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.     

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.     

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.     

The effects of three mash separation systems on the isomerisation of hop alpha-acids

This study investigates the effects of wort composition from three lautering systems on hop utilisation at different hop boiling and dosing times. A response surface methodology was applied with 60 single tests at a 5 litre scale. The parameters, which were varied, were lautering system, boiling time without hops, boiling time with hops and α-acid dosage. It was shown that the wort composition from the different lautering systems requires different boiling times or enables the reduction in boiling time with hops. Although the pH and original gravity of the lauter tun and mash filter worts were similar, different boiling times were necessary to achieve the same concentration of iso-α-acids. Further, there were variations in fatty acid composition of the worts. In order to be able to assess the effects on a larger scale, six brews were performed in a 10 hL pilot brewery. The utilisation of hop bitter substances differed despite the same boiling time and the same α-acid dosage in relation to the total quantity of wort. In addition, no significant losses of hop bitter substances were observed in the wort from a continuous mash filtration system due to the process related higher dosage of α-acid. Both sets of experiments showed that the boiling times depend on the wort composition and increased as follows: novel continuous mash filtration system < mash filter < lauter tun. The results lay the foundation for calculating the optimal parameter settings for each brewery to optimise the hop isomerisation rate. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of 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 AND MALT PHENOLICS IN LAGER BREWING

Malt tanninogens were completely removed from wort by Nylon 66 treatment and a hop phenolic extract added in amounts calculated to restore the original tanninogen level as well as the level derived only from hops. In the former case, the restoration was incomplete, which was indicative of a higher polymeric tanninogen content of hops as compared with malt, while in the latter case, the chemical interactions during kettle boiling affected the original anthocyanogen-to-catechin ratio. Physical stabilities of all the experimental brews were significantly improved in comparison with the control all-malt lager, indicating that malt tanninogens are more haze active than hop tanninogens. Hop intensity and bitterness, as well as colour, were higher in the experimental brews than in the control lager.     

COMPOSITION OF NON-STARCH POLYSACCHARIDES IN WORT AND SPENT GRAIN FROM BREWING TRIALS WITH MALT FROM A GOOD MALTING QUALITY BARLEY AND A FEED BARLEY

Worts and spent grains were obtained from pilot-scale brews using malts of two barley varieties differing in malting quality. Triumph was used as an example of a good malting quality barley and Golf as a typical feed grade barley. Arabinoxylan concentrations were similar in worts of both varieties, whereas (1–3), (1–4)-β-glucan concentrations were much higher in wort prepared from Golf malt than in wort from Triumph malt. From the worts, polysaccharide fractions were isolated by ethanol precipitation and characterised. Results indicated the presence of high molecular weight arabinoxylans and (1–3), (1–4)-β-glucans. The arabinose to xylose ratios in the precipitates were considerably higher than in total worts. Methylation analysis showed little differences between precipitated wort arabinoxylans from both varieties. In comparison to water-insoluble arabinoxylans extracted from barley and malt, the precipitated wort arabinoxylans were richer in xylopyranose residues substituted with arabinose residues at both 0–2 and 0–3. Viscosities of the hopped worts of both varieties decreased after treatment with endoxylanase 1 from Aspergillus awamori. This confirms that arabinoxylans play a role in determining wort viscosity, possibly through interactions with (1–3), (1–4)-β-glucans.     

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.     

PREDICTION OF WORT COLD BREAK PERFORMANCE OF MALT AND ITS APPLICATIONS

A new test for wort cold break performance of malt was developed, based on laboratory mashing and boiling, followed by adding a range of concentrations of copper finings at different wort pH values. The test predicted successfully brewery wort cold break performance, with malts being ranked on the basis of production of wort cold break which required a low concentration of copper finings for precipitation and flocculation. A relationship between wort pH and the concentration of copper finings required to give an acceptable cold break was established with both brewery and laboratory worts. A strong correlation (r = 0.922, p << 0.01) was found between copper finings concentration and the two variables wort pH and the amount of cold break protein. Differences in brewery cold break performance were explained largely by a difference in wort pH, although other as yet unidentified factors appeared to be involved. Cold break performance of malts was affected by both crop year and protein modification, but not total nitrogen or total soluble nitrogen. A brewing trial is described in which wort pH is increased at the end of boiling, leading to significant improvements in both cold break and isinglass finings performance.     

Reducing power of hop cultivars and beer ageing

Since lipid auto-oxidation during wort boiling is a determining for the appearance of staling flavour in aged beers, we have investigated the reducing power of hops added in the boiling kettle. An assay based on the inhibition of linoleic acid oxidation in the presence of an initiator [2,2′-azobis(2-amidino-propane) dihydrochloride=AAPH] enabled us to distinguish hop varieties and conditionings. Large differences in hop flavanoid contents explained the higher antioxidant activity of low-α-acid samples versus bitter varieties and CO₂ hop extracts. As expected, adding hop pellets to the kettle effectively increased the overall reducing activity of wort. Supercritical CO₂ hop extracts had no significant effect due to their extremely low level of polyphenols. The concentration of the very well-known marker of beer ageing, trans-2-nonenal, was lower in boiled wort exhibiting a better reducing power. The AAPH reducing power test applied to hops or worts was thus efficient to predict the nonenal synthesis during boiling. Hop varieties and conditionings emerged from this work as key-parameters for improving the reducing power of wort and the flavour stability of the final product.     

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.     

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.     

