C7 - Common Elements In Winemaking And Maturation Flashcards
What is the next stage in winemaking after harvest?
The grapes are processed and prepared for alcoholic fermentation
On a basic level, what is alcoholic fermentation?
Yeast converts sugars in the grape to alcohol
What is the next basic stage of winemaking after alcoholic fermentation?
The wine needs to be stored prior to packaging and sale
Broadly speaking, what are natural wines?
Wines made with minimal intervention
Describe the seeds and stems of the grape
Both contain tannins
Seeds contain high levels of bitter oils
How are stems made available to the winemaker
By hand harvesting
Why is the grape skin important to the winemaker?
The skin and the area immediately underneath, contain high levels of flavour compounds (containing the grape’s signature character)
It contains tannins
It contains colour compounds
A large number of chemical compounds are classed as…
Tannin
Describe tannins at Véraison
How does this change?
They taste very bitter and astringent
As grapes ripen, bitterness and astringency fall
What is the Bloom of a grape?
The waxy surface that covers the skin of a grape
It contains yeast that can be used for fermentation
List the three major constituents of a grape’s pulp
Water
Sugar
Acid
What is the largest constituent of a grape’s pulp?
Water
What is the second largest constituent of a grape’s pulp?
Sugar
In order, what are the most abundant acids in a grape’s pulp?
Tartaric acid
Malic acid
What can oxygen react with during winemaking and maturation?
Grape juice
Many of the component parts of a wine
What is oxidation?
Oxygen reacting with any component part of a wine
What is the biggest threat to a winemaker wanting their wine to be dominated by primary fruit characteristics?
Oxidation
How is the risk of oxidation broadly avoided by a winemaker?
Use of antioxidants such as Sulfur Dioxide
Keeping oxygen contact to a minimum
Why might grapes be picked at night?
It is cooler and the effect of oxygen is reduced because chemical reactions occur more slowly at lower temperatures
How are grapes kept away from oxygen once they reach the winery? What is this process called?
By filling airtight winery equipment with carbon dioxide or nitrogen before they are used for grape processing or winemaking
Protective/anaerobic winemaking
What is the argument against anaerobic winemaking?
Some argue that the resultant wines may be bland or uninteresting and that a higher level of oxygen contact helps to develop complexity and character
…rarely if ever benefit from oxygen contact during maturation
Wines that have been protected from oxygen during winemaking
How are anaerobically made wines stored?
In inert airtight vessels which are kept completely full
The vats are made from stainless steel or cement lined with epoxy-resin
How are aerobically made wines usually stored?
In wooden vessels that are normally made of oak
Oak is…but it is not…
Watertight
Airtight
How does the mild oxygen permeability of oak help a wine?
It can help to soften tannins in red wines
Gives more flavour complexity
What happens to flavours in wine during deliberate oxidation/maturation?
Primary fruit flavours gradually fade
Tertiary characters start to develop, such as leather and earth
Other than flavour, how may a wine change as a result of oxidation?
Red wines become paler and gain a hint of brown
White wines become deeper in colour and gain a hint of orange
What two main factors influence the amount of deliberate oxidation a wine receives?
Size of vessel
Length of time stored in it
How does barrel size affect the amount of oxidation a wine receives? Why?
Smaller barrels have a greater oxidative effect
They present a proportionately larger surface area of wood to the wine
How large is a barrique?
225L
Wines are rarely kept in barriques for longer than…
Two years
How may the effect of barrel oxidation be further enhanced?
If the container is not completely full
Name three wines which are matured in barrels which are not completely full
Oloroso Sherry
Rutherglen Muscat
Tawny Port
What characters do wines which are deliberately aged take on?
Caramel, toffee and nuts
What may happen to a wine if it’s exposed to too much oxygen?
It can lose much of its fruit flavour and smell stale
What can happen to over-oxidised wine in extreme cases?
Bacteria can use the oxygen to turn the wine to vinegar
What are the main uses of Sulfur Dioxide in a winery?
Antioxidant effects
Antiseptic effects
Which element in winemaking can be toxic? How is this prevented?
Sulfur Dioxide
It is regulated by law
Which major element in winemaking can cause allergic reactions, even at low levels?
Sulfur Dioxide
Why might a quality-conscious winemaker want to keep SO2 levels as low as possible?
