D1 - Winemaking Flashcards
1
Q
Sources of aroma compounds of wines
A
- from grapes - methoxypyrazines and rotundone
- from grape precursors - Thiols and terpenes
- fermentation by products - esters, acetaldehyde, diacetyl, sulphur compounds
- oak - vanillin, lactones
2
Q
What does alcohol contribute to wine?
A
- fullness of body and mouthfeel
- sense of sweetness
- oral warmth
- above 14.5% it reduces aroma volatility and increases bitterness
3
Q
Key characteristics of tannins
A
- they bind with proteins in the mouth, producing a dry sensation
- when unripe they impart bitter taste
- RS can make them feel softer
- high acidity makes them feel harder
4
Q
EU classification for sweetness levels in still wines
A
- dry / sec / trocken - <4g/L
- medium dry / demi-sec / halb-trocken - 4 - 12g/L
- medium sweet / moelleux / lieblich - 12 - 45 g/L
- sweet /doux / suss - > 45g/L
5
Q
What is the foundation the conventional modern viticulture?
A
scientific understanding of the processes which convert must into wine.
The starting point was Luis Pasteur’s identification of yeast and bacteria in 1860
6
Q
Tools used by conventional winemaking
A
- Temperature control
- use of additives and processing aids
- manipulations with different levels of technology and complications
7
Q
Who can issue organic winemaking certifications?
A
- associations
- country authorities
- the EU
8
Q
What does “organic winemaking refer to?
A
Production of wine from organically-certified grapes, and complying with rules that restrict some practices.
9
Q
Levels of organic winemaking in the USA
A
- Organic Wine - no added SO2
- wine made from organic grapes
10
Q
Are Biodynamic winemaking practices universal?
A
No, they vary across countries.
Dementer sets guidelines, but each country’s body set their own specifications.
11
Q
What is the natural winemaking tenet?
A
“nothing is added, nothing removed”
12
Q
What are the winemaking decision that are generally agreed as essential for natural winemaking?
A
- ambient yeast
- no filtering or fining
- no, or minimal, addition of SO2
- use of organic/biodynamic grapes
13
Q
Effect of Oxygen in wine colour
A
- red wines lose colour and turn tawny
- white wines become darker and turn golden, an then brown
14
Q
Ways of reducing Oxygen exposure
A
- Avoiding Ullage
- Use of inert gases
- Addition of SO2
- use of impermeable containers
- keep cool constant temperatures
- seal the bottles with screw cap or vinolok
15
Q
How can Oxygen exposure be increased?
A
- Avoiding ullage without the use of inert gas
- use of cap management techniques that spray the wine
- use of small wooden barrels
- increase the number of rackings and lees stirring
- micro-oxygenation
- hyper-oxidation
16
Q
Positive role of Oxygen
A
- hyper-oxidation removes fragile components achieving longer shelf life
- gives the fermentation a quick start
- revitalises yeast if fermentation slows down
- prevents reductive taint during bottle-ageing
- triggers development of flavour compounds that provide “character”
- Improves colour stability
- promotes tannin polymerisation - softening
17
Q
Properties of SO2
A
- Antioxidant
- Antimicrobial/Antiseptic
- Anti-oxidasic
18
Q
Forms in which SO2 can be added to the must/wine
A
- gas
- liquid
- solid - sulfur dioxide, potassium metabisulfite or potassium bisulfite
19
Q
Critical winemaking stages at which SO2 is normally added
A
- freshly harvested grapes
- after crushing/ before clarification in whites
- after AF in whites or MLF in reds
- prior to bottling
20
Q
Key points of chilling the grapes at the reception in the winery
A
- crates with the grapes are placed in a store room for hours
- grapes in a semiliquid state can be chilled by a heat exchanger
- it reduces the rate of oxidation
- particularly valuable in regions with high summer temperatures
- increases cost and slows down the processing of the grapes
- can be advantageous when processing several different grapes/plots
21
Q
When can the sorting of the grapes be carried out?
A
- at the vineyard
- at the reception
- after destemming
22
Q
ways of sorting the grapes at the winery
A
- by hand in a table of conveyor belt
- by a high-tech machine that scans individual grapes
23
Q
how can the grapes be moved when they are received at the winery?
A
- with a conveyor belt
- screw conveyor (lower potential quality)
- manually with a forklift
24
Q
What does the term crushing refer to?
A
to the application of pressure to break the skin of the grape and release the juice, so that it is available for fermentation
25
What is the aim when pressing must for white wine production?
Maximising the juice extraction without extracting tannins and avoid an excessive amount of solids
26
What is the aim when pressing red wines?
