3 Brewing Bock Beer—Materials

It is the raw materials that have shaped Bock beers. The processes that we can analyze to determine where flavors and physical characteristics are formed were devised in order to make better beer from these materials. In the craft environment, one must consider the consequences throughout the brewing process of substitution of materials.³⁰

WATER

As we have seen, the water from Munich has a lot of “temporary” (carbonate) hardness. One analysis of Munich’s water lists these ions:

Calcium	75	mg/L
Magnesium	18	mg/L
Sodium	2	mg/L
Carbonate	148	mg/L
Chloride	2	mg/L
Sulfate	10	mg/L

Without some outside treatment, a pale beer resembling today’s Helles Bocks would be impossible to make. Munich beers were either quite dark or purposely soured until the last century, when the secrets of making pale beers were finally elucidated. At that point, the Munich brewers began to make Helles beer, and eventually, Helles Bock.

In order to brew a dark Bock beer with the relatively dry finish of the traditional Bocks, it is necessary to have a high carbonate content. These carbonates buffer the brewing liquor so that the addition of a large quantity of dark malts won’t over-acidify the mash.

It is important to note here the pH of the mash, not the water itself. Water treatment is supposed to affect the brewing water to get the right pH and ion balance in the mash. Measuring the pH of the brewing water can only provide very little information for determining what to do. With soft water, a small amount of basic or acidic material can cause dramatic shifts in pH; this may have already happened and you can’t tell this from the pH alone.

Contact your water department and have a water analysis sent to you; this service is free from any public utility or private commercial supplier. If you are on a private well, investigate Noonan’s “Water Workshop” article 31 for less expensive ways of discovering the makeup of your water. You can also have a private service test your water for a more complete rundown. Refer to the article in the January 1990 Consumer Reports magazine³² on water testing and purification to learn more about commercially available testing services and different kinds of treatments and their effectiveness and expense.

In many cases, obtaining the necessary levels of carbonates requires the addition or creation of carbonates in the brewing liquor. If this is needed, the water should be soft to begin with, since, besides calcium and carbonate, there is little other ionic content in the Munich water. Adding calcium carbonate (CaCO₃) to the water is the natural way to bring up both components at once. Although calcium carbonate is barely soluble in water (19 mg/L),33 in the acid mash sufficient quantities of calcium carbonate will convert to free calcium and bicarbonate (HCO₃).

Another way to add carbonates to water is by utilizing calcium oxide (CaO, lime powder) in a carbonic acid environment:

CaO + CO₂ → CaCO₃

This can be accomplished by adding calcium oxide to water and then chilling and injecting carbon dioxide under pressure or bubbling it through. Supplying an excess of carbon dioxide is not a problem because it will disperse when used in the hot mash. In this way, calcium oxide can be used, part for part, with calcium carbonate.

Other sources of carbonates such as sodium carbonate (Na₂CO₃) or sodium bicarbonate (NaHCO₃) can also supply much of the needed carbonates, albeit with a substantial contribution of sodium.³⁴ Potassium equivalents (K₂CO₃ KHCO₃) may also be used, but potassium tends to have the same flavor effects as sodium. It may be important to try to spread the cation load around by choosing a combination of different salts to achieve the wanted levels of carbonates.

Harder waters may add a salty or metallic character not wanted in this style. Large amounts of sulfate are not appropriate, as this produces an exaggerated drying effect.^35,36 This effect, especially in combination with carbonates, will increase hop bitterness in a harsh manner. It can also cause excessive acidification of the mash. This will reduce the formation of break material in and after the boil, and can lead to haze formation. If your local water contains significantly more than 50 mg/L of sulfate, consider diluting it with distilled water to bring it under this value and then adjusting for both calcium and carbonate concentrations.

For Helles Bocks, the water should be soft, with some calcium. Munich breweries typically treat their water with calcium hydroxide (Ca(OH)₂)36 to precipitate most of the carbonate as CaCO₃. Home brewers can boil the water, cooling it quietly, and decant it off of the carbonate precipitate. Another approach is to dilute the carbonate water with distilled water until the combined carbonate content has fallen under 50 mg/L.³⁶ Soft water is advisable for use in sparging, as well, to keep the pH of the grain bed from rising during lautering.

With most of the carbonate removed, Munich water is much closer to soft, Pilsen type water. Acidification of the mash is not a problem when using the slightly darker Helles malts, or when darkening is increased by decoction mashing, or when some dunkles or caramel malt is added to the grist.

