Hopped Wort Research Articles

Study on the effect of malt and decoction mashing on polyphenols and antiradical power of wort

Mashing is one of the key operations in beer brewing. Together with polyphenolic compounds it can affect the quality and stability of beer. In our pilot brewing trials of pale lager (200 L), malts of three barley varieties were compared using either infusion or double decoction mashing. Total polyphenols, anthocyanogens and flavanoids were determined in sweet and hopped wort. Free phenolics were measured by HPLC coupled with coulometric detection. Antiradical power was determined by RC-DCPI, ARA-DPPH and ESR-T150 methods. In this way the influence of mashing method and barley variety on polyphenols and antiradical activity of sweet wort was demonstrated showing that the effect of mashing was stronger (ANOVA). The results showed significantly higher, i.e. by tens of per cent, levels of all polyphenols studied in both the decoction sweet wort and hopped wort. The decoction process resulted in higher levels of the antiradical power, ARA-DPPH (37–47%) and RC-DCPI (25–60%). A cluster analysis partitioned 28 free phenolic compounds in sweet wort primarily by variety and secondarily by mashing. The Malz malt showed a greater increase in polyphenols, free phenolic compounds and antiradical power in the decoction process compared to the Bojos and Sebastian malts. Decoction mashing introduces higher levels of phenolic antioxidants into the beer with the potential to improve the sensory stability of the beer and provide health benefits to the consumer. The different behaviour of malts and barley varieties needs to be better elucidated in further research.

Optimization of beer mixed fermentation using Saccharomyces cerevisiae and Lactobacillus brevis

Mixed fermentation is one of the methods used in sour beer production. The process requires initialization of the fermentation step by well-planned addition of brewing yeast and lactic acid bacteria to slightly hopped wort. The final product’s properties strictly depend on how the microorganisms are pitched and the initial wort composition. The experiment was performed to evaluate the impact of different initial conditions and pitching methods on the mixed fermentation process and the final product’s characteristics. With the aim of limitation of the number of experiments, the Box–Behnken design was applied. Three independent factors were considered while obtaining the response surface: initial extract, bitterness and order of pitching. The final product’s properties: ethanol and lactic acid concentration, appeared to depend strictly on initial conditions and pitching order. Several important observations have been made; for example, it appeared that the presence of LAB does not significantly impact the final ethanol concentration. Optimal conditions for obtaining the maximum or minimum of each quality were calculated using Matlab. Obtained results might improve the sour beer production process while shortening the duration and reducing the usage of ingredients.

Sour Beer as Bioreservoir of Novel Craft Ale Yeast Cultures.

The increasing demand for craft beer is driving the search for novel ale yeast cultures from brewing-related wild environments. The focus of bioprospecting for craft cultures is to identify feral yeasts suitable to imprint unique sensorial attributes onto the final product. Here, we integrated phylogenetic, genotypic, genetic, and metabolomic techniques to demonstrate that sour beer during aging in wooden barrels is a source of suitable craft ale yeast candidates. In contrast to the traditional lambic beer maturation phase, during the aging of sour-matured production-style beer, different biotypes of Saccharomyces cerevisiae dominated the cultivable in-house mycobiota, which were followed by Pichia membranifaciens, Brettanomyces bruxellensis, and Brettanomyces anomalus. In addition, three putative S. cerevisiae × Saccharomyces uvarum hybrids were identified. S. cerevisiae feral strains sporulated, produced viable monosporic progenies, and had the STA1 gene downstream as a full-length promoter. During hopped wort fermentation, four S. cerevisiae strains and the S. cerevisiae × S. uvarum hybrid WY213 exceeded non-Saccharomyces strains in fermentative rate and ethanol production except for P. membranifaciens WY122. This strain consumed maltose after a long lag phase, in contrast to the phenotypic profile described for the species. According to the STA1+ genotype, S. cerevisiae partially consumed dextrin. Among the volatile organic compounds (VOCs) produced by S. cerevisiae and the S. cerevisiae × S. uvarum hybrid, phenylethyl alcohol, which has a fruit-like aroma, was the most prevalent. In conclusion, the strains characterized here have relevant brewing properties and are exploitable as indigenous craft beer starters.

