Common Elements In Winemaking And Maturation Flashcards
Bitter oils and tannins are found in which part of the grape?
The seeds
What is the waxy surface covering the grape skin called, and what does it contain?
- The bloom
- Yeast
What is the largest single component of a grape’s pulp?
Water
What are the two most abundant forms of acid found in the grape’s pulp?
1) Tartaric acid
2) Malic acid
What are the 3 sources of tannin within a grape?
- Skin
- Seeds
- Stem
What 3 components do grape skins contain?
- Flavour compounds
- Tannins
- Colour compounds
What are 2 ways to counter oxidation?
1) Use of antioxidants such as sulfur dioxide
2) Taking precautions to oxygen contact to a minimum
Why does picking grapes at night help counter oxidation?
It is cooler - chemical reactions occur more slowly at lower temperatures, so the effect of oxygen contact is reduced
What 2 names are used to call the process of making wine with as little oxygen exposure as possible?
1) Protective winemaking
2) Anaerobic winemaking
Will wines made in a protective style benefit from oxygen contact during maturation?
Rarely, if ever
How would you store and mature wines which had been made in a protective style?
In inert airtight tanks or vats which are kept completely full
What 2 materials are inert maturations vessels made from?
1) Stainless steel
2) Cement lined with epoxy resin
Where would aerobically-matured wines be stored?
Wooden vessels, usually made from oak
Why is oak an ideal storage and maturation material for many wines?
It is watertight but not airtight
What happens with oxidative ageing to the colours of:
1) Red wine
2) White wine
1) Become paler and gain a hint of brown
2) Become deeper and gain a hint of orange
Which has a greater oxidative effect, a small or large oak barrel?
Why?
A small barrel, because they present a proportionately larger surface area of wood to the wine
How long are wines usually kept in barrique for?
Rarely longer than 2 years, as their oxidative effect is relatively strong
How can the effect of oxygen be enhanced whilst using a wooden vessel?
By not filling the container completely
Name 3 wines which are deliberately oxidative in style
- Oloroso Sherry
- Tawny Port
- Rutherglen Muscat
What happens to wine when it gets too much exposure to oxygen?
It can lose much of its fresh fruit flavour and smell stale and vinegary
What two uses does sulfur dioxide have in the winery?
It acts as an antioxidant and an antiseptic
What is strictly controlled by law because it can be toxic?
Upper levels of SO2 in wine
Why is it preferable to keep SO2 levels as low as possible?
High levels can make the wine seem harsh and lacking in fruit
What does it mean when SO2 becomes ‘bound’?
It loses the ability to have any further protective effect against oxygen
Why must levels of SO2 be constantly monitored and replenished?
It becomes bound as it protects the grape juice and wine against oxygen, so needs topping up
Why is SO2 used to kill off the many strains of yeast and bacteria which are found in wines?
They can cause unwanted flavours in the wines
Why doesn’t SO2 kill off the principal yeast involved in fermentation?
The levels used are toxic to other species, but these commercial yeasts are tolerant to those levels
Of what are the vast majority of wooden vessels made?
Oak
What are the 2 advantages of using oak for maturation?
1) They allow a small amount of oxidation, developing tertiary aromas
2) The wine can extract tannin and flavours from the oak
What do oak tannins add to red and white wines?
3 points
1) Structure
2) Textural complexity
3) Aromas such as toast, vanilla, smoke and cloves
Why is hygiene an issue with oak vessels?
It is difficult to keep them completely free of yeasts, bacteria and moulds; tainted wood can ruin a wine.
What are the 4 factors to consider when choosing an oak vessel for maturation?
1) Species and origin of the oak
2) Size
3) Production method of the barrel
4) Age
From which 2 continents does the majority of the oak used in winery vessels originate?
Europe and North America
Which 3 European countries produce the most oak for barrels?
- France
- Hungary
- Russia
What size is a barrique?
225 litres
What size is a pièce?
228 litres
How large can the biggest oak vessels be?
In excess of 2000 litres
Why do smaller oak vessels have a much greater effect on the wine than larger ones?
Because in smaller vessels, much more of the wine is in contact with the surface area of the barrel
What does toasting a barrel do to the tannins and flavour compounds in the oak?
It will transform them, giving notes of sweet spice and toast
What does ‘toasting’ a barrel mean?
It is part of the production process - the staves are heated over a flame so that they can be bent into shape.
What is the ‘level’ of toasting in a barrel?
The temperature and length of heat exposure during toasting
What diminishes each time an oak barrel is used?
The effect of the toasting
After how many uses would a barrel be expected to impart very little flavour or tannin?
On its fourth use
Why might a producer choose not to use new oak barrels?
If the strong flavours of new oak were not desirable for a particular wine
What are 2 alternative methods for adding oak aromas and tannins to wine, other than barrel ageing?
- Adding small planks of oak (staves)
- Adding small oak chips
Both could be added during fermentation or maturation, and to inert vessels
Why might a producer use oak staves or chips?
It is much cheaper than using casks
How can the oxidative effects of barrel ageing be replicated in inert vessels?
By adding small, controlled quantities of oxygen
Why are some winery vessels referred to as ‘inert’?
They do not add flavour to the wine or allow oxidation
Which 2 materials are most inert vessels made from?
- Stainless steel
- Concrete
Are inert vessels ever used for maturation?
There would be no point, as they would not impart new flavours - they are often used to temporarily store finished wines prior to bottling.
