Pressing and Must adjustments Flashcards
Define Pomace:
The solid remains of the grapes left after pressing
When are grapes pressed:
White wine: Done before fermentation (the aim is to crush and press the berries to maximise the release of juice but without extracting tannins from skins and seeds and to avoid excessive amounts of solids)
Red wine: typically after fermentation has been completed (care must be taken not to extract excessive tannin and bitterness from skins and seeds that have been softened by being in the must for periods typically between five days and three weeks)
Type of presses:
- Pneumatic press
- Basket press
- Horizontal screw press
- Continuous press
Describe a Pneumatic press:
- most popular type of press
- also called “air bag press”
- made up of a cylindrical cage with a bladder that runs down the side or middle of it that inflates pressing the berries against grates.
- can be programmed to exert different amounts of pressure
- it can be flushed with inert gas before use to protect the juice or wine from oxidation
Describe a Basket press:
- more traditional form of press
- also called ‘vertical presses’ or ‘champagne presses’
- A ‘basket’ is filled with grapes and pressure is applied from above. The juice runs through gaps or holes in the side
- Not sealed vessels (cannot be flushed with inert gases to avoid oxygen exposure)
- generally hold a smaller press load (much more labour intensive = most suited to small wineries making premium wines)
Horizontal screw press
- similar to a basket press mounted horizontally above a rectangular draining tray.
- less gentle than many other types of press and therefore less popular.
Continuous press:
- allows grapes to be continually loaded into the press as it works by using a screw mechanism;
- quicker pressing of large volumes of grapes.
- less gentle than pneumatic and basket presses ( best suited to producing high volumes of inexpensive wines)
What is the general aim of must adjustment?
- to create a more balanced wine
(especially if there has been a compromise in achieving optimum ripeness of sugars, acids, tannins and flavours)
Types of must adjustments:
- Enrichment
- Reducing alcohol
- Acidification
- Deacidification
- Adding Tannins
Define and describe Enrichment
- usually winemakers in cooler climates
- before or during fermentation
- to increase the alcoholic content of the final wine
- by adding dry sugar (beet or cane sugar / Chaptalisation, after Jean- Antoine Chaptal), grape must, grape concentrate or rectified concentrated grape must (RCGM)
- also by processes of concentration (reverse osmosis, vacuum extraction, cryoextraction).
Define and describe Reducing Alcohol
- In warm or hot regions where sugar can accumulate in the grapes quickly
- to lower the potential alcohol of the wine
- by adding water to the grape must.
- also dilutes the grapes’ aromas/flavours and acids
Define and describe Acidification:
- In warm climates without any cooling influences, the malic acid in grapes tends to drop dramatically as the grapes ripen(wine could lack freshness)
- Also used to lower pH
- Usually by adding Tartaric acid
- Also by adding citric acid (not permitted in the EU), malic acid (less used as it could be turned into lactic acid by MALO) or lactic acid (less harsh)
- before, during or after fermentation (best before fermentation starts to benefit from the effects of a lower pH / also the acidity added at this stage integrates better within the profile of the wine as a whole)
- total acidity and pH can both be affected during the various winemaking processes, including malolactic conversion and tartrate stabilisation (Needs to be taken in account when deciding the amount of adjustment)
Define and describe Deacidification
- In cool climates where grapes may have to be picked before they are fully ripe (e.g. due to the threat of poor weather)
- Addition of Calcium carbonate (chalk) or Potassium carbonate
- lowers acidity by the formation and precipitation of tartrates
- A high-tech option: deacidification
by ion exchange (expensive machinery needed)
Define and describe Addition of Tannins
- Powdered tannins may be added to help to clarify musts
- to help to stabilise the colour of musts and improve mouthfeel (red wines)
- Either added to the must before fermentation or to the wine before maturation.
