Level 4 D1 Chap 13 - General Winemaking Options Flashcards
What impact does the presence of oxygen have on wine?
Oxygen typically breaks down many flavours that make fresh, fruity wines. e.g. thiols in Sauvignon Blanc
Oxidation typically creates nutty/ savoury flavours, e.g. acetaldehyde
White wines become darker and browner
What compounds may help protect against the presence of oxygen in still wine?
Phenolic compounds in red wine are anti-oxidative
How are oxygen levels limited in winemaking?
- Avoid ullage in vessels; fill to the top and use tight seals
- Use inert gases to flush out oxygen/air from equipment before it makes contact with wine
- Add sulphur dioxide, which is anti-oxidative
- Use impermeable containers for processing and with bottles: stainless steel and concrete over wood; screw cap over cork
- Keep temperatures lower
When is oxygen required in winemaking?
At the start of fermentation, oxygen promotes healthy yeast growth
Early exposure may increase the stability of white wine to oxygen increasing ageing potential
In red wine oxygen is required for the reactions between anthocyanins and tannins that stabilises colour
Some oxygen exposure derived compounds may give desired characteristics: dried fruits, honey, caramel, coffee, leather, mushrooms
Some fortified wine requires oxygen: Oloroso, Madeira, Tawny port
How is oxygen exposure increased during winemaking?
Cap management techniques that spray/splash wine
Smaller wooden barrels
Increased rackings / lees stirring
Allow ullage in containers
Pump oxygen through (micro-oxygenation)
What properties does sulphur dioxide have in winemaking?
Anti-oxidant (indirect)
Anti-microbial
What SO2 levels are permitted by the EU?
150 mg/l in red wine
200 mg/l in white wine
Over 10 mg/l requires a label that the wine contains sulphites
How can winemakers reduce SO2 requirements?
- Limiting oxygen exposure during winemaking
- Lower temperatures during winemaking
- Good hygiene and grape sorting limit microbes
What states does SO2 exist in wine and how can these be influenced?
Bound SO2 has reacted with compounds in the wine and has limited benefits
Free SO2 is either inactive (most) or molecular (limited proportion).
Molecular SO2 is most beneficial. Greater proportions exist at lower pH
How are grapes and must protected in harvest and transportation?
Pack in smaller crates to protect against crushing
Keep temperatures lower - harvest at night
Add SO2 (potassium metabisulfite)
Keep equipment clean / sanitised
What processes may a grape be exposed to before fermentation?
Chilling Sorting, or triage Destemming Crushing Pressing
How can grapes be sorted?
- Remove unwanted grapes/bunches before harvest
- Sort by hand - on a table, a conveyer belt, or a vibrating belt (also removed MOG)
- Optical sorting
What are the implications of increasing sorting?
Increasing sorting, typically
- increases cost, and
- lowers yields as more grapes are removed.
It may be required in poor years, if there are larger number of unripe or moldy grapes
Why are some grapes not de-stemmed?
It depends on the wine being made:
- Some red wine fermentations use whole bunches, which increase tannin levels from stems (stems need to be ripe)
- carbonic maceration needs whole bunches
- some white wines and sparkling wines require whole bunch pressing
Explain crushing vs. pressing
Crushing breaks the skin of grapes and releases juice to instigate fermentation. Care is taken to leave seeds whole. Can be carried out by feet.
Pressing is the separation of juice or wine from skin and seeds
What are the common types of press?
Pneumatic press uses and air sack in a tank to apply pressure to grapes. Investment is greater, but the pressure control is greater and inert gas flushing can be carried out.
Basket press (also vertical or Champagne press) is unsealed, possibly more gentle that a pneumatic press, but more labour intensive as they hold a smaller load
Horizontal screw press is similar to a basket press
Continuous presses, which are better suited to high volume, inexpensive wine
What is the name for solid remains left over pressing?
Pomace
What are the common adjustments made to must?
Enrichment (chaptalisation, concentration, RCGM addition)
Reducing alcohol (dilution)
Acidification (4 types of acid commonly added: Tartaric, malic, citric, lactic)
Deacidification (2 compounds commonly added: potassium carbonate, calcium carbonate)
What practices are covered by the term ‘enrichment’?
Chaptalisation - adding dry sugar
Concentration of sugar levels
- reverse osmosis
- vacuum extraction
- chilling
Adding RCGM or other grape products
What level of chaptalisation is allowed in the EU?
1.5% to 3%
It depends on the area:
- Cooler regions may add up to 3% (to a maximum of 11.5% in white and 12% in red)
- Warmer regions may add up to 1.5%, and are limited to grape concentrate or RCGM
How is alcohol reduced prior to fermentation?
Typically dilution with water, although the practice is tightly controlled. Aromas and flavours are also diluted
How and when is acidification carried out?
Tartaric acid is usually added, although citric (not in the EU), malic and lactic acids can also be added
Acidification can happen at any point, although typically before fermentation
What level of de-/acidification is allowed in the EU?
-1 g/L to 2.5g/L
It depends on the area:
- In cooler climates, deacidification of up to -1 g/l is allowed
- In warmer climates, acidification of up to 2.5 g/l is allowed
Why do winemakers acidify must/wine?
In warmer climates, malic acid levels may drop dramatically during ripening
With too little acid, wine may lack freshness.
