Post-Fermentation Flashcards
What’s an ideal storage temperature for reds? Whites?
10-20C (Optimal 15)
Below 10C
What is the humidity requirement for oak aging? Why?
75-85%
Prevents leaking, reduces evaporation
What is the optimal sulfur level to prevent oxidation?
Free sulfur = at least 20mg/L
How is micro-oxygenation done?
To red wines
Controlled into of oxygen to mirror barrel aging
Two chamber device to inject oxygen through a porous ceramic material
What chemical components cause the change in aroma with flor aged wines?
Ethanal formation and its degradation into diethyl acetyl
What are inert gases used for in post-fermentation? Which ones?
N and CO2
reduce oxidation
Prevent growth of spoilage bacteria and yeast
Which inert gas is more appropriate for each process?
CO2: denser and dissolves more readiy Used for displacing air from empty tanks and preses Flush hoses and pumps Blankets headspace of tank More in white wine
N: Less soluble in wine
Passes fine bubbles through wine
Removes dissolved oxgen or for additions like SO2
More in reds
What do small barrels do for wines?
Improve clarification and natural stabilization
More complexity
What species of oak are typically used for wine?
Quercus alba: American white oak. high aromatics
Quercus petraea: tighter grained, fewer extractable tannins, high aromatics
Quercus robur: low odiferous compounds
Where does European oak normally come from?
France (Tronçais, Allier, Nièvre) (Vosges) (Limousin, looser grained)
Eastern Europe (Russian, Hungarian, Slavonian)
Portugal (north)
How does barrel cutting affect oak?
Splitting along the oak grain to minimize leakage (Euro)
Sawn from each quarter bc less porous (American)
How does barrel drying affect oak?
Air: less aggressively tannic (French is air for 18-36)
Kiln
How does toast level affect taste?
Less toasted - more woody and tannic
More toasted - more spicy
How big is a hoghead?
300L
How big is a puncheon?
500L
What temp should full barrels be stored?
18-24C if MLF
10-15 if aging
How big are oak chips? When should they be added?
6.35mm to 2cm
During fermentation
Is toasted oak powder legal?
Not in the EU
When should blending be done?
Before final stabilisation and clarification
What is clarification?
THe process in which unwanted suspended particles are removed from grape must or wine
Dead yeast cells, grape skins, stems, seed and pulp, bacteria, taertrares, colloids
What are colloids? Why can’t they be removed by clarification alone?
Large organic molecules consisting of polysaccharides, tannins, other phenolics, tannins
Too small to be removed by clarification
Unstable.
How can clarification be achieved naturally?
Graivty - takes a long time by sedimentation. Hard to remove colloids this way
What are the main methods of clarification?
Sedimentation and racking Fining Filtration Centrifugation Flotation
What kinds of vessels are well-suited to sedimentation?
Small vessels with poor heat conduction (barrels)
How often will a white wine be racked off the lees? Reds?
White: Every 2 months
Reds: Every 3-4 months
How does centrifugation work?
Spin at 10,000rpm to cause matter in suspension to be separated out
Why would you use centrifugation?
Rapid clarification of must Remove yeast during fermentation to slow it New white wines at end of fermetnation Red wines right before barrel After fining Tartrate precipitation
Good for removing dense particles - expensive and big
Why do fining agents work?
Electrostatically charged to remove colloid materials. Attract oppositely charged materials to clump together
Which colloid are negatively charged? Positively?
Tannins, pectines, dextrans, glucans
Pigments and proteins
What is bentonite? What is it used for?
Montmorillonite clay Negative Used for protein stability in whites or rosés Lees settle better in bentonite Could be some flavor reduction Settle for 2-3 weeks then rack
What is gelatin? What is it used for?
Powder form dissolved in warm water
Removes off-tastes and astringency
Especially in whites where rotten grapes were used
Can remove tannins or color
What is casein? What is it used for?
Used for white wines with excess color or oxidised character
Reduce iron content
Tannin often added to precipitate
whole milk not permitted in EU
What is isinglass? What is it used for?
Swim bladder of fish Difficult prep Removes phenolics Used for whites just before bottling to improve clarity and vibrancy Produces fluffy lees which clogs filters
What is PVPP? What is it used for?
Reduces bitterness and browning (white wines with skin contact)
Soften tannic wines
Binds with phenolics
What is carbon? What is it used for?
Charcoal
Last resort for off odors and color
May also remove good flavors and aromas
What is silica sol? What is it used for?
Silicon oxide
Used with protein based fining agent to help flocculation
Accellerate clarification process
Negatively charges
What is tannin addition? What is it used for?
Facilitate stabilisation of new wines
Aid fining process
Are blood products allowed in the EU for fining?
Not since 1987
What is egg albumen? What is it used for?
White of eggs 3-4 egg whites per barrel Salt helps dissolving Fines red wines Little color or flavor removed QUALITY REDS
When are fining agents usually added
After fermentation and after one or two rackings
What does the filterability index of a wine depend on?
The percentage of solids
Size of particles
Nature of particles
Coarse = little clogging
Fine = lots
Polysaccharides block
Lees and bacteria clog
Difference between nominally rated and absolutely rated surfaces?
nominally = average pore size Absolutely = maximum pore size
What is depth filtration? Why is it good/bad?
