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WsetDip D1 > 15.1 Post-Fermentation Clarification > Flashcards

15.1 Post-Fermentation Clarification Flashcards

1
Q

What is clarification?

A

Includes all the processes, physical and chemical, that are used to make wine clear

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2
Q

What is sedimentation?

A
  • suspended matter precipitating in a wine over time
  • wine is allowed to stand and the particles with higher density than wine will form a sediment at the bottom of the container
  • wine then be racked off, leaving the sediment behind
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3
Q

When will sedimentation happen naturally?

A
  • when wine is stored in cool cellar conditions

- if a wine is barrel aged

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4
Q

How many rackings are typically required?

A
  • depends on the size of the containers being used and the available labour
  • larger vessels = greater number of rackings required to avoid a thick layer of sediment
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5
Q

What are the benefits of sedimentation?

A
  • clarification by sedimentation avoids the potential loss of texture and flavour that may occur if the wine is fined or filtered
  • some premium wines are clarified only in this way
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6
Q

What types of wines is sedimentation used for? Why?

A
  • usually only suitable for premium or super-premium priced wines
  • takes time
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7
Q

Name 3 ways a winemaker can accelerate the clarification process.

A
  1. Centrifugation
  2. Fining
  3. Filtering
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8
Q

What is centrifugation?

A
  • a rapid process that spins the wine at high rotational speed to clarify it
  • can replace depth filtration and allow early bottling
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9
Q

What types of wines is centrifugation effective with?

A
  • wines with a lot of matter in suspension
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10
Q

What styles of wines is centrifugation typically used for?

A
  • high-volume wineries to spread the considerable cost of buying the machine
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11
Q

What is fining? Name 3 effects fining has on a wine.

A

A procedure in which a fining agent is added to speed up the process of the precipitation of suspended material in the wine

  1. removes a small proportion of unstable colloids
  2. clarifies
  3. stabilises against the formation of hazes later in the bottle
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12
Q

Of what origin can fining agents be?

A
  • protein or mineral origin
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13
Q

What are colloids?

A
  • microscopic particles too small to be removed by filtering
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14
Q

How do winemakers determine how much of a fining agent is used?

A
  • conduct laboratory trials before using fining agents to ensure that the minimum effective amount is used
  • compare the fined sample with the original wine before proceeding
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15
Q

Why is it important to not over-fine, and to only add the minimum effective amount?

A
  • can remove positive compounds from wine

- can make the wine unstable when too much is added

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16
Q

When choosing a fining agent, what factors are taken into consideration?

A
  • each fining agent has particular properties that can offer solutions to problems (e.g. removal of harsh tannins in red wines, browning in white wines)
  • fining agent must have the opposite charge from the wine colloid to be removed
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17
Q

Describe how fining works.

A
  • fining agent and the colloid attract each other

- form a solid large enough (sink to bottom of liquid) to be removed by racking or by filtration

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18
Q

What are the 3 categories of fining agents?

A
  1. those that remove unstable proteins
  2. those that remove phenolics that contribute undesirable colour and bitterness
  3. those that remove colour and off-odours
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19
Q

Why is it important to remove grape-derived proteins from white and rose wines? Why is it less important with red wines?

A
  • White: grape-derived proteins can agglomerate into a visible haze if warmed up (e.g. in transit) = a fault
  • Red: grape-derived proteins bind with tannins, precipitate naturally and are removed when the wine is racked
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20
Q

How are wines with grape-derived proteins fined?

A

With Bentonite

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21
Q

What is bentonite?

A

A form of clay which adsorbs unstable proteins and unstable colloidal colouring matter

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22
Q

What is the effect of bentonite on the final wine?

A
  • minimal effect on the flavour and texture of wine
  • leads to some colour loss in red wines
  • produces large amounts of sediment (wine is lost when racked)
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23
Q

Name 6 fining agents that remove phenolics that contribute undesirable colour and bitterness in wine.

A
  1. egg whites
  2. gelatin
  3. casein
  4. insinglass
  5. vegetable protein products
  6. PVPP
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24
Q

In what form are egg whites used to fine wines?

A

fresh or powdered form

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25
Q

For what types of wines are egg whites typically used as a fining agent? Why?

A
  • high-quality red wines
  • ability to remove harsh tannins and clarify wine
  • gentle
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26
Q

Why must egg whites be declared on a label if used in the EU?

A
  • it’s an allergen
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27
Q

What is gelatin?

A
  • A protein collagen extracted from pork
28
Q

What effect does gelatin have as a fining agent?

A
  • aids clarification
  • removes bitterness and astringency in red wine
  • removes browning in white wine pressings
29
Q

Why must one be careful when fining with gelatin?

A
  • must be added in the smallest effective amount
  • easy to over-fine with gelatin
  • stripping flavour and character
  • creating the risk of a protein haze forming later
  • not suitable for vegetarian wine as it is derived from animals
30
Q

What is casein?

A
  • A milk-derived protein
31
Q

What effect does casein have as a fining agent?

A
  • removes browning from white wines

- clarifies wines to some extent

32
Q

What is isinglass?

A
  • A protein collagen that very effectively clarifies white wines, giving them a bright appearance
  • derived from fish bladders
33
Q

Why must one be careful when fining with isinglass?

A
  • smallest effective amount must be added
  • potential for the formation of a protein haze later
  • the creation of a fishy smell
  • not suitable for vegetarians as it is derived from fish bladders
34
Q

What are vegetable protein products?

