VINIFICATION 🍇 Flashcards
1
Q
Main components in the wine
A
- Water
- Alcohol
- Acids
- Wine aromatics
- Residual sugar
- Glycerol
- Phenolics
2
Q
Approximate percentage of water in the wine
A
85%
3
Q
Major types of alcohol in the wine
A
Ethanol and higher alcohols.
4
Q
Ethanol
A
Formed during fermentation, also known as ethyl alcohol, it’s the predominant alcohol in wine, slightly sweet smell. A sensation of sweetness, bitterness, and oral warmth. It contributes to the fullness of the body and the mouthfeel. Aromas.
5
Q
Consequences of high levels of alcohol in the wine
A
↑ alcohol (> 14.5 abv) ⇨ ↓ wine aromas volatility ↑ bitterness ⇨ fruit concentration is needed to balance
6
Q
Major acids in the wine
A
Tartaric and malic come from the grape (2/3 of the total acidity in a warm climate).
Lactic and acetic are produced in fermentation or malo conversion.
7
Q
What acids improve
A
Acidity improves the structure of the wine, refreshing, in balance with fruit concentration and residual sugar. High acid leaner wine, too high tart taste, no acid flabby taste.
Perception of acidity is related to the residual of sugar (German Riesling).
8
Q
Range of total acidity
A
The sum of all the acids is in the range of 5.5-8.5 g/l.
9
Q
Range of pH
A
The logarithmic scale of measurement for the concentration of the effective acidity of a solution is in the range of 3-4.
10
Q
Consequences of low pH in the wine
A
↑ microbiological stability of wine ↑ effectiveness of SO2 ↑ ageing ability ↑ bright red colour (red wine)
11
Q
Types of wine aromatic compounds
A
- Aromas from the grapes.
- Aromas created by fermentation due to the presence of aroma precursors in grape must.
- Aromas originating from fermentation and its by-products.
- Aromas from other sources.
12
Q
Aromas from the grapes - what they are, examples
A
Aromatic compounds that are found in the grapes.
Methoxypyrazines and rotundone.
13
Q
Methoxypyrazines
A
Aromatic compounds that are found in the grapes. Common in Sauvignon Blanc, grassy and green pepper aroma.
14
Q
Rotundone
A
Aromatic compounds that are found in the grapes. Common in Syrah and Grüner Veltliner, pepper aroma.
15
Q
Aromas created by fermentation due to the presence of aroma precursors in grape must - what they are, examples
A
Compounds that are not in themselves aromatic but are building blocks which become aromatic during fermentation.
Thiols and terpenes.
16
Q
Thiols
A
Aromas created by fermentation due to the presence of aroma precursors in grape must. Released during fermentation, 4MMP gives the box tree aromas in Sauvignon Blanc (break down in presence of oxygen), for example.
17
Q
Terpenes
A
Aromas created by fermentation due to the presence of aroma precursors in grape must. Released during fermentation, fruity and floral aromas, linalool and geraniol give grapey aromas in Muscat, for example.
18
Q
Aromas originating from fermentation and its by-products - what they are, examples
A
Not present in the grape, but created from fermentation and its by-products (lees).
Esters, acetaldehyde, and diacetyl.
Yeast can produce reductive sulfur compounds during fermentation and lees ageing.
19
Q
Esters
A
Aromas compounds formed by the reaction of certain acids and alcohols, the majority created through the action of yeasts in the fermentation process, fresh and fruity aromas (aroma profile of young wines), unstable and breakdown a few months after fermentation, isoamyl acetate gives banana aroma if high concentration, for example.
20
Q
Acetaldehyde
A
Aromas compounds due to oxidation of ethanol, it masks fresh fruit aromas, stale smell (regarded as a fault in most wines), an important component of the distinctive smell of Fino Sherry.
21
Q
Diacetyl
A
Aromas compounds produced during fermentation (malo conversion), buttery aroma.
22
Q
Aromas from other sources - what they are, examples
A
Aromas compounds derived from other sources. Intense scientific research to detect the origin, interaction between aromatic and non-aromatic compounds.
Vanillin and eucalyptol.
23
Q
Vanillin
A
Aromatic compound that can be derived by wine ageing in new oak barrel.
