A preliminary study about the influence of high hydrostatic pressure processing on the physicochemical and sensorial properties of a cloudy wheat beer

High hydrostatic pressure (HHP) (400 MPa/15 min, 500 MPa/10 min, 600 MPa/5 min at 20 °C) and heat (60 °C/15 min) processing of wheat beers were evaluated by examining their impacts on microorganisms, colloidal haze, flavour, foam stability and shelf‐life prediction during 84 days of storage at 20 °C. The results obtained showed that the microbiological stability of HHP beers was comparable with heat‐treated samples, and the development of both aerobic bacteria and lactic acid bacteria was inhibited for 84 days of storage. The main parameters of the wheat beer, such as ethanol content, original extract, pH, bitterness and viscosity, were scarcely affected by either treatment compared with the control samples; however, heat pasteurization increased the colour value. Heat‐pasteurized beer resulted in an increase in the phenethyl alcohol concentration and a decrease in isoamyl acetate and ethyl acetate levels compared with the HHP samples. These treatments did not affect the amount of 4‐vinylguaiacol and 4‐vinylphenol in the beer. The HHP‐treated beers had higher colloidal haze and foam stability values than the heat‐pasteurized beers. Dynamic light scattering analysis showed that HHP treatments at 500 MPa/10 min resulted in smaller and more uniform particle sizes, which had a positive effect on beer haze stability during storage. Copyright © 2016 The Institute of Brewing & Distilling     

The Possibilities of Particle Analysis Demonstrated by the Measurement of the Colloidal Stability of Filtered Beer

Long‐term stability is one of the most important quality criteria of beer. Three groups of measuring methods are available for its determination: real time tests, predictive tests and indicative tests. One of the most common methods is the predictive forcing test, which is a time‐consuming method for accelerating beer ageing, e.g., at 0°C and 60°C. Two ways exist to perform this test: (1) follow‐up of haze development and determination of the lag phase or (2) the measurement of haze values after several days. The first option was evaluated by performing a long‐term Forcing test over a period of 4 months by analyzing a bottom‐fermented beer. It was shown that the haze curve followed a typical course with a lag phase, an increase phase and a stationary phase. Significant differences between the measurement after the cooling and the warm period were shown. In search of quicker methods and more accurate predictive indicators, the charge titration method was developed as an alternative to determine the particle charge of filtered beers, whereupon the relationship was elucidated between the increase in hazing and decrease of potential along with the advanced aging of beer. The results showed that with increased particle size due to agglomeration, the total charge decreased. In this array of trials, two differently stabilized beers were examined. Although both beers showed different haze values in the beginning (0.32 EBC and 1.30 EBC), the less stabilized beer had only 10 warm days and in contrast the beer with the good stabilization had over 20 warm days. With the help of the total charge, predictions were possible regarding the long‐term stability of the beer.     

A preliminary study of the quality attributes of a cloudy wheat beer treated by flash pasteurization

Flash pasteurization (37 and 100 pasteurization units, PU) and conventional tunnel pasteurization (15 PU) processing of wheat beers were evaluated by examining their impacts on microorganisms, colour, colloidal haze and flavour stability during 84 days of storage at 20°C. The results revealed that the microbiological stability of 37 and 100 PU flash‐pasteurized beers was comparable with that of the 15 PU sample, and the development of both yeast and lactic acid bacteria was inhibited for 84 days of storage. The conventional tunnel‐pasteurized wheat beer resulted in a higher thermal load relative to the flash‐pasteurized samples based on the results of oxidative stability. These three pasteurized beers showed a similar decrease in haze intensity throughout the storage period. Meanwhile, flash‐pasteurized beers had better colour and colloidal haze stability than the tunnel‐pasteurized beer. It was also found by dynamic light scattering analysis that the temperature in the flash pasteurizer has the desired effect on the protein denaturation and particle size distribution. Therefore, flash pasteurization is a promising method to increase the shelf‐life of wheat beers instead of conventional tunnel pasteurization. Copyright © 2017 The Institute of Brewing & Distilling     

