Wine Composition and Chemisty

Question 1

What alcohol level do most grapes produce when fermented?

Answer 1

10-15% without any added sugar

Question 2

Why is grape juice good at warding off harmful bacteria?

Answer 2

Its unusually high in tartaric acid

Question 3

What are the major components of wine?

Answer 3

Water, alcohol, acid, sugar and phenolic compounds

Question 4

What is the percentage of water in wine?

Answer 4

80-90% and primarily from the grapes themselves. Although uncommon, small amounts of water are added incidentally during winemaking when alcohol (potential/actual) or phenolic compounds are beyond desired levels

Question 5

What is the main alcohol component of wine?

Answer 5

Ethyl alcohol, also refereed to as ethanol

Question 6

What does “weight” or “body” refer to?

Answer 6

Alcohol content

Question 7

Slow, thick-appearing “tears” or “legs” in the glass after the wine is swirled is caused by…

Answer 7

High levels of alcohol

Question 8

Acids usually make up between ____ and ____ of a wines volume.

Answer 8

0.5% and 0.75%

Question 9

What are the principal acids found in wine? Distinguish which are grape acids and fermentation acids.

Answer 9

Grape acids: tartaric, malic, [citric] and [succinic]

Fermentation acids: lactic, acetic and succinic

Question 10

Tartaric Acid

Answer 10

Most prevalent of the acids found in both grapes and wine. Strongest in terms of pH

Question 11

Malic Acid

Answer 11

Sharp tasting acid typically found in underripe grapes and cool-climate grapes

Question 12

Citric Acid

Answer 12

Not usually considered a normal component of grapes and exists in minute qualities measured by specialized equipment. Sometimes added to increase the total acidity in wine which is generally unsuitable for quality wines

Question 13

Lactic Acid

Answer 13

Not found in grapes. Is created in wine by lactic acid bacteria (optional winemaking process known as malolactic fermentation). Tends to make wines softer and smoother and provide a creamy texture (sometimes buttery aroma)

Question 14

Acetic Acid

Answer 14

Acid found in most vinegars. Is volatile, readily evaporates and joins the aromas of the wine, adding complexity to the wines bouquet (typically red wines). High concentrations, caused by the chemical reaction between ethanol and oxygen, are harmful and can make the wine undrinkable.

Question 15

Succinic Acid

Answer 15

Minor component in grapes and a by-product of normal fermentation. Has a sharp, slightly bitter and slightly salty flavor.

Question 16

What is the measurement range of pH in wine? What does that mean for acidity in the wine.

Answer 16

2.9 and 3.9 logarithmic pH. Lower numbers on the scale are more acidic.

Question 17

What is the % of sugar found in grapes at harvest? What are the sugars?

Answer 17

15%-28%. Glucose and Fructose

Question 18

What are the phenolic compounds found in wine?

Answer 18

Anthocyanins, flavonols, tannins, vanillin, and resveratrol.