1. Winemaking Decisions and Wine Composition: Overview Linda F. Bisson Department of Viticulture and Enology University of California, Davis

2. EVERYTHING YOU DO HAS AN IMPACT

3. Juice and Wine Processing Pre-fermentation Processing Fermentation Management Post-fermentation Processing Aging

4. Pre-Fermentation Processing Harvest Decisions Crushing Pressing Temperature of each Sulfite addition Inoculation strategy Microbial bioloads

5. Juice/Must Treatments Skin contact Cold Soak Clarification Additions Adjustments

6. Skin Contact Allowing juice to remain in contact with skins and seeds Increases extraction of material from skins Increases astringency May be done at varying temperatures Will occur during pressing operation

7. Cold Soak Cold Soak: holding red must at low temperatures for an extended period of time prior to fermentation to increase extraction of components Impacts microbial flora

8. Clarification Removal of suspended particles in juice Can facilitate downstream processing May be removing needed yeast nutrients (over-clarifying)

9. Juice Clarification Natural (Gravity) Settling: Rack Juice from lees: results in loss of volume Batch and Continuous Drainers To separate juice from solids Control size of particles removed Centrifugation Can lead to aeration of wine May strip too many solids

10. Juice Clarification Filtration Juice may be difficult to filter Flotation Use of fine suspension of gas (nitrogen) bubbles Suspended pulp becomes attached to bubbles and floats to surface allowing removal

11. Juice/Must Additions Nutrient additions Direct impacts on microbial growth Indirect impacts on wine chemistry

12. Juice/Must Additions Nutrient additions Microorganisms

13. Yeast: Saccharomyces cerevisiae or Saccharomyces bayanus: No limit on addition, typically no more than 10 6 cells/mL. Bacteria: Malolactic bacteria, generally Oenococcus oeni: Also no limit on addition, can be as high as 10 8 cells/mL

14. Juice/Must Additions Nutrient additions Microorganisms Enzyme additions

15. Enzyme Additions Amylases: breakdown complex polysaccharides Cellulases: breakdown complex polysaccharides Pectinase: breakdown pectins Protease: breakdown of proteins Glycosidase : release of terpines

16. Purpose of Enzyme Additions Increase yield Facilitate settling Release flavors Prevent wine haze from forming later in processing

17. Juice/Must Additions Nutrient additions Microorganisms Enzyme additions Inert solids

18. Inert Solids Settling aids to increase clarification of juice Increase solids content to facilitate yeast fermentation

19. Juice/Must Additions Nutrient additions Microorganisms Enzyme additions Inert solids Sulfur dioxide (SO 2 )

20. Sulfur Dioxide Antioxidant: enzymatic Antimicrobial Stimulation of yeast Bleaches red wine color

21. Juice Additions Nutrient additions Microorganisms Enzyme additions Inert solids Sulfur dioxide (SO 2 ) Dimethyl Dicarbonate (DMDC)

22. Juice Additions Nutrient additions Microorganisms Enzyme additions Inert solids Sulfur dioxide (SO 2 ) Dimethyl Dicarbonate (DMDC) Ascorbic Acid: Antioxidant

23. Juice Additions Nutrient additions Microorganisms Enzyme additions Inert solids Sulfur dioxide (SO 2 ) Dimethyl Dicarbonate (DMDC) Ascorbic Acid: Antioxidant Oxygen

24. Stimulates microorganisms Required by yeast for optimal ethanol tolerance Stimulates oxidation reactions so oxidation products can be removed early (does not always work!)

25. Juice Additions Nutrient additions Microorganisms Enzyme additions Inert solids Sulfur dioxide (SO 2 ) Dimethyl Dicarbonate (DMDC) Ascorbic Acid: Antioxidant Oxygen Water

26. Acidity Adjustment Increase acidity Tartaric and malic acid addition Ion exchange Decrease acidity Calcium carbonate (not below 6 g/L) Ion Exchange Alter pH Ion Exchange

27. Post-Fermentation Operations: Clarity Compositional adjustment Stability Style Packaging

28. IF EVERYTHING HAS AN IMPACT, HOW DO YOU DECIDE WHAT TO DO?

29. Winery Trials Needs to be done with your equipment Needs to be done with your fruit Needs to be controlled – meaning you can reach a solid conclusion Needs to be evaluated using your subsequent processing strategy

30. The Importance of Controls Minimizing number of impact variables Isolation of effects Will dictate what question you are really answering

31. Today’s Program Pressing Pressure and skin contact Oxygen treatment effects Pre- and during fermentation Tannin management