THE INFLUENCE OF MASHING CONDITIONS ON WORT AND BEER QUALITY

From a comparison of the performance of ale and lager malts mashed by constant temperature infusion, by temperature programmed infusion, and by decoction procedures it emerges that malt modification and the pattern of kilning are as important in determining the composition of wort as are the mashing conditions. Worts with appropriate levels of amino and total nitrogen and of fermentable sugars may be obtained by selecting lightly-dried well-modified malts and mashing with a constant temperature infusion rather than by using less modified malt in conjunction with more complex mashing programmes. Ale malts yield worts of lower pH which is reflected in a slight reduction in hop utilization. Head retention is improved by the use of undermodified malts but colloidal stability is improved when well-modified malts are used. In the case of well-modified malts a high final curing temperature is not a prerequisite for achieving good colloidal stability in beer.     

SOME FACTORS INFLUENCING HEAD RETENTION AND YEAST-HEAD FORMATION WITH SPECIAL REFERENCE TO COMMERCIAL WORT SYRUP

The fermentation patterns of worts prepared from two barley syrups, a green-malt syrup and a mixture of 50% pale-ale malt and 50% carbohydrate syrup have been compared with that of an all-malt wort. No significant differences were detected in the brewing performance of three of these syrups. One barley syrup, however, exhibited reduced yeast-head formation. The effects of carbon dioxide retention, hop substances, carbohydrate content and nitrogen quality on the formation of yeast-head have been investigated. The presence of increased amount of head-negative materials, particularly phospholipids, is of prime importance in the reduced yeast-head formation of this syrup wort. After fining and conditioning, beers from this syrup possessed a substantially improved head retention, superior even to that of an all-malt beer.     

INHIBITOR OF FLUORESCENCE REACTIONS BETWEEN CALCOFLUOR AND β-(1,3)(1,4)-D-GLUCAN IN BEER AND WORT

An inhibitor of calcofluor fluorescence reaction in beer and wort was shown by analyzing beers and worts containing no β-glucan. The inhibitory activity was enhanced against the fluorescence reaction which is intensified by linkage of calcofluor with β-glucan compared to the fluorescence of calcofluor itself. The investigation indicated that the inhibitor was derived from malt and is produced during the germination process. The inhibitory activity in beer and wort changed with the degree of malt modification and the ratio of malt in the grist. Japanese beers had a wide range of inhibitory activities against the calcofluor fluorescence, lowering the apparent β-glucan contents by 12 to 20%. The inhibitor in beer and wort appeared to be an acidic compound with a molecular weight of less than 1000 daltons.     

The Impact of Low Heat Load and Activated Carbon Treatment of Second Wort on Beer Taste and Flavour Stability

There is a vast repository of knowledge regarding improving beer taste stability via wort boiling. However, as far as we are aware, there are few reports dealing with taste stability improvement in terms of quality characteristics by boiling, under proper conditions, the first wort and second worts separately. In this study, more than 50 brews in a pilot scale brewing facility were conducted to investigate suitable boiling conditions for first and second worts. When the second wort (i.e., the last 10% of the total filtered wort) was kept under a low heat load atmosphere (78°C), casted to the boiling first wort, and then re‐boiled for 10 min, the produced beer exhibited no significant differences compared to that of the general beer in terms of taste stability. However, when an adsorbent (bentonite, silica gel, activated carbon or PVPP) was individually added to the second wort and the same boiling procedure was performed, the oxidized flavour of the forced aged beer, treated with activated carbon, significantly decreased, compared to that of the general brew (level of significance α = 0.01). The data from the chemical analysis and fermentation behavior are presented.     

THE FATE OF HUMULONE DURING WORT BOILING AND COOLING

Variations in the nature of the grist, mashing temperature, gravity and content of anthocyanogens of wort influenced the yield of break obtained after boiling with humulone, but not the bitterness of the resulting worts. Only small amounts of resin were found on the break and although increased break formation resulted in increased adsorption of resin this did not lead to measurable differences in the bitterness of wort. The bitterness of the cooled wort was independent of the degree of aeration and speed of cooling.     

THE RELATIONSHIP OF DIMETHYL SULPHIDE LEVELS IN MALT,WORT AND BEER

The half-life for the conversion of malt dimethyl sulphide (DMS) precursor to free DMS has been determined at various temperatures and pH values. At pH 5·2 the half-life of the precursor in wort (S.G. 1·060) at its boiling point is 38 min, and is doubled for each 6°C fall in temperature. At pH 5·5 the half-life at the boiling point is 32·5 min. Knowing the stability of the precursor at the various temperatures in the brewing process, the extent of conversion to free DMS in wort at pitching can be predicted for malt of a given precursor content and for a given set of process conditions. The results of DMS analyses of samples taken during brewery trials are in reasonable agreement with the predicted values. This work involved infusion mashing only, but the same principles apply to decoction mashing. The fate of precursor and free DMS during fermentation and conditioning has been followed on a production scale. With some brews, where high levels of free DMS were present at pitching, much free DMS was lost during fermentation. Also, precursor DMS reappeared in the beer after a few days and there was some increase in the level of free DMS. The DMS precursor in green malt has been isolated by ion-exchange and gel-filtration chromatography. A preparation has been obtained which has 0·6 mol potential DMS per mol amino nitrogen. Thin layer chromatography showed that the preparation and its hydrolysis product had the same R_f values as S-methylmethionine and homoserine respectively.     

VOLATILE HOP CONSTITUENTS IN WORT

Using a distillation-extraction technique, a commercial wort, both before and after hopping, was analysed by GLC for the presence of volatile compounds contributed by hops. The hopped wort contained at least 0·32 p.p.m. of volatile hop constituents which is probably sufficient to influence flavour. Most of these belonged to a group of water-soluble compounds which have not previously been detected in worts or beers.     

IS WORT BOILING NECESSARY?*

Experiments are described in which the boiling of wort is replaced by a hold at 85° C, and the effects upon beer quality are reported. Beers with normal shelf-life and sound flavour can be produced without the wort having been boiled.