The Growth of Wood
Professional brewers also use wood or liquor-infused wood barrels to flavor their beer. Homebrewers can use wood in their brew, too.
Barrels
Historically, most things were shipped in barrels, whether overland or by sea. The cooper (or barrelmaker) was a respected tradesman and the last name of Cooper still exists to show us just how far back the trade goes. It made sense. There certainly weren’t any plastics, there weren’t the skills at metallurgy we have today, and the technology for bottling carbonated beer didn’t really exist until the latter part of the last century.
A barrel protects goods much better than a sack and, if made to the proper specifications, can hold liquid. And you know from drawings, paintings, and accounts that the wooden barrel was the standard for beer delivery. The question remains whether the character of the beer was affected by the barrel — and should it be?
In the past, wine was stored in barrels for the same reasons as beer. They were the standard medium of storage. Today, most wines that are aged in wood are aged in oak for the flavor characteristics this storage imparts. However, there are many wines that never see an oak cask and many wineries where you will never see an oak barrel. Furthermore, not all wine aged in barrels picks up flavor from the barrel, even if it’s an oak barrel.
Barrels that have been used many times do not impart any flavor directly from the wood itself. Many wineries use these old barrels because they are already on hand, and that’s cheaper than buying a new stainless steel tank. However, unlike in the past, almost all present-day wine barrels are made of oak — usually French or American but sometimes German or Hungarian — and are used to impart flavor to the wine when new.
Wood by Any Other Name
Not all oak species have the same flavor characteristics or even any flavor at all. The differences in flavors between French and American oaks are significant, but it is important to note that central and eastern European oak species are very neutral.
Historically, wood of the Quercus species (oak) was not the only wood used in beverage storage and aging. During the last century in California, and even into the 1920s and ’30s, many wineries had cooperage made of redwood. Those old-growth forests were just ripe for cutting to make quick, convenient, and cheap barrels. Some barrels were open-top numbers the size of a house. Gallo winery still has a whole cellar full of them.
Redwood imparts no flavor characteristics to liquids; it was just cheap and convenient. But now it’s all but gone. Not all wood is good or even neutral.
The Greeks stored their wine in pine barrels. Pine sap has a very distinct aroma (and flavor) and is the key flavor component of the Greek wine now known as Retsina. Those who have consumed this stuff agree that it’s an acquired taste, and it’s no wonder that beer in wood never caught on there.
Another wood associated with brewing is beechwood. You may have heard the term “beechwood aged” and thought that the beer was aged in barrels of beechwood. Actually, in this case the beechwood is in the form of chips or staves that have been boiled and bleached and piled into the aging tank to help keep the yeast in solution. The yeast lodges onto the stacked pieces of beechwood instead of dropping to the bottom of the tank and being covered by still more yeast.
As you might guess, bleaching and boiling a piece of wood removes any flavor character the piece might have. So beechwood is added to improve the process and not impart character.
Flavor Characteristics
Some flavors you can expect from oak aging are vanilla and toasty characteristics. The toasty may range from literally a melba toast aroma to something akin to roasted marshmallow or butterscotch, depending on the treatment of the oak. Some perceived sweetness may be involved, and caramelly notes would also be possible. There may also be astringency from the wood, especially if wood chips are used.
The flavor compounds you can expect from the wood are essentially all of the class of compounds known as phenols. Phenolic compounds make up a huge class of organic compounds that are found in such diverse elements as spice flavorings like curcumin (from turmeric), vanilla, and wintergreen, to things such as poison oak and marijuana, to medicines such as aspirin and tetracycline. Beta-lupulone is a phenol (it’s a beta acid resin found in hops).
In fact one of the most predominant phenolic flavorings found in oak is vanillin, the phenolic component of vanilla flavoring. Vanillin is much more predominant in American oak than in French oak. Winemakers spend an inordinate amount of time discussing the merits of each. Although most American oak delivers the same flavors, the flavor of French oak can vary depending on where in France it grows. Winemakers even debate which part of the Allier forest yields the best barrels.
Flavors imparted by the barrel can be influenced by how the wood was treated and aged before it was made into a barrel. Also important to the flavor imparted by the wood is what’s called the char or “toast.” This is the degree to which the wooden staves have been burned inside the barrel. This is usually broken down into one of three categories: light, medium, and dark. Obviously, a dark toast barrel will provide more color and more caramel-type flavors than a light toast. Classic American bourbon whiskey is made with American oak barrels with a dark or heavy toast.
