Browsing by Author "Naes, T."

Now showing 1 - 6 of 6
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    Characterization of selected South African young cultivar wines using FTMIR Spectroscopy, Gas chromatography, and multivariate data analysis
    (2009) Louw, L.; Roux, K.; Tredoux, A.; Tomic, O.; Naes, T.; Nieuwoudt, Helene; Van Rensburg, P.
    The powerful combination of analytical chemistry and chemometrics and its application to wine analysis provide a way to gain knowledge and insight into the inherent chemical composition of wine and to objectively distinguish between wines. Extensive research programs are focused on the chemical characterization of wine to establish industry benchmarks and authentication systems. The aim of this study was to investigate the volatile composition and mid-infrared spectroscopic profiles of South African young cultivar wines with chemometrics to identify compositional trends and to distinguish between the different cultivars. Data were generated by gas chromatography and FTMIR spectroscopy and investigated by using analysis of variance (ANOVA), principal component analysis (PCA), and linear discriminant analysis (LDA). Significant differences were found in the volatile composition of the cultivar wines, with marked similarities in the composition of Pinotage wines and white wines, specifically for 2-phenylethanol, butyric acid, ethyl acetate, isoamyl acetate, isoamyl alcohol, and isobutyric acid. Of the 26 compounds that were analyzed, 14 had odor activity values of > 1. The volatile composition and FTMIR spectra both contributed to the differentiation between the cultivar wines. The best discrimination model between the white wines was based on FTMIR spectra (98.3% correct classification), whereas a combination of spectra and volatile compounds (86.8% correct classification) was best to discriminate between the red wine cultivars. © 2009 American Chemical Society.
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    Fermentation-derived aroma compounds in varietal young wines from South Africa
    (SASEV, 2010-09) Louw, L.; Tredoux, A. G. J.; Van Rensburg, P.; Kidd, M.; Naes, T.; Nieuwoudt, Helene
    The volatile composition of 925 single cultivar young Sauvignon blanc, Chardonnay, Pinotage, Merlot, Shiraz and Cabernet Sauvignon wines of vintages 2005 to 2007, was determined using gas chromatography-flame ionisation detection. Compositional data were compared to published data on young wines from South Africa and other countries. South African young wines analysed in this study had a largely similar volatile composition to that reported in the literature. Significant between-vintage and between-cultivar differences were observed in the volatile composition of the wines investigated in this study. The concentration ranges of four compounds in red wines, hexanol, propanol, diethyl succinate and ethyl lactate, and four compounds in white wines, 2-phenylethanol, hexanoic acid, isoamyl acetate and propanol, were not influenced by vintage effects. This finding was interpreted as the first indication that typical concentration ranges for some aroma compounds can be established for South African young cultivar wines. A trend was observed in the white wines that the alcohols and their respective acetate esters, as well as fatty acids and their ethyl esters, were responsible for the vintage-related effects. Differences in volatile composition between Chardonnay and Sauvignon blanc wines could also largely be explained on the same basis. Classification models were established to discriminate between individual red wine cultivars and between the two white wine cultivars and correct classification rates of respectively, 79 % and 85 % were achieved.
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    Functional wine-omics.
    (2008) Bauer, Florian; Naes, T.; Esbensen, K. H.; Young, P. R.; Du Toit, M.; Vivier, M. A.
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    Sorting in combination with quality scoring : a tool for industry professionals to identify drivers of wine quality rapidly
    (South African Society for Enology and Viticulture, 2018) Brand, J.; Kidd, M.; Van Antwerpen, L.; Valentin, D.; Naes, T.; Nieuwoudt, Helene
    Quality plays an important role in the criteria directing wine product development. The evaluation of sensory characteristics associated with wine quality, as perceived by industry professionals, is therefore important. We investigated the suitability of the free-sorting sensory evaluation method, in combination with wine quality scoring using a 20-point scoring system, to determine the drivers of quality. Eight commercial South African Sauvignon blanc wines were assessed by a panel of 24 wine industry professionals. Free sorting with a verbalisation step to describe the groups, followed by quality scoring using score sheets routinely used in the wine industry, was performed. A multivariate sensory map was constructed using DISTATIS to explain the similarities and differences amongst the set of wines. Correspondence analysis (CA) was applied to the group descriptors, and CA deviates were calculated. Pearson’s correlation coefficients between CA deviates and the quality scores were calculated to identify the drivers of quality. Significant differences in quality were observed between the wines. The sensory attributes “passion fruit”, “green pepper”, “peas”, “asparagus” and “green” were frequently cited by the panel for the wines that received the highest average quality scores, and these attributes were identified as drivers of quality. In this study, a procedure is presented that combines sorting and quality scoring to investigate the relationship between sensory attributes and quality scores to identify the drivers of wine quality. Industry professionals and research environments can use this procedure to determine drivers of wine quality in a single evaluation session.
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    The relationships between consumer liking, sensory and chemical attributes of Vitis venifera L. cv. Pinotage wines elaborated with different Oenococcus oeni starter cultures
    (JOHN WILEY & SONS LTD, THE ATRIUM, SOUTHERN GATE, CHICHESTER, ENGLAND, WSUSSEX, PO19 8SQ, 2013) Malherbe, S.; Menichelli, E.; Du Toit, M.; Tredoux, A. G. J.; Muller, M.; Naes, T.; Nieuwoudt, Helene
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    Validation of two Napping techniques as rapid sensory screening tools for high alcohol products.
    (ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND,OXON, OX5 1GB, 2013) Louw, L.; Malherbe, S.; Naes, T.; Lambrechts, M. G.; Van Rensburg, P.; Nieuwoudt, Helene