Evaluation of the Nietvoorbi j Wine Score Card and Experimental Wine Panelists Utilizing Pattern Recognition Techniques

Principal component analysis (PCA) was applied to four cultivar wines, submitted repetitively amongst more than 450 experimental wines, to a sensory evaluation panel of 18 members who used a scoring system comprising overall wine quality and 11 wine descriptors. Inconsistent judges could be eliminated by the evaluation of scatter diagrams. After eliminating 11 judges, the scores of the remaining 7 were used to evaluate the score card in terms of weights placed on individual descriptors in a multiple regression equation, which related the 11 parameters to overall quality scores. Deviations from actual score card weights are discussed in terms of previous PCA analyses, and it is argued that both cultivar and the composition of a mixed data set with respect to these factors, could affect the relative importance of certain parameters. Fitting a similar equation to a large data set consisting of about 480 wines, comprising 23 different cultivars, confirmed the need for further investigations concerning relative score card weights, as well as a critical evaluation of score card parameters for evaluating widely diverging experimental wines

The Effect of Fermentation Time (as Induced by Fermentation and Must Conditions) on the Chemical Profile and Quality of a Chenin blanc Wine

Pattern recognition and simple factorial analyses were applied to chemical profiles determined on wines resulting from an experiment in which the effect of grape solids, assimilable nitrogen, bentonite and fermentation temperaturelevels as well as culture aeration on total fermentation time was investigated. It was found that fermentation times of the untreated Chenin blanc must could be shortened considerably by increasing grape solid levels and/ or nitrogen as well as temperature. However, it was established that the speeding up of fermentation at sub-optimal assimilable nitrogen levels leads to wines relatively high in higher alcohols and low in esters

Grape Maturity and Wine Quality

Several indices calculated from grape juice analyses were submitted to statistical analyses in order to determine correlations of these indices with quality of wine made from grapes at different stages of maturity. Curvilinear relationships were obtained enabling an optimum point to be calculated relating grape maturity to maximum wine quality. The application of skin contact in the case of white wine cultivars resulted in earlier maxima for wine quality, thus compensating to an extent for earlier harvesting. The cultivars Chenin blanc, Colombar, Pinotage and Cabernet Sauvignon were examined as outlined above over several years

Chenin blanc Wine Volatiles and the Intensity of a Guava-like Flavour

A guava-like flavour occurring in some South African Chenin blanc and Colombard dry white wines was investigated. Headspace volatiles of some of these wines, as well as those of fresh guava fruits, were analysed by means of a gas chromatograph equipped with a "sniffer-detector". In contrast to the headspace concentrate of guava fruits, no single fraction with a typical guava flavour was found in the wines analysed. The pattern recognition system "ARTHUR" was therefore used to investigate relationships between the more important wine volatiles and the intensity of a guava-like flavour of a set of wines originating from the same Chenin blanc must. Sensory scores for this flavour were used in both category and continuous property analysis in each case. Category and correlation to property plots were used to elucidate the results. Several promising variables and ratios between variables were singled out for further investigation, notably ethyl butyrate and the ratios ethyl butyrate/ethyl decanoate and ethyl butyrate/ethyl octanoate

Interactions between Grape Maturity Indices and the Quality and Composition of Chenin blanc and Colom bar Wines from Different Localities

Three grape maturity indices viz. degrees Balling (0 B), total titratable acidity (TT A) and the 0 B.pH product of musts were compared regarding their ability to predict optimum quality for Chenin blanc and Colombar wines. Comprehensive analytical data from 168 musts and corresponding wines for the 1978, 1979 and 1980 vintages from the Stellenbosch, Robertson and Lutzville areas were accumulated, and subjected to principal component analysis using variables and variable ratios selected by correlation to quality weighting. These results indicated that the two cultivars differed appreciably with respect to the value of all three measured indices. From this study it was not possible to select a specific index to predict optimum maturity in all cases. Optimum values for each index differed according to geographic locality

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

Allergic sensitisation in South Africa: Exploring regional variation in sensitisation

Background. Allergy is a common health problem in South Africa (SA), and a rational approach to allergy testing is essential to ensure cost-effective as well as optimal patient diagnosis and management.Objectives. To review allergy testing data with respect to current national testing recommendations, and to explore the regional variations in sensitisation.Methods. Retrospective data review on allergy testing from a private pathology provider in SA over a 2-year period. Data on skin-prick testing (SPT) and allergen-specific IgE testing originating from all the provinces of SA were collected and analysed with regards to allergen positivity rate and regional sensitisation patterns.Results. Among the patients (N=45 0320) tested for a suspected inhalant allergy, 46% tested positive. Only 45% of these received additional testing for the nine recommended inhalant allergens included in the current national testing protocol. Among the patients (N=6 775) who received SPT for a suspected inhalant allergy, 59% yielded one or more positive results. The most frequent sensitising allergens were house dust mite (Dermatophagoides pteronyssinus) and grass pollen. The house dust mite, Blomia tropicalis, was a significant sensitiser in coastal regions. SPT identified two other important regional allergens which are not included in the current recommendations for inhalant allergen-specific IgE testing.Conclusions. The current diagnostic recommendations include allergens that demonstrate significant sensitisation in all regions of SA. Two additional allergens that show significant regional sensitisation in the South African population were identified. These findings may aid the recommendations for the most appropriate and cost-effective approach to allergy testing of symptomatic patients in SA