Thursday, September 14, 2017

I Hate IPAs

How many times have you heard that, maybe even from your own mouth? The classic India Pale Ale has a lot of bitterness, from iso-alpha acids (isohumulones).  Iso-alpha acids are so-called because they are the result of extraction of the less soluble alpha acids (humulones) from hops, and subsequent isomerization during the boiling of the wort (usually 60 minutes).

The same reaction occurs for cohumulone and adhumulone, which differ in the side chain on the upper right of the chemical structure.

There are other compounds that are extracted from hops, that give aroma and flavor instead of bitterness.  New England style IPAs have very little hop bitterness and extreme levels of hop aroma and flavor.

(Full disclosure: I really love IPAs of all styles).

The haze occurs from the hop oil compounds binding to protein and yeast.  They are best consumed fresh, as most IPAs are, but for different reasons. In each style of IPA, the hop character (bitter in classic IPA or "juicy" in New England IPA) diminishes and changes nature.

This post is inspired by a blog called The Mad Fermentationist, who is Michael Tonsmeire (author of the  book American Sour Beer ).

Some of the important monoterpenes in hop aroma and flavor are linalool

myrcene (resin, sometimes metallic tasting)

geraniol (floral - rose and citronella)

citronellol (dihydrogeraniol)

geranial (citral A)

neral (citral B)

Apparently, monoterpene alcohols are transformed to other monoterpene alcohols during fermentation (see for example  "Biotransformation of Hop-Derived Monoterpene Alcohols by Lager Yeast and Their Contribution to the Flavor of Hopped Beer", Takoi, et al, J. Agric. Food Chem., 2010, 58 (8), pp 5050–5058 DOI: 10.1021/jf1000524).  What this means is that the flavor changes include actual modification of the hop compound profile that the brewer creates.

Another factor is that these monoterpenoids are also present in glycosylated form.  Hydrolysis (by yeast glucoside hydrolases) over time will increase the levels of unbound monoterpenoids.  This has also been found to be a factor in some of the more floral wines, such as muscat, reislings, gewurtztraminers and viogniers. (Park and Noble, "Monoterpenes and Monoterpene Glycosides in Wine Aromas", Beer and Wine Production, Chapter 6, pp 98–109, ACS Symposium Series, Vol. 536 , Chapter DOI: 10.1021/bk-1993-0536.ch006 )

A subsequent study by Takoi et al ,"Screening of Geraniol-rich Flavor Hop and Interesting Behavior of beta-Citronellol During Fermentation under Various Hop-Addition Timings"J. Am. Soc. Brew. Chem. 72(1):22-29, 2014. investigated the timings of hop additions, and their affect on the monoterpene alcohols. This study used Cascade (a hop used commonly in US IPAs such as Sierra Nevada), and the newer varieties Bravo and Mosaic.  As a matter of fact it is the use of these newer, nontraditional varieties that have led to an explosion of possibility in beer flavor beyond the IPAs you may have had before.  Other important newer hops are Azacca, Citra, and Galaxy.

Final reminder: drink New England IPAs as fresh as possible, and check the dates on the can before buying!

Saturday, February 18, 2017

A Twist on Crawfish Etouffée

In many Cajun dishes, a roux is made, and a liquid is added later.  In crawfish etouffee the flour is commonly added at the end.  In either case, the flour acts as a thickener.  Kenji Lopez-Alt's book The Food Lab explains how starch thickens on pg 741-743. The section of the book is a recipe for cheese and macaroni (stealing a large corporation's slogan).  Dissolving starch in a small amount of liquid disperses the starch granules, which prevents the formation of clumps when large clumps of powder hit hot liquid, gelatinizing on the exterior and protecting the interior starch from being hydrated.

Amylose is a linear polymer of glucose, with an alpha-1,4 linkage (figure to be added in a couple of days).  This long polymer is actually curved and spirals around itself.  Addition of water breaks the intermolecular interactions and the polymers are unwound.  The polymer chains get entangled, leading to a viscous liquid or gel.  In my opinion this can reduce the flavor impact of the other ingredients.  As a roux is cooked, the amylose breaks down, adding flavor but reducing the water absorbing ability of the roux.  However, if little liquid is added, then this is a moot point, and the texture will be quite different.  I did add dry flour to the melted butter.  With just vegetable oil this would have not been a problem.  Butter is about 15% water, I wonder if using clarified butter would have made a difference.

