The following three articles below appeared in the magazine BREWING TECHNIQUES.
Belgian Malts: Some Practical Observations
by George J. Fix
Republished from BrewingTechniques' May/June 1993.
Belgian malts offer qualities and performance profiles that differ markedly from their North American and British counterparts. This reporty on the results from experimental test brews based on Belgian malts reveals their strengths and limitations and provides recommendations for their use.
Belgium and France contain selected areas prized for growing top-flight malting barley. The ancestors of the modern varieties grown there can be traced back to the Middle East, where barley was first cultivated and malted (albeit using a primitive process). The evolution of ancient to modern strains of this malting barley is similar to the evolution of Vinefera wine grapes grown in France. Both have been selectively cultivated over the centuries for the desirable flavors they impart to their host drink.
The existence of Belgian malts was noted two years ago in a book I coauthored on Vienna-style beer (1). At that time, these malts were unavailable in North America. Rumors, however, held that this situation would soon change, and we alerted readers that popular availability of Belgian malts could alter our recommendations for the best type of malt to use in Viennas (1). These malts have now been in widespread amateur and commercial use for over a year. The results have been highly favorable, influencing virtually all of the major beer styles, of which Vienna-style beers are but one example. (See the section on "Roasted Malts" for further discussion of the Vienna style.) Belgian malts have shown different characteristics from those of standard malts in terms of clarity of run-offs, color, yield, and other factors. This article discusses the implications of Belgian malt characteristics.
The Belgian grains that are available today are all malted at DeWolf-Cosyns in Brussels, Belgium. DeWolf-Cosyns is one of the oldest and most prestigious companies in Europe and is known for having uncompromising standards of malt quality. Although a relatively large company, DeWolf-Cosyns nevertheless continues to use the traditional floor malting process. Floor malting is very expensive, but it produces the best malt (2). Another positive aspect of DeWolf-Cosyns is the diversity of the malt types they produce. The company has long supplied Belgium's many specialty brewers with a variety of specialty malts. All of these malts are being imported and are currently available to North American brewers.
Yield -- the percentage of a malt's weight that is convertible to extract -- is an important consideration when evaluating malts. Most home brewers and some pub brewers work with gravity points instead of extract. These brewers typically define yield as the number of gravity points that are obtained for a given malt rate; this measure of yield is expressed in terms of points/pounds/gallon. The present study uses a standard percentage value for yields. The Plato tables enable us to relate these two measures. If a malt yields Y% of extract, then 1 lb/gal of this malt will yield Y/100 lb/gal of extract, or 31Y/100 lb/bbl of extract (1 bbl = 31 gal). The Plato tables show that wort containing 1 lb/gal or 31 lb/bbl of extract has a specific gravity of 1.046. The general equation for translating points to percent yield is therefore
points/lb/gal = 0.46Y
Thus, a 60% yield is equivalent to 28 pts/lb/gal, and a 70% yield is equivalent to 32 pts/lb/gal.
This article reports the results of various test brews. To standardize the reported results, the same wort production procedure was used for each (see box). When using North American pale two-row malts like Klages and Harrington, the standardized procedure typically produces yields of 62-64%, real degrees of fermentation of 63-65%, and apparent degrees of fermentation of 77-79%. The values obtained for the Belgian malts are presented below.
Standardized Wort Production Procedure
Total volume of water:
64 L of distilled water, into which 30g of calcium chloride was dissolved
Volume of mash water:
Volume of sparge water:
30 min at 52 degrees C, 30-min transition to 68 degrees C, 45 min at 68 degrees C, 5-min transition to 71 degrees C, 10 min at 71 degrees C
Volume of collected wort:
Volume of finished wort:
In Europe, Pils malt generally refers to malt made from top-quality, low-protein, two-row barley. It generally has modest diastatic powers, is quite pale in color, and is much less modified than ale malts. European lager brewers tend to prefer undermodified malt, partly because of tradition and partly because of the superior storage properties these malts are reported to have. Table I shows the data on the DeWolf-Cosyns' Pils malt.
The kernels are plump and uniform in size; there are virtually no small kernels. In fact, this is true of all of the malt discussed in this article, indicating uniform germination typical of floor malting systems. The Pils malt has much harder kernels than ale malts, which indicates that the latter are more modified. The degree of modification is evident when the malts are chewed or milled.
DeClerck found that the best protein levels for malted barley were in the 9-11% range (2). The DeWolf-Cosyns Pils malt falls in the middle of this range, which is ideal. It is important to note that few North American malts fall in the DeClerck range. Most two-row malt is 11.5-12.5% protein, and six-row malts are typically >12.5% protein. One feature of low-protein malts is their relatively low diastatic power, the measure of the grain's enzymatic strength; the higher the diastatic power, the stronger the malt's enzyme system. North American two-row malts typically have diastatic powers in the 125-135 degrees Lintner range, and six-row malts are stronger still. The Belgian Pils malt is roughly 25% below that. The enzyme system in the Belgian Pils malt is therefore not strong enough to convert the starch in a mash that contains a high fraction of adjuncts (here adjunct refers to any grain that has little or no enzymes, such as roasted malts and unmalted cereal grains). With a diastatic power slightly above 100 degrees Lintner, the Belgian Pils malt is capable of converting its own starch and perhaps a 15-20% adjunct level in the grain bill. Brewers should be cautious about using higher adjunct levels.
Low-protein malts also typically produce high yields, and the difference between fine- and coarse-grind yields is small. This is certainly true of the Belgian Pils malt. It should be noted that the numerical values for the yields cited in Table I were obtained under laboratory conditions. It is generally not possible -- or desirable -- to achieve these yields in practical brewing situations. The accompanying box (Test Brew #1) shows typical results achieved using my 50-L system.
