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.     

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.     

Roasting of malt and xanthohumol enrichment in beer

The use of commercial roasted malts increases the content of the hop polyphenol xanthohumol (XN) in beer. This carrier effect is caused by high molecular melanoidins from roasted malt. Three roasting trials with different malts were performed in order to study the development of XN enrichment of wort and beer in laboratory and brewing trials. Different colour measurements, malt and flavour analysis, radical formation and antioxidative activity of selected samples were carried out. Furthermore, sensory tests of beers were conducted. During roasting the XN and isoxanthohumol enrichment in wort and beer rose with the roasting intensity of malt until it reached a maximum. The XN content in wort increased linearly with the colour of wort made from the malt samples. In PVPP-treated worts and in filtered beers, the XN content increased exponentially with the colour. After passing through a maximum, both the colour value and XN content in wort and beer decreased. Interestingly, the colour losses were more intensive than the losses of XN in worts and beers. The development of radical formation and the reducing power was linked during roasting. That means reducing groups of melanoidins are responsible for reducing power and prooxidative properties of malts. These functional groups of melanoidins are involved in the development of XN enrichment properties, because a linear correlation between these parameters was found. In conclusion, the roasting regimes showed potential for the development of special malt for the XN enrichment in beer- or malt-based beverages in late roasting stages. The use of this special malt brings more XN with less coloured malt in beer.     

Impact of Dark Specialty Malts on Extract Composition and Wort Fermentation

Dark specialty malts are important ingredients for the production of several beer styles. These malts not only impart colour, flavour and antioxidative activity to wort and beer, they also affect the course of wort fermentations and the production of flavour‐active yeast metabolites. The application of considerable levels of dark malt was found to lower the attenuation, mainly as a result of lower levels of fermentable sugars and amino acids in dark wort samples. In fact, from the darkest caramel malts and from roasted malts, practically no fermentable material can be hydrolysed by pilsner malt enzymes during mashing. Compared to wort brewed with 50% pilsner malt and 50% dark caramel malt or roasted malt, wort brewed with 100% pilsner malt contained nearly twice as much fermentable sugars and amino acids. Reduced levels of yeast nutrients also lowered the fermentation rate, ranging from 1.7°P/day for the reference pilsner wort of 9 EBC to 1.1°P/day for the darkest wort (890 EBC units), brewed with 50% roasted malt. This additionally indicates that lower attenuation values for dark wort are partially due to the inhibitory effects of Maillard compounds on yeast metabolism. The application of dark caramel or roasted malts further led to elevated levels of the vicinal diketones diacetyl and 2,3‐pentanedione. Only large levels of roasted malt gave rise to two significant diacetyl peaks during fermentation. The level of ethyl acetate in beer was inversely related to colour, whereas the level of isoamyl acetate appeared to be affected by the use of roasted malt. With large levels of this malt type, negligible isoamyl acetate was generated during fermentation.     

PROTEIN PRECIPITATION DURING WORT BOILING: QUALITY ASPECTS OF DIMINISHED WORT BOILING TIMES OF BREWS PREPARED FROM PROANTHOCYANIDIN-FREE OR REGULAR RAW MATERIALS

When using proanthocyanidin-free materials for the production of beer, a reduction of the wort boiling time can be considered. In worts prepared with regular malt and tannin-free hop extract there is a continuous precipitation of the malt flavanoids while in brews prepared from proanthocyanidin-free malt and regular hops there is a simultaneous extraction and removal of the hop flavanoids leading to constant levels of these hop flavanoids. The results also show that the level of Kjeldahl nitrogen in worts boiled with hops will be the same as that in worts boiled with n-hexane tannin-free hop extracts. These results and the fact that more protein precipitates in brews containing no malt or hop proanthocyanidins suggest that, unlike what is the case during the development of beer haze, polyphenols are not necessary for an effective protein precipitation during wort boiling.     

