14. Maturation Flashcards
Why might a producer choose to store their wine in bulk?
Some winemakers producing young, fruity styles of wine choose to bottle only when an order from a customer has been placed, or they choose to ship the wine in bulk.
What is the role of oxygen in maturation?
- Oxidation leads to a gradual reduction in many primary aromas and a development of tertiary aromas.
- Oxidation can influence the colour of wines
- For red wines; oxidation can lead to the softening of tannins
What happens when a young red wine is exposed to oxygen?
Exposing a young red wine to oxygen can result in greater colour stability and intensity. In this reaction, anthocyanins bind with tannins, which, in turn, protect anthocyanins from being bleached by SO2 additions or adsorbed by yeast lees (i.e. the anthocyanins are not held as a thin layer on the lees, which would reduce the colour of the wine). This is particularly important for light-coloured red wines
After much more prolonged exposure to oxygen, all red wines gradually become paler and browner.
What are the main factors influence the speed of oxidation in maturation?
- The amount of oxygen exposure
- The compounds in the wine
- Temperature; warm temperatures increase oxidation
How does oxygen enter wooden vessels during the maturation stage?
- Some oxygen is released from the pores of the vessel within the first month it is filled
- A very small amount of oxygen continues to enter through the gaps between the staves and the bung hole
- The times when the wine is most exposed to oxygen in this process is any transfer of the wine, such as racking, lees stirring, or topping up in which the bung is removed.
How does evaporation occur when maturing wine in wooden vessels?
Water and alcohol in liquid form impregnate the wood. Within the staves of wood, the water and alcohol turn to vapour (evaporate) and diffuse, along the concentration gradient, to the air outside
the vessel.
This leads to a gradual concentration of the other components of the wine
Why are wines maturing in smaller barrels frequently topped up?
- Small vessels, such as barrels, have a large surface area to volume ratio, increasing the rate at which wine is lost.
- This means that barrels frequently need to be topped up with more wine to keep them full (and hence avoid ullage and excessive oxidation).
- The frequency of topping up leads to more oxygen exposure in these vessels than in much larger vessels.
What is micro-oxygenation?
Micro-oxygenation involves bubbling oxygen through wine. The dose of oxygen is typically in units of mg/L per month. Micro-oxygenation is generally carried out in stainless steel tanks for a number of months post alcoholic fermentation.
Why might a winemaker choose to micro-oxygenate their maturing wine?
Winemakers may use micro-oxygenation in stainless steel tanks as a cheaper alternative to wooden vessels.
What are the advantages of micro–oxygenation?
- Micro-oxygenation is thought to increase colour stability and intensity, soften tannins, improve texture and reduce the presence of any unripe, herbaceous flavours.
- Additional benefits are that it provides the effects of gentle exposure to oxygen more quickly than barrel ageing without needing expensive barrels.
- The rate of oxygen exposure can be controlled much more tightly than it could be in a barrel.
- If used in conjunction with oak alternatives (such as chips or staves), it can also help to integrate the influence of the oak.
What are the disadvantages of micro-oxygenation?
- The increasing oxygen levels in the wine can provide a more favourable environment for spoilage organisms such as acetic acid bacteria and Brettanomyces
- New technique. therefore research into which grape varieties or types of wines benefit from micro-oxygenation and how wines made by micro-oxygenation age in bottle over the long term (and whether there is any difference compared to the same wine matured in barrel) is lacking.
At what temperatures are wines typically stored during maturation?
Red wines: 12-16°C (they are less susceptible to the effects of oxidation)
White wines: 8-12°C
What conditions increase the rate of evaporation in wooen vessels during maturation?
Low humidity and warm temperatures
What is the risk of low humidity in the cellar during maturation?
Low humidity and warm temperatures increase the rate of evaporation of water and alcohol in wine maturing in wooden vessels.
Low humidity (under 70%) can cause water to be lost at a faster rate than alcohol, which over time, can lead to a higher alcohol concentration in the wine. This can throw the wine out of balance.
How does the age of a barrel influence it’s contribution of aromas to a maturing wine?
New wood contains various extractable compounds. Each time the barrel is used, the amount of extraction decreases because fewer extractable compounds remain. (A barrel loses about 50 per cent of its new oak flavours during the first year of use.) By the time the vessel is on its fourth usage, it will contribute very little at all (but still allow ingress of oxygen).
Why do smaller barrels contribute more aromas than larger barrels?
Small vessels, such as barriques (225 l), hold a relatively small volume of liquid compared to the surface area of the vessel. This means that any extraction from the wood and exposure to oxygen is greater in small vessels than in large vessels, such as foudres.
Why is oak the most common type of wooden vessel used for maturation?
It can easily be shaped into a barrel and, importantly, makes containers that are watertight. Oak is also prized for its positive effects on the aroma/flavour and structure of the wine. Different species of oak have different characteristics, but it is possible for the same species of oak to show different characteristics depending on where it is grown.
What species of oak are most popular for maturation?
European (French, Hungarian, Russian, Slavonian)
American
What are the main differences between American an European oak>
- One of the key differences is that American oak has been found to contain much higher levels of lactones, which give aromas of coconut.
- In general, American oak tends to impart a greater intensity of aromas/flavours than European oak, which is often said to be subtler.
- By contrast, European oak tends to impart more tannin.
- Tighter grain (slower growth of the tree).
- European oak barrels (€600–€1200) is much more expensive than American oak barrels (€300– €600);
Why are European oak barrels more expensive to produce than American oak barrels?
The cost of American oak barrels tends to range from €300– €600, whereas that for French oak barrels tends to range from €600–€1200.
European oak must be split to create staves, whereas American oak can be sawn. The ability to saw American oak means more vessels can be made from the same amount of oak.
American oak also grows significantly quicker than European oak.
How does the tightness of the grain in oak barrels influence wine? Example?
Wood with a tight grain slows down the extraction of compounds compared with more coarsely grained wood, and can alter what particular compounds are most extracted.
For example, Hungarian oak, which tends to have a tight grain, is gaining popularity in New York State as an option that allows very gradual extraction of oak aroma compounds and tannins for their red wines so that they are not dominated by oak-derived characteristics.
