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Post-Fermentation Flashcards

1
Q

What’s an ideal storage temperature for reds? Whites?

A

10-20C (Optimal 15)

Below 10C

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2
Q

What is the humidity requirement for oak aging? Why?

A

75-85%

Prevents leaking, reduces evaporation

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3
Q

What is the optimal sulfur level to prevent oxidation?

A

Free sulfur = at least 20mg/L

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4
Q

How is micro-oxygenation done?

A

To red wines
Controlled into of oxygen to mirror barrel aging
Two chamber device to inject oxygen through a porous ceramic material

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5
Q

What chemical components cause the change in aroma with flor aged wines?

A

Ethanal formation and its degradation into diethyl acetyl

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6
Q

What are inert gases used for in post-fermentation? Which ones?

A

N and CO2
reduce oxidation
Prevent growth of spoilage bacteria and yeast

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7
Q

Which inert gas is more appropriate for each process?

A 
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

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8
Q

What do small barrels do for wines?

A

Improve clarification and natural stabilization

More complexity

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9
Q

What species of oak are typically used for wine?

A

Quercus alba: American white oak. high aromatics
Quercus petraea: tighter grained, fewer extractable tannins, high aromatics
Quercus robur: low odiferous compounds

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10
Q

Where does European oak normally come from?

A

France (Tronçais, Allier, Nièvre) (Vosges) (Limousin, looser grained)
Eastern Europe (Russian, Hungarian, Slavonian)
Portugal (north)

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11
Q

How does barrel cutting affect oak?

A

Splitting along the oak grain to minimize leakage (Euro)

Sawn from each quarter bc less porous (American)

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12
Q

How does barrel drying affect oak?

A

Air: less aggressively tannic (French is air for 18-36)

Kiln

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13
Q

How does toast level affect taste?

A

Less toasted - more woody and tannic

More toasted - more spicy

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14
Q

How big is a hoghead?

A

300L

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15
Q

How big is a puncheon?

A

500L

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16
Q

What temp should full barrels be stored?

A

18-24C if MLF

10-15 if aging

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17
Q

How big are oak chips? When should they be added?

A

6.35mm to 2cm

During fermentation

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18
Q

Is toasted oak powder legal?

A

Not in the EU

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19
Q

When should blending be done?

A

Before final stabilisation and clarification

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20
Q

What is clarification?

A

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

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21
Q

What are colloids? Why can’t they be removed by clarification alone?

A

Large organic molecules consisting of polysaccharides, tannins, other phenolics, tannins

Too small to be removed by clarification

Unstable.

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22
Q

How can clarification be achieved naturally?

A

Graivty - takes a long time by sedimentation. Hard to remove colloids this way

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23
Q

What are the main methods of clarification?

A 
Sedimentation and racking
Fining
Filtration
Centrifugation
Flotation
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24
Q

What kinds of vessels are well-suited to sedimentation?

A

Small vessels with poor heat conduction (barrels)