Test Brew #1 -- Pils Malt
Grain bill: 10 kg of Pils malt Original extract: 13.1 P (1.053) Yield: 68.4% Mash pH: 5.3 Fermentation: Lager yeast W-206, 10 days at 10 degrees C, 2-day cooling to 4 degrees C Real extract: 4.5 P (1.018) Real degree of fermentation: 65% Apparent extract: 2.6 P (1.011) Apparent degree of fermentation: 80%
I found that decoction mashing produced a slightly higher yield and a slightly deeper color. Other than that, the differences between infusion and decoction mashes with this malt were not great.
S-methyl-methionine (SMM), the major dimethyl sulfide precursor in malt, usually provides a good indicator of the intensity of a beer's malty/sulfury taste (3). SMM levels, however, provide no clear indication of the character of these flavors (4). For example, malt from Midwestern North American six-row barley and German Pils malt typically both have SMM levels in the range of 8-10 micrograms/gram of malt, yet beer flavors from these malts differ dramatically. At the other extreme, top-quality pale ale malt from the UK typically has SMM levels in the 1-2 micrograms/gram range. These malts have been produced for ales in which sulfuric flavors of any kind -- good or bad -- are unwelcome. The Belgian Pils malt falls in the middle of these two extremes. It will impart some malty/sulfury flavors -- lager beer tends to be insipid without such flavor components -- but the effect is not as intense as when using German Pils malt. For lager brewers, SMM levels may be the key determiner when deciding which Pils malt to use. Many brewers may find the moderate SMM levels of the Belgian Pils malt to be a defect.
Another concern about Belgian Pils malt is its moisture content. Commercial criteria typically call for moisture levels to be <4% (2). Brewers using Belgian Pils malt should periodically check to make sure that the grain has not deteriorated. Grain deteriorization will reduce yields and introduce musty tones to the finished beer. It is also advisable to store these malts in a cool, low-humidity area to prevent further water uptake.
PALE ALE MALT
Ale brewers -- whether in the UK, Belgium, or North America -- have traditionally been fussy about the malt they use. The DeWolf-Cosyns pale ale malt was clearly produced with this fussiness in mind. It is a low-nitrogen (low-protein) malt, is well modified, and has minimal SMM levels. The high degree of modification is evident by chewing some kernels. They are almost as soft as marshmallows. Specific data are shown in Table I.
This malt's low diastatic power places definite limits on the amount of adjuncts that can be included with it in the grain bill (possibly no more than 10-15%). Notice that this malt has almost twice the coloring potential of the Pils malt; very little roasted malt is needed to give the finished beer a deep amber hue, if that is desired. The mashing schedule cited in the introduction was used in the pale ale test brew (see box, Test Brew #2). Given this malt's high degree of modification, the rest at 52 degrees C was likely redundant. Otherwise, its brewhouse performance was quite similar to that of the Pils malt.
Test Brew #2 -- Pale Ale Malt
Grain bill: 10 kg pale ale malt Original extract: 13.3 P (1.054) Yield: 68.8% Mash pH: 5.2 Fermentation: Ale yeast (Siebel/Crosby & Baker BRY-96), 5 days at 20 degrees C, 2-day cooling to 5 degrees C Real extract: 4.5 P (1.018) Real degree of fermentation: 66% Apparent extract: 2.5 P (1.010) Apparent degree of fermentation: 80%
The pale ale malt has a classic English character; it imparts a definite "maltiness" to the finished beer, yet sulfury effects are totally absent. Many people use ester levels as a discriminator between ales and lagers. I believe that this method is not strictly valid because certain lagers do well with a high ester profile, and conversely some ales do well with a subdued ester profile. A far better discriminator is the malt character of the finished beer. Lagers tend to be insipid without some hints of that Central European malty/sulfury flavor tone. On the other hand, I cannot think of a single ale style in which such flavors would be welcome. Ale brewers who agree with these observations will view the very low SMM levels of the DeWolf-Cosyns pale ale as advantageous.
A natural question to ask is how Belgian pale ale malt stacks up to the top English two-row malt, namely Maris Otter (Great Ryburgh, England). What follows may sound like a cop out, and it likely is, but I feel it is too close to call. Both are outstanding. In fact, malt data on each are remarkably similar, and actual brews indicate that their color and flavor contributions are similar as well. The best advice I can give is to let price and availability determine which malt you choose. Brewers will not regret a decision for either malt.
The same comments about moisture levels made for the Pils malt apply to the pale ale malt as well.
My interest in wheat beers goes back nearly a decade (5). At the time that I wrote Wheat Beers, no commercial wheat beers were brewed in North America, despite their popularity in Central Europe. Since that time, interest in wheat beers among both amateur and commercial brewers has grown tremendously in North America. The popularity of wheat beers for pub brewers has lead to what many regard as a new beer style, namely "wheat ales." One reason for the success of wheat beers is that selected varieties of domestic wheat have done well in both malting and brewing. In addition, excellent wheat malt has been imported from both the UK and Germany. To these riches can now be added a version from Belgium. The data on the Belgian wheat malt is shown in Table I.
The values for wheat malt extract on an "as is" basis ("wet" measured, in wort) are unavailable. The numbers reported for the dry basis will always be slightly higher. The extract values reported for the other malts in this article were all measured on an "as is" basis.
In his recent excellent book on wheat beers, Eric Warner cited the following criteria for wheat malt (6):
Extract (dry basis): >83%
Protein (dry basis): <12.5%
The Belgian wheat malt satisfies the first two but not the third. The fine-to-coarse grind difference is 2.5%, which slightly misses the mark. (All of the other Belgian base malts, however, were less than 2%.) This value is a traditional figure that, along with protein levels and other parameters, has been used as a measure of malt quality. The moisture level of this malt would also be regarded as unacceptable by most commercial brewers. This malt should definitely be checked during storage.
