D1.C15. Finishing and Packaging Flashcards
What should the wimemakers do, to produce a clear and stable wine?
Wines should be clarified and stabilised before being bottled and packaged
Name the practices used for the clarification of the wine.
- Sedimentation
- Centrifugation
- Fining
- Filtration
Number of rackings required depend on which factors?
- Shape of the container: The larger the storage vessel, the greater the number of rackings required to avoid a thick layer of sediment
- Volume of the wine
- Available labour
Why do some of the wines are clarified only by sedimentation?
Some winemakers believe that clarification by sedimentation avoids the potential loss of texture and flavour that may occur if the wine is fined or filtered
Why sedimentation is usually only suitable for premium or super-premium priced wines?
As sedimentation takes time, this has a cost
In which condition, sedimentation happens as a part of the process?
Barrel aging
In many cases, why will the winemaker accelerate the process of clarification?
In high volume production the speed of processing wine is financially important
Centrifugation can be a substitute for…
Depth filtration
When is centrifugation advantageous?
For the wines with a lot of matter in suspension
Why is centrifugation practiced only in high-volume wineries?
Because of the cost of the machine
What are the origins of fining materials?
- Protein
- Mineral
What is the aim of fining?
- To remove a small proportion of unstable colloids (microscopic particles too small to be removed by filtering) from the wine
- Clarify the wine
- Stabilize the wine against the formation of hazer later in the bottle
What do winemakers do, before using fining agents? Why?
- They conduct laboratory trials before using fining agents to ensure that the minimum effective amount is used
- Many fining agents can remove desirable compounds from wine or make the wine unstable when too much is added (over-fining) and therefore it is important to add
only the minimum effective amount
What are the solutions that fining agents can offer other than clarifying the wine?
- Removal of harsh tannins in red wine
- Correction of browning in white wines
Name the 3 categories of common fining agents.
- Those that remove unstable proteins
- Those that remove phenolics that contribute undesirable colour and bitterness
- Those that remove colour and off-odours.
Why is removal of unstable proteins not needed for red wines?
- They bind with tannins, precipitate naturally and are removed when the wine is racked
What happens if the proteins in the white and rose wines are not fined?
They can agglomerate into a visible haze if warmed up
Which fining agent is used to remove unstable proteins?
Bentonite
What is bentonite?
It is a form of clay
What is the advantage of bentonite?
It has a minimal effect on the flavour and texture
What are the disadvantages of bentonite?
- It leads to some colour loss in red wines
- Produces large amounts of sediment, and so wine is lost when it is racked off
Name the fining agents that remove phenolics that contribute undesirable colour and bitterness
- Egg white
- Gelatin
- Caseine
- Isinglass
- Vegetable protein products
- PVPP ( Polyvinylpolypyrrolidone)
What re the pros and cons of egg white?
- Pro: It is gentle to the wine
- Con: It is an allergen, not suitable for vegan wines
What are the effects of gelatine on wine?
- Aids clarification
- Removes bitterness and astringency in red wines
- Removes browning in white wines
Why must gelatine be added in the smallest effective amount?
As it is easy to over-fine with gelatine, stripping flavour and character, and creating the risk of a protein haze forming later
What are the actions of casein on wine?
- Removes browning from white wines
- Clarifies wine
What are the cons of casein?
- It is an allergen
- Not suitable for vegans
What are the actions of isinglass on wine?
Very effectively clarifies the white wines, giving them a bright appearance
Why must isinglass be added in the smallest effective amount?
To avoid potential for the formation of a protein haze later and the creation of a fishy smell
Is isinglass suitable for vegetarians and vegans?
No, because it is derived from fish bladders
Vegetable protein products are produced from which vegetables?
Potato or legumes
What is PVPP (Polyvinylpolypyrrolidone)?
It is an insoluble plastic in powder form
What are the actions of PVPP on wine?
- It removes browning and astringency from oxidised white wine
- It is rarely used on red wines, but can reduce astringency and brighten the colour
Which of the fining agents that remove phenolics that contribute undesirable colour and bitterness are not suitable for vegans?
- Egg white
- Gelatine
- Casein
- Isinglass
Which of the fining agents that remove phenolics that contribute undesirable colour and bitterness are not suitable for vegetarians?
- Isinglass
- Gelatine
Which fining agents can be used both for must and wine
- Bentonite
- Gelatine
- Caseine
Name one fining agent that removes colour and off-odours?
Charcoal
Why care has to be taken while using charcoal?
Because it can over-fine easily removing desirable aromas and flavours. One option is to treat only one batch of the affected wine and then blend it with the rest of the wine to reduce this effect
What are the advantages of depth filtration?
- It can cope with fluid with many particles in it
- It does not block easily
Why is depth filtration not an absolute filter?
