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Before a short vacation break, we brewed a light bock beer on 26.07.2023 for the milestone birthday of an employee of Clausthal University of Technology. The dark bock beers that are commercially available in winter are probably well known. The base of these beers usually consists of Munich malt, rounded off with caramel malt, melanoid malt and colored malt, depending on the recipe. A bock beer must have an original gravity of at least 16 °P in order to be labeled as such, and the alcohol content is around 6 - 6.5 % vol. due to the high original gravity. Another well-known beer is Maibock, a pale bock beer with an alcohol content of around 7 - 7.5% vol. The use of light barley malts such as pilsner malt, pale ale malt or Vienna malt in combination with light caramel malts and the higher original gravity results in beers that have a noticeably deeper color than the fairly light pilsner beers. Most bock beers are bottom-fermented, while top-fermented beers are usually wheat bock beers.
Our batch consisted of 75% Pale Ale malt and 25% Carapils. We mashed isothermally for 60 minutes at 73 °C in our 70-liter system with agitator, followed by approx. 40 minutes of lautering in the BrewMonk Titan (as a heated lauter tun). The wort was kept at a constant 73 °C and the make-up water had a temperature of 80 °C. In this way, any starch rinsed out in the lauter tun is safely saccharified, and we will further increase the temperature of the sparge water in future trials. After lautering, we achieved 52 liters of wort with a quite considerable original gravity of 18.5 °P.
From the comparisons with the systems using malt pipe technology, we can conclude that higher original gravities are achieved with classic systems with agitators for a comparable amount of malt. If it remains at 18.5 °P after fermentation, the beer would even be a doppelbock. The wort was boiled for 60 minutes with a non-isomerized hop extract for the bitterness, and we added 20 grams of a special aroma hop extract in the Citra variant and 300 grams of Hüll Melon Wethop to the whirlpool at around 90 °C. Both hop varieties harmonize well with each other and should not lend the beer overpowering fruity notes.
The brew is fermented with Mangrove Jack's M84, a bottom-fermenting Bohemian yeast. This shows very good sedimentation and the beers fermented with it are usually clear after four weeks without the use of aids. We can only estimate the alcohol content from previous brews with this malt blend. With an original gravity of 12 °P, we usually achieve alcohol contents of no more than 3 % vol. with maltotriose-positive yeasts. If we now apply a simple rule of three, this beer should achieve an alcohol content of approx. 4.5% vol. However, this remains to be seen, because isothermal high-temperature mashing requires a homogeneous temperature distribution right from the start. Our experience with the malt pipe technique has shown that temperature pockets with a lower temperature can occur during mashing-in without circulation.
The beta-amylase is then active for a few minutes, it produces maltose and, as a result, the finished beers achieve higher alcohol contents than expected.
We are currently working on a bachelor thesis in the field of gluten-free beers, and we have also carried out many tests in the project on gluten-free beers based on quinoa in recent weeks. This work is tying up a lot of capacity and will not be reported here for the time being, so we were only able to brew freely again on July 17.
We were asked to brew a nice fruity Pale Ale for a conference taking place in September. Commercial pale ale beers often have an alcohol content of between 6 and 8 % vol, for which there are several reasons. On the one hand, these beers are often brewed a little stronger with original wort levels in the 13 - 15 °P range, and on the other hand, the so-called "hop creep" effect occurs during the dry hopping process.
Depending on the variety, hops contain different amounts of amylases (glucoamylases, alpha- and beta-amylase), which break down the non-fermentable higher sugars produced during the brewing process (maltotetraose and higher, as well as some dextrins) into glucose, maltose and maltotriose and thus feed them into the fermentation process. This increases the alcohol content considerably, and a Pale Ale that has been cold-hopped with the US aroma hops Simcoe and/or Cascade can easily reach 8% alcohol by volume at an original gravity of 15 °P.
