Chapters 7-9

Question 1

What role do the seeds and stems play in winemaking?

Answer 1

They both contain tannins. Seeds can also contain bitter oils. The stems are only available if grapes are hand harvested.

Question 2

What role do the skins play in winemaking?

Answer 2

The skin and the area immediately beneath it contain high concentration of flavour compounds. The skin also contains tannin and colour compounds.

Question 3

What role does the pulp play in winemaking?

Answer 3

Water is largest component of the pulp, and therefore in the wine. The sugar gets fermented into alcohol. Acids are present (e.g. tartaric, malic) which will also be present in the wine.

Question 4

What role does the bloom play in winemaking?

Answer 4

The bloom is the waxy surface that covers the skins of the grapes and contains yeasts that can be used to ferment the wine.

Question 5

What role does oxygen play in winemaking and maturation?

Answer 5

Oxygen can react with grape juice or wine. It can have positive and negative effects.
Oxygen in winemaking - many winemakers seek to reduce contact with oxygen in winemaking as it can affect fruity flavours. Using antioxidants such as sulfur dioxide, picking at night, using air tight vessels are all ways to reduce the effect of oxygen. This can be referred to as protective or anaerobic winemaking.
Oxygen in maturation - wines can be matured in airtight vessels. Wines that are matured aerobically are stored in wood. Oak is watertight but not airtight. Small amounts of oxygen can help soften the tannins and give more complexity, primary fruit flavours will fade and tertiary characteristics will develop.
Wine styles - some wines have pronounced oxidative character e.g. Oloroso Sherry, Tawny Port. For most wines too much oxygen exposure can be damaging.

Question 6

What role does sulfur dioxide play in winemaking?

Answer 6

Antioxidant and antiseptic.
Levels adjusted during winemaking.
Upper levels are strictly controlled by law.
Some naturally produced during fermentation, most winemakers keep additions as low as possible.
Some refuse to use any.

Question 7

How do oak vessels affect wine?

Answer 7

Used in fermentation and maturation.
Allows small level of oxidation while the wine is maturing to allow tertiary aromas to develop.
Wine extracts tannin from the oak.
Can also give aromas and flavours to the wine such as vanilla and cloves.
Hygiene important, tainted wood can ruin wines.

Question 8

What are the options related to oak a winemaker can consider?

Answer 8

Species and origin - French best
Size - small vessels (e.g. 225 L) have greater effect.
Production - level of toasting - transforms tannins and flavours giving notes of sweet spice and toast.
Age - effect of toasting reduces each time a barrel is used.

Question 9

What are oak alternatives?

Answer 9

Oak staves or oak chips which are inserted into an inert can add aroma and tannin at lower cost.
Oxidative effects of barrel ageing can be replicated by adding small quantities of oxygen to the wine vessel.

Question 10

What are the options for inert winery vessels?

Answer 10

These are vessels that do not add flavour to wines or allow oxidation. They are widely used for fermentation and are often used to store wines before bottling.
Stainless steel - most modern winery vessels are made from this. They are easy to clean, can be made in any shape and size, and can incorporate temperature control mechanisms.
Concrete vessels - usually lined with epoxy resin which is inert and waterproof. They were commonly used before stainless steel but many have now been replaced. They are less easy to clean, however are preferred by some winemakers due to the natural temperature regulation.
Glass bottles - used for storage and maturation.

Question 11

What happens during grape reception?

Answer 11

First dose of sulfur dioxide.
Grapes for premium wines individually checked to eliminate unripe or rotten grapes.

Question 12

What happens during destemming and crushing?

Answer 12

These are both optional. Machine harvested grapes arrive without stems. If they have been hand harvested most winemakers choose to remove them. This is often done in a machine that can also crush the grapes. Crushing breaks the skins and the juice that is collected is known as the free run juice. Damage to seeds should be avoided.

Question 13

What happens during pressing?

