Non-microbiological turbidity of beer: Part 2 – a case study

Non-microbial beer turbidity of lager beers often indicates a technological problem. Therefore, the occurrence of permanent haze in filtered and stabilized beer should not be underestimated. In this study, practical examples from industrial breweries, where several types of non-microbiological haze of colloidal were identified, are presented. These examples of haze were caused by slightly different factors, and as a result, they had a different microscopic image. It is often accompanied by mechanical impurities and sometimes by microorganisms that function as nucleation centers. Moreover, a very interesting example of almost brilliant permanent beer haze caused by the destruction of yeast cells with the following pouring intracellular contents of cells into beer is introduced. This phenomenon, which could be called “precedent”, was caused by a bad physiological condition of yeasts cells and inappropriately chosen yeast separation technology.

Finding correlations between hop catalogs and real hoppy character in brewery conditions

Brewing recipe design is mainly based on brewer’s expertise, information available in catalogs and certificates of analysis (CoA’s). Hop schedule design and formulation has become an essential topic since hoppy craft beers took the scene. But how accurate is the flavor profile information provided in catalogs? How useful is the chemical composition profile information in CoA’s? Besides current research and tons of reported experiences, hops impact is still a mystery, and topics like biotransformation are black-boxes for brewers. In this study, nine single hopped beers were brewed, and a trained panel conducted sensorial beer analysis. Then, to asses hop impact, qualitative and process-related-quantitative beer characteristics were contrasted to find valuable correlations and trends between hop catalogs and final beers. Discrepancies with catalog qualitative data were reported. In addition to what is already described in the literature, here we describe how α-acids, linalool, myrcene, and geraniol (despite the classical use for these compounds) could predict positive and negative hop impact of nine different hop varieties on bitterness, flavor, and aroma, when they are applied in different brewing process steps. Also, with this pipeline we stand the basis of a tool to be improved, available for brewers, to better predict their brews and assess new hop varieties in real-life pilot brewing set ups.

Determination of gushing potential of barley

A new control method for the determination of the malting barley susceptibility to gushing was developed. The method is based on the modified Carlsberg test (MCT) after prior stimulation of barley with substances that promote the germination process. Barleys from the harvest of 2020 and malts produced from them were used to develop and verify the method. The selection of barleys was based on the results of gushing potential detected in the produced malts. To optimise and verify the method, the barley variety Sunshine with a high gushing potential of both barley (139±33 g) and malt (144±13 g), and the barley variety Pionier with zero gushing potential of both barley and malt were used. Malt was produced from the Lodestar barley variety with a high content of the mycotoxin deoxynivalenol. Gushing of the malt was 127±10 g. The gushing potential in barley was determined by the MCT method after prior stimulation of germination. For comparison, the gushing potential was also determined by the MCT method without stimulation of germination. It was proved that stimulation of germination is a key process for correct determination of the susceptibility of barley to gushing. The newly developed method was used for the determination of the gushing potential of five barleys from the harvests of 2020 and 2021. Control gushing determination of five malt samples was performed using the MCT method. An agreement between the measured data was found.

Evaluation of Czech hop varieties in beer

New hop varieties were evaluated in brewing tests in the years 2020 and 2021. The Saaz Comfort, Saaz Shine, Saaz Late and Saaz fine aroma hops were compared in lager style beers. Saaz Comfort has the best evaluation in terms of overall popularity. With a 95% probability, its evaluation is different from that of Saaz Shine. Saaz Comfort has a considerably different evaluation of bitterness than Saaz Late and Saaz Shine. The results show that fine aroma hop varieties have different characteristics and thus do not compete with each other. Kazbek and Cascade were compared in lager and ale beer styles. No significant difference was determined in the lager style. However, a significant difference between Kazbek and Cascade was established in ALE. Gaia has a considerably better evaluation in the lager style than in ALE. Gaia has the best evaluation of aroma and bitterness in lagers with dry hopping.

Honey Mead Fermentation from Thai Stingless Bee (Tetragonula leaviceps) Honey using Ethanol Tolerant Yeast

Honey mead is a well-known conventional alcoholic beverage made by microbial fermentation of diluted honey. The selection of prospective yeasts for inoculation of honey-must with regard to honey mead quality determines the quality of mead production. The yeast consortium tolerant to ethanol stress was selected for this study using an enrichment technique. The activity of the invertase enzyme and the level of ethanol tolerance have been investigated. Thai stingless bee honey was used as a substrate, and the selected ethanol tolerant yeast consortium was used for mead fermentation. The results revealed that the PP03 had the highest invertase activity of 75.13±9.16 U/mL and the highest ethanol tolerance level of 12%. This is the first study using an ethanol tolerant yeast consortium to ferment honey mead from Thai stingless bee honey.

