Production of Fermentation Floral and Ester Taints Linda F. Bisson Department of Viticulture and Enology University of California, Davis, CA
Outline of Presentation Introduction to Esters Ester Formation during Fermentation Stability of Esters
Introduction to Esters
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
Ester Formation O R1-OH + R2-CCoA O R1-O-C-R2
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
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
Ester Classes Ethyl esters of acids Acetate esters of alcohols
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
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
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)
Esters Associated with Apple Amyl acetate Ethyl acetate Ethyl butyrate Isobutyl acetate Phenethyl acetate
Esters Associated with Pineapple Ethyl acetate Ethyl butanoate (Ethyl butyrate) Ethyl hexanoate
Esters Found in Chardonnay Concentration Range Across Strains (mg/L) Ethyl Acetate Ethyl Butyrate Isoamyl Acetate Hexyl Acetate Ethyl Hexanoate Ethyl Octanoate Ethyl Decanoate 50 - 95 0.4 - 0.75 3.5 - 11.0 1.0 - 1.7 1.0 - 2.2 1.4 - 2.0 0.6 - 0.9
Negative Wine Characteristics Associated with Esters Foxy Nail polish Bubble gum/cotton candy Soapy Candle wax Perfume Intense fruit Intense floral
Ester Expression Dependent upon chemical species present Dependent upon concentrations: relative and absolute Dependent upon matrix factors Dependent upon yeast strain and substrates
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
Negative Ester Characters Nail polish/glue: ethyl acetate Soap: ethyl octanoate, ethyl decanoate Perfume: hexyl acetate Rose: phenethylacetate, phenethyl alcohol
Esters Found in Chardonnay Concentration Range Across Strains (mg/L) Ethyl Acetate Ethyl Butyrate Isoamyl Acetate Hexyl Acetate Ethyl Hexanoate Ethyl Octanoate Ethyl Decanoate 50 - 95 0.4 - 0.75 3.5 - 11.0 1.0 - 1.7 1.0 - 2.2 1.4 - 2.0 0.6 - 0.9
Ester Formation During Fermentation
Ester Formation during Fermentation Influence of non-Saccharomyces yeasts Production by Saccharomyces
Production by Non-Saccharomyces yeast Grape flora Winery residents Primary genera: Hanseniaspora (Kloeckera) Metschnikowia (Candida) Candida Pichia Torulaspora Kluveromyces
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
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
Ester Formation in Wines Vianna & Ebeler, 2001 J. Agric. Food Chem., 49(2): 589-595
Stability of Esters
Ester Loss Volatilization: Hydrolysis: Matrix effects: temperature dependent fermentation vigor dependent Hydrolysis: pH dependent time dependent Matrix effects: masking: ethanol enhancing: sugar, polyphenol, tannin
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
Control of Ester Formation Management of strains and microbial populations Age under conditions favoring loss (or retention)
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
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
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)