Answer 13

Pressing separates the solid and liquid parts of the grapes. For white wines this is before fermentation, for red wines this is after fermentation. Seeds should remain undamaged. Traditionally this was done with vertical basket presses, but many are now automated pneumatic presses which can limit oxygen contact to a minimum. The liquid released at the beginning is different to the liquid released towards the end so the winemaker may divide it into different press fractions.

Question 14

What are the adjustments that can be made to grape juice/wine?

Answer 14

Enrichment - adding sugar (RCGM) to juice to raise the level of alcohol in the wine. Used in cooler climates but is strictly controlled. Where sugar from other sources is used it is known as chaptalisation.
Remove water - concentrates sugars and makes a wine higher in alcohol, acid, tannin (and any faults present). Reduces the volume of liquid so less wine is made.
Acidification - increasing the level of acid by the addition of tartaric acid in powdered form. Used in warmer regions.
Deacidification - reducing the level of acid by the addition of an alkali. Used in cool climates.

Question 15

How does fermentation work?

Answer 15

Yeast convert sugar into alcohol, carbon dioxide and flavour compounds. Saccharomyces cerevisiae is the yeast species responsible as it is relatively tolerant of alcohol and sulfur dioxide. Fermentation may stop when all the sugar is consumed, or when the yeast run out of nutrients, or if the temperature reaches above 35°C. When sugar levels are very high yeast can struggle. Fermentation may be stopped early by killing the yeast (through addition of sulfur dioxide or alcohol) or by removing the yeast (by chilling the wine to below 5°C and filtering them out).

Question 16

How does yeast affect fermentation?

Answer 16

The winemaker can use ambient yeast found on the bloom or in the winery which can produce complex flavours but may have variation between batches. Commercially available cultured yeast have been specifically selected for consistency but may limit the potential complexity.

Question 17

How does temperature affect fermentation?

Answer 17

If the wine becomes too hot the yeast are killed. Fermentation at a low temperature avoids the loss of more volatile aromas which can have a floral character and can encourage fruity flavours in white wines. Higher temperatures are necessary for the extraction of colour and tannin from black grape skins.

Question 18

How does malolactic fermentation affect a wine?

Answer 18

MLF takes place once the alcoholic fermentation has finished. Lactic acid bacteria convert the tart malic acid into softer lactic acid. It softens and reduces acidity and creates buttery flavours. It can be encouraged by raising the temperature of the wine and not adding sulfur dioxide, or avoided through storage at cool temperature, use of sulfur dioxide and filtering out bacteria.

Question 19

How do lees affect the wine?

Answer 19

After fermentation wine will appear cloudy due to dead yeast cells and grape fragments. After a few hours these will fall to the bottom of the vessel and form the gross lees, which can cause unpleasant aromas if not removed. Smaller particles settle more slowly and may be left in with the wine to add more flavour and texture. These are known as fine lees.

Question 20

How does pre-bottling maturation affect a wine?

Answer 20

Not every wine benefits from maturation before bottling. For wines intended for medium or long term ageing they need sufficient levels of tannin, acidity or alcohol and they must have flavours that will develop in an interesting way. The vessel will affect the wine either by adding oak flavour or allowing oxidation to take place. Components of the wine can react with each other causing further changes and leading a sediment to form that will be periodically removed.

Question 21

How does blending affect a wine?

Answer 21

Blending plays a vital role and can take place at any stage of the winemaking process. Winemakers will need to be aware of any local regulations. Reasons include:
Balance - A winemaker can adjust the balance of the wine to enhance the quality. E.g. by blending free run wine and press wine.
Consistency - To make sure there is not significant variation among bottles. E.g. by blending different barrels or vats together
Style - winemakers will have a house style they aim for despite variations in weather over vintages. In some cases winemakers may have many options for blending to achieve this style. E.g. blending different press fractions, fermentation or maturation in different vessels, the proportion of MLF, different grape varieties, different vineyards.

Question 22

How does sedimentation affect a wine?