I am unable to report on the practical significance of these deficiencies. I have yet to use the malt in full-size 50-L brews. Pilot 5-L brews indicate that it performs perfectly fine. In this regard, the procedures and recipes in Warner's book can be highly recommended for this wheat malt.
Color malts are kilned at a higher temperature than base malts but are not roasted. The two color malts offered by DeWolf-Cosyns are excellent examples. Both have sufficient enzymes to convert their own starch, a fact I confirmed with 5-L pilot brews using the standardized mashing schedule described in the introduction. I tested the Munich and aromatic malts, each on a stand-alone basis. Both gave a negative iodine reaction after 45 min at 68 degrees C. Thus, both can be included in a grain bill at any level that is desired. These malts come not only with a strong color potential, but also with very special flavor and aroma profiles. I highly recommend Darryl Richman's article on page 34 of this magazine for further discussion of the use of Munich malts (7).
The critical data for Munich and aromatic malts are shown in Table I. The carbohydrate structure of these malts indicates a high fraction of 1-6 links (3). These links will not be broken by amylase enzymes in a normal mash. Consequently, these malts will always make significant contributions to the dextrin pool even if they are fully mashed. The Munich malt could be used on its own, and pilot brews indicate that a real degree of fermentation in the range of 45-55% will be achieved. Beers with elevated dextrin levels like this were common in traditional Munich brewing (7).
Aromatic malt, on the other hand, should be thought of as an adjunct malt to be used only in small amounts because of its high color and flavor potentials and its very high fine-to-coarse grind differences.
Moisture levels of highly kilned malts are typically half that of pale malts (2). This is not the case for these color malts -- a problem that seems to be present with all of the Belgian malts. Again, it is important to store these malts in a cool, dry environment and to check them periodically for deterioration.
None of the roasted malts have enzymes. Therefore, their starch will have to be converted by enzymes from the other malts used. In my opinion, these malts are the gems of the Belgian collection. There are reasonable substitutes for the other malts discussed in this article, but these malts have no equal. I discuss them in three separate groups. Their profile data are shown in Table II.
The first group comprises Caramel Pils, Cara-Vienne, Cara-Munich, and Special B malts. The Cara-Vienne malt has the most attractive caramel-sweet aroma that I have ever encountered in a malt. It leaves an extremely pleasant tone in the finished beer. The accompanying box shows the results of a test brew based on our currently preferred version of the standard Vienna style. This version is not as malty as those based on German malts, but its finish is a good deal more elegant.
Test Brew #3 --Cara-Vienne Malt
Grain bill: 9 kg Belgian Pils malt, 1 kg Cara-Vienne, 0.5 kg Special B Original extract: 13.5 P (1.055) Yield: 67.8% Mash pH: 5.2 Fermentation: Lager yeast W-34/70, 9 days at 10 deg. C, 2-day cooling to 4 deg. C Real extract: 5.0 P (1.020) Real degree of fermentation: 63% Apparent extract: 3.0 P (1.012) Apparent degree of fermentation: 77.8% Beer color: 9 degrees L
What the Judges* Say about
Cara-Vienne-Based Oktoberfest (Test Brew #3)
Bouquet/Aroma: Good malt aroma; very slight diacetyl bouquet and aroma, true to style
Appearance: Excellent deep amber color; good clarity; good head retention; lace is good
Flavor: Very malty, appropriate for style; good balance for style; good carbonation; alcohol level appropriately high
Overall Impression: Wonderful beer; I can't find a flaw; gimme more!
*New England Competition, Westport, Massachusetts, 27 February 1993; event sanctioned by the Home Wine & Beer Trade Association and American Homebrewers Association.
The next malts -- chocolate malt, roasted barley, and roasted malt -- are the heavily roasted black malts. Chocolate malt is distinguished from the others because it has been debittered; thus, it will not impart that burnt coffee taste that highly roasted malts sometimes do. That taste, of course, can be either desirable or undesirable, depending on the beer style.
The last of the roasted malts to be discussed is the Biscuit malt. Simply chewing some kernels will give you a clear indication why this malt is so named. I haven't the slightest idea how this malt might be used in a recipe, other than the intuitive feeling that someone might create an entirely new beer style with it. It is interesting to note that DeClerck often used the descriptor "biscuit flavored" to characterize roasted malts (2). This malt makes such characterizations fully explicit.
Most European malts have much higher lipid levels than North American malts, and the Belgian malts have some of the highest lipid levels in Europe. High lipid levels will be readily apparent to the brewer by the type of run-offs observed during the sparge. Run-offs from Belgian malts will be considerably more turbid than would those of North American malts, and they require far more recirculation to achieve full wort clarity.
This raises the issue, widely discussed by writers in both the amateur and commercial literatures, of how important it is to achieve completely clear run-off into the kettle (3). Although such a large issue cannot be resolved in an article such as this, I noted the following features in my experience brewing with Belgian malts:
Finished beer clarity will not be adversely affected by turbid run-offs. In fact, if a flocculent yeast strain is used, the beer will fall brilliantly clear after only a brief postfermentation storage.
Beers that have been made with fully clarified worts show a greater stability in terms of chill haze and a longer shelf life in terms of staling. Brewers of mildly flavored beers report a stronger preference for beers made from clarified worts, while brewers of bigger beers report the reverse.
The lipid carryover to the fermentor has beneficial effects on yeast metabolism.
Commercial brewers of bottled beer, whose products are expected to have a shelf life of 4-6 months under market conditions, may be reluctant to use these malts because of their high lipid content. Others may come to different conclusions.
(1) G.J. Fix and L.A. Fix, Vienna (Brewers Publications, Boulder, Colorado, 1991).
(2) J. DeClerck, A Textbook of Brewing, Vol. 1 (Chapman and Hall, London, 1957).
(3) G.J. Fix, Principles of Brewing Science (Brewers Publications, Boulder, Colorado, 1989).
