Ch 7 - Clarification And Stabilisation & Closures Flashcards
What is the reason for clarification?
Most wine consumers prefer clear wines so any solid parts eg lees must be removed.
What are the main clarification methods used?
Sedimentation;
Fining;
Filtration
Describe sedimentation.
Normally done after fermentation using “racking”. After gross lees settle the wine is “racked” ie gently pumped into a different vessel leaving sediment behind. It may also be done during maturation to remove unwanted fine lees.
Describe fining.
Helps to ensure wine stability. An agent eg albumen, is added to the wine and helps particles clump together so they can be removed before bottling.
What is filtration? Name the two main methods.
This is a process which removes particles from wine by passing thought a filter after fermentation and during maturation.
Depth filtration and Surface filtration methods.
What is depth filtration?
This involves use of filters made from a thick layer of material which traps particles. Can handle very cloudy wines and remove gross lees.
What is surface filtration?
This resembles fine sieves which trap particles as wine flows through and are normally used after depth filtration. If pores are small enough to remove yeast and bacteria thisis called sterile filtration.
Is all wine clarified?
No. It is a winemakers choice based on their customers likes. Some believe it negatively affects wine character and texture.
What is the definition of “stable” wine?
If the wine, over a specified timeframe, changes in a slow, predictable manner. The acceptable amount of change and time frame will vary from wine to wine.
What thre areas of stability are important?
Tartrate stability;
Microbiological stability;
Oxygen stability.
Why is tartrate stabilisation required? How is it countered?
Tartaric acid can form crystals called tartrates over time. They are harmless and flavourless but can spoil appearance of wine.
By chilling wine below 0 deg C for a short period they will form and can be removed by filtration
Why is microbiological stabilisation required?
Many different forms of yeast and bacteria can spoil a wine making it undrinkable. Winery equipment must be completely clean.
Which type of wines are least at risk from microbiological contamination?
Fortified wines - high abv toxic for all microorganisms.
High acid, dry wine which undergone MLF - Insufficient nutrients for bacteria
Which type of wines are more at risk from microbiological contamination? How is it managed
Low to medium abv, low acidity, some residual sugar, not undergone MLF.
Careful handling, appropriate amount of SO2 and sterile filtering prior to bottling.
Why is oxygen stabilisation required? How is it managed?
Oxygen in wine or entering through packaging will cause oxidation, and wine will lose its fruit aromas and turn brown.
Appropriate use of SO2 and avoiding exposure to oxygen. Sterilised bottles.