Answer 22

This slowly separates any particles from the wine by gravity. As particles settle the wine is racked into a different vessel. This can happen several times to achieve clarity. The process can be accelerated by using a centrifuge but this equipment is expensive.

Question 23

How does fining affect a wine?

Answer 23

Fining removes small particles that may become visible in a bottle over time. This is done by adding a fining agent that clumps particles together which can then be removed by filtering. It is practiced by many winemakers although some choose not to as they believe it can adversely affect texture.

Question 24

How does filtration affect a wine?

Answer 24

This removes particles from a wine using a filter. This can be used to remove the gross and fine lees. Wines are usually filtered before bottling to make sure they are clear. There are two types of filtration:
Depth filtration - these are made from a thick layer of material. As the wine passes through the filter the solids become trapped inside. They are able to handle very cloudy wines and can remove gross lees.
Surface filtration - uses very fine filters that can remove yeast and bacteria. They are expensive and clog up easily and are normally used after depth filters.

Question 25

How does tartrate stabilisation affect a wine?

Answer 25

Tartaric acid can form crystals in wines known as tartrates when the wine is exposed to cool temperatures. Winemakers can force this to happen by chilling the wine to 0°C and then removing the crystals that form by filtration. Some winemakers choose not to do this.

Question 26

What is microbiological stability?

Answer 26

Many different forms of yeast and bacteria can spoil a wine. Some wines are more stable and at less risk, such as fortified wines, dry or high acid wines, or wines that have undergone MLF. Wines that are less stable are those that have not undergone MLF, or with low alcohol, low acidity, and a little residual sugar. These wines will require careful handling, an appropriate amount of sulfur dioxide and sterile filtering.

Question 27

What is oxygen stability?

Answer 27

If excessive oxygen comes into contact with a wine it can lose fresh fruit aromas. The risk can be minimised by avoiding exposure to oxygen, using sulfur dioxide and prodcuers can flush bottles with carbon dioxide or nitrogen before filling.

Question 28

What are the option related to packaging wine?

Answer 28

Glass bottles - portable, cheap, strong, they do not allow air in. However they are heavy and rigid which will add to transport costs. Producers can now use lighter bottles or transport their wines in bulk and then bottle in the country of sale. Once opened they let air in and then the wine will oxidise. Plastic bottles - lighter than glass, but the plastics used allow small amounts of air in. Bag-in-box - used for large volumes of wine. The bag collapses when wine is take out preventing air from getting in. Although a small amount can get in through the wall of the bag so wines should be drunk within 18 months.

Question 29

What are the options related to closures for bottles?

Answer 29

Cork - the most widely used. The closure of choice for wines intended for bottle maturation as it allows a small amount of oxygen to gradually enter the bottle. However wines can be affected by cork taint where the TCA chemical creates cardboard like aromas. Cork producers are working to reduce the risk of cork taint. Synthetic corks - generally made from plastic, generally used for wines for short term consumption, some can be used for wines intended for long term storage. Screw caps - have become more popular over recent decades. They do not taint the wine and allow less air in. Popular for wines where the winemaker wants to retain more fruity flavours. Still some debate about how well wines age under screw cap. Consumer acceptance varies.

Question 30

What are the best conditions for post-bottling maturation?

Answer 30

Wine should be kept undisturbed in a cool, dark place with a constant temperature of 10-15°C. There should be constant humidity and bottles sealed with a cork should be stored on their side.

Question 31

How does the clarity of juice affect white winemaking?

Answer 31

Freshly pressed grape juice has fragments from the grapes skins and pulp which can result in unpleasant aromas in the wine. Therefore the juice is clarified before fermentation. Some winemakers may choose to retain some solids. It is thought this makes the wine less susceptible to oxidation and can add complexity and texture.

Question 32

How does fermentation temperature and vessel affect white winemaking?

