Dear Mr. Wizard,

Last week I brewed a German Alt using Wyeast 1007. It’s been fermenting at 58° F for 9 days now and it’s nearing the end of the primary. I will then transfer it into a keg and let it condition for about 8 weeks. My question deals with diacetyl. Normally this is associated with lager strains, but I’m wondering if I have to worry about it with these special low temperature ale yeasts? Is diacetyl only associated with lagers or is the temperature more of a key factor?

Michael Kesler
Milwaukee, Wisconsin

Mr. Wizard replies:

The real question at issue is not whether diacetyl is only associated with lagers, but rather if it is only unacceptable in lagers. Diacetyl is naturally found in all beers during fermentation and some beers can contain perceptible levels of diacetyl after aging. Diacetyl, also known as 2,3 butanedione, is produced outside of the yeast cell when the compound alpha-acetolactate is oxidized by metal ions or dissolved oxygen. During aging, yeast cells absorb diacetyl, use it as a hydrogen donor in biochemical reactions and in the process convert into a flavorless alcohol called 2,3 butanediol.

Style gurus all agree that diacetyl should never be found in lagers. Its presence is a sign of insufficient aging and is simply not acceptable in a type of beer named after its long, cold storage! Diacetyl can also originate from beer spoilage bacteria, especially Pediococcus, and any off-flavor associated with bacterial contamination is bad, regardless of the fermenting strain. ("Wild beers", such as lambics, are of course held to a different set of rules.)

Oddly enough, if you asked the question what is the easiest type of beer to brew without having to worry much about diacetyl, I would answer lager. In a classic lager fermentation there is plenty of time for diacetyl to be produced from alpha acetolactate and for yeast to absorb diacetyl and reduce it to 2,3 butanediol. The fact that lager yeast strains are typically less flocculent than ale strains also helps since contact between the yeast cell and beer is essential for beer-yeast interactions to occur. Although Alt yeast is an ale strain, it is very non-flocculent and the cool, protracted method used to produce Alt beers makes Alts more similar to lagers with respect to yeast behavior and fermentation technique than ales. In other words, I would not worry much about diacetyl in your Alt.

Thanks to advances in brewing science over the past few decades, diacetyl is very well understood. The underlying biochemistry has allowed brewers to accelerate the aging process by manipulating beer temperature after fermentation. This has become known as the "diacetyl rest". The diacetyl rest is a step in the fermentation process designed to reduce diacetyl levels. Some breweries have gone as far as to use immobilized yeast to speed up aging by increasing the contact between yeast and beer. Globally, the result of this understanding has been a dramatic reduction in diacetyl levels in all sorts of beers.

Diacetyl is one of those compounds some people really like in small doses because it adds to the complexity of some beer (and wine) styles. Most brewers see it as a defect because of its association with beer spoilage organisms as well as its satiating effect on the consumer. For those brewers who wish to get more diacetyl in your beers, take the opposite route of alt brewing. Use a flocculent yeast, room temperature fermentation, short aging and good racking techniques to minimize the amount of yeast carried into the bottle.

Dear Mr. Wizard,

Could you please cover the major types and strains of barley used in brewing? I often see recipes that call for specific types of barley, such as Harrington two-row. Others specify Klages. I understand these are barley varieties, and not brand names. It would be good to know which varieties are present in various brands of malt.

Also, I sometimes see articles, as in the case of Michael Jackson’s article on Bitburger beer in his "Beer Companion," which say things like "only spring barley is used." So I guess barley is harvested during different seasons?

Bill Wible
Philadelphia, Pennsylvania

Mr. Wizard replies:

Wow! This is a huge question that is answered in terms of books and journals. I will try to cover the basics of malting barley varieties, but my answer is a very small tip of a very large iceberg!

Barley grown for brewers malt is called malting barley, as opposed to feed barley, and is divided into two general types; 2-row and 6-row. The most obvious difference between a head of 2-row barley and a head of 6-row barley is the arrangement of the kernels when the head is viewed down its axis. Brewers don’t make a big deal about 2-row versus 6-row barley based on the appearance of the barley head, however. The significant differences are found upon closer examination. In general, 6-row malted barley has more protein and enzyme content than 2-row malted barley, is thinner than two-row malt and contains less carbohydrate. There are also flavor differences between 2-row and 6-row and it seems that most brewers feel 2-row malt produces a fuller, maltier flavor and 6-row malt produces a grainier flavor in the finished beer.

The interesting fact about 6-row barley is that it is only grown in North America. Its high enzyme concentration after malting is one of the reasons cereal adjuncts like rice and corn can be used without causing problems with mash conversion. The other thing about 6-row barley is that it has become a symbol of what the European brewers don’t use. Just read the marketing materials of many imports and you will find references to the exclusive use of 2-row malted barley, implying that there is something inferior to 6-row malting barley. I don’t share that opinion since 6-row malt certainly has its place in brewing.

