Role of oxygen Flashcards
(18 cards)
Why are wines like Sauvignon Blanc or Pinot Grigio stored in stainless steel tanks?
To protect them from oxygen.
During maturation what effect does oxygen play on the different types of aromas?
Primary aromas reduce.
Tertiary aromas increase.
What influence can oxygen have on the colour of red wine?
Exposing a young red wine to Oxygen can help fix the colour and protect against SO2 bleaching.
Over time, exposure to oxygen will make the colour fade and turn brown.
What influence does exposure to oxygen have on the colour of white wine?
White wines become darker, from gold to brown.
What effect does oxygen have on tannins in red wine during maturation?
Oxygen results in the softening of tannins over time. This may be linked to anthocyanin and tannin bonding.
What effect the speed of oxidation of a wine?
Amount of oxygen exposure
Compounds in the wine
Temperature
Many other factors
Why do red wines oxidise more slowly than white wines?
Higher levels of anti-oxidative compounds (tannins) than white wines.
How is oxidation apparent in deliberately oxidised wines?
Brown colour
Lack of fresh fruit aromas and flavours
Flavours of nuts and dried fruits
How does oxygen enter the wine during maturation in oak vessels?
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.
Why do barrels often need topping up?
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.
Why is oxygen exposure greater in smaller barrels?
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.
What is a cheaper option than barrels, for introducing oxygen to a wine during maturation?
Micro-oxygenation
How is micro-oxygenation performed?
Carried out in stainless steel tanks for a number of months post fermentation.
Styles of wine using micro-oxygenation?
Generally used on inexpensive and mid-priced wines Growing number of premium and super premium wines using this technique.
Styles of wine using micro-oxygenation?
Generally used on inexpensive and mid-priced wines Growing number of premium and super premium wines using this technique.
What positive effects is micro-oxygenation thought to have on red wines?
Stabilises colour
Softens tannins
Improves texture
Reduces presence of unripe flavours
Why must care be taken with micro-oxygenation techniques?
Increased oxygen in the wine may encourage spoilage organisms. Relatively new technique and so it is yet to be seen how it effects wine during long term aging.
Why are temperature and humidity important in the storage facilities of maturing wines?
Cool temperatures 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).