The buttery rich end result, which lets the crawfish flavor come through, is shown below, with a Pale Ale from Fairhope Brewing.  This recipe serves 4.  Just kidding, it serves two people who each had seconds.

Crawfish Etouffée
1 stick butter
1.5 tablespoon all purpose four
¾ cup diced celery
¾ cup diced green bell pepper
¾ cup diced yellow or white onion
12 ox crawfish tails
½ teaspoon salt
¼ teaspoon cayenne pepper
black pepper to taste
¼ chopped green onions
¼ cup chopped fresh parsley

Melt butter on medium heat, stir in flour.  Whisk to make sure there are no lumps.  Stir until the color of peanut butter.  The roux will roam as it cooks, and may look separated during many steps - see the comment right before recipe begins).

Turn heat to medium-low, add celery, onions, bell pepper, cook for 15 minutes.  Stir frequently.

Add crawfish tails, bay leaves, salt, cayenne  and black pepper, cooking on medium low for 12 minutes.  The roux will start to stick toward the end, scrape the bottom of the pan.

Add green onion and parsley, cook 2 minutes, then remove from heat and cover.  After 2 minutes, serve with hot cooked white rice.

Friday, February 17, 2017

Diacetyl Sources and Metabolism

In the post Diacetyl Basics I described the structure, flavor and aroma of diacetyl.  The next article will rely an online article by George de Piro and a review by Krogerus and GibsonKrogeris and Gibson, DOI 10.1002/jib.84 .  Another article you may wish to read is from Brew Your Own.

It is desirable that if diacetyl is being made, that only your brewer's yeast culture is doing so.  Most of the time, any diacetyl produced will be reduced to acetoin (by either enzymes that generally reduce any small ketone to an aldehyde, or enzymes specific to the task).  This is the process labeled 1.  In biochemistry, reduction is commonly done by using adding two H atoms via NADH + aqueous proton + 2 electrons.

A second reduction will form 2,3-butanediol (not shown, that reduction reaction is indicated by the unlabeled single down arrow below acetoin)  The carbon with the -OH group is chiral.  In 2,3-butanediol the second alcohol group is where the remaining ketone (C=O) group was, and that carbon also is chiral after the second -OH is made.

A large source of problems with diacetyl in the final product, is high levels of alpha-acetolactate which can convert to diacetyl in the oxidative decarboxylation process labeled 2.  Generally, you can reduce formation of diacetyl in finished beer by decreasing process 4, increasing process 3, or increasing process 5.  You can also lower the amount of diacetyl in the final product by making more diacetyl (should be a line in Alanis Morissette's song Ironic, don'tcha think?).  In other words increase the rate at which reaction 2 occurs, as long as reaction 1 removes the diacetyl so produced.  The latter approach (reaction 2 followed by reaction 1) is done intentionally when doing the diacetyl rest  in lagers(raising the lager to room temperature for a couple of days after fermentation is complete).  If you judge a lager with detectable diacetyl, absent any other off-flavors that indicate an infection, drop a hint that their diacetyl rest may not have produced the results desired.  Don't say "You fergot you're diassetyl rest, dumbass!".

What is not obvious is that if the yeast is not provided with enough valine, the pathway which makes valine from pyruvate (top of figure straight down to bottom) will be upregulated, producing higher levels of alpha-acetolactate.

Of course, different strains of yeast will vary in the amount of diacetyl they tend to produce even under optimal fermentation conditions.  Highly flocculent English ale yeasts tend to produce higher levels of diacetyl.  This is why English Ale styles in the BJCP guidelines says that some diacetyl is acceptable.

A last note on removing diacetyl or preventing its formation: adding enzymes such as SEBmature L or Alphalase Advance 4000 or alpha acetolactate decarboxylase (an enzyme that accelerates process 3.)  I think you can google that for yourselves if you got this far in the post.

Sunday, February 12, 2017

Feb 18-19, 2017 is a Good Weekend for Beer in Birmingham

Today I helped judge beers for the Avondale Pro-Am competition.  A bartender was to choose a style of beer, perhaps with an interesting ingredient, and pair with one of the Avondale Brewers to make it.

