D1.C13. General Winemaking Options Flashcards
1
Q
Name two gases that play fundamental role in winemaking and maturation
A
- Oxygen
- Sulphur dioxide
2
Q
What are the parameters which determine whether oxygen will have a positive or a negative effect during winemaking?
A
Timing and the amount of oxygen exposure
3
Q
What are the adverse effects of oxygen on fresh, fruity wines?
A
- Aroma compounds (like thiols in Sauvignon Blanc) breakdown leading to loss of fruitiness
- Products of oxidation reactions may contribute unwanted aromas to the wine like acetaldehyde
- The colour of white wines can also turn darker, becoming gold and then brown
4
Q
Why are the red wines more resistant to oxidation?
A
Because, phenolic compounds in red wines have an anti-oxidative effect
5
Q
The practice of minimising oxygen exposure during the winemaking process is sometimes called..
A
Reductive or protective winemaking
6
Q
How can the effect of oxygen on must and wine be limited in the winery?
A
- Avoiding ullage in vessels by topping up
- Using inert gases like CO2, N or Argon
+ Flushing vessels, pipes and machinary
+ To fill the empty headspace - Adding SO2
- Using impermeable containers: Stainless steel and thick concrete vessels, glass bottles with screwcaps
- Keeping cool constant temperatures
7
Q
What are the positive effects of oxygen for the wine?
A
- It is required at the start of fermentation
- Lack of enough oxygen in winemaking or storage can lead to reductive off-flavours
- In the production of some white wines, exposing the must to oxygen before fermentation is thought to lead to greater oxidation stability in the wine, and to result in increased ageing potential
- In red wines, oxygen is essential in the reaction between anthocyanins and tannins that leads to greater colour stability
- Exposure to oxygen over time also leads to changes in the aromas/flavours of wine which gives a greater range and diversity of characteristics: fresh fruits become dried fruits and notes such as honey, caramel, coffee, leather and mushroom
8
Q
How can the oxygen exposure be increased during wine making?
A
- Use of cap management techniques
- Use of small wooden barrels that can only contain a small volume of wine
- Increasing the number of rackings or amount of lees stirring during ageing
- Allowing ullage in wine containers
- Use of techniques that involve pumping oxygen through the must
9
Q
Name two factors that favors the development of Brettanomcyes?
A
- Oxygen exposure
- Residual sugar
10
Q
What are the major effects of sulfur dioxide?
A
- Anti-oxidant
- Anti-microbial
- Anti enzymatic (inhibits tyrosinase and laccase)
- Wine refreshment: By binding acetaldehyde
11
Q
In which form can sulfur dioxide be applied during winemaking process?
A
- Solid:
+ Matches, tablets (SO2)
+ Powder: Potassium metabisulfite: Dusted on fresh harvested grapes. Release 50% of its weight as SO2) - Liquid: SO2 liquifies under -15°C and 3 bars of pressure)
12
Q
What is the amount of SO2 produced during fermentation?
A
Less than 10 mg/L
13
Q
What are the maximum amount SO2 allowed for red and white wines in the EU?
A
- Red wines: 160 mg/L
- White wines: 210 mg/L
14
Q
How are the maximum amount of SO2 allowed in sweet wines when compared with dry wines?
A
It is higher
15
Q
After which level of SO2 in wine, it must be stated in the label? Why?
A
- 10 mg/L
- The concentrations of SO2 found in wine are far below toxic levels; however, even at these levels some people can have some allergic reactions
16
Q
In which forms, can SO2 be found in must or wine
A
- Bound SO2: Inactive against oxidation and microbes
- Free:
+ Inactive form (majority)
+ Molecular: Most effective
17
Q
What is the relation of pH with the levels of SO2?
A
A greater proportion of free SO2 is in molecular form at lower pH levels
18
Q
What are the factors that determine the influences and the effectiveness of the added SO2?
A
- Timing
- Size
19
Q
What are the critical steps in winemaking, where adding a larger amount of SO2 is more effective than adding smaller amounts throughout the entire winemaking process?
A
- Crushing
- End of malolactic conversion
- Bottling
20
Q
Why do the quality-conscious winemakers aim to limit the use of SO2, other than legal restrictions?
A
High levels of SO2 can dull wine aromas/flavours and sometimes can cause the wine to taste harsh
21
Q
What are the practices that can reduce the amount of SO2 needed?
