D1: Specific options for white winemaking

Question 1

What is skin contact ?

Answer 1

Leaving the juice in contact with the skins to extract compounds from the skins (similar to cold soaking in red winemaking)

• when carried out on crushed white grapes: enhance the extraction of aroma and flavour compounds and precursors
• • and enhancing the texture of the wine by extracting a small amount of tannin
• — if too excessively: wine taste bitter and coarse in the mouth

Question 2

The majority of white wines are made with zero or minimal skin contact. the grapes are crushed and then pressed immediately (or whole bunches are pressed without prior crushing) this is because:

Answer 2

The principle aroma and flavour compounds of white grapes are in the pulp

1) the grapes are crushes
2) the free run juice is drained off
3) the remaining grape mass is sent to the press

• to reduce risk of oxidation and further contact between the juice and skins, the winemaker may choose to load the press with whole bunches of uncrushed grapes

Question 3

Why minimal skin contact ?

Answer 3

Typical for wines where delicate fruity flavours, minimal colour and a smooth mouthfeel are desired

• also for wines that are designed to be drunk early because
• • other wise the tannins retained due skin contact won’t have the time to soften
• also for wines where the fruit is generally underripe becuase skin contact will retain bitter flavours and astringent tannins
• slow process, requires labour and equipment
• • so less likely for inexpensive wines

Question 4

Skin contact maximise flavour extraction, so why on aromatic grape varieties?

Answer 4

They have lots of aroma compounds that can be extracted, such as riesling, gewurztraminer, viognier, muscat and SB

• also these aromatic varieties are mostly not matured in oak, so skin contact will enhance the texture

** also some winemakers believe that the technique leads to homogenisation, reducing the variations between grape varieties and different vineyards sites

Question 5

Time and temp are the 2 key factors that can influence extraction during skin contact:

Answer 5

1) Time: range from one hour to 24 hours and over with greater time on the skins leading to greater extraction of flavour and tannins

2) Temp: chilling the juice during this time reduces the rate of extraction of flavours and tannins, permitting more control and also reduces the rate of oxidation and microbial spoilage
- - including likelihood of a spontaneous fermentation
- - typically below 15°c 59°f

Question 6

The wine is usually pressed to separate the skins and the juice before fermentation begins

Answer 6

true

Question 7

What are orange wines ?

Answer 7

Wines made from white grapes that are fermented on their skins (and may undergo post fermentation maceration) without temperature control or sulfur additions.

• • often amber coloured
• this colour develops due to the oxidation of compounds extracted from the grape skins

Characteristics:
Usually dry, notable levels of tannins and taste mainly of tertiary characteristics of dried fruits and nuts

Question 8

The pressing will be as gentle as possible to avoid the extraction of unwanted compounds from the skins and seeds of the grapes, such as tannins and colour

Answer 8

true

Question 9

Usually the grapes are destemmed and crushed before loaded into the press, but:

Answer 9

also whole bunches are loaded into the press:
– reduces chance of oxidation before and during pressing, especially if inert gases such as nitrogen co2 or dry ice (carbon dioxide in solid form) are used within the press

• it is also the gentlest form of pressing, providing juice that is low in solids, tannins and colour
• • the stems also hep to break up the mass of grape skins, providing channels for the juice to drain
• this is only an option if grapes are hndharvested
• • additionally the whole bunches takup a lot of room in the press, therefore fewer grapes can be loaded within each press cycle
• • so suitable for smaller batch production of premium wines
• – less likely to be an option when making large volumes of inexpensive and mid priced wines

Question 10

If grapes are destemmed and crushed the juice that can be drained off as soon as the grapes are crushed is called the free run juice:

Answer 10

1) typically juice that is lowest in solids, tannin and colour
2) winemaker can choose to make wine only from free run juice, but missing the whole potential of the volume

Question 11

The juice that runs off through the pressing called the press juice:

Answer 11

1) at the start the juice will be similar to the free run juice, but as pressing continues and more pressure is applied, more solids, tannin and colour are extracted
2) press juice also have less sugar, acidity and typically makes wines with fuller body
3) winemaker can choose to press in fractions and may be blended later in the winemaking and maturation process
4) the last press fraction are likely to be too astringent or bitter (due the phenolic compounds from the skins, seeds or stems) and therefore will be discarted

Question 12

What is hyperoxidation?

Answer 12

Deliberately (opzettelijk) exposing the must to large quantities of oxygen before fermentation

– as they oxidise, these compounds turn the must brown

— during fermentation these compounds precipitate, returning the wine to its normal colour

• main aim: producing wines that are more stable against oxidation after fermentation

** hyperoxidation can destroy some of the most volatile aroma compounds found in the must and therefore is typically better suited to neutral grape varieties such as chardonnay

** for example hyperoxidation can reduce the level of volatile thiols and methoxypyrazines found in SB and therefore would not becarried out if an aromatic fruity or herbaceous winestyle was desired

Question 13

what is the aim of clarification ?

Answer 13

to reduce the amount of suspended solids within the must

– includes particles of grape skin, stem and seeds

Question 14

What if winemaker will generally hold solids in the wine ?