FLAVOUR AND HAZE STABILITY DIFFERENCES DUE TO HOP TANNINS IN ALL-MALT PILSNER BEERS BREWED WITH PROANTHOCYANIDIN-FREE MALT

All-malt Pilsner beers were brewed with proanthocyanidin-free malt (ant 13 × 13 × Rupal). Hopping was with n-hexane tannin-free hop extract with or without n-hexane extracted hop residue or with whole leaf hops. The different beers were analysed chemically and presented to an expert panel to detect possible preferences and differences in bitterness and astringency. The impact of hop proantho-cyanidins on haze formation is comparable to that of malt proanthocyanidins. No differences between the beers were found in triangular tests. Statistical analysis of the paired comparison tests showed that hop proanthocyanidins do not contribute to the bitterness of beer since beer brewed with tannin-free hop extract is slightly more bitter than beer brewed with whole leaf hops. No differences in astringency were noted between beers brewed with or without hop proanthocyanidins and it was found that the panel expressed a very slight preference for beer brewed with n-hexane hop extract over beer brewed with both n-hexane hop extract and extracted hop residue.     

Analysis of total polyphenols,bitterness and haze in pale and dark lager beers produced under different mashing and boiling conditions

Malting and brewing processes should be performed under process conditions in a way that minimizes beer bitterness, maximizes polyphenol content and reduces the amount of raw materials ending up in solution in the form of hazes, particles and precipitates. This work examined the influence of different mashing temperature conditions and boiling procedures on the total polyphenol content, bitterness and haze of pale and dark lager beers produced on an industrial scale. Two hop types (hop pellets and/or hop extract) and different hop varieties (Hallertau Magnum, Styrian Goldings, Saaz, Aurora and Sladek) were utilized with varying times of hop addition into the wort. Measurements of total polyphenols, colour, bitterness, alcohol content, CO₂ and pH were carried out on the beer samples. Results showed that pale lager beers had a lower total polyphenol concentration (110–179 mg/L) than dark beers (230–260 mg/L). Using hop extracts instead of hop pellets led to a lower total polyphenol concentration and to less beer foam creation. The change in the proteolytic temperature during mashing only had an influence on the total polyphenol content in the pale lager beer hopped with the pellets. Conducting proteolysis over a 20 min period led to a haze increase in all of the beers produced. In the dark beer, the haze was substantial after just 10 min at 52°C. Copyright © 2015 The Institute of Brewing & Distilling     

The Role of Malt and Hop Polyphenols in Beer Quality,Flavour and Haze Stability

Pilot‐scale brewing trials of a 12°P pale lager beer were conducted to look at the effect of a modified dose of hop and malt polyphenols on haze, flavour quality, and stability. Results confirmed that malt polyphenols, and particularly hop polyphenols, in the course of wort boiling, improved reducing activity values and the carbonyl content in fresh and stored beers. Hop polyphenols significantly increased reducing activity and decreased the formation of carbonyls (TBA value) in fresh and stored beer. Reduced content of malt polyphenols, combined with the use of hop CO₂ extract, caused an increase in the TBA value in beer. PVPP stabilized beers tended to be lower in reducing activity. Both malt and hop polyphenols affected the intensity of “harsh taste” in fresh beers and a significant influence from PVPP stabilization of beer was not observed. The staling degree of forced‐aged beers depended on the polyphenol content in the brewhouse. Both hop and malt polyphenols had a positive impact on flavour stability. PVPP treatment of beer had a positive effect on the flavour stability of heat‐aged beers. Polyphenols, especially hop polyphenols, slowed down flavour deterioration during the nine month storage period, but the primary effect was seen during the first four months of storage. Storage trials did not show any unambiguous effects for PVPP stabilization on beer flavour stability. Results confirmed the negative impact of malt and hop polyphenols on haze stability, and PVPP stabilization minimized differences in shelf life prediction values between beers prepared with the modified dose of polyphenols.     

