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This year's practical course for the Master's module "Introduction to the Chemistry of Brewing" took place at the research brewery from August 26-29, 2024. In this practical course, the essential knowledge that is also required in larger breweries is taught on a small scale.
On the first two days, we brewed in two groups and cleaned the two large 250-litre tanks, Tank Siegfried and Tank Volker, using the CIP process, which is routinely used in the food sector. Before this, however, we emptied all six tanks and transferred the green beers to pressure kegs, whereby the small tanks of around 50 liters each were used for the third time for fermentation with the bottom-fermented Lallemand Brewing Diamond after draining the trub.
As all our tanks are now permanently sealed until later cleaning, their multiple use is ultimately only limited by the number of yeast feeds and the accumulating trub in the cone. As the bottom-fermenting yeasts used today are hybrids of Saccharomyces cerevisiae and Saccharomyces eubayanus, their yeast cells change with increasing cell division and, as a rule of thumb, bottom-fermenting yeasts can be used 5 times before they should be replaced by fresh yeast. In experiments, we have noticed changes in taste from the 6th pitch, so we use a yeast for a maximum of four pitches to be on the safe side.
We carry out CIP cleaning of the two tanks as follows. The trub drain is connected to the return flow of a pump, the flow of which is connected via a pipe on the tank with a spray head inside in the upper area of the tank. We start by rinsing the tank 2-3 times with drinking water, which roughly removes the residues. This is followed by an approx. 30-minute rinsing step with caustic solution at up to 50 °C, then 2-3 rinsing steps with drinking water. A rinsing step with an acidic solution at a temperature of up to 50 °C neutralizes the lye and removes alkaline deposits. After a further 2-3 rinsing steps with drinking water, a final one-hour rinsing step with 80 °C hot water is carried out for pasteurization, which reliably kills any yeast cells that may still be present.
If you only ever use one yeast in a tank, such as the widely used W 34/70, chemical cleaning is sufficient. However, we have had the unfortunate experience that it can happen in a tank that has only been chemically cleaned that yeast cells have survived somewhere, and if an alcohol-free beer is then to be brewed with a maltose-negative yeast, this will sooner or later be further fermented by the previous yeast. In previous experiments with maltotriose-negative yeasts, our purification concept has proved successful.
We brewed the following beers in this year's practical course:
- 2x 50 L Pilsner
- 2x 50 L Pale Lager
- Non-alcoholic Pilsner (max. 0.5% alcohol by volume)
- Non-alcoholic Pale Ale (max. 0.5% alcohol by volume)
On August 26, we mashed malt isothermally at 76 °C for 30 minutes in our BrewTools 150 Pro Pale Ale. After boiling with a bitter hop extract from Yakimachief and Sauergut, we obtained 115 liters with an original gravity of 11.1 °P. 50 liters of this wort were transferred to Tank Ulla after the whirlpool, we did not add any aroma hops, we deliberately wanted to brew a simple Pilsner. The remaining wort was spiked with the hop extract Dynaboost from Yakimachief in the Mosaic variant, and after another whirlpool, 50 liters were transferred to Tank Mathias. Both wort types were fermented at 12 °C with 1 bar spunding pressure, and fermentation was completed on August 31. We have brewed a Pale Lager like this before, and our beer friends found it to be very harmonious, with some telling us that it had a finer taste than a classic Pale Ale. We are looking forward to seeing how this Pale Lager turns out this time.
On August 27, we brewed Pilsner and Pale Lager again, the recipes were identical to the previous day. However, this time the mashing took place in our BrewTower 140+, which has an agitator supported by a pump for circulation. In the isothermal high-temperature mashing process, fast and lump-free mashing is important, and we have often observed that beers produced using the malt pipe technique have a slightly higher alcohol content in comparison. There was no difference in the original gravity with the same amount of ingredients; 11.1 °P was also obtained here. The wort was boiled in the BrewTools 150 Pro. The Pils is fermented in Tank Martin, the Pale Lager in Tank Alex.
