Notes on the Home Production of Authentic Bavarian-Style Weissbiers

Let’s first address 2 bones of contention regarding process and production of Bavarian-style wheat beers such as Hefeweizen, Dunkelweizen and Weizenbock: whether the presumed fuss & bother of performing a decoction mash as described by Eric Warner in his highly-recommended 1992 book on the style, is worthwhile; and whether a ferulic acid rest at ca. 113 F (45 C) is effective in enhancing the clove-like spiciness expected in Weissbiers. A review of 21 AHA NHC medal- winning Hefeweizen and Weizenbock recipes reveals that 10 worts were produced from variations on a decoction mash program, 6 utilized an upward step mash, and 4 gold and 1 bronze medal winner were produced with single infusion mashes in the range of 150-156 F (ca. 65-69 C); 9 of the 21 employed a ferulic acid rest. My search revealed no medaling Dunkelweizen. Roggenbier is a very closely allied style: both Roggenbier gold medal winners were produced with single stage infusions at 154 F (67.8 C) & 158 F (70 C), respectively.

 

Apparently, it is possible to produce a well-received Weissbier or Roggenbier without a decoction. Whether decoction contributes improved flavors, and whether inclusion of melanoidin malt effectively replicates those flavors without a decoction, are questions I do not presume to resolve here. However, I have found that a single or double thick decoction can deliver higher brewhouse efficiency and reduced lautering times. What isn’t contested is that the degree of melanoidin development and wort color deepening is a function of the length of the boil, both in the decoction vessel, and in the kettle.

 

The efficacy of the ferulic acid rest is also controversial. We are told that ferulic acid, a derivative of the amino acid phenylalanine, is bound by pentosans in the bran layer of wheat and barley malt grains in the Weissbier mash. The temperature optimum for ferulic acid hydrolysis is typically given as 113 F (45 C). Free ferulic acid is then decarboxylated to 4-vinyl-guaiacol (4VG), the phenolic compound responsible for the ‘clove’ spice character of Weissbier, in the presence of POF+ Weissbier yeast in an active fermentation. Skepticism at the homebrew level about the value of the ferulic acid rest is exemplified in a 2019 Brulosophy ‘exbeeriment’ posted by Phil Rusher wherein a tasting panel was unable to distinguish Weissbiers brewed with and without a ferulic acid rest. And yet the most traditional Bavarian Weissbier breweries continue to perform a ferulic acid rest, and this effect has been quantified in laboratory analyses. If it’s good enough for Schneider, I am going to continue doing one, in part because the ferulic acid rest optimal temperature range overlaps broadly with the range of activity for beta glucanase, which breaks down troublesome glucans that interfere with efficient lautering. The difficulties that arise with Weissbier production are most often encountered at the lauter stage. A ‘stuck sparge’ can be the bane of lautering a Weissbier mash rich in gummy glucans. (The time I attempted a Weissbier with a step mash – with rice hulls mind you – was the only stuck mash I have ever experienced with the mash tun that I have had now for 3 decades – a 4-hour fly sparge!) Unfortunately, while the temperature ranges are roughly the same, ferulic acid hydrolysis and beta glucanase activity have different pH optima. Ferulic acid hydrolysis is favored at pH 5.7-5.9, whereas beta glucanase activity is greatest at pH 4.6-5.0, below the optima for amylase starch conversion. Happily, proprietary glucanases with wider temperature & pH ranges that have been available to commercial brewers have now trickled down to the homebrew market at reasonable prices. What I recommend is to mash in to a target temperature of 113 F (45 C), but withhold any acid malts; phosphoric or lactic acids; or other pH adjustments until after a 10- or 20-minute rest at ca. 113 F (45 C). Don’t stress about being too precise; the range of activity is between 104 & 122 F. (40-50 C). And yet, I would be wary of the standard ‘protein rest’ at 122 F (50 C).

 

A quick note on milling. I follow the lead of Warner (1992), who had had real-world experience working in a Bavarian Weissbier brewery when he wrote his book, and mill the wheat malt finer than the usual setting for barley malt. This is easy to overlook, and if you mill by hand cranking as I do, you will come to appreciate how much less friable wheat malt is than barley malt. With that caveat, I still recommend getting out your feeler gauge and reducing the roller gap to 0.024” (0.6 mm); on my budget hand mill this is as tight as she goes.

 

I recommend certain departures and simplifications from the decoction programs outlined so expertly by Warner (1992) that shouldn’t disappoint in terms of results. The traditional triple & double decoctions of yore evolved in a time of, by today’s standards, under-modified malts – good luck finding those – and before the availability of modern process aids such as the above mentioned glucanases, which of course still wouldn’t be used in Bavaria – Reinheitsgebot and all that. With this in mind, an initial ‘acid rest’ should be omitted. There are easier & faster methods of adjusting the pH later; I prefer adding acidulated malt, if needed, after the ferulic rest – which actually is allowed in Germany.

