D1.C18. Specific Options for RedWine Making Flashcards
Many of the choices involved in red winemaking are focused on:
The extraction of anthocyanins, tannins and flavours from the grape skins
What is the general aim in red wine making?
To extract anthocyanins, tannins and flavours so that the wine is suitably concentrated and balanced, but not to extract too much
What are the factors that affect the extraction of anthocyanins, tannins and flavours?
- Temperature
- Time on skins
- The medium in which the extraction is taking place (tannins are more soluble in alcohol, anthocyanins in water)
Which processes in winification can lead to the alteration or loss of anthocyanin molecules?
- Lees aging
- Additions of SO2
Which interactions make anthocyanins more stable?
- Binding with the tannins
- Gentle oxidation of wine (micro-oxygenation, barrel aging)
What is the result of change in the composition of anthocyanins and anthocyanin - tannin compounds over time?
Wine becomes paler and gradually changes from ruby through to brown. However, this change is slower for anthocyanin-tannin compounds than anthocyanins
Is chilling the grapes in the winery needed for black grapes?
Although the phenolics found in the skins of black grapes make them less vulnerable to oxidation than white grapes, chilling still helps to slow down oxidation, as well as reducing the threat from spoilage organisms. Grapes may also be chilled now if cold soaking is planned
What is the key aim of maceration before fermentation?
To extract colour and flavours, without extracting tannins
What is the temperature range for cold soaking? Why?
- 4–10°C
- To reduce the rate of oxidation, the threat from spoilage organisms and the risk of a spontaneous fermentation starting
What is the duration of cold soaking for red wines?
3-7 days
What are the benefits of cap management techniques like punching down and/or pumping over during cold soaking?
- Aids extraction of flavours and colour
- To avoid the growth of spoilage organisms that need oxygen, such as acetic acid bacteria, on the top of the cap of skins
Why is cold soaking suitable for premium wines?
- It is gentle technique. Cold temperatures result in a slow extraction, which can easily be monitored and controlled to achieve the level of extraction desired
- There is a cost to cold soaking in the energy required to chill the wine and also, time taken for cold soaking (tying up valuable tank space)
Cold soaking is commonly used for which black grape variety? Why?
- Pinot Noir
- To promote colour intensity
What are the two techniques used for macerations using heat?
- Thermovinification
- Flash détente
How is thermovinification performed?
- The must is heated to around 50–60°C and sometimes higher
- The time spent macerating at this heat can range from a number of minutes to several hours (higher the temperature, shorter the maceration)
How is flash détente performed?
- Destemmed grapes are quickly heated to 85–90°C
and then rapidly cooled under a vacuum - This takes place in as little as two minutes
- The process bursts the cells in the grape skins allowing a very rapid extraction of anthocyanins and flavours
- The short time at high temperatures limits the risk of ‘cooked’ flavours developing
Why is flash détente used in high-volume wineries?
Because the vacuum system is expensive to buy
After performing macerations using heat, what are the options?
- The juice may be pressed off the skins before fermentation to produce a low tannin, fruity style wine or may be blended with higher quality wines bringing juicy, fruity flavours
- The juice may be fermented for a period of time on the skins if a style with more tannin is required.
What is the disadvantage of pressing of the skins before fermentation when maceration using heat is performed?
- Wines tend to have colour instability because there is not enough tannin to bind with the anthocyanins and form more stable compounds
What are the other benefits of using thermovinification and flash détente?
- Both flash détente and thermovinification can be particularly beneficial if the grapes are affected by botrytis (grey rot), as the high temperatures denature oxidative enzymes (called laccase) produced by the rot
- Flash détente can also be used as a treatment for smoke taint
What are the benefits of cap management techniques?
- Without mixing, the skins spend the fermentation macerating in the same small volume of liquid that surrounds them
- Avoiding a dry cap, which can harbor acetic acid bacteria
- Avoiding the production of reductive sulphur compounds by aerating the must
- It also helps to distribute the heat produced during fermentation and is therefore essential for temperature monitoring and control
What are the main choices for cap management?
- Technique/techniques to be used
- Frequency and duration of the technique/techniques of mixing
- Timing of mixing (more mixing at the start of
fermentation with less mixing at the end will extract more colour and less tannin)
What is the role of temperature on the extent of extraction by cap management?
Warmer fermentations will extract more than cooler fermentations
How can tannin extraction be reduced near the end of fermentation?
By cooling the wine
What are the ways to perform punching down (pigeage)?
- By hand
- By mechanised plunger
Why carrying out punching down procedure by hand is best suited to low-volume production of premium wines?
- Carrying out this procedure by hand is labour intensive
- It is only physically possible to punch down the cap
manually and ensure adequate mixing of the skins in relatively small, open top vessels. Small vessels mean more labour for monitoring
How is pumping over (remontage) performed?
Juice/wine is taken from near the bottom of the vessel and sprayed over the cap of skins. Usually around one-third to one-half of the liquid in the vessel is pumped and sprayed over
Why is punching down and rack and return techniques are also performed together with pumping over?
Because pumping over is a more gentle technique that sprays the liquid over the cap, rather than breaking up the cap, so punching down and rack and return is needed to extract enough colour, flavour and tannin
What are the advantages of pumping over?
- It can be carried out aerobically, by splashing the wine against the inside wall of the open vat, which can be beneficial for yeast health and avoidance of reductive off-flavours
- Modern wineries have pumps and hoses installed at each tank, and pump-overs can be pre-programmed to occur at certain times and for certain durations, reducing the need for labour
How is rack and return (delestage) performed?
- As the juice is pumped from one vessel into another vessel, the cap of skins falls down the vessel
- The juice is then pumped from the new vessel in through the top of the original vessel and is sprayed over the skins, which breaks up the cap and mixes the juice and
skins thoroughly
Why rack and return may be used only 1–3 times during the fermentation?
Because it is more extractive than pumping over or punching down
Rack and return is most commonly used for producing which style of wines?
For red wines where medium to high levels of flavour, colour and tannin are desired (e.g. Cabernet Sauvignon, Syrah)
What are the disadvantages of rack and return?
- It cannot be fully automated and requires labour to set up and monitor the process
- It requires a clean vessel to be available, which can be an issue in wineries that are operating at peak capacity
What are Ganimede® tanks?
- They are specialised tanks that bubble CO2 up through the must/wine
- Pressure builds up under the cap, until finally the cap burst
- It is relatively extractive technique like delestage
Why are Ganimede® tanks becoming increasingly common?
- Because it can be fully automated
- Oxygen can be used instead of CO2 if the winemaker wants or needs to expose the wine to oxygen
What is the disadvantage of Ganimede® tanks?
These specialised tanks are slightly more expensive than standard stainless steel tanks