Physiology of the Grape Berry

Question 1

Where does the berry come from?

Answer 1

The result of a successfully fertilized flower

Question 2

What is the berry’s purpose?

Answer 2

The organ of survival for the vine species. It is designed to attract animals that help disperse seeds throughout the environment.

Question 3

When did humankind first divert viticulture into winemaking?

Answer 3

6000-5000 BCE

The Neolithic Era

Question 4

What is the composition of the grape and the approximate proportions (by weight) of those parts?

Answer 4

Seeds (5%)

Flesh/Pulp (80%)

Skin (15%)

Question 5

What is the Bloom?

Answer 5

A waxy coating on the outside of the berry

Question 6

Describe the outer layer of a grape’s skin.

Answer 6

A tough, waxy cuticle that is not very permeable to water

Question 7

What is a Teinturier?

Answer 7

A grape that has both dark skin and dark flesh. This is because their flesh also contains anthocyanins.

Question 8

What wine components can be found in grape skins?

Answer 8

Tannins

Anthocyanins (Black Cultivars)

Aroma and Flavor Precursors

Question 9

What wine components can be found in the flesh (pulp) of the grape?

Answer 9

Water

Sugars

Acids

Other Constituents

Question 10

What wine components can be found in grape seeds?

Answer 10

Tannins

Bitter Oils

Question 11

What happens to seeds during ripening? How is this used in cultivation?

Answer 11

Seeds turn brown and the color change can be associated with desired berry ripeness.

Question 12

What attaches the berry to the vine?

Answer 12

A Stem, also known as a Pedicel

Question 13

What is the main constituent of a grape berry?

Answer 13

Water

Question 14

What is the second largest constituent of a grape berry?

Answer 14

Sugars

Question 15

Which sugars exist in a grape berry? What are they used for?

Answer 15

Glucose and Fructose

To build the distinctive compounds of the berry, such as acids, phenolics, and volatile aromas.

Question 16

Where are the sugars located in the grape and how much of the grape do they comprise?

Answer 16

Mostly in the flesh

90-94% of the grape’s total soluble solids. It appear mostly dissolved in the grape’s water.

Question 17

What is the proportion of glucose and fructose in grapes?

Answer 17

In ripe grapes, glucose and fructose are balanced

In late harvested fruit, there is more fructose

Question 18

What are the main acids in grapes? What proportion of the total acids of the berry do they comprise?

Answer 18

Tartaric and Malic acids

About 90%

Question 19

What other acids can be found in the berry?

Answer 19

Citric

Succinic

Phenolic

Question 20

How does Malic acid respond to high temperature?

Answer 20

Malic acid is sensitive to temperature in general and respired during ripening.

Higher temperatures = more respiration, leading to lower acid levels

Question 21

How does Tartaric acid respond to high temperature?

Answer 21

There is no real effect on Tartaric acid by temperature. It is stronger and more stable than Malic acid.

Levels remain fairly constant after véraison.

Question 22

What are two major phenolic compounds found in grapes?

Answer 22

Anthocyanins

Tannins

Question 23

Where are Tannins found in grapes?

Answer 23

Skins

Seeds

Stems

Question 24

What are Tannins?

Answer 24

Large molecules which are able to combine with proteins. They confer astringency on the palate.

Question 25

Of the Tannins found in the Seeds, Skins, and Stems of grapes, which are considered softer and rounder?

Answer 25

Tannins from the Skins

Question 26

Where in the grape can you find Anthocyanins?

Answer 26

The grape’s skins

In Teinturier grapes, you can find them in the flesh as well.

Question 27

How does Anthocyanin production relate to temperature?

Answer 27

It is strongly related to temperature. The ideal temperature range is 17°C-26°C.

Temperatures over 30°C inhibit anthocyanin production.

Question 28

What are Monoterpenes?

Answer 28

A volatile compound with a perfumed, floral aroma common in

Gewürztraminer
Albariño
Muscat
Riesling
Pinot Gris
Viognier

Question 29

What are Methoxypyrazines?

Answer 29

A category of volatile aromas with a characteristic herbal and green pepper aroma common in

Sauvignon Blanc
Semillon
Cabernet Sauvignon
Merlot
Cabernet Franc
Carmenère

(All share direct DNA relationships)

Question 30

At what levels are Methoxypyrazine desirable?

Answer 30

“Modest levels”

Question 31

How is grape ripeness defined?

Answer 31

Ultimately, by the style of wine being produced. In some regions the level of potential alcohol is determined by the place the grapes are grown and wine (eg. Corton-Charlemagne, Barolo Riserva, etc).

Question 32

What is Sugar Ripeness? Where is sugar used in law to define ripeness?

Answer 32

Using the level of sugar in a grape to define when the berries can be picked for a certain style of wine.

Germany and Austria both have legally defined terms for the sugar levels required for wine styles.

Question 33

What is Technical Ripeness?

Answer 33

The determination of ripeness by analytical parameters other than sugar, usually pH and total acidity. Harvest is usually determined by the balance of acid and sugar in the berry.

aka Technological Ripeness

Question 34

What is Physiological Ripeness?

Answer 34

A measure of berry ripeness that includes sugars and acids with the addition of flavor aromas, their attributes, and the volume and quality of anthocyanins and tannins.

Sometimes called Flavor Ripeness, though this is subjective and depends on style.