June 2022

The student internship is currently taking place in the research brewery, which is part of the elective module "Introduction to the Chemistry of Brewing" in the Master's degree program in Chemistry at Clausthal University of Technology. After an introduction, we brewed on June 11 and 18, and the last brewing day of this year's internship will be June 25.
 

On the first day of practical training, we brewed a fake dark wheat beer using only barley malt, even though we will end up calling it something else, because by law a wheat beer must contain at least 50% wheat malt in the brew. There is no hard scientific justification for this, just as there is no scientific justification for the fact that only barley malt may be used for bottom-fermented beers under the so-called Purity Law. Even with a malt bill that consists of 100% wheat malt plus rice husks as a lautering aid, it is possible to brew a beer that comes very close to a Pilsner beer, even if such a beer may only be marketed as a "special beer" under certain conditions.
The taste of a wheat beer is therefore dominated by the wheat beer yeast, and only very well-trained tasters can taste the absence of wheat malt in a blind tasting. In terms of the mash bill, we used the dark wheat that was brewed in April as a guide, replacing the wheat malt with pale ale malt and the carawheat with melanoid malt.
Mashing was also carried out isothermally at 72 °C, which allows the alcohol content of the finished beer to be significantly reduced. Mashing was carried out in our system with agitator, which can hold up to 65 liters. The wort was lautered via a lauter hose into a heated vessel, from where it was pumped into the Braumeister 50, where it was boiled. The process is the same as in a 2-vessel brewhouse.
The mild bitter hopping was carried out with Herkules, while Hallertauer Blanc WetHop was used for the whirlpool hopping. Its aroma profile is described as "fruity-floral, passion fruit, gooseberry, grapefruit, pineapple", the brew was fermented in a cylindrically-conical fermentation vessel (ZKG) with the Wyeast 3068 in the 2nd guide. This is identical to the W68 from Weihenstephan, a wheat beer yeast used in many breweries, which brings out the banana aroma in wheat beer. As the yeast sediments poorly, it is a good idea to lower the pH value of the wort with sour grains if high quantities of aroma hops are used. This helps to eliminate bittering substances, making the beer easier to drink and giving it a more harmonious taste overall.
 

The Christmas bock was supposed to be brewed on June 18, but unfortunately we were only able to brew it on October 30 in 2021. So this time the beer should be ready for the Christmas season. To investigate the influence of the yeast on the taste, the recipe from 30.10.2021 was doubled with 50 L for two fermentation vessels with different yeasts, brewed in the Brew Tools 150 Pro.
Mashing and lautering were initially unremarkable so far, unfortunately we didn't quite achieve the required original gravity. Instead of the expected 16.5 °P, we only achieved 14.5 °P after boiling, so instead of a bock beer, we only brewed a small bock. As the spent grains still tasted very sweet, the problem lay in the after-pour. In large breweries, the spent grains are loosened up in the lauter tun with a chopper, and the secondary sparge is applied in several portions. This ensures that the spent grains are almost completely washed out. To date, there are no comparable choppers for the malt pipe technique, meaning that manual work is absolutely essential here. If you are not careful enough, the spent grains can form channels in the lauter tun and then not be washed out properly. That's probably what happened here. We decided to accept the result, partly because time was pressing a little.
The brew was bitter-hopped with Herkules and whirlpool-hopped at around 80 °C with Spalt Spalter, a fine, more classic aroma hop. In principle, we could have boiled for a further hour, in which case the evaporation of water would have increased the original gravity to around 16 °P for approx. 90 liters of wort. The cooled brew was divided into two ZKGs and fermented in one bottom-fermenting at 12 - 13 °C with the Lallemand "Diamond Lager" in the second fermentation, and in the other top-fermenting with the "Mangrove Jack's M15", also in the second fermentation. The Diamond Lager ferments glucose, fructose, sucrose, maltose and maltotriose, the M15 does not ferment the latter. The top-fermented beer should therefore show a little more sweetness and achieve a lower alcohol content. We expect values of a maximum of 3.5% by volume for the top-fermented beer and a maximum of 4.5% by volume for the bottom-fermented beer.
As the tanks and fermentation vessels will soon all be filled with the beers to be brewed on June 25 and other brewing projects are still pending, the real Christmas bock cannot be brewed until the end of August at the earliest.

