White: Clarification

Question 1

What is the aim of must clarification prior to fermentation?

Answer 1

• to reduce the amount of suspended solids, including particles of seeds, skins, and stems

Question 2

What is the desirable amount of suspended solids in a must that is clarified for fermentation?

Answer 2

0.5-2%

Question 3

How can very low levels of suspended solids be achieved?

Answer 3

• pectolytic enzymes
• centrifugation

Question 4

Why do some winemakers aim for slightly higher levels (1-2%) of suspended solids?

Answer 4

• adds texture to the wine, and a subtle astringency
• increase the range of aromas and complexity

Question 5

What are the advantages of very low levels of suspended solids?

Answer 5

• it can be better for achieving fruity aromas in the wine

Question 6

What fault can become a problem in fermentations in high levels of solids?

Answer 6

• generation of sulphur compounds, which in high levels, will give the wines a rotten egg aroma

Question 7

What types of wines might use musts with higher levels of solids?

Answer 7

• premium wines produced in smaller volumes
• constant monitoring is required

Question 8

What is the risk to fermentation of musts with low levels of solids?

Answer 8

• a lack of nutrients (which are released from the solid material) might lead to stuck fermentation

Question 9

How can a stuck fermentation be treated?

Answer 9

• yeast nutrients such as DAP can be added

Question 10

What four techniques are listed in the text for clarification of must?

Answer 10

• sedimentation
• flotation
• centrifugation
• clarifying agents

Question 11

Define sedimentation in relation to must clarification.

Answer 11

• suspended solids are left to fall over time with gravity
• commonly performed while chilling the wine to 4C to reduce oxidation and prevent spoilage and fermentation

Question 12

How long does sedimentation typically take?

Answer 12

12-24 hours

Question 13

What happens after sedimentation?

Answer 13

• the clear juice is racked off the sediment
• the sediment may be filtered to extract extra juice

Question 14

What are the advantages of sedimentation?

Answer 14

• cheapest method
• requires no additives or specialized equipment

Question 15

What are the negatives associated with sedimentation?

Answer 15

• takes a long time, especially for large volumes
• cost associated with the energy used for chilling
• a batch process, which is costly in terms of labor and time

Question 16

Define flotation in regards to clarifying must.

Answer 16

• the bubbling of gas through the must, which brings solid particles to the surface of the wine, which can then be skimmed off the top

Question 17

What are the advantages of using flotation to clarify must?

Answer 17

• very fast
• very effective
• can be used as a batch process or continuous process
• saving on energy costs in comparison to sedimentation

Question 18

What are the disadvantages of flotation for clarifying must?

Answer 18

• the technique requires extra equipment, gases, and fining agents, which are costly
• it is a little more expensive than sedimentation

Question 19

Which gases can be used for flotation, and what are the effects?

Answer 19

• nitrogen: inert, and so little effect on the wine
• oxygen: can be used as a hyper-oxidation step

Question 20

Define centrifugation for clarifying the must.

Answer 20

• the removal of solids from the must using cetrifugal force, which is applied to the liquid using equipment called a centrifuge

Question 21

What are the advantages of a centrifuge?

Answer 21

• can clarify the must quickly and effectively
• they are used continuously

Question 22

What are the disadvantages of centrifugation?

Answer 22

• expensive equipment
• process can introduce oxygen to the must, unless expensive inert gas is used

Question 23

What are clarifying agents?

Answer 23

• a number of different compounds that can be used to aid the clarification process, and speed up sedimentation