11. Wine Components

Question 1

What are the 7 main components of wine?

Answer 1

1) water
2) alcohol
3) acids
4) wine aromatics
5) residual sugar(s)
6) glycerol
7) phenolics

Question 2

How much of wine is water?

Answer 2

85%

Question 3

What is the predominant alcohol in wine?

Answer 3

Ethanol – formed during fermentation

Question 4

What are the principal acids in wine?

Answer 4

Tartaric and malic – both come from grape itself

Question 5

What acids are produced during malolactic fermentation?

Answer 5

Lactic and acetic

Question 6

What is the link between total acidity and pH?

Answer 6

Linked but not correlated – a wine with high acidity would normally have a high pH and vice versa

Question 7

How is acidity measured and what is the normal range?

Answer 7

• in “total acidity” and expressed “g/l” in tartaric acidity

- normal range is 5.5-8.5 g/l

Question 8

How is pH measured and what does a low pH mean for the wine?

Answer 8

• measured on logarithmic, inverse scale
• 3-4 is typically the range
• low pH increases microbial stability, increases effectiveness of SO2, gives red wines a bright colour and enhances aging

Question 9

What are examples of aromas from the grapes? (2)

Answer 9

1) methoxypyrazines

2) rotundone

Question 10

What are methoxypyrazines?

Answer 10

Occur in SB and give grassy, green pepper aroma

Question 11

What is rotundone?

Answer 11

Produces pepper aroma in Gruner and Syrah

Question 12

What are aroma precursors?

Answer 12

Compounds that are not themselves aromatic but are building blocks which become aromatic during fermentation (ex. thiols and terpenes)

Question 13

What are thiols?

Answer 13

Aromatic compounds released during fermentation

Question 14

What are terpenes?

Answer 14

Another aromatic compound released during fermentation giving floral and fruity aromas (ex. grapey in Muscat)

Question 15

What are esters? What is the most common?

Answer 15

• aromas formed through action of yeasts and fermentation process (responsible for fresh and fruity aromas)
• the most common is isoamyl acetate (banana, pineapple. apple)

Question 16

What is acetaldehyde?

Answer 16

• aroma occurring in wine due to oxidation of ethanol

- masks fruit aromas and regarded as fault in most wines (fino sherry)

Question 17

What is diacetyl?

Answer 17

• aroma produced during MLF

- contributes buttery aroma

Question 18

What are 2 examples of aromas from other sources?

Answer 18

1) vanillin - gives aromas of vanilla, comes from aging wine in new oak
2) eucalyptol - comes from waxy layer of skins absorbing from nearby eucalyptus trees

Question 19

What are the 4 components of Vinente Ferreira’s model for wine aromas?

Answer 19

1) compounds common to all wine (aromas produced by fermentation – usually sweet, alcoholic, fruity)
2) impact aromas (specific aromas that can be recognized – ex. rotundone)
3) contributory aromas (aroma compounds that are below their normal individual perception but make contribution when thy are with other certain compounds found in wines – ex. vanillin)
4) nonvolatile wine matrix (nonvolatile components of wine that affect the way the aromatic compounds are sensed)

Question 20

What are the EU classifications for sweetness levels?

Answer 20

1) dry = up to 4 g/l
2) medium-dry = between 4-12 g/l
3) medium-sweet = between 12-45 g/l
4) sweet = at least 45 g/l

Question 21

What is glycerol?

Answer 21

• most abundant part of wine after water and alcohol
• derived from sugars in grapes
• contributes to texture of wine and perception of fullness of body

Question 22

What are phenolics?

Answer 22

Includes anthocyanins and tannins