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On August 28 and 29, 2023, the practical course took place as part of the "Introduction to the Chemistry of Brewing" module, in which seven brewing enthusiasts took part. On the first day, we brewed a total of four beers in the research brewery, which should contain a maximum of 0.5% alcohol by volume.
The legislator has defined this content as the limit for alcohol-free beers. The background to this is that, if there is no alcohol dehydrogenase deficiency and no alcohol allergy, it is in fact impossible for an adult to drink enough of such a beer to build up an alcohol content that is unfit for consumption. With a degradation rate of 0.085 - 0.1 grams of alcohol per kg of body weight per hour, depending on gender, absorption and degradation are largely in balance.
For small breweries, but also for our research brewery, the effort to dealcoholize normally brewed beers is neither space-wise nor financially feasible, not to mention the experience advantage of large breweries. However, there are so-called maltose-negative yeasts that only convert sucrose, fructose and glucose from the sugars formed during the mashing process, but not maltose, maltotriose and higher sugars.
To avoid brewing a sweet beer, the original wort is reduced to approx. 7 °P. In the case of isothermal high-temperature mashing, there is also no cleavage of sucrose and, in our experience to date, the amount of glucose formed is reduced compared to a classic infusion process, while at the same time the higher sugars that are important for full-bodiedness are enriched.
One 11 kg and one 12 kg of Pale Ale malt were mashed in a 50 l mash tun with agitator. The resulting wort was then diluted to a good 100 liters and boiled for one hour together with sour grains and hop extract. Since fermentation with maltose-negative yeasts does not result in a sufficient pH drop, which prevents the precipitation of undesirable bitter substances from the hops, the lactic acid content is adjusted to approx. 700 mg/L. Before transferring to the respective fermentation vessel, which MUST be meticulously cleaned and sterilized with wet steam in order to reliably kill any maltose-positive yeasts present, the original wort was adjusted to around 7 °P by dilution.
The two brews are fermented with:
1) Saccharomycodes Ludwigii
2) Cyberlindnera Misumaiensis
This was hopped quite vigorously in order to achieve a bitterness of approx. 35 IBU units. Cyberlindnera Misumaiensis does not ferment sucrose, so that an alcohol content of less than 0.5 % vol. should be achieved with this original gravity. Both beers should be in the direction of a "pilsner".
3) Cyberlindnera Saturnus
4) Lallemand Brewing "LONA"
The wort for these two yeasts was hopped much milder with approx. 20 IBU units. The Cyberlindnera Saturnus produces a distinct pear aroma, while the "LONA" is described as having a very neutral fermentation. We added the hop extract "Spectrum" from Barth-Haas in the "Citra" variant to the latter wort to produce an alcohol-free pale ale.
When brewing with maltotriose-negative or maltose-negative yeasts, strict care must be taken to ensure that no common yeasts are present in the fermenting wort, so everything that comes into contact with wort must be meticulously sterilized beforehand. Unwanted foreign yeasts would result in the fermentation picking up speed again after the actual end. Maltose- and maltotriose-positive yeasts would multiply in the wort and at some point begin to ferment maltose and maltotriose.
This can be reliably detected using high-performance liquid chromatography, and the beers would then reach approx. 1.5% alcohol by volume instead of the expected approx. 0.5% alcohol by volume. We will know in a few weeks how successful we were in cleaning the fermentation vessels. The manufacturers of the yeasts also expressly recommend pasteurizing these beers to prevent secondary fermentation in the bottle or keg and their possible bursting. According to the Pasteur formula for beer, which was developed from many experiments at the time, and a target value of approx. 15 pasteurization units (PE) to kill yeast cells, it is sufficient to heat these beers to 60 °C for around 15 minutes:
PE = t min * 1.393^(T °C - 60 °C)
At 65 °C, only around 3 minutes would be required. In reality, more PE is achieved because no beverage can be heated from a lower starting temperature to the target temperature infinitely quickly, left there for the specified time and then cooled back down to the starting temperature infinitely quickly. The topic is quite complex, as the number of yeast cells also plays a role, and there are also other formulas for other beverages, so please refer to the relevant specialist literature at this point.
