Yeast : the soul of beer’s aroma—a review of flavour-active esters and higher alcohols produced by the brewing yeast

Among the most important factors influencing beer quality is the presence of well-adjusted amounts of higher alcohols and esters. Thus, a heavy body of literature focuses on these substances and on the parameters influencing their production by the brewing yeast. Additionally, the complex metabolic pathways involved in their synthesis require special attention. More than a century of data, mainly in genetic and proteomic fields, has built up enough information to describe in detail each step in the pathway for the synthesis of higher alcohols and their esters, but there is still place for more. Higher alcohols are formed either by anabolism or catabolism (Ehrlich pathway) of amino acids. Esters are formed by enzymatic condensation of organic acids and alcohols. The current paper reviews the up-to-date knowledge in the pathways involving the synthesis of higher alcohols and esters by brewing yeasts. Fermentation parameters affecting yeast response during biosynthesis of these aromatic substances are also fully reviewed.Eduardo Pires gratefully acknowledges the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) for the PhD fellowship support (SFRH/BD/61777/2009). The financial contributions of the EU FP7 project Ecoefficient Biodegradable Composite Advanced Packaging (EcoBioCAP, grant agreement no. 265669) as well as of the Grant Agency of the Czech Republic (project GACR P503/12/1424) are also gratefully acknowledged. The authors thank the Ministry of Education, Youth and Sports of the Czech Republic (MSM 6046137305) for their financial support

Ca isotope fingerprints of early crust-mantle evolution

Among the most important factors influencing beer quality is the presence of well-adjusted amounts of higher alcohols and esters; as well as the successful reduction of undesirable by-products such as diacetyl. While higher alcohols and esters contribute rather positively to the beer aroma, diacetyl is mostly unwelcome for beer types with lighter taste. Thus, the complex metabolic pathways in yeast responsible for the synthesis of both pleasant and unpleasant by-products of fermentation were given special attention in this last chapter

Teacher Incompetence, Misconduct and Dismissal in British Columbia: An Archival Analysis (1962–1987)

The assessment of teacher competence and the administrative management of teacher performance are pressing issues of educational accountability. Much is claimed about the putative incompetence of teachers but little systematic data exist to document the extent of this alleged incompetence or to describe incidents of incompetence. This paper reports an archival study of such cases in British Columbia between 1962-1987 and compares these findings with an earlier study from the United States

Beach safety: Can drones provide a platform for sighting sharks?

CSIRO 2019 Open Access. Context: A series of unprovoked shark attacks on New South Wales (Australia) beaches between 2013 and 2015 triggered an investigation of new and emerging technologies for protecting bathers. Traditionally, bather protection has included several methods for shark capture, detection and/or deterrence but has often relied on environmentally damaging techniques. Heightened environmental awareness, including the important role of sharks in the marine ecosystem, demands new techniques for protection from shark attack. Recent advances in drone-related technologies have enabled the possibility of real-time shark detection and alerting. Aim: To determine the reliability of drones to detect shark analogues in the water across a range of environmental conditions experienced on New South Wales beaches. Methods: A standard multirotor drone (DJI Inspire 1) was used to detect shark analogues as a proxy during flights at 0900, 1200 and 1500 hours over a 3-week period. The 27 flights encompassed a range of environmental conditions, including wind speed (2-30.0 km h-1), turbidity (0.4-6.4 m), cloud cover (0-100%), glare (0-100%), seas (0.4-1.4 m), swells (1.4-2.5 m) and sea state (Beaufort Scale 1-5 Bf). Key results: Detection rates of the shark analogues over the 27 flights were significantly higher for the independent observer conducting post-flight video analysis (50%) than for the drone pilot (38%) (Wald P = 0.04). Water depth and turbidity significantly impaired detection of analogues (Wald P = 0.04). Specifically, at a set depth of 2 m below the water surface, very few analogues were seen by the observer or pilot when water turbidity reduced visibility to less than 1.5 m. Similarly, when water visibility was greater than 1.5 m, the detection rate was negatively related to water depth. Conclusions: The present study demonstrates that drones can fly under most environmental conditions and would be a cost-effective bather protection tool for a range of user groups. Implications: The most effective use of drones would occur during light winds and in shallow clear water. Although poor water visibility may restrict detection, sharks spend large amounts of time near the surface, therefore providing a practical tool for detection in most conditions

Physiological characterization of brewer's yeast in high-gravity beer fermentations with glucose or maltose syrups as adjuncts

High-gravity brewing, which can decrease production costs by increasing brewery yields, has become an attractive alternative to traditional brewing methods. However, as higher sugar concentration is required, the yeast is exposed to various stresses during fermentation. We evaluated the influence of high-gravity brewing on the fermentation performance of the brewer’s yeast under model brewing conditions. The lager brewer’s strain Weihenstephan 34/70 strain was characterized at three different gravities by adding either glucose or maltose syrups to the basic wort. We observed that increased gravity resulted in a lower specific growth rate, a longer lag phase before initiation of ethanol production, incomplete sugar utilization, and an increase in the concentrations of ethyl acetate and isoamyl acetate in the final beer. Increasing the gravity by adding maltose syrup as opposed to glucose syrup resulted in more balanced fermentation performance in terms of higher cell numbers, respectively, higher wort fermentability and a more favorable flavor profile of the final beer. Our study underlines the effects of the various stress factors on brewer’s yeast metabolism and the influence of the type of sugar syrups on the fermentation performance and the flavor profile of the final beer