(4) G.J. Fix, "Sulfur Flavors in Beer," Zymurgy 15 (2) (1992).
(5) G.J. Fix, "Wheat Beers," Amateur Brewer 11 (1984).
(6) Eric Warner, German Wheat Beer (Brewers Publications, Boulder, Colorado, 1992).
(7) Darryl Richman, "Thinking about Beer Recipe Formulation," BrewingTechniques 1 (1), 34-35 (1993).
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Diacetyl: Formation, Reduction, and Control
by George J. Fix
Republished from BrewingTechniques' July/August 1993.
Diacetyl -- the compound responsible for buttery or butterscotch flavors that sometimes arise in beer -- can be controlled if you understand the mechanisms that contribute to its production. This review of the basic processes behind diacetyl formation and reduction will help you understand how to keep the diacetyl level in your beer at or below the acceptance threshold for the style.
Diacetyl and 2,3-pentanedione are important contributors to beer flavor and aroma. Organic chemists classify both as ketones, and diacetyl is usually called 2,3-butanedione in the literature (1). Sometimes these two ketones are grouped and reported as the vicinal diketone (VDK) content of beer (2).
Brewers' awareness and acceptance of both diacetyl and 2,3-pentanedione have changed dramatically over the past four to five decades. A 1952 report, for example, stated that the average diacetyl level of American commercial beer was 0.33 mg/L, more than three times the flavor threshold of 0.10 mg/L (3). Today the average is near 0.05 mg/L (4). Some notable exceptions exist. Some stouts can have levels as high as 0.60 mg/L, and a few British pale ales have diacetyl levels near 0.30 mg/L. Diacetyl levels in beers brewed by microbreweries and brewpubs tend to vary considerably, ranging from 0.03 mg/L to more than 1.0 mg/L in cases I have investigated.
The presence of diacetyl is usually indicated by a buttery or butterscotch tone. In fresh beer the flavor can be confused with that of caramel malts. Given time it is easy to distinguish the two; diacetyl tends to be unstable in most beers and can take on raunchy notes. The flavoring imparted by caramel malts, on the other hand, tends to be stable.
The flavor threshold of 2,3-pentanedione is near 1.0 mg/L; it usually imparts flavors that recall honey. This compound can be found well above threshold levels in some Belgian ales, where it is considered a natural flavor constituent for this style. It occurs less often in other beer styles and is regarded as a defect.
Figure 1. Pathway of diacetyl formation
DIACETYL FORMATION AND REDUCTION
The study of diacetyl and beer began with Pasteur's fundamental work in the 1870s (5). Using microscopy, Pasteur found that what we know today as lactic acid bacteria were responsible for many off-flavors in beer. The term sarcina sickness is used to describe this effect. Apparently, the involvement of diacetyl in sarcina sickness was discovered early, but it was not until 1939 that Shimwell linked this compound with the taste and smell of butter (6). Earlier studies got the organic chemistry right but were wide of the mark in terms of flavor chemistry (7). Even today it is estimated that 20% of beer drinkers do not detect the presence of diacetyl even at rather high concentrations (8).
During the early period, the only known mechanism of diacetyl formation was bacterial infection caused by unsanitary conditions. Practical brewers believed that some other factor must be involved, because buttery tones occasionally showed up in beer brewed in impeccably clean environments. Major breakthroughs occurred during the 1950s and early 1960s. J. Owades developed an effective technique for measuring diacetyl and used this method to study the fate of the compound in brewing (9). This work pointed to culture yeast as a major player in both the production and the reduction of diacetyl. Inoue and his colleagues at the Kirin Research Laboratory in Japan also made a major contribution by identifying acetolactic acid as the precursor to diacetyl (10). This work was followed by a large number of papers in which various facets of diacetyl formation and reduction were studied. Wainwright's excellent 1973 review article contains 149 references (11).
Although a number of factors affect diacetyl formation in beer, the basic middle pathway shown in Figure 1 is the one used for each. The dominant carbon flows down the leftmost branch, leading to ethanol production. Most beers contain between 30,000 and 50,000 mg/L of ethanol, so a significant amount of pyruvate is processed in this manner. Because the flavor threshold for diacetyl is 0.10 mg/L, a slight diversion of the carbon flow to the middle pathway can profoundly affect the flavor of finished beers. Note that this pathway also competes with yeast assimilation and the utilization of the amino acid valine. The practical significance of this is discussed in the section "Wort and Proteins" below.
A similar pathway is involved in the production of 2,3-pentanedione, except that different compounds are involved. The precursor is acetohydroxybutyrate, and the competing amino acid is leucine.
A number of factors lead to diacetyl formation, but only one reliable method can reduce diacetyl levels: enzymatical reduction by yeast (Figure 2). Acetoin, the intermediate product, has a rather unpleasant, musty taste, but because it has a flavor threshold of 3.0 mg/L its effect is not nearly as damaging to beer flavors as an equivalent amount of diacetyl. The final product, butanediol, is neutral as far as beer flavor is concerned.
Figure 2. Pathway of enzymatic reduction of diacetyl by yeast
THE EFFECT OF YEAST
As noted above, brewer's yeast contains enzymes for both producing and reducing diacetyl. Various yeast strains differ dramatically in this regard. The data in Table I were compiled for a book I am writing (12). Three lager strains were tested. The strains W-206 and W-34/70 are regarded as excellent reducers. The third strain, W-308, is less reliable (13), and the data in Table I document one of its less inspiring efforts. Sterile wort was fermented in each case at 10 degrees C (50 degrees F), and the diacetyl was measured using high performance liquid chromatography (HPLC).
Diacetyl formation in three yeast strains.