The calcium needed for acidification and yeast health can be added to soft water with some calcium sulfate (gypsum or CaSO₄), or with calcium chloride (CaCl₂). Although adding either of these raises the paired ion (SO₄, Cl) concentration to levels that wouldn’t normally be associated with Munich water, in small amounts their addition won’t affect the flavor of the resulting beer. 50 mg/L of calcium is a good level for these purposes.²³

MALT

If ever there was a beer style that could be thought of as varietal, Bock beer would be it. Varietal wines are those wines labeled by grape variety rather than by regional wine making practice such as Chardonnay, compared to a white Bordeaux. As the defining feature of these beers, there should be something special about the malt employed. The favorite selection of German brewers is two-row spring Moravian barley, which is a particularly low protein malt. The Moravian barley strain provides a distinct character which is enhanced in the style.37 It is grown throughout the countryside of Bavaria and is in widespread planting throughout Europe. All of the malt styles discussed below are typically created from this variety of barley in Europe.

The situation is very different in North America, where high-protein six-row varieties are often used for “specialty” malts such as Munich, caramel, and chocolate.^2,30 Where a continental malt may have 10 percent protein, six-row malt can rarely be found at under 12 percent, and usually the protein level will be closer to 13 percent. In an all-malt beer, especially one like a Bock, there will be sufficient amino acids (called free amino nitrogen, or FAN) for the yeast to do its job, and the additional protein content in a six-row malt can only lead to haze and instability in the final product.

Also, the malting process currently employed in making these North American malts may not necessarily result in the same flavors and aromas as those in European malt. The makeup of North American barley, combined with a shorter, drier, and higher-temperature malting process, results in the product having a different balance of sugars and amino acids and compounds built from them than the European two-row malts. This issue is of prime importance, and is covered in detail below.

Barley seeds are formed from low-moisture starch granules encased in a tough protein matrix. This matrix is what makes the seeds hard and preserves them over winter into the spring. When the embryonic plant senses that spring has arrived, it can manufacture protease, the enzymes needed to dissolve the proteins of the matrix and only then begin to digest the starch.

The term modification is commonly interpreted to refer to the level of starch breakdown (and therefore, amylaze enzyme content) in the malt. However, it pertains as much or more to protein degradation as to starch simplification.

Continental European malting practice in the past resulted in malt that was not as friable and soft as American and British malts, which are considered to be adequately- and well-modified, respectively. Continental malts have always been considered to be somewhat under-modified.36 As recently as 1965, typical Bavarian malt was sprouted only up to the three-quarters point.³⁸ The embryonic plant was allowed to grow only three quarters of the way around the acrospire. This growth is indicative of the modification level of the malt. British malts are not considered done until the vast majority of seeds show a full length growth of the acrospire.

That has changed, however. Today, imported malts from Germany and Belgium appear to be nearly as modified as their American counterparts. It is entirely possible to use them in single-step infusion mashes, and to expect the same levels of extract as in domestic or British two-row malts.

American two-row strains such as Harrington and Klages provide a different spectrum of proteins, and in greater quantities (typically about 12 percent), which affect the flavors and aromas that arise from the use of these malts.³⁷ This is, in some respects, done intentionally to enhance the enzyme content of these malts so that high quantities of cereal adjuncts such as corn and rice can be converted. This is an important feature since the largest purchasers of these malts have this purpose in mind when they specify the protein levels needed.

MELANOIDINS

One of the most important factors in producing quality Bock beers is the creation and maintenance of melanoidins. These colored compounds also provide many of the malty, bready, and beery aromas and flavors that distinguish these styles.

Melanoidins are polymeric compounds formed by nonenzymatic browning, also known as a Maillard reaction,²³ named for the French chemist who elucidated a part of the chemical pathway. The entire process is still not completely understood.

This process occurs when amino acids, the building blocks from which proteins are created, combine instead with simple sugars. In the first step, the amino acid and a sugar molecule combine in an unstable complex that can then either return to the constituent ingredients or be further modified in a reaction known as an Amadori Rearrangement. The result of this is a molecule called a ketosamine. Ketosamines gradually break down in acidic, aqueous environments, such as conditions found while mashing or boiling. They can also form complexes, however, with additional sugars (diketosamines), that rapidly decompose under heat into a variety of compounds that are precursors to melanoidins. These precursors, while also being heated, are then converted to melanoidins. Under strong heat (212 degrees F, 100 degrees C), the reaction from ketosamines to melanoidins is definitely favored.