Answer 32

The optimum temperature for white wine fermentation is 12°C to 22°C. At too low temperatures pear drop aromas are created and the wine can fail to capture varietal aromas. At higher temperatures varietal fruit character will be lost but non-fruit aromas may develop. Where stainless steel vessels are used they can control the temperature to prevent it from getting too high. It is less easy to control temperature in barrels but as they are normally housed in cool cellars this can help dissipate heat.

Question 33

What are the winemaking choices for producing an inexpensive high volume white wine?

Answer 33

As these wines are often based on primary flavours, careful handling to avoid oxidation is important. Sulfur dioxide will be monitored throughout and juice and wine will be handled protectively. The grapes will be crushed and pressed. Acidification may be necessary if the grapes were grown in a warm climate. The juice will be highly clarified, using a centrifuge or filter to be quick. Stainless steel fermentation at a cool temperature will preserve fruity flavours. MLF may be blocked, the wine will be racked off its lees and stored in stainless steel. If oak flavour is desired, staves or chip will be used. The wines may contain some residual sugar from the addition of RCGM. Wines will be stabilised, fined and filtered and sulfur dioxide added before bottling.

Question 34

What are the winemaking choices for producing a premium aromatic white wine?

Answer 34

Aromatic juice needs to be handled carefully to retain the fruit and floral aromas. SO₂ will be monitored. Some skin contact may be permitted. The juice will be clarified, a gentle method of clarification will be used. Inert vessels will be used, including stainless steel or large old oak vessels if a little oxidation is required. Cool fermentation temperatures will encourage primary aromas, ambient yeast may be used. If some sweetness is required the fermentation will be stopped early by chilling or adding SO₂. MLF is avoided by adding SO₂ as this may interfere with fruit aromas. Some lees contact may be desired to add flavour and texture. New oak is generally avoided, wines are bottled soon after fermentation. Level of clarification and stabilisation can vary.

Question 35

What are the winemaking choices for a premium non-aromatic wine?

Answer 35

The grapes can be crushed or loaded into the press whole. Some controlled exposure to oxygen at this stage is thought to improve the wine's ability to age. Clarification is carried out using a gentle method such as settling. Some solid matter may be retained to add to complexity and texture. Fermentation may take place in a range of vessels, temperatures and yeasts may vary according to the wine style desired. Many post-fermentation options can be used. Choices will be made about type of oak, size of oak, age of oak. MLF and extended lees contact may occur to add a richer mouthfeel. Wines may be fined and filtered before bottling.

Question 36

In sweet winemaking, how is the fermentation stopped?

Answer 36

The fermentation can be stopped by fortification or adding SO₂ or chilling the wine. Fortification takes place by adding a neutral grape spirit to a fermenting wine. This kills this yeast and stops the fermentation. Adding SO₂ or chilling the wine will stop the fermentation, then yeast must be removed by filtration. This typically results in wines that are low in alcohol.

Question 37

In sweet winemaking, how does adding a sweet component affect the wine?

Answer 37

In countries like Germany süssreserve is added to dry wines to make them medium sweet. The grape juice will be filtered before fermentation or SO₂ can be added. RCGM can also be used, often to add a little sweetness to high-volume inexpensive wines.

Question 38

What are 4 ways of concentrating grape sugars?

Answer 38

1. Noble rot - Grapes are fully ripe, in a region with misty mornings and dry sunny afternoons. Damp conditions allow the rot to grow on the grape, the fungus punctures the skin of the grape leaving tiny holes. In the warm sunny afternoons the water evaporates from the grapes concentrating sugars, acids and flavours. The fungus adds flavours such as honey and dried fruit. 2. Drying grapes on the vine - referred to as passerillage. Grapes dehydrate and turn into raisins on the vine, increasing the sugar content in the juice. Warm dry autumns are needed. The wines have an over-ripe, dried fruit flavour and textured mouthfeel. They are sometimes labelled 'late harvest'. 3. Drying grapes after picking - healthy grapes are dehydrated, concentrating the sugar. Conditions must be warm and dry, and any rotten grapes removed. This is used in the passito wines of Italy and can give raisin flavours. 4. Freezing grapes on the vine - healthy grapes left on the vine until winter. They are picked when frozen, when pressed ice is trapped and removed and sugar content of juice increases. The is used for Eiswein and Icewine. The wines have pure varietal character. The effect can be artificially replicated by freezing grapes in the winery.

