The quantitative determination and some values of dimethyl sulphide in white table wines

A gaschromatographic headspace method has been developed for the quantitative determination of dimethyl sulphide (DMS) in wines. The standard deviation of the method was in the order of 6%.Application of the method to the analysis of several white wines showed DMS values which varied from O to over 400 µg/1. From analytical data it appeared that DMS developed in the bottle and could as such possibly contribute to bottle bouquet. It was found that maturecl Riesling wines had particularly high concentrations of DMS.Die quantitative Bestimmung von Dimethylsulfid in weißen Tafelweinen sowieeinige Angaben über seine KonzentrationFür die quantitative Bestimmung von Dimethylsulfid (DMS) in Wein wurde unter Verwendung der „headspace"-Technik und von Dichlormethan als Standard eine gaschromatographische Methode entwickelt. Die Genauigkeit der Methode liegt bei einer Standardabweichung von 6%. Bei der Anwendung der Methode auf eine Reihe von Weißweinen wurden DMS-Werte zwischen O und über 400 µg/l ermittelt. DMS scheint sich während der Ausreifung des Weines in der Flasche zu entwickeln und könnte zum sogenannten Lagerungsbukett beitragen. Besonders hohe DMS-Konzentrationen wurden in älteren Riesling-Weinen festgestellt

Factors affecting the reproducibility of fermentation of grape juice and of the aroma composition of wines 1. Grape maturity, sugar, inoculum concentration, aeration, juice turbidity and ergosterol

Gas chromatographic analysis was used for the investigation of some factors which determine the production of volatile wine components during fermentation. Especially the effect of "heterogenous" juice factors such as turbidity and air content were investigated in respect of fermentation rate and the production of fatty acids, fusel alcohols and esters. lt was shown that the fermentation lag of clear filtered and de-aerated grape juices could be prevented by small ergosterol additions before inoculation. A marked similarity was observed in the chromatograms of wines from fermentations of clear juices which were stimulated either by air or by ergosterol. Grape maturity proved to be a major factor affecting the production of volatile acids, alcohols and esters during fermentation. Fermentations of de-aerated and clear filtered juice with an addition of 0.5 g bentonite/l yielded wines with the best scores an sensory evaluation.Maßgebliche Faktoren für die Reproduzierbarkeit der Vergärung von Traubenmostund die Aromazusammensetzung von WeinI. Traubenreife, Zucker, Konzentration des lnokulums, Luft, Klarheit des Mostesund ErgosterinEinige Faktoren, welche die Bildung flüchtiger Weininhaltsstoffe bei der Gärung beeinflussen, wurden gaschromatographisch untersucht. Besonders die Wirkung „heterogener" Faktoren im Traubenmost, wie zum Beispiel Trübung und Luftgehalt, auf die Gärungsgeschwindigkeit und die Bildung von Fettsäuren, Fuselalkoholen und Estern wurde untersucht. Es wurde gezeigt, daß die Gärungsverzögerung bei klarfiltrierten und entlüfteten Traubensäften durch die Zufügung kleiner Mengen von Ergosterin vor der Inokulation verhindert werden kann. Wurde die Gärung von geklärtem Most durch Luft oder durch Ergosterin angeregt, so zeigten die Chromatogramme der Weine eine starke Ähnlichkeit. Die Traubenreife erwies sich als der wichtigste Faktor, der die Bildung von flüchtigen Säuren, Alkoholen und Estern bei der Gärung beeinflußt. Die Vergärung von entlüftetem und klarfiltriertem Most mit Zusatz von 0,5 g Bentonit/l ergab Weine, die bei der Weinprobe die höchsten Punktezahlen erhielten

Assessing a portable, real-time display handheld meter with UV-A and UV-B sensors for potential application in personal sun exposure studies

BACKGROUND : Observing accurate real-time measurements of solar ultraviolet radiation (UVR) levels is important since personal excess sun exposure is associated with skin cancers. Handheld measurement devices may be helpful but their accuracy is unknown. We compare a portable, science-grade solar UVR monitoring device against two fixed, science-grade solar UVR instruments. METHODS : Instruments were (1) a fixed Solar Light 501 UV-B biometer to measure UV-B; (2) a fixed Kipp and Zonen radiometer used to measure UV-A and UV-B; and (3) Goldilux ultraviolet probes which are commercially available portable devices. Two different probes were used, one measured UV-A and the other UV-B radiation. The Goldilux probes were levelled and secured next to the UV-B biometer. Between 10:00 and 14:40 UTC+2, the UV-B biometer was set to record at 10-minute intervals and measurements by the Goldilux probes were manually taken simultaneously. Results were compared for all data and by solar zenith angle (SZA) ranges. RESULTS : The Goldilux UV-B probe measured UV-B relatively well in its diurnal pattern, however, its readings were ~77% higher than those made by the UV-B biometer. While UV-A measurements from the Goldilux UV-A probe and those from the radiometer were in relatively good agreement in pattern, the radiometer read ~47% higher than the Goldilux UV-A probe. UV-B data from Goldilux UV-B probe had a moderately strong correlation with UV-B biometer data for small SZAs; conversely, for UV-A, the Goldilux UV-A probe had a strong correlation with the UV-A radiometer data for large SZAs. CONCLUSION : Handheld devices may be useful to provide real-time readings of solar UVR patterns, however, to achieve synchronicity in the magnitude of readings to those made by science-grade fixed instruments, devices may need to be used during certain times of the day and in clear-sky conditions which may not be practical in personal exposure studies.Dr Wright receives funding support from the South African Medical Research Council and the National Research Foundation of South Africa.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-08462019-11-01hj2019Geography, Geoinformatics and Meteorolog

