Thermal load is often considered as a vague and obscure burden for brewers. In order to clarify the concept of thermal load, this paper aimed to characterize and quantify thermal load during wort boiling. Thermal processing of wort was found to cause the accumulation of Maillard intermediates, which might lead to the generation of off-flavours during beer ageing. The amount of intermediates could be quantified in terms of HMF-equivalents. A part of these intermediates was reduced by yeast during fermentation. The remaining non-reducible intermediates in beer can therefore be considered as the chemical memory of thermal load on wort.In order to quantify thermal load in wort, the kinetic behaviour was examined and a pseudo 0th order kinetics was established. The quantification of thermal load was then captured in a formula, which consisted of two terms. The first is a specific wort term, which evaluates the susceptibility of a particular wort to applied thermal load. This tool could be used by every brewer to predict the effect of boiling process changes on the wort. In addition, a boiling system term was created. Although the latter term is highly theoretical, it provides insights in the impact of differences in boiling intensity on thermal load of wort.
Although beer pasteurization has been the object of a number of studies, there is no published data dedicated to investigation of the effects of pasteurization on aluminium content of beer and aluminium migration from aluminium package to beer. Thus, in order to investigate the changes of aluminium content along with aroma compounds changes, GF-AAS method with Zeeman background correction and GC-HSS method were used in this work. Also, for other analytical determinations, classic physical and chemical methods were applied. Pitting corrosion of aluminium cans was determined by microscopic analysis. Analyses were conducted periodically throughout seven months of storage on two different brands of beer filled in aluminium cans (pasteurized and non-pasteurized samples). One part of samples was stored in a refrigerator (4^oC) and the other in a thermostatic chamber (22^oC). The effects of pasteurization on aluminium content and aroma compounds changes were observed. Pasteurized samples, at the beginning of storage (22^oC), showed a higher content of aluminium and can corrosion. At the end of storage time in non-pasteurized samples, presumably via the activity of present microorganisms, more expressive can corrosion and aluminium migration was observed. Levels of aroma compounds in both pasteurized and non-pasteurized beer samples decreased during storage negligibly.
Dans le cadre de ce travail, on a pu montrer que la repartition chirale du R-linalool etait stable a pres de 94 % dans le houblon aromatique du houblon presse, jusqu'aux produits conventionnels du houblon.- Dans la biere on a trouve parfois des teneur en R-linalool nettement plus faibles. On suppose comme cause une racemisation pendant la production de la biere. Le degre de racemisation depend fortement du mode de houblonnage.- Au cours du vieillisement de la biere, la racemisation se poursuit pendant que la teneur en linalool reste constante. Il en resulte une perte d'arome appreciable par l'analyse organoleptique. La valeur du pH semble etre un facteur important dans la transformation du R-linalool en S-linalool au cours du vieillissement de la biere.- Les composes ameres subissent des transformations au cours du vieillissement de la biere qui se traduisent par une diminution sensorielle et analytique de l'intensite et de la qualite de l'amertume de la biere.
Au cours de la fabrication de la biere il y a coagulation de complexes proteines-polyphenols a partir du trouble. Ceux-ci sont produits comme trouble a chaud, a la fin de l'ebullition du mout et separes apres le refroidissement du mout avant la fermentation comme trouble a froid. L'elimination actuelle du trouble a chaud avec les dreches et le trouble a froid avec les eaux residuaires n'est pas judicieux vu la haute valeur physiologique alimentaire.- On a demontee que tout type de trouble pouvait etre seche sur un cylindre chauffant. Des melanges avec des levures excedentaires de la brasserie conduit a un produit facile a secher. Ce melange possede une composition voisine de celle d'une levure excedentaire sechee. Un trouble seche dans sa composition est avant tout domine par des constituants d'extrait sans azote, compose essentiellement par des glucides.- Les essais de nutrition effectues avec des produits secs ont donne des resultats positifs que l'on n'esperait pas de facon si accentuee. Malgre l'absence de resultats des proprietes physiologiques alimentaires au cours de ces essais sur le trouble seche, la question sur l'acceptabilite d'un melange amere de levures-troubles a ete prouvee de facon indiscutable a l'aide d'un essai de nutrition. Les craintes decrites dans la litterature concernant l'absorption du trouble par les animaux ont ete eliminees par cet essai.
In brewing practice it is of importance to know the particular stage of the cell cycle during which yeast generates trehalose under stress conditions as a protectant. Currently, there are no methods available (preferably on-line) to determine trehalose levels for process modelling and yeast propagation respectively. The aim of this investigation was to extend the physiological analysis spectra with a fast direct fluorescence optical detection for trehalose. A rise in temperature during the stage of exponential growth caused an immediate trehalose accumulation in the yeast cells, which has been detected by both HPLC and fluorescence optical analysis.