Question 39

How does pre-fermentation extraction affect red winemaking?

Answer 39

Macerating the crushed grapes at a low temperature before fermentation will extract colour and flavour compounds.

Question 40

How does temperature control affect red winemaking?

Answer 40

The temperature for red wine fermentation is 20°C to 32°C. The warmer temperature will aid extraction of colour, flavour and tannin. Care must be taken not exceed 35°C as this will kill the yeast. Control of temperature can allow the winemaker to control how much colour, flavour and tannin is extracted.

Question 41

What are the options for cap management techniques?

Answer 41

Punching down - the cap is pushed back into the fermenting juice either by hand or mechanically. Care must be taken not to overwork the cap, particularly at the end of the fermentation. Pumping over - the fermenting juice is drained from the bottom of the vat then pumped over the top. This is a popular technique and is a good way of dissipating heat and oxygen. Pumping over - the fermenting juice is drawn off from the bottom of the vat, put into another vessel, then pumped back over the cap. This is very extractive and would normally only be used once or twice during fermentation. It is a good way of dissipating heat. Rotary fermenters - fermentation takes place in rotating horizontal tanks, the juice is in constant contact with the skins.

Question 42

What are the options for fermentation vessels in red winemaking?

Answer 42

The cap management techniques required for red winemaking mean that red wines are usually fermented in large open topped vessels. They can be made from oak, concrete, or steel. Fermentation in oak barrels is impractical.

Question 43

How does post-fermentation extraction affect red winemaking?

Answer 43

This will encourage further extraction of tannin, this may be desirable depending on the style. Very long post-fermentation maceration can help to create a smoother tannin structure.

Question 44

What are the options for the press wine in red winemaking?

Answer 44

At the start of pressing the wine may be similar to the free run wine, but as pressing continues the wine becomes deeper in colour with higher tannin. The different stages of the pressing can be divided into press fractions which may then be blended back into the wine later.

Question 45

How does carbonic maceration work?

Answer 45

Whole, uncrushed bunches are placed into vats that are then filled with CO₂ to remove all the oxygen. Intracellular fermentation starts, once the level of alcohol reaches 2% abv the skins start to split and the juice is released. The grapes are pressed to separate the skins, yeast complete the fermentation off the skins. The method extracts colour but little tannin, the wines are fruity with notes of banana, bubblegum and kirsch.

Question 46

How does semi-carbonic maceration work?

Answer 46

Whole, uncrushed bunches are placed into vats. The grape sat the bottom of the vat are crushed under the weight of the grapes above and some juice is release. Ambient yeast ferment the juice producing CO₂ which fills the vat and the remaining intact berries undergo carbonic maceration. When the intact berries split, the grapes are pressed and yeast complete the fermentation. In some instance the fermentation may complete on skins, the grapes will be broken up using punching down. This can result in better integration of flavours from intracellular fermentation and fresher fruit character.

Question 47

How does 'whole bunches with crushed fruit' work in red winemaking?

Answer 47

Whole bunches are mixed in with crushed fruit at the start of the fermentation. The whole bunches become submerged under the cap and intracellular fermentation takes place. The whole bunches are progressively crushed as the cap is punched down. This gives wines a silkier texture and brighter fruit character.

Question 48

What are the winemaking choices for high-volume, inexpensive red wines?

Answer 48

The wines are typically made in a fruity low-tannin style. The juice will be handled protectively with SO₂ level monitored. The grapes will be destemmed and crushed. Acidification may be needed due to the warm climates the grapes are typically grown in. Pre-fermentation maceration is possible, but may be less likely if space is needed and wine is wanted quickly. Fermentation with commercial yeast at 22°C to 25°C to maximise fruity flavours. Cap management will vary but typically the cap will not be heavily worked. Post-fermentation maceration generally avoided due to constraints on space and time. Carbonic or semi-carbonic maceration would also be an option. Wines may be stored in steel, or if oak is used it is old oak or staves or chips. Wines will be stabilised, fined and sterile filtered, SO₂ levels will be topped up to reduce the risk of oxidation.