New approach to the production of xanthohumol‐enriched beers

Xanthohumol is a hop polyphenol with proven positive effects on human health. The aim of this work was to use special malts (roasted malt and melanoidin malt) for the preparation of high‐gravity sweet worts with an extremely high xanthohumol content. The solubility of xanthohumol was higher in sweet worts prepared from roasted malts than from Pilsen or melanoidin malts. This sweet wort (xanthohumol ~20 mg L^?1) was used for the preparation of xanthohumol‐rich beer. The importance of melanoidins in xanthohumol solubility was also examined. Isomerization reactions occurring at increased temperatures is one of the main reasons for the loss of xanthohumol in the brewing process and therefore the most appropriate temperature for addition of xanthohumol products to sweet worts was determined. The influence of filtration and stabilization materials (diatomaceous earth, polyamide sorbents and tannic acid) on the concentration of xanthohumol in enriched beer was also examined. Only a small effect of these materials was shown in xanthohumol‐rich dark beers, with the exception of tannic acid, which removed a significant amount of this polyphenol. Copyright © 2013 The Institute of Brewing & Distilling.     

Influence of malt on the xanthohumol and isoxanthohumol behavior in pale and dark beers: A micro-scale approach

The main objective of this work was to understand which compounds are responsible for the partial inhibition of xanthohumol (XN) thermal isomerization during wort boiling of dark malts. With such purpose, worts from different kinds of malt (pale, caramel and roasted) were chemically characterized (e.g. antioxidant activity, polyphenols and melanoidins contents) and studied by several chromatographic techniques. Molecular exclusion chromatography experiments showed that adsorption of XN to polyvinylpolypyrrolidone is lower for the high molecular weight fractions. It seems likely that this is due to the reaction between XN and coloured substances that changes chemical properties of XN or, at least, results in the formation of complexes that have different chemical properties. This leads to an inhibition of XN isomerization observed in this work. It was also verified that the melanoidins content was significantly higher in the higher molecular weight fractions, suggesting that probably these compounds are the main responsible for the XN isomerization inhibiting effect.     

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.     

控制啤酒中残留草酸含量的探讨

通过对酿造原料（包括麦芽、大米、酒花）的考察，发现不同的麦芽品种中草酸含量各不相同，酒花对麦汁中的草酸含量影响较大，添加辅料大米有助于降低草酸，酵母发酵对草酸含量影响很小。当麦汁中的钙离子含量达到80mg／L时，啤酒中的钙离子浓度在60mg／L，啤酒中的草酸15mg／L左右。     

The Evolution of Dextrins During the Mashing and Fermentation of All‐malt Whisky Production

The production of malt whisky involves the mashing of barley malt, followed by the fermentation of the resulting wort without further treatment. While this process has many parallels to the production of an all‐malt beer, one of the main differentiating steps during substrate preparation is the inclusion of a boiling step for the wort in the production of beer. Other than the destructive action of the boiling process on microorganisms, the boiling also destroys all malt enzyme activity. Since a typical whisky wash is not boiled it carries through a certain proportion of microbial activity associated with the malt, but more importantly it retains some enzyme activity that has been activated during the malting and mashing processes. The changes in sugars and dextrins during both mashing and fermentation of the resulting wash were investigated. Evidence of the continuous amylolytic activity during an unboiled, all‐malt wash fermentation is shown; while no ongoing amylolytic activity could be deduced during the fermentation of a boiled all‐malt wort. Furthermore, the data suggests that the amylolytic activity during mashing and fermentation are different with regards to α‐amylase action linked to its multiple‐attack action pattern as a function of substrate conformation, temperature, and effectiveness of potential hydrolytic events.     

Quality of pilsner malt and roasted malt during storage

Malt is usually expected to be stable during 12 months of storage. However, in practice many brewers notice changes in malt aroma during storage. The oxidative stabilities of pilsner malt and roasted malt were evaluated during a 12 month storage at different temperatures (10 and 20 °C) and water activities (0.231 and 0.432). The radical content in malt kernels was measured by electron spin resonance spectroscopy and the volatile profile of the resulting sweet worts was measured by head‐space analysis followed by GC‐MS analysis. The storage of malt resulted in oxidative reactions and a large change of the volatile profile of the resulting worts. Roasted malt was much more unstable than pilsner malt, as illustrated by a higher initial radical intensity, larger radical decay during storage and a larger change in the volatile profile of the wort with increased amounts of lipid oxidation products. For both roasted malt and pilsner malt, good correlations were found between radical decay and changes in the volatile profile of the wort, where high temperature and high water activity resulted in the largest changes. During the 12 months of storage, the sugar extract of the wort made from the malts remained constant and was not affected by the chemical changes. This study suggests that chemical changes occurring in malts during less than 12 months of storage may potentially affect the aroma of beer, and that water activity and storage temperature should both be kept low in order to maintain a high malt quality. Copyright © 2014 The Institute of Brewing & Distilling     