Within an experiment concerning the influence of barley and malt storage on their general quality and lipid oxidation in particular different spring and winter barley varieties of the crops 1999 and 2000 were processed. In addition to malting the barleys the produced malts were also used for brewing purposes. The flavour stability of the resulting beers was evaluated by a trained taste panel by comparing the fresh ones with those that were stored for four weeks at 28 degreesC. Five different raw material batches were analysed: Fresh barley and malt, barley and malt stored for six months and malt produced from barley which has been stored for six months. Three different beers have been produced using these five batches: Beer from fresh malt, beer from a half year stored malt and beer from malt which was produced from stored barley. It could be shown that there is only a slight influence of a suitable six month storage period of the raw materials on their standard parameters: Only the moisture content of the raw materials of all three batches increases slightly (respiration, hygroscopicity etc.) and the proteolysis of the malts produced from stored barleys was a little bit more intensive than that produced from the fresh ones. The flavour stability of the beers produced from stored raw materials was not found to be worse than that produced from fresh barley resp. malt although the amount of free and triglyceride-bonded hydroxy fatty acids, especially trihydroxy fatty acids (THOE), was noticeable influenced by the storage period. In particular the THOE of barley and malt could be a suitable marker for ageing processes on the base of lipid oxidation.
Within the scope of this assignment it could be shown that the chirale distribution of Linalool in aroma hops starting with raw hops up to all conventional hop products stays almost stable at 94 % R-Linalool. In beer considerably lower amounts of R-Linalool are found. A racemisation during the brewing process is thought to be the cause. Hereby the degree of racemisation obviously depends considerably on the type of hopping. In the course of beer staling racemisation continues with the overall amount of Linalool remaining constant. As a result a flavour loss is detectable also by organoleptic testing. A main factor for the transformation from (R)-Linalool into (S)-Linalool during beer staling may be the pH.- Bitter compounds undergo changes during beer staling that are reflected in an organoleptical and analytical decline of the intensity and quality of the beer bitterness.
There are many different possibilities to detect contaminants in beer. They are all based on a pre-accumulation of germs in/on selection media. Via micro- sieve technology a technique is presented where contaminants can be determined without pre-accumulation directly on a silicone sieve. Contaminants filtrated onto the micro sieve can be detected by both fluorescence optic and molecular biology (PCR-analysis). Thus, statements regarding functionality (viability) and identity are feasible.
The now available second part of a report related to the importance of deep bed filtration during kieselgur filtration deals with the impact of particle size distribution properties of different kieselguhr varieties on particle separation in the filter cake. For these purposes a beer sample with bimodal particle size distribution is filtered using different kieselgur varieties. Furthermore, kieselguhr samples are being modified regarding their particle size distribution by using upcurrent classifying and are also used in the filtration study. The analysis resulted in a high differentiation of particle size distribution of the samples. The poorly filterable beer shows a bimodal particle size distribution with two peaks in the range of 0.8 mum and approx. 6 mum. The well filterable beer shows a peak in the range of 6 mum (characteristic particle size of yeast cells). It can be shown that particles of different particle size can be separated from beer using different mechanisms of kieselguhr filtration: via surface filtration and via deep bed filtration. Particle size distribution and surface condition of kieselguhr impact the separation process. This study is a continuation of a joint project of the TU Bergakademie Freiberg with the Freiberger Brauhaus AG.
For the determination of original wort gravity within the range of 13 to 20 w/w-% there is among other things a well-known mathematical linear formula according to [2] with an accuracy of +/- 0,03 w/w-%. This formula can be used for the determination of original wort gravity within a range of 10 to 21 w/w-%, but with a reduced accuracy of +/- 0,1 w/w-% or by applying a simple correction to the formula of +/- 0,07 w/w-%. Through further adjustments of this mathematical formula according to [2] and via range containment it is possible to determine the original wort from the density d(20/4) over the density d(T) with an accuracy of less than +/- 0,01 w/w-% within the range of 10 to 18 w/w-%. Remarkably enough this does not involve complicated arithmetic operations, but rather the fact that this correlation can be described with linear functions.
Ever since it was known that Trichloroanisole can diffuse through plastic sealing of beverage packaging material, the problem of beverage contamination by volatile organic substances became obvious. Inadequate storage, combined with poor permeability of sealing material can cause the migration of undesirable substances into beverages. We developed a simple and precise method to determine the permeability of sealing material of crown corks, screw closures as well as PET bottles and their closures and of two-piece or multi-part can sealing of Naphthalene, as a substitute for other non-polar, organic substances. Serious differences concerning permeability were observed when testing several crown corks with different sealing. Plastic beer bottles also showed major differences in the permeability of Naphthalene.