A
- Good winery hygiene
- Effective grape sorting
- Limiting oxygen exposure
- Keeping the grapes, must and wine in cool conditions
22
Q
During transportation to winery, grapes are vulnerable to:
A
- Oxidation
- Ambient yeasts
- Acetic acid bacteria
23
Q
What measures can be taken to minimise the threats of oxidation and microbial infection?
A
- Harvesting and transporting the grapes at night
- Addition of SO2
- Keeping the grapes in cold storage rooms in the winery
- Sanitising the harvesting equipment/bins
- Collecting and transporting the grapes in small crates to minimise crushing
24
Q
What are the transportation options for hand-harvested and machine-harvested grapes
A
- Hand harvested
+ To transport the grapes in small crates: Minimal crushing
+ The small crates are tipped into larger hoppers (large bins) for transport to the winery: More crushing - Machine-harvested: The fruit has already been destemmed and and is typically transported in large containers, with some release of juice
25
On arrival to winery, a number of options are possible and will depend on:
- Volume of the grapes
- Whether they have been hand- or machine-harvested
- Health and the quality of the grapes
26
How can large volume of grapes be moved on reception?
- Conveyor belt (gentler with higher quality potential)
- Screw conveyor
27
How can smaller volume of grapes be moved on reception?
Hand-harvested grapes can be moved around manually, often with a pallet truck or forklift
28
When does the winemaker choose to chill grapes on reception?
If the grapes are warm when they reach the winery
29
What are the advantages of chilling the grapes on reception?
- Help to preserve fruity aromas
- Reduce the threat from spoilage organisms
- Also advantageous to store the grapes if all the sorting tables, presses and other equipment is already in use
30
What are the options for chilling?
- Refrigeration unit: Used for whole bunches. Slower
- Heat exchanger: When the grapes are in a more fluid format (e.g. fruit that has been machine picked, grapes that are destemmed and possibly crushed). Faster
31
What is the disadvantage of chilling the grapes?
Higher cost due to equipment and energy cost
32
How can a grape grower decrease the need of chilling?
By harvesting at night or early in the morning
33
What is the French word for sorting?
Triage
34
The level of grape sorting depends on which factors?
- Ripeness and health of the fruit
- Intended final wine quality and price
- Whether any sorting has been carried out in the vineyard
- Physical state of the grapes (depending on the choices of transportation to winery)
35
What are the factors that increase the cost as grape sorting levels increase?
- More labour and time
- Less yield
36
How can grape sorting change in bad and good vintages?
- In poor years and in cool climates a greater of level of sorting may simply be required
- In very good years, fruit may arrive near perfect condition and require little sorting. MOG may still need to be removed
37
What is the usual sorting strategy for inexpensive wines?
No sorting
38
What are the key determinants of sorting?
- The health of the grapes on arrival at the winery
- The quality of the wine to be made in relation to the price that can be gained for the wine
39
What are the sorting options for quality wines?
- Removing unwanted grapes/bunches before picking or during hand-harvesting
- Sorting by hand on a table or a moving or vibrating belt (the latter also removes MOG) before or after destemming or both
- Optical sorting: Can be done either in a harvesting machine or at reception in the winery
40
Optical sorting is used for kinds of wines on price basis? Why?
- Only in premium or super-premium wines
- Due to the cost of the machine and high level of selection
41
In which conditions, the grapes are not destemmed?
- Red wine fermentations that use some whole bunches
- Carbonic maceration
- Whole bunch pressing for some white wines (e.g. common for high-quality sparkling wine)
42
What happens when the stems are not ripe in whole bunch fermentation?
They can convey unwanted green flavours and bitter tannins to the wine
43
What is crushing?
Application of sufficient pressure to the grapes to break the skins and release the juice, making it available for fermentation
44
What happens if the pressure applied for crushing is not gentle enough?
The seeds are crushed which would add bitterness
45
What is the traditional way of crushing the grapes?
Human feet
46
What does the term "must" refer to?
The substance that is being fermented. (The mixture of grape juice, pulp, skins and seeds that comes from the crusher but for white wines, must may also refer to the grape juice that is fermented)
47
Why soft pressing is important for both white and red wines?
