Techniques for Maximizing Hop Flavor and Aroma

Introduction
This blog post provides a summary of the techniques I’ve found for maximizing hop flavor and aroma, based on my experimental results and general experience.  Others have said many of these things before, and in some cases with better writing skills.  I am not claiming that anything here is a new discovery; I’m just reporting what I’ve found from my personal brewing experience.  (As usual with this blog, the contents of this post may change over time as I revise and update what I’ve learned.)

1. Use a Lot of Well-Preserved Hops in the Boil
When using too much hops there is a risk of tannins that can cause a grassy taste (Palmer, How to Brew, p. 44) and of course excessive bitterness.  But big, hoppy beers seem to require (strangely enough) lots of hops.  In a 5-gallon (19-liter) batch, six ounces (170 g) of hops very late in the boil (and/or at flameout) and an additional two ounces (57 g) for dry hopping is good, but on the low side for a really big beer.  I won’t hesitate to double that amount of hops, for a total of one pound (454 grams) in a 5-gallon (19-liter) batch.

Some beers that I’ve brewed with lots of hops have had a “grassy” flavor, as noted by John Palmer.  It’s not necessarily bad, but it’s not the character of the hops that I look for.  At this point, I think that this flavor was caused by using improperly-stored hops.  In a six-gallon (23-liter) boil, I’ve added one ounce (28 g) at 15 minutes before flameout, 11 ounces (312 g) at flameout (with 10 minutes of post-flameout natural cooling), and an additional 2 ounces (57 g) during dry-hopping, and not noted any grassy flavor (but lots of wonderful citrusy flavor).  All of these additions were made with properly-stored hops, which may have been a critical factor.  (That beer turned out quite well and measured only 41 IBUs.)  I now try to use only hops less than a year old that I believe have been properly stored.  Pellet or whole-cone hops stored in nitrogen-flushed packaging seem to keep well for a very long time.  Hops not stored in nitrogen-flushed packaging must be kept in a freezer at all times.  If hops aren’t stored in nitrogen-flushed packaging and are not continually kept at refrigeration temperatures or lower, I don’t trust the quality, even if they are in vacuum-sealed mylar bags.  Some LHBS will buy hops in bulk and re-package them in smaller quantities.  If those smaller packages are not flushed with nitrogen and/or stored continuously at close to freezing temperatures, the quality may suffer.  Since becoming more careful about my hop-storage conditions, I’ve not noticed any grassy flavor in my beers.

By adding lots of hops late in the boil, IBUs are difficult to predict using standard models.  On the one hand, additions close to flameout will produce more IBUs than predicted by standard formulas (e.g. Tinseth, Rager, Garetz) because of continued heat after flameout and the oxidized alpha acids that are produced quickly in hot wort.  On the other hand, once you get above 2 ounces (57 g) of AA 10% hops in a 6-gallon (23-liter) boil, IBUs increase less than standard models will predict due to a solubility limit.  (The Garetz model does have a correction for hopping rate, but I find it to be too conservative.)  The mIBU approach addresses flameout additions but not high levels of alpha-acid concentration.  A different post provides a hopping-rate correction factor that is linked to alpha-acid solubility.  Both methods are combined in an online calculator for the mIBU method I’ve developed.  Since then I’ve developed another IBU model called SMPH.  At any rate, I’ve learned to not fear large amounts of well-preserved flameout hops with a 10-minute rest period before forced cooling.

2. Add Hops Late in the Boil, and/or Cover the Kettle After Late-Hop Additions
Hops should be added late in the boil.  How late?  I’ve found that a one-minute steep time had a noticeable improvement in hop flavor compared with longer steep times when the kettle is uncovered.  I’ve also found increased hop flavor by adding hops at flameout and then letting the wort cool naturally (with the lid on) for 10 minutesThe difference between a 1-minute steep time and a 10-minute steep time is probably only a just noticeable difference; minor differences in steep time don’t seem to be that important.

Covering the kettle after late-hop additions (i.e. no greater than 15 minutes before flameout) might provide an increase in hop flavor.  I’ve also found no noticeable change in flavor between 1, 5, 10, and 15-minute additions when the kettle is covered, suggesting that hop flavor is reduced through evaporation, although there may be other factors influencing flavor.

According to Greg Noonan, “the bitterness derived from long boiling is coarser than that from a more moderate period” (Noonan, New Brewing Lager Beer, p. 154), which also suggests that more hops for a shorter time in the boil is advantageous.

In short, I add hops close to flameout in order to preserve hop flavor.  If I add hops at 5, 10, and/or 15 minutes before flameout (in order to adjust the bitterness), I cover the kettle to prevent the loss of evaporating hop oils.