Maximising the amount of wine extracted without breaking the seeds, which are soft after the maceration and would otherwise impart an overtly bitter taste
27
Name the different types of presses
- Pneumatic
- basket
- horizontal screw
- continuous
28
Explain the mechanism of the Pneumatic press.
| What other name can it receive?
- "air bag" press
- it consists of an horizontal cylinder with a bladder on one of the sides. Grapes are loaded on one of the sides and, as the bladder inflates, they are pushed against the grates the other side
29
advantages and disadvantages of the pneumatic press
```
advantages
- it can be flushed with inert gas
- it can be programmed to exert different amounts of pressure
disadvantage
- high initial investment
```
30
Explain the mechanism of the basket press
Cylindric vertical basket in which the grapes are loaded. The pressure is applied from above .the juice/wine will run through the gaps of the basket and collected by a tray at the bottom of the press
31
Advantages and disadvantages of the basket press
```
advantages
- gentler than the pneumatic press
- lower investment
disadvantage
- is not enclosed - cannot be flushed with inert gas
- can only be use with smaller batches
- more labour intensive
```
32
What is the pomace ?
the solid remains of grapes after pressing
33
Options when clarifying a white must
- sedimentation
- centrifugation
- flotation
- pectinolytic enzymes
34
Options when clarifying wine
- Sedimentation
- centrifugation
- Finning
35
Explain sedimentation
The wine/must is placed in a tank and chilled, to avoid oxidation/spoilage, and left to let the solid particles in suspension settle by gravity. Then is is racked to another tank and the sediments are left behind
The rate depends on the size and shape of the vessel
36
Explain Centrifugation
The must/wine is rapidly rotated by a centrifuge, a machine that uses centrifugal forces to separate liquid from solids.
It is very quick and efficient, but very costly in terms of equipment
It also increases O2 exposure, unless it is flushed with inert gas (further increasing costs).
It can be used continuously, reducing time and labour demand
37
What is Flotation? When can it be used?
- A technique for clarifying white musts, it cannot be used in final wines
- It involves bubbling gas through the must. as bubbles rise, they catch and bring solid particles with them, which are skimmed off the top of the vessel.
- Nitrogen is traditionally used, but O2 can also be used to hyper-oxidise the wine at the same time.
- It is most effective when a fining agent is used.
- It is fast, it can be carried out continuously, no chilling is needed. But initial investment on equipment is required, as well of the ongoing gas cost
38
How do the pectinolytic enzymes act? When can they be used?
- They break down pectin contained in cell walls of the plants/fruits. This allows a quick separation between the solids and liquids.
- it can only be used when clarifying must.
39
What is hyper-oxidation? How is it carried out?
- The deliberate oxidation of the must before fermentation. It is carried out to destroy and precipitate the most fragile components of the wine, resulting in a final wine that is more stable towards oxygen.
- A special tank is needed in which O2 is bubbled from the bottom of the vessel
40
What does the term "enrichment" refer to?
| What are the different options?
- it refers to a range of practises/processed carried out to increase the concentration of sugar in the must, in order to achieve a higher alcoholic strength in the final wine.
- Options: adding dry sugar, grape must or CRGM; vacuum distillation, cryo-extraction, reverse osmosis.
41
What does de-acidification process consist of?
- achieved by the addition of a Carbonate (calcium or potassium) which neutralises acids
- it only has effect on tartaric acid, not in the harsher malic acid
- sometimes a small batch is completely neutralised, and then blended back to the bulk
42
Why are "nutrients" sometimes added to the must?
| What products can be added?
- to increase nitrogen levels in the must, so that yeast can carry out a sound fermentation and avoid the synthesis of sulfur off-odours.
- Options: DAP, Thiamine
43
As well as acohol, CO2 and heat, what else do yeast produce during fermentation?
- SO2
- acetic acid
- aroma compounds
- glycerol
- higher alcohols
44
In what conditions do yeast produce ethanol? How are those conditions achieve in wine fermentation?
- in anaerobic conditions
- this is quickly achieved as the Dissolved oxygen is absorbed by the growing population of yeast. Which is required to their reproduction
45
What does "killer" yeast refer to ?
Yeast strains that produce compounds that poison other strains
46
Common species of ambient yeast
- Kloeckera
| - Candida
47
Advantages of using wild yeast
- no cost
- marketing tool
- yeast are unique to the vineyard/winery
- more complexity in aroma compounds
48
Disadvantages of using wild yeast
- fermentation starts slowly
- fermentation to dryness takes longer
- increased risk of stuck fermentation
- consistent product cannot be guaranteed
49
Advantages of using cultured yeast
- reliable fermentation to dryness
- consistency
- ability of selecting specific strains for the style of wine being produced.
