Lecture 17: Aging

1. Lecture 17: Aging

2. Reading Assignment: Text, Chapter 10, pages 382-415

3. AGING: As a means of achieving stability

4. Aging: To Achieve Stability • To allow reactions that are going to happen to occur before bottling • Polymerization of tannin • Polymerization of pigment • Stabilization of color • Loss of volatile esters

5. Polymerization

6. AGING: To correct a problem

7. Aging: To Correct a Problem • Allow “negatives” to disappear • Volatilization • Hydrolysis • Oxidation • Precipitation • Other Chemical reactions

8. AGING: As stylistic

9. Aging: As Stylistic • “Oxidative” versus “reductive” aging • Allow formation of new characters • Addition of new characters from cooperage • Addition of new characters from yeast lees/autolysis • Increase/Decrease complexity depends upon varietal/composition

10. Aging Variables • Time

11. Time Different reactions will occur at different rates. A steady state value may or may not be reached. [Compound] Time

12. Aging Variables • Time • Temperature

13. Temperature Faster at Higher Temperature Slower at Higher Temperature Temperature Independent

14. Aging Variables • Time • Temperature • Oxygen

15. Oxygen Exposure Leads To: • Polymerization of phenolics • Good: softens astringency • Bad: too much loss of color • Browning/Pinking • May be desirable or neutral (reds) • May be undesirable (whites) • Acetaldehyde • Stabilized color • Oxidized flavors

16. Acetaldehyde Formation OH O + 02 + H2O2 R OH O R OH O H2O2 + H3C-CH2 H3C-CH + 2H2O

17. Stabilization of Color Reaction of oxygen with anthocyanins leads to polymerization and stabilization of red color.

18. Control of Oxygen Exposure • Use inert gas flush (N2, CO2) • Limit headspace • Top-off barrels • Monitor saturations

19. Air Saturations • One “saturation” = 6 mL O2/L • Capacity for O2 is dependent upon the phenolic composition • A single saturation occurs with each air exposure • Racking • Fining • Filtration • Centrifugation • Movement to tank/barrel

20. Aging Variables • Time • Temperature • Oxygen • Cooperage

21. Cooperage • Glass • Stainless steel • Wood

22. Wood Variables • Source of wood • French • American • Other • Aging of wood • Toasting level • Number of times it has been used • Barrel, Staves, Chips

23. Wood • Allows limited oxygen exposure • Allows some evaporative loss • Adds nuances • Surface area versus volume of wine important

24. Aging Variables • Time • Temperature • Oxygen • Cooperage • Yeast lees

25. Yeast Lees • Yeast autolysis adds flavors • Long chain esters • Stimulates Malolactic Fermentation • Activity of yeast enzymes continues post-lysis • Impacts mouth feel

26. Aging Variables • Time • Temperature • Oxygen • Cooperage • Yeast lees • pH

27. pH • Affects rates of some reactions • Phenolic oxidations 9 times faster at pH 4.0 versus pH 3.0 • Affects microbial persistence and activity

28. Aging Variables • Time • Temperature • Oxygen • Cooperage • Yeast lees • pH • Catalysts

29. Catalysts • Metal ions can increase rates of some chemical reactions

30. Aging Variables • Time • Temperature • Oxygen • Cooperage • Yeast lees • pH • Catalysts • Chemical composition of wine

31. Chemical Composition of Wine It’s what in there that counts!

32. The 5 Goals of Post-Fermentation Operations: 5. PACKAGING

33. Packaging • Bottling • Sterile • Non-sterile • Closure • Cork • Synthetic cork • Screw cap • “Bag-in-box”