The man in the shirt that says Judge is a fellow BJCP judge, Danny Reid.  The Pro-Am event for the public, where you can taste some of these beers, is next Sunday (Feb 19, 2017)  2-5 pm at Avondale Brewing.

The other event is Saturday, at, called the Heart of Dixie Open (HODO).  HODO judging was done on Feb 4, but I was unable to attend.  The event for the public is Saturday Feb 18, 2017 , starting at 1 pm.  A bunch of the Carboy Junkies will be pouring their beer there.

The Avondale and Good People Facebook events pages are the most comprehensive source for their events.  And for the Carboy Junkies, unless you join our mailing list.

Thursday, February 9, 2017

Alpha Acids - The Bitter Truth

(Thanks to Mike Jablonsky for the title).  A lot of brewers know that alpha acids cause bitterness somehow.  In this article I will discuss just a little bit of their structure, names, and use.

First of all, why are these called acids?  There are no carboxylic acid groups in the molecule (see the structures below and note the absence of a carboxylic acid group).  The reason they are called acids is that alpha acids are more soluble in basic pH.

Humulone is just one of the three common examples of the class of molecules called humulones. One step in the biosynthesis by the hop plant (Humulus lupus) is the transfer of the side chain from an amino acid to the humulone precursor.  I have aligned the structures of the amino acid above the humulone, so that you can see where the side chain went onto the humulone molecule.  The other two humulone structures are cohumulone and adhumulone:

Looking at the bottom of the molecular structure, we see a hydroxyl group, and an isoprenyl group. Isoprenylation (commonly called prenylation) is a common building process in plant biochemistry.  If you replace the bottom hydroxyl of humulones with an isoprenyl group, you get the beta acids (lupulones). Lupulones are even less soluble in water, due to the switching out of a -OH group which can hydrogen bond with water, for a "hydrophobic chain" which cannot favorably interact with water.

Neither the alpha acids nor beta acids dissolve at a high enough concentration to impart any perceivable bitterness.  You must change these structures through isomerization.  That will be a separate topic for another day.

Thursday, February 2, 2017

Diacetyl Basics

First things first: you may have heard the word diacetyl pronounced many different ways.  A couple of them are common, and largely depend on which country you are in.  The problem lies in the different ways that acetic \ə-ˈsē-tik-\) acid and acetate (\ˈa-sə-ˌtāt\) are usually pronounced. The common pronunciations of diacetyl are \ˌdī-ə-ˈsēt-əl, dī-ˈas-ət-əl\, and are based in turn how the acetyl group is pronounced.  I think more UK speakers pronounce with the long e, Americans with the second pronunciation.  You could finesse this issue entirely by saying 2,3-butanedione, which is the systematic nomenclature for this compound.  Here it is:
Any chemical structures which I post are generated by me, feel free to download to your collection under a noncommercial Creative Commons license.

Diacetyl is a flaw in almost every style of beer if it is noticeable.  There are variations in how sensitive tasters are to the flavor and aroma.  At high levels the aroma is strongly artificial butter (which IS diacetyl).  At lower levels, diacetyl mixes with other flavors and aromas and is perceived more as butterscotch.  This level is acceptable in some beer styles, but even then moderation is desirable.  Even if a taster does not perceive any of these flavors and aromas, the taste will definitely seem off to the consumer.  The consumer would likely finish the beer, but not order another.  Diacetyl coats the tongue, and diminishes perception of hop bittering and hop flavor compounds.

There are several sources and sinks for diacetyl.  Diacetyl is produced during fermentation, then normally reduced by yeast enzymes to acetoin and 2,3-butanediol.  However, things can go awry with yeast.  If the fermentation is problematic, high diacetyl levels will be just part of a whole suite of symptoms, and the beer would not be released for public consumption.  The consumer would be more likely to experience high diacetyl levels from bacterial contamination, either in the package or through dirty beer lines.

A future post on diacetyl will get more into the weeds of chemistry.  Any beer judges want to hop in with their experience in detecting diacetyl, or its effects on the beers they judged?

Credit to for the pronunciations.