D1.C16. Specific Options for White Winemaking Flashcards
What are the aims of skin contact for white wines?
- To enhance the extraction of aroma and flavour compounds and precursors
- To enhance the texture of the wine by extracting a small amount of tannin
What happens if the skin contact is used too excessively for the white wines?
It can make white wines taste bitter and feel coarse in the mouth
Is skin contact a common practice in white winemaking?
No, the majority of white wines are made with zero or very minimal skin contact
What are the advantages of using whole bunches in white winemaking?
- To further limit the contact between the juice and the skins
- To reduce risk of oxidation
- Providing a juice that is low in solids, tannins and color
- The stems provide channels for the juice to drain
In what conditions, minimal skin contact is desired for white winemaking?
- Where delicate fruity flavours, minimal colour and smooth mouthfeel are desired
- For wines that are designed to be drunk early because the tannins that would be extracted during skin contact would not have time to soften
- If fruit is at all under-ripe, as skin contact in this case could extract bitter flavours and astringent tannins
- Inexpensive wines for logistics and cost perspective
When is skin contact preferred?
Skin contact maximises flavour extraction and therefore it is most effectively used on aromatic grape varieties that have lots of aroma compounds that can be extracted, such as Riesling, Gewurztraminer, Viognier, Muscat and Sauvignon Blanc
What are the two main factors that influence extraction during skin contact?
- Time
- Temperature
What are the effects of chilling (usually below 15°C) the must during skin contact?
- Reduces the rate of extraction of flavours and tannins
- Reduces the rate of oxidation
- Reduces the threat of microbiological spoilage
- Reduces the likelihood of spontaneous fermentation
How are “orange” (amber) wines produced?
By fermenting white grapes on their skins
What are the tasting characteristics of orange wines?
Orange wines can have notable levels of tannin and characteristics such as dried fruit, dried herbs, hay or nuts
What are the attitudes of winemakers producing orange wines, in terms of winemaking practices?
They ususally work with traditional methods and minimal intervention, using ambient yeasts, without temperature control or SO2 additions
Why is pressing the white grapes typically 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
What are the disadvantages of whole bunch pressing?
- It is only an option if the grapes have been hand-harvested
- Whole bunches take up a lot of room in the press, so needs more time and more labour
So whole bunch pressing may be suitable when making smaller batches of premium wines
What is “free run juice”?
It is the juice that can be drained off as soon as the grapes are crushed
What are the properties of free run juice?
- Lowest in solids
- Lowest in colour and tannins
- Lower pH and higher acidity
What happens if the winemaker chooses to make wine from entirely free run juice?
It reduces the final volume of wine that can be produced and therefore has a cost implication
How is press juice different than free run juice?
- At the start, the press juice will be similar to the free run juice, but, as the pressing continues and more pressure is applied, more solids, tannin and colour are extracted
- It has lower acidity and less sugar
What is the advantage of separating the press juice in different fractions (press fractions)?
Different press fractions may be blended with the free run juice in the winemaking and/or maturation process
Why are last press fractions usually discarded?
They are likely to be too astringent or bitter (due to tannins from the skins, seeds or stems)
What is the target of hyperoxidation?
The compounds in the must that oxidise most readily
What is the aim of hyperoxidation?
- The main aim is to produce wines that are more stable against oxidation after fermentation
- It can also help to remove bitter compounds that can come from unripe grape skins, seeds and stems
Why is hyperoxidation typically better suited to less aromatic grape varieties such as Chardonnay?
Because hyperoxidation can destroy some of the most volatile aroma compounds (like the volatile thiols and methoxypyrazines found in Sauvignon Blanc), and therefore would not be carried out if an aromatic fruity or
herbaceous style of this wine was desired
What is the economic burden of hyperoxidation?
It is not particularly expensive, but it is an extra step in the winemaking process that requires labour to set up and monitor so may have some small impact on costs
What is the aim of clarificiation?
To reduce the amount of suspended solids within the must
What is the proportion of solids in the must that winemakers generally would like to achieve?
0.5 to 2 %
How can solid levels in the must below 1% be achieved?
- By using pectolytic enzymes
- Centrifugation
Why do some winemakers choose to retain between 1–2 per cent or marginally higher amounts of solids in the must?
- This can add to the texture of the wine, giving a subtle astringency
- Greater range of aromas from fermentation giving greater complexity
In which types of white wines a relatively high level of solids are not desirable?
Wines like inexpensive Pinot Grigio, for obtaining fruity aromas
Why do the fermentations with a high level of solids need careful monitoring and management?
As the various compounds within the solids and their reactions can give reductive sulfur compounds, leading to off-flavours.
Why is a small amount of solids is beneficial in the must?
It provides nutrients for yeast, and over-clarifying the must can lead to stuck fermentations
Why the fermentations with very low level of solid should be monitored closely?
Yeast nutrients like DAP may be needed to be added
Why is the must usually chilled around 4°C during sedimentation?
