VEN124 Section VI

Wine Aroma and Flavor:

Putting It All Together

Lecture 19:

The Flavor and Aroma Compounds of Wine

Distribution of Aroma Compounds in White Wines

Vegetal

Fruity

(Terpenes)

Muscats

Chenin blanc

Fr. Columbard

Chardonnay Sauvignon

blanc

“Canadian

Muscat”

Rieslings

Traminer

Classes of Flavor/Aroma Compounds

• Pyrazines

Pyrazines

N

N

R

O-CH3

R =

-CH2-CH-CH3

-CH2-CH3

-CH3

CH3

Bell pepper

Potato

Peanut

Pyrazines• Derived from grape• Not microbial in origin• Vegetal characters

– Bell pepper– Chili– Bean– Carrot– Potato– Peanut– Roasted Barley

Classes of Flavor/Aroma Compounds

• Pyrazines• Terpenes

Terpenes

• Fruity fruit/floral aromas from grapes

• Can be produced by some yeasts and molds (but not by Saccharomyces)

• Derived from isoprene units

• May be unbound or bound (as glycosides)

• Only unbound terpenes can be detected

Terpenes

Formed from isoprene units

C

C

C

C C

1

2

3

4 5

The double bond can occur anywhere in the 5-member structure

Terpenes

• Monoterpenes: C10

• Higher terpenes: C10

Terpenes

Can occur as:

hydrocarbons

alcohols

aldehydes

ketones

esters

Monoterpene Hydrocarbons

CH3

C

CH3 CH2 4 5

3

21

5

4

32

1

Limonene

Monoterpene Alcohols

C

CH3 CH3

CH3

CH2OH

H

CH3

OH

CH2

C

CH3 CH3

Geraniol Linalool

Monoterpene Aldehydes

CH3 CH3

CHO

CHOH

H

C C

CH3 CH3 CH3 CH3

Geranial Neral

Higher Terpenes

• Includes napthalene derivatives

• From plants

• Fruit characters

• Fuel characters

Higher Terpenes

C

CH3

CH2

O

Grapefruit

Higher Terpenes

CH3

CH3 CH3

Trimethyl Dihydronapthalene

“Kerosene”

Classes of Flavor/Aroma Compounds

• Pyrazines• Terpenes• Shikimic acid derivatives

Shikimic Acid Derivatives

• Derived from aromatic amino acid metabolism

• Produced by plants, microbes, oak extraction

Shikimic Acid Derivatives

CO H

OCH3

OH

Vanillin

Classes of Flavor/Aroma Compounds

• Pyrazines• Terpenes• Shikimic acid derivatives• Lactones

Lactones

• Oxygen-containing 5-member ring compound

• From grapes, microbes, oak extraction

• Typical characters: cotton candy, generic candy, generic fruit, coconut, buttery

Lactones

O CH2OH OC4H9

O

CH3

Furfuryl Alcohol Methyl Lactone

Classes of Flavor/Aroma Compounds

• Pyrazines• Terpenes• Shikimic acid derivatives• Lactones• Esters

Esters

• From reaction of an alcohol and an acyl-CoA molecule

• Formed mainly by microbes, but can come from plant

• Readily hydrolyzed at wine pH

Esters

R1-OH R2-CCoA

O

R1-O-C-R2

O

Esters

Alcohol: ethanol or alcohol from amino acid, purine, pyrimidine degradation

Acid: acetic acid or acid from amino acid degradation, fatty acid biosynthesis

Esters

• Ethyl acetate: nail polish remover/glue

• Ethyl laurate: soap

• Isoamyl acetate: banana

• Phenethyl acetate: rose oil

Esters

• Short chain: fruity, floral

• Long chain: perfume, soap

• Lower concentration: fruity, floral

• Higher concentrations: perfume

Ester Formation Influenced By:• Temperature

– Higher temperature: increased loss• Volatilization• Hydrolysis

• Oxygen exposure– Stimulate fatty acid biosynthesis

• Nitrogen source availability– Precursor availability

• Strain/genetic background– As much as 10-fold difference in level of production

Classes of Flavor/Aroma Compounds

• Pyrazines• Terpenes• Shikimic acid derivatives• Lactones• Esters• Higher alcohols

