Chemestry Flashcards
What is the major alcohol in wine?
Ethanol
What are the fermentable sugars in grapes?
Glucose
Fructose
What are the unfermentable sugars in grapes?
Arbinose
Rhamnose
Xylose
At what abv does yeast die?
18-21%
What is the German term for adding unfermented grape juice to wine?
Süssreserve
Which is sweeter: fructose or glucose?
Fructose is twice as sweet as glucose.
Which sugar ferments first: fructose or glucose?
Glucose
The process by which sugar is added to unfermented grape must is called?
Chaptalization
Named after Jean Antoine Chaptal
What is the purpose of chaptalization?
Indented to make the resulting wine higher in alcohol NOT sweeter.
Describe tartaric acid.
Tartaric: harsh and biting, cold stabilization process (chilling a wine to 22-27*F for several weeks) precipitates 1/3 to 1/2 of the tartaric acid out of wine
Describe malic acid.
Green apples, delicate and fragile, broken down by yeast, malolactic fermentation is the process by which lactic bacteria convert malic acid to lactic acid
What are the primary acids in wine not found in grapes?
Lactic and Succinic
What is the primary acid in wine?
Tartaric
What acids are found in the grape?
Citric, Malic, and Tartaric
How does bottle bouquet occur?
Most phenolics combine with sugars, as wine matures in bottle, the phenolic flavor precursors split from their sugars, resulting in the development of bottle bouquet.
What is polymerization?
Polymerization is the process by which tannins and pigments combine into long chains of molecules, eventually falling out as sediment and leaving a wine lighter and less astringent, another function of bottle age.
What are the substances responsible for the color of “red” wine?
Anthocyanins
How does acid affect color in red wine?
The more acidic, the redder it is.
The less acidic, the more blue in the mix.
What are the yellow pigments in white wine called?
Flavones
How does acid affect white wine?
The more acid, the paler the color.
The less acid, the more gold.
How does the grain of oak impact tannin?
Tight-grained oak (cool forest) = less tannin.
Wide-grained oak (warm forest) = more tannin.
How do the barrel staves impact tannin?
Air drying (slow) staves = less tannin Kiln-dried = more tannin
How does the splitting of staves impact tannin?
Hand-splitting (with the grain) = less tannin Sawn staves (agains grain) = more tannin
How does barrel toast level impact tannin?
Heavy toast = less tannin
Light toast = more tannin
How many molecular compounds can we detect (smell) in wine?
Approx. 200 out of nearly 500
When wine is exposed to air, alcohols oxidize to form…
Aldehydes
What is the most widely known aldehyde?
Acetaldelyde
What is the most aldehydic wine?
Sherry!
Red wine fermentation takes place between which temps?
60-90* F (14-35* C)
Malolactic Fermentation is…
The process in which bacteria cause Malic Acids to be changed to Lactic Acids.
What is the most important strain of yeast?
Saccharomyces cerevisiae