24
Q
Eucalyptol
A
Aromatic compound that can be volatized from eucalyptus trees by heat and absorbed in the waxy layer of the grape skins in nearby vines.
25
What residual sugars improve
Sweetness and body.
26
EU classification for sugars in still wines
- Dry/Sec/Trocken – < 4 g/l or < 9 g/l with the difference of acidity not more than 2 g;
- Medium dry/Demi-Sec/Halbtrocken – between 4-12 g/l or < 18g/l with the difference of acidity not more than 10 g;
- Medium or Medium sweet/Moelleux/Lieblich - between 12-45 g/l;
- Sweet/Doux/Süss - > 45 g/l.
27
Glycerol
3rd abundant part of wine (dry wines).
It derives from the sugar in grapes. High levels in wines made from botrytis-affected grapes (Tokaji) or by carbonic maceration (Beaujolais).
It gives smoothness to the texture and the perception of the fullness of the body. Sweet taste.
28
Phenolics - what they are, examples
Group of compounds that are in the skins, stems, and seeds.
| Anthocyanins and tannins.
29
Anthocyanins
Colour pigments responsible for the red colour of red and rosé wines. Not very stable as single molecules (they need to combine with tannins by oxygen), colour can be altered or lost during winemaking process (lees ageing or addition of SO2). They are soluble in both the must and wine.
30
Key points for conventional winemaking
- Louis Pasteur identified bacteria and yeasts in 1860 to convert grape must into wine.
- Principles of:
1. temperature control;
2. use of additives and/or processing aids of many types (sugar, SO2, cultured yeast, fining agents);
3. manipulations (from simple pressing and filtration to high technology).
- Manipulations and the use of additive are dictated by the style, price point required, health and ripeness of the grapes, preferences of the winemaker.
31
Key points for organic winemaking
- Wines with certified organically-grown grapes and restricted rules during winemaking process.
- Ecocert gives a list of allowed and not allowed operations.
- The rules vary across countries with regard to the addition of SO2. Regulated amount in EU, no addition in the USA (“wines made from organic grapes” category allows the addition of SO2).
- Certification increase the cost, issued either by associations (Organic Winegrowers New Zealand), or determined at country level (US Department of Agriculture) or by the EU.
32
Key points for biodynamic winemaking
- Wines with biodynamically grown grapes.
- Demeter is the main certifying association. Each country has a different standard. In the UK, natural yeasts are encouraged, but organic or, if unavailable, commercial yeasts can be used. In the USA, natural yeasts must be used, but certain classes of commercial yeast can be used if a ferment has stuck and then only on a case-by-case basis.
- Biodynamic wines are more expressive of terroir (for the winemakers).
- Certification increase the cost.
33
Key points for natural winemaking
- Winemakers reject many modern interventions in favour of artisan practices from the past (nothing added, nothing removed).
- Wines with the fewest possible manipulations, ambient yeasts, minimum quantity of SO2.
- No certifying body, but some associations publish their approach/standards (ViniVeri and L’Association des Vins Naturel).
- No restrictions on the grapes.
- Small batch and mid to premium prices.
- Natural wines are more expressive of terroir (for the winemakers).
34
Meaning of reductive/protective winemaking
The practice of minimising oxygen exposure during the winemaking processes.
35
How to limit the effects of oxygen in winemaking
- avoiding ullage in vessels (vessels have to be filled up to the top, evaporation in wooden vessels);
- use of inert gases (nitrogen, carbon dioxide, argon);
- addition of sulfur dioxide;
- use of impermeable containers (stainless steel and thick concrete vessels are impermeable to oxygen, wooden vessels allow gentle ingress of oxygen, screwcap can minimise exposure to oxygen);
- cool and constant temperatures (cool temperatures slow the rate of oxidation reactions).
36
Ullage - what it is
The headspace of air between the wine and the top of the container.
37
Examples of inert gases
Nitrogen, carbon dioxide, argon.
38
Hyperoxidation - what it is, pros/cons
Exposition of the must to large quantities of oxygen before fermentation. Compounds oxidise and turn the must brown (precipitation during fermentation and the wine returns to its normal colour).