Question 49

What are some of the winemaking choices for a premium Cabernet Sauvignon wine?

Answer 49

Cabernet Sauvignon is usually destemmed and crushed as the stems can give an astringent character. Pre-fermentation maceration can help with colour extraction. Fermentation tends to be warm at 26°C to 30°C as this will encourage sufficient extraction while maintaining fruity flavours. Extractive cap management will be avoided toward the end of the fermentation. Post-fermentation maceration may be encouraged to soften existing tannins. Oak maturation is common, a high proportion of new oak can be used without overpowering the wine, 12 to 18 months is typical. The wines will often be blended with other varieties like Merlot that can soften the structure.

Question 50

What are some of the winemaking choices for a premium Merlot wine?

Answer 50

Premium Merlots tend to be made in two ways: 1. Grapes harvested as late as possible to get maximum colour, concentration of ripe flavours and smooth tannins. The wines are often matured in new oak. This is the 'international' style. 2. Grapes are harvested earlier to make a wine with medium body and alcohol, higher acidity and some herbaceous aromas. This is more commonly seen in Bordeaux. More generally - the grapes are destemmed and crushed, pre-fermentation maceration may occur, generally extraction during fermentation is less rigorous, oak maturation is common for 12 to 18 months.

Question 51

What are some of the winemaking choices for premium Pinot Noir?

Answer 51

Some winemakers will choose to destem and crush their fruit, followed by pre-fermentation maceration to extract colour and flavour. Other winemakers may choose to include a proportion of whole bunches in the ferment, which can enhance the red fruit and floral character. Fermenations can be cooler if aiming for a lighter fresher style, warm temperatures enable more colour, flavour and tannin to be extracted. Post-fermentation maceration is not widely practised. It is often matured in oak for 12-24 months, although too much new oak can be overpowering so second and third fill barrels are often used. Pinot Noir is not normally blended with other varieties.

Question 52

What are some of the winemaking choices for premium Syrah/Shiraz?

Answer 52

In warm climates wines tend to be full bodied, intensely ripe and high in alcohol. These wines typically undergo vigorous cap management to extract maximum colour, flavour and tannin. A high proportion of new oak can be used. A more restrained style from earlier harvested grapes or moderate climates can be made using gentler cap management techniques, and may include a proportion of whole bunches in the fermentation. A fine tannin structure may be achieve by extended post-fermentation maceration. Winemakers often use bigger barrels or older oak for this more restrained style.

Question 53

What are some of the winemaking choices for premium Grenache/Garnacha?

Answer 53

Destemmed and crushed. Pre-fermentation maceration - colour and flavour Some producers retain proportion of whole bunches to enhance the ripe red fruit flavours. Cap management - punching down widely used. Post fermentation maceration to enhance tannin structure, but Grenache usually drained off the skins. Normally matured in large, old oak so as not to overwhelm flavours. Mostly blended with other varieties - add fresher fruit, more colour and tannin.

Question 54

What are the three ways of making rosé wine?

Answer 54

1. Direct pressing - black grapes are crushed and pressed in the same way as in white wine production. This extracts little colour from the skins, care has to be taken so as not to extract too much tannin. This method produces very delicately coloured wines. 2. Short maceration - black grapes are crushed and allowed to macerate to extract colour and flavour. The length of the maceration determines how much colour and tannin will be extracted. It may extend into the start of the fermentation. The free run juice will then be drained off the skins and fermented at a cool temperature. 3. Blending - a small quantity of red wine is added to a white wine to produce a rosé wine. This is not permitted within the EU with the exception of Champagne. Some fruity inexpensive new word rosé wines are made this way.