If too much pressure is applied or if the filter is used for too long, some particles will make their way through the filter
What are the types of depth filtration?
- Earth filters (using diatomaceous earth)
- Sheet filters (plate and frame or pad filters)
What is diatomaceous earth?
It is pure silica
Rotary drum vacuum filters using diatomaceous earth can filter..
Very thick and cloudy wine
What is the advantage of diatomaceous earth?
It comes in a range of particle sizes and thus can remove large or very small (e.g. yeast) particles
What are the disadvantages of diatomaceous earth?
- It is an oxidative process
- Initial investment in machinery is high, though the per litre cost after that is small
- It must be disposed of responsibly, so increasing the cost
How can oxidation be prevented rotary vacuum filters?
Enclosed DE filters flushed with an inert gas
Why is filtration quicker in sheet filters as the number of the sheets in the filter increase?
Because any portion of wine only passes through one sheet
Can sheet filters be used as an absolute filter?
Yes, very fine graded sheets can be used to remove any remaining yeasts at bottling
How is the economic burden of sheet filters?
- They require investment initially but the cost of filter sheets is low
- Trained personnel must operate them to work properly
Why are the membrane filters slower than depth filters?
As the pores are smaller, often less than 1 micron
Why should the wines be pre-filtered first before filtering by membrane filters?
Otherwise the membrane filters are easily blocked
Why are membrane filters used usually as a final precaution before bottling?
To ensure that the wine is completely clear and microbiologically stable
Can membrane filtration be always regarded as a “sterile filtration?
If the filter size is over than 1 micron, then it can not be regarded as a sterile filter
How is the economic burden of membrane filters?
The initial investment is small, but the cartridges are expensive and an ongoing cost
What is the advantage of cross-flow filters when compared with membrane filters?
They can filter wine with a high load of particles or lees very quickly
How is the economic burden of cross-flow filters?
- Machines are expensive but no replacement sheets, cartridges or earth to buy or dispose
- They are more suitable for large and/or well- funded wineries
What does stabilization mean?
It refers to several winemaking interventions, if not carried out, could lead to undesired effects in the finished wine
How is protein stability achieved?
By fining with bentonite
What are tartrates?
Potassium bitartrate and, less frequently, calcium tartrate, are harmless deposits of crystals that can form in the finished wine
Why all high-volume winemaking and many small scale operations will seek to prevent tartrate deposits?
Because many customers will regard the tartrates as a fault
Name the options to achieve tartrate stability
- Cold stabilisation
- Contact Process
- Electrodialysis
- Ion exchange
- Carboxymethylcellulose (CMC)
- Metatartaric acid
What are the traditional and contemporary methods to achieve tartrate stability by cold?
- Traditional: To extent by the wine being kept in a cold cellar for months through the winter
- Contemporary: wine can be held at –4°C for around eight days so that the crystals form before bottling
What is the prerequisite before a cold stabilisation practice? Why?
Removal of colloids by fining as they could prevent the crystals from forming
What are the drawbacks for cold stabilisation?
- Cold stabilisation requires the equipment and the cost of energy to refrigerate the wine
- It only removes the more common potassium bitartrate, not calcium tartrate
How is contact process performed to achieve tartrate stability?
- Potassium bitartrate is added to the wine and speeds up the start of the crystallisation process
- Wine is usually cooled to around 0°C (32°F) and after one or two hours the resulting crystals are filtered out
What are the advantages of contact process?
- Quicker
- Continuous
- More reliable
- Cheaper
What is the working principle of electrodialysis to achieve tartrate stability?
It uses a charged membrane to remove selected ions
What are the advantages of electrodialysis
- Although the initial investment is high, total cost is lower than cold stabilisation
- It uses less energy
- It is faster
- It removes both potassium and calcium ions and to a smaller extent, tartrate ions
- It is allowed in EU and other territories
What is the working principle of ion exchange?
It does not remove tartrate but it replaces potassium and calcium ions with hydrogen or sodium ions, which will not drop out of solution
Why is ion exchange not allowed for tartrate stabilisation in some territories?
Because, it replaces the potassium with sodium, which is not conducive to health
What is the working principle of CMC for tartrate stabilisation?
It prevents tartrates from developing to a visible size
What is the advantage of CMC for tartrate stabilisation?
- It is much cheaper than chilling
- It is widely used on inexpensive white and rosé wines
What are the disadvantages of CMC for tartrate stabilisation?
- Not suitable for red wines as it reacts with tannins and causes haze
- It keeps the wine stable for a few years
What is the working principle of metatartaric acid for tartrate stabilisation?
It prevents the growth of potassium bitartrate and calcium tartrate crystals, reducing the need for cold stabilisation