Precision of a Small Brew House by Determining the Repeatability of Different Brews to Guarantee the Product Stability of the Beer

The most important success factors of a brewery are to brew a high-standard beer and to sell this product successfully on the market. Especially, guaranteeing an objective product quality is a difficult task, in terms of beer quality, for craft brewers. Following these product stability parameters is not only necessary to secure the expiry date but also with regard to the repeatability of the brews (from batch to batch). To evaluate the precision of a small brew house (1 hL), three different beer types, lager beer (Pilsener), pale ale (Kölsch), and wheat beer (Weißbier) were repeatedly produced and analyzed. It was found that small fluctuations in the wort preparation, in terms of time or analysis, have no noticeable difference on the sensory characteristics of the final product. Nevertheless, strict adherence to the brew recipe and raw material monitoring are necessary in order to keep these deviations as minimal as possible. Finally, this study verified that microbrews can be repeated so that the consumers will not detect any differences with their five senses in the end

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

Interaction of proteins and amino acids with iso-α-acids during wort preparation in the brewhouse

This paper investigates the binding behavior of iso-α-acids from hops on free wort amino acids and proteins concerning the wort production process in breweries. The studies were carried out with different amino acids, bovine serum albumin and wort. To identify the nature of reaction between iso-α-acids and these substances, analyses of free amino nitrogen, HPLC and isothermal titration calorimetry were performed. According to the results, the iso-α-acids do not form covalent bonds with free amino acids of wort. However, iso-α-acids, especially isohumulone and isoadhumulone, form ionic bonds with wort proteins. A distinction must be made between proteins that are present in the hot trub, and those that are still dissolved in the hot wort. Proteins that are already coagulated and precipitated no longer react with iso-α-acids. Future experiments will investigate whether the established ionic bonds between iso-α-acids and proteins from the wort preparation process are maintained during fermentation until the finished beer or beer foam. If this is the case, which is induced by the experiments, there is a measurable loss of iso-α-acids in the hot wort, but at the same time, a gain for the later beer foam retention, as the iso-α-acids will stabilize it.TU Berlin, Open-Access-Mittel – 202

Measuring physical activity-related environmental factors: reliability and predictive validity of the European environmental questionnaire ALPHA

BACKGROUND: A questionnaire to assess physical activity related environmental factors in the European population (a 49-item and an 11-item version) was created as part of the framework of the EU-funded project "Instruments for Assessing Levels of PHysical Activity and fitness (ALPHA)". This paper reports on the development and assessment of the questionnaire's test-retest stability, predictive validity, and applicability to European adults. METHODS: The first pilot test was conducted in Belgium, France and the UK. In total 190 adults completed both forms of the ALPHA questionnaire twice with a one-week interval. Physical activity was concurrently measured (i) by administration of the long version of the International Physical Activity Questionnaire (IPAQ) by interview and (ii) by accelerometry (Actigraph device). After adaptations, the second field test took place in Belgium, the UK and Austria; 166 adults completed the adapted questionnaire at two time points, with minimum one-week interval. In both field studies intraclass correlation coefficients (ICC) and proportion of agreement were computed to assess the stability of the two test scores. Predictive validity was examined in the first field test by correlating the results of the questionnaires with physical activity data from accelerometry and long IPAQ-last 7 days. RESULTS: The reliability scores of the ALPHA questionnaire were moderate-to good in the first field testing (ICC range 0.66 - 0.86) and good in the second field testing (ICC range 0.71 - 0.87). The proportion of agreement for the ALPHA short increased significantly from the first (range 50 - 83%) to the second field testing (range 85 - 95%). Environmental scales from both versions of the ALPHA questionnaire were significantly associated with self-reported minutes of transport-related walking, and objectively measured low intensity physical activity levels, particularly in women. Both versions were easily administered with an average completion time of six minutes for the 49-item version and less than two minutes for the short version. CONCLUSION: The ALPHA questionnaire is an instrument to measure environmental perceptions in relation to physical activity. It appears to have good reliability and predictive validity. The questionnaire is now available to other researchers to investigate its usefulness and applicability across Europe