Classification of White Cultivar Wines by Origin using Volatile Aroma Components

Stepwise discriminant analysis was applied to gas chromatographic data of some volatile compounds obtmiieabjiTreonextracliOii"of dry white table wines. By means of this statistical method, successful classifications according to origin of Colombar wines from two regions, and Chenin blanc wines from three regions, were obtained. The components with the highest discriminatory value were i-amyl acetate, hexyl acetate and i-butanol, in the case of the Colombar wines and hexanol and 2-phenyl ethanol in the case of the Chenin blanc wines

Differentiation between Wines Originating from Different Red Wine Cultivars and Wine Regions by the Application of Stepwise Discriminant Analysis to Gas Chromatographic Data

Stepwise discriminant analysis (SDA) was applied to gas chromatographic data of some volatile compounds extracted with freon from red wines. By means of this statistical method, Pinotage and Cabernet Sauvignon wines (1978 vintage) could be classified into separate groups, the most effective variables being hexanol and i-amyl acetate. Pinotage wines from three, and Cabernet Sauvignon wines from two localities (1979 vintage) were subjected to classification according to origin. Successful classifications were obtained using the variables ethyl acetate, ethyl caprate, i-amyl acetate as well as a compound tentatively identified as i-valeric acid

Objective quality rating of Pinotage wine

Relationships between wine composition and three quality parameters were investigated employing a linear multiple regression statistical model. For this purpose a least squares curve fitting computer programme was applied to analyses of 17 Pinotage wines for 6 fatty add esters. Overall quality, taste and aroma ratings were determined by a taste panel and utilized as dependent variables. lt was found that 2 esters viz. n-hexylacetate and ethyl-n-octanoate allowed excellent prediction equations to be set up for the quality ratings when incorporated into multiple regression equations.Objektive Beurteilung der Weinqualität bei der Sorte PinotageDie Beziehungen zwischen der Weinzusammensetzung und drei Parametern der Weinqualität wurden untersucht, wobei das statistische Modell einer mehrfachen linearen Regression verwendet wurde. Zu diesem Zweck wurden die bei 17 Weinen der Sorte Pinotage gewonnenen Analysenergebnisse über 6 Fettsäureester in ein Computerprogramm zur optimalen Kurvenanpassung eingegeben. Durch ein Gutachtergremium wurden die Gesamt-Weinqualität, der Geschmack und der Geruch bewertet; die Daten dieser Qualitätsbeurteilung wurden als abhängige Veränderliche benützt. Es wurde festgestellt, daß 2 Ester, nämlich n-Hexylacetat und Äthyl-n-octanoat eine ausgezeichnete Vorhersage der Weinqualität ermöglichten, wenn ihre Werte in Mehrfachregressions-Gleichungen eingesetzt wurden

The use of confocal microscopy in quantifying changes in membrane potential

Monitoring the plasma membrane potential and its changes can be a time consuming and challenging task especially when conventional electrophysiological techniques are used. The use of potentiometricfluorophores, namely tetramethylrhodamine methylester (TMRM), and digital imaging devices (laser scanning confocal microscopy) provides reliable and time efficient method. Two scorpion pore-forming peptides, namely PP and OP1, were used as a tool to induce depolarization of the plasma membrane potential of neuroblastoma cell line and cardiac myocytes. Alternative methods for the neuroblastoma cells and cardiac myocytes were used. Depolarization of the neuroblastoma cells was calibrated with 140 mM KCl solution with 1 ìM valinomycin, after which intensity readers were substituted in the Nernst equation for quantification. Calibration of the alternative method used of the cardiac myocytes’ plasma membrane potential changes was calibrated with the use of 5, 20, 40, and 80 mM KCl solutions with 1 ìM valinomycin. A calibration curve was then constructed from which plasma membrane potential could be calculate

Making A Difference: Year Two Report of the Pennsylvania High School Coaching Initiative

This report examines the implementation of the second year of three for the Pennsylvania High School Coaching Initiative (PAHSCI). Funded by the Annenberg Foundation, this initiative focuses on literacy and math coaches providing support to teachers from across the major subject areas to create literacy-rich classrooms in which students actively engage in learning tasks that deepen their content knowledge and strengthen their abilities to think critically and communicate well. This report presents findings from the first two years of research. It includes survey research as well as in-depth qualitative research in participating schools and districts and provides recommendations for PAHSCI stakeholders as they refine the program and for other education reformers as they consider the benefits of instructional coaching as a strategy for improving high schools and student achievement