15. Finishing and Packaging Flashcards
(30 cards)
What are proteins?
Building block for all organic life, and are classified as colloids (due to their molecule size)
what are unstable colloids
particles that that include proteins, phenolics (tannins and anthocyan), and polysaccharides (pectin/complex carbohydrate/gelatine like)
what is denaturing;
when unstable colloids slowly change their nature as molecules rearrange causing deposits in final wine
what are the three effects of cork taint
- unattractive, mouldy, wet cardboard smell
- reduces the fruit character
- shortens the finish of wines
How is cork taint formed
- by TCA - TriChloroAnisole
- formed in cork by actions of phenolic compounds and chlorine
- cork bark plantations were affected when Organochlorine insecticides surrounding the plantations
how can you reduce cork taint
- cleaning corks with stream extraction
- quality control and new technology;
- impermeable cork membrane
- using alternative closures
what are the effects of oxidisation
- 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
How does Hyper-oxidation affect a white wine
- 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
What are acceptable levels of VA
0.3g/l - 0.5g/l
What are the relevant amounts of VA in reference to their respective aromas
- Acetic acid; 1.5g/ L (vinegar)
- Ethyl acetate; 250mg/L (nail polish remover)
- formation of acetic acid result of;
- acetic acid bacteria
- inadequate levels of SO2
- excess exposure to oxygen.
How do you manage VA in the winery?
- 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
what are the strains of acetic bacteria;
Aceobactor (wine)
Gluconobacter (must)
Explain the formation of VA in wine
Volatile acidity is created by acetic acid bacteria and yeast, which convert alcohol into acetic acid and ethyl acetate
What is the difference between hyperoxidation and microoxygenation
hyperoxidation involves intentionally exposing grape juice or must to high levels of oxygen before fermentation, aiming to reduce subsequent oxidation during aging and fermentation.
Micro-oxygenation, on the other hand, is a post-fermentation technique where controlled amounts of oxygen are added to wine, often with oak, to promote positive reactions like tannin softening and improved color stability.
How much YAN does yeast need for positive ferment?
150mg/L
How can you avoid reduction
can be avoided by making sure yeast is not stressed.
This is done by ensuring it has sufficient nutrients and oxygen
Make sure must is at an adequate temperature.
SO2 may need to be lowered
(especially if the closure used allows very little oxygen ingress)
- What are VSC’s
potent aromas with low detection thresholds
can be positive such as; grapefruit, passionfruit aromas (thoils)
What are some examples of negative reductive aromas and chemical name?
Hydrogen Sulfide (H2S) - Rotten eggs, drain
Ethanethoil - Rotten onion, burnt rubber
Dimethyl sulfide - Canned corn, cooked cabbage
Examples of winemakers in burgundy wineries which are for or against reductive winemaking
- Domaine Comtes Lafon (against)
- Coche-Dury (for)
- Domaine Leflaive (against)
What is the difference between cork taint and cork fault
cork taint is derived from winemaking ei; VA, oxidation, brettanomyces and reduction
and wine taint comes from outside of the winemaking process ei. TCA (Cork Taint), smoke taint, eucalyptus taint
What are the negative effects of Brettanomyces
- off-flavours dominate,
- fruity flavours are reduced
- acidity or tannins of wine becomes more prominent.
The key ways to avoid Brettanomyces are:
- excellent hygiene
- maintaining effective SO2 level
- keeping pH levels low
- keeping the period between the end of alcoholic fermentation and malolactic conversion as short as possible
- Avoiding use of barrels & cross contamination
What methods can you use to cure Brettanomyces?
- PVPP (insoluble plastic)
- Activated charcoal
- Fining and Filtration
- DMDC (dimethyl dicarbonate, commercial name: Velcorin)