- White: Not to extract tannins and avoid excessive amount of solids
- Red: To avoid extraction of excessive tannins and bitterness from skin and seeds
48
Name the types of presses that can be used in winemaking
- Pneumatic press (air-bag press)
- Basket press (Vertical, Champagne)
- Horizontal screw press
- Continuous press
49
Which of the presses that can be used in winemaking is most popular?
Pneumatic press
50
What are the advantages of pneumatic presses?
- It can be programmed to exert different amounts of pressure
- It can be flushed with inert gas before use to protect the juice or wine from oxidation
51
What are the disadvantages of pneumatic presses?
- Need for initial investment
- Need for batch processing
52
What are the disadvantages of basket presses?
- Not sealed vessels so, can not be flushed with inert gases to minimize oxidation
- They hold smaller press load, together with the need for batch processing, it is much more labour intensive therefore much more suitable for small wineries paking premium wines
53
What are the disadvantages of horizontal screw presses?
- Less gentle
- Need for batch processing
54
What is the advantage of continuous presses?
Grapes are continually loaded into the press as it works by using a screw mechanism; this allows for quicker pressing of large volumes of grapes
55
What is the disadvantage of continuous presses?
They are less gentle than pneumatic and basket presses and therefore best suited to producing high volumes of inexpensive wines
56
What are the aims of must adjustment?
Create a more balanced wine especially if the is a compromise in achieving optimum ripeness of sugars, acids, tannins and flavours
57
Must adjustments are generally made after which process during white winemaking?
Must clarification
58
What is the aim of enrichment?
Increase the alcoholic content of the final wine
59
Which methods can be used to enrich the must?
- Adding sugar, grape concentrate or RCGM
- Concentration
+ Reverse osmosis
+ Vacuum extraction
+ Chilling
60
What is the source of sugar used in Chaptalization?
Can be beet or cane
61
In which regions of Europe Chaptalization is allowed?
Cooler parts only. Warmer areas (broadly southern Europe) are not permitted to add sugar, but they can add grape concentrate or RCGM, again within limits
62
What are the minimum natural potential alcohol, maximum allowed enrichment and maximum alcohol level in final wine (if enriched) for Zone A (Germany, exc Baden and UK)
- Minimum natural potential alcohol: 8%
- Maximum allowed enrichment: + 3%
- Maximum alcohol level in final wine: 11.5% (12% for red wines)
63
What are the minimum natural potential alcohol, maximum allowed enrichment and maximum alcohol level in final wine (if enriched) for Zone CIIIb (Most of Portugal, southern Spain, southern Italy and Greece)?
- Minimum natural potential alcohol: 9%
- Maximum allowed enrichment: + 1.5%
- Maximum alcohol level in final wine: 13.5%
64
Why adding sugar is done when the fermentation is underway?
Because the yeasts are already active and can therefore cope better with the additional sugar in the must
65
Which of the concentration techniques to enrich the must is used more widely than the others? Why?
- Cryoextraction is more widely used than reverse osmosis and vacuum extraction
- Because reverse osmosis and vacuum extraction is expensive
66
How can the potential alcohol in the must be lowered?
By adding water to the grape must
67
What is the disadvantage of adding water to decrease the potential alcohol in the must?
It also dilutes the aromas/flavours and acids
68
Is adding water to reduce the potential alcohol level in the must a common practice?
No, it is only legal within some countries or regions. e.g. in California water may be used within the addition of other wine processing additives
69
Is acidification a common practice?
Acidification is routine in most warmer parts of the world for inexpensive and mid-priced wines and many premium wines
70
Which acids can be used for acidification?
- Tartaric acid (most common)
- Citric acid (not permitted in EU)
- Malic acid
- Lactic acid
71
Why is malic acid used less for acidification?
As it could be turned into lactic acid by malolactic conversion
72
When can lactic acid be used for acidification?
If adjustments need to be made after malolactic conversion
73
Although acidification can be done before, during or after fermentation, why do the winemakers usually prefer to acidify, before fermentation starts?
- To benefit from the effects of a lower pH
- They believe that integration of the acid is better if done at this stage
74
Which processes in winemaking practice can affect total acidity and the pH of the wine, leading to the need for acid adjustment?
- Malolactic conversion
- Tartrate stabilization
75
What is the amount of permitted acidification in the coolest (Zone A) and the warmest (Zone CIIIb) zones of EU?
- Zone A: -1 to 0 gr/L (only deacidification)
- Zone CIIIb: 0 to 2.5 gr/L
76
Why are the winemakers in EU not allowed both to chaptalize and acidify the wines?