- low levels of VA
50
Disadvantages of using cultured yeast
- cost
| - consistency in fruit expression may limit terroir expression
51
What temperature range is considered to be a "cool fermentation"?
Which styles of wines are produced at this fermentation temperature?
- 12-16C
| - fresh fruity white wines
52
What temperature range is considered to be a "mid-range fermentation"?
Which styles of wines are produced at this fermentation temperature?
- 17 - 25C
- fruity early-drinking reds
- less fruity whites at the lower end
- barrel fermented whites at the higher end
53
What temperature range is considered to be a "warm fermentation"?
Which styles of wines are produced at this fermentation temperature?
- 26 - 32C
| - more intense flavoured reds - more tannin and colour extraction but less fruity aromas retained.
54
advantages of using stainless steel tanks
- inert and airtight
- easy to clean
- high level of mechanisation is possible
- easy to control the fermentation temperature
- come in a variety of shape and sizes
55
Advantages of using concrete vessels
- high thermal inertia
- neutral and airtight
- can be build in-situ, according to the winery's needs
56
Adv. and disadvantages of fermenting wines in wooden vessels
adv.
-retains heat
- gradual and controlled O2 exposure
-better integration of oak during maturation
dis.
- high cost
- difficult to clean, impossible to sanitise, pores my harbour spoilage microorganisms
57
what conditions are necessary to encourage MLF ?
- low total SO2
- moderated pH (3.3 - 3.5)
- Temperature between 18 - 22C
58
ways of preventing MLF
- adding SO2
- chilling the wine under 15C
- sterile filtration
- adding the enzyme lysozyme
59
what is the outcome of Malolactic conversion ?
- part of malic acid is converted to lactic acid
- reduction of acidity and rise in pH
- CO2 is produced
- colour loss in reds
- greater microbiological stability
- modification of flavour - lower fruitiness, more VA, production of diacetyl
60
What are the advantages of carrying out MLF in barrel?
- better integration of flavours
| - use of lees to improve mouthfeel
61
What does the term "co-inoculation" refer to?
- inoculation of yeast and bacteria to carry out AF and MLF at the same time.
- sometimes bacteria is added half-way through AF or just before the end of it
62
what are the benefits of co-inoculation?
- improved retention of fruity aromas
- reduction of production times
- reduction in labour for monitoring two separated processes
- reduction of critical time in which the wine is exposed to spoilage organisms
63
Post fermentation adjustment options
- reduction of alcohol
- acidification and pH adjustment
- tannin addition
64
Ways of removing alcohol after AF
- Reverse osmosis
| - spinning cone
65
What is the common path after AF for young fruity or acidic styles of wine
```
reductive techniques:
- maturation is stainless steel
- kept at low temperature
- vessels blanketed with inert gas
- also likely to be bottled shortly after AF
-
```
66
Benefits of storing the wine in bulk
- more efficient use of store area
- flexibility to sell the wine according to market demand
- extended shelf life for young wines
- option of transporting in bulk to the final market, reducing cost of transportation
67
key factors in the maturation process
- oxygen exposure rate
- type of wood
- yeast lees
- temperature
68
How does temperature affect the maturation process of the wines ?
it determines which reactions take place, and at which rate.
69
Role of Oxygen during maturation
- improves colour stability in red wines
- gradual reduction of primary aromas, and development of tertiary aromas
- polymerisation of tannins and reduction of bitterness
- whites will turn darker, becoming golden and then brown
- reds become paler and turn from ruby to garnet and then tawny
70
how does wine get exposed to oxygen during barrel maturation?
- some O2 is released from the vessel the first month it is filled
- Small amount passes through the gaps between the staves and the pores of the wood
- the wine is most exposed with the bung is removed
71
Why do wooden vessels need to be topped up during maturation?
What factors increase the regularity in which they have to be topped up?
- some water and alcohol impregnate the wood
- then there is further loss as they diffuse to the outside and evaporate
evaporation rate is increased by
- low humidity levels in the atmosphere
- smaller vessels
72
Why does the wine "concentrate" when it is subjected to long maturation periods in barrels?
Because water and alcohol evaporate through the pores of the oak. If humidity levels are low (less than 70%) water is lost at a higher rate, and the final wine will have a higher alcoholic strength.
73
Explain reverse osmosis process to reduce alcohol level of a wine.
- to revert the natural osmosis direction the more concentrated solution is subjected to high pressure.
- carried out in a cross-flow filter
- as the wine passes through, a mixture chiefly composed of water, acetic acid and alcohol is removed.
- alcohol is removed by distillation or another membrane process, and the water blended back to the wine.
74
What are the uses of reverse osmosis in winemaking?
