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The prevailing wisdom seems to be that dry hopping is for aroma only, and effects on flavor are assumed to be a matter of perception. (i.e. smell affects taste)

However, while attempting to "fix" a beer that came out far too sweet, I have been looking into hop extracts, etc. While researching I came across this message:

From a chemical point of view, dry hopping will extract all of the alpha and beta acids in hops. The humulones, lupulones and other volatile oils are isomerized in the alcohol and water (the alcohol dues most of the extraction). Yes, more aroma and flavor will be extracted, but so will bitterness. We dry hop most of the time to add aroma to the beer, so most of the time we dry hop with low alpha acid "aroma" hops. Try dry hopping with Galena, Perle, Simcoe, Challenger, Northern Brewer or other high alpha acid hop. You will get the bitterness!

Is this true? Will using high-alpha hops for dry hopping contribute bitterness?

3
  • Meant to include the source of that comment: groups.yahoo.com/group/Zymurgy/messages/… Nov 14 '11 at 21:07
  • Thanks for that. The whole part up to the parenthesis is bogus.
    – BeerSensor
    Nov 21 '11 at 14:56
  • Tomorrow night I'll be conducting an experiment of my own. I'll be making three seperate 1 gallon batches just using some free LME I came across. 1st gallon I'll drop all of one ounce of Cascade Hops at the beginning of a 60min boil. 2nd gallon I'll do a hop schedule outing the 1 oz in over the course of the hour. 3rd gallon I'll be doing no hops, and once all three batches have converted ABV I'll add an ounce of hops to secondary and letting all three go for another week to 10 days before bottling. Then I'll taste test and report back here the difference.
    – user12976
    Nov 24 '15 at 22:20
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That quote you posted is a mess. I don't even know what they're trying to say there.

Yes, dry hopping will add bitterness, but not in the usual sense (which is iso-alpha acids). Dry hopping is done cold, so there is essentially no isomerization of alpha acids going on, which is what normally happens in the kettle boil. The bitterness that comes from dry hopping is mostly from polyphenols. The polyphenols of low-molecular weight will add bitterness (catechin, epicatechin, procyanidin, prodelphinidin, etc), while the higher molecular weight polyphenols (tannins) will add astringency.

Beer Sensory Science, Bitterness

Beer Sensory Science, Astringency

3
  • So it seems that the salient point is that, while alpha acids may be extracted from dry hopping, they will not be isomerized thus they will have no effect on bittering. Nov 14 '11 at 22:32
  • That is correct, although not many alpha acids will be extracted into a cool aqueous product. They are very hydrophobic, so they don't like to be in water. As I said, most bitterness resulting from dry-hopping comes from polyphenols.
    – BeerSensor
    Nov 15 '11 at 16:30
  • 2
    I love science. :) Nov 17 '11 at 23:00
9

I've recently done the experiment. Zero boil hops, but dry-hopped with 6 ounces of high alpha acid hops (Summit, Simcoe and Apollo). This brew is quite bitter, whatever the reason, and it is of the same "kind" of bitterness one would expect from hopping in the boil and not particularly astringent.

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  • Very interesting! I'd love to know if this is verifiable and what compounds might be causing the bitterness.
    – bk0
    Sep 27 '12 at 14:56
  • Well this is confusing, I'm not sure what the answer is now. Mar 3 '14 at 16:46
  • How large was the batch?
    – user613068
    Apr 13 '15 at 18:20
  • IMO you can bitter with cold additions of hops. Don't believe, stick a hop pellet in your mouth. I think the real issue is there hasn't been any math done to estimate cold addition bittering. It takes a lot of high AA hops, but it does happen. This is like cold steeping coffee, works but really inefficiently. Dec 30 '15 at 11:11
6

I've had bitter hop flavor come from dry hopping as well.

The quoted text from the OP makes sense to me: Dry hopping is essentially creating a tincture. Don't believe me? Drop 3 grams of a high alpha hop in a liter of vodka and come back in a month, chose something fruity and popular like mosaic or galaxy. 3 grams is toughly equal to 2 oz in a 5 gallon batch.