 

I have reproduced below the concise & illustrative figure that the creator(s) of the excellent website Braukaiser have abstracted from the technical brewing literature to convey graphically the pH & temperature ranges of the enzymatic processes I discuss in this article.

 

https://braukaiser.com/wiki/index.php/How_pH_affects_brewing

 

 

There are different methods available for raising the mash from 113 F (45 C) to 137 F (45 to 58.3 C). You could pull a thick decoction of 1/3 the mash volume, and then, after boiling, return the decocted mash slowly and carefully to achieve 138 F (58.9 C), at the high end of the protease range to prevent the rest mash falling back into the lower peptidase range during the second decoction; but then you would be doing a double decoction. If you have a direct-fire mash tun like mine, or an all-in-one system with RIMS, you could raise the temperature as you would a step mash. My preference is to mash in targeting the ferulic/beta glucan rest temperatures with a 1 qt. per pound ratio – a thick mash favors these lower temperature processes – then add hot water that I have previously set to boil in the 20 qt. stockpot that will later serve as a decoction vessel, to the mash. This size stockpot has proven adequate with single decoctions for 10-gallon batches of a Weizenbock, so is more than ample for lower gravity Weissbiers; though I have sometimes wished I had opted for the 6-gallon. Here’s an example from which you may extrapolate. Imagine a standard 5-gallon homebrew batch: 10 lbs. of malt have been doughed in at a 1:1 ratio with 10 qts. of 126.2 F (52.3 C) water to achieve a 10–20- minute rest at 113 F (45 C). A popular mash calculator suggests you would add 3.8 qts. of boiling water to this thick mash to hit the 137 F (58.3 C) protease rest temperature; throw in some ice if you overshoot. The rest mash temperature will be expected to fall during the subsequent decoction, so I aim for the higher end of protease activity. These latter processes are also said to be more efficient in a thick mash, but life is full of compromise. For decoction, you actually want to end up with a fairly thin mash overall, which will favor attenuation. Warner (1992) recommends 1.4 qt. to the pound, and that works well. You may even want to add a little more water to replace any that evaporates during the boiling of the decoction. For the 10 lb. example above, boil 5 qts. of water, and reserve the extra 1.2 qts. for thinning out the very thick decoction about to be pulled. For extended decoction boils of 30 minutes or more, it would be wise to keep a tea kettle of extra hot water on hand to replenish further evaporative loss from the decoction to be boiled in the next step.

 

There are any number of variations on a decoction mash. Aside from Warner (1992), another Braukaiser webpage on the topic of decoction provides some interesting possibilities. Don’t feel you must be constrained by a particular published program or recipe; not even mine. You can do this. It’s not rocket surgery, just some simple every day brain science. And depending again on your gear setup, I wouldn’t worry about hitting the numbers right on every time. If the temperature is a little low, direct or indirect heat (e.g., RIMS) can quickly correct that; and simply adding the boiled decoction back slowly and carefully as both mashes cool passively should prevent overshoots.

 

Here is something you can try at home. You have verified starch conversion with a negative iodine test before boiling the decoction. Now, after boiling, perform that test again and you will probably see a positive starch result. The physical and thermal effects of the boil will have liberated more starch from the grains, now accessible for later conversion when returned to the rest mash. I have gotten better than 95% brewhouse efficiency by these methods, as opposed to ca. 85 % with one stage infusions with highly-modified British malts, where you definitely don’t want to be messing about in the protein active ranges if you want any foam at all. You will have also broken down more of the viscous gummy fractions and made lautering easier. But for a wheat beer, still use lots of rice hulls – perhaps a lb. for each 5 gallons of finished beer, only added at mash-out – and you may just have a shorter brew day than you would have had with a step mash – or at least not a much longer day.

 

We have easier methods of raising mash temperatures than our 19th century forebears, so the thin third decoction to reach mash-out temperatures shown in some decoction programs is another step that can be omitted. The time and temperature(s) of the rest(s) you choose for final conversion back in the mash tun once the decoction has been returned to the rest mash I leave to your intentions and creativity. If you have followed me so far in this article, you’ll know what to do. I like good attenuation, so I prefer an hour at 146-147 F (ca. 63.5 C), followed by a gentle slow rise to mash-out at 168 F (75.5 C).

 

 

 

Other techniques have been proffered for enhancing yeast-derived flavors; most involve stressing yeast by under pitching, or under oxygenating the wort. However, these methods risk an extended lag phase and/or sluggish fermentation, so I have never tried them.

