Application of a hop by‐product in brewing: reduction in the level of haze‐active prolamines and improved antioxidant properties of the beer

After supercritical CO₂ extraction of hops or formation of lupulin‐enriched pellets (type 45), polyphenol‐rich by‐products remain. These have some industrial and agricultural applications (preparation of polyphenol extracts and in the production of low‐bitterness beers). In this work, both materials were used in pilot‐scale brewing experiments for the production of beer enriched with polyphenols. Samples of beer made from these residues underwent analyses for haze‐active prolamines, total polyphenols, phenolic monomers, antioxidant capacity, bitterness and colour. An almost identical decrease in the content (from hopped wort to final beer) of the prolamines of approximately 30% was detected in standard beer as well as in the beer prepared from the hop residue (HR 1) after supercritical CO₂ extraction. In contrast, the level of prolamines was reduced by more than 50% in the beer following addition of the hop residue (HR 2) after production of lupulin enriched pellets. Both hop materials contributed to an increase in the antioxidant capacity of the final beer by 21.5 and 11.9%, respectively. Another part of this work was aimed at the investigation of colour and bitterness changes in beers made ??using hop by‐products. Addition of the material HR 2 into the wort caused an increase in colour and in bitterness of the matured beer by 20 and 11% rel., respectively. Copyright © 2014 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 Instability of Pale Lager Beers: Determination of Analytical Markers in Relation to Sensory Ageing

Flavour changes of six Belgian pale lager beers were studied in order to estimate the importance of different parameters and reactions in relation to the ageing process. An attempt was made to link analytical data with sensory evaluation using multivariate statistical analysis. Partial least squares regression techniques (PLSR) were employed on the analytical and sensory data. As apparent from the PLSR model, significant indicators of lager beer ageing are aldehyde markers (especially total aldehydes, furfural, hexanal, 2‐methylpropanal, 2‐methylbutanal, and 3‐methylbutanal), cold and permanent haze, and beer colour. Conversely, compounds or parameters that load negatively in the PLSR model for beer ageing are trans‐isohumulones, cis‐isohumulones, total bitterness, the T/C‐ratio, polyphenolic markers (especially proanthocyanidins), the flavanoid content, and, to a lesser extent, the TB‐index and reducing power (TRAP). The integrated analytical‐sensorial methodology is proposed as a useful tool for evaluation of the flavour instability of pale lager beers.     

Enrichment of xanthohumol in the brewing process

Xanthohumol (XN), a component of hops, is lost in significant quantities in the conventional brewing process. In commercial beers less than 0.2 mg XN/L are found. In order to increase the yield of XN in the brewing process, the parameters of XN recovery were studied. During wort boiling, XN is largely isomerised to isoxanthohumol. Further losses are owing to the precipitation and absorption of XN to yeast cells and haze particles and by filtration. The use of XN-enriched hop products combined with a late hop dosage during wort boiling proved to be effective in increasing the XN content in beer. The yield was further raised by a low-pitching rate and the abnegation of beer stabilisation. The use of dark malts had a positive effect on the XN recovery. Investigations of roasted malt extracts revealed several high-molecular substances that are able to form complexes with XN. These complexes proved to be stable in the brewing process. Depending on the addition of roasted malt or special XN-enriched roasted malt extracts, dark beers with more than 10 mg XN/L were achieved. Results obtained led to a brewing technology that produced on an industrial scale pale wheat beer with more than 1 mg XN/L.     

Personality traits and bitterness perception influence the liking and intake of pale ale style beers

Bitterness is classically considered undesirable in foods and beverages. Yet, widespread commercial success of beers (like Bitters in the UK or IPAs in the US) indicate bitterness is desirable for some consumers. Here, we tested whether personality traits influence beer liking and intake. Under laboratory conditions, beer consumers (n = 109) rated liking and intensity of 2 pale ales and a lager, and intensity of two bitter solutions (quinine, Tetralone®). Participants also completed intake and personality questionnaires (Sensation Seeking, Sensitivity to Punishment and Reward, and Food Involvement). A liking ratio for each beer was calculated from each participant’s liking for that specific beer and their total liking for all beers. Participants were classified as weekly, monthly, or yearly pale ale consumers using intake data. Using intensity ratings, personality measures, and other parameters, hierarchical linear regression was used to predict liking ratios, and logistic regression was used to predict beer intake frequency. A significant interaction between Sensation Seeking and quinine bitterness (p = 0.03) was found for the liking ratio of a pale ale. The interaction revealed liking of the pale ale increased with Sensation Seeking but only if quinine bitterness was also high. Intake models showed increased odds of frequent pale ale intake with greater quinine bitterness and lower liking for lager beer. These data suggest liking and intake of pale ales is positively related to Sensation Seeking and bitter taste perception. Contrary to findings in other bitter foods and beverages, the high bitterness found in pale ales may be desirable for some consumers.     

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.     

