Common Winemaking Flashcards
What is MLF and what does it do?
Lactic acid bacteria converts tart malic grape acid into softer lactic acid
Also produces CO2 & softens and reduces acid
How do you control MLF?
Encourage MLF by raising the temperature of the wine and by not adding SO2 after fermentation
Avoid MLF by storing wine at cool temperatures, using SO2, or by filtering out the bacteria
What 4 factors determine the effect of oak maturation?
Species and origin: European or American oak
Size: Small (225- or 228-liter) or large (2000-liter)
Production method of barrel: Level of toast used
Age: First fill, second, etc., Imparts little at fourth+ fill
How are acid levels adjusted?
Adding acid: addition of tartaric acid (in powder form)
In Europe, this is permitted in warm regions only
Removing acid: addition of an alkali
Common in cooler regions
What 2 factors do winemakers control to affect alcoholic fermentation?
Yeast: commonly use Saccharomyces Cerevisiae
- Ambient yeast could also be used, but they can’t be as controlled
- Fermentation will stop if yeast runs out of sugar OR other needed nutrients (high sugar or alcohol can also stop it)
Temperature: fermentation won’t start if below 5°C and will stop if over 35°C
- Temperature used also affects the fruit characteristics and tannins levels
What are gross lees?
Post-fermentation lees that are heavy and fall to the bottom of vessels within a matter of hours
Can cause unpleasant aromas if not removed
What are fine lees?
Smaller particles that fall slower than gross lees
Fine lees are removed gradually in the maturation process
They add flavor and a richer texture
Describe sedimentation.
Clarification method done after fermentation
- After gross less are settled, the wine is slowly and gently pumped into a different vessel, leaving the sediment behind (“racking”)
- Subsequent rackings can remove fine lees
- Process can be accelerated with a centrifuge
For some fine wines, sedimentation and racking are the only clarification method used
Describe fining.
Clarification method done before bottling
- Some wine constituents slowly clump together over time and create haze or deposits
- This is prevented by adding a fining agents that speeds up the process
- Clumps are then removed before bottling
Fining is widely practiced and generally considered important, but winemakers avoid it because they think it affects the flavor and texture
How do winemakers achieve tartrate stability?
- Tartaric acid can form crystals called tartrates
- They are clear in white wine and purple in red wine
- Crystals are harmless and flavorless
- Cool temperatures accelerate the formation
- They can be removed after long maturation in cool cellar
- If this is impossible, chill the wine below 0°C for a short time
Crystals are removed by filtration
How do winemakers achieve microbiological stability?
- Yeast and bacteria thrive in grape and wine residues
- They can make a wine undrinkable and unfit for sale
- Fortified wines have no risk due to high level of alcohol
- Dry, high acid, MLF wine are resistant due to high alcohol, high acid, and lack of nutrients
(Some winemakers prefer to do MLF instead of sterilizing) - Low to med alcohol, low acid, non-MLF, residual sugar wines are high risk
(Careful handling and appropriate amount of SO2 is required)
Describe the filtration process.
Clarification method done after fermentation and during maturation
Filtering removes both gross and fine lees before bottling
Describe the 2 types of filtration.
Depth filtration: Made from thick material, solids get stuck in the filter (gross lees)
Surface filtration: Very fine sieves, very expensive and clog easily, usually done after depth filtration, sometimes fine enough to remove yeast and bacteria (i.e. sterile filtration)
What benefits do stainless steel and concrete vessels offer?
- Do not expose the wine to oxygen
- Help regulate the temperature of the wine
What are enrichment and chaptalization?
Enrichment: Increasing sugar levels during or before fermentation by adding Rectified Concentrated Grape Must (RCGM)
- Forbidden or strictly controlled in many areas
Chaptalization: When the sugar comes from something other than a grape (i.e. sugar beet)