Melanoidins formed from the amino acids glycine and α-alanine give the deepest color while the characteristic malty aromas come from valine and leucine. The former will combine at lower temperatures, the latter only once 212 degrees F or 100 degrees C is reached.23 Other amino acids form melanoidins as well, but their properties are not yet known. The melanoidins may be responsible for many malty tastes, and the various precursors can, either directly or indirectly, generate the malt aromas that we so love.

Melanoidin production is most active in the malting process, where situations of highly concentrated amino acids and reducing sugars exist. It also continues to some extent in decoction mashing and to a somewhat lesser extent in boiling. For dark beers, it is important to use a malt with a great deal of melanoidins already in it.³⁷

The precursors to melanoidins are also subject to modification via a process called Strecker Degradation that produces aldehyde byproducts such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, and isovaleraldehyde. These aldehyde compounds are very strong flavoring agents, and it is believed that some of the melanoidin flavors and aromas can be ascribed to them. Many of these aldehydes are carried off in the steam of the boil or further degraded, and the levels carried over into the finished wort are relatively low compared to the initial quantities present in the wort.³⁹

However, the aldehydes produced this way are of relatively low molecular weight, and are only somewhat stable. Later, during beer storage, they can undergo transformations into longer-chained aldehydes, which have even lower sensory thresholds and less pleasant flavors and aromas. As the carbon chain in the aldehyde grows beyond six carbon atoms in length, generally the threshold is so low it can be more conveniently expressed in units of p/L.22

Also, one of the principal melanoidin precursors itself is 5-hydroxymethylfurfural, which has been measured at concentrations of up to 78 mg/L in dark beers.²³ This aldehyde and its cousins, furfural and 5-methylfurfural, are also carried over into the finished beer. Fortunately, they have higher taste thresholds (5-hydroxymethylfurfural has a threshold of 1 gm/L and furfural is 150 mg/L), but furfurals are closely associated with stale flavors.

The other danger arising from melanoidins is that they are easily oxidized, especially when they are hot.⁴⁰ The oxidation of melanoidins is not a direct problem, but they can later be reduced by alcohols, converting the alcohols into aldehydes, or by polyphenols (tannins) which can then cause haze.²² Aldehydes, especially those formed from higher (longer carbon chain) alcohols, produce a distinct stale and cardboard flavor.

On the other hand, if melanoidins make it into the beer in a reduced state, they help to maintain the beer by sacrificing themselves first to oxidation, rather than alcohols and polyphenols. As Fix has stated,²² they are indeed a two-edged sword. The key to producing an extremely stable product is to prevent melanoidin oxidation before packaging, and particularly before cooling of the wort.

Melanoidins are present to a certain extent in all malts, but they can be coaxed into much greater development by careful selection of the barley seed and certain malting techniques. The abundance and balance of amino acids present in the barley and enhanced by the manipulations of the maltster in creating the green malt (malt ready for kilning) and kilning it, can control which kinds of melanoidin compounds are created.23 The green malt must be rich in reducing sugars and soluble amino acids to produce an adequate Munich or caramel malt. Since this situation can only be partially controlled by the modification of the seed during steeping and germination, the barley strain is of critical importance. The end result can be an intense malt flavor and aroma, and deep red-brown colors.

HELLESMALZ (PALE MALT)

2 to 2.7 °Lovibond (2.3 to 4.0 °EBC)

Pale malt will make up the majority of the grain bill for Helles Bocks, and a large fraction of it in the darker colored beers. Especially for the former styles, it is important to use a distinctly flavored malt to produce a memorable and faithful beer.

In a laboratory, this malt can yield 80 to 82 percent of its dry weight up for conversion into sugars and dextrins, and soluble proteins. In a brewery situation, somewhat less yield can be expected.

Typically, this malt will go through a drying phase and very light kilning to produce a relatively pale colored malt that still has some melanoidin character. After the germination process produces the correct level of modification in the green malt, it will undergo a twelve-hour drying phase followed by four hours of kilning. Generally, the drying temperature will be 122 degrees F (50 degrees C), and kilning will occur at 176 degrees F (80 degrees C).⁴¹

The drying phase makes use of the enzymes that have been created during germination to solibulize and break down a lot of the protein matrix. This comes from the action of peptidases, glucanases, and phosphatases. The resulting malt is therefore soft, and this allows the starch granules to be easily liberated during the mash. Some amount of simple sugars are also created, even at this low temperature. The drying phase brings the green malt from about 40 percent water down to about 10 percent.