- removing water from must (must concentration)
- removing VA from wine
- removing alcohol from wine
- removing 4-ethylphenol from wine
75
Explain the spinning-cone method of removing alcohol from wine
- consist of a column with 40 upside-down cones, half of them fixed, and half spin.
In a vacuum environment, the cones spin the wine into thin liquid films. Cool vapour will rise from the wine, carrying the volatile compounds.
In the first pass, delicate aromas are extracted, which are condensated to blend back afterwards ("the essence"). The second pass is the one that removes alcohol.
76
How does the size of the wooden vessel affect the wine maturation?
the smaller the vessel, the higher the contact surface to volume ratio. this means that:
- the impact of wood flavour will be higher
- the evaporation rate will be higher
- oxygen exposure rate will be higher
- barrels will be topped up more frequently
- maturation process will be shorter
77
What are the characteristics of American Oak in comparison to European one?
- higher levels of lactones (coconut flavour)
- greater intensity of aromas
- lower level of tannins
- cheaper to produce
78
How does the tightness of the grain of the oak influence in wine maturation process?
the tighter the grain the slower the extraction of compounds
| it can also alter which compounds are extracted
79
What are the natural factors that affect how tight the grain of the oak is?
- the slower the growth of the tree, the tighter the grain
| - continental climates promote a slower tree growth
80
What does the term "seasoning" in oak barrel production context mean?
- process of 2-3 years that reduces the humidity of the wood, reduces bitterness, increases aroma compounds
81
What is the level of toasting of a barrel? What is their effect?
- the temperature and time that the wood is exposed to fire heat
- it is categorised as: light, medium and heavy
- toasting transforms tannins and aromas, giving notes of spice, caramel, roasted nuts and smoke.
82
Why does barrel maturation increase the cost of production?
- oak is expensive
- if barriques are small, a large amount of them is needed.
- it is labour intensive - barrels need to be monitored individually, and operations are carried our manually
- meticulous cleaning is essential
- it extends the production time - cashflow is slow.
- they take up a lot of winery space
- temperature and humidity of the store room needs to be controlled
83
What are the oak alternatives to barrel?
- oak staves
| - oak chips
84
What is micro-oxygenation?
bubbling O2 gradually through the wine to simulate the oxidative reactions that naturally occur when maturing wine in wooden vessels.
85
How is the dose of O2 used during micro-oxygenation measured?
in mg/L per month.
86
What are the benefits of applying micro-oxygenation?
- tannin polymerisation, reduction of bitterness
- increased colour stability
- improve texture
- removal of unripe flavours
- the rate of O2 can be tightly controlled
- the effects of oak maturation are achieved in a shorter period of time.
- investment in equipment is a one-off payment
- less labour intensive
87
What does "battonage" refer to?
the stirring of the lees to increase contact surface with the wine
88
what is the impact of battonage in wine maturation?
- increased O2 exposure
- enhanced yeast flavours
- reduced fruity characteristics
89
What are the effect of ageing the wines on their lees?
- improved texture "creamy"
- more fullness of body
- yeasty flavours
- reduced astringency
- modification of oak flavours
- protein stabilisation
- protection from oxidation
- if it is not closely monitored - production of reductive sulfur compounds
90
What does the term autolysis refer to?
to the process through which yeast cells die and break down, releasing compounds that will integrate into wine and modify its flavour and texture
91
What are the lees?
the term describes the sediment that settle at the bottom of the vessel. This includes dead yeast, grape particles, precipitated tannins, and other insoluble compounds.
92
What is the difference between gross lees and fine lees?
- Gross lees: the sediment that settle within 24 hours after fermentation . they are removed with the first racking
- fine lees: smaller particles that take longer to settle, subsequent racking are carried out to control its levels
93
What is racking?
Is the action of transferring the wine from one vessel to another, mainly with aim of removing sediments (lees, tartrates, etc).
94
how is racking carried out?
The wine is removed through a valve near the bottom of the vessel, but above the top of the sediment, and pumped or poured into a new, clean vessel.
95
Factors that affect the number of rackings
- maturation length
- whether the wine is matured on lees or not
- level of O2 exposure desired
96
reasons for blending wine
- Balance
- complexity
- volume
- consistency
- style
- minimise faults
- price
97
What are the different origins of oak used in winemaking?
- North America
- France
- Slavonia
- Hungary
- Russia
98
Options when clarifying wine
- sedimentation
- centrifugation
- Fining
- filtration
99
Benefits of clarifying wine with the centrifugation process
- Quick process
- it can replace depth filtration
- allows early bottling
- effective with wines with a lot of matter in suspension
100
Explain the concept of fining
It is an intervention in which a fining agent is added to speed up the precipitation of suspended material in wine. It clarifies the wine and stabilises it, as it removes unstable colloids that may otherwise case hazes later in the bottle. It can also remove unwanted components such as harsh tannins or dark colourants in white wine.