FLAVOUR AND HAZE STABILITY DIFFERENCES DUE TO HOP AND MALT TANNINS IN ALL-MALT PILSNER BEERS BREWED WITH PROANTHOCYANIDIN-FREE AND WITH REGULAR MALT

All-malt Pilsner beers were brewed with and without hop and malt proanthocyanidins by using regular malt and whole leaf hops as well as proanthocyanidin-free malt and n-hexane tannin-free hop extract. The different beers were analysed chemically and presented to an expert panel to detect possible differences in bitterness and astringency. The impact of proanthocyanidins on the formation of haze was demonstrated clearly. No differences between the beers were found in triangular tests although their levels of total polyphenolics and anthocyanogens differed by about 225 and 85 mg/litre. Statistical analysis of the paired comparison tests showed only very slight differences between beers with or without hop and malt proanthocyanidins. Thus, proanthocyanidin-free beer was considered less than slightly more bitter and astringent than regular beer and there was a very slight preference for the latter.     

CALIBRATION AND EVALUATION OF HAZE METERS

A survey of haze meters that are currently available has been carried out to find out whether an instrument(s) can be recommended for use by the brewing industry. There is a marked difference between values measured by instruments reading at 13° and 90° scatter. There are very minor differences in the haze values obtained using the various 90° instruments. Overall the Hach meter is recommended as a replacement for the Radiometer. Suspensions of styrene divinylbenzene beads were judged to be suitable as an alternative to Formazin for standardising haze meters.     

Wheat Variety and Barley Malt Properties: Influence on Haze Intensity and Foam Stability of Wheat Beer

Laboratory wheat beers were brewed with different wheat varieties of different protein content (8.7–14.4%) and with five different barley malts, varying in degree of modification (soluble protein: 3.9–6.9%). In a first series of experiments, it was investigated whether wheat positively influences the foam stability, a major characteristic of wheat beers. NIBEM and Rudin (CO₂) foam analyses revealed that the effect of wheat on foam stability depended on the barley malt used for brewing. When using malt with high foaming potential, wheat exerts a negative influence. However, wheat added to over‐modified malt with less foam promoting factors, ameliorates beer foaming characteristics proving that wheat contains foam active compounds. In addition, Rudin (N₂) values suggested that wheat positively influences foam stability by decreasing liquid drainage, probably caused by a higher beer viscosity and/or a finer foam bubble size distribution. Furthermore, the haze in wheat beers, which is another important quality characteristic of these beers, was investigated. Permanent haze readings of the 40% wheat beers were lower than 1.5 EBC haze units. For 20% wheat beers, an inverse relation between the permanent haze (9.4–19.3 EBC haze units) and the protein content of the wheat was established. The barley malt used for brewing also influenced permanent haze readings. A positive correlation between the modification degree of the malt and the permanent haze intensity was found. It was concluded that the choice of raw materials for wheat beer brewing considerably influences the visual properties of the beer.     

LOW PROANTHOCYANIDIN MALTS FOR PRODUCTION OF CHILLED AND FILTERED OR FINED BEER

Malts which conform to most commercial specifications can be prepared from Galant barley, which is low in anthocyanogens. However, the malting performance of this variety is only medium and considerable care is required during kilning in order to avoid excessive colour development. Beers brewed from Galant malt have greatly improved chill haze stability, although flavour stability is not significantly affected. Fining and filtration studies on rough beer and forcing tests for the development of non-biological haze in finished beer indicate that the use of Galant malt greatly reduces the extent of precipitation of particulate matter during brewing, conditioning and subsequent storage. This can result in considerable savings in the use of finings, and in longer filter runs since levels of addition of body feed can be reduced. It is suggested that the use of low anthocyanogen malts could, with some beers, reduce the necessity for chilling prior to and during filtration.     

