Wine Chemistry

Question 1

What is Succinic acid?

Answer 1

Succinic acid is a minor component in grapes and a byproduct of fermentaion. It has a sharp, slightly bitter, salty flavor.

Question 2

What are the five major components of wine?

Answer 2

Water
Alcohol
Acid
Sugar
Phenolic Compounds

Question 3

What percentage of wine is normally water?

Answer 3

80-90%

Question 4

Which alcohol is the main alcohol component in wine?

Answer 4

Ethyl Alcohol (ethanol)

Question 5

What is another name for Ethyl Alcohol?

Answer 5

Ethanol

Question 6

What types of alcohol are found in wine?

Answer 6

Ethyl Alcohol (primary)
Smaller Amounts: Glycerol, Methyl Alcohol (methanol), fused alcohols (fusel oils) or higher alcohols.

Question 7

What is a volatile compound?

Answer 7

A compound that evaporates easily.

Question 8

What percentage of a wine do acids make up?

Answer 8

.5-.75%

Question 9

What is the most prevalent acid in wine?

Answer 9

Tartaric

Question 10

Which acids are typically found in grapes?

Answer 10

Tartaric Acid
Malic Acid
Citric Acid (Minute amounts)
Succinic Acid (Minor component)

Question 11

What acids are from fermentation?

Answer 11

Lactic Acid
Acetic Acid
Succinic Acid

Question 12

What does Total Acidity measure?

Answer 12

The volume of all acids in a wine.

Question 13

Why is pH often used as a measurement for acidity rather than Total Acid?

Answer 13

Total acidity measure the volume of all acidities in a wine. Some acids have a more acidic taste than others, and some are stronger. The pH level is the combined chemical strength of the acids present.

Question 14

What is the normal pH range for wine?

Answer 14

2.9-3.9

Question 15

Does a wine with a lower pH taste more or less acidic than one with a higher pH?

Answer 15

A lower pH tastes more acidic.

Question 16

What is the percentage of sugar in most grapes at harvest?

Answer 16

15-28%

Question 17

What are the two main types of sugar found in grapes.

Answer 17

Glucose and Fructose

Question 18

What are phenolic compounds?

Answer 18

Molecules present in wine in minute quantities, and have a major impact on the sensory profile of a wine.

Question 19

What is a monosaccharide, and which sugars in wine are monosaccharides?

Answer 19

A simple sugar. Both Glucose and Fructose are simple sugars.

Question 20

What are the five main phenolics found in wine?

Answer 20

Anthocyanins
Flavonols
Tannins
Vanillin
Resveratrol

Question 21

What is an Anthocyanin?

Answer 21

A phenolic compound that gives red wine its color.

Question 22

How is the color of red wine affected by acid?

Answer 22

More acidic wines appear redder, less acidic wines look bluer.

Question 23

What is a Flavonol?

Answer 23

A phenolic compound that is a yellow pigment. It increases in grapes with increased exposure to sunlight.

Question 24

What happens to certain phenolic compounds over time?

Answer 24

They polymerize, form longer chains and become sediment.

Question 25

What is an Aldehyde?

Answer 25

Oxidized alcohols that are formed when wine is exposed to air.

Question 26

What are two examples of wine that encourage the formation of Aldehydes?

Answer 26

Sherry and Madeira.

Question 27

What is the most common Aldehyde?

Answer 27

Acetaldehyde.

Question 28

What is acetaldehyde?

Answer 28

An aldehyde formed by the oxidation of ethanol.

Question 29

What is an esther?

Answer 29

A molecule formed by the joining of an acid and alcohol.

Question 30

What is the largest group of odiferous compounds found in wine?

Answer 30

Esthers

Question 31

What is Ethyl Acetate?

Answer 31

The ester of acetic acid and ethanol.

Question 32

What aromas does Ethyl Acetate impart?

Answer 32

At low concentrations, fruity, flowery aromas. At high concentrations, faulty aromas of nail polish remover, varnish, or glue.

Question 33

Are esters considered a fault?

Answer 33

At high enough concentrations, the ester aromas may be faulty off-odors.

Question 34

What effect do dissolved gases have on wine?

Answer 34

Dissolved gases promote many chemical reactions through oxidation, which may be beneficial or to be avoided depending on the wine.

Question 35

What is a common dissolved gas found in wine?

Answer 35

Carbon dioxide is found in at least small quantities in all wines as a by-product of fermentation.

Question 36

What are the labeling requirements regarding Sulfites in the US?

Answer 36

If a wine contains more than 10 ppm of sulfur dioxide it must display the contains sulfites warning on the label.

Question 37

What are the benefits of sulfur in winemaking?

Answer 37

It is an antioxidant and an antibacterial agent.

Question 38

What are methoxypyrazines?

Answer 38

Also called a pyrazines, these are the flavor compounds that result in herbaceousness in wines.

Question 39

What is Rotundone?

Answer 39

A key aroma compound responsible for the "spicy" or "peppery" aroma in some red wines, particularly Syrah from cooler climates. Also found in Grüner Veltliner.

Question 40

What is Rancio?

Answer 40

A tasting term referring to a fortified wine or Vin Doux Naturel that was deliberately maderized.

Question 41

What are Terpenes?

Answer 41

Flavor compounds associated with the floral and citrus aromas found in wines such as Muscat, Gewürztraminer, and Riesling.

Question 42

What is Ullage?

Answer 42

It its the process of evaporation of wine held in a barrel. Head space at the top of the barrel is also called the ullage.