101
How does the fining agents work chemically?
Th unstable colloids to be removed are separated from each other as they hold the same electrostatic charge. The fining agent has to hold the opposite charge, and will therefore attract those colloids.
The attracted components will form larger particles that will precipitate and will be easier to remove.
102
What does "over-fining" refer to?
| How is it avoided?
Term that describes the excessive use of a fining agent. As a result, many agents may remove desirable wine components or make the wine more unstable.
Prior trials are carried out in the laboratory to determine the minimum effective amount.
103
Name the different fining agents used in winemaking
- Bentonite
- gelatine
- albumin
- casein
- isinglass
- Tannins
- vegetable proteins
- Silica Soil
- PVPP
- activated charcoal
104
Name the different types of filters, and examples of them
- Depth filtration - earth filter, sheet filter
| - Surface filter - cartridge filter, crossflow filter
105
What does the term "stabilisation" refer to?
it refers to several winemaking interventions carried out to avoid unwanted hazes, deposits, and rapid changes in the wine (browning) after bottling.
Fining, filtering, and tartrate stability contribute to both clarifying and stabilising the wines.
106
Name the options for tartrate stability
- Cold stabilisation
- contact method
- Ion exchange
- Electrodialysis
- Metatartaric acid
- Mannoproteins
- Carboxymethylcellulose (CMC)
107
What does "DMDC" refer to?
| What is it used for?
- Dimethyl dicarbonate - Velcorin
| - it inactivates Brettanomyces
108
What is bentonite? Explain its use in winemaking
- It is a type of clay, and aluminium-silicate one that i s formed from volcanic ash. It is obtained in the USA
- It is a fining agent used for clarifying and protein stabilise the wine, and for clarifying musts.
- It is strongly negatively charged, thus it has high absorption strength, forming voluminous deposits. It is very efficient with unstable colloids but has minimal effect on texture and flavour. Though it reduces colour in reds.
109
Explain the use of albumin
It is a clarifying agent extracted from egg whites. It can be used in it fresh or powdered form. It is used for both, reds and whites.
It is very efficient removing harsh tannins, but has a gentle effect in the wine.
110
Key factor about Gelatine use in winemaking
- It is a protein collagen extracted from pork
- it can be used in wine and must
- removes bitterness and astringency in reds
- removes browning in whites
- it easily over-fines - protein haze and removing flavour
111
Define Filtration
It is a physical separation technique used to eliminate solids from a suspension. The liquid is passed through a filter medium, consisting of porous layers that trap solid particles, thus, making the wine clear.
112
Explain depth filtration
The solid particles are removed within the structure of the filter medium itself, which has to be many times thicker than the size of the particles being removed. It works because the liquid has to ravel through tortuous pathways, and the particles will be trapped somewhere in the material
113
Explain Surface filtration
| What other name is it given?
- Absolute filtration
- The channels of the filter medium are smaller than the particles to be removed. Therefore, they get trapped at the surface of the filter.
114
explain the cold stabilisation process
The wine is cooled just above the freezing point (-4C for a 12ABV wine, up to -8C for fortified) and stored up to 8 days. This reduces the tartrate solubility, therefore, crystals will form and condensate.
- huge amount of energy use
- low surface contact
115
Explain the contact tartrate stabilisation process
the wine is brought in contact with micro-crystals of K bitartrate, which act as a nucleus, triggering further crystallisation.
The wine is cooled to 0C, added with 4 g/L of micro-crystals, and stirred vigorously to keep them in suspension
116
how does the cross-filter work? What other name can it receive ?
- tangential filter
- the wine runs through a tube under pressure, the walls of which are made of the filtering membrane. Thus as it is filtered, it cleans itself.
117
What are "Cartridge Filters"?
A type of surface filter which uses very small filter pores, often less than one micron. They are normally used just before bottling to ensure the wine is completely clear and stable. It can be used for sterile filtration.
As the pores are small: the wine must be pre-filtered. It can easily get blocked.
118
Why do tartrate crystals appear after bottle age and not before?
Because the colloids in wine act as protective agents against crystallisation and precipitation. After some time in bottle, the colloids denature and lose their protective effect.
119
Explain the use of mannoproteins as an additive
- they are use for make the wine tartrate stable
- they act as protective colloids against crystallisation, with very good stability in wine
- they are used in a powdered form, which must be added the day before bottling
120
Explain the Electrodialysis process
- it uses the properties of selective membranes that allow the passage of tartrate ions under the influence of an electric charge.
