Maturation Flashcards
What factors have an influence on wine during the maturation period?
1) oxygen
2) new wood
3) lees
How does oxidation affect wine?
1) a gradual reduction in primary aromas
2) a development of tertiary aromas such as dried fruits and notes
3) white wines become darker
4) anthocyanins bind with tannins which protect the anthocyanins from being bleached by SO2 or held on the lees (exposing a young wine to oxygen leads to greater color stability and intensity)
5) prolonged exposure to red wines gradually become paler and browner
6) softening of tannins
Speed of oxidation
Influenced by:
1) amount of oxygen exposure
2) compounds in the wine (reds anti-oxidative phenolic compounds)
- reds often matured 12-24 months
- whites 6-12 months
3) the temperature (warm temps increase oxidation)
Methods of oxygen exposure
1) wooden vessels
2) micro-oxygenation
Wooden Vessels and oxygen
- method of slow, gradual exposure to oxygen is storage in small wooden vessels
- a small amount of oxygen is released from the vessel in the first month and a very small amount passes through staves and the bung hole
- the most exposure occurs during racking, lees stirring, or topping up
- some wine is lost as the water and alcohol impregnate the wood then evaporate (small barrels =more evaporation, more topping up needed)
Micro-oxygenation
- a cheaper alternative to barrels
- bubbling oxygen through wine, generally carried out in stainless steel for a number of months following alcoholic fermentation
- measured in units of mg/L per month
- historically inexpensive or mid-priced wines but now seen at every price level
Pros:
1) increases color stability and intensity
2) softens s=tannins
3) improves texture
4) reduced any unripe, herbaceous flavors
5)can be controlled tightly
Cons:
1) creates a favorable environment for spoilage organisms such as acetic acid bacteria and brettanomyces
Temperature and humidity
- wines are matured in stable, cool temps to slow the rate of oxidation and the threat of spoilage organisms
- white wines at 8-12C / 46-54F
- red wines at 12-16C / 54-61F (less susceptible to oxidation)
- temperature also impacts the rate of the various chemical reactions in wine, warm = undesirable
- low humidity increases the rate of oxidation and wine loss, reducing the volume to sell and increasing the need for topping up
- humidity under 70% causes water to be lost at a faster rate than alcohol, leading to higher abv
Role of Wood in maturation
1) age of the vessel
- a new barrel has the most extractable compounds, loses 50% in first use, by 4th usage contributes very little
2) size of the vessel
- small 225L extract more wood/oxygen than large vessels like foundres (1000L)
3) type of wood
- EU and US oak give vanillin but US oak has more lactones giving coconut and EU oak gives more tannin
- oak grown in cooler climates have tighter grains and slow down extraction
4) method of production
- staves need to be dried, typically outside for 2-3 years, to lower humidity, reduce bitterness and increase aroma compounds (cloves)
- toasting barrels is needed to shape them and transform tannin and aroma compounds (light, medium, heavy) with the latter giving the most spice, caramel, roasted nuts, char, and smoke
5) length of time in wood
- longer = greater extraction and diversity of wood-derived aroma compounds
6) cost
- mid-priced to super-premium wines
- small batch
- increases labor due to need for monitoring and intense cleaning
- adds time to the process
Oak alternatives
Oak chips and staves are much cheaper and can be used alongside micro-oxygenation for the desired stylistic effect
Lees
The sediment that settles at the bottom of a wine vessel made up of dead and dying yeast, bacteria, grape fragments, precipitated tannins, nutrients, and other insoluble compounds
Gross Lees
The sediment that forms within 24 hours after the end of fermentation, made up of larger heavier particles
Fine lees
The smaller particles that settles more slowly when they gradually form a sediement
Racking
The process of transferring wine from one vessel to another with the aim of removing sediment from the wine. The first racking to remove gross lees and subsequent rackings for fine lees or any other solid material that has fallen over time. Wine is removed from the valve near the bottom of the vessel and pumped/poured into a new, clean vessel. This increases oxidation especially if allowed to splash.
How do lees form and what do they contribute
The yeast cells die very slowly and break down (yeast autolysis), releasing compounds that contribute flavors, body, and texture
- some of these compounds bind with phenolic compounds, reducing color and softening tanning
- some bind with certain extractable components of the wood, tannins and flavors, reducing astringency and modifying flavors
- yoghurt, dough, biscuit, toasted bread
- protein stabalisation in whites (anti-haze)
- helps control oxidation, lowering the need to SO2
- too thick a layer can produce reductive sulfur compounds (smoke to rotten egg)
- they provide nutrients for microbes, assisting the growth of lactic acid bacteria (for MLF) and spoilage organisms like brettanomyces
- can add cost for storage time and labour for monitoring
Blending
Refers to the mixing together of two or more batches of wine. Can take place at any time during the winemaking process but is most often carried out after stabilization (in case problems arise) and just before finishing and packaging. Small scale trials will be done beforehand.
Blending involves combining what aspects of wine?
1) grape varieties
2) locations
3) grape growers or businesses that sell grapes
4) vintages
5) treated differently in the winery
6) aged differently
Often depends on local legislation
Why blend?
1) balance
2) consistency
3) style
4) minimize faults
5) complexity
6) minimize faults
7) volume
8) price