Higher Alcohols

• Made mostly by microbes, can be made by plants

• From amino acid degradation/ biosynthesis

Fusel oils

Aromatic amino acid derivatives

The Fusel Oils

• 3-Methylbutanol

• 2-Methylbutanol

• Isobutanol

• Propanol

Classes of Flavor/Aroma Compounds

• Pyrazines

• Terpenes

• Shikimic acid derivatives

• Lactones

• Esters

• Higher alcohols

• Acids

Acids

• From plant or microbes

• Sourness

• Other characters: – Rancid (butyric acid)– Pungent (acetic acid)

Acids

Least

Sour

Most

Sour

Citrate Fumarate Malate Lactate

Succinate

Tartrate

Acetic Acid

Legal Limits: US CA OIV

White: 1.2 g/L 1.1g/L 0.98g/L

Red: 1.4 g/L 1.2g/L 0.98g/L

Threshold of Detection:

1 g/L

Classes of Flavor/Aroma Compounds

• Pyrazines• Terpenes• Shikimic acid derivatives• Lactones• Esters• Higher alcohols• Acids• Phenolic compounds

Phenolic Compounds

• Bitterness

• Astringency

• Produced by plant

• Can be converted into vinyl phenols by microbes (spoilage characters)

BitternessFlavanols OH

OH

HO

OH

O

OH

Catechin

AstringencyFlavanols and Non-flavinoids

OH

OHHO

COOH

OH

OH

CH

HC

C=O

O

HOOC-CH-CH-COOHOH

Gallic acid

Caftaric acid

Classes of Flavor/Aroma Compounds• Pyrazines• Terpenes• Shikimic acid derivatives• Lactones• Esters• Higher alcohols• Acids• Phenolic compounds• Sulfur-containing compounds

Sulfur-Containing Compounds

• Low thresholds of detection

• Generally produced by microbes– Degradation of sulfur containing amino

acids– Spontaneous reactions from microbially-

derived sulfides

Sulfur-Containing Compounds

• Sulfides

• Thiols

• Sulfoxides

Sulfides

• H2S (hydrogen sulfide): rotten egg

• CH3-S-CH3 (dimethyl sulfide): cabbage, canned corn

• CH3-S-S-CH3 (dimethyl disulfide): clam

Sulfur-Containing Compounds

• Sulfides

• Thiols

• Sulfoxides

Thiols

• CH3-SH (methanethiol): rubber

• CH3-CH2-SH (ethanethiol): onion, rubber, skunk

Sulfur-Containing Compounds

• Sulfides

• Thiols

• Sulfoxides

Sulfoxides

• CH3-SO-CH3 (dimethyl sulfoxide): plastic, rubber hose

Sulfur-Containing Compounds

• Sulfides

• Thiols

• Sulfoxides

• Thio alcohols

Thio Alcohols

• HS-CH2-CH2-OH (mercaptoethanol): barnyard

• CH3-S-(CH2)4-OH (thiomethylbutanol): garlic, chive

• CH3-S-(CH2)3-OH (methionol): raw potato, soy

Classes of Flavor/Aroma Compounds• Pyrazines• Terpenes• Shikimic acid derivatives• Lactones• Esters• Higher alcohols• Acids• Phenolic compounds• Sulfur-containing compounds• Amino acid derivatives

Amino Acid Derivatives

• Several other types of compounds can be formed from amino acids by yeast and bacteria

• Appearance depends upon which microbes are present and what nitrogen/carbon sources are present

Amino Acid Derivatives: Mousiness

N NC-CH3

O

HC-CH3

O

2-Acetyl-tetrahydro-pyridine

Metabolite of lysine made by Lactic Acid Bacteria and Brettanomyces

Classes of Flavor/Aroma Compounds• Pyrazines• Terpenes• Shikimic acid derivatives• Lactones• Esters• Higher alcohols• Acids• Phenolic compounds• Sulfur-containing compounds• Amino acid derivatives• Specific compounds

Specific Compounds

• Other plant compounds associated with aroma

• Not well characterized

Specific Compounds: Methyl Anthranilate

Concord Grape Character: “Foxy”

NH2

C-O-CH3

O