D1: Maturation

Question 1

Generally oxidation leads to a gradual reduction in many primary aromas and a development of _____

Answer 1

tertiary aromas such as dried fruits and nuts

• if well developed the this can enhance the quality of a wine
• if not this can result in reduction of quality

Question 2

Additionally oxidation can influence the colour of wines:

Answer 2

1) white wines becomes darker, gradually becomming gold and then brown

2) young red: can result in greater stability and intensity:
- - anthocyans binds with tannins
* this protects anthocyanins from being absorbed by yeast lees or bleached by so2 additions
* * important for ligt coloured red wines such as PN

—- after much more extensive ageing, red wines gradually become paler and browner

Question 3

For red wines oxidation also seem to result in the ____ of tannins.

Answer 3

Softening

• • this may be positive for quality
• – not yet well understood, but may at least in part be linked to anthocyanin and tannin bonding

Question 4

The speed of oxidation is influenced by the amount of oxygen exposure, the compounds in the wine and temperature, among other factors.

Answer 4

1) wine fully exposed to air (and hence oxygen): will generally oxidise quicker than when oxygen exposure is more gradual (kept in a large oak vat)

2) red wines can withstand a higher level of oxygen exposure than whites before any signs of oxidation are apparent due their higher content of anti oxidative phenolic compounds (eg tannins)
* this is why red wines are often matured longer than whites with 12-24 months pre bottling maturation and 6-12 for white

3) warm temp increasing the speed of oxidation reactions

Question 5

A high level of oxidation is a key part of the style of some wines (such as oloroso sherry)

Answer 5

The oxidation evident from the brown colour of the wine and lack of fresh fruit on the palate replaced by nuts and dried fruits

• in this case the iwne is stored in barrels that are not filled up to the top allowing oxygen to the headspace of the barrel (ullage)

— more commonly for unfortified red and white wines, the exposure to oxygen is limited and has much slower and subtler effect

** too much oxidation in these wines is usually seen as a fault

Question 6

what about wooden vessels and oxidative maturing ?

Answer 6

1) some oxygen is released from the pores of the vessel within the first month that the vessel is filled with wine
- - a very small amount is also passing through the gap between the staves and the bung hole

2) the time when the wine is the most exposed to oxygen is during transportation (racking, lees stirring or topping up when the bung is removed)

Question 7

Some wine is generally lost during the maturation process in wooden barrels.

Answer 7

Water and alcohol in liquid form impregnate the wood
– within the staves of wood the water and alcohol turn to vapour (evaporate) and diffuse (verspreid) along the concentration gradient to the air outside the vessels

• this leads to a gradual concentration of the other components of the wine
• • small vessels evaporate more wine than large
• – also the topping of small vessels leds to more oxygen exposure then in larger vessels
• —- the amount of oxygen that enter the barrel relative to the volume of wine is also larger for small barrels
• leading to quicker (but not extreme) oxidation

Question 8

Maturing wine in barrels is costly, therefore micro oxygenation is a replacement technique:

Answer 8

1) bubbling oxygen into the wine
2) the dose is typically in units of mg/l per month
3) generally carried out in stainless steel tanks for a number of months post alcoholic fermentation
4) generally for inexpensive and mid priced wines (however now also on premium)

Question 9

What does micro oxygenation do to the wine ?

Answer 9

1) increases colour stability and intensity, soften tannins, improve texture and reduce the presence of any unripe herbaceous flavours
2) it provides the effects of gentle exposure to oxygen more quickly than in wooden barrels
3) the rate of oxygen can be controlled much better than in oak barrels
4) if used in conjunction with oak alternatives (staves, chips) it also can integrate the influence of the oak

Question 10

However, care must always be taken because the increasing oxygen levels in the wine can provide a more favourable environment for spoilage microbes such as

Answer 10

Acetic acid bacteria and brettanomyces

Question 11

Wines are usually matured in stable cool temp to slow down the rate of oxidation and other reactions and lower chance of microbial spoilage.

Answer 11

1) whit wines: 8-12°c 46-54°f
2) red: 12-16°c 54- 61° f
* as they are less susceptible to the effects of oxidation

Question 12

Stable cool temp give a slower maturation than warm temp 20°c and above due :

Answer 12

the effect of chemical reactions hat happens between the different compounds in the wine

Temp also determines what reactions can occur and how quickly various reactions will occur
* unfortunately, many of the reactions that benefit from warm temp are undesirable in terms of wine quality

Question 13

Low humidity and warm temperatures increase the rate of wine loss.

