Wine Composition and Chemistry Flashcards
Name 5 major components of wine
Water Alcohol Acid Sugar Phenolic Compounds
Wine typically contains _____% of water.
80-90%
Wine typically contains _____% of alcohol by volume.
10-15%
What is ethyl alcohol?
the primary result of alcoholic fermentation and the main alcohol component of wine.
also known as ethanol
Name 4 other types of alcohol that can occur in wine production in small amounts.
Glycerol
Methyl Alcohol (Methanol)
Fusel Alcohols (Fusel Oils)
Higher Alcohols
Acid accounts for what percentage of a wine’s volume?
usually between 0.5% and 0.75%
What are the 6 principle acids in wine?
Tartaric Malic Citric Lactic Acetic Succinic
What is the most prevalent of the acids found in both grapes and wine?
Tartaric Acid
What are tartrates?
“Wine diamonds”-solid crystals formed by tartaric acid at low temperatures.
What winemaking process minimizes or avoids the formation of tartrates?
Cold Stabilization
True or False: Tartaric acid is the strongest of the acids found in wine in terms of pH.
True
What acid can be described as sharp-tasting and is frequently associated with green apples.
Malic Acid.
What acid is sometimes added to increase the total acidity in a wine?
Citric Acid-although its distinctive citrus fruit flavor makes it generally unsuitable for quality wines.
What are the 3 fermentation?
Lactic Acid
Acetic Acid
Succinic Acid
What causes the creation of lactic acid in wine?
lactic acid bacteria which convert malic acid into lactic acid through malolactic fermentation
Which of the wine acids are considered to be volatile?
Acetic Acid- most commonly found in vinegar, it readily evaporates and joins the aromas of the wine
What is acetobacter?
a bacteria that when acetic acid is in higher concentration can cause a chemical reaction between ethanol and oxygen that makes a wine undrinkable.
Describe Succinic Acid.
- a minor component in grapes and a by-product of normal alcoholic fermentation.
- has a sharp, slightly bitter, slightly salty flavor
What are 2 numbers used to describe the acidity level of a wine and why are 2 different measurements used?
Total acidity (TA)
pH
-TA includes several acids, some of which are stronger than others
What does pH measure?
The combined chemical strength of the acids present.
Where is wine usually measured on the logarithmic pH scale?
between 2.9 and 3.9
- a lower pH indicates a stronger acid content
Why do winemakers generally place particular emphasis on pH?
Because it gives an indication of stability and plays a role in determining sulfur additions
What are the 2 sugars present in grapes?
Glucose
Fructose
Name 5 phenolic compounds compounds.
Anthocyanins Flavonols Tannins Vanillin Resveratrol
What phenolic compound is responsible for giving red wine its color?
Anthocyanins
How does the acidity of a red wine affect its color?
more acidic wines appear redder in hue, while less acidic ones appear blue
What are Flavonols (flavones)?
Yellow pigments found in white wines.
What causes the increase in Flavonols in grapes?
increased exposure to sunlight
-white wines from sunnier climates tend to have a more golden color than wines from cooler or cloudier climates
What phenolic compound acts as a natural preservative and helps protect red wines from oxidation during the aging process?
Tannins
Name an aromatic phenolic compound.
Vanillin
-found in oak barrels imparts a vanilla scent to barrel-aged wines.
True or False:
The Vanillin found in oak barrels is the same compound found in vanilla beans.
True
Which phenolic compound in wine is believed to have several beneficial health effects in humans?
Resveratrol
What causes the formation of sediment in wines?
Over time, some phenolic compounds, particularly tannins and pigments, tend to polymerize, or combine into longer molecule chains and become too heavy to stay suspended in the liquid.
What are Aldehydes?
oxidized alcohols that are formed when a wine is exposed to air.
Name 2 types of wines that are made using special techniques that encourage the formation of aldehydes.
Sherry and Madeira
What is the most common aldehyde found in wine and how is it created?
Acetaldehyde-formed by the oxidation of ethanol