A
  • fining agents derived from potato or legumes

- suitable for vegan-friendly wines

35
Q

What is PVPP?

A
  • Polyvinylpolypyrrolidone
  • insoluble plastic in powder form
  • removes browning and astringency from oxidised white wine
  • gentler than charcoal
36
Q

What types of wines is PVPP used on? Rarely used on?

A
  • oxidised white wine

- rarely used on red wines (but can reduce astringency and brighten the colour)

37
Q

Name a fining agent that removes colour and off-odours.

A

Charcoal

38
Q

What does charcoal do?

A
  • removes brown colours (e.g. to create Pale Cream Sherry)

- removes some off-odours

39
Q

Why must one be careful when fining with charcoal? What solution can be used?

A
  • over-fines easily removing desirable aromas and flavours

- Solution: only one batch of the affected wine and then blend it with the rest of the wine to reduce this effect.

40
Q

What is filtration?

A

A physical separation technique used to eliminate solids from a suspension by passing it through a filter medium consisting of porous layers that trap solid particles, thus making the liquid clear

41
Q

What is the most common way of clarifying wine?

A

Filtration

42
Q

What are the two types of filtration?

A
  1. depth filtration

2. surface filtration

43
Q

What is depth filtration?

A
  • traps particles in the depth of the material that forms the filter
  • can cope with fluid with many particles in it (e.g. wine that has just been pressed or lees)
  • small particles are trapped within the many irregular channels through the filter
44
Q

Why is depth filtration not always reliable?

A
  • if too much pressure is applied or if the filter is used for too long, some particles will make their way through the filter
  • not an absolute filter
45
Q

What is the most common form of depth filtration?

A

Diatomaceous earth

46
Q

What is diatomaceous earth?

A
  • form of depth filtration
  • once processed, is pure silica and inert
  • aka ‘DE’, ‘Kieselguhr’
47
Q

What type of filter uses diatomaceous earth to filter wines in an oxidative way?

A
  • Rotary vacuum filters use this method to filter very thick and cloudy wine (e.g. wine mixed with lees)
  • oxidative process (drum is exposed to air)
48
Q

What type of filter uses diatomaceous earth to filter wines in a non-oxidative way?

A
  • Enclosed DE filters do the same job

- Can be flushed with an inert gas (e.g. nitrogen) to avoid oxidation

49
Q

How is DE flexible?

A

DE comes in a range of particle sizes and thus can remove large or very small (e.g. yeast) particles

50
Q

What happens with used DE?

A
  • must be disposed of responsibly

- adds an additional cost

51
Q

What are sheet filters? Name 2 synonyms for sheet filters.

A
  • aka ‘plate and frame’ or ‘pad’ filters
  • wine is passed through a sheet of the filtering material
  • the more sheets in the filter, the quicker the wine can be filtered because any portion of wine only passes through one sheet
52
Q

At bottling, how can remaining yeasts be removed?

A

Filtering with very fine graded sheets

53
Q

What are the costs associated with sheet filter systems?

A
  • require investment initially (the frame must be very robust to withstand the pressures involved)
  • cost of filter sheets is low
  • trained personnel must operate them to work properly
54
Q

What are the 2 types of depth filtration?

A
  1. diatomaceous earth

2. sheet filters

55
Q

What are the 2 types of surface filtration?

A
  1. membrane filters

2. cross-flow filters

56
Q

What is a surface filter?

A
  • stops particles that are bigger than the pore size of the filter from going through
  • absolute filters
57
Q

Which filters are absolute: depth or surface filters?

A

Surface filters

58
Q

What is a membrane filter? What’s another name for membrane filter?

A
  • aka ‘cartridge filter’

- catch particles that will not go through the pore size of the filter

59
Q

What is slower: membrane filters or depth filters? Why?

A
  • membrane filters

- the pores are smaller

60
Q

What must happen before a membrane filter is used? Why?

A
  • wine must be pre-filtered first (e.g. by depth filtration)

- otherwise, membrane filters can easily get blocked

61
Q

When are membrane filters typically used?

A
  • as a final precaution immediately before the wine is bottled to ensure that the wine is completely clear and microbiologically stable
62
Q

What does the term ‘sterile filtering’ refer to?

A

When membrane filters are used as a final precaution immediately before the wine is bottled to ensure that the wine is completely clear and microbiologically stable

  • not entirely accurate
  • the point is that yeasts and bacteria have been removed and therefore the wine is microbiologically stable
63
Q

What are the costs associated with a membrane filter?

A
  • initial investment is small

- cartridges are expensive

64
Q

What is a cross-flow filter? What is another name for cross-flow filter?

A
  • aka ‘tangential filter’
  • allow wine to pass through the filter while uniquely cleaning the surface of the filter as it works
  • solid particles cannot pass through the filter
  • can filter wine with a high load of particles or lees very quickly
65
Q

What are the costs associated with a cross-flow filter?

A
  • the machines are expensive, making them more suitable for large and or well-funded wineries
  • no replacement sheets, cartridges or earth to buy or dispose of
66
Q

What are the downsides of filtering? Why is it a controversial winemaking technique?

A
  • Some believe that it can negatively affect a wine’s character, especially stripping it of texture
  • Others believe that any immediate loss of texture is compensated in two ways:
    1. wine will recover from the shock of filtration after some months
    2. much less chance of wines developing faults as bacteria and yeasts have been removed
  • the fruit and the terroir may express themselves better in a correctly fined and filtered wine

WsetDip D1 (87 decks)

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