Production of Fermentation Floral and Ester Taints

Linda F. BissonDepartment 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

R1-OH + R2-CCoA

O

R1-O-C-R2

O

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

– 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

Ester

Ethyl Acetate Ethyl Butyrate Isoamyl Acetate Hexyl Acetate Ethyl Hexanoate Ethyl Octanoate Ethyl Decanoate

Concentration Range Across Strains (mg/L) 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

Ester

Ethyl Acetate Ethyl Butyrate Isoamyl Acetate Hexyl Acetate Ethyl Hexanoate Ethyl Octanoate Ethyl Decanoate

Concentration Range Across Strains (mg/L) 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

ISOAMYL ACETATE

00.10.20.30.40.50.60.70.80.9

0 100 200 300 400 500 600 700

Time (Hours)

Co

nc.

(m

g/L

)

4.98

5

5.02

5.04

5.06

5.08

5.1

Wei

gh

t (K

g)

Stability of Esters

Ester Loss Volatilization:

– 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)