It can make wines seem harsh and lacking in fruit
When used as an antioxidant, why must SO2 levels be constantly monitored?
By protecting wine from oxidation, SO2 becomes ‘bound’ and can have no further protective use
Why is SO2 effective as an antioxidant?
It is toxic to the many strains of yeast and bacteria that can cause unwanted flavours in wine
Is SO2 toxic to the principal fermentative yeast involved in winemaking?
No, this strain is resistant to certain levels of SO2
The majority of wooden vessels used in winemaking are made of…
Oak
Other than oxygen, what can oak ageing give to a wine?
Tannins
Flavours
What does oak-tannin give to a wine?
Structure/textural complexity
What kind of flavours can oak give to a wine?
Toast
Vanilla
Smoke
Cloves
What is a particular challenge when using oak for maturation? Why?
Hygiene
It is particularly difficult to keep wooden vessels free of yeasts, bacteria and moulds
Why may a winemaker use different types of vessel during maturation?
As oak vessels differ widely in their characteristics
To enhance complexity in their wines
What are the four major factors to consider when choosing oak for maturation?
Species and origin of oak
Size
Production of oak barrels
Age
Describe why species of oak is an important factor in flavour characteristics
Flavour can change, even within a species of oak
…oak has broadly similar characteristics no matter which country it’s from
European
Where is some of the finest oak considered to be from?
Some forests in France
What is a 228L barrel known as?
Pièce
How large can wine maturation vessels get?
More than 2000L
What is one of the most important procedures when it comes to how a barrel affects the flavour of a wine?
Toasting
How are the barrel’s staves prepared so they can be bent into shape?
They are heated
What secondary effects does the heating of a barrel’s staves have?
It transforms the tannins and the flavour compounds in oak
What flavours are newly produced by a barrel once it is toasted?
Sweet spice
Toast
What does ‘level of toasting’ refer to in the making of a barrel?
The temperature and length of heat exposure
What affects the flavours a barrel can give to a wine?
The level of toasting
What happens each time a barrel is used?
The effect of toasting diminishes
Why might a winemaker not use new oak?
In order to make a wine with subtler oak flavours
How else may oak flavours and tannins be added to a wine, other than using barrels? What is the advantage of doing this?
By using oak staves or oak chips
It’s cheaper
How may the oxidative effects of barrel ageing be replicated?
By adding small, controlled quantities of oxygen to the wine vessel
What is an inert wine vessel?
It does not add flavour to the wine or allow oxidation
What are the majority of inert winery vessels made from?
Stainless steel or concrete
What can inert winery vessels be used for?
Fermentation
Temporary storage of wine after it is finished
What are most modern winery vessels made from?
Stainless steel
List the advantages of stainless steel as a winery vessel
Easy to keep clean
Can be made into any shape and size
Can incorporate temperature control mechanisms
What are the two main types of temperature control mechanisms?
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? What does this do?
Epoxy resin
It’s inert and provides a waterproof barrier
What was commonly used before stainless steel vessels?
Concrete vessels
What are the disadvantages of concrete vessels over stainless steel?
They can be less easy to clean and maintain
Why might some winemakers prefer concrete vessels?
The thick concrete shells help to regulate temperature during fermentation and maturation without the need for expensive equipment
Name a wine vessel which is not steel or concrete…
Glass bottles
When do grapes usually use their first dose of SO2?
When they arrive at the winery
Besides receiving SO2, what else may happen to wine grapes during reception?
They may be individually checked and sorted for unripe and rotten grapes
What is the next possible stage after grape reception?
Destemming and crushing
What does crushing do?
It breaks the skin of the grapes and liberates a quantity of juice
What is the liquid product of crushing called?
Free run juice
What is the danger when crushing grapes?
If the seeds are crushed, they will release bitter oils and tannin
What does pressing do?
It separates the liquid and solid constituents of the grape
Why are modern pressing techniques designed to be gentle?
As with crushing, to avoid crushing the seeds
What is the traditional design of grape presses?
They were all vertical
How does a vertical press work? What is a traditional vertical press called?
The pressure on the grapes comes from above, using a screw or lever
A basket press
Name a wine producing region which is still particularly known for its vertical presses
Champagne
Describe a pneumatic press
An inflatable rubber tube within a perforated, horizontal stainless steel cylinder
What does a pneumatic press allow that a vertical press does not?