The gelation of (1 --> 3)(1 --> 4)-beta-D-glucans in non-filtrated beer leads to a clogging of the filter media during the beer-brewing process and an increased filter media usage, reduces the beer output and increases the production costs. New investigations of the gelation mechanism show different types of gelation. A spontaneous gelation occurs independent of the molar above a critical glucan concentration (c = 1%) and follows an athermic kinetic with an at least two-dimensional seed growth. The formation of the gel seeds at suitable association points is much faster than the regular gelation. In general, the speed of gelation is controlled by the low molar mass fraction (M-w < 100 000 g/mol) of the glucan. A gel seed formation occurs also below the critical concentration of the spontaneous gelation. However, below the critical concentration of 1% an overall gelation of the solution with the formation of a solid gel particles is only possible for high molar mass fractions of the glucan (M-w > 100 000 g/mol) and an additional increase of the contact rate for example via shear forces. An analysis of the olygomeric composition of an enzymatic degradation of glucans allowed the formulation of a new gelation mechanism via regular cellotriose units along the glucan backbone in contrast to the widely assumed association via long cellulose-like units.
The determination of the flocculation behaviour of brewers' yeast represents an important part of brewery quality management, because alterations of this characteristic yeast property will directly influence the fermentation process, filterability of beer, and final beer quality. In this research work, three laboratory methods for measuring yeast flocculation were tested and evaluated. As a comparison, we simultaneously conducted fermentation trials in EBC-Fermentation Test Tubes and stainless steel CCTs. Both the determination of cell surface hydrophobicity according to Akiyama-Jibiki and the modified Helm's Test according to D'Hautcourt und Smart were practical and reliable methods, which therefore can be recommended. As a result of our findings, the modified Helm's Test according to Mota und Soares was less suitable because of its partly inaccurate results.
Different studies show, that fermentation in cylindro-conical fermentation tanks (ZKG) leads to low ester levels in beer. This can result in a one-sided flavour profile particularly in wheat beers, but also in Marzen and Festbier, in alcohol reduced beers and light beers. Fermentation experiments conducted in a bio reactor with varied parameters like sugar composition, pressure and convection showed that increased pressure reduces ester formation and thus, the tank heights has a great impact on ester formation. Studies in terms of sugar composition in wort suggest, that due to a maltose reduction ester levels increase in beer (6, 7, 8, 9). In fermentation experiments on a small scale (10 L) with bottom and top fermenting yeasts the ester level could be influenced by variation of the sugar ratio. In order to influence the sugar ratio Glucose/Maltose a special mashing procedure was developed which supports the maltase activity. This procedure is conform to the purity law, can be conducted in every brewery and is described in detail. Experiments on a pilot plant scale (60 L) with different barley and wheat malts have shown that the amount of ester in comparison to the "Hoch-Kurz-Maischverfahren" (high temperature, short time mashing process) can be increased 3-fold. An additional benefit of the new mashing procedure is the disintegration of beta-glucane.
Dans le cadre d'une serie d'essais pour examiner l'influence du stockage de l'orge et du malt on a transforme differentes varietes d'orges d'hiver et de printemps de la recolte de 1999. On a evalue la qualite generale de ces matieres premieres et en particulier l'oxydation lipidique. A cote d'un maltage on a effectue une fabrication de biere a partir des malts produits. Les bieres obtenues on ete soumises a un test de stabilite de flaveur grâce a d'une evaluation sensorielle en comparant la biere fraiche a une biere stockee pendant quatre semaines a 28 °C. Concernant les matieres premieres on a evalue cinq versements : orges fraiches, malts frais, orges et malts stockes pendant une demi-annee ainsi qu'un malt ou l'orge a ete stockee pendant une demi-annee. A partir des cinq versements on a obtenu trois sortes-differentes de bieres : biere a partir de malt frais, biere a partir d'un malt stocke pendant une demi-annee et biere produite a partir d'un malt ou l'orge a ete stockee pendant une demi annee. On a pu montrer que l'influence d'un stockage approprie de matieres premieres pendant une demi- annee etait faible dans le domaine des parametres standards : on a observe une legere augmentation de la teneur d'humidite des trois versements (respiration, hygroscopie) ainsi qu'une legere augmentation de la proteolyse sur les malts produits a partir d'orges stockees comparativement au malt fabrique a partir d'orges fraiches. La stabilite de flaveur des bieres produites a partir de matieres premieres stockees n'etait pas plus mauvaises que celle des bieres fabriquees a partir de matieres premieres fraiches. Toutefois la quantite d'acides gras libres et lies aux triglycerides, en particulier, les acides trihydroxyoctadeceniques (THOE) sont fortement influences pendant le stockage. En particulier les THOE dans l'orge et le malt peuvent servir de marqueur du vieillissement sur la base d'une oxydation lipidique.