Variability in the levels of fungicide residues in final beer as they are influenced by various sequences of agrochemicals used for treatment on hops

The fate of during brewing of pesticides (organic compounds and copper) from hops was determined to reveal linkages between various pesticide sequences applied in hop yards and the level of pesticides in beer. For this purpose, laboratory-scale brewing trials were carried out with conventional hops from four localities in which pest control spray programs varied. Pesticide residue analysis in samples of hopped wort, young beer, and beer was carried out by liquid chromatography in tandem with mass spectrometry (LC-MS/MS). Cu concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). The transfer rates (%) of individual pesticides were calculated to demonstrate their ability to be transferred from hops to the brewed solutions. The pesticides exhibited different transfer rates correlating well with their log p values; however, the obtained transfer data were not related to their concentration in hops. The average transfer rates calculated for ametoctradin (15% ± 5%), mandipropamid (38% ± 4%), boscalid (48% ± 5%), and azoxystrobin (47% ± 2%) increased in good correlation with their descending log P values. On the contrary, the transfer rates of copper residues were related to residual concentrations of copper in hops and exhibited logarithmic dependency. The carryover of the sum of all pesticides in the four samples ranged from 36% to 49%, averaging 42% ± 6%. The data showed no substantial influence of various pesticide spray sequences on the percentages of overall pesticide residues carried over into beer.

Effects of Wheat Malt-Derived Endo-Β-1, 4-Xylanase Supplementation on The Quality of Wheat Beer

Endo-β-1, 4-xylanase (EC 3.2.1.8) is a key enzyme in the degradation of Arabinoxylan (AX). AX and its degradation products are the key substances that affect the viscosity, turbidity, filtration speed, alcohol, foam performance, and health care function of wheat beer. A wheat malt-derived endo-β-1, 4-xylanase was isolated and purified by our group in the previous stage. The aim of this study was to investigate the effects of the wheat malt-derived endo-β-1, 4-xylanase addition on the quality and composition of AX in hopped wort and wheat beer. The results showed that the content and the average degree of polymerization (avDP) of water-soluble arabinoxylan (WEAX) in hopped wort and wheat beer decreased with the increase of the addition level of the wheat malt-derived endo-β-1,4-xylanase. When the addition of wheat malt-derived endo-β-1,4-xylanase was 2.5 times of the activity of endo-β-1,4-xylanase in raw malt, the degradation rate of WEAX in hopped wort was the maximum (33.71%), and the avDP of WEAX was the minimum (29.74) at the addition level of the endo-β-1,4-xylanase was 2 times. The viscosity and turbidity of hopped wort and wheat beer decreased continuously with the increase of the addition level of the endo-β-1,4-xylanase, while the foam stability of wheat beer increased continuously. Wheat malt-derived endo-β-1,4-xylanase could decrease the content of 1320-6200 Da polysaccharide in wheat beer, but increase the content of<1320 Da polysaccharide.

Sour Beer with Lacticaseibacillus paracasei subsp. paracasei F19: Feasibility and Influence of Supplementation with Spondias mombin L. Juice and/or By-Product.

This study aimed to evaluate the probiotic strain Lacticaseibacillus (L.) paracasei subsp. paracasei F19 (F19) with the yeast Saccharomyces cerevisiae US-05 (US-05), using Spondias mombin L. ('taperebá' or 'cajá') juice and by-product, in four sour-type beer formulations: control, with bagasse, juice, and juice and bagasse. The viability of F19 was evaluated by pour-plating and PMA-qPCR. Fermentability, in addition to physicochemical and sensory parameters, and aroma and flavor, were evaluated during brewery by using Headspace Solid-Phase Microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). F19 was successful in fermenting bagasse in a MRS medium (9.28 log CFU/mL in 24 h) but had a low viability in hopped wort, growing better in formulations without bagasse or juice. No difference between formulations was observed regarding sensory acceptability, and the HS-SPME/GC-MS revealed different flavors and aroma compounds. In conclusion, the production of a potential probiotic sour beer with F19 and US-05 is feasible regarding probiotic viability. However, S. mombin, as juice or bagasse, threatened probiotic survival. Different flavors and aroma compounds were detected, whereas no difference between formulations was found regarding sensory acceptability. The moderate alcohol content achieved is important for bacterial survival and for the development of a probiotic beer with health claims.

