Centennial IPA: The Myrcene Hypothesis

I have a bit of a love-hate relationship with the classic “C” hops. At their best, hops like Cascade and Centennial can lend complex floral aromas and ripe orange, lemon, and grapefruit flavours when used on the hot side. Where it gets complicated for me is the dry hop characteristics. Those beautiful flavours from the boil can be overwhelmed by an unpleasant herbal aroma that I can only describe as the pith of an orange, but with none of the pleasant zest. I’ve often struggled to describe it because it’s not that often that I eat just the pith of an orange! This post is a deep dive into the that weird aroma using an experimental Centennial IPA.

Because of this noted dry hopping downside I’ve tended to stay away from using these hops post boil. I’ve often wondered why I didn’t hear about it from others too – am I the only person that perceives this unpleasant flavour? One thing I’ve learned in tasting beer is that everyone has their own unique tasting abilities and preferences. Maybe I’m just in a small minority that’s offended by this stuff.

Centennial IPA Experiment

I decided to investigate a little further with an experimental brew. Conveniently I had 12 ounces of Centennial in the freezer, and I could hear it calling out to be used in a big IPA recipe. The main idea for this beer would be to test the hypothesis that the herbal aroma is connected to the dry hop. I had good reason to believe it was based on past experience. And while I don’t necessarily blame myrcene alone, it seems like a prime suspect given it’s common descriptors (spicy, herbal) and significant fraction of the oil in Centennial (up to 65%). Myrcene is also in the “hydrocarbon” family, and is extremely volatile. This means it’s unlikely to survive the boiling and fermentation processes, and dry hopping is the most likely source in beer.

To confirm the source of the offending aroma, I would limit hopping to the kettle only – at least at the start. I later realized that dry hopping cold in the serving keg could help further pinpoint the exact source.

Centennial IPA Brew Day Breakdown

I wanted to keep the malt bill simple and familiar, so I used a grist of 2-row with 2.5% crystal 120. It’s a single infusion brew-in-a-bag recipe using a similar wort production process as the Easy Ale recipe.

ItemNotes
24 L brewing waterInclude: 8.0 g gypsum, 3.5 g calcium chloride, 17 g of 25% phosphoric acid
6.0 kg base maltPrairie Malt 2-row
0.1 kg crystal malt C120
Target volume~19 L (5 gal.) into the fermenter
Target OG~1.067 @ 70% efficiency
Mash styleSingle infusion, brew-in-a-bag
Mash temperature/time147 F (63.9 C) for 45 minutes

Water profile

The brewing water profile is heavier on sulphate, and more “minerally” overall than the Easy Ale. With the higher overall bitterness of this beer I feel it stays in balance.

CalciumSulphateSodiumChlorideResidual alkalinitysulphate:chloride ratio
135 ppm187 ppm2 ppm95 ppm-932.0

Kettle hopping strategy

The hopping is where this beer really diverges from the Easy Ale. With 12 ounces of Centennial, and all of it going in the kettle, the bitterness and kettle flavour is much more amped up. I settled on more or less even additions of 3 ounces each at 20, 10, 5, and 0 minutes and left the hops to steep for 20 minutes after cutting the heat. This yields a calculated bitterness somewhere in the 100 IBU range, but after applying the hop concentration correction I arrive at something in the mid-70s. My palate says the mid-70s value is a better estimate.

Centennial IPA Tasting and Analysis

The very first impression is that this is an intensely floral beer. I had some indication it would be based on the smells coming out of the fermenter, and it did indeed carry through.

There’s a supporting malt body upfront giving way to high intensity hops and a pleasing, rounded bitterness. The floral character hits, and transitions into fresh lemon zest layered on top of bittersweet caramel. It reminds me of an older West Coast IPA before “juicy” beers became the new normal. 

A pint of Centennial IPA against a white background

The aroma is muted, but I can pick out burnt caramel and what I think are dark fruit esters from the yeast. I could be fooled into thinking this is a British pale ale by aroma alone. 

The hop flavour is high, but is it saturation? Maybe. It might be variety dependent at this high of a hopping rate. I look forward to trying some of the other high intensity hops in similar kettle-only beers. Most importantly there’s no hint of the offending herbal aroma I was looking for. Whatever it was seemed to be a product of dry hopping, which was both unsurprising and satisfying to know for certain.