Aging in Oak
If you want to try giving your beer oak flavor, the best method is to use a small barrel.
Make absolutely sure that the barrels are clean and sanitized. Cleaning with steam is a good option. If you find a used one you want to try to resurrect, you may need to rehydrate it (by soaking) to bring it back to water-tight status.
An alternative to using barrels is to use oak chips, but choose your chips carefully. Avoid chips that closely resemble sawdust. These do not impart the best oak flavors. Try to purchase chips that are actual shavings: curled pieces of oak from barrel stave shapings.
Experiment with your additions, perhaps using one-half ounce of chips in one batch and one ounce in another. Other factors to experiment with include aging time and temperature as well as style of beer.
Remember that the oak flavors should complement or accent flavors in the beer. Generally darker, full-bodied and higher alcohol beers are compatable with oaking, because many of the negative characteristics associated with aging in oak are masked in these beers due to the malt profile. Chips may cause more astringent flavors than oak barrels; beers that are high in IBUs may become too astringent.
When you sample your barrel-aged brew, if you find the flavor too strong, take a page out of the professional’s book and mix the oak-aged batch with a carboy-aged batch.
Keeping Tradition Alive
Some British styles of beer, such as Old Ale, are still either cask conditioned or bottle conditioned and corked. Gales Prize Old Ale is probably the best and best known example. These beers can have very characteristic flavors and aromas of acetaldehyde (green apple) and malt vinegar and can be quite sour. There is some evidence that these characteristics may diminish as the bottle ages.
At Traquair House in Scotland, the old mash tun is actually made of wood. Other British breweries still release beer to “the trades” in wooden casks. A portion of Wadsworth 6X and Samuel Smith real ale is conditioned in wooden casks. The portion is then combined with beer not conditioned in a wooden cask.
Steve Parkes, head brewer and lead instructor for the American Brewers Guild, worked for several UK brewers making traditional ales before his move to the United States. According to Parkes, the British brewers aren’t interested in getting flavor from the barrel itself and, in fact, do just about everything they can to eliminate any flavors from their wooden firkins.
Many Czech breweries use wooden fermenters. And of course, you can’t forget the Belgians and particularly the monks that live and brew there! It would be tough to find an abbey beer that hasn’t done some time in a barrel. Some of the styles and brands are actually three or four different “beers” blended together. Most are flavored by bacteria and wild yeast. Some of the beer may have been in oak barrels for as long as two years.
In the United States the Firestone Walker Brewing Co., Los Olivos, Calif., uses an open-barrel fermentation system for its Double Barrel Ale. According to Head Brewer Christian August, the object of using barrels at Firestone Walker is to impart wood flavor to the beer. The brewery uses new American oak barrels for fermentation. These barrels see about a solid month of use, then get rotated out.
Not all the beer goes through oak fermentation. August says that the total amounts to less than 20 percent. It was found that any more than that gave the beer too much oak flavor. The beer is pulled off the casks at peak kraeusen (the height of fermentation) and blended into lagering tanks.
Firestone Walker uses a medium toast, which the brewers found gave them the flavor they were looking for. They tried oak chips but found that the chips gave a very different character to the beer than the barrels did. August did some investigating and found that barrel companies use a very low quality oak for their chips and, to a certain extent, for their smaller oak barrels as well.
Other US regional breweries use wooden barrels for open fermentation. These include the Minnesota Brewing Co., St. Paul, Minn., and Lion Brewery in Wilkes-Barre, Pa.
Ghosts of Drinks Past
American microbreweries, such as Denver’s Rock Bottom and the Denver Chop House and Brewery (also owned by Rock Bottom Restaurants), are experimenting with a process that the Scots have used for centuries: aging your product in a barrel that once held something else. Just as the Scots have long aged their “water of life,” Scotch whisky, in barrels that once held sherry, port, or bourbon whiskey, American microbrewers are doing the same with their beer.
“Mega-micro” brewery Boston Beer Co. ages its Sam Adams Triple Bock in bourbon barrels, and other breweries are using whisky and wine (such as Cabernet Sauvignon) barrels. As you might expect, the beer takes on much of the flavor characteristics of the previous liquid that was in the barrel.