Antioxidant properties of commercial alcoholic and nonalcoholic beverages

Recent interest in food phenolics has increased greatly, because of their antioxidant and free radical scavenging abilities. Popular beverages in the world include tea, coffee, cocoa, beer, wine and fruit/vegetable juices. All of these beverages contain phenolic compounds. In present study total polyphenol content and in vitro antioxidant properties were investigated in 16 red wines, 5 white wines, 5 lager beers, 3 dark beers, 17 fruit juices and 5 vegetable juices. High polyphenol content was measured in red wines (1720 +/- 546 mg x L(-1)) and in some fruit juices such as elderberry and prunes (5,680 and 1,807 mg x L(-1), respectively). The concentration of polyphenols was between 159 and 5,680 mg x L(-1) in fruit juices and between 255 and 696 mg x L(-1) in vegetable ones, while low level of phenolics was observed in dark and lager beers and white wines (473, 376 and 392 mg x L(-1), respectively). All samples exhibited significant antioxidant properties such as hydrogen-donating ability, reducing power, chelating ability and total antioxidant status (TAS) value. These antioxidant properties strongly correlated with the total polyphenol content of the beverages.     

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.     

Modification of perceived beer bitterness intensity,character and temporal profile by hop aroma extract

The effect of hop aroma on perceived bitterness intensity, character and temporal profile of beer was investigated. A hop aroma extract was added at 3 levels (0, 245, 490 mg/L) to beers at low, medium and high bitterness. Beers were evaluated for perceived bitterness intensity, harshness, roundedness and linger by a trained panel using a rank-rating technique at each bitterness level, with and without nose clips. The use of nose clips enabled the olfactory aspect to be decoupled from taste and mouthfeel aspects of bitterness perception. Results showed significant modification of perceived bitterness in beer by hop aroma depending on the inherent level of bitterness. These modifications were mainly driven by olfaction – in an example of taste-aroma interactions, as well as certain tactile sensations elicited by the hop aroma extract in the oral cavity. At low bitterness, beers with hop aroma added were perceived as more bitter, and of ‘rounded’ bitterness character relative to those without hop aroma. When judges used nose clips, this effect was completely eliminated but the sample was perceived to have a ‘harsh’ bitterness character. Conversely, at high bitterness, even when nose clips were used, judges still perceived beers containing hop aroma to be more bitter. These increases in bitterness perception with nose clips indicates the stimulating of other receptors, e.g. trigeminal receptors by hop aroma extract, which in tandem with the high bitterness, cause perceptual interactions enhancing bitterness intensity and also affecting bitterness character. Bitterness character attributes such as ‘round’ and ‘harsh’ were found to significantly depend on bitterness and aroma levels, with the second level of aroma addition (245 mg/L) giving a ‘rounded’ bitterness in low bitterness beers but ‘harsh’ bitterness in high bitterness beers. The impact of aroma on temporal bitterness was also confirmed with time-intensity measurements, and found to be mostly significant at the highest level of hop aroma addition (490 mg/L) in low bitterness beers. These findings represent a significant step forward in terms of understanding bitterness flavour perception and the wider impact of hop compounds on sensory perception.     

EFFECTS OF PRODUCTS FROM SEEDLESS AND SEEDED HOPS ON BEER QUALITY

Comparative semi-industrial brewing trials with standard Continental lager beers have been carried out in Switzerland using hop pellets and hop extracts made from seeded and seedless hops. It has been demonstrated that the products from seeded hops containing 8% and 9% of seeds have no adverse effect on beer quality and that the flavour of all the beers was acceptable.     

Immunochemical determination of gluten in malts and beers.

The gluten content in different varieties of barley and malts, and in different types of beers, was determined by a 'sandwich' enzyme immunoassay (RIDASCREEN Gliadin kit). The gluten levels in barley wheat, rye and spelt malts ranged 18.8-45.0, 44.0-68.0, 41.6 and 21.2 g kg-1, respectively. When various types of beer were compared, the gluten concentration increased as follows: alcohol-free beer (<3.0), lager beers (<3.0-8.7 mg l-1), stouts (9.0-15.2 mg l-1) and wheat beers (10.6-41.2 mg l-1). When 10 Czech lager beers were analysed, using both sandwich and competitive ELISA, the results showed that the latter method provided values several times higher than the former. Gluten balance was carried out during the brewing process, starting from the raw materials and terminating at the final beer. Gluten levels decreased due to precipitation during the mashing process, primary and secondary fermentation and, lastly, as a result of adsorption during beer stabilization. The gluten content in beer is, thus, approximately three orders of magnitude lower than in the raw malt.     

