Monthly Archives: March 2011

It’s been two weeks.

And that’s too long to go without a post. I apologize. I’ll do my best to rectify the situation soon.

In the meantime, drink some beer.


It’s been recognized in beer since the 1870’s, and it may just be one of the most well-known flavor defects in beer across the world. Just because it’s recognizable, however, doesn’t mean people are necessarily bothered by it since Corona and Heieneken sell plenty of bottled beer. It’s becoming common knowledge among some of the beer-drinking public that putting beer in clear or green bottles will allow it to become skunky or “lightstruck”. Following right behind is the growing awareness that, with the use of specialized hop extracts, brewers can successfully put beer in such bottles without resulting in skunked beer (Miller products being the best known of these). We’ll discuss these topics and more as we explore this phenomenon. A warning: there will be chemistry.

First, the molecule: 3-methylbut-2-ene-1-thiol, but you can call it 3-MBT for short. With a threshold of around 4 parts-per-trillion in beer, 3-MBT is among the most potent flavor compounds that can be found in beer; as such, it does not take much to ruin your beer. If you drink your beer from a pint glass on a sunny patio you may notice this flavor by the time you reach the bottom of the glass – that’s how quick this problem can arise.

Here’s the little bugger now. Rather innocuous looking, isn’t he?

3-methyl-2-butene-1-thiol, or 3-MBT: Source of Lighstruck / Skunk flavors in beer

We’ll take a small break here for a minor organic chemistry lesson involving molecular nomenclature. The great thing about O-chem is that there are rules by which molecules are named, and if you know the rules you can figure out the molecule’s shape and features. Let’s take 3-methylbut-2-ene-1-thiol: the “but” part of the name tells you that there we are dealing with a carbon-chain that is 4 carbons long (1 carbon: meth-; 2 carbons: eth-; 3 carbons: prop-; 4: but-; 5: pent-; etc etc). Each carbon is numbered sequentially, and I’ve included the numbers in the image. As the name implies, there is a “thiol” group on the number 1 carbon. A thiol is like an alcohol group but with a sulfur atom in place of an oxygen, -SH instead of -OH. Continuing to look at the name we see that on the number 2 carbon there’s an “ene” group, which means that there is a double bond between that carbon and the next. Finally, on the number 3 carbon, there is a methyl group (essentially a branch made up of a carbon “chain” made of only one carbon – remember “meth-” meaning 1 carbon?). So, if one of the carbons off of #3 is a methyl group, which one is the #4 carbon? For the purposes of this molecule, it can be either one, and whichever is #4 then the other is the methyl group. This concludes the nomenclature lesson. Now, back to the… well, more chemistry I guess.

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Does Guinness travel well?

Well, beer in general doesn’t travel well, so I’m going to guess “no”.

I ran across an article about a study by the Institute of Food Technologists (link in the sidebar) which sought to find out if there was any truth to the idea that Guinness served in Ireland tastes better than that which is served elsewhere. Their preliminary results indicate that, yes, Guinness served in Ireland tends to score higher in flavor preference to those outside the country, even after accounting for various variables.

I’m not surprised. In fact, I bet this is the case for most any beer in the world: it’s very likely going to taste better the closer you are to the brewery. This is because there is less transportation and time required to get the beer to various parts of Ireland compared to the rest of the world, meaning less time for the flavor to deteriorate from oxidation and aging. Also, Guinness probably has more influence over local bars and how they maintain their tap lines. This is also related to proximity; there are probably more Guinness reps combing the pubs of Dublin than there are in Boston. They also mention the affect on popularity and the effect on freshness: Irish pubs will probably be going through more Guinness than pubs elsewhere, meaning there is fresher beer on tap since the turnover rate is higher. All of these factors should be no-brainers.

Other thoughts I had when I read this was about the methodology. I haven’t read the paper, but I’m going to assume that all 4 researchers tasted Guinness in a number of different countries, and overlapped their territory, because otherwise there would be no way to control for the “assessor” variable during the analysis. I also note that in the abstract, they say their researchers were “non-expert”. I would have hoped that they would have had some level of beer flavor training, however basic, before undertaking this project. Another thing I wondered about is how they controlled for the “ambiance” variable. While they did mention the possibility that ambiance could affect the assessment of the beers, in the abstract they say the statistical significance remained even after controlling for ambiance. Now, I’m not sure how you can control for ambiance without tasting all the beers in a single location; it doesn’t make sense to me.

I was also a bit irked at the tone from the following passage, which seems to assume that the Journal of Food Science, or beer research in general, might be considered a non-scientific discipline:

That the Journal of Food Science is a serious publication can be inferred from some of the other material in the March issue. One feature is headed: “Technological Optimization of Manufacture of Probiotic Whey Cheese Matrices”. A second reports: “Improved Sauerkraut Production with Probiotic Strain Lactobacillus plantarum L4 and Leuconostoc mesenteroides LMG 7954”.

It’s almost like they needed to convince themselves that Food Science is actually science…

PS: the pint of Guinness I had at the Panorama Sky Bar at the end of the Guinness tour was the most expensive “free” beer I’ve ever had: 17€. But they poured a little shamrock in the head of the beer, so that’s got to be worth something, right? Of course the 17€ was for the tour of the “brewery” (read: “museum”), but really the only worthwhile part of the tour was the view at the top and the pint in your hand.