Practical Application of Empetrum Nigrum Extract in Brewing

The article presents the developed formulation of a new variety of light beer with the dry extract of the Empetrum nigrum added. For this purpose, the authors obtained Empetrum nigrum dry extract, which contains 3.40% phenolic substances, including 0.56 % simple phenols; 1.16 % flavonoids, represented by coumarins, chalcones and aurones; and 79.8 % carbohydrates. A man added dry extract Empetrum nigrum to the hopped wort before fermentation in an amount of 0.5 g/l. At this concentration of the added extract, there is an alcoholic fermentation activation, which is evident as an increase in acidity, color and the number of yeast cells in the wort during fermentation to 7.725·107 CFU/ml. The researchers revealed that the beer, obtained according to the developed recipe, had improved organoleptic properties; the taste and aroma of a drink are notable for the pleasant sweetness and herbaceous shade.

Profiling the Volatile and Non-Volatile Compounds along with the Antioxidant Properties of Malted Barley

In this work, the stability of antioxidant compounds in malting barley seeds before and after the production of the final products is reported. In this reflection, the findings revealed that the process of fermentation had a significant impact on antioxidant activity. In vitro, antioxidant capacities were evaluated using DPPH free radical scavenging assay. The results obtained from the spectrophotometric analysis showed that the lowest inhibition value was observed in the samples that were obtained by the classical fermentation process (ABC) and the samples of non-alcoholic beer obtained by the thermal process (NABT), with free radical inhibition capacity values of 8.50% and 5.50%, respectively. The samples of hopped wort (HW) and malted barley seeds extract (BSE) showed very high antioxidant activity with free radical inhibition capacity of 14% and 12.60%, respectively. The obtained extracts were analyzed by gas chromatography and high-performance liquid chromatography, both combined with mass spectrometry detection (GC–MS, HPLC–MS). GC–MS analysis of the SPME extraction showed the presence of 29 compounds with isopentyl alcohol in major concentration (18.19%) in the alcoholic beer; on the other hand, the HPLC–DAD–ESI/MS analysis of the ethyl acetate extract showed the presence of 13 phenolic compounds. Interestingly, the degradation of 3-Hydroxyphloretin 2′-O-glucoside in the final products of the non-alcoholic beers was found. Finally, the FTIR analysis was also employed in order to detect the type of efficient groups present in the extracts.

Optimal Design Approach Applied to Headspace GC for the Monitoring of Diacetyl Concentration, Spectrophotometric Assessment of Phenolic Compounds and Antioxidant Potential in Different Fermentation Processes of Barley

The present study aimed to validate a control method on the gas chromatography system (GC) based on the experimental design strategy, to examine the changes and correlation between the fermentation process and the quality of alcoholic and non-alcoholic beer product, especially the formation of diacetyl. On the other hand, spectrophotometric methods were applied to the determination of polyphenols content and the potential antioxidant activity of beer during different fermentation processes. with this aim, three modes of barley fermentation were used, specifically classical fermentation, stopped fermentation and thermal process. The results showed that the different fermentation modes had a major impact on diacetyl production. The highest concentration was obtained using stopped fermentation 0.36 mg/L, the lowest concentration value 0.07 mg/L was detected using the thermal process. Monitoring the increase of oxygen concentration between fermentation, filtration, and filling of the final product (32, 107, 130 ppm, respectively) has a significant impact on the concentration of diacetyl. The obtained results of spectrophotometric analysis showed that the total antioxidant activity changed during beer fermentation process and demonstrate that the extend of the antioxidant activity was very much dependent on the total polyphenolic content with a higher value in Hopped wort (13.41%, 65 mg GAE 100 mL−1, 28 mg CE 100 mL−1) for antioxidant potential, total phenolic content, and total flavonoids content, respectively, whereas the lowest values was detected in Non-alcoholic beer using thermal process (7.24%, 35 mg GAE 100 mL−1, 10 mg CE 100 mL−1) for antioxidant potential, total phenolic contents, and total flavonoids contents, respectively. Based on the results achieved, we reveal the impact of the fermentation process on the nutritional value of the final product.

Research of hop polyphenols impact on malt hopped wort aroma formation model experiments

Currently, a lot of research is being done on the flavoring compounds of hops. However, much less attention has been paid to the aroma formation considering the hop polyphenol different groups by various methods at the wort hopping stage. Therefore, the main goal of the research is an impact of hopping conditions on the polyphenolic compounds, when the hop is extracted variously into both wort and water to better understand extraction conditions, mechanisms, and factors as well as aroma formation considering various groups of polyphenols. As shown the hop variety, boiling time, and treatment type affect the hop polyphenols amount extracted into the wort. Aromatics varied upon a hop variety and wort boiling time accompanying a positive softening effect regarding aroma formated from malt wort compounds comparing to hopped aqueous extracts. The research proved the most noticeable pH (7 and above) impact on aroma formation caused by the polyphenol conversion. As also shown the first time, a temperature and acidic pH doubled the rutin amount, as well as the best extraction of the prenylflavanoid isoxanthohumol, was achieved by boiling at an alkaline medium pH. The results obtained indicate that various hydrophilic amino acids containing in the wort can stabilize polyphenols affecting the quality indicators of beer produced from different grain raw materials.