The kilning process finishes drying the malt, taking the water content down to between 3.5 and 4 percent, which allows the malt to have a long storage life. The low water content tends to help preserve the various enzyme systems in the malt so that they will be available when the malt is mashed.

Helles malt is the only kind of malt that can have any β-glucanase surviving into the finished malt; the higher temperatures used in making other malts completely destroys this fragile enzyme. The β-glucanase enzyme moderates the breakdown of β-glucans, which increase viscosity and slow down lautering.

Kilning also helps to add some coloring and malty aroma by creating a small amount of melanoidins from some simple sugars and liberated amino acids. The low temperature processing determines that only a few of these compounds, particularly the lighter colored and flavored ones, are produced.23

In the end, helles malt is a very specialized product that is a compromise between light color and rich flavor. This compromise is especially suited to the production of all Munich styled beers, and in particular, Helles Bocks.

DUNKLESMALZ (MUNICH MALT)

5 to 9 °Lovibond (9.5 to 21 °EBC)

True Munich malt is a very specialized product. The approach of darkening malt by heating it after it is dry does not imitate the character of the real thing.37 The key to making Munich malt is to use relatively high temperatures while the green malt is still wet to enhance melanoidin production. In this sense, Munich malt is more closely related to caramel malt than to pale malt, although it does retain sufficient enzyme activity to convert its starch content to sugars.

Several steps are taken to insure increased melanoidin levels. More total enzymes are created, and more amino acids and simple sugars are liberated by first “forcing” the piece of malt (as maltsters phrase it) to a high level of modification during germination.³⁷ This intensive modification lowers the total extract available to the brewer, but increases the amount of amino acids and reducing sugars present as the green malt is removed to the kiln. Even so, dunklesmalz will yield 77 to 80 percent in the laboratory.

During the drying phase, the green malt is heated to 149 to 158 degrees F (65 to 70 degrees C), where more sugars are created from the starch. Then, the malt is slowly dried at increased temperatures of about 212 to 220 degrees F (100 to 105 degrees C).⁴¹ At these temperatures and with reducing sugars and amino acids present in high concentrations, the melanoidin formation process (as described above) is greatly enhanced. Once 195 degrees F (90 degrees C) is reached, the process really takes off. At temperatures above 212 degrees F (100 degrees C), the color can triple or quadruple the result of drying at 175 degrees F (80 degrees C). The sugars used to create the melanoidins comprise only 2 to 3 percent of the weight of the dried malt, so extract levels are not greatly affected by the melanoidin forming process.

In addition to increased color and aroma formation from this regimen, other protein removal processes are at work as well. The high temperature enhances protein coagulation and nonenzymatic protein destruction. As a result, Munich malt has a much lower content of high molecular weight proteins, and is much less inclined to form protein hazes in dark beers. Especially during decoction mashing, a tremendous amount of protein is coagulated and removed from the wort before it ever gets into the kettle.

CARAMELMALZ (CARAMEL OR CRYSTAL MALT)

Although this style of malt is originally of English invention, the Germans have adapted it into their own version. Caramel malt is used as a small adjunct, with a maximum of 3 to 5 percent of the grist for pale beers and as much as 10 percent for dark beers. In a pale beer, a lower color malt will be used (20 to 28 °Lovibond / 50 to 70 °EBC), while darker beers may use a combination of pale and dark caramel (40 to 47 °Lovibond / 100 to 120 °EBC) malts. Caramel malt is used to increase malt character, color, and aid head retention.⁴¹ By choosing the caramel malt color carefully, the amount of darkening can be controlled for pale beers.

Caramel malts are created by stewing: the green malt is brought up to 40 to 45 percent water by weight and held between 140 and 167 degrees F (60 to 75 degrees C) for up to three hours. This allows both the protease and amylaze enzymes in the malt to do their work, creating a wealth of simple amino acids and sugars. Then the malt is dried at 300 to 355 degrees F (150 to 180 degrees C) for one to two hours, which builds a high content of melanoidins. The darker the malt, the less extract remains after this color formation. Caramel malts will produce from 70 to 77 percent yield, depending on the original barley and the final color.

