Chapter 1 - Wine Composition And Chemistry Flashcards
What are the major components of wine?
Water Alcohol Acid Sugar Phenolic compounds
80-90% of wine
Water
10-15% of wine
Alcohol, primarily ethyl alcohol/ethanol
What other types of alcohol occur in wine?
Glycerol, methyl alcohol/methanol, and fusel alcohols (fusel oils) or higher alcohols
What can result in tears or legs in the glass?
High levels of alcohol or residual sugar
How is a wine’s aroma carried to the nose?
Ethanol, a volatile compound, evaporating easily
0.5% to 0.75% of wine
Acids
Principal acids found in wine
Tartaric Malic Citric Lactic Acetic Succinic
Grape acids
Tartaric
Malic
Citric
Succinic
Fermentation acids
Lactic
Acetic
Succinic
Which acids are found in minute quantities in grapes?
Citric
Succinic
What are wine diamonds?
Solid crystals formed from tartaric acid at low temperatures that do not redissolve in wine, lowering the acidity of the wine.
What is the strongest acid in wine in terms of pH?
Tartaric
What is the flavor profile of Malic acid?
Sharp tasting, green apples
What grapes are high in Malic acid?
Underripe and cool-climate grapes
What acid may be added to increase the total acidity of a wine?
Citric
How is lactic acid produced in wine?
Lactic acid bacteria converts malic acid during malolactic fermentation
What is acetic acid?
Found in most types of vinegar, a low level is created during fermentation. It is volatile so it evaporates and joins the aroma, adding complexity to the bouquet, particularly in reds.
What is acetobacter?
Harmful (to wine) bacteria that causes a reaction between ethanol and oxygen resulting in higher concentrations of acetic acid possibly making a wine undrinkable.
What is succinic acid?
Minor component of grapes, by product of normal fermentation. Sharp, slightly bitter, slightly salty flavor.
What is total acidity?
Volume of all acids in a wine
What is pH?
Combined chemical strength of the acids present.
Typical pH scale of wine
2.9 to 3.9
What percent of sugar do grapes contain at harvest?
15-28%
What are the main sugars in grapes?
Glucose
Fructose
What are the phenolic compounds found in wine?
Anthocyanins Flavonols Tannins Vanillin Resveretrol
What are anthocyanins?
Give red wines their color.
How does acidity affect color in red wines?
More acidic wines appear redder, less acidic wines appear bluer
What are flavonols?
Yellow pigments found in white wines. Increased by exposure to sunlight. Summer climates will produce more golden wines than cooler/cloudier climates.
What are tannins?
Astringent, bitter compounds found in skins, seeds, and stems of grapes and also in oak and oak barrels. They form the structure or backbone of wine and are a natural preservative to protect from oxidation in the aging process. Produce a textural, drying sensation.
What is vanillin?
Aromatic compound in oak that imparts a vanilla scent to barrel aged wines.
What is resveretrol?
Compound believed to have beneficial health effects in humans.
Where are phenolics primarily concentrated?
The skin and seeds of grapes.
How is sediment created?
Phenolic compounds, mainly tannins and pigments, polymerize, becoming too heavy to stay suspended in the liquid and drop out of the solution. One of the main results of the aging process.
What are aldehydes?
Oxidized alcohols formed when wine is exposed to air.
What is acetaldehyde?
Most common aldehyde which is formed by the oxidation of ethanol. Gives fino sherries their distinct aroma.
What are esters?
Molecules resulting from the joining of an acid and an alcohol. Largest odiferous compounds in wine.
What is ethyl acetate?
Most common ester in wine, the ester of acetic acid and ethanol.
What is the effect of ethyl acetate?
In low concentrations, fruity, flowery aroma.
In high concentrations, faulty aromas of nail polish remover, varnish, or glue.
Why is sulfur added?
To absorb free oxygen molecules that can harm wine.
What is the threshold for “Contains Sulfites” warning labels?
10 parts per million
