Hop products

The use of hops in the form of hop extract has spread rapidly the yield of the extract is better, yet insufficient. The production of a satisfactory hop extract quahty, ie, no taste difference to beer hopped by using other "natural" hop products, has appeared to be a science or art in itself Use of the right solvent and distillation is the key point, and many unsuccessful attempts have been made. The latest and most successful method, using the so-called Hquid carbon dioxide extraction, meets the high quaUty demands almost perfecdy. Preisomerization of the resins makes it uimecessary to boil them with the wort they can be added directly to the finished beer to avoid poor yield (through boiling) and the loss of resins (during fermentation). 

Figure 8.1-14. Return on Investment (ROI) for hops production under different processing conditions, and dependence on processing-weeks.

EBC Technology and Engineering Forum. Hops and Hop Products Manual of Good Practice. Nuremberg Getranke-Fachverlag Hans Carl, 1997. 

Institute of Brewing Recommended Methods. Hops and hop products 6.5. Alpha- and beta-acids in hop extracts by HPLC. 

Analytica—EBC methods, a- and / -Acids in hops and hop products by HPLC. 

GK Buckee. Estimation of a-, /3- and iso-o-acids in hops, hop products and beer using high performance liquid chromatography. J Inst Brew 91 143-147, 1985. 

The separation of the wort from the insoluble residues (leuters), also called treber, is achieved by the traditional process in a cylindrical container with double bottom the upper one is a sieve on which the treber forms a natural, approx. 35 cm thick filter layer. The resulting filtrate (flavouring) is collected in the brew kettle (hop kettle) and combined with hop or hop products. The quantity of added hop depends on the type and quality of beer. 

The new edition appears as two volumes because a single one would be inconveniently bulky. The first volume outlines the entire process and leads from barley, malting and water to the production of sweet wort. In the second volume there are chapters on hops and hop products, production of hopped wort, fermentation, yeast biology and all aspects of beer qualities and treatment. 

In order to increase the stilbene level, stilbene-enriched hop products and brewery process modifications are needed (e.g., adding a stilbene-enriched ethanolic hop extract after fermentation significantly increases the beer stilbene potential). 

Biendl M, Mitter W, Peters U, Methner FJ (2002) Use of a xanthohumol-rich hop product in beer production. Brauwelt Int 1 39 2... 

Biendl M, Methner FJ, Stettner G, Walker C (2004) Brewing trials with a xanthohumol-enriched hop product. Brauwelt Int 111 182-184... 

Magalhaes, P. J., Dostalek, R, Cruz, J. M., Guido, L. R, Barros, A. A. (2008). The impact of a xanthohumol-emiched hop product on the behavior of xanthohumol and isoxanthohumol in pale and dark beers a pilot scale approach. Journal of the Institute of Brewing, 114,246-256. 

Wort boiling with hops or hop products is done in a brew kettle (hop kettle) in which the initial and subsequent worts from the lautering step are collected. Addition of hops is adjusted according to the type and quality of beer desired. The quantity (in hop cones/hectoliter) for fight lager beer is 130-150 g for Dortmund-type beer, 180-220 g for Pilsener beer, 250-400 g for dark Munich beer, 130-170 g and for malt beer and dark bock beer, 50-90 g. The critical factor is the content of bitter substances in the hops selected. The utilization of the bitter substances (a-acids) is only 30-35%. 

Table 4.1 Weight and volume of hops and hop products per million hectolitres beer...

The primary aromatic substances in beer are derived from raw materials (barley or hops) that confer the beer s typical odour and taste. Bitter acids of hops have a bitter taste (see Section 8.3.5.1.3), but hop cones also contain 0.3-1% m/m of terpenoids (60-80% of hop essential oil), which have a considerable influence on the smell of beer. The main components of aromatic hop oils are sesquiterpenic hydrocarbons in which a-humulene, P-caryophyllene and famesene dominate. The major monoter-penic hydrocarbon is myrcene. For example, the essential oil content of fine aromatic varieties, such as Saaz, is 0.8% m/m, of which 23% is myrcene, 20.5% a-humulene, 14% famesene 6% and P-caryophyUene. Significant components of the hop aroma in beer are mainly isomeric terpenoid monoepoxides resulting from autoxidation and diepoxides of a-humulene and fS-caryophyUene, but also other terpenoids. Important components of hops odour are also various alcohols (such as geraniol and hnalool), esters (ethyl 2-methylpropanoate, methyl 2-methylbutanoate, propyl 2-methylbutanoate and esters of terpenic alcohols, such as geranyl isobutanoate), hydrocarbons, aldehydes and ketones formed by oxidation of fatty acids, such as (3E,5Z)-undeca-l,3,5-triene, (Z)-hex-3-enal, nonanal, (Z)-octa-l,5-dien-3-one, their epoxides, such as ( )-4,5-epoxydec-2-enal and sulfur compounds. Other important components of hops are so-called polyphenols (condensed tannins) that influence the beer s taste and have antioxidant effects. Less important compounds are waxes and other hpids. Hop products, such as powder, pellets and extracts (by extraction with carbon... 

Since 1980, the formerly used solvent methylene chloride has been substituted step by step by CO2 processes, covering nowadays over 30% of the hops production. Such plants are located in Europe, United States, and Australia while the first two countries use supercritical CO2, the latter use a process involving liquid CO2. Due to less solvent power, liquid extraction requires more than 50 kg of C02/kg hops in order to obtain the demanded yield of 9 5 wt% for a-acid, although hardly getting any hard resins. 

At present the alpha acids analysis of hops and of hops products is the most... 

The dried flower cones of the female hop plants of various sorts and cultivars are materials for alpha acids determinations. In the last decades, several preparations such as hop extracts, hop pellets, enriched hop, have been introduced on the market, aiming to stabilize the brewing value of hops or to improve the beer quality. Nowadays, more than half of the total hops production is processed in this way. 

Alpha acids have a chiral centre, and, as naturally occurring compounds, they display optical activity. Measuring the optical activity by polarimetry for the determination of the alpha acids is due to Salac and Dyr (4). The drawbacks of the polarimetric approach are the difficulty of measuring accurately a small rotation angle, the unpredictable presence of other optically active compounds in the hops or hop products and the interference of chlorophyll-derived green-coloured compounds. Since the rotation angle is measured at the yellow D-line of a sodium lamp, a green colour indeed hinders the measurement. The silica gel filtration procedure, mentioned before, improves the polarimetric analysis. Two contributions based on this approach were worked out in our laboratory (5,6). 

Quantitative analyses of alpha and iso-alpha acids are needed to guide commercial transactions. Hops, hop products and hop extracts may be purchased on the basis of their alpha acids content and the same may apply to pre-isomerized extracts. In these transactions there is a seller and a buyer. It is to the seller s interest that the analytical figures are high and the opposite applies of course to the buyer. Eventually a neutral party may be contacted to perform the necessary analyses. The importance of the method chosen for the analysis is, however, decisive. Both parties should agree in advance on the method to be followed and should be aware of some of the consequences and possibilities. 

The molecular weight of the cis and trans isohumulones and of the cis and trans isoadhumulones is 362 while that of the cis and trans isocohumulones is only 348. Equal weight concentrations of cis and trans isocohumulone, compared to cis and trans isohumulone-isoadhumulone. will therefore contain 4% more equivalents. Some methods for iso-alpha acids analysis could be sensitive to this factor. The percentage of cohumulone in hops and hop products is also variable. The same variability will therefore occur in the composition of the iso-alpha acids. In hops with a low cohumulone content (about 15 % cohumulone is the lowest) the average molecular... 

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