D1 Specific options for white winemaking

Question 1

Skin contact

Answer 1

After crushing and before pressing white wines may be left in contact with the skins (cold soaking) for 24 hours and over to enhance the extraction of aroma and flavour compounds and precursors and texture (tannins).

Chilling slows down extraction, permitting more control. Also reduce risk of oxidation and threat from spoilage organisms.

Usually done for aromatic grape varieties only because non-aromatic grapes would lose their aromas.

This process requires time and labour, therefore not applicable for inexpensive wines.

White wine may also be fermented on their skins, known as orange wines.
This wines have high tannins and aromas of dried fruit, dried herbs, hay and nuts.

Question 2

Pressing the grapes

Answer 2

Whole bunch pressing is the gentlest form of pressing.
It avoid the extraction of unwanted compounds from the skin and seeds, such us tannins and colour.
It minimise the rate of oxidation (especially if inert gas is used).
Because grapes must be hand-harvested and the whole bunches takes lot of space in the press this is suitable for small/premium production.
If grapes are destemmed and crushed, the juice drain off (“free run juice”) is typically the lowest in solid, tannin and colour, lower in pH and higher in acidity and sugar.
Using only the free run juice reduces the volume of the wine, therefore has a cost implication .
Usually free run and pressed juice are blended together to increase body and texture.

Question 3

Hyperoxidation

Answer 3

Is the technique that expose the must to oxygen before fermentation.
The aim is to produce a wine that is more stable against oxidation after fermentation.
Best for less aromatic grapes as it can disrupt most volatile aroma compounds.
The equipment is not expensive, however add costs of monitoring and labour.

Question 4

Clarification of must

Answer 4

Reduce the amount of suspended solid (grape skin, stem, seeds).
Ideal suspended solid is 0.5-2%.

Right amount can add texture, moderate astringency, grater range of aromas from fermentation, greater complexity.
Too high solid level can give reductive aromas.
Too little solid may not provide nutrients for yeast, leading to stuck fermentation.

The careful monitoring make it suited to small volume/premium wines.

Question 5

Clarification options

Answer 5

Sedimentation (must and wine)
The must is chilled to around 4C (to reduce the rate of oxidation and the threat from spoilage organisms) for 12-24 hours. The must is then racked off.
It requires no extra equipment or additives.
However, this process takes time and labour (due to batch process) and costs of energy is high.
For this reasons it suited to small volume/premium wines.

Flotation (must only)
Bubbles gas (inert gas, nitrogen) up through the must.
The solid particles are them skimmed off.
Fining agents must be added (to help the binding of the particles).
Equipment is little bit more expensive.
Quick and continuous.
Also, does not need chilling, saving energy costs.

Centrifugation (wine and must)
Separate solids and liquids.
It is quite invasive to the wine.
Quick and continuous.
Save time and labour costs.

Clarifying agents (must only)
Can be added to speed up the rate of sedimentation.
Petolytic enzymes break down pectins.
There is a cost but is justified against the time, labour and energy saved.

Question 6

Fermentation temperatures and vessels

Answer 6

Floral, fruity white wines are best produced at cool temperature (15C), less aromatic varieties, lightly warmer temperatures (17-25C).
Stainless steel is tanks are used due to the ability to control temperatures easily.

Barriques and concrete may be use for premium wines.
The barriques-aged wines gain deeper colour and fuller body, more integrated oak derived aromas.
Increased contact between the wine and the lees contributes texture.
However, this add costs of barrels, monitoring lots of barrels.

Question 7

Malolactic conversion

Answer 7

The effects are reduction in acidity, increase pH,
increase microbiological stability and modification of flavour.
Usually done in non-aromatic grape varieties, where is perceived as greater complexity.

Question 8

Barrel maturation

Answer 8

Premium, low aromatic wines may be aged in oak to add texture and complexity of flavour (vanilla, clove, ginger, nutty).
Inexpensive alternative are oak chips and staves.

Question 9

Lees ageing

Answer 9

Contributes more body and help stabilise the wine.
May introduce reductive sulfur compounds (struck match, smoke, rotten egg, cabbage)
The lees may be stirred (batonnage) or not.
Batonnage increase the effect of the lees and the oxygen exposure, decreasing the fruit flavours and the reductive sulfur compounds.
Add time, storage and labour costs.

Question 10

Blending

Answer 10

Blending, finishing and packaging