FARBESMALZ (ROASTED MALT)

It may seem curious that the malt that is commonly called Munich malt in North America is known to the Germans as dark malt, while roasted malts like black patent and chocolate are called color malts. This has more to do with how the malt is put to use, rather than with the actual characteristics of the malt itself. Dark malt is used to make dark(er) beers, while color malt is used strictly as a coloring agent.³⁹

Color malts should never be used in quantities large enough to significantly affect the flavor or aroma of the beer. Typically, color malts make up at most 1 to 2 percent of the grist.³⁸ This is because they are roasted to such high temperatures that the malt character they would have had from the melanoidins is overcome by the bitter flavors of burnt caramel and proteins.

At the end of the process, the color malt has a water content of only 1 to 2 percent. Normally, this would increase the percentage of the other components of the malt, but even with this, the malt can produce only about 70 percent extract.

Note also that roasted barley, a common ingredient in Irish and British style beers and widely used in North America, is never used in Germany. This is due to the Reinheitsgebot’s prohibition of unmalted cereal ingredients. This prohibition includes unmalted barley.

MALT SYRUPS AND DRIED MALT EXTRACTS

Malt syrups and dried malt extracts offer the great convenience of achieving the high original gravities needed for these styles without a long, complex process. This is because they can be diluted to just the right level. However, they have their own difficulties, and I am unaware of any commercial German brewer using these ingredients to produce Bock beers.

The problems with extracts are three: potential oxidation in handling and storage, low FAN content, and adulteration with sugar syrups. These problems can be avoided and excellent beer can be created with extracts, but doing so requires getting fresh product from a reliable source, and performing a mini-mash to help overcome problems that might arise from the latter two areas.

It is critical to the quality of the beer, and of dark beer specifically, that it be created with unoxidized wort.⁴⁰ As has been made clear in the professional and homebrewing literature, the melanoidins which are so crucial to the flavor and stability of Bock beers will quickly cause the beer to become stale and unpalatable once oxidized.²² Oxidized melanoidins are at the beginning of several different oxidation reaction chains (mentioned above in the section on melanoidins) that can cause problems with haze and off-flavors. Any oxygen that might be included in the malt extract during the packaging process will have a long period before connecting with the melanoidins in the wort.

Oxidation also increases wort color. An increase of oxygen content from 0.2 mg/L to 1.0 mg/L can increase wort color by 0.38 °SRM (1 °EBC). A further increase to 10.0 mg/L can add another 1.4 °SRM (3.5 °EBC). This darkening does not come with the same aromas and flavors expected from good quality malts.

Darkening can be increased during extended storage times due to the Maillard reactions continuing unabated. In these conditions, a high concentration of reducing sugars and free amino acids are present. However, the different (lower) storage temperatures emphasize formation of a different balance of melanoidins than are created in the high temperature malting, mashing, and boiling processes.37 This is why it is important to get fresh extract.

Long storage times are sometimes encountered with the distribution and retailing of malt extracts. Ask your supplier when they received their shipment; encourage them to find out how long their distributor has had it. If you start with old extract, your beer could be old even before it has finished lagering.

Other concerns, that have been reported in many publications,^42,43,44,45 indicate that nearly all of forty-four commercial lager extracts purchased from maltsters and from home brewing retailers in Canada had significantly lowered levels of free amino nitrogen (FAN). Many levels had lowered below the point where proper yeast metabolism could be maintained in a standard beer wort of 1.048 (12 °Plato). Some of these extracts had levels that were only half or a third of the generally recommended minimum of 150 mg/L. A Bock beer wort created exclusively from one of these extracts, in spite of the higher original gravity (and correspondingly higher FAN concentration), could still fall at or below the minimum FAN requirements. Further evidence^42,45 shows that FAN utilization by yeast in an extract wort is significantly reduced, regardless of the initial FAN concentration. This evidence leads to the concern that the FAN present has undergone some change during processing that renders it less available to the yeast.

It is not clear why this comes about. One might speculate that as the extract ages and the Maillard reactions continue, a significant fraction of the FAN becomes bound up in melanoidins. If this were to prove true, fresh extract would again be the appropriate solution, but the experiment has not been conducted. Regardless, reduced FAN levels can be counteracted by adding fresh malt back into the beer wort by doing a mini-mash.