La gelification des (1→3)(1→4)-β-D-glucanes presents dans la biere filtree conduit a la colmatation des dispositifs de filtration durant le brassage industriel de la biere. Ainsi les temps de filtrage sont reduits, la consommation de filtres est elevee, la production en biere est reduite et les couts de production sont eleves. De recentes etudes sur le mecanisme de gelification mettent en evidence deux differents types de gelification. La gelification spontanee se produit independamment de la masse molaire, au-dela d'une concentration critique de glucane (c = 1%) et suit une cinetique de formation athermique avec une croissance au moins bidimensionnelle de graines geliques. La formation de ces graines d'origine sur des locations appropriees du glucane est bien plus rapide qu'une cinetique de gelification homogene. La vitesse de gelification est, en general, controlee par les faibles masses moleculaires de glucane (M w 100 000 g/mol) et une augmentation additionnelle des contacts d'association (par exemple par l'apport de forces de cisaillement). Par ailleurs, la degradation enzymatique et l'analyse de la composition des polymeres ont permis de mettre en evidence que l'association des glucanes ne se produit pas, comme assume jusqu'ici, par l'intermediaire de longues sequences de type cellulose, mais par des sequences regulieres de blocs cellotrioses passant le long du squelette glucane.
One of the possibilities how to make beer production more effective is lowering the time of diacetyl and 2,3-pentanedione reduction. These compounds, collectively referred as vicinal diketones, are very important since their taste limits are very low and evolve undesirable change of beer flavour, which is known as buttery, cottage cheese or whey taste. The aim of our work was to study an influence of carbon dioxide pressure during the active carbohydrate fermentation and the end of fermentation on vicinal diketones reduction. We compared vicinal diketones reduction in young beers fermented under carbon dioxide pressure of 100 kPa during the whole main fermentation and in beers fermented without carbon dioxide pressure until extract concentration decreased to 7.5 degreesP and then under carbon dioxide pressure of 50 kPa. Experiments were done in the wort fermentation of gravity 12.5 degreesP and 13.5 degreesP. Lower carbon dioxide pressure accelerated vicinal diketones reduction and speeded up the end of fermentation. Wort concentration had no influence on vicinal diketones reduction in studied wort gravities (12.5 degreesP and 13.5 degreesP).
Low mashing-in temperature (37degreesC) and long duration of resting (60 min. including mashing-in) and long time of heating up to 63 degreesC leads to very high amount of FAN - up to 270 mg/l in 12 degrees P wort, but to very poor foam stability of beer produced (220 seconds in average) due to a low amount of high molecular proteins. When mashing-in temperature was higher (63 IQ the FAN concentrations of 12 degreesP wort was only 162 mg/l, but foam stability of beer was higher - 268 seconds in average. Mashing-in temperature of 50 degreesC leads to respectable FAN concentration. Yeasts utilised 104 mg/l of FAN in average using 13.5 degreesP wort with initial FAN concentration of 235 mg/l, 90 mg/l using 12.5 degreesP wort (initial FAN - 219 mg/l) and 87 mg/l using 10.5 degreesP wort (initial FAN - 197 mg/l). During maturation process any decrease of FAN was registered. FAN content was dropped due to blending of beer with deoxygenated water by automatic HGB system for desiderative resultant gravity. FAN content in finished product varied from 85 to 106 mg/l for 12 degreesP beer, and from 70 to 94 mg/l for loop.
Addition of hop products into a wort boiling process supplies colloidal, biological, organoleptic and foam stability as well as hop affects bitterness, aroma, colour and gushing. Nowadays hop pellets, extracts and pre-isomerised hop products are used. Using of pre-isomerized hops makes manipulation easier because of lower dosing and increases utilisation. Price level of the hops comparing with HHT hops is lower by one half in average and bitterness analytical results are reached on the same level. During measurement of bitter substances by BU method there were no differences in values, but isohumulones measurement shows that felt bitterness is higher, it is BU x 1,2. There was no influence neither on foam stability nor gushing creation. The negative taste properties were found during organoleptic tests; mainly in beers with higher hop content, tart and higher hoppy and ester taste was determined as negative taste properties.
