What color grapes can be used to make white wine?
Predominantly white grapes, but many red/black grapes may also be used.
What are some important considerations winemakers have to weigh before processing and fermenting white grapes?
- Length of skin contact, if any
- Fermentation temperature
- Fermentation vessel
- Use of lees
- Malolactic fermentation
What chemical can be used at multiple points during the winemaking process to prevent oxidation and inhibit the growth of microorganisms?
Sulfur dioxide (SO2)
What are some of the effects Sulfur dioxide (SO2) has on wine?
SO2 acts as an:
- Antiseptic (kills microorganisms)
- Antioxidant (binds with oxygen)
What are some commonly practiced must adjustment techniques?
- Chaptalisation (adding sugar to increase alcohol)
- Watering back (to re-start fermentation or to dilute undesirable elements)
Which acid is typically used to acidify a wine?
How is a wine deacidified?
By adding an alkali (an acid neutralizer).
What is the most common must adjustment made to white grapes from warm/hot climates?
What is chaptalisation?
Adding sugar before or during fermentation in order to increase the alcohol level in a wine.
Beet and cane sugar are the most common forms of sugar used.
Why do most winemakers avoid skin contact on their white wines
To reduce the risk of oxidation and the extraction of unwanted flavors.
Why would some winemakers keep white wine juice in contact with the grape skins?
Because skin contact increases flavor intensity and texture.
If a winemaker is doing skin contact for a white wine, how long will the juice stay in contact with the skins?
Usually only for a few hours.
When are grapes for white wines pressed?
Before fermentation (ideally, shortly after they're harvested and brought to the winery).
What techniques can a winemaker use to clarify the must of a white wine?
What can happen to a white wine if the winemaker does not clarify the must adequately?
Unpleasant aromas can form from microbiological issues and fermentation may stop.
Why do some winemakers chose not to over-clarify their white wine musts?
Some winemakers believe that having a small amount of grape solids in a fermenting must will make the resulting wine less prone to oxidation; additionally, they feel these solids will contribute complex flavors and a more pleasing texture to the final wine.
What is the most commonly used yeast strain in winemaking?
Why is it preferred?
This yeast strain is preferred because of its hardiness against SO2 and elevated levels of alcohol.
What are the two sugars found in grapes which are easily converted into alcohol?
What aspects of winemaking will determine the speed of fermentation?
- Type and quantity of yeasts;
- Nutrient content in the must;
- Concentration of sugars in the must;
- Temperature (warmer temperatures mean faster fermentations);
- How much SO2 is used (too much slows fermentation).
What is the optimum fermentation temperature for white wine?
Between 12°C - 22°C (54°F - 72°F)
What may happen if white wines are fermented at too low a temperature?
- Yeasts may go dormant, but they can be woken up with an increase of heat;
- Low fermentation temperatures may result in "pear drop" or pear candy aromas and may prevent a grape's true varietal aromas from developing.
What may happen if white wines are fermented at too warm a fermentation temperature?
- Yeasts may die;
- Hot fermentation temperatures will sometimes create unappealing aromas, and there is a risk that the classic varietal character will be lost in the process.
What kinds of vessels are commonly used to ferment white wines?
- Steel tanks
- Oak barrels
What are the advantages of fermenting white wines in stainless steel?
- Stainless steel is inert (non-reactive), which helps maintain varietal character;
- Temperature control systems are easier to build into stainless steel fermenters than oak or cement.
What are the advantages of fermenting in oak barrels?
- Oak barrels are known to transfer heat effectively;
- Oak barrels will add richer flavors and rounder textures.
What will cause a fermentation to cease (aka a stuck fermentation)?
- All available sugar in a must is consumed;
- Yeasts run out of nutrients to metabolize;
- Temperatures exceed 35ºC (95ºF)
What are some potential complications a winemaker can run into during fermentation?
Yeast nutrient deficiencies in the must, which can lead to stuck fermentations or off-odors;
Carbon dioxide poisoning.
What are some important considerations winemakers must take into account post-fermentation in re: white wines?
- What vessel to use (oak, stainless steel, etc.)
- Whether to blend or not;
- Whether to lees age or not;
- Whether to allow, actively encourage, or completely block MLF;
- Whether to fine or filter the wine, and how much.
What are some of the benefits of blending white wines post-fermentation?
Blending helps the winemaker:
- improve consistency, texture, or flavor;
- enhance balance;
- create wines of a particular or desired style.
What flavors will aging in new oak add to white wines?
Oak aging is known to add flavors of vanilla, toast, bread, clove, dill, nutmeg, coconut, butterscotch, anise, and smoke.