D1.C14. Maturation Flashcards
How are the young fruity wines like New Zealand Sauvignon Blanc or Veneto Pinot Grigio kept after the end of fermentation?
They are stored in vessels that are impermeable to oxygen, such as those made from stainless steel, and kept protected by use of SO2 and/or blanketing with inert gas to retain primary fruity aromas.
How long are the young fruity wines like New Zealand Sauvignon Blanc or Veneto Pinot Grigio kept after the end of fermentation?
They are likely to be finished and packaged shortly after the end of fermentation. But some producers may prefer to store them in bulk and bottle them when an order from the customer has been placed or may choose the ship the wine in bulk
What are the advantages of storing the wine as bulk?
- Gives flexibility: depending on demands it can be packaged with different labels, sold in bulk or blended with other wines
- It is often more efficient in terms of winery space than the same volume of wine kept in stacks of bottles
- Wine labels are less likely to get dirty or become ruined (e.g. by humidity)
What are the key factors that may have an influence on the wine during maturation?
- Oxygen
- New wood
- Yeast lees
During which stage of winemaking process blending is done?
It may take place at any point in the winemaking process, however it is often carried out at the end of maturation process
What is the effect of oxidation on the aromas of the wine?
Generally, oxidation leads to a gradual reduction in many primary aromas and a development of tertiary aromas, such as dried fruits and nuts
What is the effect of oxidation on the color of white wine?
With exposure to oxygen, white wines become darker, gradually becoming gold and then brown
By which mechanism, exposing a young red wine to oxygen can result in greater colour stability and intensity?
Anthocyanins bind with tannins, which, in turn, protects anthocyanins from being bleached by SO2 additions or adsorbed by yeast lees
What is the effect of oxidation on the tannins of the wine?
Softening of the tannins
Why is red wines are often matured for longer than white wines?
Because red wines can withstand a higher level of oxygen exposure than white wines before any signs of oxidation are apparent due to their higher content of anti-oxidative phenolic compounds (e.g. tannins)
What is the traditional, and still commonly used, method of gaining a slow, gradual exposure to oxygen?
To store the wine in small wooden vessels
By which mechanisms, do the wooden vessels provide oxygen to the wine?
- Some oxygen is released from the pores in the vessel within the first month that the vessel is filled with wine
- A very small amount of oxygen also continues to pass through the gaps between the staves and the bung hole
- However, the times when the wine is most exposed to oxygen in this process is during any transfer of the wine, such as during racking, lees stirring or topping up in which the bung is removed
Why is some wine is generally lost during the maturation process 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
Why evaporation from small wooden vessels is more?
They have a larger surface to volume ratio
Why do topping up lead to more oxygen exposure in smaller vessels, compared to larger vessels?
The amount of oxygen that enters the barrel relative to the volume of wine is also larger for small vessels compared to larger vessels
What is micro-oxygenation?
Bubbling oxygen through wine
In which kind of tanks and for how long, is micro-oxygenation performed?
Micro-oxygenation is generally carried out in stainless steel tanks for a number of months post alcoholic fermentation
Micro-oxygenation is used for the production of which kind of wines?
Initially, it was generally used on inexpensive and mid-priced wines; however, a growing number of wineries producing premium and super-premium wines are using the technique
What are the advantages of micro-oxygenation?
- Increase color stability
- Soften tannins
- Improve texture
- Reduce unripe, herbaceous flavours
- Provides the effects of gentle exposure to oxygen more quickly than barrel ageing without needing expensive barrels
- 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
Why care must be taken while using micro-oxygenation?
Because, increasing oxygen levels in the wine can provide a more favourable environment for spoilage organisms such as acetic acid bacteria and Brettanomyces
What are the ideal storing temperatures for white and red wines?
- White wines tend to be stored at 8–12°C
- Red wines are stored a little warmer at 12–16°C
What is the effect of temperature on maturation process?
Stable, cool temperatures give a slower maturation than warm temperatures
Although higher temperatures speed up maturation, why do winemakers prefer stable cool temperatures to give a slower maturation?
Warmer temperatures do not simply speed up the ageing. The temperature determines what reactions can occur and how quickly various reactions will occur.
Unfortunately, many of the reactions that benefit from warm temperatures are undesirable in terms of wine quality
Which conditions in the cellar increase the rate of wine loss?
- Warm temperatures
- Low humidity
Why is increased rate of wine loss during maturation not undesirable?
- It reduces the volume of the wine to sell
- Barrels need topping up more often
+ Greater cost through labour requirement
+ Risk of oxidation is increased
Humidity under what per cent cause water to be lost at a greater rate than alcohol and, over time, this can lead to a higher alcohol concentration?
70 %
What is the role of wood in maturation?
- Permits a slow exposure to oxygen
- Newly-made wood vessels also contain various extractable compounds, including tannins and many aroma compounds