THE ESTIMATION AND SIGNIFICANCE OF CATECHIN AND DIMERIC CATECHIN IN BEER

A gas-liquid chromatographic method for the estimation of monomeric and dimeric catechin in beer is described. This method has been used to estimate the concentrations of these compounds in a number of beers, which were found to contain 0·5 to 8·0 ppm of monomeric catechin and up to 22·0 ppm of dimeric catechin. Beers bottled with a high level of air in the headspace can have a long shelf-life providing the level of dimeric polyphenols is low. The shelf-lives of beers which contain high concentrations of dimers are very sensitive to the levels of air in the headspace. At the levels found, monomeric catechin has no significant effect on haze whether or not headspace air is present.     

THE REACTIONS BETWEEN POLYPHENOLS AND ALDEHYDES AND THE INFLUENCE OF ACETALDEHYDE ON HAZE FORMATION IN BEER

The reactions and interactions between proteins and polyphenols are, among other phenomena, responsible for haze formation in beer. The participation of aldehydes in the polymerisation of polyphenols is considered. The formation of phenolic Baeyer-type condensation products containing phenolic residues linked by CH₃CH-bridges through reaction with acetaldehyde is possible at the pH of beer (4.0). These and other reactions with acetaldehyde in beer participate in beer haze formation.     

THE INTRINSIC INFLUENCE OF CATECHINS AND PROCYANIDINS ON BEER HAZE FORMATION

Different concentrations of catechins and procyanidins were added to an all-malt Pilsner beer brewed from proanthocyanidin-free malt (ant 13·13 × Rupal) and tannin-free hop extract in order to evaluate their intrinsic role in beer haze formation, i.e. in the absence of malt and/or hop flavanoids. The molar tanning capacities of flavanoids depend upon their degree of polymerisation. Procyanidin B6 was much more haze active than procyanidin B3. Both immediate haze and formation of haze after 150 days of storage at room temperature was in general linearily related to the added concentration of phenolics.     

The chemical components in malt associated with haze formation in beer

In bright beer, haze formation is a serious quality problem, which reduces beer storage and shelf life. In this study, haze‐active proteins, alcohol chill haze formation ability, α‐amylase activity, the contents of total polyphenol, protein and its fractions and amino acids were analysed using 23 barley accessions to investigate the relationship between the quality components in the malt and the haze character in beer. The results showed that there were largely genotypic variations for all examined traits among the 23 barley accessions. However, there was no significant correlation between the haze character and α‐amylase activity. All haze characteristics were significantly and positively correlated with total protein content, albumin, globulin and the hordein content, as well as the glutamic acid (glutamine), proline and phenylalanine content, and were not correlated with total polyphenols. A model describing the relationship between the chill haze in the beer and the protein content in the malt was developed. Copyright © 2016 The Institute of Brewing & Distilling     

FLAVOUR AND HAZE STABILITY DIFFERENCES IN UNHOPPED AND HOPPED ALL-MALT PILSNER BEERS BREWED WITH PROANTHOCYANIDIN-FREE AND WITH REGULAR MALT

Unhopped and hopped all-malt Pilsner beers were brewed with proanthocyanidin-free malt (ant 13–13×Rupal) and with regular malt (Gatinais). A tannin-free hop extract was used. The beers were analysed chemically and presented both to an expert and an untrained taste panel to detect possible preferences and differences in bitterness and astringency. The colloidal stability of the proanthocyanidin-free beers is superior to that of the regular ones. Paired comparison tests show that at the 3% significance level there is a difference in the appreciation of bitterness of the unhopped beers, the proanthocyanidin-free beer being the more bitter. The panelists do not detect differences in astringency and they have no preference for either beer. In the case of the hopped beers no bitterness, astringency or preference differences are found in paired comparison tests. Finally, no differences between hopped and unhopped proanthocyanidin-free and regular beers were found at the 5% significance level when using both an expert and an untrained panel in triangular experiments.     

