15. Finishing and Packaging

Question 1

What are proteins?

Answer 1

Building block for all organic life, and are classified as colloids (due to their molecule size)

Question 2

what are unstable colloids

Answer 2

particles that that include proteins, phenolics (tannins and anthocyan), and polysaccharides (pectin/complex carbohydrate/gelatine like)

Question 3

what is denaturing;

Answer 3

when unstable colloids slowly change their nature as molecules rearrange causing deposits in final wine

Question 4

what are the three effects of cork taint

Answer 4

• unattractive, mouldy, wet cardboard smell
• reduces the fruit character
• shortens the finish of wines

Question 5

How is cork taint formed

Answer 5

• by TCA - TriChloroAnisole
• formed in cork by actions of phenolic compounds and chlorine
• cork bark plantations were affected when Organochlorine insecticides surrounding the plantations

Question 6

how can you reduce cork taint

Answer 6

• cleaning corks with stream extraction
• quality control and new technology;
• impermeable cork membrane
• using alternative closures

Question 7

what are the effects of oxidisation

Answer 7

• wine becomes prematurely brown in colour
  
  • loss of primary fruit
  • vinegary smell
  • aromas of; bruised apple and nuts, dried fruit, nuts/honey, dried roses, hay/dried flowers/parsley

Question 8

How does Hyper-oxidation affect a white wine

Answer 8

• causes phenolic compounds in the must to oxidize, which then precipitate out during clarification and fermentation.
  
  • one removed, the resulting wine is less susceptible to oxidation in the future

Question 9

What are acceptable levels of VA

Answer 9

0.3g/l - 0.5g/l

Question 10

What are the relevant amounts of VA in reference to their respective aromas

Answer 10

• Acetic acid; 1.5g/ L (vinegar)
• Ethyl acetate; 250mg/L (nail polish remover)

Question 11

• formation of acetic acid result of;

Answer 11

• acetic acid bacteria
  
  • inadequate levels of SO2
  • excess exposure to oxygen.

Question 12

How do you manage VA in the winery?

Answer 12

• Managing Volatile acidity in the Winery;

sorting fruit to exclude damaged grapes
scrupulous hygiene in the winery
Protecting wine from oxygen;
- keeping vessels topped up (and inert gas cover)
- careful racking
- maintaining adequate SO2 levels.
certain yeast strains can decease VA in final wine by a gram per L

Question 13

what are the strains of acetic bacteria;

Answer 13

Aceobactor (wine)
Gluconobacter (must)

Question 14

Explain the formation of VA in wine

Answer 14

Volatile acidity is created by acetic acid bacteria and yeast, which convert alcohol into acetic acid and ethyl acetate