It’s possible to apply pressure over a larger area in a controllable way
Why are some presses built within a closed tank?
So that the amount of oxygen in contact with the juice is kept to a minimum
What is it important to be aware of regarding the juice which is pressed?
Liquid released at the start of pressing is very different to liquid released at the end
What are fractions?
Different pressings of grape juice/wine
What may be done with different ‘fractions’?
They may treated individually and blended in different proportions to create a certain style
When may adjustments take place?
Before, during or after fermentation
How is grape juice commonly referred to?
Must
What is the term for the level of sugar in grape juice?
Must weight
How may sugar be increased in a wine? What is it called?
By adding Rectified Concentrated Grape Must
Enrichment
What is Rectified Concentrated Grape Must?
A colourless, odourless, syrupy liquid
At what stage may a must be enriched?
Before or during fermentation
Which wine adjustment is banned in many parts of the world?
Enrichment
What may happen to a wine if the process of enrichment is abused?
It may become hard and thin
Because there are insufficient flavours to balance the artificially elevated alcohol
What is chaptalisation?
Where sugar from sources other than grapes is added as a form of enrichment
Other than enrichment, how else may alcohol levels be raised in a must/wine?
By removing water from the must
What are the disadvantages of removing water to concentrate sugar/alcohol?
As well as sugar, it concentrates tannins, acids, flavour compounds and faults
It reduces volume too
Name an adjustment which is very difficult
Removing sugar
Can alcohol be removed from wine?
Yes, after fermentation is complete
How is acid usually increased in a wine?
By the addition of tartaric acid in powder form
Where is acidification permitted?
In Europe, only in warmer countries
In many hot countries around the world
How may a wine be de-acidified?
By the addition of an alkali
What are the inputs and outputs of fermentation?
Sugar and yeast
Alcohol and CO2
What are the ‘other’ by-products of fermentation?
Heat and flavour compounds
Which yeast species is responsible for the majority of wine fermentations? Why is this used?
Saccharomyces cerevisiae
Due to its tolerance of relatively high alcohol levels and SO2
What is the minimum temperature at which fermentation can begin?
5C
At what point does fermentation naturally stop?
When all the sugar has been consumed
What may stop fermentation before all sugar has been consumed?
Yeast run out of nutrients
Temperature reaches over 35C
Combination of high sugar and alcohol
What may happen to fermentation if sugar levels are very high?
Fermentation may not even start
Broadly speaking, how may a winemaker deliberately halt fermentation?
By killing yeast
By removing yeast
How may yeast be killed?
Adding SO2
Adding grape spirit
Describe how a winemaker may remove yeast?
By temporarily halting fermentation, by chilling the must to below 5C
By filtering the yeast out
What are the two important ways in which a winemaker may control fermentation?
Choice of yeast
Temperature management
What are the two yeast choices a winemaker has?
Whether to use the ambient yeast strains on the grape bloom, or adding cultured strains to the must
What is the advantage of using ambient yeast strains?
It can produce complex flavours in the final wine
What is the disadvantage of using ambient yeast strains?
The winemaker cannot control exactly which yeast strains are present
There may be some variation between batches of grapes
What are commercially available yeasts?
Strains of S. Cerevisiae that have been specifically selected because they consistently perform and produce attractive flavours
What is a potential argument against using cultured yeasts?
That it can limit the potential complexity of the wine
Why is temperature management important in the winery?
Because if fermenting wine becomes too hot, yeast are killed
By controlling temperature, the winemaker can influence the wine’s flavours
What is achieved by fermenting at lower temperatures?
It avoids the loss of most volatile aromas (which often have a floral character)
It can encourage the development of fruity aromas in white wines
What is achieved by fermenting at higher temperatures?
This is necessary for the extraction of colour and tannins from black grape skins
Why is temperature control during fermentation easier now than it was?
Many vats have their own heating/refrigeration systems
Other than automatically, how may excess heat be releases during fermentation?
By pumping over
Name a winemaking technique which has been pivotal in quality and consistency of modern winemaking
Precise temperature control
When does malolactic fermentation usually take place?
Once alcoholic fermentation has finished
What carries out MLF?
Lactic acid bacteria
What happens during MLF?
Lactic acid bacteria convert tart malic grape acid into softer lactic acid
What does MLF broadly do?
Softens and reduces acidity
Creates buttery flavours
Produces CO2
How may MLF be encouraged??
