Chapter 1 - Wine Composition and Chemistry

Question 1

What are the major components of wine?

Answer 1

water, alcohol, acid, sugar, phenolic compounds

Question 2

What are the types of alcohols in wine?

Answer 2

Ethyl
Glycerol
Methyl
Fusel
Higher

Question 3

How is wine’s aroma carried to the nose?

Answer 3

Through ethyl alcohol which evaporates easily and carries the wine’s aromas to the nose.

Question 4

What causes wine to have weight or body?

Answer 4

Alcohol

Question 5

Acid is what percentage of wine’s volume?

Answer 5

.5%-.75%

Question 6

What types acid in wine are caused by the grapes?

Answer 6

Tartaric
Malic
Citric
Succinic

Question 7

What types acid in wine are caused by fermentation?

Answer 7

Lactic, acetic, succinic

Question 8

Describe some aspects of tartaric acid in wine.

Answer 8

most common, strongest pH, can form wine diamonds (tartrates) at low temps., (tartrates can be minimized through cold stabilization)

Question 9

Describe aspects of malic acid in wine.

Answer 9

Sharp tasting (green apple), found in wine made with underripe grapes or cool-climate grapes, can be mitigated using malolactic fermentation.

Question 10

Describe aspects of citric acid in wine

Answer 10

Is not naturally found in wine, sometimes added to increase total acidity, generally not found in quality wines.

Question 11

Describe lactic acid in wine.

Answer 11

Not naturally found in wine. Created by lactic acid bacteria (converts malic acid into lactic acid in malolactic fermentation). Results in a softer and smoother mouthfeel in wine.

Question 12

Describe acetic acid in wine

Answer 12

Type of acid found in vinegar. It is volatile, so you can smell it in the aroma. In higher concentrations it can cause a chemical reaction which will make the wine undrinkable.

Question 13

What pH level scale is used to measure wine?

Answer 13

Between 2.9 and 3.4. (2.9 is more acidic than 3.4)

Question 14

What does a lower pH mean?

Answer 14

Stronger acid content. (2.9 will have more acid than 3.4)

Question 15

Why do winemakers care about pH?

Answer 15

It gives an indication of stability

Helps determine sulfur additions

Question 16

What percentage of sugar do wines typically contain at harvest?

Answer 16

15%-28%

Question 17

What types of sugar is in wine?

Answer 17

Glucose

Fructose

Question 18

Name phenolics that are found in wine

Answer 18

Anthocyanins
Flavonols
Tannins
Vanillin
Resveratrol

Question 19

What are anthocyanins?

Answer 19

Compounds that give red wine its color

color is also influenced by acidity levels - more acidic wines are redder in hue, less acidic wines appear bluer

Question 20

What are flavonols?

Answer 20

Yellow pigments found in white wines. They increase in grapes with increased exposure to sunlight.

(Sunnier climates tend to have wines with more golden color than wines from cooler climates)

Question 21

What are tannins?

Answer 21

Astringent, bitter compounds found in the skins, seeds, and stems of grapes. Also found in oak and oak barrels. They help form the structure of big red wines. Natural preservative which helps protect wines from oxidation.

Question 22

What is vanillin?

Answer 22

Aromatic phenolic compound in oak that imparts a vanilla scent to barrel-aged wines.

Question 23

What is resveratrol?

Answer 23

A compound in wine believed to have several beneficial health effects in humans.

Question 24

Where to phenolics come from?

Answer 24

The grape skins and seeds.

Question 25

How is sediment in wine formed?

Answer 25

The phenolics in wine (tannins and pigments) polymerize (combine into long molecule chains). THe chains become too heavy to stay suspended and drop out of the liquid. This creates sediment which will cause a wine to be lighter in color and less astringent.

Question 26

What are aldehydes?

Answer 26

Oxidized alcohols that are formed when wine is exposed to air. (This is also what gives fino Sherry its distinctive aroma.)

Question 27

What are esters?

Answer 27

Molecules that result from the joining of acid and alcohol. Can result in nice aromas at lower concentrations or faulty aromas at higher concentrations.

Question 28

What is ethyl acetate?

Answer 28

A type of ester formed when acetic acid and ethanol combine.

Question 29

What type of aromas does ethyl acetate impart to a wine at low concentrations?

Answer 29

Fruity, flowery aroma

Question 30

What type of aromas does ethyl acetate give to a wine at high concentrations?

Answer 30

Nail polish remover, varnish, or glue.

Question 31

What are dissolved gases?

Answer 31

They are present in any liquid, but not in high concentrations. Examples: dissolved oxygen and CO2.

Question 32

What are sulfites?

Answer 32

A class of chemicals based on sulfur. It is an important preservative widely used to keep wines stable after fermentation. Produced in minute quantities and is a natural by-product of fermentation. (Some people are extremely allergic to it – wines in the US need to be labeled, “contains sulfites”)

Question 33

When do wines need to carry a label “contains sulfites” in the US?

Answer 33

When a wine has more than 10 ppm of sulfur dioxide