Hop proanthocyanidins for the fining of beer

Fining agents are used in the clarification of beers; they help to reduce the time required to sediment suspended yeast cells and ensure the clarity and colloidal stability of beer. Following an adventitious observation during dry‐hopping experiments, we identified a fining activity associated with Saaz hops. Extracts of hop cones were subsequently shown to have the capacity to flocculate yeast and result in their sedimentation. This activity has since been identified in extracts of many different hop varieties and, significantly in spent hops, the co‐product resulting from commercial extraction of hops with either CO₂ or ethanol. Here we illustrate the activity of the novel finings extracted from spent hops following CO₂ extraction of Galena hops. The sediments formed on fining were compact, relative to those obtained when commercial isinglass was used to fine the same beers. The hop extracts were also effective in reducing 90° haze in beers under conditions designed to mimic both cask ale (12 °C) and lager (4 °C) type applications. The compounds responsible for the fining activity appear to be large (30–100 kDa, or more) polyphenols. Analysis of the polyphenols using colourimetric tests indicated the presence of proanthocyanidins. On acidic hydrolysis these generated cyanidin, which would be derived from a polymer composed of catechin and epicatechin subunits. The presence of these materials in spent hops offers the possibility to develop commercial products, with desirable fining properties, from an existing co‐product stream. Furthermore, the finings are derived from a traditional ingredient of the brewing process. Copyright © 2015 The Institute of Brewing & Distilling     

High Hydrostatic Pressure Treatments for Beer Stabilization

ABSTRACT: Crude cloudy beers from a small-scale brewery were treated with high hydrostatic pressure (HHP-600 MPa, 5 min) or heat pasteurized (60 °C, 10 min). The treatments did not affect pH, ethanol, extract, bitterness, or phenolics in comparison with untreated beers; HHP beers retained permanent haze, similar to untreated samples. Heat pasteurized beer resulted in a more rapid increase of the a* (red) and a slower decrease of the b* (yellow) color parameters than in HHP samples. The microbiological stability of HHP beers was comparable with heat-treated beers, and the development of yeast and lactic acid bacteria was inhibited for 49 d of storage.     

EUROPEAN BREWERY CONVENTION: HAZE AND FOAM GROUP. TOWARDS THE CHEMICAL PREDICTION OF SHELF LIFE

Rapid chemical methods are described for assesssing in beer the levels of “oxidizable polyphenols” and “sensitive proteins,” both of which influence non-biological shelf life. The method for oxidizable polyphenols depends on the formation of an insoluble complex with cinchonine sulphate. Freshly processed beers form only a slight haze on the addition of cinchonine sulphate, but the haze produced is greatly increased if the beers are previously oxidized. For beers stabilized by a process involving reduction of the polyphenol content, it is found that the rate of haze formation is then directly related to shelf life and is inversely proportional to it.     

THE RELATIONSHIP BETWEEN HAZE AND THE SIZE OF PARTICLES IN BEER

Haze measurements have been obtained for suspensions of polystyrenelatex particles of known diameter using two light scattering instruments which measure at angles of 90° and 13° respectively. The results agree well with the theory of light scattering and demonstrate the significant effects of particle size and angle of detection upon the instrumental values for haze. This information has been used to correlate the particle size distributions of a number of beers, as measured by Coulter Counter, with the corresponding, measured haze values.     

Effects of high hydrostatic pressure on shelf life of lager beer

Filtered bright lager beer samples were either treated with high hydrostatic pressure (HHP, 350 MPa for 3 and 5 min at 20 °C) or conventional heat pasteurization (60 °C for 15 min). A storage period of 56 days showed that HHP and heat pasteurization had similar results in terms of pH and color (p<0.05). However HHP-treated samples had lower bitterness and protein sensitivity and higher chill haze values than the heat pasteurized samples at the end of the storage period. The microbiological stability of HHP-treated beers was the same as that of heat-treated beers, and the development of both lactic and acetic acid bacteria was inhibited for 56 days of storage. Although more studies should be carried out to investigate the effects of HHP treatment on different types of lagers and ales, our results revealed that HHP could be successfully used to increase the shelf life of beer even at temperatures well below those required for heat pasteurization.