By raising the temperature of the wine and not adding SO2
How may MLF be avoided?
Through storage at cool temperatures
Use of SO2
By filtering out the bacteria
Why may wine appear cloudy after fermentation? What becomes of this effect?
Due to the presence of dead yeast cells and grape fragments
The offending particles are usually heavy enough to fall to the bottom of the vessel within a few hours
What is the sediment that falls to the bottom of the vessel after fermentation?
Gross lees
What is the result of gross lees are not removed?
Unpleasant aromas can develop in the wine
What are fine lees?
Smaller particles in the wine after fermentation (which settle more slowly)
How are fine lees removed?
They are removed gradually during the wine maturation process
Why may a winemaker not want to remove the fine lees during pre-bottle maturation?
To add extra flavours and a richer texture to the wine
Why may a wine be bottled after only a few months?
The winemaker may want to preserve as many primary fruit aromas as possible
Give an example of a premium wine which is only matured for a short time, in inert vessels before bottling
Premium Australian Riesling
What is the most important factor in determining how well a wine will survive medium to long-term ageing?
It needs to have flavours that will develop in an interesting way
What changes can occur during pre-bottling maturation?
The vessel can affect the wine’s flavours by adding oak flavours or allowing the wine to oxidise
Over time, wine components can react with each other, altering flavour or balance (and sometimes creating sediment in the vessel, which is periodically removed)
When does blending take place?
It can take place at any stage during winemaking
When does blending usually take place?
After fermentation or during maturation
What is blending used to achieve?
Improve balance
Attain consistency
Achieve a certain style
What may impede blending?
Local laws
Give an example of when blending may be used to improve balance
When making red wine, free run wine may be blended with press wine to increase tannins in the final product
Give an example of when blending may be used to achieve consistency
Wines matured in small barrels can develop in subtly different ways and may be blended together in a large vat to smooth out inconsistencies
Variations may arise due to differences in fruit (harvested at different times)
Inconsistencies may arise during winemaking
How may a winemaker go about achieving their ‘house style’
By creating as many blending options as possible during the winemaking process
List some variations of blends that a winemaker may create
Separating press fractions
Fermenting/maturing in different vessels
Allowing only a proportion to go through MLF
Using different grape varieties
Different vineyard plots
Different vintages
What are the three main techniques a winemaker may use to clarify a wine?
Sedimentation
Fining
Filtration
Why may a wine not go through all clarification treatments?
Because some winemakers believe that some of the treatments may harm the character of the wine
What is racking?
Once the gross lees have settled in a deposit, the wine is gently pumped into another vessel, leaving the sediment behind
How are fine lees dealt with after racking?
Racking may be repeated several times during maturation
For some wines,…is the only clarification that will take place
Sedimentation and Racking
What is the major disadvantage of natural sedimentation as a means of clarification?
It is very slow
How may sedimentation be accelerated? What is the disadvantage of this?
By putting wine in a centrifuge
The equipment is very expensive
What is fining?
It speeds up the process of deposits clumping together in a wine so that they can be removed
How is fining performed?
By adding a fining agent to the wine and removing the clumps that appear
Why may a winemaker not add a fining agent to a wine
Some winemakers believe it can adversely affect flavour and texture
What is filtration?
A process that physically removes particles from a wine as it is passed through a filter
When may filtration be performed?
After fermentation, during maturation and before bottling
What are the two methods of filtration?
Depth filtration
Surface filtration
Describe the filters in depth filtration
They are made from a thick layer of material
Describe depth filtration
As wine passes through the filter, the solid parts become trapped inside it
What can depth filtration achieve?
It can handle very cloudy wines and remove gross lees
Describe filters in surface filtration
They resemble very fine sieves
How does surface filtration work?
Solid particles are trapped on the surface of the filter as wine passes through
What are the disadvantages of surface filtration?
Filters are very expensive
Filters clog very easily
How is the expense of surface filtration minimised?
By only using it after depth filtration
What is sterile filtration?
Where the pores in a surface filter are small enough to remove yeast cells and bacteria
When may sterile filtration be performed?
Just before bottling
Why are some bottles unfiltered?
Some winemakers believe that filtration can negatively affect a wine’s character, especially its texture
When is a wine considered stable? Why does this vary?