Barley can also be further categorized by when it is sown in the field. Spring varieties are sown in the spring and harvested in the fall. Winter varieties, on the other hand, are sown in the fall or winter and harvested in late spring. Winter varieties are said to over-winter because they don’t germinate and grow into plants until the following spring. This is like planting bulbs in the fall for spring flowers. These different varieties are perhaps more significant to farmers being able to optimize their land than they are to brewers making different beers from Spring and Winter barleys.

The most important thing to remember when considering why certain barley varieties are grown is the barley farmer. There always has been and will continue to be a very careful balance between what maltsters want in their barley and what farmers are willing to produce. Planting a field of malting barley can be a very poor decision for farmers if the crop does not meet the specifications of the maltster. Rejected crops are sold as feed barley for a much lower price. To further increase the risk, malting varieties typically have a lower yield per acre than feed barley.

A good barley variety has good yield per acre, is disease resistant, does not have a tendency to lodge (fall over and make harvesting impossible) and does not shatter (the kernels fall out of the head onto the ground). Other traits include water requirements and ripening date. Harvesting becomes difficult during fall or spring rains, depending on the growing region because combines don’t do too well in muddy fields.

The maltster has a different set of concerns. In a nutshell, the maltster wants a barley with excellent uniformity that is easy to germinate and modifies evenly during germination. Certain varieties require a considerable amount of coaxing in the malt house, for example in the steeping and aerating regimen, than others. If you are a maltster you don’t want barley that makes your life difficult.

Finally, there is the brewer. We want malt that makes good beer. Of course each brewer has different needs and the prudent brewer goes to a great deal of effort to ensure barley farmers and maltsters are producing malt to suit their needs. The only brewers with this sort of clout are the really big boys. These brewers also support barley-breeding programs. Other brewers rely on groups like the American Malting Barley Association to recommend and approve barley varieties for malting based upon their brewing properties.

North American barley farmers grow both 2- and 6-row varieties. Examples of 2-row varieties include Klages, Harrington, B1202 (a variety developed by Anheuser-Busch) and numerous varieties of Coors’ Moravian barley (for example, Moravian III). Six-row varieties include Morex, Russell, Excel, Robust and Stander. These are all spring barley varieties, which is the norm for North American malting barley varieties. The Europeans only grow 2-row barley. Examples of European spring barley include Chariot, Alexis, Hana, Ferment, Steffi, Krona and Sissi. Winter varieties, mainly grown in England, include Maris Otter, Halcyon and Pipkin.

Of the varieties listed in this short listing, there are only a few we as brewers ever hear mentioned. Klages is arguably the most noted American variety among home and craft brewers. It was a very prominent variety grown in the West, especially in Idaho, and was prized by maltsters for its excellent malting properties. Harrington and B1202 have largely replaced Klages acreage because these varieties have better agronomic properties. Maris Otter is prized for its excellent malting and brewing properties in England and Hana is one the prized varieties used in the production of the lightly modified Czech malts.

So how does the homebrewer use this information when it comes to buying malt? For starters, I would not worry too much about hunting down a certain barely variety for a given recipe unless the variety is readily available as a "straight" malt. Most maltsers blend varieties after malting in order to produce a consistent product for the brewer. The only malt widely marketed by barley variety is Maris Otter. The U.K. maltsters who produce and sell floor-malted Maris Otter also sell "floor-malted ale malt" that is a blend of Maris Otter, Pipkin and Halcyon. To convince me that a bag of malt is made exclusively from Klages, for example, I would require papers from the maltser in addition to the vendor’s description because Klages acreage is very, very low.

Usually, if the maltster wants the brewer to know what variety of barley is used in the malt they will advertise it. Oftentimes, brewers are less concerned about what variety is used and more concerned about the lab analysis (typically referred to as the malt "spec" or specification sheet). Malt specs give insight into modification, protein content and size, wort viscosity, beta-glucan content, color, enzymatic activity, extract yield, moisture content, hardness or "friability" and aroma. This is why many malts are described by the type of beer they are intended to be used in, for example ale, pilsner, lager and stout malts, instead of the variety of barley used to make the malt. Big brewers are very concerned about malt specs and maltsters must produce malts to meet their specs. Malsters typically accomplish this by blending various malts.

In practical terms, this means if you buy pale malt from a large malting company it has been designed to meet the specs of a large brewer because that’s where the big malting companies make their money. If you want to brew beers with malts made with known varieties or single varieties, I would start by researching malt produced by smaller malting companies. Many small maltsers have Web-sites that contain very good information about the varieties of barley they typically use. Some of these companies have U.S. sales representatives that will personally respond to questions about variety. You can then experiment with known varieties and determine how variety affects your beer.