- both types of tartrates are removed
- does not require previous fining
- high-cost method
121
What does CMC stand for?
| How is it used in winemaking?
- Carboxymethylcellulose - cellulose extracted from wood
- it prevents tartrates from from developing to a visible size.
- It is widely used with inexpensive white and rose, but not suitable for reds as it reacts with tannins causing hazes.
- keeps wines stable for a few years
122
What is sparging?
a process that flushes inert gas to remove dissolve oxygen from wine
generally carried out prior to bottling
123
What are the effects of skin contact in white wines?
- more extraction of aroma/flavour compounds and small level of tannins
- - enhances the characteristics of aromatic varieties
- slight tannin extraction can improve texture
124
What are the benefits of pressing whole bunches in still white wine production?
It is the gentlest way of extracting the juice. Musts obtained are delicate, with low content of solid matter and colour. It also reduces oxidation to the maximum
125
What are the drawbacks of pressing whole bunches in still white wine production?
- slow process, as it can only be carried out in small batches (the stems occupy a lot of press space)
- hand harvesting is required
- more expensive
126
What are the options for macerate red grapes before fermentation?
- cold soak
- Thermovinification
- Flash détente
127
What is "the cap"?
it is the accumulation of grape skins at the top of the fermented that are raised by the CO2 bubbles.
128
Why does the cap need to be managed?
- its formation reduces the surface contact with the fermenting must (little extraction)
- the must directly in contact gets quickly saturated - stopping extraction
- the top of the cap can dry out and be exposed to spoilage bacteria
129
Additional benefits of cap management (other than aiding skin extraction)
- integration of O2 - aids development of yeast and avoids reductive sulphur compounds
- it can help to release heat
130
name the options for cap management
- punching down
- pumping over
- rack and return
- rotary fermenter
- ganimede tanks
131
explain cold soaking
- the wine is chilled to 4-10C and it is left to macerate with the skins for 3-7 days
- skins are normally punched down
- gentle technique, extracts mainly colour
132
What are the effects of macerating with heat previous to the AF?
- It aids and accelerate pre-ferm. maceration. extracting high levels of colour but little tannins.
- most wines will then be fermented without the skins, occupying less tank space and avoiding the need to manage the cap (reduced costs)
- colour instability - no tannins to bind with anthocyanins
- enhanced fruitiness
- denatures oxidative enzymes on grapes that have been affected by grey rot
133
How is thermovinification carried out?
- must is heated to 50-60C and left to macerate for minutes or even hours. the higher the temperature the shorter the maceration
134
How is Flash détente carried out? What are its benefits?
destemmed uncrushed grapes are quickly heated to 85-90C and instantly cooled down under vacuum. The cells of the skins burst and quickly colour extraction results.
It reduces the risk of developing cooked flavours and helps to reduce smoke taint
135
Why are some wines cooled by the end of fermentation ?
to slow down the extraction of harsher tannins by the rising alcohol level
136
What is "pigeage"? How is it carried out? what are its results?
- French term for Punching down
- a plunger is used to submerge the cap in the must
- can be carried out by hand or mechanised
- It is only viable in small open fermenters
- it results in gentle extraction
- carried out in small batches of high-quality wine
137
What is "remontage"? How is it carried out? what are its results?
- another name for pumping over
- the wine from the bottom of the fermenter is pumped to the top and sprayed over the skins.
- It can be done anaerobically in closed vessels and attaching the hose to a tap at the top.
- can me programmed
- can be carried out in all size of vessels and used for all types of wine styles and price ranges
- fairy gentle extraction
138
How do rotary fermenters work? What are its results?
- They are horizontal closed tanks that rotate and have an inner blade that breaks the cap.
- very extractive
- wines high high levels of colour and tannin
- fully automated - low labour requirements
- commonly used for high-volume inexpensive wines.
139
explain rack and return and its impact on wine
all the fermenting wine is racked off to another tank and then it is flushed back over the skins.
Highly extractive method. Efficient in releasing heat and it dissolves high levels of oxygen.
- It can only be done 1-3 times
140
How do Ganimede Tanks work?
- they reuse the CO2 created by the fermentation to build pressure and break the cap when a series of by passes are opened. Alternatively, air can be used to increase O2 exposure.
- fully automated, and can break the cap quickly and very regularly
- relatively extracitve
141
What are the results of carbonic maceration?
- fall in acidity
- high levels of colour extracion
- low levels of tannins
- production of strawberyy, kirsch, cinnamon and even banana and chewing gum distinctive flavours.
- higher production of glycerol
142
How is carbonic maceration carried out?
