What are the main purposes of skin contact?
- Enhance texture (by extracting small amt of tannin)
2. Enhance extraction of aroma compounds and aroma precursors
What happens when skin contact is used too much?
Wine can taste bitter and feel coarse
Why do some producers not want any skin contact? (Multiple reasons)
- Want to preserve fresh fruit aroma
- Minimal color extraction
- Smooth mouthfeel (no tannins)
- Want wines that can be drunk early (tannins need time to integrate with the wine and soften)
- If fruit is underripe, want to avoid extracting bitter flavors and astringent tannins
- Want to sell the wine early & cheaply - skin contact slows down the process and adds additional labor & equipment
Is skin contact more effective on aromatic or nonaromatic grapes? Why?
Aromatic because they have more aroma compounds to extract. These aromatic varietals also seldom see oak so this adds texzture
What are the 2 key factors that influence level of skin contact extraction?
Time and Temp
What makes a wine an orange wine? What are the classic characteristics?
Fermentation on skins
Notable levels of tannins. Flavors of dried fruit, dried herbs, hay, nuts
What are the pros of pressing whole bunches?
- Reduces chance of oxidation before and during pressing. Esp if inert gasses are used
- More gentle - stems help break up the mass of grape skins
- Provides juice that is low in solids, tannins, and colors
Why is whole bunch pressing usually only reserved for premium/small batch wines?
- Whole grapes take up more storage space
- Fewer grapes are pressed at once - takes more time
- Grapes must have been hand harvested
Free run juice vs Press juice - in terms of sugar, pH, tannins, color, solids
- More sugar
- Lower pH/higher acidity
- Less tannins
- Less color
- Less solids
What are press fractions and what are they used for?
Separated press juice
Different press fractions can be blended with the free run juice in the winemaking or maturation process to increase body and texture
What is hyperoxidation?
What happens during it?
What is the goal?
Technique of deliberately exposing the must to large quantities of oxygen before fermentation
Targets the compounds in the must that oxidize most readily. As they oxidize, these compounds turn the must brown. During fermentation, the compounds precipiate out, returning the wine to its normal color
Goal: stabilize the wine against oxidation after fermentation and remove bitter compounds (ie from unripe grape skins, seeds, skins)
Is Hyperoxidation more suitable for aromatic or non aromatic varietals?
Nonaromatic because it destroys most volatile aroma compounds (ie thiols, methoxypyrazines)
When does must clarification happen?
Between pressing and fermentation
After fermentation
What is the general percentage of solids in the must?
0.5-2%
How do you get solids in the must to be lower than 1% in white wine must?
Using pectolytic enzymes or centrifugation
Why do some winemakers want to leave 1-2% or more of solids in white wine for fermentation?
- Add texture to wine
- Give a subtle astringency
- Greater range of aromas from fermentation - greater complexity HOWEVER you sacrifice fruityness
- Provides nutrients for yeast and prevents stuck fermentations
Risk of high solids fermentation
The various compounds within the solids adn their reactions can lead to off flavors
Ie. Reductive sulfur compounds at high levels (rotten eggs smell)
What is the benefit of having a small amount of solids in the must? REMOVE
Provides nutrients for yeast and prevents stuck fermentations
Methods of clarification of grape must:
- Sedimentation
- Flotation
- Centrifugation
- Clarifying Agents
Describe sedimentation
AKA Settling
Must is chilled to around 4C to reduce the rate of oxid, risk of spoilage organisms, and spontaneous fermentation
Suspended solids fall over time due to gravity (12-24 hrs)
Clear juice is removed via racking (transferring to the fermentation vessel
Cheapest in terms of equipment
Most time consuming, laborous (batch process) and takes energy to chill wine THEREFORE mostly used for premium wines
What is the rate of sedimentation dependent on?
- Temp - the colder the temp, the longer it takes
2. Size of the vessel - large, tall vessels take more time than short small ones
Describe flotation
The bubbling up of gas through the must. As the bubbles rise, they bring up solid particles. The solid particles are then skimmed off the top of the vessel
Faster than sedimentation
Generally inert gases like nitrogen is used. If O2 is used, this is a form of hyperoxidation
Fining agents must be added to the must for this to work
Can be continous or batch process
Describe Centrifugation and pros/cons
A machine with a rapidly rotating container that uses centrifugal forces to separate solids from liquids
Pros: very fast, continuous
Cons: expensive equipment, increases exposure to O2 unless flushed with inert gas
Describe Clarifying Agents
Different compounds can be added to the must as processing aids to speed up the rate of sedimentation
Ie. Pectolytic enzymes can help break down pectins (naturally found in plant cell walls). Breaking down pectins allows a more rapid separation between the liquid juice and solids
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Chapter 13 - General Winemaking Options46
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Chapter 14 - Maturation14
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Chapter 15 - Finishing & Packing P135
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Chapter 15 - Finishing and Packaging P240
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Chapter 16 - White Winemaking34
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Chapter 17 - RS Wines Winemaking20
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Chapter 18 - Red Winemaking46
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Chapter 19 - Rosé Winemaking13
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Chapter 1 - The Vine30
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Chapter 2 - The Vine Growth Cycle36
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Chapter 3 - The Growing Environment - Part 1 Sunlight and Temperature27
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Chapter 3 - The Growing Environment - Part 2 Water & Nutrients32
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Chapter 4 - Approaches to Grape Growing14
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Chapter 5 - Vineyard Establishment23
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Chapter 6 - Managing Nutrients and Water25
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Chapter 7 - Canopy Management28
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Chapter 8 - Part 1: Hazards13
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Chapter 8 - Part 2: Pests10
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Chapter 8 - Part 3: Diseases20
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Chapter 9 - Harvest12
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Chapter 11 - Wine Components20
