Chapter 7 - Common Elements in Winemaking Flashcards
Name the parts of the grape
Skin - high concentration of flavour compounds. Also contains tannins and colour compounds
Seeds and stems - contain tannins and bitter oils
Bloom - the waxy surface that covers the skin
Pulp - contains water, sugar and acids (mostly tartaric, a bit malic)
Tannins
What is the chemical process of oxygen reacting with wine reffered to as?
Oxidation
What flavours does oxidation take away from wine?
Primary fruit characteristics
What anti-oxidant is often used?
Sulfur Dioxide
What are some techniques to counter the effects of oxygen in winemaking?
- harvest at night when it is cooler
- keept the grapes chilled as long as possible during and after harvest
- keep the grapes and juice away from oxigen with airtight equipment
Why do lower temperatures help against oxidation?
Chemical processes go slower in lowe temperatures
What gasses are used to keep machinery airtight?
Nitrogen and Carbon Dioxide
What is winemaking with the least amount of oxigen referred to as?
Anaerobic winemaking
Can you mature wines that have been made anaerobicly in oak vessels
No, wines made in that way don’t benefit from any contact with oxigen during maturation
What airtight maturing vessels are there?
- stainless steel
- cement lined with epoxy
What can contact with very small amounts of oxygen during ripening do to wines?
- soften tannins in red wines
- give complexity to flavours: fruit will fade into teriary characters like earth or leather
- colour changes. Red becomes paler and can turn brown, white becomes deeper in colour and becomes a bit orange
Why are wines rarely kept more than 2 years in barriques?
Because of its small size (225 liters), the relative surface touching the oak (and thus oxigen) is very big compared to larger vessels
Why would barrels not fully be topped up? Examples
For fortified wines that have a deliberate oxidative style this is a technique used to create nutty, caramel and toffee flavours.
Olorosso, Tawny Port and Rutherglen Muscat
What is the risk of too much oxigen exposure during ageing?
Too much loss of fresh fruit flavours and stale smell
What is SO2 and what is it used as?
Sulfur Dioxide
- antioxidant
- antiseptic
Why is the use of SO2 restricted?
It can be toxic (though the concentration in wine is lower than dried fruit)
It can cause allergic reactions
What is a ‘bound’?
SO2 when it reacts with O2. It loses its protective ability and becomes a ‘bound’
What does SO2 do, other than protect against oxigen?
It kills off bacteria and yeasts (except for the one that does the alcoholic fermentation)
What other use, aside from micro oxidation, do oak vessels have?
Adding tannin (and thus structure) Adding flavour (like vanilla, toast, smoke and cloves)
What are 4 important factors in choosing the type of oak vessel
- species and origin. Oak from different species or origins can have different characteristics (flavour etc)
- size. Small vessels have more impact than big vessels (due to relative surface contact
- age. The amount of flavour a barrel gives to the wine deminishes with every useage
- production. For instance toasting, which gives distinct flavours to the wine
What is a piece, and what is a barrique?
Piece is an oak barrel of 228 liters
Barrique is 225 liters
What are the 2 main origins of oak vessels?
American Oak and European (French, Hungarian, Russian)
After how many times do oak vessels lose most of their flavour?
After 4 uses
What are other ways than oak barrels to get the aroma’s and tannins in the wine?
Chips or staves
What are 2 ways temperature be controlled in stainless steel vessels?
Sleeves on the outside
Coils on the inside
Why do some wine makers prefer concrete vessels?
The thick shells help to regulate temperature
Why should damaging the seeds be avoided during crushing?
It releases bitter and astringent oils an tannin
When is pressing done?
In white wines before fermentation, in red wines usually after fermentation
What is free run juice?
The juice that comes from crushing, when the skin is lightly broke
What does a traditional (basket) press look like?
It is vertical, with a plate that is raised or lowered by using a screw or lever. Still used in Champagne
How does a pneumatic press work?
With an inflateable tube within a horizontal cylinder, sometimes built within a closed stainless steel tank to minimize contact with oxygen
Name 3 components that can be adjusted in a wine (or must)
Sugar, alcohol and acid
What is the must weight?
The level of sugar in the must
What is RCGM?
Rectified Concentrated Grape Must, a sypury liquid, used to ‘enrich’ the grape must to get higher levels of alcohol
When is enrichment done?
In cooler climates, adding RCGM, helps raise alcohol levels when grapes don’t get enough sugar on their own
What is a danger of enrichment?
The wine may not have enough flavour to balance the higher levels of alcohol
What is chaptalisation?
Enrichment with sources other than RCGM, for instance sugar beets
What is another way, other than enrichment, to get more alcohol in the wine and what is the risk here?
Remove water from the juice. It concentrates the sugars, but also everything else (even flaws)
Why and where is acidification done?
Usually only in warmer regions, where acid levels can drop too far during ripening
How is acidification done?
