Unconventional yeast and dark malts. Beer making 101

• Researchers used bottom- and top-fermenting yeasts and unconventional strains
• Research results can be used in designing beers
• Beer technology with improved health benefits has been developed at the university
• Postgraduate studies in brewing are increasingly popular
• The Academy of Good Beer is the only such competition in the academic environment
• A university brewery will begin operating at the Regional Product Centre this year

Barley, hops, water and yeast – four ingredients without which there is no beer. The key to beer production is yeast, the living organisms that make the fermentation process take place. In addition to ethanol and carbon dioxide, this produces the compounds that give beer its flavour and aroma. Justyna Paszkot, Alan Gasiński, Joanna Kawa-Rygielska from the Department of Fermentation and Cereal Technology investigated how yeast can be used to improve the sensory quality of this popular beverage. The results of the study 'Evaluation of volatile compound profiles and sensory properties of dark and light beers fermented by different strains of brewer's yeast' were published by 'Scientific Reports', a highly-regarded journal belonging to the publication 'Nature'.

From light to dark, bottom to top

– For the purposes of the study, we produced eight beers at the university, under laboratory conditions. Four light, based on pale Pilsner malt, and four dark, with the addition of dark special malt – says Justyna Paszkot. The article is her fourth and final publication related to her PhD. A series of studies conducted as part of her PhD thesis looked at the effect of dark malts on the content of phenolic compounds, on antioxidant properties and on the course and effects of fermentation.

– We have shown that the addition of dark malts to the wort increases the content of phenolic compounds and free radical scavenging capacity. We also determined the effect of successive stages of the beer production process, including fermentation with yeast strains with different characteristics, on the content of these valuable compounds. We showed that the fermentation process can lead to an increase in antioxidant properties – says the author.

This time, the contribution of different yeast strains and the effect of dark specialty malts on the volatile compound profile and sensory quality of the beer were tested. A bottom-fermenting yeast strain Saccharomyces pastorianus (lower temperature range, 5-13 degrees), a top-fermenting strain Saccharomyces cerevisiae (15-20 degrees) and unconventional strains were used for fermentation. Saccharomyces cerevisiae of the kveik type is isolated from a group of microorganisms used in the production of traditional Norwegian beers, and the yeast Saccharomyces cerevisiae var. Diastaticus, by its high ability to attenuate wort carbohydrates and its unusual sensory profile, has often been treated in breweries as an undesirable microbial contamination.

The beers were assessed in two ways. First, by gas chromatography, for the content of volatile substances that build flavour and aroma. These depend on the composition of the wort, the strain and dose of yeast and the conditions of the fermentation process. Fifty-eight compounds were identified, mainly from the group of alcohols, esters, aldehydes, terpenes and terpenoids, and ketones.

Sensoric in a strict regime

At the next stage, the drinks were tested not with equipment, but through the human senses. During sensory analysis, the team from the Department of Fermentation and Cereal Technology took into account clarity, colour, frothiness and carbon dioxide saturation. According to a proprietary questionnaire, the perceptibility of the basic beer flavours – bitter, sweet and sour – and their accompanying aromas was assessed. It takes a special kind of experience to detect caramel or roasted notes from malt, or citrus or herbal notes from the addition of hops. Such nuances can only be perceived by sensory experts, who first have to develop the right sensitivity and then train their sensory memory and take care of their senses. This is important, especially if you want to spot flaws in a product. Skills go hand in hand with a regime: a sensoryist can’t smoke cigarettes, drink strong coffee, use hot spices or taste-altering drugs.

– Strong alcohols and esters shape the perceptibility of the sour taste and alcoholic aroma, while malt-derived aromas are mainly related to the aldehyde content, explains Justyna Paszkot. Large differences in the composition of volatile compounds were observed between beers fermented with different yeast strains. Top-fermented beers had the most volatile compounds, while bottom-fermented beers had the least. Conclusion: the composition of beer volatile compounds was more influenced by yeast than by the addition of dark special malt.

– The results are of an applied nature. They can be used in the design of beers to bring out specific characteristics and increase sensory appeal through the selection of biological material. In addition, our research has shown the potential of unconventional yeast in the production of dark beers, which has not been investigated before, adds the author. She plans to continue her research on the effects of fermentation on antioxidant properties and the content of phenolic compounds.

