The quantification of trace substances in raw materials, mash, wort and beer is becoming more frequently required by brewers. Stable isotope dilution assay (SIDA) coupled to gas chromatography mass spectrometry or liquid chromatography mass spectrometry instrumentation is a sensitive and highly specific technique for precise quantification of trace substances from complex matrices. The current paper elucidates the basic principles of stable isotope dilution assays and presents practical applications related to brewing. It emphasizes the importance of isotope standards in multi-step sample clean-up procedures and answers the question why SIDA is (so far) not widely used in brewery quality control.

BrewingScience - Monatsschrift für Brauwissenschaft, 64 (November/December 2011), pp. 140-150

It is generally recognized that flavour quality and flavour(in)stability cannot be grasped by one parameter, since the multitude of flavour chemicals involved. To identify beer chemistry changes during staling in commercial pilsner beer, an integrated analytical-sensorial methodology using multivariate statistical analysis was applied on samples subjected to ageing at 30 °C. Application of this technique to model the taste(in)stability in an objective way, offers the opportunity to more thoroughly investigate the influence of raw materials, brewing methods and applied technologies on flavour stability. The models obtained showed differences in aging behaviour of six commercial pale lager beers..

The Hop Storage Index (HSI) is used to describe the freshness of raw hops and hop pellets. The analysis is done by spectrophotometric methods as described in the Analytica-EBC 7.13 and ASBC Hops-12.

As in previous years we would like to demonstrate the variations in the contribution of hop oils to beer depending on the crop year. As a representative hop aroma substance we have chosen linalool, which correlates well with the sensory impression of a hoppy aroma in beer.

The Hopsteiner Guidelines 2011 will soon be published and be available at Brau Beviale 2011 in Nuremberg. We are still working on some details of the beer production and will present the balance of World Alpha Acid Supply and Demand as soon as possible.

Ozone can be widely used for oxidation of diverse water constituents and mineralization of organic compounds and therefore for their elimination in drinking and process water as explained before in the review Ozone I: Characteristics/Generation/Possible Applications by Heim C. and Glas K., BrewingScience 2011 [1]. Electrolytic ozone generation in situ using boron-doped diamond electrodes is a relatively new and promising technology. The current article describes the formation of ozone directly from water with a DIACHEM^® electrode. Ozone concentrations in water depend on the applied current on the one hand and on the water matrix on the other hand..

To derive differences between German pilsner beers which have effects on acceptance, sensory description is linked to consumer acceptance. The sensory perception of pilsner beer is described by sensorily-trained consumers. For the pilsner type of beer, an appropriate number of representative and characteristic attributes are compiled for the precise description of sensory perceptions. By investigating acceptance by untrained consumers (n=142) in blind and open product tests, estimations of pilsner beers are measured. The results can highlight promising pilsner varieties and identify those which are sensorily unconvincing. In addition, split analyses are performed concerning consumers’ objectives and sensory expectations.

The main quality challenge of beer is the change of its chemical composition during storage. It is known that the typical bitterness of fresh beer declines in the intensity and changes in the quality with an increasing age of the beverage. The bitter tasting compounds trans-iso-α-acids converse into lingering and harsh bitter tasting tri- and tetracyclic degradation products. In order to investigate the evaluation of beer flavour stability, the behaviour of trans-iso-α-acids, the trans/cis ratio of bitter acids, and the formation of tricyclocohumol and tricyclohumol as representatives of acidic-catalyzed degradation products of trans-iso-α-acids were chosen as analytical markers in wort, fresh beer as well as in 2 and 4 months aged beer samples with and without inline pre-isomerization. The characteristics of these analytical parameters were determined using HPLC-DAD and HPLC-MS/MS analysis. Supplementary to quantitative data, fresh beer as well as 2 and 4 months stored beer samples with or rather without the use of pre-isomerization were evaluated for the attributes aroma, taste, and beer ageing by a trained sensory panel.

In this paper, two non standard methods are introduced and described precisely for measuring the vitality of yeast. Both are simple and produce results in a very short time. For the purpose of demonstrating these methods, brewing yeasts were placed under specific types of stress in various situations and compared to yeast not under stress. Their capacity for producing CO₂ was measured, and the condition of their cell walls was determined parallel through potentiometric titration. The results show that both of the methods demonstrated in this paper are effective for determining the physiological condition of yeast. Also, the condition of their cell walls changed, which was made apparent by the volume titrant required in the potentiometric titration..

Holistic concept for water and recyclables recovery for the food industry in breweries – Part 1

Many industries focus on safeguarding specific physical-chemical properties in effluent water treatment and/or processing. In the food and beverage industry, hygiene and psychological aspects also play a role as consumers disapprove of “mixing” effluent water and food. In this article, strategies for water and recyclables recovery suitable for breweries are proposed. In part 1, pollution arising in brewery effluent water is described and various strategies for water recovery are presented. Part 2 discusses end-of-pipe treatment of effluent water using a combination of biological and membrane processes. Together with possibilities of utilising spent grains, a possible holistic concept is presented.

Quality control begins with yeast culturing

Consistency in beer quality is dependent on many factors. In addition to water, malt and hops, brewing yeast is an essential raw material and plays an important role in successfully producing beers of premium quality. The Weihenstephan Research Center for Brewing and Food Quality at Technische Universität München has developed a comprehensive quality control program for the culturing and propagation of brewing yeast, which fulfills the stringent demands placed on their pure yeast cultures by brewers.