The flavours mingle

About 3 weeks after brewing the flavours mingle beautifully to form a lemon candy-like flavour. It reminds me of Amnesiac from Phillips Brewing in Victoria. The floral aroma is still there, but is most noticeable right after pouring a pint. There’s a pretty, white billowy head to complement a fresh pint. 

A pint of Centennial IPA below the tap

If I brew a beer like this again I’d probably take out the crystal malt and go 2-row only. I find the crystal a bit distracting in a beer this heavily hopped, and it feels unnecessary to try to add malt character to such a flavourful beer.

Centennial IPA Dry Hopping

At this point I’d gotten enough out of the beer. There was absolutely no hint of the offending herbal aroma, which at least confirmed the original hypothesis. But it also felt like I could go a little further and explore dry hopping in the serving keg. I don’t have a great (or any) way of purging air from hop pellets, so my main concern was the potential for oxygen getting into the keg via hops pellets. I figured this keg probably wouldn’t last long enough to notice anyways, so I went for it.

Dry hopping strategy

The keg was about half full at this point, so I used half the quantity of a full 19 L/5 gallon batch. I added 3 ounces of Centennial pellets to a sanitized muslin bag, and dropped it directly into the cold serving keg (5.5 C/42 F). I purged the headspace and anxiously waited.

24 hours contact time

My first taste was about 24 hrs in, and there was a noticeable dry hop haze in the previously clear beer. The aroma had completely transformed. It was distinctly fruity and “hoppy” but not in a citrus way – it was more of a tropical fruitiness with a slight vanilla finish. The dry hops added an amazing depth to the beer for such a short, cold contact time. Tropical fruit is not what I had expected. How was this going to evolve?!

48 hours contact time

After 48 hrs the aroma evolved to take on a slightly more herbal bent. I caught a familiar hint of wet dog, which I had always associated with new beer due to settling yeast, not dry hopping. The beer had certainly taken on a new identity post dry hop, with a fruit forward aroma and flavour. The dry hop takes over the kettle additions upfront, but the lingering bitterness and kettle flavour draw each sip out into a longer finish. 

72 hours contact time and beyond

By 72 hours I’m picking up hints of the herbal aroma I’m not a fan of. The wet dog is coming in a bit more, most obviously the first bit of a pour – maybe from the warmer beer in the lines in the tower section of the tap? Identifying the wet dog aroma is an unexpected bonus of this experiment. I’ve always associated it with green beer, and it’s not a long-lasting character, but it’s cool to know the source.

After a week of dry hopping I was picking up the familiar orange-pith-extract aroma I was searching for. The identity of the beer had changed yet again, from fruit-forward to herbal, but with a definite fruity presence in the finish. Very interesting transformation with this beer from floral-lemon, to tropical, and finally herbal-fruity. Even with the herbal aroma in the mix, the beer is still pretty enjoyable. Does cold dry hopping lead to less extraction of the undesirables?

Towards the end of the keg the hydrocarbon edge eased off and it swung back to fruity. Overall the dry hop was much higher quality than what I’d achieved with Centennial in the past. Is cold dry hopping the way to go? I may explore changing my process as a result of this cool experiment.

Centennial IPA: Final Takeaways

I found this to be an incredibly insightful brewing experience. It felt like a brew day in slow motion, with new flavours and ideas coming out almost every day. I learned a lot about what I like in dry hopping and how I might change things in the future. These are the main takeaways for me:

  • The orange-pith-extract aroma is a product of dry hopping
  • Cold dry hopping may extract less of the undesirable (to me) compounds than warm dry hopping
  • Separating hot and cold side hopping allows you to really understand the flavours, and whether you’re getting what you want from each
  • A short, cold dry hop extracts tropical fruit and vanilla character from Centennial!

In addition to the above, I realized during this experiment that dry hopping in the serving keg might be the best way to experience the different flavours of a single hop. I’ve always evaluated new hops with kettle hopping and dry hopping smashed together, but this might be too many variables to unpack all together. I’ll definitely consider making this approach standard for evaluating new hops. I’m stoked at the possibilities!

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