bioconversion, especially in relation to NEIPA. Studies have shown geraniol in hops like Citra is converted during fermentation into citronellol when there is excess linalool present. But what does this mean for your beer? I talked to Stan Hieronymus when planning an experiment based on his suggestion to use other linalool and geraniol rich hops to mimic Citra. He directed me to a more recent study from the same team that…
There has been passionate discussion about hop bioconversion, especially in relation to NEIPA. Studies have shown geraniol in hops like Citra is converted during fermentation into citronellol when there is excess linalool present. But what does this mean for your beer? I talked to Stan Hieronymus when planning an experiment based on his suggestion to use other linalool and geraniol rich hops to mimic Citra. He directed me to a more recent study from the same team that suggested the thiol 4-MSP (aka 4-MMP) has a synergistic effect with these terpenes. Some hops (e.g., Citra, Centennial) contain linalool, geraniol, and 4-MSP and thus can be used as a single hop to create a fantastic IPA.

The question I set out to answer was whether the same flavors can be achieved piecemeal by adding individual hops to fill in the background flavors and then dry hop with fancy hops to lend varietal character. It is a practical consideration because hops like Citra and Galaxy are in short supply, and often cost four times the price of less-sexy varieties. If we can only get our hands on a couple boxes of Citra for Sapwood Cellars‘ first year, how do we maximize the amount of Citra-forward IPA brewed?

The problem with blindly relying on the science regarding individual compounds is that you can miss the IPA through the hops. I selected Chinook (geraniol), Nugget (linalool), and Eureka (4-MSP). However, each contributes a variety of other aromatics, how would these come through?

Most of the bioconversion happens to terpenes extracted on the hot side, so how important is a mid-fermentation dose of dry hops? At the end of the combined boil I added Chinook, Nugget, and Eureka for the whirlpool. On day two, I dry hopped one fermentor with more Chinook and Nugget and the other with Citra and Galaxy. I then keg-hopped both with Citra/Galaxy in stainless steel hop filters (rather than the nylon knee-highs I’d been using).

I hooked the two kegs up in the kegerator without paying attention to which beer was on which tap. I was able to identify them almost immediately with my first carbonated sample a week later. I thought that was enough to skip the triangle test and go straight to preference. I brought a growler of each to the DC Homebrewer’s August meeting. There were lots of strong opinions (I didn’t tell the homebrewers what I was testing, but asked them to focus on the hop character). With 11 votes to 8, the beer with Citra and Galaxy as the first dry hop addition won, but not by as much as I would have guessed. Here are select comments that each elicited:

Cheaper Hops – Nugget/Chinook: West Coast, spicy, subtle, vegetal, fruitier, aromatic (several), “Galaxy/Mosaic,” more bitter (several), minerally, crisper.

Cheater Hops – Citra/Galaxy: Piney, fruity, juicy, berry, fresh orange, hoppier, sweeter, restrained, rounder, more dry hop, more aromatic.

These results were of the beers after less than two weeks in the keg. While freshness is essential for NEIPA given their sensitivity to oxygen, a little extra time post-fermentation can be beneficial. I’ve gotten a few emails from brewers disappointed with the “juiciness” of their beer a few days after kegging. It often takes time for the yeast (which is coated in hop compounds) and lupulin to settle out and clear the way for those juicy flavors. In this case I also found the extraction of the keg hops took a couple weeks, with the Cheaper Hop half tasting more like Citra and Galaxy now a month after kegging.

I think this experiment contradicts the old adage that dry hopping only effects aroma. Flavor and aroma are inextricably linked. Dry hopping can even decrease IBUs, or it can add bitterness depending on how much iso-alpha is in the beer already. There are few simple rules in brewing!

For my tastes too much maltiness distracts from the hops in NEIPAs. I don’t care for the full Maris Otter crackery flavor that some examples have. For this batch I started with a similar malt bill to my previous NEIPA, but subbed in Golden Promise for about 2/3 of the base malt. Golden Promise is softer than some of the other British base malts, and I thought it worked well here to increase the perception of maltiness without distracting.

Cheaper Hops

Smell – Nice mix of bright citrus juice (orange) and more classic Pacific-Northwest hop-bag resin. Has some of that bold Citra/Galaxy tropical, but it is a component rather than a feature. Toasty notes, nice depth addition from the Golden Promise.

Appearance – Maximum haze without muddiness. Slightly darker than some of my previous batches, which likely increases the appearance of haze. Nice head, but retention isn’t remarkable.

Taste – Falls a little short of full-on NEIPA, lacking that wonderful saturated juicy hop flavor. Although the fullness of the hop character has increased while sitting on the keg hops. Pineapple, orange candy, and dank. Slightly sharp bitterness, a bit lupulin bite in the throat.

Mouthfeel – Smooth, but a little chalky in the finish.

Drinkability & Notes – A nice solid NEIPA with some character that might appeal to the cross-over West Coast drinker. Certainly nice to be able to get that good an IPA from 2/3 inexpensive hops, but it isn’t fooling anyone.

Calcium	Chloride	Sulfate	Sodium	Magnesium	Carbonate
90	90	90	10	5	45

Source: The Mad Fermentationist

Citra-Galaxy NEIPA: Bioconversion