Wine Chemistry Flashcards
What is Succinic acid?
Succinic acid is a minor component in grapes and a byproduct of fermentaion. It has a sharp, slightly bitter, salty flavor.
What are the five major components of wine?
Water
Alcohol
Acid
Sugar
Phenolic Compounds
What percentage of wine is normally water?
80-90%
Which alcohol is the main alcohol component in wine?
Ethyl Alcohol (ethanol)
What is another name for Ethyl Alcohol?
Ethanol
What types of alcohol are found in wine?
Ethyl Alcohol (primary)
Smaller Amounts: Glycerol, Methyl Alcohol (methanol), fused alcohols (fusel oils) or higher alcohols.
What is a volatile compound?
A compound that evaporates easily.
What percentage of a wine do acids make up?
.5-.75%
What is the most prevalent acid in wine?
Tartaric
Which acids are typically found in grapes?
Tartaric Acid
Malic Acid
Citric Acid (Minute amounts)
Succinic Acid (Minor component)
What acids are from fermentation?
Lactic Acid
Acetic Acid
Succinic Acid
What does Total Acidity measure?
The volume of all acids in a wine.
Why is pH often used as a measurement for acidity rather than Total Acid?
Total acidity measure the volume of all acidities in a wine. Some acids have a more acidic taste than others, and some are stronger. The pH level is the combined chemical strength of the acids present.
What is the normal pH range for wine?
2.9-3.9
Does a wine with a lower pH taste more or less acidic than one with a higher pH?
A lower pH tastes more acidic.
What is the percentage of sugar in most grapes at harvest?
15-28%
What are the two main types of sugar found in grapes.
Glucose and Fructose
What are phenolic compounds?
Molecules present in wine in minute quantities, and have a major impact on the sensory profile of a wine.
What is a monosaccharide, and which sugars in wine are monosaccharides?
A simple sugar. Both Glucose and Fructose are simple sugars.
What are the five main phenolics found in wine?
Anthocyanins
Flavonols
Tannins
Vanillin
Resveratrol
What is an Anthocyanin?
A phenolic compound that gives red wine its color.
How is the color of red wine affected by acid?
More acidic wines appear redder, less acidic wines look bluer.
What is a Flavonol?
A phenolic compound that is a yellow pigment. It increases in grapes with increased exposure to sunlight.
What happens to certain phenolic compounds over time?
They polymerize, form longer chains and become sediment.
What is an Aldehyde?
Oxidized alcohols that are formed when wine is exposed to air.
What are two examples of wine that encourage the formation of Aldehydes?
Sherry and Madeira.
What is the most common Aldehyde?
Acetaldehyde.
What is acetaldehyde?
An aldehyde formed by the oxidation of ethanol.
What is an esther?
A molecule formed by the joining of an acid and alcohol.
What is the largest group of odiferous compounds found in wine?
Esthers
What is Ethyl Acetate?
The ester of acetic acid and ethanol.
What aromas does Ethyl Acetate impart?
At low concentrations, fruity, flowery aromas. At high concentrations, faulty aromas of nail polish remover, varnish, or glue.
Are esters considered a fault?
At high enough concentrations, the ester aromas may be faulty off-odors.
What effect do dissolved gases have on wine?
Dissolved gases promote many chemical reactions through oxidation, which may be beneficial or to be avoided depending on the wine.
What is a common dissolved gas found in wine?
Carbon dioxide is found in at least small quantities in all wines as a by-product of fermentation.
What are the labeling requirements regarding Sulfites in the US?
If a wine contains more than 10 ppm of sulfur dioxide it must display the contains sulfites warning on the label.
What are the benefits of sulfur in winemaking?
It is an antioxidant and an antibacterial agent.
What are methoxypyrazines?
Also called a pyrazines, these are the flavor compounds that result in herbaceousness in wines.
What is Rotundone?
A key aroma compound responsible for the “spicy” or “peppery” aroma in some red wines, particularly Syrah from cooler climates. Also found in Grüner Veltliner.
What is Rancio?
A tasting term referring to a fortified wine or Vin Doux Naturel that was deliberately maderized.
What are Terpenes?
Flavor compounds associated with the floral and citrus aromas found in wines such as Muscat, Gewürztraminer, and Riesling.
What is Ullage?
It its the process of evaporation of wine held in a barrel. Head space at the top of the barrel is also called the ullage.
