Browsing by Author "Iipinge, Hilaria"

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    Oenological evaluation of Chenin Blanc wines elaborated from different trellising systems
    (Stellenbosch : Stellenbosch University, 2019-12) Iipinge, Hilaria; Buica, Astrid; Panzeri, Valeria; Stellenbosch University. Faculty of Agrisciences. Dept. of Viticulture and Oenology.
    ENGLISH ABSTRACT: Grape composition plays a significant role in defining wine style and typicality; and there are ways in which grape composition can be altered or modified. Among these ways are viticultural practices which include trellising systems. Trellising systems are driving mechanisms that alter canopy microclimates, consequently affecting yield and the quality of grapes. Due to the fact that most grape primary metabolites contribute to the production of secondary compounds in final wines, it is important to assess if changes in canopy microclimates induced by trellising systems can reflect in final wines. Therefore, the aim of this study was to characterise (chemically and sensorially) grape must and wines of Chenin Blanc grapes made from grapes of different trellising systems. Basic oenological parameters (including Brix, pH, TA and alcohol) were measured for grape juice from harvest and then throughout the winemaking process. Sugar level varied in the first season with a significant difference between systems, but no significant differences were observed in other parameters. The other important factor evaluated was yield, which had differences between systems; mostly, open canopies by horizontal division produced higher yield than vertical dividing canopies and closed non-dividing canopy systems. However, those differences were not statistically significant between systems. YAN, ammonia, total (FAN) and individual amino acids in musts and major volatiles and thiols were subsequently measured. The concentrations were above critical levels for YAN. No significant differences were found across all the treatments, when the data were subjected to analysis of variance, and even by multivariate analysis no distinctive groupings were formed. However, the additional fingerprint of wine samples by high-resolution mass spectrometry produced groupings of samples according to trellising systems. In Chapter 3, the wines of the six different trellising systems were profiled using a rapid descriptive method (CATA), using both analytical and expert panellists; further, wine overall quality was evaluated by experts. Wine samples could not be differentiated by aroma according to trellising systems. On the other hand, taste and mouthfeel profiles implied that there were differences between wine samples according to trellising systems. Additionally, the overall wine quality rating showed significant differences between wines of according to trellising systems, mostly contributed by significant differences in taste and aroma ratings. In Chapter 4, a detailed discussion of results from Chapters 2 and 3 is presented by comparing sensory profiles with chemical composition by correspondence analysis and principal component analysis respectively. Aroma compounds showed no significant differences between trellising systems (Chapter 2). Aroma description profiles from the correspondence analysis (CA) biplot (Chapter 3), illustrated that aroma profiles of the wines were similar since no clear groupings observed., The CA score plot from taste and mouthfeel results produced a similar configuration pattern with the PCA score plot from the high resolution mass spectrometry (HRMS) data, which indicated that the trellis system may have an influence on chemical aspects also related to the wines’ taste perception. The results of this research contribute to information that winemakers or growers may require regarding decisions they can make in relation to choosing an appropriate trellising systems. However, other factors such as cultivar, climate, vintage, and economic advantage should not be disregarded.