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Viticulture/Vinification > Post-Fermentation > Flashcards

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
Q

How often will a white wine be racked off the lees? Reds?

A

White: Every 2 months
Reds: Every 3-4 months

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26
Q

How does centrifugation work?

A

Spin at 10,000rpm to cause matter in suspension to be separated out

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27
Q

Why would you use centrifugation?

A 
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

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28
Q

Why do fining agents work?

A

Electrostatically charged to remove colloid materials. Attract oppositely charged materials to clump together

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29
Q

Which colloid are negatively charged? Positively?

A

Tannins, pectines, dextrans, glucans

Pigments and proteins

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30
Q

What is bentonite? What is it used for?

A 
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
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31
Q

What is gelatin? What is it used for?

A

Powder form dissolved in warm water
Removes off-tastes and astringency
Especially in whites where rotten grapes were used
Can remove tannins or color

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32
Q

What is casein? What is it used for?

A

Used for white wines with excess color or oxidised character
Reduce iron content
Tannin often added to precipitate
whole milk not permitted in EU

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33
Q

What is isinglass? What is it used for?

A 
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
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34
Q

What is PVPP? What is it used for?

A

Reduces bitterness and browning (white wines with skin contact)
Soften tannic wines
Binds with phenolics

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35
Q

What is carbon? What is it used for?

A

Charcoal
Last resort for off odors and color
May also remove good flavors and aromas

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36
Q

What is silica sol? What is it used for?

A

Silicon oxide
Used with protein based fining agent to help flocculation
Accellerate clarification process
Negatively charges

37
Q

What is tannin addition? What is it used for?

A

Facilitate stabilisation of new wines

Aid fining process

38
Q

Are blood products allowed in the EU for fining?

A

Not since 1987

39
Q

What is egg albumen? What is it used for?

A 
White of eggs
3-4 egg whites per barrel
Salt helps dissolving
Fines red wines
Little color or flavor removed
QUALITY REDS
40
Q

When are fining agents usually added

A

After fermentation and after one or two rackings

41
Q

What does the filterability index of a wine depend on?

A

The percentage of solids
Size of particles
Nature of particles

Coarse = little clogging
Fine = lots
Polysaccharides block
Lees and bacteria clog

42
Q

Difference between nominally rated and absolutely rated surfaces?

A 
nominally = average pore size
Absolutely = maximum pore size
43
Q

What is depth filtration? Why is it good/bad?

A

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
Q

What is surface filtration?

A

Absolute filtration
Sieving mechanism
Liquid through membrane
.45 micron diameter = yeast and bacteria removal

45
Q

What are membrane filters?

A

Made of thin plastic or ceramc material

Can be reused

46
Q

What is perlite?

A

Derived from volcanic rock
Coarser than DE
Used for musts and cloudy wine

47
Q

What are filter pads made of?

A

Cellulose
Pads can be reused
The plates are expensive

48
Q

Pros/cons of cross-flow membrane filtration?

A

Pros: even dirty wines can be filtered.
Absolute filtering

Expensive
Flow rate decreases eventually
Clogs easily

49
Q

What is ultra filtration?

A

Cross flow filtration

Membranes can filter out individual components of a wine

50
Q

What is reverse osmosis?

A

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
Q

What is osmotic distillation?

A

high quality grape concentrates

Water vapour passes from grape juice through membrane into brine

52
Q

What are the main instability problems for wine?

A

Tartrate instability
Oxidation
Microbial spoilage

(also proteins, phenolics, copper, iron)

53
Q

What compound precipitates out when it comes to tartrate instability?

A

Potassium bitartrate

Calcium tartrate issues are less common but can happen. Not as easy to prevent

54
Q

How to prevent tartrate instability?

A

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
Q

What level should free sulfur be to prevent oxidation?

A

20 mg/L

56
Q

What microorganisms can survive in wine?

A

Lactic bacteria
Acetic bacteria
Yeast

57
Q

How is ethyl acetate created?

A

Acetic bacteria convert alcohol into acetic acid (vinegar) which binds to alcohol.

58
Q

What are some examples of spoilage yeasts?

A

Candida (surface spoilage yeasts) - causes unwanted flor to bloom
Brettanomyces (found in wood)

59
Q

What is acetaldehyde?

A

The yeasty taste that flor gives off

60
Q

What does sorbic acid do?

A

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
Q

What is the max permitted iron concentration in wine?

A

10mg/L

62
Q

What is the max permitted copper concentration in wine?

A

EU:1mg/L
USA: .5mg/L

63
Q

What are the steps taken when bottling a wine?

A

Pre-bottling analysis of wine
Checking quality of packaging
Monitoring bottling operation
Post-bottling analysis

64
Q

What are appropriate free SO2 levels in wine while aging in bulk?

A

25-30 reds

35 whites

65
Q

What is ISO 9001?

A

A common process attempted by members of the wine industry

66
Q

What are halo-anisoles?

A

Corkiness or mustiness

67
Q

What are some ways to analyze a wine before bottling?

A

High performance liquid chromotography
Fourier Transform Infrared Spectroscopy
Rapid DNA

68
Q

Sugar limits for still wines in EU?

A

Dry: <4g/L
Medium-dry: <12g/L
Medium: 12-45 g/L
Sweet: >45g/L

69
Q

Sugar limits for sparkling wines in EU?

A 
Brut nature: <3g/L
Extra Brut: <6g/L
Brut: <12g/L
Sec: 17-35g/L
Demi-sec: 33-50
doux: >50
70
Q

What is titratable acidity?

A

Total acidity
Expressed as equivalent of g/L tartaric acid (or sulfuric in France)
Min 4.5g/L
MOst have 5-7g/L

71
Q

What pH range do most wines fall in?

A

2.8-4
Below 3 is rare
Softer, ripe reds are above 2.7

72
Q

How much dissolved CO2 do most young white wines have?

A

600-1000mg/L

73
Q

What is TDE?

A

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
Q

What equipment is necessary for bottling?

A 
Membrane filter
Bottle rinser
Filler
Corker
Labeller
75
Q

What does modern bottling do?

A

Eliminates yeast or bacteria that could harm wine through Filtration or heat treatment

76
Q

What is flash pasteurization?

A

Kill microbes by heating wine to 80-90C for a few seconds the rapid cooling

77
Q

What is tunnel pasteurization?

A

high temperature for a medium length of time (sprayed by hot water after bottling) over 80C for 15 minutes

78
Q

What is a common cork size?

A

44x24

79
Q

What is a cork tree called?

A

Quercus suber

80
Q

Bottling: How to test for SO2

A

titration of a known volume of the wine with a concentration of iodine after treating with alkaline solution

81
Q

Bottling: How to test for VA

A

Simple glass still that is steam distilled and collected

82
Q

Bottling: How to test for alcohol

A

Distillation and hydrometrics

83
Q

Bottling: How to test forresidual sugar

A

fehlings titration reaction with copper salts

84
Q

Bottling: How to test for malic and lactic acid

A

Paper chromatographic proedure

85
Q

Bottling: How to test for tartrate instability

A

Filtered sample in -4C bath for 72 hours

86
Q

Bottling: How to test for protein stability

A

Filtered sample heated to 80C for 6 hours

87
Q

Bottling: How to test for sorbic acid

A

Colorimetric procedure

88
Q

how to test for extra copper

A

Gas chromotography. Fill a clear bottle with wine and place it on a window in sun for 7 days

89
Q

How to check for excess iron

A

Half filled clear bottle of wine in a cool dark place for 48 hours

Viticulture/Vinification (7 decks)

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