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
What causes excessive volatile acidity and how is it identified?
Acetic acid bacteria may arise if levels of SO2 are too low. These bacteria produce acetone/vinegar smell
What causes reduction and at what stages in winemaking does it typically occur?
Volatile, reductive sufur compounds are formed either under yeast stress in fermentation (normally low nitrogen), or exhaustion of oxygen in closed vessels in lees ageing.
How can reduction be avoided?
Ensure yeast has sufficient nutrients and oxygen
Lower SO2 levels (especially with impermeable closures)
What is light strike and how is it avoided?
Predominantly UV light causes the production of volatile sulphur compounds.It can be avoided by using dark glass, and storing wine out of daylight and fluorescent displays.
What is ‘brett’?
Brettanomyces is a yeast that creates animal or farmyard smells
It is considered a fault in high quantity. In low quantity it may add complexity to a wine.
How is ‘brett’ avoided?
The cells can survive in wood in old and new barrels
It can hopefully be avoided through:
- excellent hygiene
- maintaining effective SO2 levels
- keep pH low
- keep fermentation and MLF as close together as possible so that SO2 can be added as soon as possible
Once packaged, what sources of oxygen can impact a wine?
Winemakers measure “total package oxygen.”
- Dissolved oxygen
- Headspace
- Contained in the cork/closure
- Oxygen transmission rate (OTR) through the cork or closure
What are the advantages and disadvantages of packaging in glass?
Advantages:
- inert
- easy to sterilise
- inexpensive
- recyclable
- impermeable
Disadvantages:
- high carbon footprint (manufacture and weight to transport)
- fragile
- rigid (headspace)
- risk of light strike
What are the most common alternatives to glass packaging?
Plastic - cheap, light, but not suitable for long term
Bag-in-box / pouch - easy storage, lightweight, no headspace, but not suitable for long term
Brick/Tetra Pak - easy storage, light but costly equipment to set up
Can - light weight, robust, impermeable, needs to be lined with plastic