Impact of Successive Exploitation of a Saccharomyces pastorianus Starter Culture on Saccharide Uptake Dynamics from Wort.

SUMMARYResearch backgroundThe production of lager beer includes successive repitchings of a single Saccharomyces pastorianus starter culture. During the beer production process, the yeast is exposed to several stress factors which could affect the fermentation performance. An incomplete fermentation represents a waste of fermentable extract and leads to a beer with higher carbohydrate levels, which could result in a beer with an atypical flavour profile. The aim of the present study is to determine the impact of successive exploitation of a single S. pastorianus starter culture on the wort saccharide uptake dynamics.Experimental approachThe fermentation was monitored during the production of twelve batches of beer, where the starter yeast culture was reused twelve times without any further treatment. The following beer production steps were monitored: wort production, yeast starter culture propagation, primary fermentation, secondary fermentation and the final product. The work was conducted on an industrial scale employing standard process conditions.Results and conclusionsMonitoring of the starter culture viability during successive fermentations indicated no reduction in the viability and vitality of the yeast culture. Monitoring of the fermentable wort saccharide concentrations (glucose, fructose, disaccharides and trisaccharides) revealed a correlation between an improvement in saccharide utilisation and starter culture age. Saccharide uptake efficacy proportionally matched the repitching frequency. Successive exploitation of S. pastorianus starter culture has a positive impact on the dynamics of saccharide utilisation from classical hopped wort and the young beer. Furthermore, the final lager beer contains no residues of fermentable saccharides that could affect the overall quality and flavour profile.Novelty and scientific contributionResults showed the impact of twelve successive wort fermentations on the dynamics of saccharides uptake that gives brewers important information. The added value of the experiment is all the work done on the industrial scale, with control of all processes and usage of exactly the same raw materials. This study contains usable technological data on the behaviour of saccharides during brewing on the industrial scale, which is not yet found in the literature.

Impact of Caustic Soda Solution Temperature on Efficiency of its Cleaning on Solid Sediments After Completed Process of Cleaning in CIP System of Brewing Unit

Abstract The paper presents the results of analysis concerning the impact of temperature on sedimentation in the caustic soda solution that constitute a contamination after the process of cleaning utensils and pipes for hopped wort transport in the brewery. The solution was collected from the production plant after the process of cleaning and subjected to 12-hour sedimentation and changes of the solid particles participation, their size and percentage share in the solution was determined. The study was carried out with the Shadow Sizing method. The results were subjected to statistical analysis and the surface area of the response of the relation between the time and temperature of sedimentation and the number of particles which stay in the solution was calculated. The research results proved that the temperature significantly affects the cleaning degree of solutions by sedimentation and its duration. After sedimentation in solutions, particles with the surface area from 0.001-0.003 mm2 remain. Those particles are not subject to sedimentation and constitute a coloidal suspension in the solution.

Search for compounds contributing to onion-like off-flavor in beer and investigation of the cause of the flavor

Onion-like off-flavor is a highly undesirable property in beer. Although several compounds that impart onion-like odors have been identified, the individual contribution of these compounds to the onion-like off-flavor in beer is not clear. In the present study, we searched for compounds that impart an onion-like odor by gas chromatography (GC)-olfactometry. The analysis of several types of beer revealed that 2-mercapto-3-methyl-1-butanol (2M3MB) and 3-mercapto-3-methyl-1-butanol (3M3MB) were possible causative compounds. Based on the difference threshold values in beer (0.13ng/mL for 2M3MB and 17.5ng/mL for 3M3MB) and the quantification values of these compounds in beer samples, only 2M3MB was considered to contribute to the onion-like off-flavor in beer. A further formation factor analysis of 2M3MB revealed that 2M3MB was formed in hopped wort after fermentation, and that the concentration of 2M3MB increased following the hot aeration treatment of wort. These results suggest that preventing the hot aeration of wort is a key factor for reducing 2M3MB levels in beer. In a previous report, 3-methyl-2-buten-1-ol (3MBol) was speculated to be the precursor of 2M3MB and 3M3MB; however, the results of the present quantification analysis and wort addition tests indicate that 3MBol did not contribute to the formation of 2M3MB in the brewing process and that unknown precursors of 2M3MB originated in wort. Identifying the precursor of 2M3MB may facilitate elucidation of the mechanism of 2M3MB formation.