Adsorption
Unwanted particles are trapped due to electrostatic and adhesion forces
Made of diatomaceous earth or pads of cellulose fibers (earth filtration sheet or cellulose)
High solids okay, grape must
Simple
Not absolute filtration
What is surface filtration?
Absolute filtration
Sieving mechanism
Liquid through membrane
.45 micron diameter = yeast and bacteria removal
What are membrane filters?
Made of thin plastic or ceramc material
Can be reused
What is perlite?
Derived from volcanic rock
Coarser than DE
Used for musts and cloudy wine
What are filter pads made of?
Cellulose
Pads can be reused
The plates are expensive
Pros/cons of cross-flow membrane filtration?
Pros: even dirty wines can be filtered.
Absolute filtering
Expensive
Flow rate decreases eventually
Clogs easily
What is ultra filtration?
Cross flow filtration
Membranes can filter out individual components of a wine
What is reverse osmosis?
Works like ultra filtration but only allows small particles to go through membrane (water, methanol, ethanol, acetic acid, ethyl acetate)
Concentrates musts
Decrese acetic acid
De-alcoholize finished wine
What is osmotic distillation?
high quality grape concentrates
Water vapour passes from grape juice through membrane into brine
What are the main instability problems for wine?
Tartrate instability
Oxidation
Microbial spoilage
(also proteins, phenolics, copper, iron)
What compound precipitates out when it comes to tartrate instability?
Potassium bitartrate
Calcium tartrate issues are less common but can happen. Not as easy to prevent
How to prevent tartrate instability?
Cold stabilisation: Chill wine to -4–8C for eight days. Now contact process instead (less expensive)
Contact process: Chill wine to 0C and seed it with powdered potassium bitartrate. Few hours
Gum arabis: Protective that prevents crystals from growing large. Only works for 1 year
Metataric Acid: Protects from precipitting for 1 year
Ion exchange: not in EU. Causes high levels of sodium in wine
What level should free sulfur be to prevent oxidation?
20 mg/L
What microorganisms can survive in wine?
Lactic bacteria
Acetic bacteria
Yeast
How is ethyl acetate created?
Acetic bacteria convert alcohol into acetic acid (vinegar) which binds to alcohol.
What are some examples of spoilage yeasts?
Candida (surface spoilage yeasts) - causes unwanted flor to bloom
Brettanomyces (found in wood)
What is acetaldehyde?
The yeasty taste that flor gives off
What does sorbic acid do?
Antimicrobial agent that prevents growth of yeast, mold, and fungi
Potassium sorbate that is dissolved
Can have a rancid flavor or be metabolised by lactic bacteria
What is the max permitted iron concentration in wine?
10mg/L
What is the max permitted copper concentration in wine?
EU:1mg/L
USA: .5mg/L
What are the steps taken when bottling a wine?
Pre-bottling analysis of wine
Checking quality of packaging
Monitoring bottling operation
Post-bottling analysis
What are appropriate free SO2 levels in wine while aging in bulk?
25-30 reds
35 whites
What is ISO 9001?
A common process attempted by members of the wine industry
What are halo-anisoles?
Corkiness or mustiness
What are some ways to analyze a wine before bottling?
High performance liquid chromotography
Fourier Transform Infrared Spectroscopy
Rapid DNA
Sugar limits for still wines in EU?
Dry: <4g/L
Medium-dry: <12g/L
Medium: 12-45 g/L
Sweet: >45g/L
Sugar limits for sparkling wines in EU?
Brut nature: <3g/L Extra Brut: <6g/L Brut: <12g/L Sec: 17-35g/L Demi-sec: 33-50 doux: >50
What is titratable acidity?
Total acidity
Expressed as equivalent of g/L tartaric acid (or sulfuric in France)
Min 4.5g/L
MOst have 5-7g/L
What pH range do most wines fall in?
2.8-4
Below 3 is rare
Softer, ripe reds are above 2.7
How much dissolved CO2 do most young white wines have?
600-1000mg/L
What is TDE?
Total dry extract
Takes into account alcoholic strenght, specific gravity, volatile acidity, and SO2 levels
Used to see if addition of water or excess sugar is used
What equipment is necessary for bottling?
Membrane filter Bottle rinser Filler Corker Labeller
What does modern bottling do?
Eliminates yeast or bacteria that could harm wine through Filtration or heat treatment
What is flash pasteurization?
Kill microbes by heating wine to 80-90C for a few seconds the rapid cooling
What is tunnel pasteurization?
high temperature for a medium length of time (sprayed by hot water after bottling) over 80C for 15 minutes
What is a common cork size?
44x24
What is a cork tree called?
Quercus suber
Bottling: How to test for SO2
titration of a known volume of the wine with a concentration of iodine after treating with alkaline solution
Bottling: How to test for VA
Simple glass still that is steam distilled and collected
Bottling: How to test for alcohol
Distillation and hydrometrics
Bottling: How to test forresidual sugar
fehlings titration reaction with copper salts
Bottling: How to test for malic and lactic acid
Paper chromatographic proedure
Bottling: How to test for tartrate instability
Filtered sample in -4C bath for 72 hours
Bottling: How to test for protein stability
Filtered sample heated to 80C for 6 hours
Bottling: How to test for sorbic acid
Colorimetric procedure
how to test for extra copper
Gas chromotography. Fill a clear bottle with wine and place it on a window in sun for 7 days
How to check for excess iron
Half filled clear bottle of wine in a cool dark place for 48 hours
