Ch. 1 - Wine Composition & Chemistry Flashcards
(32 cards)
What is wine from a scientist’s point of view?
Wine is a complex blend of chemicals that collectively give the liquid its visual, olfactory, and tactile characteristics.
What are the major components of wine?
The major components of wine include the following: • Water • Alcohol • Acid • Sugar • Phenolic compounds
What % of wine is water?
Wine is typically 80-90% water. The water in wine is
primarily from the grapes themselves, although small
amounts of water may be added incidentally during
winemaking.
What type of alcohol is present in wine?
Ethyl alcohol, also referred to as ethanol, is the primary
result of alcoholic fermentation and the main alcohol
component of wine. Other types of alcohol that occur
in smaller amounts include glycerol and methyl alcohol
( or methanol), as well as a group of compounds known
asfusel alcohols (fuse/ oils) or higher alcohols.
What carries wine aromas to the nose?
Ethanol is a volatile compound, which means that it evaporates easily. When it does, it carries the wine’s aromas to the nose.
What does acid contribute to the wine?
A variety of acids, especially in white wines, give
the wine much of its structure, balance, and thirst quenching refreshment. Acids usually make up
between 0.5% and 0.75% of a wine’s volume.
Name the various types of acids in wine.
Grape Acids
- Tartaric Acid
- Malic Acid
- (Citric Acid)
- (Succinic Acid)
Fermentation Acids
- Lactic Acid
- Acetic Acid
- Succinic Acid
Which acid is the most prevalent acid in wines?
Tartaric acid is the most prevalent of the acids
found in both grapes and wine. It is also the
strongest in terms of pH. Tartaric acid also has
a unique propensity to form solid crystals at
low temperatures.
How can “Wine Diamonds” be avoided in wines?
The formation of tartrates can be avoided
or minimized through the winemaking process of
cold stabilization.
How can malic acid be reduced in wine?
High levels of malic acid can be assuaged using the winemaking technique known as malolactic fermentation.
Which acid is added in wines for acidification?
Citric acid is sometimes added to
increase the total acidity in a wine, although its
distinctive citrus fruit flavor makes it generally
unsuitable for quality wines.
Which acid is not naturally found in grapes but is found in wines?
Lactic acid is not found in grapes; rather, it is
created in wine by lactic acid bacteria, which
convert malic acid into lactic acid in the optional
winemaking process known as malolactic
fermentation.
What effect does MLF have on wine?
MLF gives the wine a creamy texture and, in some cases, a “buttery” aroma.
Which of the acids found in wines is volatile?
Acetic acid is volatile, so it readily evaporates and joins the aromas of the wine, adding to the complexity of a wine’s bouquet, particularly in red wines.
What is Acetobacter?
Higher concentrations of acetic acid typically the result of a chemical reaction between ethanol and oxygen caused by harmful (to wine) bacteria called acetobacter, can be unpleasant and may make a wine undrinkable.
What is Total Acidity (TA)?
Total acidity (TA), which is the volume of all the acids in a wine . In general, more acid equates to a more acidic taste.
What is pH in wines?
The pH level of a wine represents the combined chemical strength of the acids present. Wine usually measures between 2.9 and 3.9 on the logarithmic pH scale. A lower pH indicates a stronger acid content.
Thus, a wine with a pH of 2.9 will be more acidic than a wine with a pH of 3.4.
What sugars are present in wines?
The grapes contain roughly equal amounts of two sugars:
• Glucose
• Fructose
Name the phenolic compounds present in wines.
- Anthocyanins
- Flavonols
- Tannins
- Vanillin
- Resveratrol
What are Anthocyanins?
Anthocyanins are compounds that give red wine
its color, which in fact ranges from blue to purple
to red. The color of a red wine is influenced by
both the amount of anthocyanins and the acidity
level of the wine; more acidic wines appear redder
in hue, while less acidic ones appear bluer.
What are Flavonols?
Flavonols are yellow pigments are found in white wines. Flavonols (sometimes called fiavones) increase
in grapes with increased exposure to sunlight;
therefore, white wines from sunnier climates tend
to have a more golden color than white wines
from cooler (or cloudier) climates.
What are Tannins?
Tannins are astringent, bitter compounds
found in the skins, seeds, and stems of grapes .
They are also found in oak and oak barrels.
These compounds form part of the structure,
or “backbone,” of big red wines.
What is Vanillin?
Vanillin is an aromatic phenolic compound in oak
that imparts a vanilla scent to barrel-aged wines.
What causes a wine to throw sediments?
Over time, some phenolic compounds , particularly
tannins and pigments, tend to polymerize, or combine into longer molecule chains. These chains may eventually become too heavy to stay suspended in the liquid and may drop out of the solution as sediment.