Storage stability of pasteurized non-filtered beer

The influence of pasteurization on non-filtered beers was investigated during accelerated storage (40°C, 41 days). Two beers were produced from the same hopped wort, which was fermented with two different yeast strains. Half of the bottled beers were tunnel pasteurized resulting in four different beer samples. The pasteurization influenced the volatile profile of both fresh beers, but during storage the differences between the volatile profiles of pasteurized and non-pasteurized beers disappeared. During the storage period, the pasteurized beers gave a lower rate of radical formation, as evaluated by electron spin resonance spectroscopy, indicating a better oxidative stability. The pasteurization had no effect on the levels of the pro-oxidative metals iron and copper. Pasteurization slightly increased the protein content of the beers. SDS–PAGE analysis showed that the two beers had different protein profiles, which changed during storage; however, pasteurization of both beers did not affect their protein profiles. The level of thiols were lowered in one beer and raised in the other beer by pasteurization, but during storage the levels of thiols decreased at the same rate in all of the beers. It was concluded that pasteurization had a positive influence on the oxidative stability of non-filtered beer. Copyright © 2013 The Institute of Brewing & Distilling

Comparison of analytical parameters of beer brewed in two different technological ways at two pub breweries

This publication deals with brewing beer by infusion and decoction technologies of mash production in microbreweries. Samples of two microbrewery beers are compared, namely Richard beer (Brno-Žebětín) produced in a double mash manner appropriate for the Czech brewing type, and beer samples taken at the laboratory microbrewery of Mendel University in Brno (MENDELU), where beer is produced in a simpler and less energy – demanding infusion method. At all the beer samples the basic analytical parameters of real extract, ethanol content, degree of fermentation and the extract of original hopped wort were measured using an automatic beer analyzer. The results coming out of the automatic beer analyzer are compared with the results of the beer samples analysis performed by liquid chromatography, by which the contents of oligosaccharides, maltose, glycerol and ethanol were measured. Both methods provide a number of analytical results for the comparison of decoction and infusion techniques, and analytical characteristics of both the brewing procedures. Emphasis is placed on statistical data processing and comparison of different types of beer and particular brews between each other, both in terms of production technology as well as beer sampling throughout the year.

The impact of different ale brewer’s yeast strains on the proteome of immature beer

BackgroundIt is well known that brewer’s yeast affects the taste and aroma of beer. However, the influence of brewer’s yeast on the protein composition of beer is currently unknown. In this study, changes of the proteome of immature beer, i.e. beer that has not been matured after fermentation, by ale brewer’s yeast strains with different abilities to degrade fermentable sugars were investigated.ResultsBeers were fermented from standard hopped wort (13° Plato) using two ale brewer’s yeast (Saccharomyces cerevisiae) strains with different attenuation degrees. Both immature beers had the same alcohol and protein concentrations. Immature beer and unfermented wort proteins were analysed by 2-DE and compared in order to determine protein changes arising from fermentation. Distinct protein spots in the beer and wort proteomes were identified using Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and MS/MS and revealed common beer proteins, such as lipid transfer proteins (LTP1 and LTP2), protein Z and amylase-protease inhibitors. During fermentation, two protein spots, corresponding to LTP2, disappeared, while three protein spots were exclusively found in beer. These three proteins, all derived from yeast, were identified as cell wall associated proteins, that is Exg1 (an exo-β-1,3-glucanase), Bgl2 (an endo-β-1,2-glucanase), and Uth1 (a cell wall biogenesis protein).ConclusionYeast strain dependent changes in the immature beer proteome were identified, i.e. Bgl2 was present in beer brewed with KVL011, while lacking in WLP001 beer.

