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WSET Diploma: Unit 2 > Vini 2: Fermentation > Flashcards

Vini 2: Fermentation Flashcards

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1
Q

Equation for fermentation:

A

C6H1206 -> 2C2H5OH +2CO2 + energy

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2
Q

Sugar needed to create each 1% alcohol by volume:

A

ca. 16-18g/L

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3
Q

Sugar preferred by most yeasts:

A

Glucose

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4
Q

Main by-product of fermentation:

A

Glycerol (glycerine) - colourless, viscous.

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5
Q

Other woods used as vessels:

A

Chestnut, cherry, acacia and walnut.

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6
Q

Main difference between wood and stainless steel:

A

Wood retains heat more readily.

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7
Q

Lining for cement tanks:

A

Epoxy resin, tiles, wax or glass.

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8
Q

Percentage abv. by which Saccharomyces yeasts will normally dominate:

A

4%

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9
Q

French for starter culture:

A

Le pied de cuve

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10
Q

Why use a starter culture?

A

To allow Saccharomyces to dominate immediately, to start fermentation quickly and to kill off other indigenous microflora. Slow fermentation is risky.

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11
Q

Measuring must density:

A

Keeping fermentation rate uniform is key. France: relative density/Baumé. Aus, NZ, USA: Brix/Balling. Germany, Switzerland: Oechsle (hydrometer). Italy: Babo. Austria: KMW.

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12
Q

Substance responsible for banana/pear drop aroma at low temps.:

A

Isoamyl acetate

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13
Q

Substance responsible for high levels of VA at low temps.:

A

Ethyl acetate

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14
Q

Pumping over, punching down and rack and return in French:

A

Le remontage, le pigeage et le délestage.

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15
Q

Level of unfermentable sugars even in driest wines:

A

Up to 2 g/L

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16
Q

Getting a stuck fermentation started again:

A

Increasing levels of nutrients rich in nitrogen: di-ammonium phosphate (DAP) or thiamine (vitamin B). Oxygenation early on is also key.

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17
Q

Yeasts deprived of nitrogen:

A

They break down amino acids releasing hydrogen sulphide (H2S).

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18
Q

Typical fermentation temp. for white wine:

A

Between 14-20 deg, though can reach up to 25 in small barrels.

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19
Q

Cooling of newly fermented white wine:

A

Down to 12 deg to aid yeast settling.

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20
Q

Addition of SO2 to avoid MLF in whites:

A

40-50mg/L.

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21
Q

Temp. of white wine if MLF desired:

A

17-20 deg. Lees stirred once a week.

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22
Q

Reduced hydrogen sulphide can produce…

A

Mercaptans - onion-smelling substance.

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23
Q

Treating severely reduced wine:

A

Pass through a copper pipe or add copper sulphate.

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24
Q

Aim of using rollers for bâtonnage:

A

Stirring in less oxygen.

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25
Q

The three rosé winemaking techniques:

A

Drawing-off/saignée, direct pressing and blending.

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26
Q

Drawing-off/saignée:

A

Most common. Destemmed, crushed, sulphited grapes. Mild colour, treated as white must. Cool temps. with no oxygen. MLF blocked. Young consumption.

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27
Q

Direct pressing:

A

Direct press of freshly harvested grapes. Care taken to reduce tannin extracted. Pale colour.

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28
Q

Blending:

A

Rosé Champagne and New World rosés. Not allowed in EU.

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29
Q

Two kinds of phenolic compounds:

A

Non-flavonoids (simpler) and flavonoids (catechins and anthocyanins).

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30
Q

What are tannins?

A

Polymerised catechin molecules.

31
Q

What is polymerisation?

A

The joining together of compounds.

32
Q

Filling vessels before fermentation:

A

No more than 80% capacity, as fermenting mass will expand.

33
Q

Addition of SO2 for red wines:

A

10-80 mg/L.

34
Q

Cold soaking:

A

Sub-15 degs for 3-7 days. Higher SO2 amounts: 80-100mg/L to stop spontaneous fermentation happening.

35
Q

Typical fermentation temps. for reds:

A

20-32 degs.

36
Q

Thermovinification:

A

Heating to 60-80 degs for 20-30 mins to aid colour extraction. Good for rotten grapes as damaging oxidative enzymes are killed.

37
Q

Regularity of pumping over (remontage):

A

1-3 times a day. Used for Cab Sauv and Merlot in particular.

38
Q

Advantage of punching down (pigeage):

A

Gentle extraction. Common for Syrah and Pinot Noir. Usually done 1-3 times a day.

39
Q

Rack and return (délestage):

A

Usually done twice during fermentation. Excellent aeration.