On the last day of the internship, three non-alcoholic (< 0.5% by volume) beers were brewed on June 25. There are various processes for producing alcohol-free beers in large breweries. In simple terms, they are brewed with reduced original gravity and after fermentation, the alcohol is removed from the finished beer in dealcoholization plants. Today's plants are so good that beers with 0.0% alcohol by volume can be achieved with a very good taste - no comparison to the first alcohol-free beers around 40 years ago, which the author of these lines still remembers well.
However, most smaller breweries and universities cannot afford such a technical and financial outlay, so alternative methods have been under development for many years. At the Research Center for Brewing and Food Quality at the Technical University of Munich, maltose-negative yeasts are being intensively researched and actively sought as part of the yeast hunt(s). For details, please refer to the habilitation thesis by Dr. Mathias Hutzler, who has earned an excellent reputation as "The Yeast Hunter". Such yeasts only utilize glucose, fructose and sucrose, but not the maltose, maltotriose and higher sugars formed during the brewing process.
When brewing with such yeasts, it is important to pay attention to a few points: it is particularly important that all vessels in the cold area are meticulously cleaned, as only a few cells of a normal yeast would multiply and then ferment the higher sugars. Furthermore, the original gravity should not exceed 7 °P if no more than 0.5% alcohol by volume is to be achieved. As there are only a few sugars to ferment, the so-called pH drop during fermentation is too low. The young beers are therefore not acidic enough to be microbiologically stable, and the unpleasantly bitter hop resins do not precipitate, which can make such a beer undrinkably bitter, especially when aroma hops are added. Sour malt or souring agents are therefore absolutely essential.

Specifically, we brewed 150 liters of wort in the Brewtools 150 Pro with Pale Ale malt, Carahell and a good 25% sour malt in an isothermal process at 72 °C. With an original gravity of 7.1 °P, it was a precision landing, so to speak. The bitter hopping was done with Herkules, the calculated bitterness should be around 20 IBU. The brew was divided into 3 fermentation vessels and fermented separately with Saccharomycodes Ludwigii (TUM SL17), Cyberlindnera Saturnus (TUM 247) and Cyberlindnera Amylophila (TUM 242). We deliberately refrained from using aroma hops so that we could later compare the taste of these three beers. The SL17 produces very drinkable pale beers with light honey aromas, the TUM 247 a pronounced pear aroma, the TUM 242 with its mild phenolic character comes very close to classic wheat beer yeasts.

On June 4, we brewed semi-experimentally. On our quite rocky road to low-alcohol IPAs, we again reached deep into our bag of tricks and tried to brew an IPA with no more than 4% alcohol by volume using isothermal mashing at 72 °C and briefly heat-treated hops. To do this, we produced a wort in the "Braumeister 50" with pale ale malt, which achieved an original gravity of 12.9 °P. The bitterness was adjusted during the boiling process with "Herkules", Ariana WetHop was added to the whirlpool at 85 °C, and the dry hopping was carried out with Citra, Simcoe and Wai-iti, which had previously been heat-treated in wort for just a few minutes. As hops have glucoamylases, alpha- and beta-amylase, the amount of which varies from hop to hop, the so-called "hop creep" would occur with untreated hops, i.e. the enzymes from the hops break down higher non-fermentable sugars into fermentable ones. Not only does fermentation then take several weeks, which is unusual for top-fermented beers, but there is also a risk that bottles that have not been stored sufficiently cool and not pasteurized will burst. For fermentation, we took the Windsor Ale from the tank of a maturing beer as a pitching yeast, and fermentation was almost complete on June 6. This yeast does not ferment the maltotriose, so the finished beer should have a "sweet" character with no more than 3.5% alcohol by volume.