Day Diacetyl Level (mg/L)
W-206 W-34/70 W-308
1 .18 .15 .18
3 .25 .20 .48
5 .23 .18 .92
7 .18 .14 .75
9 .14 .09 .65
Highly flocculent yeast usually behave much like W-308 and can leave perceptible levels of diacetyl in beer, which is one reason why most commercial yeast strains are powdery and fully flocculate only after chilling. Yeast behavior for a given strain can also vary with reuse. The data in Table II were reported by Hoffmann for an unspecified lager strain (14).
Diacetyl levels for a larger strain
Day Diacetyl Level (mg/L)
first second third fourth
gen. gen. gen. gen.
1 .15 .16 .28 .36
3 .19 .36 .47 .65
5 .16 .29 .39 .60
7 .12 .23 .28 .40
In my experience, increases in the diacetyl formed with repitching, such as those reported above, parallel increases in the level of respiratory-deficient mutants in the pitching yeast. These mutants are strong producers of diacetyl and have lost their ability to reduce diacetyl. The presence of Gram-positive bacteria also cannot be ruled out as contributors to diacetyl formation. Yeast that is free of those two defects usually displays better performance with reuse.
Diacetyl production and reduction are strongly influenced by temperature, and the rates for both increase as temperature increases. Thus, an ale fermented at 20 degrees C (68 degrees F) typically has a higher diacetyl peak than, say, a lager fermented at 10 degrees C (50 degrees F). The rate of diacetyl reduction, however, is much higher in the ale than in the lager, which is why most lager brewers prefer to get diacetyl levels below 0.10-0.15 mg/L at the end of the main fermentation. Some additional reduction occurs in cold storage, but at a very slow rate. For this reason, some brewers raise the temperature of a cold-fermented beer to 20 degrees C (68 degrees F) for a brief period following the end of the main fermentation, a practice that is usually called diacetyl rest.
One alternative is the so-called Narziss fermentation. In this procedure the first two-thirds of the fermentation is done at 8-10 degrees C (46-50 degrees F). During the final third of fermentation, the temperature is allowed to increase to 20 degrees C (68 degrees F), after which the beer is transferred to cold storage. Another alternative is to add freshly fermenting wort (kraeusen) to diacetyl-laden beer in cold storage.
The bacteria that can directly promote diacetyl production consist of Gram-positive cocci (Pediococci) and select strains of Gram-positive rods (Lactobacillus). The effect of using these bacteria is easy to identify -- both bacteria also produce lactic acid, and the net effect is a rather raunchy butter tone with an unmistakable acid aftertaste. In both amateur and commercial brewing of yesteryear, infections from unsanitary equipment were not uncommon. Today, with the availability of highly effective sanitizers, infections tend to occur only in sloppy and poorly managed operations. It has been my experience that in modern operations, infections, when they occur, happen through pitching yeast.
It is unnecessary for fully developed pitching yeast to be sterile. Practical experience has shown that as long as bacteria relevant to beer are kept below the level of 1-10 cells per 10 million yeast cells, the finished beer will remain unaffected (15). The situation is dramatically different in the initial stages of yeast propagation. Here, sterile conditions are needed, as is pure culture yeast. This is particularly true when propagating yeast from slants, but it also applies to starting up semidormant liquid yeast. It is relatively easy to measure bacterial levels, particularly for lactic acid bacteria (15), and hence there is little justification for leaving these matters to chance.
Care should be taken when using yeast that has been held in bulk storage. If culture yeast go dormant, they tend to excrete amino acids (16), which bacteria can use as a source of nitrogen. Low levels of bacteria can grow to unacceptably high levels by this means. The safest course is to store the yeast under a sterile wort cover, at a temperature as close to 0 degrees C (32 degrees F) as possible, and for as brief a period as possible.
WORT AND PROTEINS
The basic diacetyl formation pathway shows clearly the major role that amino acids play. Worts deficient in valine tend to lead to elevated diacetyl levels. A typical scenario is given in reference 2 (p.189). As long as a sufficient amount of valine is present, there will be a net reduction of diacetyl after it reaches a peak level. If the valine content is depleted prematurely, however, net diacetyl production will resume, leading to what has been called the "second diacetyl peak." Some of this extra diacetyl ultimately will be reduced, but invariably the finished beer will contain a higher diacetyl content than it would had the wort contained adequate valine. The same remarks apply to 2,3-pentanedione and leucine.
Both leucine and valine are regarded as critical amino acids because yeast usually cannot metabolize adequate replacements from other nitrogen sources if leucine and valine are missing. If sufficient amounts of proteins are to be available in the fermentation, they must come from wort; this in turn depends on the amount of malted grains used. High-quality malt used with reasonable mashing systems will yield wort that is rich in all the relevant amino acids.
Brewers use a single number to characterize the size of their wort's amino acid pool -- namely, its free amino nitrogen (FAN) level. This number is to wort amino acids what specific gravity (or percent extract) is to wort carbohydrates. High FAN levels mean adequate leucine and valine pools. Conversely, low FAN levels result in inadequate levels of leucine and valine.
An all-malt wort at 12 degrees P (SG = 1.048), for example, typically has a FAN level in the range of 300-325 mg/L. This level is considered ideal. A 10 degrees P (SG = 1.040) all-malt wort, on the other hand, has a FAN level near 250-270 mg/L -- generally regarded as adequate. However, if a third of the malt were replaced with an equivalent amount of unmalted cereal grains or sugar (or both), then the FAN level would fall to 165-180 mg/L, which is generally regarded as inadequate. Apart from economic considerations, this is one of the main reasons why large industrial brewers using high adjunct levels tend to favor high-gravity brewing. If the 10 degrees P wort with 33% adjuncts were concentrated to, say, a 14 degrees P wort, then the FAN level would increase to 230-250 mg/L. This is a major improvement over the dilute adjunct wort.
Reports have been published of various deficiencies in certain brands of malt extracts (17). It appears that, in general, the protein levels of wort produced from extracts are lower than those obtained from grain worts. These and related issues are discussed in an excellent article by Lodahl (18).
