Post-Fermentation Clarification Flashcards
What is fining?
Fining agent added to speed up process of precipitation of suspended material in wine
What origins can fining agents be?
Protein and mineral
How does fining work?
-fining agent removes small proportion of unstable colloids from wine
-helps clarify stabilise wine against formation of hazes later in the bottle
-fining agent must have opposite charge to colloid, attract to each other, form solid big enough to be filtered out by racking/filtration
Other than clarify, what else can fining agents do?
-remove harsh tannins in red
-remove browning in whites
What do you have to be careful of when fining?
-not to remove desirable compounds
-not over fining- make wine unstable
What are the 3 categories of fining agents? (What do they remove?)
- Remove unstable proteins
- Remove phenolics that contribute undesirable colour and bitterness
- Remove colour and off odours
When is it necessary and when is it not necessary to remove proteins during fining?
-not necessary for reds- these bind with tannins and precipitate naturally, removed when racked
-necessary with whites and roses- agglomerate into visible haze if warmed up- bentonite
What is bentonite and when is it used?
-form of clay- absorbs unstable proteins and unstable colloidal colouring
-used for removing unstable proteins
What are the fining agents used to remove unstable phenolics which contribute undesirable colour and bitterness
-egg whites
-casein
-isinglass
-gelatine
-vegetable protein products
-pvpp
What is the fining agent used to remove colour and off-ordours?
charcoal
What are the 2 types of filtration?
Depth filtration and surface filtration
What is depth filtration?
-trapes particles in filter
-can cope with fluid with many particles (from pressing and lees)
-small particles get trapped
What are the advantages of depth filtration?
Doesn’t block easily
What are the disadvantages of depth filtration?
Not absolutely reliable- if too much pressure/used for too long- some particles make their way through filter
What is diatomaceous earth filter?
-most common form of depth filter
-once it has been processed, pure silica and inert
-DE is wetted, used as a filter medium
-wine sucked by vaccum from outside of rotary drum, through the DE, to inside of drum
What are the advantages of diatomaceous earth filter?
-can filter thick, cloudy wine
-oxaditive process
How can you make diatomaceous earth filter inert?
-use an enclose DE filter- flush with inert gas
What is a membrane filter?
-catches particles that will not go through pore size of filter
What is the difference between a depth filter and a membrane filter?
-membrane filter slower than depth filter as pore sizes are smaller
-membrane filter must be pre-filtered or could get blocked
-membrane is small investment, but cartridges are expensive
membrane filter is final precaution before bottling to ensure wine completely clear and microbiologically stable
What is membrane filtering sometimes called?
sterile filtering- yeasts and bacteria been removed= wine microbiologically stable
What is a cross flow filter?
-allows wine to pass through filter while uniquely cleaning surface of filter
-solid particles can’t pass through filter
What are the advantages of a cross flow filter?
-cleans as it works
-can filter wine with high load of particles or lees very quickly
-no need to buy cartridge’s, sheets, or dispose of eath
-(but high initial investment)
What is cold stabilisation?
-removing tartrates
-chilling wine to -4 for 8 days to allow crystals to form before bottling
-filter out
What are the disadvantages of cold stabilisation?
-cost of equipment and refrigerating the wine
What must be removed before cold stabilisation?
colloids- by fining- could prevent crystals from forming
What is contact process?
-quicker, continuous, more reliable, cheaper form of cold stabilisation
-add potassium bitartrate to wine to speed up start of crystallisation, chill to 0 degrees for one to 2 hours
-filter tartrates out
How can you ensure microbial stability?
-residual sugar left in wine= re-ferment in bottle
-filter yeast- sterile filtration
-add so2 and sorbic acid= inhibits yeast from growing
-disad- can smell effect of sorbic acid at low level
-v few microbes can live in wine w low ph and high alcohol, except:
–lactic acid bacteria
–acetic acid bacteria
–brettanomyces
What happens to wines with lactic acid bacteria where malo hasn’t been carried out?
-malo likely to start again in bottle
-remove by ensuring malo been completed or filtering out lactic acid bacteria