To prevent the wines being stretched by the two additions
77
When is deacidification needed?
In cool climates where grapes may have to be picked before they are fully ripe (e.g. due to the threat of poor weather)
78
Which methods are used for deacidification?
- Adding calcium carbonate or potassium carbonate by formation and precipitation of tartrates
- Ion exchange (expensive)
79
What are the reasons of adding powdered tannins to the must?
- To help clarify must
- To help stabilize the color in red wines
- To improve the mouthfeel in red wines
80
What does yeast need initially for fermentation? Why?
- Oxygen
- To multiply quickly
81
When does the yeast switch to fermentation?
When all oxygen has been used up
82
What are the right conditions for alcoholic fermentation?
- Viable temperature range
- Yeast nutrients esp nitrogen
- Absence of oxygen
83
What are the products of alcoholic fermentation other than alcohol, CO2 and heat?
- Very small amounts of SO2
- Wine aromatics
- Glycerol
84
In which ways can alcoholic fermentation produce wine aromatics?
- From aroma precursors, released by the action of yeast
+ Thiols: 4MMP in Sauvignon blanc
+ Terpenes: Linalool, geraniol in Muscat
- Created by the yeast:
+ Esters: Many fruity flavours like banana from carbonic maceration
+ Reductive sulfur compounds
85
What are the advantages of Saccharomyces cerevisiae
- It can withstand well high acidity
- It can withstand well increasing alcohol level
- It is fairly resistant to SO2
86
Why does Saccharomyces Cerevisiae quickly becomes the dominant yeast even in wild fermentations?
Because most of the ambient yeasts like Klockera and Candida will die out as the alcohol rises past 5 %
87
What are the advantages of using ambient yeasts for fermentation?
- They add complexity by producing different aroma compounds
- It costs nothing
- Yeast population in a must can be unique to a place or region
- It can be used as part of the marketing of the wine
88
What are the disadvantages of using ambient yeasts for fermentation?
- Fermentation may start slowly: It is dangerous for the build-up of unwanted volatile acidity and the growth of spoilage organisms (such as Brettanomyces) and bacteria, potentially leading to off-flavours
- Fermentation to dryness may take longer
+ Not desirable in a high volume winery
+ Increased risk of a stuck fermentation, leaving the wine in a vulnerable state to spoilage organisms
- A consistent product cannot be guaranteed
89
What are the practices that can be performed to suppress the ambient yeast before adding cultured yeasts for fermentation?
- Cooling down the must
- Adding SO2
90
What are the advantages of using cultured yeasts for fermentation?
- They produce reliable, fast fermentation to dryness
- They produce low levels of volatile acidity
- Less danger from spoilage organisms
- Consistent product from one vintage to another
- Large selection of cultured yeast strains available commercially, the winemaker’s choice can also affect the style of wine created
91
Which yeast is preferred for the must with high potential alcohol or re-fermeting sparkling wine?
Saccharomyces bayanus
92
What are the disadvantages of using cultured yeasts for fermentation?
- Similarity of fruit expression (and hence the charge of ‘industrial wine’)
- Adds the cost
93
What are the results of low nitrogen levels in the must during fermentation?
- Production of undesirable sulfur compounds
- Stuck fermentation
94
Which yeast nutrients can be added if the nitrogen levels are low in the must?
- Diammonium phosphate (DAP)
- Thiamine (Vit B1)
95
The speed of fermentation is related to:
Temperature of the must
96
Why do the winemakers may prefer a relatively warm start to fermentation (e.g. 25°C / 77°F)?
To get the yeast population established, and then monitor it regularly and cool or warm the must as required
97
What is the ideal fermentation temperature range for producing fresher, fruitier white wines and rosé?
12–16°C
98
What is the ideal fermentation temperature range for producing easy-drinking fruity red wines?
17–25°C
99
What is the ideal fermentation temperature range for producing red wines with pronounced flavour concentration and high tannins?
26–32°C
100
Above which temperature the fermentation may slow down and stop as yeasts struggle to survive, with risk of a stuck fermentation?
35°C
101
What are the options for temperature control during fermentation?
- Moving to a cooler or warmer room, if fermentation vessels are small enough to move
- Pumping over (delestage)
- Using temperature control fermentation vessels that use either water or glycol in jackets that surround vessels (typically stainless steel)
102
What are the advantages of stainless steel fermentation tanks?
