Wine Composition and Chemistry Flashcards
The main type of potable alcohol in wine
Ethanol (Ethyl alcohol)
An acid that tastes like green apples
Malic acid
The most prevalent acid found in both grapes and wine
Tartaric acid
Another term for tartrates
Wine diamonds (tartartic acid crystals)
Conditions that can lead to a drop in malic acid
Warm/hot climate
The ripening phase
Over-ripe grapes
Malolactic fermentation
Acid not found in grapes, but often produced during secondary fermentation (mlf)
Lactic acid
Acid that is both a minor component of grapes, and a by-product of normal alcoholic fermentation
Succinic acid
Typical range of pH for most wines
2.9 to 3.9
Two main fermentable sugars found in grapes
Glucose and fructose
Sugar remaining in a wine post-fermentation
Residual sugar
Compounds that give red wine its color
Anthocyanins
Yellow pigments found in white wines
Flavonols (flavones)
Sources of tannin
Seeds, skins, and stems of grapes
Oak barrels/other oak products
Compound found in red wine known for health benefits
Resveratrol
What is meant by “polymerization”
When molecules (such as tannins) combine into longer molecule chains
Oxidized alcohols
Aldehydes
Molecules that result from the joining of an acid and an alcohol
Esters
Chemical reactions resulting from dissolved oxygen
Oxidation
In the US, wines containing more than _____ ppm of sulfur dioxide must carry a warning label
10 (ten)
How much water is typically found in wine?
80-90%
Where does most of the water in wine come from?
The grapes themselves
How much alcohol is typically found in wine?
10-15%
What is the main alcohol component of wine?
Ethyl alcohol or Ethanol
What other types of alcohol may be found in wine?
Glycerol Methyl alcohol (methanol) fusel alcohols (fusel oils) or higher alcohols
What does alcohol contribute to a wine?
the mouth-filling, tactile sensation of wine as it rests on the palate or “body”
How much of wine’s volume is made up by acid?
.5-.75
Which acids are grape acids?
Tartaric
Malic
(Citric)
(Succinic)
Which acids are fermentation acids?
Lactic
Acetic
Succinic
Strongest acid in terms of pH?
Tartaric
Which two conditions produce a wine high in Malic acid?
Underripe grapes
Cool Climate
What affect does malolactic fermentation have on a wine?
Softens
Smooths
Byproduct creates a creamy texture and occasionally “buttery” aroma
Where is acetic acid commonly found?
Vinegar
What is different about acetic acid?
It is volatile so it easily evaporates and joins the aromas of the wine adding complexity (too much will make a wine undrinkable)
What flavor does succinic acid offer?
Sharp, slightly bitter, slightly salty
What is Total Acidity (TA)?
Volume of all acids in a wine
What is pH?
Chemical strength of the acids present
What percentage of grapes are sugar at harvest?
15-28%
What can hide the minor flaws of lower quality wines?
Sweetness
What are the different kinds of phenolic compounds?
Anthocyanins Flavonols Tannins Vanillin Resveratrol
What are Anthocyanins?
Compounds that give red wine its color
Two factors that affect red wines color?
Anthocyanins
Acidity
Wines with more acid will appear _________?
Redder
Wines with less acid will appear __________?
Bluer
What are Flavonols?
Yellow pigments found in white wines
What causes Flavonols to increase?
Increased exposure to sunlight
Why do white wines from cooler (cloudier) climates tend to have less of a yellow hue than ones from warmer (sunnier) climates?
Less Flavonols or Flavones
What do tannins offer to a wine?
Structure
Preservative/Protection from oxidation during aging
What is Vanillin?
Aromatic phenolic compound in oak that imparts a vanilla scent to barrel-aged wines
It is the same compound found in oak and vanilla beans
Where are the phenolics of a grape concentrated?
Primarily in its skin and seeds
Are red wines or white wines more likely to be high in phenolic compounds?
Reds because of the increased contact with grape solids
What has a major effect on a wine as it ages?
Polymerization because the molecule chains become too heavy for integration and drop as sediment removing those flavors from the wine
What does sediment do to a red wine?
Lightens color
Makes the wine less astringent
How are Aldehydes formed?
Exposure to air
Which wines encourage the formation of aldehydes?
Sherry
Madeira
Most common type of aldehyde?
Acetaldehyde – formed by the oxidation of ethanol
Two ways a wine may become oxidized?
Exposure to oxygen
Exposure to heat
What gives Fino Sherries their distinctive aromas?
Acetaldehyde
What are Esters?
Molecules that result from the joining of an acid and an alcohol
What is one of the most common esters in wine?
Ethyl Acetate
What two elements combine to form Ethyl Acetate?
Ethanol and Acetic Acid
What aroma does Ethyl Acetate provide at low concentrations?
Fruity, Flowery Aroma
What aroma does Ethyl Acetate provide at high concentrations?
Nail Polish Remover
Varnish
Glue
Why is sulfur used in a wine?
To absorb oxygen molecules before they can affect the wine
Benefits of Sulfur/Sulfites
Preservative
Antioxidant
Antibacterial
Are sulfites found in all wines?
Yes, it is a naturally occuring part of fermentation, although winemakers can make the decision to not add any addition sulfur