3. Hop Stands: If Used, Keep Them Reasonably Short
Keeping hops in the wort at various sub-boiling temperatures for 60 minutes adds maybe some extra body, but little to no additional hop flavor.  A 45-minute hop stand at 170°F seems to add no hop flavorA 10-minute hop stand (with hops added at flameout) can produce very nice hop flavor.  However, I’ve found no perceptual difference in flavor with hops boiled for 10 minutes or steeped at 170°F (77°C) for 10 minutes, and so wort temperature may not play a large role in preserving hop flavor.

The take-away message seems to be that even at sub-boiling temperatures, steeping for too long removes (or fails to produce) that wonderful hop flavor.  However, sub-boiling temperatures don’t seem to provide much more (or less) flavor than steeping in boiling wort.  Because of these conclusions, I’m less of a fan of hop stands than I used to be.

4. Dry Hop for Aroma and Flavor
I’ve found through informal experiments that small to moderate hop aroma requires a large amount of late-hop or flameout additions.  But a bigger aroma can be obtained by also dry hopping with an ounce or two (about 25 to 60 grams) in a 5-gallon (20-liter) batch.   Flavor and aroma are intertwined, and so increasing the aroma tends to have a large positive impact on flavor.  (Noonan says it better: “the full, fresh aroma of hops is only captured by ‘dry-hopping’.”  (Noonan, New Brewing Lager Beer, p. 78.)  Adding even more hops provides more aroma, up to a limit.  Lafontaine and Shellhammer recommend 400 to 800 grams per hectoliter, or 2.8 to 5.6 oz (80 to 160 grams) in a 5-gallon (20-liter) volume (“Impact of static dry-hopping rate on the sensory and analytical profiles of beer”, S. R. Lafontaine and T. H. Shellhammer, J. Inst. Brew., 124, pp. 434-442, 2018).

5. Dry Hop using a Weighted Mesh Bag
When I dry hop, I put the hops in a very large mesh bag along with some weights.  The bag makes for easy removal of the hops, and the weights force all of the hops to be submerged.  The large mesh bag allows the hops to move around in the wort.  If you have a narrow-necked carboy, you can consider racking the beer to the keg or bottling bucket before removing the hops.

6. Dry Hop With Well-Preserved Hops
John Palmer notes that dry hopping may yield “a dry aftertaste, like old tea” (Palmer, How To Brew, p. 44).  Gordon Strong comments that “it can produce a lingering grassy, vegetal note that some may not like” (Strong, Brewing Better Beer, p. 72). He recommends “limiting the contact time of dry hops in beer to 3 to 7 days” (ibid, p. 72).  In my experience, a week of dry hopping is not too long as long as well-preserved hops are used.  Other options include (a) dry hopping for a day or two, (b) dry hopping for 2 or 3 days, removing those hops, and then dry hopping again with fresh hops for another 2 or 3 days, or (c) adding hops during the active fermentation, possibly along with later additions.  There are lots of options, but using well-preserved hops seems to avoid unwanted flavors.

7. Yeast Selection
I did an informal experiment comparing four yeast strains from the same manufacturer (Fermentis), each added to identical wort.  A variety of Citra, Mosaic, Simcoe, and Amarillo was used in the boil, and Amarillo was used for dry hopping.  The measured IBUs of the four beers were similar (ranging from 47.0 to 51.6) and so the IBU differences between the beers were below the threshold of 5 IBUs needed to detect a difference in bitterness.  The flavors were quite different, however.  Safale US-05 (American Ale) yielded a beer that was, in my opinion, pretty standard, which is not surprising because it’s the yeast strain I use most often.  Safale S-04 (English Ale) had a full-bodied taste with a very nice stone-fruit flavor.  It seemed smoother than the US-05, even though there was only a 3-IBU difference.  Safale S-33 (ale yeast for “fruity and hoppy beers”) had a more “resinous” flavor, like pine, which made more of what I consider a West-Coast American IPA.  Finally, I felt that Safale K-97 (“German Ale”) did not mix well with the American hops; it had a thin flavor, more like grapefruit rind than a full citrus flavor.  The importance of yeast strain on hop flavor should not be underestimated.

Other Techniques
I’ve tried making a “hop tea”, and adding that instead of hop cones or pellets to the secondary.  Noonan gives fairly detailed instructions (Noonan, New Brewing Lager Beer, p. 160) and recommends the practice.  I’ve found that this tea doesn’t really capture the fresh hop flavor I’m looking for, but steeping in vodka or everclear instead of water brings out the flavor much better.  It’s not yet clear to me how to use this technique without increasing the alcohol level of the beer.

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