Preparation of a Low Carbohydrate Beer by Mashing at High Temperature with Glucoamylase

A malt grist, supplemented with glucoamylase (1,4-α-D-glucan glucohydrolase, EC 3.2.1.3), was mashed isothermally at 70°C to produce wort with a real fermentability of over 87% and beer with a residual carbohydrate content of less than 0.75% w/v at an original gravity of 42°S. The effects of varying mash pH, calcium content, glucoamylase addition rate and mash conversion time were investigated. The process was effective even with undermodified malt. Pilot scale brewing trials shozved no adverse effect on beer foam quality when the glucoamylase preparation had a specified range of protease side-activity. The process has the advantage of ensuring glucoamylase inactivation during wort boiling while being shorter than the alternative of enzyme treatment of wort prior to boiling.     

Behaviour of Antioxidants Derived from Hops During Wort Boiling

The oxidative stability of wort at different stages during wort production and the radical scavenging characteristics of α‐, β‐, iso‐α‐acids and a hop polyphenol extract were evaluated using ESR spectroscopy and DPPH• radical quenching measurements. Radical generation in unhopped wort was significantly, positively correlated with heating rate prior to boiling but not with dissolved oxygen content. Hop α‐ and β‐acids showed similarly significant radical quenching abilities, while iso‐α‐acids and a hop polyphenol extract displayed a negligible effect. Isomerization of α‐acids to iso‐α‐acids reduced wort's antioxidative capacity. Commercially available hop products with varying polyphenol content showed similar radical inhibiting properties, which were a function of hop acid content. Relative to an unhopped treatment, hop additions to wort resulted in significantly lower amounts of Strecker aldehydes in stored beer.     

异构酒花颗粒在啤酒酿造中的应用研究

对异构酒花颗粒和普通酒花颗粒进行了对比研究。结果表明,添加异构酒花颗粒可减少苦味物质的损失,酿造出的啤酒优于只采用普通酒花颗粒酿造出的啤酒,特别是酒花香突出,泡特性好。     

Sensory and Instrumental Flavour Analysis of Wort Brewed with Dark Specialty Malts

In order to explore the flavour produced by dark specialty malts, wort samples were brewed with different malts and evaluated by sensory and instrumental analysis. With increasing wort colour, a trained tasting panel detected more intense bitter and burnt flavours, whereas sweet and husky flavour notes decreased. Conversely, caramel and bread‐like flavour attributes had a maximal intensity for the intermediate wort colours. Tasting of 20 EBC worts indicated that the flavour profile was significantly affected not only by malt level and malt colour but also by malt origin. Furthermore, the darkest caramel malt (480 EBC units) was found to contain most Maillard aldehydes as determined by the reaction with thiobarbituric acid. Similarly, other intermediate products of the Maillard reaction such as acetic acid, diacetyl and 2,3‐pentanedione were found to arise in a higher concentration in dark caramel malts (220–480 EBC units) than in roasted malt (1200 EBC units). Dynamic headspace GC/MS further revealed that brewing with dark specialty malts considerably increased the level of 3‐methylbutanal, its aldol condensation product (2‐isopropyl‐5‐methyl‐2‐hexenal) and heterocyclic Maillard compounds. In contrast, dark malts drastically reduced the amount of hexanal in wort. By means of HPLC, it was established that only extreme roasting temperatures lead to the thermal degradation of ferulic acid to 4‐vinylguaiacol in malt.     

Brewing with Rice Malt — A Gluten‐free Alternative

The preparation of beer‐like beverages with rice malt as the only raw material is reported. Several tests were performed on a laboratory scale and in a 25 L‐capacity pilot plant. Both the decoction and the infusion procedure were tested; malt and water were mixed in a ratio 1:3.5 for both methods and the mash was brewed without adding exogenous enzymes. The obtained worts were fermented using bottom fermenting yeasts, while “beers” were re‐fermented utilizing top fermenting yeasts and adding either sterile wort or sugar. A maximum ethanol of 4.5% vol. was obtained after the primary fermentation from an initial wort with an original gravity of 11.8°Plato. All parameters of the beer were found to be acceptable using a standard beer analysis. Owing to a suitable hop addition, an aroma very similar to that of a normal beer was obtained.     

