White: Clarification Flashcards
What is the aim of must clarification prior to fermentation?
- to reduce the amount of suspended solids, including particles of seeds, skins, and stems
What is the desirable amount of suspended solids in a must that is clarified for fermentation?
0.5-2%
How can very low levels of suspended solids be achieved?
- pectolytic enzymes
- centrifugation
Why do some winemakers aim for slightly higher levels (1-2%) of suspended solids?
- adds texture to the wine, and a subtle astringency
- increase the range of aromas and complexity
What are the advantages of very low levels of suspended solids?
- it can be better for achieving fruity aromas in the wine
What fault can become a problem in fermentations in high levels of solids?
- generation of sulphur compounds, which in high levels, will give the wines a rotten egg aroma
What types of wines might use musts with higher levels of solids?
- premium wines produced in smaller volumes
- constant monitoring is required
What is the risk to fermentation of musts with low levels of solids?
- a lack of nutrients (which are released from the solid material) might lead to stuck fermentation
How can a stuck fermentation be treated?
- yeast nutrients such as DAP can be added
What four techniques are listed in the text for clarification of must?
- sedimentation
- flotation
- centrifugation
- clarifying agents
Define sedimentation in relation to must clarification.
- 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
How long does sedimentation typically take?
12-24 hours
What happens after sedimentation?
- the clear juice is racked off the sediment
- the sediment may be filtered to extract extra juice
What are the advantages of sedimentation?
- cheapest method
- requires no additives or specialized equipment
What are the negatives associated with sedimentation?
- 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
Define flotation in regards to clarifying must.
- 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
What are the advantages of using flotation to clarify must?
- very fast
- very effective
- can be used as a batch process or continuous process
- saving on energy costs in comparison to sedimentation
What are the disadvantages of flotation for clarifying must?
- the technique requires extra equipment, gases, and fining agents, which are costly
- it is a little more expensive than sedimentation
Which gases can be used for flotation, and what are the effects?
- nitrogen: inert, and so little effect on the wine
- oxygen: can be used as a hyper-oxidation step
Define centrifugation for clarifying the must.
- the removal of solids from the must using cetrifugal force, which is applied to the liquid using equipment called a centrifuge
What are the advantages of a centrifuge?
- can clarify the must quickly and effectively
- they are used continuously
What are the disadvantages of centrifugation?
- expensive equipment
- process can introduce oxygen to the must, unless expensive inert gas is used
What are clarifying agents?
- a number of different compounds that can be used to aid the clarification process, and speed up sedimentation