Tuesday, September 12, 2017

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 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.

Chinook and Nugget hops.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?

Citra and Galaxy Hops.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.

Milled barley and flaked oats.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.

Cheater hops on the right, Cheaper hops on the left.

Cheater Hops

Smell – Similar notes of pineapple and orange, but without an undercurrent of resin. Not an especially amped nose compared recent batches with London III, lacking the oomph of my favorite NEIPAs. Perhaps the malt getting in the way?

Appearance – Identical.

Taste – It has that saturated fancy hop (4-MSP) flavor. Bright, fruity, really juicy. Nice toasty-malty note in the finish, lingering with just a touch of resin. Firm bitterness. The aftertaste is where I really get the Citra-Galaxy rounded tropical fruit compared to the Cheaper hops.

Mouthfeel – Seems slightly crisper, less chalky.

Drinkability & Notes – I’m a sucker for that full fruity flavor with a slight weirdness from the hops. Drinkable and wonderfully hoppy. The hot-side additions of less expensive hops really worked in this batch!

Changes for Next Time – Clearly that early dry hop addition isn’t all about bio-conversion. I’ll be focusing my linalool and geraniol additions at the end of the boil and 4-SMP hops at that early dry hop.

Running the wort into a BrewBucket.Recipe

Batch Size: 5.50 gal
SRM: 3.8
IBU: 78.1
OG: 1.060
FG: 1.016
ABV: 5.8%
Final pH: 4.52
Brewhouse Efficiency: 68%
Boil Time: 60 mins

Fermentables
-----------------
37.6% - 5 lbs Simpsons Golden Promise
22.5% - 3 lbs Rahr 2-row Brewer's Malt
21.1% - 2.8 lbs Quaker Quick Oats
18.8% - 2.5 lbs Weyermann Carafoam

Mash
-------
Mash In - 60 min @ 154F

Hops
-------
1.00 oz Nugget (Pellets, 13.00% AA) @ 15 min
2.00 oz Chinook (Pellets, 13.00% AA) @ Whirlpool 30 min
2.00 oz Nugget (Pellets, 13.00% AA) @ Whirlpool 30 min
1.00 oz Eureka (Pellets, 18.00% AA) @ Whirlpool 30 min

Cheaper Hops Option:
3.00 oz Chinook (Pellets, 13.00% AA) @ Dry Hop Day 2
3.00 oz Nugget (Pellets, 13.00% AA) @ Dry Hop Day 2

Cheater Hops Option:
3.00 oz Galaxy (Pellets, 14.00% AA) @ Dry Hop Day 2
3.00 oz Citra (Pellets, 12.00% AA) @ Dry Hop Day 2

Both
1.50 oz Citra (Pellets, 12.00% AA) @ Keg Hop
1.50 oz Galaxy (Pellets, 14.00% AA) @ Keg Hop

Water
-------
5 g Calcium Chloride @ Mash
4 g Gypsum (Calcium Sulfate) @ Mash
.5 tsp Lactic Acid @ Mash

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

Yeast
-------
SafAle S-04 English Ale

Notes
-------
Scaled to be brewed as either half of the batch.

Brewed 8/6/17 with Collin

Mash pH initially 5.55 pre-acid. Acid brought it down to 5.26. Around 5.4 if it had been cooled.

Whirlpool hops added right at flame-out.

Used ice to get it down to 70F. 5 gallons into each fermentor. Shook to aerate and pitched S-04 directly. Left at 64F to ferment.

Up to ~68F internal by 24 hours.

After two days down to 1.024 (60% AA) added 3 oz Nugget/Chinook to FV1, and 3 oz each Galaxy/Citra to FV2. Fermentation slowing down. Increased ambient temperature to 68F.

8/16/17 Kegged both. ~4 gallons of FV1, 4.5 of FV2. Quad-flushed. 1.5 oz each of Citra and Galaxy in the new screens, weighted with marbles.

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11 comments:

Dave said...

How did you like the stainless hop filter for the keg? Did you tie or weigh it down or just drop it into the keg?

The Mad Fermentationist (Mike) said...

They seemed fine, no complaints so far. I weighed them down with marbles, no tie-off. Not looking forward to cleaning (with the knee-highs I tie the marbles off separately from the hops so I don't have to separate the two). I might eventually go with a solid weight with these.

Ray K said...

What are your thoughts on short 30 minute boils when using hop extract?

My beers always turn out darker than I prefer, perhaps due to longer boiling times.

When using hop extract, all of the hard work has been done already right? Shortening the boil should work.

For my NEIPAs thus far, it is a hop shot @ the beginning of the boil then no kettle hops until flameout.

Your thoughts?

Clint Eaker said...

Timely post! This is exactly in line with what I'm hoping to brew in a week and a half. On your whirlpool hops, do you typically add whirlpool hops at flameout or do you do a partial chill before adding the whirlpool hops?

Jon said...

I'm happy to see the use of S-04 because I'm a cheap lover of dry yeasts (I recently used Nottingham for a NEIPA with decent results). I'm curious if you'd use it again or if you think the other more commonly used NEIPA yeasts are better?
Cheers!

The Mad Fermentationist (Mike) said...

I only partially chill if I'm looking to reduce the IBU contribution. I note the temperature if I do (just kegged a saison that had Chinook and Nugget at 180F for whirlpool followed by Nelson in the fermentor and keg).

This isn't the first time I've used S-04 for a NEIPA. I don't think it "pops" quite as much as 1318, but we're hoping to try some blends and timed-pitches with it to achieve a bit for yeast-hop interaction. On a small-commercial scale dry yeast is so much easier that we're going to try our best to use it!

Anonymous said...

nice post, however i don't think bioconversion is the apropriate term here. it is rather xenobiotic metabolism of yeast cells, than conversion of organic materials into usable products or energy sources by biological processes or agents, such as certain microorganisms.

since, we do not purify the metabolites of the hop compounds from the yeast cells or the medium and use it for industrial or pharmacological purposes, i would call it biotransformation. simple xenobiotic metabolism of yeast cells.

just my two cents

Marco B said...

Most of the bioconversion happens to terpenes extracted on the hot side

Sorry if I missed it, but is there a resource for this? I have been curious for a while on the difference and resulting benefits/caveats between hot and cold applications

The Mad Fermentationist (Mike) said...

Didn't realize "bioconversion" had such a specific meaning, noted.

The growth phase comment was based on this sentence from the first study linked: "Geraniol showed a drastic decrease during the growth phase and a part of geraniol was converted to beta-citronellol by yeast."

Marco B said...

Oops, I was referring to terpene extraction. It is more efficient at a certain temperature?

The Mad Fermentationist (Mike) said...

Hot is almost always more efficient for any sort of extraction, but at the risk of volatilization. Likely differs by terpene. Not something I'm aware of a good source for.