Physiology of the Grape Berry Flashcards
Where does the berry come from?
The result of a successfully fertilized flower
What is the berry’s purpose?
The organ of survival for the vine species. It is designed to attract animals that help disperse seeds throughout the environment.
When did humankind first divert viticulture into winemaking?
6000-5000 BCE
The Neolithic Era
What is the composition of the grape and the approximate proportions (by weight) of those parts?
Seeds (5%)
Flesh/Pulp (80%)
Skin (15%)
What is the Bloom?
A waxy coating on the outside of the berry
Describe the outer layer of a grape’s skin.
A tough, waxy cuticle that is not very permeable to water
What is a Teinturier?
A grape that has both dark skin and dark flesh. This is because their flesh also contains anthocyanins.
What wine components can be found in grape skins?
Tannins
Anthocyanins (Black Cultivars)
Aroma and Flavor Precursors
What wine components can be found in the flesh (pulp) of the grape?
Water
Sugars
Acids
Other Constituents
What wine components can be found in grape seeds?
Tannins
Bitter Oils
What happens to seeds during ripening? How is this used in cultivation?
Seeds turn brown and the color change can be associated with desired berry ripeness.
What attaches the berry to the vine?
A Stem, also known as a Pedicel
What is the main constituent of a grape berry?
Water
What is the second largest constituent of a grape berry?
Sugars
Which sugars exist in a grape berry? What are they used for?
Glucose and Fructose
To build the distinctive compounds of the berry, such as acids, phenolics, and volatile aromas.
Where are the sugars located in the grape and how much of the grape do they comprise?
Mostly in the flesh
90-94% of the grape’s total soluble solids. It appear mostly dissolved in the grape’s water.
What is the proportion of glucose and fructose in grapes?
In ripe grapes, glucose and fructose are balanced
In late harvested fruit, there is more fructose
What are the main acids in grapes? What proportion of the total acids of the berry do they comprise?
Tartaric and Malic acids
About 90%
What other acids can be found in the berry?
Citric
Succinic
Phenolic
How does Malic acid respond to high temperature?
Malic acid is sensitive to temperature in general and respired during ripening.
Higher temperatures = more respiration, leading to lower acid levels
How does Tartaric acid respond to high temperature?
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.
What are two major phenolic compounds found in grapes?
Anthocyanins
Tannins
Where are Tannins found in grapes?
Skins
Seeds
Stems
What are Tannins?
Large molecules which are able to combine with proteins. They confer astringency on the palate.
Of the Tannins found in the Seeds, Skins, and Stems of grapes, which are considered softer and rounder?
Tannins from the Skins
Where in the grape can you find Anthocyanins?
The grape’s skins
In Teinturier grapes, you can find them in the flesh as well.
How does Anthocyanin production relate to temperature?
It is strongly related to temperature. The ideal temperature range is 17°C-26°C.
Temperatures over 30°C inhibit anthocyanin production.
What are Monoterpenes?
A volatile compound with a perfumed, floral aroma common in
Gewürztraminer Albariño Muscat Riesling Pinot Gris Viognier
What are Methoxypyrazines?
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)
At what levels are Methoxypyrazine desirable?
“Modest levels”
How is grape ripeness defined?
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).
What is Sugar Ripeness? Where is sugar used in law to define ripeness?
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.
What is Technical Ripeness?
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
What is Physiological Ripeness?
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.
