Wednesday, July 6, 2011

Hop Oil: Is Bigger Better? A preview of ongoing research at OSU

Time to take a step back, scratch the chin, and ponder what it’s all about.

I’m talking of course about the Big Questions. No, not whether great beer makes you a better person (I think it does) or whether a beer with the right kind and amount of hops can make you live longer and happier (you gotta believe).

The Big Question for the moment is this: Is Bigger Better? That is, higher total hop oil content a reliable measure of the hop’s potential for great flavor?
Let’s break it down. It’s fairly certain that the same amount of whole cones will have a higher total oil content that even the best crafted pellet. Does this mean that the whole hop will add more millileters of total oil to your pint glass than a good pellet? Possibly yes, depending on the specific oil compound.

But does it mean that the whole hop will add more of the oil compounds we desire to your pint glass? Ah, that’s the question. Actually, it opens up a series of questions, the first of which is what oil compounds do we actually desire?

It would be so easy if we could crank up the high tech machinery, identify particular oils, measure the percentage of said oils in a given assay of hops and then conclude that one cultivar is “better” because it has more of the “more desirable” oil compounds. But, alas, god’s not in the machines, and really and truly there are as many gods as there are palates, although perhaps some flavor gods are more better than others (with apologies to the grammar gods).

Let’s look at the Cascade hop for a second. A Cascade whole hop can have 40-60% more total oil (in mL/100g) than an assay of your typical type 90 pellet. Looks impressive. And many brewers do have success in dry hopping with “big total oil” varieties (eg, CTZ). But let’s peel back the onion a bit.

Does the “big oil” hop deliver the “most desirable” oils? Again, lets look at Cascade. Between 70 and 80% of the total oil in Cascades is myrcene (roughly ~53%) and humulene (~26%). In a well designed pellet, the myrcene-humulene (M-H) content is approximately 35% and 26%, respectively. In short, the M-H content in a Cascade whole hop will likely gobble up between 75 and 80% of the total oils, but in a pellet, the M-H content is far smaller at around 55-60%.  

OK, so, two more questions. One, what’s wrong with myrcene and humulene? And two, all fine and dandy, but isn’t the real measure how much of the oil actually ends up in your pint glass?

"Odors Compounds" chart from OSU
Click here for a larger version
 Break it down. First, on the question of the desirability of specific oils, take a look at the “Odor Compounds” chart from Oregon State University. Myrcene is described as “Green, balsamic and slightly metallic aroma). Humulene: piny/woody. Certainly nothing wrong with those descriptors.

For perspective, take a look at some of the others, such as geraniol, limonene, citral, linalool, and we come across descriptors at least this drinker tends to find a bit more appealing (rosy, fruity, citrusy, floral, orangy, etc). Anecdotally, I haven’t heard too many brewers tout either myrcene or humulene as “target oils.” Then again, we’re huge fans of Odell and I’m sure their Myrcenary Double IPA is a knock-out!

On the second question – how much of the oil makes it in your pint glass – the answer is more complex, but equally interesting. A quick bit of background first (sorry for all the parenthetical chatter!) – IH is sponsoring research on the correlation, if any, between the medium of the hop (whole flower vs four vendors’ type 90 pellets) and the relative contribution of total and specific oils when dry hopping. The results should be forthcoming soon but we’ve already observed a thing or two of the eyebrow raising variety.

Even though the whole hop has about 70% more total myrcene than a typical pellet, the amount of myrcene from the flower that is dispersed into your pint glass appears to be substantially less (5.5 ml vs ~6.5 ml). A far lower amount of myrcene is “extracted” compared to a pellet (5% compared to 17%). It appears that a big chunk of the myrcene in the whole hop is lost. (Where did it go? Another question for another day).

Do the smaller but perhaps more flavorful oil compounds exhibit similar “volatility?” Does the design of the pellet (eg. average particle size , density and diameter) influence the expression of certain desirable oil compounds? Do certain oils have a “saturation point” where, regardless of the starting point of oil quantity in the flower or pellet, when added to a beer-like solution, is there a threshold for maximum solubility? Does the design of the pellet influence the rate of oil extraction? And how does all of this potentially impact what brewers do or should do in the brewhouse?

For those answers, and more fun questions, please stay tuned. In the meantime, viva la difference! Using the scientific method, with the aid of technology, we can draw verifiable and repeatable conclusions from the data. But, as we’ve said before, even the most sophisticated palates will disagree on the description let alone desirability of the oils from the same hop as they work themselves into your pint glass. See

July 4, 2011


  1. I had to stop myself from adding comments to all your posts, but I just wanted to say I love your blog and keep up the good work.

    Especially the articles with Dr. Haunold, he's a veritable fount of knowledge.

  2. Any updates on this? Super interested in even preliminary data.

    Do you have a link to a chart that details typical essential oils content by variety? (Like in the charts you've posted over on but with more than just myrcene detailed? (and Linalool for 3 hop varieties?)

    The detail in the OSU "Odor Compounds in Cascade and Willamette Hops" chart is probably way more detailed than I'm looking for, which is great, but is only looking at Cascade and Willamette...

    Although I know I'm not being realistic, I'd LOVE to see a "hop oil sensory training kit" like the Siebel Institute's Off-flavor Sensory Training kit that came with small quantities of single hop oils that you could spike into a liter of boring lager to evaluate the flavor contributions of each oil one at a time.

    Knowing that this is pretty unlikely any time soon, my backup plan was simply to go down a list of essential oil concentrations by hop variety and to brew a number of single hop IPAs with all late additions and dry hopping with the hop variety that has the greatest concentration of each essential oil to try and get a feel for what each oil contributes that way...

    (But I can't find such a chart to even attempt it.)


  3. Hmm... These guys manufacture the FlavorActiv kits and are generally sensory evaluation obsessed; they have a 10 beer flavor standard kit for 69GBP already; these would be the guys to talk to to see about getting beer aroma chemicals in tablet form for adding to beer.

    If you had the data on general concentrations of each oil by hop variety you could even make blends that approximated the contributions from real varieties of hops or, even more excitingly, you could simulate concentrations for theoretical hops you'd like to see...

    -Then you could come up with a target desired hop profile that could keep your OSU buddies busy for a LOONG time.


  4. Forgot the link.


  5. Sorry for all the rapid-fire comments, but I found the hop oil concentration database I was looking for. (USDA ARS had it; of course! -Although some of the data is astonishingly old and some of the Yakima proprietary varieties seem to not be in there... ;( -Sure would be good to have for providing substitutions based upon oil content...