The Impact of a Xanthohumol‐Enriched Hop Product on the Behavior of Xanthohumol and Isoxanthohumol in Pale and Dark Beers: A Pilot Scale Approach

Based on the health‐promoting properties of xanthohumol (XN), the production of an enriched beer in this substance would be of interest to the brewing industry, from the perspective of pointing out the benefits that beer could bring consumer health. For that purpose, in this work efforts were applied to produce a beer enriched in XN. Also investigated was the influence of a XN‐enriched hop product on the content of XN and isoxanthohumol (IXN) in pale and dark beers. It was verified that XN was largely converted into IXN during wort boiling. However, the use of dark malts revealed a positive effect on the thermal isomerisation of XN. These results are indicative of the isomerisation‐inhibiting effect of the stout production process, which resulted in high levels of XN in the beer. Further losses of XN were due to incomplete extraction from the hops into the wort, adsorption to insoluble malt proteins and adsorption to yeast cells during fermentation. It was possible to produce a dark beer enriched in XN (3.5 mg/L) by using coloured malt (caramel malt, roasted malt and roasted malt extract) and a special XN hop extract combined with late hop usage during wort boiling.     

PHENOLIC ACIDS IN BEERS AND WORTS

The total contents of phenolic acids measured by high-performance liquid-chromatography were 5–8 mg/litre in beers brewed in Ireland whereas 16–40 mg/litre were present in four other beers. In all beers the predominant phenolic acids were vanillic, p-coumaric and ferulic acids. Free phenolic acids were extracted from Emma barley grains and malt in very small amounts (15–28 mg/kg) but larger quantities (191 mg/kg) were released on mashing the malt. Little change occurred in the contents of phenolic acids on processing a lager wort through to the finished beer. Treatment with excess Polyclar AT removed astringent flavour and phenolic acids from an experimental ale but this flavour loss could not be accounted for by the adsorption of phenolic acids. The flavour threshold for a nine-component phenolic acid mixture in lager was between 50 mg/litre and 100 mg/litre.     

Aging characteristics of different beer types

Eight commercial beers (3 lager beers, 2 dark ales and 3 high-alcoholic ales) were aged for one year under normal storage conditions, and the changes with time of flavour profile and the concentration of 15 volatile compounds were monitored. The compounds were chosen as markers to evaluate the importance of different reactions in the aging process of each beer type. The development of typical aging flavours during beer storage could be linked to the Maillard reaction, the formation of linear aldehydes, ester formation, ester degradation, acetal formation, etherification and the degradation of hop bitter compounds. A difference in the nature of aging flavours between lager and specialty beers was found and seemed to be mainly the result of an increased Maillard reaction in specialty beers. Based on the results, some practical strategies are proposed to improve the flavour stability, depending on the beer type.     

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.     

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     

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.     

Use of High Hydrostatic Pressure to Increase the Content of Xanthohumol in Beer Wort

During beer production, xanthohumol (XN) extracted from hop through wort boiling is largely converted into its isomeric flavanone, isoxanthohumol (IXN), due to the thermal treatment. XN has a great biological interest as a functional compound (being anti-carciogenic, antioxidant, anti-inflammatory, and anti-infective) and its loss leads to beers with very small amounts of XN and reduced functional properties. In this work, we studied the use of high-pressure treatments (HP; 100, 200, 250, 300, 400 and 500 MPa for 5 min and 250 and 400 MPa for 15 min), applied to previously boiled worts with a second hop dosage, as an extractive procedure, to produce XN-enriched beer worts. The results indicated that beer worts processed by HP showed higher levels of XN. The best results were obtained for 250 MPa, 5 min, resulting in an increase of 4-fold in XN, compared with beer worts produced only by boiling, and 2-fold compared with a method mimicking a recently proposed methodology also intended to improve XN in wort (called XAN method). Combinations of lower pressures with short pressurisation periods proved to be more efficient to increase the amount of XN in the wort. Moreover, HP-processed worts showed lower levels of IXN compared with samples produced by the mimicked XAN method. Physical–chemical characteristics of worts (pH, colour, bitterness and original extract) produced by HP, were similar to those produced only by boiling. These results clearly indicate the potential of using HP treatments to increase the XN content in beer wort, together with less isomerisation to IXN, and open promising possibilities to produce beers with higher amounts of XN, with potentially enhanced functional properties and health promoting properties.     

Dark vs. light drinks: The influence of visual appearance on the consumer’s experience of beer

We report evidence concerning how the visual appearance of a drink (dark vs. light pale/amber beer) can influence the consumer’s tasting experience. Two experiments were designed to study the effect of visual appearance on people’s hedonic and sensory judgments of beer. Importantly, the beers were indistinguishable in terms of their flavor when tasted in the absence of visual cues.Participants rated the same beer (pale or dark, depending in which group they were assigned) under blind conditions as having more body than when tasted under sighted condition (regardless of whether it was pale or dark; see Experiment 1).When the participants evaluated the expectations and tasting experience of the two different beers under sighted conditions (pale vs. dark), after tasting, those who preferred pale beers, rated the darker beer as tasting sweeter than those who usually prefer other types of beers, such as dark ones (see Experiment 2). Prior tasting, when asked which beer they thought was the most expensive, the majority of the participants chose the darker beer. Furthermore, after tasting both beers, participants reported being willing to pay up to 6% more on average for the darker beer as compared to the pale one.