I did a dry hop test in which I added pellet hops to vodka diluted to 5% alcohol. I scaled my hop additions to 1 oz and 2 oz and 3 oz in a 5 gallon batch with several different hop varieties and tasted them at 1 day, 3 days, 1 week and 3 weeks. I dont have my notes handy, I remember that I used Cascade, Saaz, German Hul Mellon and, Fuggle - that may be all of them. What I recall clearly is that the fuggle was my easy favorite with herbal flavors and lemon and grass and that the Hul Mellon was extremely bitter in the higher concentrations (though the lowest actually got some of that nice melon undertone - the others where overwhelmed with bitterness.)

0

Some fairly recent research has shown that dry hopping affects beer bitterness in a number of different, interesting and even unexpected ways.

To address the main question of whether or not dry hopping adds bitterness: it absolutely can (but not necessarily).

Humulinones:

Hops, and especially hop pellets, contain humulinones, a recently-discovered oxidation by-product of hop alpha-acids. They are suggested to be ~65% as bitter as iso-alpha-acids (i.e. 1 ppm of humulinone would be ~0.65 IBUs), and are also readily dissolved in beer without boiling. That is to say, they can be directly extracted into finished beer when dry-hopping.

This study tested commercially available IPAs and found humulinone concentrations as high as 24 ppm. It also suggests that humulinones are not derived from hops during boiling (meaning their contribution is basically all due to dry hopping). So, given the relative bitterness of the humulinones, it seems fair to conclude that a beer with 24 ppm of humulinone has ~16 IBUs worth of bitterness from dry hopping alone. Not at all a trivial number (though not huge, to be fair).

Hulupones:

Another study (which also confirms some points about humulinone) suggests that hulupones (an oxidation by-product of hop beta-acids) can contribute directly to beer bitterness through dry hopping, though it's much less clear to what degree. Hulupone is shown to be ~85% as bitter as iso-alpha-acid (i.e. 1 ppm of hulupone would give ~0.85 IBUs).

Previous studies (cited in the paper) suggest hulupone levels in hops anywhere between 0-3% by weight, and the study itself doses hulupone extract into beer at levels up to 40 ppm (indicating it is clearly soluble). Though no conclusive evidence is shown (and I could not find any additionally), if hops with high enough hulupone concentrations are used for dry hopping, they should be able to contribute non-negligible amounts of bitterness directly.

Dry hopping and pH:

In the first MBAA study linked to above, it was shown that dry hopping seems to linearly increase the pH of the beer, and that the increase in pH seems to cause an increase in the perception of bitterness.

Dry hopping can actually decrease bitterness:

Interestingly, dry hopping can remove iso-alpha-acids from finished beer (presumably by the vegetative matter adsorbing the hydrophobic acids and falling out of suspension). In yet another study, beers of relatively high bitterness were dry hopped with Cascade hops at 1 lb. per barrel (a modest amount by modern standards...) and were shown to have lost up to 37% of their iso-alpha-acids in the process (51 ppm before dry hopping and 32 after, in the paper).

Some general take-aways:

  • While dry hopping absolutely can add bitterness, it can also take it away.
  • In general, beers low in bitterness to begin with may have significant bitterness contributions from dry hopping
  • More bitter (to begin with) beers may tend to lose bitterness in the dry hopping process, even if some of it is replaced with bitterness from humulinones or hulupones.
  • It's possible (and seems feasible) that high-alpha hops, having more of the precursors to humulinones, could contribute more bitterness during dry hopping that low-alpha hops. This appears to have not been studied.

Further, here are two blog posts which touch on this subject in a more homebrew-friendly fashion, including recipes, home-scale trials and discussions with the author of two of the studies I've linked:

I'll also note that the accepted answer's points on polyphenols contributing to bitterness are still spot-on and entirely relevant.

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