1. Production of Fermentation Floral and Ester Taints
Linda F. Bisson
Department of Viticulture and Enology
University of California, Davis, CA

2. Outline of Presentation
Introduction to Esters
Ester Formation during Fermentation
Stability of Esters

3. Introduction to Esters

4. What Is an Ester? Volatile molecule
Formed from the reaction of an alcohol and a keto acid
Formed enzymatically from an alcohol and a keto acid bound to the cofactor, Coenzyme A
Characteristic fruity and floral aromas

5. Ester Formation O
R1-OH
R2-CCoA O
R1-O-C-R2

6. Where do Esters Come from?
Can be formed by the chemical reaction of an alcohol and a keto acid
Can be formed enzymatically by the plant
Can be formed enzymatically by microbes

7. Where do Esters Come from in Wine?
Can be formed by the chemical reaction of an alcohol and a keto acid
Can be formed enzymatically by the plant
Can be formed enzymatically by microbes
Non-Saccharomyces yeasts
Saccharomyces
Lactic acid bacteria
Acetic acid bacteria

8. Ester Classes
Ethyl esters of acids
Acetate esters of alcohols

9. Ester Classes Ethyl esters of acids Acetate esters of alcohols
Keto acids from amino acid catabolism
Fatty acids from fatty acid biosynthesis or lipid degradation
Acetate esters of alcohols
Ethanol
Derivatives from nitrogen metabolism
Fusel oils from amino acid catabolism
Alcohols from purine and pyrimidine catabolism

10. Common Esters Found in Wine
Ethyl Propanoate
Ethyl -2-Methylpropanoate
Ethyl-2 -Methylbutanoate
Ethyl-3-Methylbutanoate
Isobutyl Acetate
2-Methylpropyl Acetate
2-Methylbutyl Acetate
3-Methylbutyl Acetate (Isoamyl acetate)
Hexyl Acetate
Requires grape precursor
Ethyl Lactate
Bacterial in origin

11. Positive Wine Characters Associated with Esters
Fruit
Apple
Apricot
Fig
Melon
Peach
Pear
Prune
Raspberry
Strawberry
Honey
Tropical fruit
Banana
Coconut
Mango
Pineapple
Floral
Rose
Butter
Spice
vanilla
Yeast (bread)

12. Esters Associated with Apple
Amyl acetate
Ethyl acetate
Ethyl butyrate
Isobutyl acetate
Phenethyl acetate

13. Esters Associated with Pineapple
Ethyl acetate
Ethyl butanoate (Ethyl butyrate)
Ethyl hexanoate

14. Esters Found in Chardonnay
Concentration Range Across Strains (mg/L)
Ethyl Acetate
Ethyl Butyrate
Isoamyl Acetate
Hexyl Acetate
Ethyl Hexanoate
Ethyl Octanoate
Ethyl Decanoate

15. Negative Wine Characteristics Associated with Esters
Foxy
Nail polish
Bubble gum/cotton candy
Soapy
Candle wax
Perfume
Intense fruit
Intense floral

16. Ester Expression Dependent upon chemical species present
Dependent upon concentrations: relative and absolute
Dependent upon matrix factors
Dependent upon yeast strain and substrates

17. In General . . .
The higher the concentration the more negative the impression is of the character
Longer chain esters fall into soapy, perfume range
Combinations of esters can confer a stronger aroma than the sum of the individual compounds

18. Negative Ester Characters
Nail polish/glue: ethyl acetate
Soap: ethyl octanoate, ethyl decanoate
Perfume: hexyl acetate
Rose: phenethylacetate, phenethyl alcohol

19. Esters Found in Chardonnay
Concentration Range Across Strains (mg/L)
Ethyl Acetate
Ethyl Butyrate
Isoamyl Acetate
Hexyl Acetate
Ethyl Hexanoate
Ethyl Octanoate
Ethyl Decanoate

20. Ester Formation During Fermentation

21. Ester Formation during Fermentation
Influence of non-Saccharomyces yeasts
Production by Saccharomyces

22. Production by Non-Saccharomyces yeast
Grape flora
Winery residents
Primary genera:
Hanseniaspora (Kloeckera)
Metschnikowia (Candida)
Candida
Pichia
Torulaspora
Kluveromyces

23. Production by Non-Saccharomyces yeast
Contribute generic fruity and floral notes
Can make excessive ethyl acetate (Hanseniaspora)
Better adapted to lower temperatures than Saccharomyces
Bloom during cold-settling
Bloom during cold maceration
Can be sulfite tolerant

24. Production by Saccharomyces
Yeast Strain
Nutrition (Sugar, Nitrogen)
Generally increased nitrogen in vineyard increases ester concentrations
During fermentation impacted by both nitrogen source (NH4+, amino acids) and nitrogen level interacting with yeast genetic background
Temperature
Grape Variety

25. Ester Formation in Wines
Vianna & Ebeler, 2001 J. Agric. Food Chem., 49(2):

26. Stability of Esters

27. Ester Loss Volatilization: Hydrolysis: Matrix effects:
temperature dependent
fermentation vigor dependent
Hydrolysis:
pH dependent
time dependent
Matrix effects:
masking: ethanol
enhancing: sugar, polyphenol, tannin

28. Ester Loss
Generally lost upon aging in barrel (volatilization and hydrolysis)
Lost upon aging in bottle (hydrolysis)
Most esters gone six months post-fermentation, depending upon aging and temperature of aging

29. Control of Ester Formation
Management of strains and microbial populations
Age under conditions favoring loss (or retention)

30. Ester Taint Tasting Glass 1: Control Chardonnay wine
Glass 2: Ethyl acetate
Glass 3: Ethyl octanoate, ethyl decanoate
Glass 4: Hexyl acetate
Glass 5: Phenethylacetate, phenethyl alcohol
Glass 6: Rhône 4600 esters, Grenache blanc

31. Ester Taint Tasting Glass 1: Control Chardonnay wine
Glass 2: Ethyl acetate: nail polish remover
Glass 3: Ethyl octanoate, ethyl decanoate: soap
Glass 4: Hexyl acetate: perfume
Glass 5: Phenethylacetate, phenethyl alcohol: rose
Glass 6: Rhône 4600 esters, Grenache blanc

32. Rhône 4600: Isolated from the Côtes du Rhône region
Complex aroma notes and elevated ester production such as tropical (pineapple) and fresh fruit (apple, pear, strawberry)