Differences in protein content and foaming properties of cloudy beers based on wheat malt content

To investigate differences in protein content, all barley malt beer, wheat/barley malt beer and all wheat malt beer were brewed, and the protein during mashing, wort, fermentation and beer determined. It was shown that protein was mainly extracted during mashing and the protein rest phase, decreased in the early stages of fermentation and remained almost steady during wort boiling and cooling, in the middle and late stages of fermentation. By separating beer foam from beer, similar protein bands of 51.7, 40.0, 27.3, 14.8, 6.5 and < 6.5 kDa appeared in the three beers, defoamed beers and beer foams using the sodium dodecyl sulphate polyacrylamide gel electrophoresis. Quantitatively, protein bands of 6.5–14.8 and <6.5 kDa had the highest contents in the three beers. Unique bands at 34, 29.2, 23.0, 19.7 and 17.7 kDa were found in beer, defoamed beer and beer foam from wheat beer and all‐wheat malt beer, respectively. Wheat beer foam showed the best foam stability and the protein in all barley malt beer showed the best migration to the foam. The beer foam properties were influenced by not only protein content but also protein characteristics and/or origin. It is suggested that the barley malt contributed the beer foam ‘skeleton protein’ while protein components from wheat malt kept the foam stable. © 2018 The Institute of Brewing & Distilling     

Brewing with 100% Oat Malt

Oats are a cereal with beneficial nutritional properties and also unrealized brewing potential. Furthermore, oats can be tolerated by the majority of people who suffer from celiac disease. Malting of oats produced a malt, which was found suitable for brewing a 100% oat malt beer. The mashing regime, designed by using mathematical modelling, was successfully transferred to a pilot scale plant. The improved lautering performance of oat malt was due to its higher husk content, which also led to a lower extract content in oat wort when compared to barley wort. The protein profile of oat wort, as measured by using Lab‐on‐a‐Chip analysis, revealed that there was no significant difference in the protein profile between oat and barley wort. The fermentation of oat and barley worts followed the same trend; differences could only be seen in the higher pH and lower alcohol content of the oat beer. The flavour analysis of oat beer revealed some special characteristics such as a strong berry flavour and a lower amount of staling compounds when forced aged. This study revealed that it was possible to brew a 100% oat malt beer and that the produced beer was comparable to a barley malt beer.     

Corn grist adjunct – application and influence on the brewing process and beer quality

In the brewing industry, barley malt is often partially replaced with adjuncts (unmalted barley, wheat, rice, sorghum and corn in different forms). It is crucial, however, to preserve constant quality in the beer to meet the expectations of consumers. In this work, how the addition of corn grist (10 and 20%) influences the quality of wort and beer was examined. The following parameters were analysed: wort colour, dimethyl sulphide (DMS) and protein content, non‐fermentable extract, extract drop during fermentation, alcohol content and the attenuation level of the beer, together with filtration performance. The samples (all‐malt, and adjunct at 10 and 20% corn grist) were industrial worts and the beers produced in a commercial brewery (3000 hL fermentation tanks). The application of 10 and 20% corn grist had an effect on the wort colour, making it slightly lighter (11.1 and 10.5°EBC, respectively) than the reference barley malt wort (12.2°EBC). The free amino nitrogen level, DMS and non‐fermentable extract were significantly lower in the worts produced with the adjunct; the alcohol content and attenuation levels were higher in the beers produced with adjunct. The use of corn grist, at the level of up to 20% of total load, appears to affect some of the technological aspects of wort and beer production, but it does not significantly influence the final product characteristics. Copyright © 2014 The Institute of Brewing & Distilling     

DIFFERENCES IN UTILISATION OF THE ESSENTIAL OIL OF HOPS DURING THE PRODUCTION OF DRY-HOPPED AND LATE-HOPPED BEERS

Late-hopped and dry-hopped beers were prepared and their lipophilic constituents extracted using Amberlite XAD-2 resin. Examination of the volatile constituents by GC-MS confirmed that most of the hop oil added towards the end of wort boiling is lost by evaporation. Part of the material which survives boiling is chemically transformed by yeast during fermentation. Dry-hopped beer contained compounds more representative of the original hop oil than did the corresponding late-hopped beer. A liquid carbon dioxide extract of hops, rich in essential oil, has been fractionated by column chromatography on alumina-silica giving preparations which simulate either late-hop or dry-hop character.