Storing Beer in Barrels
Beer was stored in wood when there were no alternatives. Today brewers choose to use stainless steel and glass instead of wood for good reason. Other than the possibility of the beer taking on some characteristics of the wood itself or what the barrel once held — which is sometimes desired, depending on your recipe — there are oxidative and microbiological dangers in storing beer in barrels.
Wooden barrels don’t keep air away from the contained product as well as glass or metal. In fact in the case of most beverages, especially alcoholic beverages, there is evaporation. This is called in the distilling industry the “angel’s share” but is otherwise known as “ullage.” If you’ve ever been within 100 feet of a bonded distillery’s aging warehouse, you know about ullage. The alcohol fumes are very apparent. (The term “ullage” is also used in England to describe the spoiled beer that is returned to the brewery.)
Because wine and beer have a lower alcohol percentage than liquor, evaporation is not so dramatic. Winemakers keep extra wine — usually in glass carboys — with which to top off the barrels as the wine ages. Wine has a higher alcohol percentage (around 15 percent) than beer (around 5 percent), so evaporation is even less of a concern for beer makers. If you are planning to keep beer for a year or more in a barrel, you can plan to reserve beer for topping up, but it is really not necessary.
Brewers know that air picked up by the beer during processing or trapped in the bottle or keg during packaging will contribute to staling flavors and oxidative reactions. This is especially true in beers stored in wooden barrels. While topping up limits the headspace, the headspace in beer, as opposed to in wine, contains CO2 from the carbonation. If you are concerned about oxidation, you should not use wooden barrels.
Because barrels are exposed to oxygen and the beer is kept in what is known as an aerobic environment, it is also quite likely that the beer will be attacked by flor yeasts (the type that make sherry) or wild yeast species such as Brettanomyces or Dekkera. The latter two are very important in the flavors of some lambics and other Belgian beers but are normally considered spoilage organisms in most wine and beer.
The biggest potential spoiler in the quest to age beer in wood is Acetobacter, which essentially is responsible for turning beer into malt vinegar. There is also the danger that Pediococcus and Lactobacillus, two huge beer-spoiling bacteria genera, could get a foothold in the barrel.
Preparing the Barrels
Winemakers combat the problem of microbiological contamination in ways not open to homebrewers. But if you have picked up some of the marked-down items at your local discount liquor mart, you’ll know that not all winemakers are completely successful. However, winemakers do have several advantages over brewers in this regard.
First, wine generally has two to three times the alcohol content of beer. Alcohol is a great inhibitor of microorganisms. Second, wine generally has a pH of a full point or more lower than beer. Low pH (or an acidic environment) is a good inhibitor of microorganisms.
The winemaker’s most important weapon is sodium metabisulfite. Adding this is called “sulfuring the wine,” and any wine that isn’t certified organic has most likely had this added. The metabisulfite binds oxygen, which would have oxidized the wine, and also inhibits the growth of microorganisms.
In the past this compound was used in domestic beer (it can still be used abroad, especially in Third World beer). However, today there are strict limits for domestic use, and this compound can be smelled and tasted at much lower quantities in beer than in wine.
Typically, before a barrel is used for wine and each time it is emptied, the interior of the barrel itself receives burning sulfur smoke as well as any sulfur that may be added to the wine in the form of powdered metabisulfite.
According to Parkes, the wooden barrels used for cask ales in Britain did receive a massive dose of metabisufite after they were returned from the tavern, which would not legally be considered a direct addition to the beer. In addition, steam was applied directly to the interior of each cask until the outside of the cask was hot to the touch.
Rather than fool with metabisulfite and risk spoiling the flavor of your beer at home, try this steam-cleaning method if you wish to experiment with small wooden casks.
Experimentation
At one time the use of wood was a critical part of creating and storing beer. But because of the advances in materials technology, you probably are not interested in the barrels strictly as a medium for storage.
The lengths you need to go to procure one and the space needed to set it up for use almost require that you experiment with wood for the added complexity of flavors it will impart. But experimentation with wood may not be as foolproof as experimenting with a different variety of hops; there are negative flavor compounds associated with wood and there are fewer precedents to follow in your experimentations. Still, if you hit it right, you can have a toasty, vanilla taste of history.