The main aim is to produce wines that are more stable against oxidation after fermentation. It removes bitter compounds, can destroy some of the most volatile aroma compounds (no for aromatic grape varieties), better suited to neutral grape varieties such as Chardonnay (can destroy thiols and methoxypyrazines of Sauvignon Blanc).
No high costs for the equipment, but more labour.
39
How to increase oxygen exposure
- cap management techniques for red wines;
- small wooden barrels;
- increase the number of rackings or amount of lees stirring during ageing;
- allowing ullage without inert gases;
- pumping oxygen through the must.
40
Relationship between oxygen and yeast
Oxygen is required at the start of fermentation to promote the growth of a healthy yeast population.
41
Consequences of too many oxidation reactions
No good for the production of fresh and fruity wines. Aroma compounds that give fruity style break down in the presence of oxygen (thiols). Oxidation reactions can produce unwanted aromas (acetaldehyde), darker colour (red wines have phenolic compounds, so they have to absorb more oxygen).
42
Oxidation reactions - what they are
The reactions oxygen does take part in create products that then go on to react with many must and wine compounds.
43
Unwanted effects due to oxygen exposure
It can provide a more favourable environment for spoilage microbes (acetic acid bacteria and Brettanomyces).
44
Main functions of sulfur dioxide
- Anti-oxidant – it reacts with the products of oxidation reactions and it inhibits oxidative enzymes.
- Anti-microbial – no yeast and bacteria (different tolerance).
45
EU limits for sulfur dioxide
160 mg/l red wines
| 210 mg/l white wines
46
The minimum amount of sulfur dioxide to declare on the label
10 mg/l
47
When is sulfur dioxide usually added during the winemaking process?
Added usually after picking or when the grapes reach the winery, at bottling.
48
Bound SO2
When SO2 is added to must or wine, it dissolves and reacts with compounds; ineffective against oxidation and microbes.
49
Free SO2
It’s unbound to compounds; effective against oxidation and microbes.
50
The most effective moments to add sulfur dioxide
When the grapes are crushed, after malo, and at bottling.
51
Consequences of high levels of SO2
High levels of SO2 are toxic and they can dull wine aromas/flavours and sometimes cause the wine to taste harsh.
52
Which forms can have SO2
Gas, liquid or solid – sulfur dioxide, potassium metabisulfite or potassium bisulfite.
53
Ways of transport the grapes after hand harvest
Grapes are in small crates:
- grapes stay in small crates (high quality, small-scale grape growing, minimal crushing, limited oxidation and microbial spoilage);
- grapes are tipped into larger hoppers such as large bins (possibility of crushing, adding of SO2 in the form of potassium metabisulfite).
54
Way of transport the grapes after machine harvest
Usually larger estates. Grapes are destemmed, transport in large containers, release of juice, adding of SO2.
55
How to preserve grapes during transportation from vineyard to cellar
- night harvest;
- addition of SO2;
- cold storage;
- sanitising harvesting equipment/bins.
56
Key operations during the grape reception
- Chilling.
- Sorting.
- Destemming.
- Crushing.
57
Chilling - what it is, pros/cons
During grape reception phase by a refrigeration unit, heat exchanger if fluid. Warm temperatures increase the oxidation and microbial spoilage, costs for equipment and energy, useful to preserve fruity aromas, takes time.
58
Sorting - what it is, pros/cons
During grape reception phase by table and optical sorting, otherwise during harvest. It depends on the ripeness and health of the fruit arriving at the winery, the intended final wine quality and price, carried out in the vineyard, physical state of the grapes; cost is related to the vintage.
59
Destemming - what it is, pros/cons
During grape reception phase. It’s common except for red wine fermentations with whole bunch (Pinot Noir in Burgundy or Sonoma), carbonic maceration (Gamay in Beaujolais), whole bunch pressing for some white wine (high-quality sparkling wine); series of blades within a rotating drum that remove the grapes from the stems or harvest by machine; stems contain tannins.
60
Crushing - what it is, pros/cons
During grape reception phase. Application of sufficient pressure to the grapes to break the skins and release the juice, making it available for fermentation; gentle, combo destemming-crushing.