Answer 14

1) generally the proportion of solids in the must to be 0.5-2%
* some winemakers would use higher perc or not clarifying the must at all (for texture)
- - giving the must an subtle astringency (part of skins and stems will add tannins)

2) relatively high level of solids can also give extra complexity:
- low levels are good for fruity styles
- relatively high level suited for prem chardonnay
- - monitoring with care required because too much can lead to off flavours

• high solid fermentation can give reductive sulfur compounds that at low levels are desirable (struck, match, smoke) but at high levels rotten eggs
  3) small amount of solids is benefical in that it provides nutrients for yeast and over clarifying the must can lead to stuck fermentations
  4) very low levels of solid in fermentation needs also monitoring as there need to be sufficient nutrients for yeasts and maybe adding these nutrients like (DAP)

Question 15

Sedimentation:

Answer 15

1) settling: the suspended solids are left to fall over time with gravity
2) must is commonly chilled to around 4°c (39°f) to reduce the rate of oxidation and microbial spoilage and to avoid a spontaneous fermentation

3) rate depend on size of vessel
4) sedimentation times of 12-24 hrs are not uncommon

5) The clear juice is transferred to the fermentation vessel (process called racking)
- - the solids left behind after sedimentation will often be filtered by cross flow or depth filters to extract extra juice

6) cheapest in terms of equipment, but time and cost for chilling (also batch process which again cost labour and time and used for small volume production of premium wines

Question 16

Flotation:

Answer 16

1) bubbling gas up through the must
2) as the bubbles of gas rise they bring with them the solid particles, the particles are then skimmed of the top of the vessel

3) flotation speed up the rate of clarification
- - inert gas like nitrogen is used (oxygen will cause hyperoxidation

4) fining agents are required as the particles can bind easy and rise up
5) little more expensive as it requires equipment and products like nitrogen or fining agent
6) effective as it can be used for small batches or larger volumes
7) the must does not need to be chilled so less expensive

Question 17

Centrifiguration:

Answer 17

1) a machine that compromise a rapidly rotating container which use centrifugal force to separate solids from liquids
2) clarify the must quickly

3) used continuously rather than as a batch process (saves time and labour cost
- – however machine is expensive to buy

4) also increases the must’s exposure to oxygen quickly unless the machine is flushed with inert gas
5) can be used on wine as well as must

Question 18

Clarification of must: clarifying agents

Answer 18

1) Pectolic enzymes break down pectins in the must
* pectins are naturally found in plant cell walls (in jam making they are the compounds that turn liquid into gel)

** breaking down the pectins allows a more rapid separation between the liquid and the solids

2) Pectolic enzymes only aid the clarification of must, not wine
- - some fining agents can clarify the must as the wine

3) These products adds cost, but this may be justified against the time and energy saved compared to sedimentation (wine need to be chilled at low temperatures for several hours)

Question 19

Ferm temp for white wines are usually cooler than red wines:

Answer 19

This is because the volatile aroma and flavour compounds that are desired in many white wines are best produced and retained at cool temperatures (around 15°c 59°f

Question 20

in some white styles, fruity aromas are not particularly desired for example:

Answer 20

1) where oak is going to provide flavours
* in these cases the ferm temp can be slightly warmer (17-25°c / 63-77°f and sometimes higher

** this promote yeast health and avoid the production of certain esters, such as isoamyl acetate (banana like smell)

Question 21

Why are stainless steel tanks the most popular vessel for fruity floral styles like SB PG veneto ?

Answer 21

Due its ability to control temp easily and hence maintain the cool fermentation conditions needed for these styles of wine

Question 22

Concrete and old oak vats (as well as steel tanks) may be used for white wines fermented at slightly higher temperatures where maximising the fruity and floral aromas from fermentation is not the aim (some styles of chablis and white rioja)

Answer 22

true

Question 23

Small oak barrels are popular for some styles of white wines (fermentation) (premium and super premium chardonnay (due its high cost of new barrels) what are the pros and contras ?

Answer 23

1) Monitoring ferm in these vessels is more labour intensive than in a single large vessel

2) the wines fermented in small oak vessels have a deeper colour and fuller body
due the:
* oxidative environment of oak
* action of yeast during fermentation
* small vessels also increases the contact between yeast lees and wines and this also contribute texture

3) the wines also provide more blending options:
* because each wine in the different vessels can show slightly different characteristics after the fermentation

Question 24

Malolactic conversion for white wines:

Answer 24

Reduction in acidity, increases microbial stability and modification to the flavours of wine

• low aromatic variety such as chardonnay: can have greater complexit due the effects of malo and the primary fruitcharacteristics
• • malo will decrease the acidity and increase PH
• • it is possible to adjust the acidity of the wine as necessary (this adjustmen can also be made at the must stage) it is also possible for winemakers to reduce the alcohol of the wine at this stage

Question 25

Barrel maturation for white wines:

Answer 25

1) premium and super premium wines
* * particularly low aromatic varieties, this can add texture and complexity of flavours

2) very costly for inexpensive wines and therefore they can use oak alternatives

Question 26

What about lees ageing for white wines ?

Answer 26

1) aim: give more body, soften the mouthfeel and help to stabilize the wine
* also protect against oxygen
* and may introduce some reductive sulfur compounds (low levels can be desirable)

2) the impact of lees is more significant in white wines than reds
3) less practiced on inexpensive wines

4) the lees may be stirred (battonage):
* increases the release of yeast compounds into the wine
* traditionally with a rod through the bung of a vessel
- - this also increases the exposure to oxygen: increase the effect of dead yeast and decrease primary fruit characteristics

– introduction of oxygen and disturbing of lees also reduces the development of reductive sulfur compounds and the off flavours they can introduce

** now there are options like automatically rotate the vessel without opening it (more control and more options)

5) lees stirring at a large number of barrels is labour intensive and can therefore dd to the cost of production