Dissertation
PHENOLIC EVOLUTION IN WINE: DETERMINATION OF NEW METHODOLOGY TO MEASURE PHENOLIC CONTENT AND THE IMPACT OF MATURITY, ALCOHOL, AND SULFUR DIOXIDE ON WINE COLOR DURING AGING
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/108483
Abstract
Wine phenolic compounds, namely anthocyanins and tannins, are extracted from grape skins and seeds during maceration and fermentation and provide a variety of sensory characteristics to wine, including color, astringency, and bitterness. As wines age, polymeric pigments are formed through the reaction of anthocyanins and tannins and are responsible for stable wine color and astringency modification. In this study, the effects of maturity and alcohol on wine phenolic compounds, specifically polymeric pigments, were investigated in order to determine the most important factors for polymeric pigment formation and stability. We found that the formation of polymeric pigments in red wine was highly correlated to the initial wine anthocyanin concentration (R2=0.735; 0.528 for Syrah and Cabernet Sauvignon, respectively). Factors that increased the concentration of both anthocyanins and tannins, namely by increasing fruit maturity and wine alcohol, increased the formation of polymeric pigments. Contrary to previous thought, the ratio between anthocyanins and tannins was not correlated to polymeric pigment formation. However, only 40-60% of initial wine anthocyanin content was retained in the form of polymeric pigment. This retention was increased with wines that had greater tannin, suggesting the presence of both reactants increases compound stability.
Additionally, characteristics beyond phenolic concentration, such as tannin polymer length and subunit composition, impact salivary protein-tannin interactions, which in turn impacts astringency. It has been proposed that phenolic hydrophobicity, which changes as a result of subunit composition and polymer length, relates to the strength of the protein-tannin interaction. Therefore, methodology was developed for both the separation of and the measurement of hydrophobicity of wine phenolic compounds. In a survey of Washington wines, hydrophobicity was negatively correlated to tannin concentration (R2=0.33). However, no single measured factor explained the hydrophobicity well, indicating it was a unique measurement. When hydrophobicity was examined in experimental wines, the phenolic hydrophobicity was significantly impacted by fruit maturity but was independent of wine alcohol. In controlled studies, phenolic hydrophobicity increased with wine age; however, this relationship was not observed in commercial wines. This suggests that picking and winemaking decisions have a larger impact on phenolic hydrophobicity than wine age.
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Details
- Title
- PHENOLIC EVOLUTION IN WINE: DETERMINATION OF NEW METHODOLOGY TO MEASURE PHENOLIC CONTENT AND THE IMPACT OF MATURITY, ALCOHOL, AND SULFUR DIOXIDE ON WINE COLOR DURING AGING
- Creators
- Caroline Place Merrell
- Contributors
- James F Harbertson (Advisor)Thomas Henick-Kling (Committee Member)Thomas Collins (Committee Member)Barbara Rasco (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Food Science
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 170
- Identifiers
- 99900581516901842
- Language
- English
- Resource Type
- Dissertation