Level 4 D1 Chap 15 - Finishing and Packaging Flashcards
What steps are involved in finishing a wine ahead of packaging?
All optional/ as required
8 weeks ahead or more: blend, analyse and adjust alcohol, acidity and tannins
4-6 weeks: Check protein and tartrate stability for further fining
1-2 weeks: Add any sweetening
2-3 days: Test filterability of wine
0-1 days: adjust SO2 and oxygen
During bottling: quality sample for SO2 and O2
What techniques clarify wine?
Sedimentation - premium/super-premium
Centrifugation - high-volume wineries
Fining - sounds very tricky; test then fine; then must still filter!
Filtration - most common way of clarifying wine
How is sedimentation carried out?
Leave the wine to settle and rack off.
It is a slow process suitable for premium/ super premium wines.
How is centrifugation carried out?
Spin the wine at high speed in a centrifuge.
The capital investment is high, so it is normally used in high-volume wineries
What types of fining agent are there?
Ones that remove:
- unstable protein: e.g. Bentonite (mostly white wines)
- phenolics with undesirable colour & bitterness: e.g.: egg albumin;
gelatine, casein; isinglass; vegetable protein; PVPP - colour and off-odours: charcoal
How is fining carried out?
Small sample testing helps determine the desired quantity of fining agent.
Agents have the opposite charge to the colloid, bind to it, and form a larger particle that settles faster.
List fining agents that remove phenolics, the agent properties and typical target wines
Egg white: removes harsh tannins. It is an allergen
Gelatin: protein collagen from pork removes bitterness in red wine and browning in white wine
Casein: milk protein that removes browning from white wine
Isinglass: protein collagen from fish bladders that clarifies white wines; makes them bright.
Vegetable proteins: suitable for vegan friendly wine; removes browning from white wines
PVPP (Polyvinylpolypyrrolidon): insoluble plastic powder removes browning and astringency from oxidised white wine
What are the main types of filtration?
Depth filtration:
- diatomaceous earth (pure silica)
- sheet filter (plate and frame, or pad filter)
Surface filtration
- membrane filter (removes yeasts and bacteria; normally very fine, “sterile filtering”; requires pre-filter so that membranes are not blocked; makes wine completely clear microbiologically stable). Cartridges are expensive.
- cross-flow filter (very fine, and high volume, but expensive capital investment)
STABILIZATION: What different types of compound stability does winemaking normally refer to?
Protein stability
- fining with bentonite is key
Tartrate stability - avoid crystals
Microbial stability
- sterile filtering is most common
What are a winemaker’s options to increase tartrate stability?
Cold stabilisation: hold wine at -4 °C for 8 days before filtering
Contact process: add potassium bitartrate, cool to 0°C for 1-2 hours and filter
Electrodialysis: charged membrane removes certain ions. High investment, but low running costs as no chilling is required
Carboxymethylcellulose (CMC): extracted from wood, used in white/rosé wine. Much cheaper than chilling
Metatartartic acid: Used in red wine in place of CMC, but time limited
What are target SO2 levels when finishing a wine?
Molecular SO2 changes with pH so there is a range: at a lower pH less SO2 is needed
- white wine: 25–45 mg/l (lower than for red wines due to lower pH)
- red wine: 30–55 mg/l
- sweet wine: 30–60 mg/l
How can dissolved oxygen levels be reduced?
Sparging (flushing) with inert gas to remove O2.
List common types of wine fault
- Cloudiness / hazes
- Tartrate formation
- Re-fermentation
- Cork taint
- Oxidation
- Volatile acidity
- Reduction
- Light strike
- Brettanomyces
How is cork taint identified?
Wet cardboard / wet leaves smell
What identifies oxidation as a fault in wine?
Prematurely brown in colour, loss of primary fruit and vinegary smell