 

I have made enjoyable Weissbiers in closed fermenters with Munich Classic, but never quite felt they expressed all of the flavors I have experienced with imported examples. That all changed when I was able to safely perform an open fermentation. The advantages of open fermentation for yeast forward styles (Weissbier; Belgian and British ales) are well documented and discussed elsewhere. It’s also traditional, which has its own intangible appeal. Traditional producers continue with open fermentation, generally in wide shallow vessels, and much is made of the importance of the ratio between the width and depth of these vessels. But such observations are made with respect to commercial fermenters containing tens or hundreds of hectoliters. Open fermentation is beneficial due to not having the inhibitory CO2 backpressure building up above the wort as would be the case in a closed vessel. But what explains the importance of fermentation vessel dimensions? A shallow vessel also subjects the ferment to less hydrostatic pressure than a tall conical fermenter. Further study, as they say, is needed, but suppose it is simply the depth,  regardless of the width, that is important, as would seem to be the case were the additional determining factor hydrostatic pressure. As homebrewers we’ve got this; our worts rarely sit very deep in the fermenter compared to commercial operations. Or it is may also be possible that a wide shallow ferment benefits from a greater surface area for exchange of gases between the evolving CO2 and the ambient air. But wide and shallow is difficult to configure at the homebrew level. An amusing YouTube video shows a Weissbier brewed in a bathtub, but that seems more a parlor trick than a viable approach to home fermentation.

 

Our goal then is to get the lid off of our more familiar fermenters, and the larger the top aperture the better, in part to allow the free escape of CO2, and in part because we need to be able to skim the Krausen. The standard 5- or 6-gallon bucket can scarcely contain the high growth of krausen you can anticipate once these yeasts are given free rein in an open vessel.

 

I had long contemplated obtaining a 20-gallon food grade plastic winemaking fermenter for brewing 10- or 15-gallon batches, building in a tap & spigot a couple of inches from the bottom, and then, as soon as the krausen has receded, and attenuation has slowed sufficiently, simply draining the contents directly into 2 or 3 5-gallon corny kegs fitted with a collective spunding valve – the keg gas fittings can be plumbed together to equalize the pressure – to naturally carbonate. We are after all brewing Hefe-Weissbiers, so some residual yeast at serving time should be acceptable, and the ongoing ferment will gobble up any oxygen picked up in the transfer. For 5-gallon batches, a 10-gallon wine grape fermenter, and a single corny keg and spunding valve should suffice, and might even fit into a converted fridge, or other temperature controllable closed chamber. Just set the spunding valve to blow off at the PSI that a carbonation chart tells us corresponds to the target level of 3.5 volumes of CO2 for the temperature you are working at, and all is golden*. If you miss the moment, and generate insufficient pressure, external CO2 pressure can be applied later to reach 3.5 volumes. I am still convinced that this approach would work admirably. Unfortunately, my drafty garage/brewery in San Francisco is afflicted by fruit fly-festation seasonally. So, despite John Palmer’s assertion on his highly-recommended short video on the topic of open fermentation that the evolving CO2 is noxious to insects and would protect the ferment, there is a limit to my confidence in that effect in my particular situation. Palmer also suggests placing a towel over the open fermenter; but would that actually be an open fermentation? It seems like the towel would impede the gas exchange at the surface of the krausen. If you have an enclosed dust- and insect-free room, you shouldn’t need the towel, but such a space could be a challenge to protect in a domestic setting.

 

(*It’s worth a mention that true Bavarian Weissbiers are bottle conditioned with speise. Since I don’t follow this practice myself – it’s very complicated – I refer you again to Warner (1992), should you wish to attempt it at your own risk. Or just bottle condition at full attenuation in the usual homebrew fashion.)

 

It wasn’t until I obtained an enclosed, easily sanitized fermentation chamber and a 55 L wide-mouthed Fermzilla that I was able to confidently perform open fermentations of Weissbiers, and achieve the very expressive 4VG and ester character I had been seeking. Pitch your yeast with the lid off. If it makes you feel better, you can lightly cover the mouth of your fermenter with foil until signs of active fermentation are evident – I do. But then remove any impediment to CO2 evolution until the krausen begins to subside. The key for me was having an enclosed chamber, be it homemade or storebought – a miniature version of the presumably clean and sanitary enclosed spaces wherein traditional breweries conduct their ferments.

 

When you give one of these Bavarian wheat yeasts their head, they will take every inch and more. You will probably need to do some serious skimming to avoid a sticky mess. Beware of going to sleep at night without taking precautions, especially with the higher gravity Weizenbocks. Unless you wish to harvest yeast from the krausen, I recommend the maximum dose of one of the proprietary silicon-based foam control aids available from your homebrew supply these days; you will still have plenty of krausen, and quite possibly improved foam retention in the glass.

 

The yeast-derived flavors we seek are formed early in fermentation, from the growth phase through high krausen. Once the protective krausen begins to subside at day 3 or 4, it’s time to think about either transferring to a closed vessel, or capping the fermenter and trapping CO2. You may wish to elevate the temperature for a few days as attenuation is slowing and allow the yeast to clean up any diacetyl or acetaldehyde prior to packaging.

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