- whole bunches are placed in a tank filled with CO2
- anaerobic conditions trigger an enzymatic fermentation that produces 1.5-2% of alcohol
- Polyphenols migrate from the skin to the pulp of the grapes. Extra AA are liberated
- berries die when they reach 2 % alcohol
- wine is racked off from its skins and traditional AF is completed with inoculated yeasts
143
Options when pressing red wines
- At the end of AF
- after a post fermentation maceration
- just before the end of AF (normally to finish it in barrel
- in carbonic maceration - when must reaches 2% ABV
144
Option for Rosé wine production
- short maceration
- direct pressing
- blending
- Saignée
145
What does the term "vin gris" refer to?
Rosé wines made by direct pressing
146
Explain direct pressing technique for producing rosé wines
- either whole bunches or destemmed and crushed grapes are directly placed in the press to extract the juice. The press is normally flushed with inert gas. The must is then treated as a white wine
- it produces the palest and more delicate rosés
- co-pressing with white grapes is also an option
147
Why would a winemaker co-press or co-ferment with white grapes in rosé wine production?
to reduce colour and increase acidity
| it will also modify the flavour/aroma profile of the wine
148
What are the results of producing a rosé wine by blending?
- final wine has a high white wine character
- high degree of control over colour and style
- easy to make and cheap
149
What does the term "saignée" refer to?
in French - "bleeding"
Refers to the wines made from juice that bleeds from red must macerating with the skins
it is usually a by-product of red wine production
150
How are those rosé wines produced by maceration in comparison to direct pressing?
they are deeper in colour and more pronounced in flavour
151
name the faults that can affect the wine
- cloudiness and hazes
- re-fermentation in bottle
- cork taint
- oxidation
- brettanomyces
- volatile acidity
- light strike
- reduction
152
what does OTR stand for?
Oxygen Transmission Rate
153
What elements affect the total package oxygen?
- OTR
- The Dissolved Oxygen in the wine
- the O2 in the headspace
- the amount of O2 in the cork or other closure
154
What are the options to sterilise the wine when bottling?
- Thermotic or hot bottling
- tunnel pasteurisation
- Flash Pasteurisation
155
Name the different technical corks available
- Colmated Cork
- Agglomerated cork
- One-plus-one
- Diam stopper
156
What are the options when choosing packaging materials?
- Glass
- Bag-in-Box
- cans
- Bricks
- PET bottles
- Pouch
157
What are the benefits of the natural cork?
- biodegradable
- elastic - it can be compressed and will quickly regain its original shape
- anti-slip property
- it comes from a natural renewable source
- good oxygen barrier with variable OTR
158
What are the causes of hazes in bottle ?
- poor filtering of the wine - too much pressure in depth filters, wrong pore size.
- unsuccessful fining (protein haze) - wrong type of agent, over-fining.
- activity of bacteria or yeast - inadequate filtering + low SO2 levels
159
What are the tartrates?
- tartaric salt crystals that can appear at the bottom of the bottle
160
What are the causes of oxidation faults? And its consequences?
Causes
- excessive O2 exposure during winemaking process.
- excessive O2 exposure in bottle due to faulty bottling, poor quality closures or for keeping the wine for longer than the appropriate for its style.
Consequences
- premature browning
- loss of primary fruit aromas
- vinegary smell
161
What are the causes of VA fault? Ans its effect?
- Cause: activity of acetic acid bacteria, inadequate levels of SO2 and excessive O2 exposure.
- Effect: pungent nail varnish or vinegary smell
162
Causes of Reductive taint
- yeast under stress due to low nutrient levels during AF
- complete exclusion of O2 exposure during ageing of the wine, especially when on its lees
- complete exclusion of O2 exposure combined with high SO2 levels during bottle ageing.
163
Measures to avoid the attack of Brettanomyces
- Excellent winery hygiene
- maintaining effective SO2 levels
- keeping pH levels low
- shortening the time period between AF and MLF to add SO2 as soon as possible
164
Management options when wines have been infected with Brettanomyces
- sterile filtration + addition of SO2
- use of DMDC (Velcorin) which inactivates the yeast.
- reverse osmosis to reduce the aromatic components it produces
- blend the wine with other sound batches to reduce its impact on the final wine
165
causes of light strike
- exposure to UV radiation or artificial fluorescent lighting
- packing the wine is clear glass bottles increases the risk
166
Explain Thermotic bottling
The wine is heated to 54C them bottled, corked, packed into cases and put aside in the warehouse to slowly cool down. The yeast and bacteria are killed by virtue of the long period at elevated temperature, rather the temperature itself
167
Explain Tunnel Pasteurisation
The wine is bottled as normal, and then the bottles are passes through a large heat tunnel where they are raised to 82C for about 15 minutes by spraying hot water. At the end of the tunnel they are sprayed with cold water to quickly cool them down.
