Brock KUHLMAN1 Bodil JØRGENSEN2, José L. ALEIXANDRE TUDO3,1, Wessel DU TOIT4, John P. MOORE1
1South African Grape and Wine Research Institute, Stellenbosch University, Stellenbosch, South Africa
2Plant Glycobiology, Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
3Universitat Politecnica de Valencia, Instituto de Ingenieria de Alimentos para el Desarrollo (IIAD), Departamento de Tecnología de Alimentos
4Department of Viticulture and Oenology, Stellenbosch University, Stellenbosch, South Africa
Email contact: brock[@]sun.ac.za
AIM: To determine the effect of both ripeness and enzyme maceration on the astringency and bitterness perception of Cabernet Sauvignon wines
Recent work has contributed to a more detailed understanding of the grape cell wall deconstruction process from ripening through crushing and fermentation, providing a better understanding of what role polysaccharides play in post-harvest fermentation of grapes(1,2). Current research on glycomics in red wine making suggest polysaccharides are important sensory impact molecules (3–6).
METHODS: Our experimental system harvests Cabernet Sauvignon grapes at three different ripeness levels and makes wine both with and without enzyme treatment. Using glycan-array technology (Comprehensive Microarray Polymer Profiling – CoMPP) as an analytical tool, we explore comparative levels of polysaccharides derived from cell walls that pass through the fermentation process to wines. These results are confirmed using GC-MS analysis of hydrolyzed polysaccharides, in addition to analysis of extracted tannins and polyphenols. Wines are submitted for sensory analysis to test astringency and bitterness perception after alcohol level equalization, providing a novel look at emzyme macerations sensory effect, focusing on polysaccharide levels in wine.
RESULTS/DISCUSSION: Data shows ripeness has a more limited effect than expected on polysaccharide profiles in finished wine, but enzyme addition causes a marked decrease in soluble polysaccharides. An increase in polymeric pigments and tannins is noted with enzyme use. Sensory testing of these wines established a relationship between perceived astringency and polysaccharide, but also shows the traditionally accepted relationship between phenol content of red wines and perceived astringency is more complicated.
CONCLUSION: Enzyme maceration has an effect on perceived astringency in finished wines, but does not affect bitterness. Ripeness has a limited effect on polysaccharide extraction, but no significant differences in wine astringency. In this study, bitterness was not affected by ripeness nor enzyme maceration.
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