Post-Fermentation Clarification

Question 1

What is fining?

Answer 1

Fining agent added to speed up process of precipitation of suspended material in wine

Question 2

What origins can fining agents be?

Answer 2

Protein and mineral

Question 3

How does fining work?

Answer 3

-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

Question 4

Other than clarify, what else can fining agents do?

Answer 4

-remove harsh tannins in red
-remove browning in whites

Question 5

What do you have to be careful of when fining?

Answer 5

-not to remove desirable compounds
-not over fining- make wine unstable

Question 6

What are the 3 categories of fining agents? (What do they remove?)

Answer 6

1. Remove unstable proteins
2. Remove phenolics that contribute undesirable colour and bitterness
3. Remove colour and off odours

Question 7

When is it necessary and when is it not necessary to remove proteins during fining?

Answer 7

-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

Question 8

What is bentonite and when is it used?

Answer 8

-form of clay- absorbs unstable proteins and unstable colloidal colouring
-used for removing unstable proteins

Question 9

What are the fining agents used to remove unstable phenolics which contribute undesirable colour and bitterness

Answer 9

-egg whites
-casein
-isinglass
-gelatine
-vegetable protein products
-pvpp

Question 10

What is the fining agent used to remove colour and off-ordours?

Answer 10

charcoal

Question 11

What are the 2 types of filtration?

Answer 11

Depth filtration and surface filtration

Question 12

What is depth filtration?

Answer 12

-trapes particles in filter
-can cope with fluid with many particles (from pressing and lees)
-small particles get trapped

Question 13

What are the advantages of depth filtration?

Answer 13

Doesn’t block easily

Question 14

What are the disadvantages of depth filtration?

Answer 14

Not absolutely reliable- if too much pressure/used for too long- some particles make their way through filter

Question 15

What is diatomaceous earth filter?

Answer 15

-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

Question 16

What are the advantages of diatomaceous earth filter?

Answer 16

-can filter thick, cloudy wine
-oxaditive process

Question 17

How can you make diatomaceous earth filter inert?

Answer 17

-use an enclose DE filter- flush with inert gas

Question 18

What is a membrane filter?

Answer 18

-catches particles that will not go through pore size of filter

Question 19

What is the difference between a depth filter and a membrane filter?

Answer 19

-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

Question 20

What is membrane filtering sometimes called?

Answer 20

sterile filtering- yeasts and bacteria been removed= wine microbiologically stable

Question 21

What is a cross flow filter?

Answer 21

-allows wine to pass through filter while uniquely cleaning surface of filter
-solid particles can’t pass through filter

Question 22

What are the advantages of a cross flow filter?

Answer 22

-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)

Question 23

What is cold stabilisation?

Answer 23

-removing tartrates
-chilling wine to -4 for 8 days to allow crystals to form before bottling
-filter out

Question 24

What are the disadvantages of cold stabilisation?

Answer 24

-cost of equipment and refrigerating the wine

Question 25

What must be removed before cold stabilisation?

Answer 25

colloids- by fining- could prevent crystals from forming

Question 26

What is contact process?

Answer 26

-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

Question 27

How can you ensure microbial stability?

Answer 27

-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

Question 28

What happens to wines with lactic acid bacteria where malo hasn’t been carried out?

Answer 28

-malo likely to start again in bottle
-remove by ensuring malo been completed or filtering out lactic acid bacteria