Transportation and Grape reception Flashcards
What are the threats to quality when grapes are being transported from the vineyard to the winery?
Oxidation
Ambient yeasts
Acetic acid bacteria
What five measures can be taken to reduce the risks during transportation?
- Harvesting and transporting grapes at night (lower temperatures minimise threats)
- Addition of SO2 to the grapes at time of harvesting (To provide antioxidant and antimicrobial protection)
- Reduction of grapes’ temperature (putting them in cold storage to minimize risk of oxidation and microbial infection)
- Sanitising harvesting equipment and bins
(To reduce the chance of microbial infection) - Collecting the grapes in small crates
(To minimise crushing and reduce oxidation of the juice)
How is machine harvested fruit typically transported?
In large containers with some release of juice
Why are black grapes less vulnerable to oxidation?
They contain more phenolic compounds with anti-oxidative properties
What are the options for transporting hand-harvested grapes to the winery?
- Transporting in small crates
- Tipping into larger hoppers : this can cause crushing of grapes, oxidation, increased threat from spoilage organisms
What treats pose acetic acid bacteria and ambient yeast during transportation?
Ambient yeasts: They pose a threat to grape quality
Acetic acid bacteria: They can turn alcohol into acetic acid, causing vinegar-like flavours
What are the four main operations of processing when grapes arrive at the winery?
- Chilling
- Sorting
- Destemming
- Crushing
What options are there for moving grapes around the winery?
Large volumes of grapes - Conveyor belt or screw conveyor
Small volumes of grapes - Manually with pallet truck or forklift
Why might a winemaker choose to chill grapes? And how?
To decrease the rate of oxidation and the threat of spoilage organisms
- Put them into a refrigeration unit
- A heat exchanger for machine harvested or crushed grapes
- Add dry ice to the crates of grapes
What factors impact the level of grape sorting required in the winery?
- Ripeness of grapes
- Health of grapes
- The intended wine quality and price
- Whether there has been any sorting in the vineyard
- The physical state of the grapes (crushed, machine harvested)
Why does more grape sorting lead to more cost?
Labour costs
Time required
Reduced yield
What is MOG?
Material other than grapes: leaves, twigs, insects
Why may cool climate grapes require more sorting?
Higher disease pressure and unripe grapes
What are the options for sorting grapes for quality wines?
- Removal of unwanted grapes and bunches during picking
- Sorting by hand at the winery
- Optical sorting using a high tech digital imaging equipment. Only used for premium and super-premium wines
How do destemmers work?
A series of blades within a rotating drum removes grapes form the stems.
Which types of wine might utilise destemming upon reception of the grapes?
Most white wines and many red wines.
Why might winemakers destem the grapes?
Stems contain tannins which can be extracted if the stems are left in contact with the wine. Tannins are undesirable in white wines and extra tannins may be undesirable in red wines.
Why may winemakers choose not to destem the grapes?
- Red wine fermentations using whole bunches
- Carbonic maceration
- Whole bunch pressing for some white wines.
Define grape crushing.
Application of pressure to the grapes to break the skins and release the juice.
What is must?
The mixture of grape juice, pulp, skins and seeds resulting from crushing. For white wines this can refer to the grape juice being fermented.