Large breweries produce non-alcoholic pilsner beers in a very complex and energy-intensive process. As a rule, a beer with a reduced original gravity is brewed, from which the alcohol is then removed in a reverse osmosis system. The current lower limit is 0.03% alcohol by volume, whereby the legislator defines alcohol-free beers in Germany as those with an alcohol content of less than 0.5% vol.
Beers de-alcoholized to 0.03% alcohol by volume have a watery character, which is why unfermented wort is added to these beers to achieve a certain sweetness; outside Germany, sugar or sweetener is also added. Incidentally, we can easily detect the addition of wort analytically using high-performance liquid chromatography. As flavorings are also lost during reverse osmosis, the beers are hopped again, resulting in highly drinkable non-alcoholic beers. The technology continues to develop, and a Bavarian brewery has launched a non-alcoholic Pilsner on the market that raises the bar for non-alcoholic beers yet again.
For us as a research brewery that is completely dependent on state and third-party funding, it is of course illusory to dealcoholize beers. In cooperation with our colleagues at the Technical University of Munich in Freising-Weihenstephan, we are therefore taking a different approach and using maltose-negative yeasts for fermentation, for our Pilsner the Saccharomycodes Ludwigii, which can only utilize glucose, fructose and sucrose.
On 28 August , we produced a wort with 6.8 °P from 50% Munich malt and 50% Pale Ale malt in the BrewTools 150 Pro using the isothermal high-temperature mashing process. The wort was boiled with a bitter hop extract from Yakimachief, for the aroma we used an aroma hop extract (Perle) from Eisemann, the wort is fermented in Tank Siegfried. As maltose-negative yeasts hardly cause a drop in pH, we added enough sour grains to achieve a microbiologically safe pH value of less than 4.5 in the finished beer. The fermentation is carried out under pressure, and unless we have picked up a foreign yeast somewhere, the beer will not contain more than 0.5% alcohol by volume.
We pasteurized the last non-alcoholic beers, but this time we want to ferment the non-alcoholic beers under pressure and later filter them to remove all yeast cells. Earlier preliminary tests have shown that our candle filter completely removes the yeast, at least there was no evidence of secondary fermentation in unpasteurized beers. Alcohol-free beers are now being requested more frequently, and in a preliminary test we also succeeded in producing a beer with 0.0% alcohol by volume.
On August 29, we basically repeated the experiment from August 28. As our aim was to brew an alcohol-free pale ale, we decided against aroma hopping with "Perle". Instead, we used the Yakimachief hop extract Dynaboost in the Mosaic and Citra variants for the whirlpool. For the dry hopping in Tank Volker, we used up our leftover Barth Haas Spectrum product (Galaxy and Citra) and emphasized the aroma with Yakimachief hop extract Hyperboost in the Mosaic variant. This beer is fermented with the Lallemand Brewing LoNa, which, like the Saccharomycodes Ludwigii, ferments glucose, fructose and sucrose. At 6.8 °P, the alcohol content should be below 0.5 % vol. In our opinion, LoNa is a very good yeast for producing non-alcoholic Pale Ale beers. This pale ale is also fermented under pressure and is to be filtered later.
Towards the end of September, the second part of the internship takes place, in which we analyze beers and bottle them under counterpressure, followed by a sensory evaluation.
But which of these beers are actually beers in the sense of the so-called provisional beer law of 1993? We have already reported on this on this website, and it is an interesting German curiosity. Outside of Germany, all of these beers would also be beers in the legal sense. Under our provisional beer law, however, we are only allowed to call the two Pilsen beers "beer". The Pale Lager, the non-alcoholic Pale Ale and also the non-alcoholic Pilsner are to be described as bottom-fermented (Pale Lager) or top-fermented beer specialties, or even just as beer specialties, in accordance with a recommendation of the German Brewers' Association. And what the specification "Brewed according to the German Purity Law of 1516" means in reality will be discussed in the summer semester in the lecture "Theory and Practice of Beer Brewing".