Another consideration in examining the use of extracts was reported in the Journal of the American Society of Brewing Chemists.42 Disturbingly enough it was reported that significant evidence of apparent adulteration of some extracts with glucose syrups had been found. (Unfortunately it is unclear who is at fault for the detected adulteration, thus concrete action has yet to be taken.) This not only has the effect of diluting what FAN is available but changes the sugar balance of the resulting wort. This change can have a profound effect on the yeast, because yeast uptake of sugars follows a fixed schedule. Since yeast metabolizes sugars in a rigid order, with single chain sugars used first, high quantities of them suppress the uptake of more complex sugars like maltose.

In a normal all-malt Bock wort, glucose makes up about 25 percent of the carbohydrates; maltose and maltotriose make up as much as 45 percent³⁸ (dextrins and other minor sugars make up the rest). A wort created from an adulterated extract could easily have these percentages reversed. In such a situation, the Crabtree effect can inhibit the yeast from entering the respiration phase,²² thus preventing the high reproduction rates needed early in the fermentation to obtain the optimal yeast density in the beer. This can lead to long, disordered fermentations, which can provide opportunities for invading organisms to gain a beachhead in the wort. Indeed, Journal of the American Society of Brewing Chemists42 notes that comparisons of attenuation of the original 1.048 (12 °Plato) wort were cut off after reaching 1.024 (6 °Plato), rather than the planned 1.012 (3 °Plato), because some of the test worts created from extracts never reached their appropriate final gravities.

Dried malt extract (DME) is created by spraying hot wort through a partial vacuum (which lowers the boiling point of the water in the wort), evaporating the water and leaving the wort solids behind. One of the conveniences of DME is that it is easy to measure out and divide up.

However, once the package is opened, another factor comes into play. DME is very hygroscopic, meaning that it will pull moisture out of the air, and begin to liquefy. It is the liquefaction that allows oxidation reactions to proceed, so this must be prevented. DME, once opened, should be kept in a closed, cool, dry environment. A refrigerator or freezer is a good location, since the cold air can hold much less moisture.

There is no information regarding possible adulteration of DME^42,45 as only extract syrups were tested.

Another point of consideration in choosing an extract product: one should be guided by the intended use described on the extract’s label. Extracts made from lager malts should provide more of the sulfury, lager character that will help to distinguish the flavor and aroma characteristics of these beers. Extracts made from continental malts have a better chance of containing the crucial melanoidin balance that is wanted.

The greatest difficulty in recommending extracts is that the evidence shows they can be quite variable from brand to brand.42

One should attempt to get the freshest product, from a well known and respected source. Store it in a cool place once purchased, and use it up quickly. Once an extract is discovered that produces a quick and complete fermentation, patronize the producer. Extracts are not interchangeable parts of a beer, and a bargain price does not always purchase a quality product.

The bottom line on extracts is that they can make the process far shorter and more convenient, but insufficient information is available to guide the brewer in making the correct product choice. By formulating recipes with significant amounts of added malts in a mini-mash, potential problems can usually be minimized. This is particularly important for Bock beers, that depend so heavily on the quality of the malt aroma and flavor.

HOPS

Because bitterness can be discussed easily in terms of quantifiable levels, this tends to overshadow other considerations when choosing boiling hop varieties. Realize that even though such hops are usually discussed only in terms of the bitterness they bring to the beer, they will also contribute differing flavors. Bitterness is only one dimension of hop character, even in hops boiled an hour or more.

Hopping rates are affected by the kind of brewing liquor in use. If the brewing liquor is highly carbonate, as is the case with traditional Dunkles and Doppelbocks, smaller quantities of noble hops should be used in order to maintain the elegance of the beer. Carbonates enhance the perception of bitterness from the hops.36 Carbonate waters have been called “hop savers”,²⁹ but in fact, they emphasize the strong bitterness of the hops and tend to hide the finer flavors. High α-acid hops are particularly affected by this, and yield very rough, coarse flavors that quickly become unpleasant.

Physical characteristics can be important as well. Even though the higher gravity wort of a Bock beer will tend to reduce the amount of bitterness available from the hops,⁴⁶ the decreased bittering rates keep the total mass of hops used low. Because hops help to coagulate proteins and therefore clarify the beer, the tiny quantities of high α-acid hops that might be called for on the basis of bitterness alone could prove insufficient for clarification purposes. This is especially so in a high protein wort such as a Bock. This could be further emphasized by other processing choices like a shorter boiling time and an infusion, rather than decoction mash.