Although it is important that our wort have a sufficient amino acid pool, it is also important that our culture yeast be able to use this nitrogen source. The situation for leucine and valine is particularly critical because their uptake by brewing yeast is rather slow in general and incomplete in the case of dysfunctional yeast. Respiratory-deficient mutants represent an extreme example of this. In all such cases the inevitable result is elevated diacetyl levels.
One cannot overstate the importance of using appropriate media in propagating yeast. The instruction sheet that accompanies yeast slants sold by Siebel (Chicago, Illinois) states that propagation should be done with wort that is ". . . of a similar original gravity and composition to the major production brand." Many brewers use dilute, unhopped wort having a specific gravity of 1.020. Although opinions may differ about these two options, totally artificial media should be avoided. I recently did some tests with what is often called "baker's media." It consisted of a dextrose-sucrose solution enriched with mineral nutrients (19). Yeast propagated on this media showed excellent cell growth rates during propagation. Their performance in the main fermentation, however, was unacceptable. A major defect was an extremely slow and incomplete valine uptake. Diacetyl levels were always higher by at least a factor of 4 relative to yeast propagated with the Siebel procedure, and in one example the level was 10 times higher.
The reaction acetolactic acid -> diacetyl is of the redox type (2). Acetolactic acid is oxidized to diacetyl, and other constituents (for example, various aldehydes as well as wort-derived melanoidins and tannins) are reduced. In all of the mechanisms described so far in this article, this is done enzymatically by microbes, culture yeast, and, in adverse cases, by other guests in our worts. The reaction can occur nonenzymatically, however, in the presence of an appropriate oxidizing agent. Indeed, a widely observed but little discussed phenomenon occurs when diacetyl appears spontaneously in a beer that seemed to have normal flavors. Strong evidence indicates that this can occur when marginally dysfunctional yeast have been used in the main fermentation -- they tend not to metabolize all the acetolactic acid in the wort. The acetolactic acid spills over into the finished beer and later is oxidized to diacetyl. Mechanical abuse of packaged beer can promote this; headspace air is the oxidizing agent. Elevated temperatures augment the effect. I have seen cases in which wort constituents (melanoidins and tannins), oxidized on the hot side in wort production, were passed on to the final beer, only to play the role of oxidizer there.
Oxygen and diacetyl are linked in another way, in this case in a positive manner. Hoffmann has shown that inadequate oxygenation of chilled wort can lead to elevated diacetyl levels (14). In one of his test brews, the dissolved oxygen content of chilled wort was a mere 0.80 mg/L. The second brew had 10 times that amount (8.0 mg/L), which is a widely used value. To achieve this level of oxygenation, one typically must saturate chilled wort with direct oxygen injection. Hoffmann reported that after the seventh day of fermentation, the poorly oxygenated wort had a diacetyl level of 0.80 mg/L, whereas the level in the second brew was down to 0.20 mg/L.
Ironically, Hoffmann also reported that diacetyl levels increased again after dissolved oxygen levels exceeded 8.0 mg/L. I have found that the maximum amount of oxygen that can be dissolved in, say, a 12 degrees P wort (SG = 1.048) at 10 ¡C (50 degrees F) is 7.8 mg/L (12). The amount of dissolved oxygen decreases as either the temperature or the wort gravity increases. To get higher values one would have to use supersaturation procedures, which requires special equipment. Thus, small-scale brewers need not fear that too much oxygen has been dissolved in their chilled worts.
A UBIQUITOUS GUEST
It can probably be said that the extreme sensitivity that practical brewers tend to have for diacetyl flavors in beer results, in part, from the fact that virtually every aspect of brewing involves diacetyl formation or reduction. Opinions will probably always differ about the suitability of diacetyl flavor in various beer styles. Nevertheless, we should be all aware of how it can arise and how its level can be controlled.
(1) T.W.G. Solomons, Organic Chemistry (John Wiley and Sons, New York, 1984).
(2) G.J. Fix, Principles of Brewing Science (Brewers Publications, Boulder, Colorado, 1989).
(3) O.B. West, A.L. Lautenbach, and K. Becker, Am. Soc. Brew. Chem. Proceedings 81 (1952).
(4) A. Piendl, "Biere Aus Aller Welt," Brauindustrie, various issues.
(5) L. Pasteur, Etudes sur Biere (Gauthier-Villar, Paris, 1876).
(6) J.L. Shimwell and W.F. Kirkpatrick, J. Inst. Brew. 45 (1939).
(7) A. Zimmermann, Brauereibische Betriebslehre (self published, Buffalo, 1904).
(8) M.C. Meilgaard, MBAA Tech. Qr. 28 (1991).
(9) J.L. Owades, L. Maresca, and G. Rubin, Proceedings of the American Society of Brewing Chemists (American Society of Brewing Chemists, St. Paul, Minnesota, 1959).
(10) T. Inoue, Y. Yamamoto, E. Kobubo, and Y. Kuroiwa, "Report Research Labs," no. 16 (Kirin Brewing Co., Takasaki, Japan, 1973).
(11) T. Wainwright, J. Inst. Brew. 79 (1973).
(12) G.J. Fix, Principles of Brewing Science II: Practical Considerations (manuscript in preparation).
(13) G.J. Fix, Proceedings of the National Microbrewers and Pubbrewers Conference and Trade Show, New Orleans, 18-21 April 1993 (Institute for Brewing Studies, Boulder, Colorado).
(14) S. Hoffmann, Brauwelt International (Brauwelt/Verlag, Nuremburg, Germany, 1985). (15) G.J. Fix, Beer & Brewing 12 (Brewers Publications, Boulder, Colorado, 1992). (16) M.J. Lewis, Am. Soc. Brew. Chem. (1963).
(17) J. Paik, N.H. Low, and W.M. Ingledew, "Malt Extract: Relationship of Chemical Composition to Fermentability," J. Am. Soc. Brew. Chem. 49 (1991).