Brewing Technology Blog

I was just going through some of the links that have been sending traffic to my blog, and I noticed one of them was from a Tweet that Bill Simpson (from CaraTechnologies) made awhile back, calling it a “great blog about beer tasting”; awesome! Although he may not recall it, I’ve met Bill Simpson before and he is quite knowledgeable about beer and brewing. I suppose you’d have to be if you were a consultant for any number of brewing-related issues. Anyway, he’s sent some traffic my way, so I’ll send some to him. His blog is The Brewing Technology Blog and has lots of great information. Now, I’m telling you this in confidence that you won’t run off to some other blog and forget about this one. Fortunately, he seems to update his blog slightly less often than I do, but he also covers a broader range of topics than I do, too.

At any rate, check it out. It may be more suited for commercial brewers than homebrewers or beer drinkers, but there is information there that can be used by anyone.

That’s not what I meant by “Lawnmower Beer”.

Today, we’ll take a quick look at the source of grassy flavors in beer. This off-flavor is caused by the “leaf alcohol” known as cis-3-hexenol. This compound arises in various vegetative systems (flowers, leaves, stems, etc) when unsaturated fatty acids such as linolenic acid are degraded. As you can see by the picture in that last link, linolenic acid is a fatty acid with a long 18-carbon chain (tail) with a few points of unsaturation (meaning double-bonds along the chain). These double bonds are highly reactive and the fatty acid chain can be broken here. When this happens, cis-3-hexenol can be formed as the tail-end piece and grassy flavors will result. In beer, this happens most frequently when old hops are used particularly if they haven’t been dried thoroughly or stored properly. So, if you’re growing hops at home and intend to use them in some homebrew, take note:  the picked hops need to be dried down to about 30% of their original weight; roughly 8-10% moisture.  So with improper hop production and storage influencing grassy flavor production, it stands to reason then, that these conditions could also lead to isovaleric acid production. All things being equal, however, the cheesiness of isovaleric acid will probably be noticed before the grassy flavors, since not only does isovaleric acid have a lower threshold than c-3-h (1ppm vs. 15ppm) but the source material for isovaleric acid (humulone; one of 3 alpha acids) is likely at a higher initial concentration than the various poly-unsaturated fatty acids (total fat content averages around 3% of the weight of hops).

There aren’t too many beers that I can think of that are heavy in grassy flavors, but I would hazard a guess that you are more likely to find them in European pilsners and lagers as they tend to be lighter in flavor (meaning they can’t hide defects as well) and they tend to use the traditional nobel hops which are used as aroma hops rather than bittering hops. This means, among other things, less source material for isovaleric acid production, as well as poorer storability and higher tendency to oxidize.

If anybody knows of any commercial beers which seem to be grassy in character, I’d love to hear from you. Shoot me an email through the “Contact” link above and I’ll see if I can track any down. For now, all my grassy beer is made by me, my stock solution of cis-3-hexenol, and my pipette.


[edit:  3/3/11, 12:53 EST, added language about hop drying.]

Black Gold and Hop Henge: Two delicious Oregon beers

This week we had two guest beers on taste panel which were really quite nice. One of them even obtained the coveted “Defect-Free?” title which really hasn’t been handed out by our panel before that I recall. Quite a refreshing experience.

First, the Imperial Stout from Full Sail Brewing. This was the beer that the panel could find no appreciable defects in. It was smooth, flavorful, balanced (as Imperial Stouts go), and really quite nice. This beer was apparently aged in bourbon barrels for 10 months, and it shows. Very complex and alcoholic bourbon/whiskey flavors, deep roasted malt characters, and a stomach-warming 11.4% abv. If you like stouts and you enjoy those rich flavors that come along with bourbon-barrel aging, this should be your beer.

Bourbon Barrel

Another beer we had this week makes regular appearances in my fridge at home. It’s my go-to IPA at the moment, since it hasn’t let me down yet. Deschutes Brewing’s Hop Henge Experimental IPA. Not sure what’s experimental about it, unless they are trying to see how much of it they can get me to buy. This IPA is not light on malt flavors, but the crown jewel of this beer is its immense floral and green-hop aromas. And at 9% abv, it’s rather deceptive; it really doesn’t present itself as having that much alcohol. Balanced, refreshing, and tasty, I’ll be coming back to this one next year (it’s one of 3 Bond St. Series IPA’s on seasonal rotation).

Resinous, Green Hop Aroma
Isoamyl acetate

Drink up!

Beeeer iiiinnn Spaaaaaaace!

Not sensory related (necessarily), but cool nonetheless.

Found a pretty cool article about a new beer which has been developed specifically for consumption in a weightless or microgravity environment.


Astronauts4Hire Flight Member Todd Romberger was selected to perform the flight research. Todd sampled the beer during 12 microgravity parabolas, each reproducing the weightless conditions of space for 30 seconds at a time, and recorded qualitative data on beverage taste and drinkability as well as biometric data to gain a first look at alcohol effects the body.

I’d be interested in finding out what kind of qualitative data they collected and how they recorded “drinkability”. Seems that, for 30 seconds at a time, drinkability (as difficult as it already is to define) would be hard to accurately describe.

Here’s some other interesting information about the project, from someone who was involved with it directly:

The beer is a stout that is brewed for low carbonation and powerful flavor. If the carbonation content is too high, it can cause stomach discomfort in the astronauts/space flight participants because the bubbles can’t go anywhere. This can lead to wet burps (basically throwing up a little bit in the back of your throat, only worse).
The flavor is powerful because of your body’s fluid shift. Without the pull of gravity, blood pressure in the head increases, and astronauts often have a headache in the first day or so until their body equilibrates. However, your senses of taste and smell are numbed compared to while you’re on Earth. In space, astronauts cover everything in hot sauce just so they can taste something. This beer makes up for the numbed taste by increasing the flavor.
The purpose of the experiment was to see what the difference was between the ground taste test and the microgravity taste test (among many other variables). The results are being presented tomorrow afternoon at the Next-Generation Suborbital Researcher’s Conference.