With lentils instead of barley

Researchers from UPWr have been conducting a number of brewing projects for a long time. They have developed technology for gluten-free beers based on malts made from legumes. People with coeliac disease often replace grains with legumes that do not contain gluten. They can buy gluten-free pasta or baked goods, but they cannot drink beer, which is usually based on barley malt. For several years, scientists in Wrocław have been producing unusual malts from legume seeds, which can be used to successfully produce gluten-free beers.

The Department of Fermentation and Cereal Technology has also developed a beer with grape pomace. It is based on the use of by-products from the wine industry, in line with the trends of a closed-loop economy. "Grape Beer" is darker, has a fruity aftertaste and more flavonoids, i.e. high antioxidant potential. It significantly reduces levels of acetaldehyde, a toxic compound formed during fermentation, excess of which deteriorates beer quality.

Research is also underway at the university on low- and non-alcoholic beers using unconventional yeasts belonging to genera other than the standard Saccharomyces brewing yeast and sour beers with the addition of yeast and lactic acid bacteria. A beer with a higher xanthohumol content has also been developed. This is a flavonoid that the scientific world has recently become interested in: it has several times the free radical scavenging capacity of vitamin C, and has anti-inflammatory, anti-viral and anti-cancerogenic effects. It is only found in hop cones, but is sensitive and is broken down in the beer-making process. – We have been able to design a method of extracting beer in which xanthohumol is present in concentrations with proven health-promoting effects. This is one of the achievements that I am particularly pleased about – says. Prof Kawa-Rygielska.

Her team has also developed methods for managing by-products of the brewing industry, such as thresh and yeast waste biomass. Together with members of the UPWr fermentation team, Prof. Kawa-Rygielska implemented the project 'University-Industry Cooperation in Fermentation Technologies in Poland', with research centres in Belgium, France, Germany, Portugal, the UK and Italy. As a result, new technological solutions for the brewing industry were brought to Poland and International Schools of Fermentation Technology were initiated.

New university brewing projects are usually developed in collaboration with business, and their results have been applied many times in industry; some recipes have been implemented permanently. –  As part of our master's theses and doctoral theses, we solve technological problems for entrepreneurs – adds the professor.

Beer studies for enthusiasts and professionals

Also, together with brewers, the first postgraduate studies in "Brewing technology" in Poland were established at the  Wrocław University of Environmental and Life Sciences in 2016, awarded by the Association of Brewing Employers in Poland , "Browary Polskie". Right from the start, interest was so high that places in the first intake ran out after a week. Professionals, including employees of regional and restaurant breweries, creators of small craft breweries, as well as enthusiasts, apply for these courses. Some learn for pleasure, developing hobbies and looking for new flavours. The more experienced want to develop their skills and seek guidance at university.

– After the year 2000, a beer revolution began in our country. Firstly, home brewing developed strongly, and then some of the enthusiasts turned it into a business, opening the first small breweries – says Prof. Kawa-Rygielska, head of the study, which is a response to the growing needs of the market. There is a growing number of breweries that need educated employees. Adepts of brewing learn the technology of production of top and bottom fermentation beers, instrumental and sensory analysis. They learn how to set up their own mini-brewery, what equipment to use, how to manage quality, and how to take care of marketing. They explore the legal and economic aspects of beer production in Poland and the European Union. Theory is complemented by practice: in the brewing workshops, students have to design the entire beer production process. At the end, the effects are evaluated and conclusions are drawn from mistakes.

– Graduates set up their own businesses. For example, one person studied in one edition of the degree programme and his daughter in the next. Now, they opened a small family brewery together – says the professor.

Others easily find work in breweries in Poland and abroad. Well-known Wrocław brands such as Zloty Pies and Browar Stu Mostów also employ our university graduates. An interesting fact is the new Wrocław cafe Chmiel Kawę was created by UPWr graduates who serve coffee with hops. In the oldest gastropub in Wrocław, Piwnica Świdnicka, which celebrated its 750th anniversary in June, a unique beer was reconstructed according to a historical recipe to mark the jubilee. The author of the reconstruction and head brewer of the Cellar is also a graduate, Gniewko Drewnicki.