(18) M. Lodahl, "Malt Extracts: Cause for Concern," BrewingTechniques 1 (2), 26-28 (1993).
(19) G. Reed and T.W. Nagodawithana, Yeast Technology (Van Nostrand Reinhold, New York, 1991).
Explorations in Pre-Prohibition American Lagers
By George J. Fix
Republished from BrewingTechniques' May/June 1994.
Pre-Prohibition American lagers differed significantly from modern domestic pale lagers. A sampling of recipes from that era reveals higher flavor profiles and greater variety than we expect from this style today.
If one were to poll a representative group of beer enthusiasts, home brewers, and commercial microbrewers about preferred beer styles, it is likely that American lagers would fall near the bottom of their lists. Descriptors like "tasteless," "bland," and "thin" would probably be offered as reasons for the low rating. This puts North America in a somewhat unusual position of having the vast majority of its beer intellectuals not only critical of specific versions of its major indigenous beer style, but in fact highly critical of the style itself. Some evidence suggests that this attitude is spilling over to the general population; many of the major brands are showing negative growth rates, and just about all of the large industrial brewers are showing interest in specialty and seasonal beers.
It is interesting to reflect on how this particular situation arose. Many suggest that it is a matter of overexposure - beer lovers have become bored of so many versions of the same beer style. This does not explain, however, why the same phenomenon has not occurred in the United Kingdom, where bitters are the popular style, or in Central European countries, where continental lagers predominate.
I believe that modern American lagers reveal the legacy of Prohibition. Unlike other major brewing regions, North America had 13 years during which commercial beer production was banned. This period had deleterious effects on just about all aspects of American brewing, including the traditions that were established in the period from the 1850s to 1920.
This article illustrates the dramatic change in the American lager style by examining selected American lager formulations. These formulations were considered "mainstream" and enjoyed large sales volumes during the pre-Prohibition era, yet they differ substantially from modern American lagers in their flavor profiles.
This article confines the discussion to lager beer. Space limitations do not permit inclusion of ales, and indeed a complete survey of pre-Prohibition brewing would require an entire book to do it justice. A strong case can be made that the Golden Age of American ale brewing started in the l980s with the growth of microbrewing. The major thrust of this article is that the Golden Age of lagers occurred near the turn of the 20th century. Omitted also from this article is what historical references such as Wahl-Henius (1) call steam or common beer. These beers were fermented with lager yeast but at ale temperatures. This special style, indigenous to the United States, also deserves a full book (Brewers Publications [Boulder, Colorado] is preparing one for its Classic Beer Series).
PRE-PROHIBITION PALE LAGER
I came across the formulation shown in the accompanying box in the late l970s and have been brewing it on a regular basis ever since (2,3). Several variations of the basic recipe exist, but the one shown appears to be typical (see reference 4, page 38, for example).
This high-gravity lager may strike modern palates as a specialty beer. Nugey, however, notes that it was an everyday beer that " . . . had a very large sales volume . . ." (4). Before Prohibition, mainstream beer did not mean weak, flavorless beer.
Authenticity suggests that domestic six-row pale malt should be used, and I am constantly struck by how well six-row pale malt does in a formulation like this. According to Wahl-Henius, " . . . only six-row barleys of Manchusia type can be considered for the preparation of chill-proof beers . . ." (1). In my experience, however, I get the best results in this formulation using malt from a domestic two-row barley call Hannchen. This barley was once grown in the Columbia River and Blue Mountain counties of Oregon (6). Its genealogy can be traced back to Hanna, the classic Moravian barley. This barley variety was brought to the United States early in the 20th century (7), and it is reasonable to assume that it played an important role for quality-conscious turn-of-the-century brewers. Unfortunately, it is no longer cultivated. Brewers today wishing to work with a domestic two-row malt will have to settle for Klages or Harrington.
The primary feature that separates this beer from all-malt continental lagers is the use of flaked maize, an unmalted cereal grain. The flakes are hardly a cheap malt substitute. Indeed, they typically cost two to three times more than domestic malt, and they are even more expensive than premium imported malts. What one gets with this specialty grain is extra strength without the satiating effects of a high-gravity beer. Alcohol by itself is essentially tasteless. Nevertheless, it is a flavor carrier, enhancing the other active flavor components in a beer, as it does in this formulation. The maize also leaves a pleasant grain-like sweetness in the finished beer. The chief advantage that flakes have over corn grits or rice is that, unlike the latter, flakes do not require cooking at boiling temperatures to achieve gelatinization. Many feel that this is the key to the flakes' desirable flavoring (2).
The high hopping rate in this beer sharply distinguishes it from modern American lagers. Although neither Nugey nor Wahl-Henius were specific about the type of hop varieties used, it is likely that "imported hops" means continental noble varieties like Hallertauer Mittelfruh or Saaz. Turn-of-the-century Budweiser labels, for example, had the Saaz hop proudly displayed as one of its ingredients.
A good deal more uncertainty surrounds the domestic hops used. It is known that Clusters were popular among U.S. brewers. I find the flavoring of this hop to be quite crude, especially in formulations having a high hop profile like this one. In the past, I have used continental aroma hops exclusively. In recent years, however, I have obtained good results using domestic aroma hops like Crystal, Liberty, Mt. Hood, and Tettnanger (which are good but different from German Tettnangers).
Data reported in both Nugey and Wahl-Henius indicate that the turn-of-the-century lagers had higher residual extracts than the 5.5 °P shown for the formulation in the box. In fact, Nugey explicitly states that the real extract alcohol ratio should be no less than 1.3 and no more than 2.5 (4). In the above, it is 5.5/5 = 1.1. Those wishing to get to the historical values should omit the mash rest at 140 °F (60 °C) and go directly from 122 °F (50 °C) to 158 °F (70 °C), holding the latter for 45 min. This method gives a higher terminal gravity and slightly lower alcohol content. The net effect is to put the beer comfortably into the prescribed range, if that is what is desired. It will have a more pronounced sweetness, a characteristic common in pre-Prohibition beers. It is important to emphasize that the numbers cited here refer to actual percent extract (real extract), not apparent extract (as measured by a hydrometer).