On August 29, a "Helles" was brewed under the guidance of master brewer Siegfried Opperman at the Zellerfeld Brewing Academy in regular operation.
The so-called high-short infusion mashing process was used, and after hop boiling, 280 liters of wort with 12.1 °P were obtained. This wort is fermented together with already fermenting green beer with a bottom-fermenting Pilsener yeast in a cylindrically-conical fermentation vessel with a capacity of around 1000 liters at 10 °C, and the main fermentation will take around 10 days. As part of the internship, it was also possible to learn how everyday brewing is carried out in a commercial microbrewery.
After our short summer break, we resumed brewing on August 16. As previously reported, we are comparing the isothermal high-temperature mashing process with classic methods such as the so-called high-short mashing process used in large breweries, and we have now repeated these comparative tests and will have to repeat them again. First of all, the deviations from the first series of tests during mashing are only slight, which speaks for good reproducibility.
In science, it is imperative to repeat tests in order to rule out misinterpretations, and with three identically performed tests you usually achieve a good database. The fact that results rarely agree 100% is due to random errors alone, which lead to results that are more or less scattered around a mean value. To be on the safe side and to rule out systematic errors, experiments should ideally be carried out by different people, even if this is difficult per se in the context of theses. In the case of a doctoral project tailored to one person, it can even prove to be very difficult to have a result checked by another person, as the expertise is quite individual and the wealth of experience also grows during the scientific work.
In addition, scientific progress must be demonstrated for the completion of a doctoral project. In times of Impact Factor, Hirsch Index and the like, which only reflect quantitative parameters but not qualitative ones, the question arises as to how the results of time-consuming experiments are to be seen in such a context. If you are dealing with a chemical synthesis, the effort involved in repeating it twice may be manageable. In physical chemistry or experimental physics, however, the time required can vary greatly.
Let's take photoelectron spectroscopy as an example, which is also of interest in the analysis of beer foams. Once you are familiar with this technique, which requires a learning phase of several months, you need one day to prepare and carry out an experiment; a similar amount of time is required for an experiment with atomic force microscopy. It is therefore quite possible to repeat such experiments twice in a week of experimentation, followed by more or less time-consuming data analysis. This always assumes that the equipment is working and that there is no external interference. With in situ scanning tunneling microscopy, the effort involved can be considerable, and if you are unlucky, the experiment is already over after the probe has approached the sample, and then you have to start all over again.
But what is it like in the brewery? Colleagues who deal exclusively with brewing science are often accused of publishing too little and having too few Hirsch indices. At non-university research institutions or at foreign universities, the allocation of funding is often linked to such quantitative parameters, and the Anglo-American slogan "Publish or perish!" is actively practiced. Is it possible to write 100 publications per year in brewing, as some groups in chemistry or electrochemistry do? Let's take a look at the time required in a large brewery. The mashing and lautering process for a typical Pilsner beer takes 2 - 3 hours, depending on the brewing process, followed by a one-hour boil.
In a multi-unit brewhouse, a brew can be completed after 4 - 5 hours, and in shift operation a brewery could produce up to 5 brews per day. This is followed by approximately one week of primary fermentation, followed by approximately four weeks of secondary fermentation. The beer is then filtered and bottled. All in all, it takes around 6 weeks from brewing day to bottling.
In our research brewery, where we do not (yet) filter, the entire process until a bottom-fermented beer has matured takes a good 8 weeks, especially as our tank capacities are limited. During this time, all the analytical work is carried out, such as Determination of free amino nitrogen (FAN) Sugar distribution using high-performance liquid chromatography and enzymatic methods as well as viscosity. Finally, the fermented beers are examined in detail with regard to fermentation by-products, lactic acid and microbiological purity and subjected to a sensory evaluation (aka "tasting").
All these processes and examinations are repeated twice to ensure that the results also survive a peer review process. And who knows what additional experiments will result from the peer review. It is therefore not surprising that in chemistry an experiment can be carried out three times and fully evaluated after 4 weeks, whereas in brewing such a series of experiments can take up to 6 months.