What are 3 advantages of using stainless steel for vessels?
- Easy to keep clean
- Can be made in any shape and size
- Can incorporate temperature control mechanisms
What are the 2 types of temperature control mechanism used in stainless steel vessels?
- Sleeves on the outside of the vessels
- Internal coils through which cold or hot liquid can be circulated
What are concrete vessels usually lined with, and why?
Epoxy resin - it is inert and provides a waterproof barrier
Why have many concrete tanks been replaced by stainless steel?
They can be less easy to clean and maintain
Why do some winemakers prefer concrete over steel vessels?
The thick concrete shells help regulate temperature during fermentation without the need for expensive temperature control equipment
Other than concrete and steel, what is another type of inert vessel which can be used for storage and maturation in the winery?
Glass bottles
When do grapes usually receive their first dose of SO2?
As they arrive at the winery
Why might grapes be individually checked on a sorting table when they arrive at the winery?
To eliminate unripe or rotten grapes - for premium wines only
Name two optional processes right after grape reception.
1) Destemming
2) Crushing
Why might grapes arrive in the winery without stems?
If they have been machine harvested
Do most winemakers prefer to keep or remove the stems?
Most choose to remove them
How is destemming usually carried out once in the winery?
In a machine which can subsequently crush the grapes
What happens to grapes when they are crushed?
3 points
- The skin breaks
- A quantity of free run juice is liberated
- The seeds are not damaged
What happens if grape seeds are crushed?
They release bitter oils and tannin
What is ‘pressing’?
The separation of the liquid and solid constituents of the grape.
When does pressing typically occur for:
1) White wines
2) Red wines
1) Before fermentation
2) After fermentation
Should seeds be damaged or undamaged during pressing?
Undamaged - pressing should be gentle
What is a ‘basket press’ and how does it work?
The traditional style of vertical wine press - pressure is applied to the grapes from above using a plate which is raised & lowered with a screw or lever.
In which region do many wineries still widely use traditional basket presses?
Champagne
What are the two main types of wine press?
- Vertical basket press
- Pneumatic press
How do pneumatic presses work?
A rubber tube is inflated inside a perforated, horizontal stainless steel cylinder - the grapes are pressed between them and the juice runs off.
Why are pneumatic presses more effective than vertical presses?
They make it possible to apply pressure over a larger area, in a more controlled manner.
Why are some pneumatic presses built within a closed tank?
To minimise oxygen contact with the juice
What is the name for the different pressings into which grape juice may be separated during the pressing process?
Fractions
When can adjustments be made to one or more of the major components of the grape juice or wine?
Before, during or after fermentation
What is ‘must’?
Grape juice
What is the ‘must weight’?
The level of sugar in the grape juice
Why might a winemaker decide to carry out enrichment?
If there is insufficient natural sugar in the grapes to give the wine a satisfactory level of alcohol.
Would enrichment be needed for wines produced in hot or cool climates?
Cool climates, as the acidity in the grapes would be high and the sugar levels low at harvest
What is the process of enrichment?
Increasing sugar levels in the grape juice by adding RCGM either before or during fermentation.
How does enrichment increase the level of alcohol in a final wine?
It adds sugar, so there is more sugar available for the yeast to convert to alcohol.
- What does RCGM stand for?
- What is RCGM?
- Rectified Concentrated Grape Must
- A colourless, odourless syrupy liquid made from grape juice
When is RCGM added to wine in the enrichment process?
Before or during fermentation
Why is enrichment forbidden or strictly controlled in many parts of the world?
If the process is abused, it can produce inferior wine which tastes hard and thin because there are insufficient flavours to balance the artificially elevated alcohol.
What is chaptalisation?
Similar to enrichment, it is a process to increase sugar and thus alcohol levels in a wine before or during fermentation - but instead of RCGM, sugar from sources other than grapes is used (e.g. sugar beet)
If sugar beet were added to a fermenting wine to increase final alcohol levels, would this be enrichment or chaptalisation?
Chaptalisation - the sugar is from a source other than grapes.
Other than enrichment and chaptalisation, what is a 3rd method of increasing sugar levels during wine production?
Removing water from the juice to concentrate the sugars.
Why is removing water from the juice to concentrate sugars not a particularly effective method of increasing alcohol?
(2 points)
1) All other elements in the juice are also concentrated - including tannins, acids, flavour compounds and faults.
2) Volume of the juice is reduced so less wine can be made and sold.
If too much sugar is added to the juice, how can this be corrected?
It is very difficult to remove sugar from the juice, so modern machinery is used to remove alcohol from the wine once fermentation is complete.
What is the name of the process by which acid is added to grape juice?
Acidification
Why might acid need to be added to grape juice?
If, during ripening, grape acids fall too far.
Would chaptalisation/enrichment be needed for grapes grown in a cool or a hot climate?
Why?
- Cool climate
- The grapes may struggle to reach sufficient levels of sugar ripeness in cooler temperatures
Would acidification be needed for grapes grown in hot or cool climates?
Why?
- Hot climates
- The grapes may convert too much acid to sugars in hot temperatures, which would lead to a flabby and unbalanced wine
What is normally added to the wine during acidification?
Powdered tartaric acid
Generally speaking, where in Europe is acidification allowed?
Warmer regions only
Where is deacidification common?
In cooler climate regions where acid levels may not have fallen sufficiently in ripening grapes
What happens in the process of deacidification?
An alkali is added to the juice to neutralise excess acid.