I have entered beers based on this formulation in two competitions. The first was the Second Annual International Beer Competition in Phoenix, Arizona, in March l981, where it won the David Line Trophy (3). The second competition produced entirely different results, probably because of the judges' greater sensitivity to commonly defined beer styles. It was an AHA-sanctioned event held in the midwest in March l993. The score sheets indicated that the judges were exercised in the extreme that someone could enter a beer that was ". . . so far out of category . . ." They suggested that I purchase a copy of Charlie Papazian's book (8) to get a more appropriate recipe. Ironically, all the judges praised the beer's flavor, which was exactly the flavor that originally defined this beer style.
A milder version of American lager was very popular on the West Coast and historically was called Western lager. Possibly the most famous was that brewed by Henry Weinhard. The excellent book by Gary and Gloria Meier includes a survey of the history of this beer (9). From Wahl-Henius (4) and Zimmermann (10) we can surmise that the original extract of Western lager was in the 11.5-12 °P range. Rice (a grain indigenous to the West Coast) was used instead of maize, and the hop rate was about one-third less than that of the pre-Prohibition pale lager discussed above. This is a serious beer that can do well in modern competitions. On the other hand, it appears that before Prohibition, brewers and beer consumers from the East Coast (at that time the most populous part of the country) held Western lager in low esteem. Ironically, this version later evolved into American lager as we know it today.
Spiced lagers were widely brewed in the pre-Prohibition era, possibly to compete with the ales that were available then. Every lager brewer had a unique way of brewing such beers, and even they were likely moving targets. The following should therefore be seen only as one example. The recipe was given to me by Gilbert Straub, and it was regularly brewed by the Straub Brewing Co. of St. Mary's, Pennsylvania, in the period l895 to 1920.
Anecdotal evidence suggests that pre-Prohibition American lagers had high sulfur profiles and that this was a valued flavor constituent. Ale drinkers, then as now, generally found this flavor unappealing, creating a problem for the spiced lager formulations. The brewing log at the Straub Brewery indicates that they dealt with this problem by using an extended 31/2-4 h boil, which removes most of the dimethyl sulfide (DMS) precursor and hence leads to a reduced sulfur taste (5). I have found that in small-scale brewing such extended boils can lead to inferior beer foam, likely because of excessive precipitation of foam-positive proteins. As an alternative, I have found that a low-sulfur flavor can be obtained with a conventional boil using a low DMS-precursor malt. English pale ale malt can be recommended for this purpose.
All-malt Bock beers have long been brewed in North America. Historical references indicate that German brewing procedures and recipes were widely used for these beers in the pre-Prohibition period (7). (I highly recommend Darryl Richman's recent book on Bock beer .) Although this is my personal favorite way to brew Bock beers, it should be noted that in North America an indigenous variant also emerged. It was called a "malt tonic" or "spring tonic," the latter being suggestive of how it was used. Although this beer was usually brewed for the spring, some brewed it year-round for medicinal purposes. Wahl-Henius stated that such beers should be ". . . medicated to such an extent as to preclude their use as beverages . . ." (4). I am not exactly sure what this means, but in any case the recipe shown in the accompanying box is an "unmedicated" version that can be found in Zimmermann's book (10).
All-malt formulations were used for pale beers as well as Bock beers. These beers could be distinguished from continental lagers through their use of North American malt and hops. Such formulations were very popular in New York City and surrounding areas like Brooklyn. Ben Jankowski's excellent article documents one of the finest, namely Trommer's White Label Beer (12). The data given in that article describe the beer as it was brewed in the l940s and l950s. The original extract was 12 °P, with IBUs in the high 20s. The turn-of-the-century version was close but slightly bigger; the original extracts were in the 13-14 °P range, and the IBUs were in the mid-30s.
(1) R. Wahl and M. Henius, American Handy Book of the Brewing, Malting, and Auxiliary Trades (Wahl-Henius Institute, Chicago, l908).
(2) G.J. Fix, "Gilbert Straub and the Pennsylvania Brewing Tradition," Amateur Brewer, No. 9, l982.
(3) G.J. Fix, "Pennsylvania Lager," Zymurgy 4 (4), Winter l98l.
(4) A.L. Nugey, Brewers Manual (Jersey Print Company, Bayonne, New Jersey, l948).
(5) G.J. Fix, Principals of Brewing Science (Brewers Publications, Boulder, Colorado, l987).
(6) W.H. Fotte, "Hannchen Barley Production in Oregon - Its Future," MBAA Tech. Quarterly 2 (4), l965.
(7) H.L. Hind, Brewing: Science and Practice, vol. 2 (John Wiley & Sons, New York, 1943).
(8) C. Papazian, The New Complete Joy of Home Brewing (Avon Books, New York, 1984).
(9) Gary Meier and Gloria Meier, Brewed in the Pacific Northwest (Seattle Fjord Press, Seattle, l99l).
(10) A. Zimmermann, Brauerei Betriebslehre (Buffalo, New York, l904).
(11) D. Richman, Bock Beer (Brewers Publications, Boulder, Colorado, in press).
(12) B. Jankowski, "The Bushwick Pilsners," BrewingTechniques 2 (1), l994.
George Fix is a professor at the University of Texas at Arlington, a senior consultant at DME Brewing Services (headquarters in Milwaukee, Wisconsin), the yeast quality consultant for Crosby & Baker (Westport, Massachusetts), and a member of the editorial advisory board of BrewingTechniques.
Issue 2.3 Table Of Contents