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.
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.]
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.
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