No alcohol, but citrus and honey

Every year, new breweries and new beers appear on the market. According to the Beer Crossover portal, in 2021, 38 new breweries were established and 2368 new beers were produced, more than the year before. In 2022, there were 286 active commercial breweries. 18 breweries are owned by the four largest brewing groups, whose combined production amounts to around 90 per cent of the market. About 9 per cent is owned by medium-sized and regional breweries, and about 1 per cent by the smallest craft and restaurant breweries.

How do you orient yourself in this multitude of beers? Quality is guaranteed by the prizes awarded by the Academy of Good Beer. This is the only beer competition of this size in an academic environment. – The idea was initiated in 2017 by the then rector Prof. Roman Kołacz – says Prof. Kawa-Rygielska, co-initiator and president of the Academy. – 'We are keen to promote high quality and bring hobbyists and professionals together – she adds.

The beers are judged by academy staff and experienced judges. The chairman of the judging panel is Rafał Kowalczyk, a juror of international competitions, including the World Beer Cup and Great American Beer Festival in the USA, the International Beer Cup in Japan. The evaluation of the beers takes place in accordance with the guidelines of international and national organisations related to brewing. All samples are coded, poured into identical glasses and cooled to 10 degrees.

Out of 80 beers submitted by brewers from all over Poland, seven from each category made it to the finals: beers brewed by students and graduates of the 'Brewing Technology' postgraduate course as part of brewing workshops, freestyle beers brewed by home brewers, beers in classic styles brewed by breweries, beers in new wave styles brewed by breweries, non-alcoholic beers brewed by breweries. The level was high and the winners were decided by nuances: the quality of hop bitterness or the balance between sweetness and bitterness. Beer is a complex product: some characteristics are disadvantages (sulphurous notes, too much fruitiness in classic styles, pronounced alcoholiness), others are advantages: hoppy, malty, citrusy notes at the right level, balanced bitterness. Whether a particular compound is an advantage or disadvantage depends on the particular beer style. Light creamy and buttery notes resulting from the presence of diacetyl are acceptable in Czech pils, while in German pils, on the contrary, they are a disadvantage.

This year's highlight was Grodziskie beer, based on traditions dating back to the Middle Ages, on malt smoked with oak wood. Berliner Weisse is lagered with the addition of lemon and orange peel, and Sugar beer with the addition of honey. This is the first time that non-alcoholic beers have entered the competition. They are technologically challenging because they contain no alcohol, which promotes microbial contamination and reduces their shelf life, while still having the taste and aroma of classic beers. This is a new trend and the fastest growing group of beers.

During the Academy, not only quality is assessed, but also compliance with the style. More than a hundred styles are included in the best-known catalogue compiled by the BJCP. This is a non-profit institution that categorises beer styles and provides sensory training for judges.

Brewing under the Korns

Poland is the leading producer of beer in Europe, after Germany and the United Kingdom, and brewing is one of the most innovative branches of our food industry.

The activities of the Wrocław University of Environmental and Life Sciences are part of this trend. These include not only research and educational projects, postgraduate studies and the Academy of Good Beer. The university also co-organises the largest National Brewing Congress in the country and the Autumn Brewing Workshop, as well as sensory training courses. – The university's brewery will be launched later this year –announces Adam Głowacki from the Faculty of Biotechnology and Food Sciences, one of the coordinators of the project. – It will be a small-scale production, but on very professional equipment. With a three-cavity brewhouse for the production of wort from various types of malt, fermentation tanks where the yeast conducts the fermentation process of the beverage, which will then be aged and pasteurised and bottled.

The brewery will operate at the Regional Product Centre. This is a place where brewers, cheese makers, winemakers and other producers of food, often produced on a small artisanal scale, will be able to use the laboratory and scientific base. – Our experts will help, for example, with the design of new products, the development of new production technologies for beer, wine, cheese, bread, herbal and meat products – adds Adam Głowacki.

The CPR, along with the brewery, is located in the university's Education and Development Centre, in the historic palace and park complex in Pawłowice. It used to be the seat of the Korn family, well-known publishers and patrons of the arts. Above the portal of the palace, their ancestral motto candide et caute, nobly and prudently, is still visible, which could also be the motto of today's brewers. Today, it is a place where modern technology and history come together. Also the history of a beverage whose origins go back to ancient Assyria and Babylon and which is doing ever better.

Aneta Augustyn

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