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25
How often will a white wine be racked off the lees? Reds?
White: Every 2 months Reds: Every 3-4 months
26
How does centrifugation work?
Spin at 10,000rpm to cause matter in suspension to be separated out
27
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
28
Why do fining agents work?
Electrostatically charged to remove colloid materials. Attract oppositely charged materials to clump together
29
Which colloid are negatively charged? Positively?
Tannins, pectines, dextrans, glucans Pigments and proteins
30
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 ```
31
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
32
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
33
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 ```
34
What is PVPP? What is it used for?
Reduces bitterness and browning (white wines with skin contact) Soften tannic wines Binds with phenolics
35
What is carbon? What is it used for?
Charcoal Last resort for off odors and color May also remove good flavors and aromas
36
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
37
What is tannin addition? What is it used for?
Facilitate stabilisation of new wines | Aid fining process
38
Are blood products allowed in the EU for fining?
Not since 1987
39
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 ```
40
When are fining agents usually added
After fermentation and after one or two rackings
41
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
42
Difference between nominally rated and absolutely rated surfaces?
``` nominally = average pore size Absolutely = maximum pore size ```
43
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
44
What is surface filtration?
Absolute filtration Sieving mechanism Liquid through membrane .45 micron diameter = yeast and bacteria removal
45
What are membrane filters?
Made of thin plastic or ceramc material | Can be reused
46
What is perlite?
Derived from volcanic rock Coarser than DE Used for musts and cloudy wine
47
What are filter pads made of?
Cellulose Pads can be reused The plates are expensive
48
Pros/cons of cross-flow membrane filtration?
Pros: even dirty wines can be filtered. Absolute filtering Expensive Flow rate decreases eventually Clogs easily
49
What is ultra filtration?
Cross flow filtration | Membranes can filter out individual components of a wine
50
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
51
What is osmotic distillation?
high quality grape concentrates | Water vapour passes from grape juice through membrane into brine
52
What are the main instability problems for wine?
Tartrate instability Oxidation Microbial spoilage (also proteins, phenolics, copper, iron)
53
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
54
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
55
What level should free sulfur be to prevent oxidation?
20 mg/L
56
What microorganisms can survive in wine?
Lactic bacteria Acetic bacteria Yeast
57
How is ethyl acetate created?
Acetic bacteria convert alcohol into acetic acid (vinegar) which binds to alcohol.
58
What are some examples of spoilage yeasts?
Candida (surface spoilage yeasts) - causes unwanted flor to bloom Brettanomyces (found in wood)
59
What is acetaldehyde?
The yeasty taste that flor gives off
60
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
61
What is the max permitted iron concentration in wine?
10mg/L
62
What is the max permitted copper concentration in wine?
EU:1mg/L USA: .5mg/L
63
What are the steps taken when bottling a wine?
Pre-bottling analysis of wine Checking quality of packaging Monitoring bottling operation Post-bottling analysis
64
What are appropriate free SO2 levels in wine while aging in bulk?
25-30 reds | 35 whites
65
What is ISO 9001?
A common process attempted by members of the wine industry
66
What are halo-anisoles?
Corkiness or mustiness
67
What are some ways to analyze a wine before bottling?
High performance liquid chromotography Fourier Transform Infrared Spectroscopy Rapid DNA
68
Sugar limits for still wines in EU?
Dry: <4g/L Medium-dry: <12g/L Medium: 12-45 g/L Sweet: >45g/L
69
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 ```
70
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
71
What pH range do most wines fall in?
2.8-4 Below 3 is rare Softer, ripe reds are above 2.7
72
How much dissolved CO2 do most young white wines have?
600-1000mg/L
73
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
74
What equipment is necessary for bottling?
``` Membrane filter Bottle rinser Filler Corker Labeller ```
75
What does modern bottling do?
Eliminates yeast or bacteria that could harm wine through Filtration or heat treatment
76
What is flash pasteurization?
Kill microbes by heating wine to 80-90C for a few seconds the rapid cooling
77
What is tunnel pasteurization?
high temperature for a medium length of time (sprayed by hot water after bottling) over 80C for 15 minutes
78
What is a common cork size?
44x24
79
What is a cork tree called?
Quercus suber
80
Bottling: How to test for SO2
titration of a known volume of the wine with a concentration of iodine after treating with alkaline solution
81
Bottling: How to test for VA
Simple glass still that is steam distilled and collected
82
Bottling: How to test for alcohol
Distillation and hydrometrics
83
Bottling: How to test forresidual sugar
fehlings titration reaction with copper salts
84
Bottling: How to test for malic and lactic acid
Paper chromatographic proedure
85
Bottling: How to test for tartrate instability
Filtered sample in -4C bath for 72 hours
86
Bottling: How to test for protein stability
Filtered sample heated to 80C for 6 hours
87
Bottling: How to test for sorbic acid
Colorimetric procedure
88
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
89
How to check for excess iron
Half filled clear bottle of wine in a cool dark place for 48 hours

Viticulture/Vinification (7 decks)

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