Answer 13

this is undesirable as it reduces the volume of wine to sell

also:
- barrels need to be topping up more (greater cost of labour)
- risk for oxidation harmful for quality

Conditions of low humidity approximately 70% causes water to be lost at greater rate than alcohol and over time this can lead to a higher alcohol concentration in the wine, which in many instances may be seen as undesirable

• • for these reasons, wines are usually matured in cool cellars of constant temperature and humidity
• • temp and humidity control systems are common in modern cellars
• — many traditional cellars where build underground for this same reason

Question 14

wooden vessels permit a slow exposure to oxygen during the wine’s maturation. newly made vessels contains various extractable compounds, including tannins and many aroma compounds, which can have a significant influence on the wine. the level and type of extracted from vessels depend on the following features of wooden vessels:

Answer 14

1) age of the vessel
2) size of the vessel
3) type of wood
4) production of vessel

Question 15

Age of the vessel:

Answer 15

1) new wood contains various extractable compounds
- - each time a barrel is used the amount of extraction decrease
* a barrel loses about 50% of its new oak flavours during the first year of use

2) after four years of use the barrel will contribute very little, but still allow ingress of oxygen
3) the flavours of new oak can clash with aromatic grape varieties
4) where new oak is used it is typical as a proportion of the blend with wine that is stored in pre used barrels

Question 16

Size of the barrel:

Answer 16

Small vessels, such as barriques 225l 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 large vessels such as foudres

Question 17

Type of wood:

Answer 17

1) most commonly is oak:
- can easily be shaped into a barrel
- - makes containers that are watertight
- - positive effects on aroma flavour of the wine
- — different species of oak can have different characteristics
* most are from european oak (french, also hungarian, russian or slavonian, also american

• both eu and amerikan have significant levels of vanilin
• • american have higher levels of lactones which gives coconut aromas to the wine
• – in general american oak haves an greater intensity of aromas/ flavours than european oak which is often subtler
• – european has more tannin

2) The production process for barrels from eu oak is more expensive than american (french vessels more expensive than american)
* american: 300€ -600€
* french: €600-1200
- - eu oak has to be split to create staves
- — american oak can be sawn
* ** american oak also grows significantly faster than european oak

3) thightness of the grain:
- more thightly grained wood: result of slower growth of tree
- - ex oak in continental climates grow slower (russia hungary) so thightes grains
- — wood with tight grain slow down extraction of aromas and flavours
* hungarian oak is gaining popularity in NY because it adds slowly tannins and gradual aroma compounds to their wines who are generally medium in body, alcohol and tann and flavour intensity (so no dominant oak characteristics

4) also chesnut wood, cherry and acacia

Question 18

Production of the vessel:

Answer 18

1) wood needs to be seasoned: outside and can dure 2-3 years
- - lowers the humidity level
- - reduces bitter flavours
- - increase aroma compounds (such as those who give cloves)

2) heating the staves for bending
- - also transform the tannin and aroma compounds in the oak
- - temp and length of heat exposure is refered as toasting level
* light, medium or heavy toasted
* contributes notes of spice, caramel, toffee roasted nuts char and smoke
* * many are more pronounced at heavy toasting
- —- many winemakers let make the barrels to an house style (housestyle)

Question 19

The level and type of compounds extracted from the vessel will also depend on the length of time that the wine is aged in the vessel:

Answer 19

1) the longer the more extrction of compounds and greater exposure to oxygen
2) some extraction is greater at different stages in the maturation process thats why it is not completely constant

*** size of the vessel, type age of wood and environment will also affect the extraction of aromacompounds

Question 20

Why is barrel maturation expensive ?

Answer 20

1) expensive to buy
2) small barriques dont hold much wine so a lot of barrels are needed
3) monitoring and performing winemaking options as lees stirring is dificult in so much barrels
4) spoilage microbes like brettanomyces like to live in wood so meticulous cleaning and sanitation is needed
5) slow process, the wine can be stored for 1-2 years or even longer
6) in most cases the wine is sold when its packaged and reaches the market

Question 21

For expensive reasons the winemaker may choose to use alternative to barrels:

Answer 21

1) oak chips and staves
- - can be attached in stainless steel vessels or concrete vessels
- — chips are generally in a sack whos left to soak in the vessel
- — also different species available and toasting levels (complexity)
2) micro oxygenation

Question 22

Lees describes the sediment that settles at the bottom of a wine vessel. it is made up:

Answer 22

• dead yeast
• dying yeast and bacteria
• grape fragments
• precipitated tannins, nutrients and other insoluble compounds

Question 23

the sediment that forms quickly after the end of fermentatin (24 hours) is called gross lees:

Answer 23

This is made of larger heavier particles

— smaller particles settle down more slowly called fine lees

Question 24

the lees may be removed by removed by racking

Answer 24

1) the first after ferm removes gross lees
2) subsequent peridic racking helps to manage the levels of fine lees

—- some winemakers will choose to keep the wine in contact with the fine lees, this has several effects

Question 25

after ferm the yeast cells will very slowly die and break down (autolysis)