With so much alcohol, a little caution is naturally advisable, especially as the natural breakdown rate of alcohol in the human body is only 0.085 - 0.1 g per hour and kilogram of body weight, depending on gender, provided there is no allergy to alcohol or a lack of alcohol dehydrogenase. If you drink a liter of a Pale Ale with 8% alcohol by volume, you consume a good 65 g of alcohol. With a body weight of 70 kg, it takes between 9 and 11 hours to completely break down this amount of alcohol. Assuming a body weight of 70 kg with a water content of 50% and assuming, for the sake of simplicity, that this amount of alcohol is distributed homogeneously, a person weighing 70 kg would build up an alcohol content of almost 2 per mille when drinking one liter of such a beer quickly.
From these simple calculations in the first semester of a chemistry course, it should be clear that alcoholic beverages should always be handled with great care and that reducing the alcohol content while maintaining a comparable taste is certainly not a bad goal. The legislator has defined alcohol contents of < 0.5 % vol. in drinks as "alcohol-free", because with the above-mentioned natural degradation rate of 0.085 - 0.1 g per hour and kilogram of body weight as well as the limited absorption capacity of liquid, it is virtually impossible to build up an alcohol content that is unfit for consumption.
On the other hand, brewers often argue that alcohol is a very important flavor carrier. This is not fundamentally wrong, but from a molecular point of view, in a non-ideal mixture of alcohol and water, this does not necessarily mean that a lot of alcohol always leads to more flavor. Such a simple "a lot helps a lot" approach ignores the non-trivial interaction of water and ethanol molecules on a molecular level. Cold hopping also introduces both non-polar, more volatile aroma components into a beer, whose vapor pressure is hardly affected by the alcohol content, and polar, less volatile aroma components, which do not volatilize significantly even at a typical whirlpool temperature of 80 - 90 °C. It should also be noted that many aroma compounds are glycosidically bound to sugar structures and these are split off by the enzyme beta-glucosidase, which some yeasts possess intrinsically. If hops with more volatile components are combined in dry hopping with those with less volatile components in whirlpool hopping, the aroma profile can be well controlled.
In order to achieve an alcohol content of between 3 and 4 % vol with an original gravity of around 12 °P in a pale ale, the principle of stopped fermentation could be applied, which some breweries do. These beers usually taste somewhat sweet, which is not necessarily a disadvantage. In such cases, unfermented maltose and maltotriose can be reliably detected using HPLC.
We take a different approach to the production of low-alcohol pale ale beers, which was published in the trade journal BRAUINDUSTRIE at the beginning of the year. Specifically, we used Pale Ale malt and a small amount of Carapils to produce a wort that reached a good 12.5 °P using isothermal high-temperature mashing. We mashed in a mash tun with an agitator, lautered in a thermostatically controlled lauter tun (BrewMonk Titan) and then boiled in the Braumeister 50.
The procedure is similar to that of a three-vessel brewhouse. As previously reported, the systems with agitator are clearly superior to the malt pipe technology for isothermal high-temperature mashing, as homogeneous mashing-in takes place at the beginning without the formation of temperature nests at a lower temperature, in which the beta-amylase is then active for a short time and produces maltose. All beers brewed in this way with Pale Ale malt and maltotriose-positive yeasts showed around 3 % alcohol by volume at 12 °P original wort temperature.
The wort was boiled with a non-isomerized bitter hop extract for 60 minutes, followed by whirlpool hopping at around 90 °C with an aroma hop extract from Yakimachief in the "Citra" variant. For the dry hopping, we used the lupulin-enriched P45 hops "Simcoe" and "Citra" (CryoHop from Yakimachief), which were briefly heat-treated in wort in a closed vessel to inactivate the amylases before being added to the wort. The brew is fermented with "Ebbegarden Kveik", a maltotriose-positive yeast that possesses the beta-glucosidase enzyme mentioned above and thus emphasizes the hop aroma per se in addition to the yeast's own fruity aromas. Provided that the hop enzymes have been safely denatured at the selected temperature, the alcohol content of the final beer should be around 3% vol.