The Role of Oxygen in Maturation

Question 1

Why are wines like Sauv Blanc or Pinot Grigio stored in SS tanks?

Answer 1

To protect them from oxygen.

Question 2

During maturation, what effect does oxygen play on the different types of aromas?

Answer 2

Primary aromas reduce.

Tertiary aromas increase.

Question 3

What influence can oxygen have on the color of red wine?

Answer 3

Exposing a young red wine to oxygen can help fix the color and protect against SO2 bleaching.

Over time, exposure to oxygen will make the color fade and turn brown.

Question 4

What influence does exposure to oxygen have on the color of white wine?

Answer 4

White wines become darker, from gold to brown.

Question 5

What effect does oxygen have on tannins in red wine during maturation?

Answer 5

Oxygen results in the softening of tannins over time. This may be linked to anthocyanin and tannin bonding.

Question 6

What affects the speed of oxidation of a wine?

Answer 6

• amount of oxygen exposure
• compounds in the wine
• temperature
• many other factors

Question 7

Why do red wines oxidize more slowly than white wines?

Answer 7

Higher levels of antioxidative compounds tannins, than white wines.

Question 8

How is oxidation apparent in deliberately oxidized wines?

Answer 8

• brown color
• lack of fresh fruit aromas and flavors
• flavors of nuts and dried fruits

Question 9

How does oxygen enter the wine during maturation in oak vessels?

Answer 9

• some oxygen is released from the pores of the wood during the initial month after filling
• a small amount of oxygen passes through the bung hole
• during transfer or racking of the wine

Question 10

Why do barrels often need topping up?

Answer 10

Water and alcohol impregnate the wood, and then evaporate. Topping up is required to avoid excess ullage and excessive oxidation.

However, introduction of wine into the barrel results in small amounts of oxygen entering the wine.

Question 11

Why is oxygen exposure greater in small barrels?

Answer 11

Smaller barrels have greater wood to wine ratio.

Wine evaporates more quickly.

Small barrels require more frequent topping up. Quantity of oxygen added with the top up is relatively larger per volume of wine in a smaller barrel than a large one.

Question 12

What is a cheaper option than barrels, for introducing oxygen to a wine during maturation?

Answer 12

Micro-oxygenation

Question 13

Define micro-oxygenation.

Answer 13

The bubbling of oxygen through wine.

Question 14

How is micro-oxygenation performed?

Answer 14

Carried out in SS tanks for a number of months post-fermentation.

Question 15

Styles of wine using micro-oxygenation?

Answer 15

Generally used on inexpensive to mid-priced wines.

Growing number of premium and super-premium wines using this technique.

Question 16

What positive effects is micro-oxygenation thought to have on red wines?

Answer 16

• stabilizes color
• softens tannins
• improves texture
• reduces presence of unripe flavors

Question 17

Why must care be taken with micro-oxygenation techniques?

Answer 17

Increased oxygen in the wine may encourage spoilage organisms.

Relatively new technique, and so it is yet to be seen how it affects wine during long term aging.

Question 18

Why are temperature and humidity important in the storage facilities of maturing wines?

Answer 18

Cool temps slow the rate of oxidation and evaporation.

Humidity is controlled to slow evaporation to reduce volume losses and alcohol rises (as water evaporates more quickly in low humidity)/