Vini 2: Fermentation Flashcards Preview

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Flashcards in Vini 2: Fermentation Deck (73)
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1

Equation for fermentation:

C6H1206 -> 2C2H5OH +2CO2 + energy

2

Sugar needed to create each 1% alcohol by volume:

ca. 16-18g/L

3

Sugar preferred by most yeasts:

Glucose

4

Main by-product of fermentation:

Glycerol (glycerine) - colourless, viscous.

5

Other woods used as vessels:

Chestnut, cherry, acacia and walnut.

6

Main difference between wood and stainless steel:

Wood retains heat more readily.

7

Lining for cement tanks:

Epoxy resin, tiles, wax or glass.

8

Percentage abv. by which Saccharomyces yeasts will normally dominate:

4%

9

French for starter culture:

Le pied de cuve

10

Why use a starter culture?

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

11

Measuring must density:

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

12

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

Isoamyl acetate

13

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

Ethyl acetate

14

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

Le remontage, le pigeage et le délestage.

15

Level of unfermentable sugars even in driest wines:

Up to 2 g/L

16

Getting a stuck fermentation started again:

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

17

Yeasts deprived of nitrogen:

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

18

Typical fermentation temp. for white wine:

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

19

Cooling of newly fermented white wine:

Down to 12 deg to aid yeast settling.

20

Addition of SO2 to avoid MLF in whites:

40-50mg/L.

21

Temp. of white wine if MLF desired:

17-20 deg. Lees stirred once a week.

22

Reduced hydrogen sulphide can produce...

Mercaptans - onion-smelling substance.

23

Treating severely reduced wine:

Pass through a copper pipe or add copper sulphate.

24

Aim of using rollers for bâtonnage:

Stirring in less oxygen.

25

The three rosé winemaking techniques:

Drawing-off/saignée, direct pressing and blending.

26

Drawing-off/saignée:

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

27

Direct pressing:

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

28

Blending:

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

29

Two kinds of phenolic compounds:

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

30

What are tannins?

Polymerised catechin molecules.