Control of antioxidant beer activity by the mashing process

Beer is considered to be a good source of antioxidants. The composition and the quantity of the antioxidant compounds depend not only on the qualities of the raw materials, but also on the technology processes. Barley and malt represent the main source of antioxidant compounds in beer and the contribution of the hop antioxidants is lower. The influence of the mashing process on the antioxidant activity and polyphenol concentration is crucial. The antioxidant state of the sweet wort and the hopped wort are dependent on the technology processes and the raw materials used. The spontaneous sorption of polyphenols onto wort dregs and the polymerization of catechin and epicatechin lead to decreasing concentrations of individual polyphenols in the final beer. Two methods, based on electron spin resonance were used to determine antioxidant activity. These were the DPPH (2,2-diphenyl-1-picryl-hydrazyl) assay and the ‘lag time’ assay using free radical spin-trapping agent PBN (N-tert-butyl-α-phenylnitrone). HPLC with CoulArray detection was used to measure the concentration of the individual polyphenols. This study focused on the antioxidant compounds and on the correlation of their concentrations with the values of total antioxidant activity depending on the mashing process. A good correlation was found between the decline in the concentrations of DPPH (expressed as ARA2) and concentrations of catechin and epicatechin (in sweet wort samples R2 = 0.970, R2 = 0.961, respectively, and in hopped wort samples R2 = 0.949, R2 = 0.956 respectively). Copyright © 2012 The Institute of Brewing & Distilling

Brewing trials with spring and winter barley varieties

The effects of a set of barley varieties on the brewing process and quality of beer production intermediaries were studied in trial brews (40 l) prepared using the two-mash decoction process. The varieties included in the trial were selected based on the starch granule size distribution determined previously. A significant effect of the varieties on the saccharification time of both mashes was determined. The highest saccharification rate in brews was achieved with the variety Jersey; the saccharification time of the 1<sup>st</sup> and 2<sup>nd</sup> mash with the variety Tiffany was markedly longer. The varieties with a greater fraction of large starch granules (Tiffany and Luxor) exhibited a higher haze with sweet wort as well as hopped wort compared to the varieties with a low fraction of large starch granules (Jersey and Tolar). The effect on the lautering time was not demonstrated. Pronounced varietal differences were determined in the extract balance of the brewing process. The varieties Tiffany andLuxor exhibited significantly lower extract yields. The malts from these varieties had lower laboratory extracts and higher extract losses in spent grains. The effect of the variety on the sacharide composition in hopped wort was confirmed. The proportion of fermentable saccharides in hopped wort extract rose from the variety Tiffany (66.9%) to the varietyJersey (83.6%). A significant difference in the final attenuation was also determined (76% in beers prepared from the varieties Tiffany andLuxor compared to 81.5% from theJersey variety).  

The growth and survival of food-borne pathogens in sweet and fermenting brewers' wort

The aim of this study was to investigate the factors affecting the survival and growth of four food-borne pathogens ( Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus) in sweet and fermenting brewery wort. The Gram-negative pathogens ( E. coli and Salm. Typhimurium) were capable of growth during the initial stages of fermentation in hopped wort, although they were quickly inactivated when added during the later stages of fermentation. When the wort was left unpitched, the two Gram-negative pathogens grew unabated. Pathogen growth and survival was enhanced as the pH was increased, and as both the ethanol and original gravity were decreased. Although having no effect on the Gram-negative pathogens, low levels of hop iso-α-acids were sufficient to inhibit L. monocytogenes, and a synergistic antimicrobial effect between iso-α-acids and pH was observed. S. aureus failed to initiate growth in all of the test worts. There appears to be no reason for concern of the safety of a “typical” wort during fermentation, however due attention should be paid when wort is stored or antimicrobial hurdles are lowered, for example in the production of reduced and alcohol-free beer, and in unpasteurised products.

The relationship between polypeptides and foaming during fermentation

The foam level during fermentations of hopped and unhopped wort and with fresh yeast and successive generations of yeast was examined. Simultaneously the total and hydrophobic polypeptide contents in worts, fermented worts and their concomitant foams were checked. It was shown that the total and hydrophobic polypeptide contents of the foam fraction and the foam level during fermentation were dependent on the generation number of yeast. The early generations of yeast (generations 1 and 2) promoted the formation of the largest amount of foam. It was also observed that a higher volume of foam occurred during fermentation of hopped wort in respect to unhopped one despite a higher concentration of polypeptides in unhopped wort. It could be a consequence of a higher foaming potential of polypeptides in hopped wort. The findings of the work may result in the limitation of foaming in the fermenters and consequently the increase of the brewery productivity without using additives and compromising the quality of the final product.