Theoretical and practical aspects in the application of the charge titration method for a faster prediction of the colloidal stability of bottom fermented beers

Das Sicherstellen einer konstanten Bierqualität zählt heutzutage zu den größten Herausforderungen der Brauindustrie. Als wesentlicher Stabilitätsparameter definiert sich die chemisch-physikalische Stabilität als Resistenz filtrierter Biere gegenüber Trübungsneigung. Um den Zeitpunkt sichtbarer Trübung im Bier vorherzusagen, wurde die Bestimmung von Partikeloberflächenladungen mittels titrimetrischer Analyse angewandt (Ladungstitration). Im Zuge der Erarbeitung theoretischer, kolloidchemischer Grundlagen zur Partikelanalytik konnte erstmals ein vollständiger Aufbau der elektrischen Doppelschicht durch die Kombination unterschiedlicher Theorien beschrieben werden. Weiter wurde die praktische Umsetzung der Anwendung der Ladungstitrationsmethode zur Analyse der Bierstabilität auf ihre Einflussgrößen evaluiert. Anhand unterschiedlich stabilisierter Biere konnte deren Anwendbarkeit zur Beurteilung der kolloidalen Bierstabilität demonstriert werden. Dabei wurde erstmalig auch das Signal der Potentialstärke quantitativ einbezogen. Letztlich war über die Formulierung eines Stabilitätswerts die Vorhersage der Trübungsstabilität bereits im frisch abgefüllten Bier möglich.Assuring a constant beer quality is one of the biggest challenges in the brewing industry. One important parameter is the physico-chemical stability of the product. This is the resistance of filtered beer against haze formation. To predict the time until haze gets visible, determination of the particle surface charge with titrimetric analysis was performed (charge titration method). In the course of theoretical colloid chemical basics for the particle analysis, a complete description of the electric double layer could be given by combining different theories for the first time. The practical implementation of the charge titration method for analyzing the beer stability was evaluated on the influencing factors. With the help of differently stabilized beers, estimated colloidal stability could be demonstrated. For the first time, the signal of the potential was interpreted quantitatively. Finally, with the formulation of a stability factor a prediction of haze formation in the fresh bottled beer was possible

Usability and technological opportunities for a higher isomerization rate of -acids: A review

Hops are an essential raw material for beer production in the brewery. The hop constituents give the beer its bitter taste, additional aroma, and can make it more stable. As hops are a cost-intensive ingredient, the bitter substance yield plays a major role for breweries. Various approaches are available to increase hop utilization in brewhouses. They range from pre-isomerized hop products or catalysts, which are only utilized outside the German Beer Purity Law, to different procedures, as well as novel brewhouse and dosing equipment. Examples include changes in the mashing process, pre-isomerization systems, or fractional wort boiling

Dynamics of the Driving Force During the Normal Vocal Fold Vibration Cycle.

Intraglottal pressure is the driving force of vocal fold vibration. Theoretically, simultaneous quantification of glottal area and transglottal airflow allows the calculation of the intraglottal pressure waveform during a single vibration cycle. In this study, we show that, by combining photoglottography (transglottal light transmission) and airflow (Rothenberg mask) measurements during sustained vocal emissions in vivo, the intraglottal pressure wave can be approximated in a way similar to what has been done in models. The results confirm in vivo that the intraglottal pressure is systematically larger during the opening phase than during the closing phase, so that over one whole cycle, the driving force performs net positive work, accounting for sustained vocal fold motion. A component of this driving force asymmetry is related to vocal tract inertance, which also accounts for the skewing of the airflow waveform compared with the area waveform. Furthermore, the intraglottal pressure ratio (opening:closing) increases with voicing intensity, reaches a maximum around 76 dB, and significantly decreases at higher intensities. This rise and fall suggests that there is a range of intensity values in which, mechanically, a maximum of the driving force is imparted to the vocal fold mass. This finding could have implications for voice economy in professional speakers