40
Q

Submerged cap process:

A

Using head boards secured near top of tank. Makes extraction difficult.

41
Q

Rotovinification:

A

Efficient, but pricey and risks over extraction.

42
Q

Autovinification:

A

Also known as Algerian Ducellier system. Fully automated.

43
Q

To remember when deciding the duration of skin contact:

A

The quality of extracted substances is directly proportional to fruit quality.

44
Q

Typical skin contact durations:

A

Light, easy-going reds - 8 days. Full-bodied reds for ageing - 3 weeks. Top vintages - 1 month or more.

45
Q

Why are press wine and free-run wine kept separate until blending?

A

Because press wine may well require a greater level of fining than the free-run wine.

46
Q

What is released into red wine as lees autolyse?

A

Mannoproteins - boost tartrate stability.

47
Q

Flash expansion/Flash détente:

A

Pre-heated grapes (65-90 degs) into vacuum. Cooled rapidly and cells destroyed. Tannins and anthocyanins released.

48
Q

Three species of bacteria capable of carrying out MLF:

A

Lactobacillus, Leuconostoc and Pediococcus.

49
Q

MLF equation:

A

Malic Acid -> Lactic Acid + Carbon Dioxide gas

50
Q

Substance responsible for buttery richness in wines:

A

Diacetyl.

51
Q

What lactic acid bacteria need:

A

pH 3.3-3.5, temp. 17-20 degs, less than 50mg/L total SO2 and nutrients.

52
Q

Stopping MLF:

A

Early clarification (fewer nutrients), SO2 added after fermentation (free levels above 25 mg/L, sub 12 deg temps, pH lower than 3.1 etc.)

53
Q

Encouraging MLF:

A

Keeping wine on lees (nutrients), low SO2, warm temps. (18-22 degs), adding freeze-dried MLF bacteria and lifting pH to over 3.3.

54
Q

Checking success of MLF:

A

Checking reduction or complete absence of malic acid. Chromatographic test/enzymatic analysis.

55
Q

Effects of MLF:

A

Deacidification, stability, loss of primary fruit, added aroma, increased VA and increased spoilage possibility if left unchecked.

56
Q

La liqueur de tirage:

A

Sucrose (cane/beet) with selected yeast strand to stimulate second fermentation in sealed bottle. Abv. up 1.2-1.3%.

57
Q

Riddling in French:

A

Le remuage.

58
Q

Dosage/la liqueur d’expédition:

A

Blend of sugar and wine that determines overall sweetness level.

59
Q

Cork and wire cage in French:

A

Le muselet.

60
Q

Tank method/cuve close/Charmat:

A

Second fermentation takes place in sealed tank. Cheaper - Sekt and Prosecco. Coarser, broader bubbles.

61
Q

Transfer method:

A

Adapted version of Méthode Traditionelle: secondary fermentation in bottle, but dosage done in pressurised tank. Mid-market NW sparkling.

62
Q

Port/VDN fortification:

A

During fermentation. Port: 6-9% abv reached when wine drained from skins and spirit of 77-79% abv added - one part spirit to four parts wine. Overall abv hits 18-19% and yeast dies.

63
Q

Vessel for port maturation:

A

550l ‘pipe’.

64
Q

Pressing of Palomino:

A

Usually in horizontal press (Vaslin or Willmes). First 70% of juice its free-run for Fino and Manzanilla. Next 20% for Oloroso.

65
Q

Vessel for Sherry:

A

600/650l oak butts.

66
Q

Removal of wine from individual barrel in solera structure:

A

No more than one third at a time.

67
Q

Average ageing for Sherry styles:

A

3-5 for Fino, Amontillado and Oloroso up to 10 years.

68
Q

Sweetening of sherries

A

RCGM for Pale Cream and PX for Cream Sherry and Sweet Oloroso.

69
Q

Before bottling Sherry:

A

Cold stabilisation. Routine membrane filtration of Fino and Manzanilla to remove flor.

70
Q

Three ways of making a sweet wine:

A

Interrupting the fermentation, adding a sweet component and concentrating existing sugars.

71
Q

Stopping the fermentation:

A

Fortification or adding SO2/cooling the temp. Lower abv. and cheaper.

72
Q

Adding a sweet component:

A

RCGM or süssreserve (unfermented grape juice of same origin or quality).

73
Q

Concentrating existing sugars:

A

Drying on mats (Vin Santo, PX), on vines (Passerillage), freezing, noble rot (Botrytis cinerea) - Riesling, Sémillon and Chenin Blanc.

WSET Diploma: Unit 2 (8 decks)

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