- Easy to clean
- Large range of sizes
- High degree of control over the temperature
- High level of mechanization (automatic pump-over, automatic emptying etc)
- Very good at protecting the wine from oxygen
- Do not add flavours
103
What is the disadvantage of stainless steel fermentation tanks?
They require substantial initial financial investment in the tanks themselves and in computerised temperature-control systems.
104
What are the advantages of concrete fermentation tanks?
- They maintain an even temperature much more efficiently than stainless steel
- Smaller, egg-shaped vessels in concrete are said to set up convection currents that mix the fermenting must and mix the lees during maturation (very expensive)
105
Which countries have retained their traditional large wooden fermentation casks?
- France (Alsace)
- Germany
- Italy
106
What are the advantages of wood fermentation tanks?
- Retains heat well
- Some winemakers value the small amount of oxygen that fermenting red wine in oak provides
- Can be used many times so inexpensive over the long term
107
What are the disadvantages of wood fermentation tanks?
- Great care has to be taken with hygiene as the pores in wood can harbour bacteria and spoilage organisms
- They require capital investment when new large oak casks are bought
108
Although white wines may also be fermented in small wooden barrels, this relatively rare for red wines. Why?
Due to the need to manage the cap of skins
109
What are the pros and cons of plastic fermentation vessels?
- Plastic vessels are light, versatile and useful for small-batch fermentations
- However, plastic is permeable to oxygen and it can be difficult to control the temperature in plastic vessels
110
What are the different names used for terracotta pots?
- Amphora
- Qveri (Georgia)
- Tinaja (Spain)
111
Malolactic conversion happens at which stage of winemaking process?
It typically happens after alcoholic fermentation and occasionally during it
112
Which conditions encourage malolactic conversion?
- Temperature between 18–22°C
- A moderate pH (3.3–3.5)
- Low total SO2.
113
Historically, how does malolactic conversion used to happen? How does it start now?
- Historically it often happened spontaneously in the spring following the harvest as the temperature rose in the cellar
- Now it is started bu inoculating cultured lactic acid bacteria and making sure that optimum conditions are available
114
Which conditions prevent malolactic conversion?
- Temperature below 15°C
- Low pH
- Moderate levels of SO2
115
What can winemakers do avoid malolactic conversion?
- Adding lyzozyme which kills the lactic acid bacteria
- Filtration
- Move any batch of wine going through malolactic conversion to another part of the winery to avoid the spread of lactic acid bacteria
116
Do all wines go through malolactic conversion?
Red wines routinely go through malolactic conversion. It is a winemaker’s choice for white wines
117
What are the outcomes of malolactic conversion?
- Reduction in acidity and rise in pH: This is because lactic acid is a weaker acid than malic acid
- Some colour loss in red wines: Not a problem except in very pale red wines
- Greater microbial stability: It prevents malolactic conversion to spontaneously happen later
- Modification of the flavour: A slight loss of fruit character may occur with the addition of buttery notes (notably in white wine).
- Increase volatile acidity
118
What is the advantage and disadvantage of conducting malolactic conversion in barrels?
- Advantage: Ability to be able to stir the lees at the same time and promote better integration of the flavours
- Disadvantage: More work because barrels may be at different temperatures and so will need monitoring individually
119
Why do some winemakers prefer to promote malolactic conversion at the same time as alcoholic fermentation?
- This can increase fruity characteristics (or alternatively reduces the loss of fruit character from the final wines)
- It shortens production times, saving money
120
Why should the winemaker aim to make small postfermentation adjustments if needed?
For not to upset the balance of the wine
121
What are the options to remove the alcohol from the wine
- Adding water (where permitted)
- Reverse osmosis (expensive)
- Spinning cone (only financially viable for large volumes of wine)
122
What is the difference between the reverse osmosis and spinning cone in terms of removal mechanism
- Reverse osmosis removes alcohol and water and then water is blended to recreate the wine
- Spinning cone removes alcohol and volatile aroma compounds and then aroma compounds are blended back into the wine
123
What practice can be performed to reduce unwanted color taints?
Fining
124
What practice can be performed to enhance the color intensity?
Adding very small amounts of the grape-derived colouring agent, MegaPurple (not permitted in some regions like Ribera del Duero)