The role of acetic acid bacteria in brewing and their detection in operation

Acetic acid bacteria (AAB) are often considered a threat of the past because today’s equipment allows to perform post-fermentation processes under greatly reduced level of oxygen. This paper deals with the current importance of AAB in brewing. The risk of contamination as well as functional role in spontaneously fermented sour beers is reviewed. The main harmful effect of AAB lies in the direct spoilage of draft beer and formation of biofilms, most often in dispensing systems. On contrary AAB seems to be indispensable in the case of sour beer production. A key issue of AAB in brewing environment is their (early) detection and identification. Therefore, part of this study is devoted to both the latest sophisticated methods and also those of traditional cultivation. which are still prevalent in operating laboratories due to their cost and easy implementation. Finally, the experimental and pictorial material is added as a guide for operations that have less experience with AAB.

Miniaturized and improved method for Apparent Total N-Nitroso Compounds determination in beer

A miniaturized and improved method for Apparent Total Nitroso Compounds determination in liquid matrices was developed. The main improvement is based on a miniaturized and modified apparatus for chemical denitrosation of nitroso compounds by hydrogen bromide in a glacial acetic acid mixture. The reaction is carried out in a teflon reaction coil while the reaction product, gaseous nitric oxide, is drifted to a chemiluminescence detector by the flow of argon together with a vacuum obtained by the detector's oil pump. The apparatus significantly increased the efficiency of the Apparent Total N-Nitroso Compounds determination (compared to the previous method), specifically, the dead volume of the apparatus was significantly decreased, and the effect of the reverse reaction was eliminated as well. The apparatus shortens the analysis time (1.4 min/injection), further it provides a lower detection limit (3 μg(N-NO)/l), quantification limit (10 μg(N-NO)/l), and method uncertainty (15%), and is simpler for the operation.

Brewing tests of new fine aroma hop varieties (Humulus lupulus L.) Saaz Brilliant, Saaz Comfort and Saaz Shine

Characterization of varietal profiles of hop secondary metabolites in beer is of considerable importance for hop growing and brewing. This three-year study focused on pilot brewing tests of three new Saaz derived hop varieties, namely Saaz Brilliant, Saaz Shine and Saaz Comfort. The sensory profiles of kettle and kettle+dry single hopped beers were monitored. At the same time, the impact of dry hopping technology on sensory perception of final beers and changes in volatile compounds was investigated. Pilot brews (200 l) of 12% pale lager were prepared in kettle and kettle+dry variants using the new Czech varieties and traditional Saaz as a control sample. Essential oils in beers were determined by GC/MS-MS method with the aim to clarify links to the beer sensory profile of both, kettle and dry hopping mode. The descriptive sensory method of hop-derived aromas and the triangle tests were employed to determine the sensory quality of beer. The overall sensory impression of beers from all tested varieties was at least comparable to traditional Saaz, and Saaz Comfort even reached better evaluation. The profile of essential oils and hop flavours in beer was partially different, however it was not rated worse than Saaz. The kettle+dry hopped beers of new varieties were significantly different from Saaz in the triangle test, Saaz Brilliant was preferred over the Saaz. The results showed considerable potential of new varieties for the production of interesting and taste-specific beers and the enrichment of the spectrum of fine aroma varieties of Czech hops.

Non-microbiological turbidity of beer: Part 1 – semireview

Beer is a complex mixture consisting of hundreds of chemical substances. Some of them are macromolecules, such as proteins and polysaccharides that together with polyphenolic compounds form poorly soluble complexes causing beer turbidity or cold colloidal turbidity. Furthermore, beer turbidity can be caused also by procedural particles entering into beer during brewing process (filtration and stabilization aids) or by foreign particles from external environment (mechanical impurities). If turbidity, sediment or individual particles occur in filtered and stabilized beer, their origin must be determined since brilliant visual impression of the filtered beer influences an opinion of customers on a specific product. The identification of different species of turbidity using microscopic image, particle staining, enzymatic analysis or identification precursors is clearly described in this paper. The study includes pictorial documentation of various particles that may be part of beer turbidity.

Analysis and prognosis of bitter acids content in Czech hop varieties – year 2020 and long-term comparisons and trends

The article deals with the harvest forecast of the content of bitter acids in Czech hop varieties harvested in 2020. This is presented in the context of long-term trends in the content and composition of bitter acids analogues and the stability of the varietal characteristics in the aforementioned harvest. This analysis is usually available at the end of the calendar year. 180 hop samples were analysed using EBC 7.7 (HPLC) method. The α-acids content in the most important variety of Saaz (3.65% in dry matter) was 12.8% rel. higher than in the 2019 harvest and 4.2% rel. higher than the 28-year average. The α-acids content in Saaz Late (3.23%), Sladek (7.9%), Kazbek (6.4%) and Agnus (12.4%) was significantly higher than both the long-term averages for the varieties and the harvest of 2019. The Premiant (8.0%) variety was close to the long-term average. The ratio of α-/β-acids, the relative content of cohumulone and the relative content of colupulone were consistent with long-term averages of the tested varieties. It was confirmed that the harvest forecast provides timely information on the α-acids content of the given harvest, the results being in good agreement with the values of the final evaluation of all harvested hops.