By adding tartaric acid in powder form
How, why and where is deacicidication done
Usually in colder regions, where acid levels have not dropped enough during ripening, by using alkali
What is acoholic fermentation?
The conversion of sugar into alcohol and CO2
What are the by-products (4) of alcoholic fermentation?
CO2
Alcohol
Heat
Flavour compounds
What is the yeast responsible for most fermentation in wine?
Saccharomyces Cerevisae
Why is Saccharomyces Cerevisae a good yeast for alcoholic fermentation?
Its is very resistant to alcohol and SO2
What is the lowest temperature required for alcoholic fermentation?
5 *C
When does alcoholic fermentation stop?
When sugar runs out
When nutrients other than sugar run out
When the temperature of the juices reaches over 35 *C
When the alchol level becomes too high (this requires a lot of sugar to begin with)
How can the fermentation be stopped before all the sugar is consumed?
By adding SO2 or grape spirit to kill the yeast
Or by removing the yeast using filtration after chilling the wine below 5 *C
Why are ambient (indiginous) yeasts not suitable for high volume wine production?
Winemakers cannot what yeasts exactly are present, which may result in different flavours between batches and longer fermentation times
In what way does fermentation temperature influence the final wine?
Fermenting at low temperatures avoids the loss of volatile aroma’s that have a floral character and encourages the development of fruity flavours.
Higher temperatures promote extraction of colour and tannin
What is MLF
Malolactic fermentation. Which takes place after alcoholic fermentation. Turning malic acids into lactic acids (which are softer to the palate)
What is the effect of MLF?
It creates softer acids, reduces acidity, and creates buttery flavours.
A byproduct is also CO2
How is MLF encouraged?
Raising the temperature during fermentation
What are lees?
Dead yeast cells and grape fragments
What 2 types lees are there?
Gross and fine
Why would a wine maker keep the wine in contact with the lees?
It adds texture and flavour
What are the components of a typical still wine?
Ethanol Tannins and colour Water Acids Sugars Aroma’s and flavour compound
Why would a winemaker store its wine for the shortest amount of time possible in an inert vessel (wine quality, not economic)
To keep as many primary fruit aroma’s as possible
What does a wine need in order to survive medium to long term ageing?
Tannins
Acidity
and/or alcohol
And flavours that can develop in an interesting way
When is blending most often done?
After fermentation or during maturation
Why is blending done?
Improve balance, attain consistency and/or achieve a certain style
Why is blending for consistancy so inportant?
Wines ripened in different vessels can show slight differences for a number of reasons. To get one consistant product in all of the bottles, the wines are often blended.
Differences can arise due to variations in the oak, vineyard site or harvesting time.
What can winemakers do to create as many blending options as possible? (6)
Seperate press fractions
Fermenting or maturing in different types of vessels
Only allowing a portion of the wine to go through MLF
Using different varieties
Vinyard plots
Vintages
What are the 3 main techniques for clarification?
Sedimentation
Fining
Filtration
Why would a winemaker NOT clarify its wine?
If they believe it can harm the character of the wine
What is sedimentation and racking?
When winemakers let gravity pull suspended particles (such as gross lees) to the bottom of the liquid and then pump the clear liquid off of the sediment. This is called racking, and can be done at multiple moments and stages (all after fermentation).
What is fining?
The process of speeding up the clumping together of certain constituents, in order to filter them out as a part of clarifying the wine.
What are the 2 types of filtration?
Depth filtration - the wine is passed through thick layers of material
Surface filtration - using very fine sieves. Sometimes so fine that it can be called sterile filtration
When is a wine considered stable?
If it changes in a slow, predictable manner over a specified time frame
Apart from clarification, what are 3 important areas that require stabilisation?
Tartrate stability, microbiological stability and oxygen stability.
What are tartrates?
It is cristalized tartaric acid. They are harmless and flavourless.
Cold temperatures speed up the process of cristalization. (This fact can be used by winemakers to force tartrate stability)
What aids microbiological stability?
Alcohol, lack of nutrients and acidity.
Name 2 styles that are naturally resistant to microbiological spoilage
Fortifies wines - because of the high alcohol levels
Dry, high acid, MLF wines - alcohol, lack of nutrients and acidity.
What are 2 ways to sterilize a wine?
SO2 and sterile filtering
What happens to wine if a wine is exposed to oxygen (during or) after bottleing?
Losing fresh fruit aroma’s and turning brown
Why is wine mostly packaged glass bottles?
Cheap, sturdy and portable. And completely airtight (the glass itself)
What is the downside to using glass bottles?
Heavy and rigid. Which adds transport costs and takes op much space.
Why is plastic not the beet option for storing wine?
Tiny amounts of oxigen pass through, which puts the wine at risk within about 18 months. So it is good for early drinking wines, but nothing that needs ageing.