- To reduce the rate of oxidation
- To reduce the threat from spoilage
organisms - To avoid a spontaneous fermentation
What is the usual times allocated for sedimentation?
12-24 hours
What happens to the solids left behind after racking?
They will often be filtered by cross flow or depth filters to extract extra juice
What are the advantages of sedimentation?
- Cheapest method
- Requires no extra equipment or additives
What are the disadvantages of sedimentation?
- It takes the most time
- Cost of energy used in chilling
- It is a batch process which is costly in terms of labour and time
- So, it is most commonly used for small-volume production of premium wines
How does flotation work?
- Inert gas is bubbled up through the must
- Fining agent are added
- As the bubbles of gas rise, they bring with them the solid particles
- The solid particles are then skimmed off the top of the vessel
What are the differences of flotation, when compared with sedimentation?
- It is faster
- It can only be used in must, not wine
- It is little more expensive in terms of the equipment needed
- It can used as a continuous or a batch process
- Does not need chilling so saves energy cost
What are the advantages of centrifugation?
- Used continuously, which saves time and labour cost
- Can be used on wine as well as must
What are the disadvantages of centrifugation?
- It is expensive so typically only used in wineries needing to process large volumes of must quickly
- It also increases the must’s exposure to oxygen unless the machine is flushed with inert gas
What is the action of pectolytic enzymes?
Breaking down the pectins allows a more rapid separation between the liquid juice and solids
Can pectolytic enzymes be used for both must and wine?
Pectolytic enzymes only aid the clarification of must, not wine
What is the economic burden of clarifying agents for clarification of the must?
There is a cost of purchasing these agents, but this may be justified against the time and energy saved compared to sedimentation
Why is the fermentation temperatures for white wines are typically cooler?
Because, the volatile aroma and flavour compounds that are desired in many white wines, for example, many esters, are best produced and retained at cool temperatures (around 15°C)
What is the optimum temperature for the white wines where fruity aromas are not particularly desired (e.g. where oak is used)?
In these cases, the fermentation can be slightly warmer (17–25°C) to promote yeast health and avoid the production of certain esters, such as isoamyl acetate (banana-like smell).
What is the popular vessel of for fermentation to produce fruity, floral white wines like Sauvignon Blanc or Veneto Pinot Grigio?
Stainless steel tanks
Which kinds of vessels may be used for white wines fermented at slightly warmer temperatures, where maximising the fruity and floral aromas from fermentation is not the aim (for example, some styles of Chablis and white Rioja)?
Concrete and old oak vats as well as stainless steel tanks
Small oak barrels (sometimes with new oak) are popular choice for:
Particularly premium and super-premium Chardonnay.
What are the advantages of using small oak barrels for the fermentation of white wines?
- Wines that have been fermented in small oak vessels have a deeper colour and fuller body, due to the oxidative environment
- More integrated oak-derived aromas, due to the action of the yeasts during fermentation
- The small size of these vessels also increases the contact between the wine and yeast lees, and this is also thought to contribute texture
- Provide more blending options
What are the disadvantages of using small oak barrels for the fermentation of white wines?
- Adds costs due to the need to buy the barrels and the large number that may be required
- Monitoring fermentation in these small vessels is more labour intensive than monitoring a single large vessel
Small barrel fermentation is not a method of choice for which kinds of grapes?
Aromatic grapes like Riesling
Malolactic conversion is a choice for the wines produced by which type of grapes?
Low aromatic varieties like Chardonnay
Why adjustment of pH can be necessary after malolactic conversion?
Because malolactic conversion decreases the acidity and increases the pH of the wine
Which kinds of wines are likely to be aged small oak vessels?
-Premium and super-premium wines, particularly those made with low-aromatic varieties such as Chardonnay, are likely to be aged in small oak barrels for the texture and complexity of flavours this can bring
What are the options if any flavours from oak are wanted for inexpensive wines?
Staves or chips can be used
What are the aims of lees aging?
- Give more body
- Soften the mouthfeel
- Help to stabilize the wine
- Protect wine from oxygen and may introduce some reductive flavours
What is the aim of stirring the lees (batonnage), if practiced?
To increase the release of yeast compounds into the wine
What is the most traditional way of lees stirring?
- Using a rod and manually stir the lees into the wine
What is the advantage of using a rod and manually stir the lees into the wine?
Introduction of oxygen and disturbing of the lees also reduces the development of reductive sulfur compounds and the off-aromas
What is the disadvantage of using a rod and manually stir the lees into the wine?
- It increases oxygen exposure and can result in an increase in the effects from the dead yeast and a decrease in fruity flavours
How can oxygen exposure be prevented during lees stirring?
There are other options that now agitate and/or mix the lees without needing to open the vessel like barrel racks that permit easy rolling of the barrels
What is the economic burden of lees stirring?
Lees stirring on large numbers of large barrels is labour intensive and can therefore add to the cost of production
