Impact of Winemaking Decisions on White Wine Mouthfeel

1. Impact of Winemaking Decisions on White Wine Mouthfeel Linda F Bisson Department of Viticulture and Enology, UCD May 9, 2013

3. Physiology of Mouthfeel • Binding to salivary proteins • Interference in binding of components to salivary proteins • Binding to other proteinaceous surfaces in the mouth

4. Factors Impacting White Wine Mouthfeel • Polyphenolic content/Astringency • Glycerol/Sugar alcohols • Residual sugar • Acidity • Ethanol • pH

5. Astringency in White Wines: Phenolic Content • Skin contact • Skin and seed damage during processing • Varietal • Growing region • Impacted by aging • Aging and aging in barrel • Oak amendments

6. Ethanol • Ethanol has an impact • Direct effects • Heat • Tactile irritation • Indirect effects • Interference in binding reactions • Enhances perceptions of sweetness

7. Acidity • Direct effect in being detected by sensors: astringent like sensations elicited • Indirect effect in altering binding of other components

8. pH • Final pH adjustment of wine has an impact: Altering binding of components to sensory receptors • Inverse relationship: Decreasing pH leads to increased astringency

9. Factors Are Interacting • pH and acidity can interfere in binding of astringent compounds to salivary proteins • Polysaccharides and small peptides: competition for binding • Ethanol can impact perception of other characters: change in binding kinetics • Factors can generate competing signals or enhance the same signal (tone down or increase astringency

10. Practices Impacting White Wine Mouthfeel • Native fermentation • Direct inoculation with non-Saccharomyces yeast • Sur lie aging • ML Fermentation • pH adjustments

11. Native Fermentation • Contributions from bacterial flora: • Wild Lactic acid bacteria: • Change in acidity/pH • Production of polysaccharides • Production of small peptides and lipids • Production of proteases and other hydrolases • Non- Saccharomyces yeast: • Production of polysaccharides • Production of small peptides and lipids • Production of proteases and hydrolases

12. Direct Inoculation with Non-Saccharomyces Yeast • Polysaccharide production

13. Sur Lie Aging • Release of cell components • Hydrolases • Release of: • Lipid • Mannoprotien • Polysaccharide release • Peptides • Stimulation of growth of other microbes

14. Malolactic Fermentation • Changes in acidity/pH • Polysaccharide release

15. pH Adjustments • pH adjustment of juice complicated: multiple possible impacts on mouth feel • Organisms present • Extractability and stability of macromolecular components • Impact on polymerization reactions

16. pH During Fermentation Trial • Chardonnay • Yeast strain: EC1118 • pH of juice: 3.65 • Fermentation temperature: 68 F • 50 ppm SO2 • 23 Brix • Adjusted with potassium bicarbonate or tartaric acid to +0.2, -0.2 and -0.4 pH units

17. Final Values of Wine

18. Tastings • Glass 1: Control, pH 3.59 • Glass 2: +0.2, pH 3.77 • Glass 3: -0.2, pH 3.35 • Glass 4: -0.4, pH 3.11