The most local product for Bavaria comes from the Hallertauer region south and east of Nürnberg. Hersbrucker or Hallertauer Mittelfrüh are the most highly prized products of the Hallertauer region.

In Helles Bocks, where carbonate levels will be low, higher hopping rates should be used, but the fine noble flavors of Hersbrucker, Hallertauer Mittelfrüh, Spalter, and even Tettnanger are still preferred. These give the cleanest, most elegant, and balanced flavors to the beer.

American varieties of the Hallertauer strain, like Mount Hood and Liberty, also work well in Bock beers because they have similar flavor and aroma characteristics to their German forebears.

Other, more distinctive, varieties can be used in blends to tame them a bit. Saaz, Styrian Goldings, and some English and English-derived strains like Kent Goldings, Fuggles and Willamette can be used in blends with the more traditional hops mentioned above to give unique flavor and aroma notes. Although these would produce less traditional beers, they would not be so strange as to break the Bock beer mold.

The strongly floral and very distinctive citrus flavor of Cascades can fight with the malt and lager characters of Bock beers. Although the author doesn’t find this an appealing combination, especially in Helles Bocks, with North American brewers looking for very distinctive products, this elicits partisans on both sides.

YEAST

The yeast pitched must be a good strain in excellent condition, for the rigors of a high-gravity wort fermentation can otherwise prevent the completion of the task. There must be a large quantity of yeast, and it must already be acclimated. Only when the yeast is at its peak, can it produce a clean product that is free of off-flavors.

The high original gravity, combined with the high final ethanol content work together to inhibit yeast activity. The high concentration of sugars creates osmotic pressure on the yeast cell which, without effort on the part of the cell, would draw water out of the cell’s cytoplasm. This effort distracts the cell from other metabolic endeavors, like reproduction, respiration, and fermentation.

Ethanol, as a waste product, is toxic to yeast. This effect is heightened as the fermentation progresses and ethanol concentration goes up. In some cases,⁴⁷ this can cause the complete cessation of fermentation well short of the attenuation limit of the wort. Worts with starting gravities above 1.096 (24 °Plato) never reach the attenuation limit with lager yeast.

The strain of yeast chosen should be a known performer, capable of working in a high-gravity environment and still completing the fermentation. It should produce as neutral a flavor as possible, since fermentative byproducts are generally perceived as flaws in the Bock styles.

It must not be of a highly flocculative nature; such yeast strains do not stay in suspension long enough to complete the fermentation, and so the resulting beer will be sickly sweet. In such a situation, the yeast may also leave a strong, unwanted diacetyl component. This comes about because the yeast falls out of solution before all the sugars are used up, forcing it to metabolize the diacetyl produced early in the fermentation.

Yeast propagation is discussed further in the recipe chapter, but it must be kept in mind that yeast grown on a medium without maltose will require an adaptation period of as much as a day, slowing the start of the fermentation.47 Although optimum yeast reproduction can be obtained with continually replenished and aerated weak (0.5 percent) sugar solutions, such yeasts are not adapted to brewery conditions. Typically, yeast propagation in the brewery is accomplished with all-malt wort.

The author has had good results with both commercially available strains and those collected from continental and large breweries in the United States. Any strain with good alcohol tolerance that meets the other requirements set forth already will produce a fine Bock. Wyeast Bavarian (2206) is a good place to start. Mixed reports have been aired on Wyeast Munich (2308). Apparently it is somewhat unstable and can produce high levels of diacetyl, therefore requiring special handling (a diacetyl rest) at the end of the primary. Wyeast Bohemian (2124) tends to produce more esters than are called for in the style.

If the brewer is interested in attempting the reproduction of beers from previous centuries, there is room for greater creativity. Before the middle 1800s, single cell cultures were unknown, and mixed cultures of ale yeast were the rule. Lagering has always been practiced to some extent, though, with regard to these styles, so an ale strain that is cold-tolerant is important. Alt beer strains, such as Wyeast German Ale (1336) come to mind, but the ever popular Sierra Nevada/Narragansett yeast (Wyeast American 1056) seems to be tolerant of temperatures down to 50 degrees F (10 degrees C). Both of these strains are good fermenters and do not produce high levels of esters or diacetyl.

The further back in history one goes, the more likely it becomes that some level of lactic acid producers would have been included in the microflora. One should turn to the practices of the rural Belgian brewers for a view back in time. (Suggested reading is Lambic by Jean Xavier Guinard.)24