Wine Composition and Chemistry

Question 1

Name 5 major components of wine

Answer 1

Water
Alcohol
Acid
Sugar
Phenolic Compounds

Question 2

Wine typically contains _____% of water.

Answer 2

80-90%

Question 3

Wine typically contains _____% of alcohol by volume.

Answer 3

10-15%

Question 4

What is ethyl alcohol?

Answer 4

the primary result of alcoholic fermentation and the main alcohol component of wine.
also known as ethanol

Question 5

Name 4 other types of alcohol that can occur in wine production in small amounts.

Answer 5

Glycerol
Methyl Alcohol (Methanol)
Fusel Alcohols (Fusel Oils)
Higher Alcohols

Question 6

Acid accounts for what percentage of a wine’s volume?

Answer 6

usually between 0.5% and 0.75%

Question 7

What are the 6 principle acids in wine?

Answer 7

Tartaric
Malic
Citric
Lactic
Acetic
Succinic

Question 8

What is the most prevalent of the acids found in both grapes and wine?

Answer 8

Tartaric Acid

Question 9

What are tartrates?

Answer 9

“Wine diamonds”-solid crystals formed by tartaric acid at low temperatures.

Question 10

What winemaking process minimizes or avoids the formation of tartrates?

Answer 10

Cold Stabilization

Question 11

True or False: Tartaric acid is the strongest of the acids found in wine in terms of pH.

Answer 11

True

Question 12

What acid can be described as sharp-tasting and is frequently associated with green apples.

Answer 12

Malic Acid.

Question 13

What acid is sometimes added to increase the total acidity in a wine?

Answer 13

Citric Acid-although its distinctive citrus fruit flavor makes it generally unsuitable for quality wines.

Question 14

What are the 3 fermentation?

Answer 14

Lactic Acid
Acetic Acid
Succinic Acid

Question 15

What causes the creation of lactic acid in wine?

Answer 15

lactic acid bacteria which convert malic acid into lactic acid through malolactic fermentation

Question 16

Which of the wine acids are considered to be volatile?

Answer 16

Acetic Acid- most commonly found in vinegar, it readily evaporates and joins the aromas of the wine

Question 17

What is acetobacter?

Answer 17

a bacteria that when acetic acid is in higher concentration can cause a chemical reaction between ethanol and oxygen that makes a wine undrinkable.

Question 18

Describe Succinic Acid.

Answer 18

• a minor component in grapes and a by-product of normal alcoholic fermentation.
• has a sharp, slightly bitter, slightly salty flavor

Question 19

What are 2 numbers used to describe the acidity level of a wine and why are 2 different measurements used?

Answer 19

Total acidity (TA)
pH
-TA includes several acids, some of which are stronger than others

Question 20

What does pH measure?

Answer 20

The combined chemical strength of the acids present.

Question 21

Where is wine usually measured on the logarithmic pH scale?

Answer 21

between 2.9 and 3.9

- a lower pH indicates a stronger acid content

Question 22

Why do winemakers generally place particular emphasis on pH?

Answer 22

Because it gives an indication of stability and plays a role in determining sulfur additions

Question 23

What are the 2 sugars present in grapes?

Answer 23

Glucose

Fructose

Question 24

Name 5 phenolic compounds compounds.

Answer 24

Anthocyanins
Flavonols
Tannins
Vanillin
Resveratrol

Question 25

What phenolic compound is responsible for giving red wine its color?

Answer 25

Anthocyanins

Question 26

How does the acidity of a red wine affect its color?

Answer 26

more acidic wines appear redder in hue, while less acidic ones appear blue

Question 27

What are Flavonols (flavones)?

Answer 27

Yellow pigments found in white wines.

Question 28

What causes the increase in Flavonols in grapes?

Answer 28

increased exposure to sunlight | -white wines from sunnier climates tend to have a more golden color than wines from cooler or cloudier climates

Question 29

What phenolic compound acts as a natural preservative and helps protect red wines from oxidation during the aging process?

Answer 29

Tannins

Question 30

Name an aromatic phenolic compound.

Answer 30

Vanillin | -found in oak barrels imparts a vanilla scent to barrel-aged wines.

Question 31

True or False: | The Vanillin found in oak barrels is the same compound found in vanilla beans.

Answer 31

True

Question 32

Which phenolic compound in wine is believed to have several beneficial health effects in humans?

Answer 32

Resveratrol

Question 33

What causes the formation of sediment in wines?

Answer 33

Over time, some phenolic compounds, particularly tannins and pigments, tend to polymerize, or combine into longer molecule chains and become too heavy to stay suspended in the liquid.

Question 34

What are Aldehydes?

Answer 34

oxidized alcohols that are formed when a wine is exposed to air.

Question 35

Name 2 types of wines that are made using special techniques that encourage the formation of aldehydes.

Answer 35

Sherry and Madeira

Question 36

What is the most common aldehyde found in wine and how is it created?

Answer 36

Acetaldehyde-formed by the oxidation of ethanol