ADDITION OF HOP EXTRACTS TO BEER USING LIQUID CARBON DIOXIDE*

A method is described for imparting hop character to beer using extract prepared by treating hops with liquid carbon dioxide. The long contact times required for conventional dry-hopping techniques are avoided, and the use of liquid carbon dioxide as a medium for dispersal of the extract obviates problems due to residual organic solvent or emulsion stabilizers. Beers in which hop character was introduced in this way were found to be similar in flavour to control beers treated with portions of the same hop extract dissolved in ethanol.     

USE OF EXTRACTS PREPARED WITH LIQUID CARBON DIOXIDE AS A SUBSTITUTE FOR DRY HOPS

Liquid carbon dioxide hop extracts were prepared for use as a substitute for dry hops. Many of these extracts were oil rich fractions containing up to 14% (w/w) hop oil. Extracts of Styrian Golding, Wye Target and Wye Northdown hops were used to treat ales prior to completion of beer processing and subsequent packaging. Emulsion/suspension systems were developed as carriers to facilitate addition of these extracts to beers before the chilling process. A loss of hop character from beer was found to occur during fining and filtration. Beers, treated with the extracts, exhibited natural though varietally distinct dry hop character. Production scale trials using these extracts have been successfully carried out to dry hop a brewery conditioned draught bitter and to match a traditionally dry hopped premium pale ale. The quantities of extract used indicated that economies in hop usage can be achieved when substituting liquid carbon dioxide hop extracts for dry hops.     

PRODUCTION-SCALE APPARATUS FOR THE INJECTION OF HOP EXTRACTS INTO BEER USING LIQUID CARBON DIOXIDE

Extracts of hops made with liquid carbon dioxide can be substituted for dry hops to introduce the flavour of hop oils into beer. Apparatus has been devised so that such extracts can be redissolved in liquid carbon dioxide and then metered into beer. Successful trials have been carried out on the commercial scale.     

The Oxygenated Sesquiterpenoid Fraction of Hops in Relation to the Spicy Hop Character of Beer

Hop‐derived sesquiterpenoid‐type oxidation products have been associated with a spicy or herbal hoppy beer character. However, the flavour threshold values of hitherto identified oxygenated sesquiterpenes are generally much higher than their estimated levels in beer. By applying two‐step supercritical fluid extraction of hop pellets using carbon dioxide, followed by chromatographic purification of the enriched sesquiterpenoid fraction, highly specific varietal hop oil essences containing all main oxygenated sesquiterpenes were obtained. Post‐fermentation addition (at ppb levels) of these purified sesquiterpenoid essences from various European aroma hops led to distinctive spicy or herbal flavour notes, reminiscent of typical ‘noble’ hop aroma. It is concluded that a spicy hop flavour impression in beer depends significantly on minor constituents of the natural sesquiterpenoid hop oil fraction.     

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.     

PREPARATION OF HOP EXTRACTS WITHOUT USING ORGANIC SOLVENTS

Extraction of hops with liquid carbon dioxide at ambient temperature provides an attractive means of producing hop extracts which are rich in α-acids and free from hard resins, polyphenols, pigments and residual organic solvents. The resulting yellow extracts give beer with a clean bitter flavour when they are added during wort boiling. Manufacturing costs using the process are likely to be substantially less than in a conventional hop extraction plant.     

Mechanism of gushing induction by carbon dioxide transfer activator

The article deals with the activation of carbon dioxide transfer from carbonated beverages. As a model compounds agents produced by Trichoderma reesei and harzianum and degraded hop iso‐extract were selected. These substances were added to the carbonated water or beer and their effect was compared. The method of pressure growth in the bottle headspace after rapid piercing and re‐closing the bottle was used. Some carbon dioxide transfer activators accelerated CO₂ escape even at rest; others required shaking for different periods. The pressure growth measurement allowed the prediction of gushing before its occurrence. Copyright © 2017 The Institute of Brewing & Distilling     

奶啤的研制

以牛奶、麦芽和酒花为主要原料,通过二次生物发酵研制出具有奶香和啤酒风味的奶啤饮料。通过实验确定奶啤的最佳配方及生产工艺流程并对奶啤的稳定性进行探讨,从而研制出即有啤酒的低酒精度、泡沫丰富和适度的二氧化碳,又具有酸乳饮料的酸甜可口、营养全面的奶啤饮料。     

仙人掌奶啤的研制

探讨了以仙人掌、牛奶、麦芽和酒花为主要原料经过二次生物发酵研制既有啤酒的低酒精度,泡沫丰富和适度的二氧化碳,又具有酸乳饮料的酸甜可口,营养全面且具有保健功能的绿色饮料—仙人掌奶啤。通过实验确定仙人掌奶啤的最佳配方及仙人掌汁的添加方式,并对奶啤的稳定性进行了探讨。     

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.     