168
Explain Flash Pasteurisation
The wine is heated to around 75C for about 30 seconds and quickly cooled down before it reaches the filter. Then it is bottled. The major drawback is that it can be re-infected during bottling.
169
Advantages of glass bottles for wine packaging
- inert material
- it is impermeable to gas
- inexpensive to manufacture
- can be delivered to the winery in sterile conditions.
- can be recycled without losing quality
- they are the only option for sparkling wine
- they are the best option for age-worthy wines
170
What is the shelf life of the Bag-in-Box?
nine months for a three litre box
171
What does the Bag-in-Box consist of?
- Cardboard box that houses a flexible bag inside
- Bag: two outer layers of high-density polyethylene (HDPE), between which there is a layer of aluminium. The latter one acts as the oxygen barrier, which gives excellent protection when new, but deteriorates with use due to small cracks in the foil when it is flexed (flex cracking)
172
Advantages of the Bag-in-Box
- flexible pour size
- range of sizes available - home and commercial use
- good protection from oxygen after pouring
- easy to store
- low environmental impact
173
What characteristics of the wine must be adjusted when packing it in a Bag-in-Box ?
- higher SO2 level than when packing it in glass
- low dissolved oxygen
- low Carbon Dioxide
- ensure there is no headspace in the bag
174
What is the most important feature of the Brick packaging? how is it achieved?
- it is the only packaging that is truly aseptic.
- The packaging material is sterilised by UV radiation as it passes through the filling machine, the machine is filled with sterile-filtered Nitrogen and the wine itself is sterile filtered.
175
What does the structure of the brick consist of?
Laminate of Polythene, cardboard, a layer of aluminium foil (the O2 barrier) and another layer of polythene to protect the aluminium.
176
How is the wine packed in bricks?
- the package is formed around the liquid
- the material is formed into a tube, the bottom is sealed, the wine piped from above and then the tube is sealed and cut with the desired proportions.
177
What are the most important characteristics of the cans as a wine packaging?
- they are a good option for early-drinking wines
- it is light weight but robust
- easy to open
- impermeable to oxygen
- recyclable
178
What is the cause of cork taint?
- reaction between a penicillium mould in the crevices of the cork and the chlorine-containing chemicals used in the sterilising process held in the past. This reaction produces Trichloranisole (TCA), a substance with a powerful fungal aroma.
179
What measures have been taken to reduce the incidence of tainted corks?
- more careful harvest of the cork bark
- storage of the bark off the ground
- replacement of the chlorine process by peracetic acid and ozone, which eliminate TCA precursors
- clean corks with steam extraction
- use of high-tech (such as gas chromatography) to detect the presence of TCA
180
What is a colmated cork?
a piece of natural cork that has been coated with a mixture of cork dust and latex. This process fill the lenticels creating an impermeable membrane between the cork and the wine, excluding any aromas from the cork reaching the wine.
181
What is an agglomerated cork? what is its major drawback?
- a stopper made by cork granules stuck together with a resin-based glue.
- it is only suitable for short-life wines as the resin disintegrates after a few months in contact with wine.
182
What is a one-plus-one cork?
a disc of natural cork bonded to each end of the agglomerate centre, so that the wine is only in contact with the natural piece of cork.
- it has been designed to overcome the agglomerate cork limitations
183
What is a diam stopper?
Natural cork is grinded into very small particles that allow to separate the elastic fraction (the suberin) from the harder woody particles, which are rejected. The suberin is treated with Diamant process , then washed with CO2 removing any residual TCA. Finally, they are mixed with a plastic polymer, compressed and heated to obtain a uniform, fine-textured stopper.
184
What are the main characteristics of the synthetic closures? name the different types
- made with food-grade plastic with a silicone coating
- the major disadvantage is that they do not have a good oxygen barrier.
- They tend to absorb flavour compounds.
- Types: Moulded closures and extruded closures.
185
What are the different names given to the aluminium screw caps?
- ROTE (Rolled on tamper evident) - Australia
- ROPP (Rolled on Pilfer proof) - UK
- Stelvin (name of a well-known brand)
186
What are the advantages of sealing bottles with screw caps?
- they provide the best oxygen barrier
- they do not cause taint
- do not suffer from quality variation
- do not need any special tool for opening
- are available with three different OTR
187
What do glass stoppers consist of?
- the stop itself is made of glass, and the seal is formed by a PVC plastic ring that sits at the top of the underside of the stopper. To ensure a tight closure it requires especially designed bottles with a smaller inside neck diameter.