If over a specific time, it changes in a slow, predictable manner
The rate and amount of change deemed acceptable will vary from wine to wine
Name a stabilisation process and explain why it is considered to ‘stabilise’
Fining
It aims to produce a predictable outcome after bottling
Other than fining, name three other important areas that require stabilisation
Tartrate stability
Microbiological stability
Oxygen stability
Why can tartaric acid crystals form in wine? What are they called?
Tartaric acid is less soluble in wine than in grape juice
Tartrates
What do Tartrates look like?
Clear crystals in white wine
Purple crystals in red wine (stained by colour compounds)
What is the big disadvantage of Tartrates?
They spoil the appearance of the wine
How is the formation of Tartrates accelerated?
In cool temperatures
How may a winemaker force tartrate formation?
By chilling the wine to below 0C
How are tartrate crystals removed?
Filtration
Why are yeast and bacteria undesirable in wines?
They can spoil a wine and make it undrinkable
Why is it important to keep equipment sterile from a microbiological perspective?
Undesirable microorganisms can thrive in grape and wine residues
Which wines may not be at risk from microorganisms?
Fortified wines
Their alcohol levels are toxic for all microorganisms
Name a non-fortified wine which is highly resistant to microbiological spoilage
A dry, high-acid wine that has undergone MLF
Which wines are most prone to microbiological spoilage?
Low acid, low alcohol wines, which have not undergone MLF and have a little residual sugar
How are more susceptible wines treated to prevent spoilage?
With SO2
Sterile filtration
How may oxidation risk be reduced in a wine?
Minimising oxygen contact
Keeping SO2 topped up
Name an extra measure a winemaker may take during packaging to minimise oxidation risk
The bottle may be flushed with CO2 or nitrogen before filling to eliminate oxygen
What are the advantages of glass bottles?
Portable Cheap Quite strong Oxygen impermeable Do not impart flavours to wine
What are the main disadvantages of glass bottles? Explain this
They are heavy and rigid
Weight adds to transport costs
Rigidity means it cannot be packed to make best use of the available space
How are the disadvantages of glass bottles being counteracted?
Some producers are using lighter bottles
Some bottle in or closer to the destination country
Apart from logistics, why is bottle rigidity a disadvantage?
It means that when half-full, the bottle will contain a space for air
What is the main disadvantage of plastic bottles for wine?
They are slightly oxygen permeable and wines may lose their freshness within a matter of months
What is the advantage of bag-in-box wines?
What is the disadvantage?
The bag collapses as wine is drunk, preventing air from entering
The plastic bag is still oxygen permeable
Within what time period must a bag-in-box wine be consumed?
18 months
What factors may dictate the type of closure which is used for a bottle?
Ease of use
Which closures a bottling line is designed to use
For bottles intended for maturation, it must allow the wine to mature positively
What does a slow release of oxygen allow in some wines?
The development of tertiary flavours
What does an airtight closure allow?
Retention of fresh fruit flavours
Why may a winemaker not be able to choose their bottle closure?
It may be overridden by the preference of the consumer market
What is the most widely used bottle closure?
Cork
What is the major benefit of cork as a wine closure?
It allows very small amounts of oxygen to enter the wine, thus allowing the development of sometimes desired tertiary flavours
What are the two problems with cork-closed wines?
The risk of cork-taint
Risk of oxidation
What causes cork taint?
Trichloroanisole (TCA)
What effect does TCA have on a wine?
Gives wine a mouldy, cardboard-like aroma
How are winemakers battling the risk of TCA?
By investing large sums in treatments designed to prevent its formation
Hat are synthetic corks made from?
A form of plastic
What is the disadvantage of synthetic corks as closures?
They are generally designed for wines intended for early consumption
Who has championed the use of screw caps?
Producers from Australia and New Zealand
What are the advantages of screw caps as closures?
They do not taint wine
They provide an impermeable seal from air
What have trials shown about screw caps?
They preserve fruit flavour in wine longer than cork
How has the disadvantage of screw caps as a closure been countered by some producers?
Some screw caps have been designed to have some oxygen permeability
Within what time are the majority of wines best consumed?
One year
What happens to wines not intended for ageing when kept in bottle for more than a year?
They lose their primary fruit flavours
Give examples of wine styles which can mature in bottle for several years and are no at their best immediately after bottling
Vintage Port
The finest German Rieslings
Bordeaux Crus Classés