High Pressure Inactivation of Lactobacillus plantarum in a Model Beer System

ABSTRACT: The effects of hop extract and ethanol on growth, high pressure inactivation, and survival of Lactobacillus plantarum were determined in model beer. Corresponding to the beer spoiling ability of this strain, levels of hops and ethanol typical for beer did not inhibit growth. Pressure death time curves determined at 300 MPa were described by an empirical model taking into account the sigmoid shape of survivor curves, sublethal injury, and the presence of baroresistant cells. Ethanol (5 and 10%) enhanced pressure effects on L. plantarum whereas hop extract (50 and 100 ppm) was less effective. In contrast, hop extracts killed pressurized cells during subsequent storage in beer but ethanol did not.     

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.     

HOP PRODUCTS

Hop products have established an important and permanent position in the brewing raw materials market. Hop pellets and hop extract offer significant advantages to traditional brewers. However, the ultimate hop product is the isomerised hop extract, which can now be produced without the involvement of organic solvents. Still to be resolved and hence controlled is the contribution of the hop oil fraction to beer flavour.     

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.     

啤酒泡沫稳定剂的应用研究

分析了泡沫稳定剂的种类、品牌及浓度梯度对啤酒泡持、粘度和总蛋白的影响,研究了泡沫稳定剂对货架期啤酒泡沫稳定性的影响。结果表明,进口PGA和异构化酒花浸膏效果较好;添加进口PGA和异构化酒花浸膏90d后样品的泡持提高比例仍大于10％,货架期泡沫稳定性较好;异构化酒花浸膏的胶体稳定性最好。建议进口PGA的添加量最高不超过40mg／L。感官品评结果显示,添加六氢异构-1酒花且添加量为30mg／L的酒样最佳,风味略后苦,柔和。     

SOLUBILITY OF HOP α- AND β-ACIDS IN LIQUID CARBON DIOXIDE*: ADDENDUM: SOLUBILITY OF PESTICIDES IN LIQUID CARBON DIOXIDE

A procedure is described for determining the solubility of hop α- and β-acids in liquid carbon dioxide. Results have shown that the optimum temperature range for the extraction of hops with liquid carbon dioxide is +5 to +10°C. A number of pesticides used by hop growers are appreciably soluble in liquid carbon dioxide.     

The Relative Significance of Physics and Chemistry for Beer Foam Excellence: Theory and Practice

Bubble nucleation sites in beer glasses should be uniformly small to ensure that the foam produced comprises homogenously small bubbles with attendant reduced degrees of disproportionation. The latter phenomenon is also hindered by increased film thickness in foam, which in turn will be enhanced by increased localised viscosity, encouraged perhaps by polysaccharide‐polypeptide complexes. Erring on the “high end” of specification for carbon dioxide will promote replenishment of foam through beading. Nitrogen at a relatively low level (15–20 ppm) will hinder disproportionation with limited suppression of hop aroma and introduction of undesirable textural features. Hydrolysed hordein appears selectively to enter beer foams at the expense of the more foam‐stabilising albuminous polypeptides, suggesting that any future procedures that might selectively eliminate hydrolysed hordein components from beer would be expected not only to enhance haze stability but also foam, by eliminating species that preferentially enter into the bubble but have less foam‐stabilizing capability once they are there.     

A study of beer bitterness loss during the various stages of the Romanian beer production process

Beer is one of the oldest known alcoholic beverages produced by a yeast fermentation of a cereal extract that was germinated in water beforehand. The bitter taste of beer comes from the group of substances introduced during wort boiling, which are the extracted components of hops. The aim of this study was to determine some characteristics of beer (original extract, alcohol content, colour, pH, total acidity, carbon dioxide and bitterness values) during the three stages of the beer production process in a typical Romanian brewery. Measurements were carried out on 60 samples of beers, 10 measurements for each step of the process examining wort, unfiltered fermented beer and bottled beer (final product) from two different types of beer (light and dark). Statistical process control of the beer was performed. Losses in the bitterness units during the production process were between 24.7 and 41.54%, reported in terms of final product. Copyright © 2013 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.     

THE MANUFACTURE OF HOP CONCENTRATES AND EXTRACTS*

Manufacture of the traditional hop concentrate (i.e., a product containing the chemically unchanged natural hop constituents apart from useless inert material) is increasing both in Europe and in America; this traditional concentrate, which is added to the copper, retains the varietal characteristics of the parent hop. In determining replacement ratios it is important to assess bitterness by tasting trials, as analytical assessments of bitterness may give misleadingly low results when concentrates are used. Although chemically pre-isomerized extracts can be prepared for addition to sweet beer, it is improbable that this type of extract will be used extensively until a great deal more is known about transformations which take place during hop boiling; such an extract, however, does allow maximum utilization of hop bittering principles. The selection of hops for high α acid content and the separate addition of the flavour components such as hop oil appears to be a desirable development for the near future.