Answer 25

releasing compounds that contribute flavours, body and texture to the wine

1) some of there compounds react with the phenolic compounds of the grape reducing colour and softening tannins

2) compounds from the lees also bind with certain extractable components of the wood
- - wood tannins
- — reduce astringency and modify the flavours of the wood

3) a range of compounds are released by the yeast and these compounds can react with aroma compounds already in the wine

4) in white wines are the effects of the lees generally more significantly
- - yoghurt lie, dough like biscuity of toasty however these can be very subtle

Question 26

lees ageing also helps the stabilisation of the wine against unstable proteins that can cause hazes

Answer 26

generally the effect of groos lees are more significant than fine lees

Question 27

Lees protect the wine from oxygen,

Answer 27

Helping to maintain a slow, controlled oxidation during maturation and lowering the need to use so2 during this time

1) however, a too big layer of gross lees can produce volatile, reductive sulfur compounds
- - at low levels these aromas can add complexity and aromas like struck match and smoke
- —- if not controlled it can lead to rotten egg aromas that comes from higher level of hydrogen sulphide (reduction)

2) lees can provide nutrients for microbes:
- - good for lactic acid bacteria
- – bad for spoilage microbes like brettanomyces

Question 28

Stirring the lees=

Answer 28

battonage

Question 29

Lees ageing may increase the time the wine is sold so can increase the final cost of the wine:

Answer 29

1) they need to bo monitored regularly and may be stired, which incurs labour cost
2) can also add cost due the labour for opening a lot of vas and stirring them

Question 30

how about racking ?

Answer 30

1) transferring wine from one vessel to another with the aim of removing sediment from the wine
- - this sediment may be gross lees, fine lees or other material

• the wine is removed from the original vessel through a valve (klep) near the bottom of the vessel (above the top of the sediment) and pumped and poured out into the top of a new, clean vessel

2) racking is an oxidative process: some will increase the oxidation by deliberately splashing the wine
- – feasible to protect the wine from oxygen during this process (aromatic or fruity wines) by using pressure from inert gas to push the wine out through a hose into a new vessel which would have been flushed with an inert gas

3) racking may be carried out once or several times during the maturation process

Question 31

Blending can take place at any time during the winemaking process but usually before bottling, it may involve combining wines:

Answer 31

1) from different grape varieties
2) different locations (different vineyards, regions or even countries)
3) from different grape growers
4) different vintages
5) threatened different in the winere (wood, …)
6) that have been treated equally in the winery but are in different vessels for logistical reasons

Question 32

There are several key reasons for blending wines:

Answer 32

1) balance
2) consitency
3) style
4) complexity
5) minimise faults
6) volume
7) price

Question 33

What about blending for enhancing the balance ?

Answer 33

1) increase or moderate the levels of certain characteristics of the wine to produce a wine that is better balanced and in this way enhance quality

ex: batch of warmer vineyard that has been picked late can be blended with a batch of wine from cooler vineyard to finetune the acidity levels
ex: merlot provides body and ripe, plummy fruit to a blend wit CS which when not ripe can be too astringently tannic on its own

Question 34

Why blending for consistency ?

Answer 34

Significant variation among bottles of a single product in a single vintage is usually seen as a fault
* blending can be necesarry to ensure a certain volume of consistent product

• some winestyles needs consistency over different years (sherry, non vintage sparkling wines)
• • also many inexpensive wines where th econsumer may not expect nor accept significant vintage variation

Question 35

Why blending for a certain style ?

Answer 35

even with different vintages some winemakers want their own housestyle

Question 36

blending adds complexity:

Answer 36

The blending of two or more parcels of wine may lead to a greater range of flavours and in this way enhance the complexity and quality of the final wine

Question 37

Blending also minimise faults:

Answer 37

ex: if one barrel is showing significant volatil acidity, that wine may be sterile filtered and blended into a larger volume of un faulty wine to lower the concentration and sensory perception of acetic acid

Question 38

Blending for ensuring a certain volume:

Answer 38

1) for areas with small vineyard holdings
- - blend wines from different vineyards
2) bad vintages: grapes need to be bought for a viable volume

Question 39

blending affecting the price:

Answer 39

the wine that is made need to be profitable at a certain price point: thats why sometimes chardonnay is blended with trebbiano or semillon because the latter two are less expensive

also not blending for reasons ‘single vineyard’ certain character blabla

Question 40

The blending process:

Answer 40

1) generally starts with blending trials using measuring cylinders and small volumes of wines to distinguish the proportion of each wine in the favoured blend before conducting on a much larger scale

2) can be extremely challenging (young wines destined for long ageing
- - needs to estimate how the blend will develop in the future

3) blending is best carried out before stabilisation in case any instabilities arise from the blend
- - ex: tartrate stability is dependent on ph level and this can be altered by blending wines with different different pH levels