Winemaking Flashcards
What sensations does alcohol contribute to wine?
Sweetness, bitterness, warmth, fullness
What does volatile acidity refer to?
Acetic acid
What is rotundone?
Peppery aroma in Syrah and GV
Characteristics of wine with low pH:
Stable, bright red, increased ageability, increased effectiveness of SO2
How are flavors formed in wine?
Fermentation
Grape must contains aroma precursors
Building blocks for post-fermentation aromas and flavors
Thiols:
Aromatic compounds released during fermentation
Terpenes:
Aromatic compounds released in fermentation with fruity and floral aromas
Aromas created by fermentation:
Esters
Acetaldehyde
Diacetyl (buttery)
Sulfur compounds
Importance of Glycerol?
3rd most abundant part of wine
Contributes smooth texture and full body, lightly sweet
Is SO2 allowed in organic winemaking?
Yes in EU
Yes in US with “wine from organic grapes”
No added in US for organic winemaking, and all naturally occuring <10mg/L
How to limit oxygen in winemaking?
Avoid ullage (space of air) Use of inert gases - nitrogen, co2, argon Add SO2 - antioxidative Impermeable containers - stainless steel Cool, constant temperature
How to increase oxygen exposure in winemaking?
Cap management Small wood barrels Allowing ullage Racking/lees stirring Hyperoxidation/micro-oxygenation
Role of SO2 in winemaking, and when is it added?
Anti-oxidant
Anti-microbial
Soon after grapes are picked/reach the winery, crush, after MLF, and at bottling.
When is SO2 not effective?
When it is bound - SO2 binds when added to must or wine
At high pH levels
How to best transport grapes to winery?
In small crates to minimize crushing
Sanitized equipment
Cold temps
Addition of SO2
When does pressing occur?
White wines - right after crush
Red wines - after desired time on skins or after fermentation
Describe pneumatic press:
“air bag”
Cylindrical cage with a bladder
Bag gradually inflates - can be programmed for appropriate pressure
Easily flushed to prevent oxidation
Describe basket press:
More traditional but now less common "vertical press" Pressure applied from above, juice/wine flows through holes on the side No prevention from Oxygen - open Gentler
Name four types of presses:
Pneumatic, basket, horizontal screw, continuous
Define enrichment:
Adjusting the potential alcohol in grape must
Practiced after fermentation begins
Includes Chaptalisation (adding beet or cane sugar)
Can also add grape concentration or RCGM
Four ways to raise alcohol in must:
Enrichment
Reverse Osmosis
Cryoextraction
Vacuum evaporation
How do you reduce alcohol in wine?
Add water to grape must pre-fermentation
Most common method for acidification?
Tartaric acid addition
Methods for deacidification?
Addition of Calcium Carbonate (chalk)
Addition of Potassium Carbonate
Ion exchange
Process of yeast in fermentation:
Yeast eat O2 and multiply (aerobic respiration)
Switch to fermentation when O2 is out (anaerobically)
Needs viable temp range, access to nitrogen and nutrients, alcohol, CO2, and heat
Fermentation temperature ranges:
Cool - 12-16 Fresh, fruity white and rose Moderate - 17-25 Fruity reds and less fruity/barrel whites Warm - 26-32
Advantages of concrete over stainless steel for fermentation?
Maintain a much more even temperature
Create convection currents that mix must and lees
Advantages of stainless steel for fermentation:
Easy to clean, large, controlled, neutral, protect against oxygen, mechanized
Advantages of wood fermentation:
Retains heat, allows small stream of Oxygen
Long term - inexpensive
What factors encourage MLF?
18-22
Moderate pH 3.3-3.5
Low SO2
Adding cultured lactic acid bacteria
Effects of MLF?
Reduction of Acidity Rise in pH Color loss in red wines Greater Microbial stability Flavor modification - loss of fruit character, addition of butter
Options for removing alcohol post-fermentation?
Reverse osmosis
Spinning cone
What factors have an influence on the wine during maturation?
Oxygen, new wood, yeast lees
Effects of oxygen during maturation?
Gradual reduction of primary aromas
Development of tertiary aromas
Color change
Softening of tannins
Effect of temperature on oxidation?
Warm temperatures increase speed of oxidation
How does oxygen permeate the barrel?
First month, through the pores
Over time, gaps between staves and the bung hole
Describe micro-oxygenation
Small doses of oxygen are bubbled into the wine post-fermentation
Effects of micro-oxygenation in maturation?
Increased intensity Increased color stability Softer tannins Improved texture Reduces unripe, herbaceous flavors
Storage temperature for wines?
Whites: 8-12
Reds: 12-16
Describe wine loss during maturation
Can occur when barrel-aged
Water/alcohol evaporates through staves
Increased loss with warm temperatures and low humidity
What is a barrique?
A small vessel - 225L
Name of a large vessel for aging?
Foudres
Components unique to American oak?
Lactones
Less oak tannin
Why is American oak cheaper?
Can be sawn (makes more vessels)
Grows significantly quicker
Half-price of European
Five species of oak:
American, French, Hungarian, Russian, Slavonian
Other wood alternatives to oak?
Chestnut, cherry, acacia
Define and explain the role of autolysis
Break down of dead yeast cells
Contributes flavors, body, and texture to the wine after fermentation if not filtered
Stabilizes the wine
What does blending refer to?
Varieties Locations Different growers/businesses Vintages Different vinifications Different vessels
Why do you blend?
Balance Consistency Reach a desired style Complexity Minimize faults Volume Price
Methods of post-fermentation clarification?
Sedimentation, Centrifugation, Fining, and Filtering
Three categories of fining agents?
Removal of unstable proteins
Remove phenolics that contribute color/bitterness
Remove color and off-odors
Examples of fining agents?
Charcoal Egg White Gelatine Bentonite Casein Isinglass Vegetable protein products PVPP - Polyvinylpolypyrrolidone
Types of filtration:
Surface (membrane or cross-flow)
Depth (Sheet or diatomaceous earth)
How to ensure protein stability?
Fining with bentonite
How to ensure tartrate stability?
Cold stabilisation Contact process Electrodialysis Ion Exchange Carbosyethylcellulose (CMC) Metatartaric Acid
Define cold stabilization:
Wine chilled to -4C for ~8 days and then filtered
Removes potassium bitartrate
Define contact process
Potassium bitartrate added to wine, speeds up crystalization
Wine chilled to 0C and filtered after 1-2 hours
Quicker, cheaper, and more reliable form of cold stabilization
Define electrodialysis
Form of tartrate stability that uses a charged membrane to remove potassium, calcium, and tartrate ions
Amount of free SO2 in wine?
White: 25-45mg/L
Red: 30-55mg/L
Sweet: 30-60mg/L
Define sparging
Removing dissolved oxygen before bottling by flushing with inert gas
What causes volatile acidity?
Activity of acedic acid bacteria
Inadequate levels of SO2
Excess exposure to Oxygen
How to avoid brett?
Excellent winery hygiene
Maintain effective SO2 levels
Keep pH low
Short time between Fermentation and MLF so SO2 can be immediately added
Measuring oxygen in packaging?
Total package oxygen:
- Dissolved oxygen
- oxygen in head space
- oxygen in cork
- oxygen transmission rate of cork/closure