61
Must - what it is
It's the mixture of grape juice, pulp, skins, seeds that comes from the crusher.
62
MOG
Matter other than grapes, during sorting, such as leaves, twigs, insects.
63
Pressing - what it is, types
```
It’s the separation of the juice or wine from the skins and seeds. In red winemaking, the grapes are typically crushed before fermentation and pressed after the desired number of days on the skins or at the end of fermentation.
Four types:
- Pneumatic press.
- Basket press.
- Horizontal screw press.
- Continuous press.
```
64
Types of presses
- Pneumatic presses.
- Basket press.
- Horizontal screw press.
- Continuous press.
65
Pneumatic press - what it is, pros/cons
The most popular type (air bag presses). Cylindrical cage with a bladder that runs down the side or middle of it, grapes are loaded into the tank, the other side is filled with air and, as the bladder inflates, the grapes are pushed against grates, separating the juice from the skins. Programmable, possibility of inert gas, initial investment (medium to large-scale wineries).
66
Basket press - what it is, pros/cons
A basket is filled with grapes and pressure is applied from above, the juice runs through gaps in the side of the basket and is collected by a tray at the bottom of the press. Small press load, more labour, no possibility of inert gas.
67
Horizontal screw press - what it is, pros/cons
Similar to basket mounted horizontally above a rectangular draining tray. Less gentle, batch processing (clean after pressing).
68
Continuous press - what it is, pros/cons
Continue loading (screw mechanism), less gentle, for cheap wines.
69
Major must adjustments
- Enrichment.
- Reducing alcohol.
- Acidification.
- Deacidification.
70
Enrichment - what it is, pros/cons
Must adjustment. More sugar to have more alcohol: adding dry sugar (chaptalisation), grape must, RCGM, removing water like reverse osmosis (expensive, for high volumes), vacuum extraction (expensive, for high volumes), cryoextraction (freezing the must/wine and removing ice from it, less cost). In the EU chaptalisation is allowed within limits in the cooler parts of Europe. Warmer areas can add grape concentrate or RCGM (limits).
71
Potential alcohol
The amount of alcohol that would be created by fermenting all the naturally-occurring sugar in the must into alcohol.
72
The best time in which sugar is added into the must
When fermentation is underway because the yeasts are already active and can therefore cope better with the additional sugar in the must.
73
Reducing alcohol - what it is, pros/cons
Must adjustment. Adding water to the grape must in warm or hot regions, aromas/flavours are diluted (law, California). Possibility to remove alcohol from the wine in post-fermentation adjustments.
74
Acidification - what it is, pros/cons
Must adjustment. Only in the warmest areas by addition of tartaric acid, citric acid (no EU), malic acid (not common), lactic acid (after malo). Before (preferred, better integration), during or after fermentation. Adjustments are related to the climate (deacidification in the coolest zone, acidification in the warmest, both in the moderate-climate zone). In the EU, no possibility to chaptalize and acidify must at the same time.
75
The best time to apply acidification
Before fermentation to benefit from the effects of a lower pH and better integration. Otherwise during or after fermentation. Some winemaking operations (malo or tartrate stabilisation) affect total acidity and pH.
76
Deacidification - what it is, pros/cons
Must adjustment. Only in the coolest areas (grapes are picked not fully ripen) by calcium carbonate (chalk) or potassium carbonate, ion exchange (cost). Formation and precipitation of tartrates.
77
Alcoholic fermentation - what it is
Conversion of the sugar into ethanol and carbon dioxide carried out by yeast in the absence of oxygen. This conversion produces also heat.
78
Yeasts - what they are, right conditions, consequences of their action
Group of microscopic fungi that convert sugar into alcohol and affect aroma/flavour. Initially, yeast needs oxygen to multiply quickly, then they switch to fermentation.
Right conditions: viable temperature range, yeast nutrients (nitrogen otherwise stuck ferment and rotten egg smells, diammonium phosphate or thiamine), no oxygen.
Consequences: production of alcohol, carbon dioxide, heat, volatile acidity, SO2, wine aromatics (from aroma precursors such as thiols and many terpenes, created by yeast such as esters), glycerol. Some species or strains may also produce detectable levels of undesirable reductive sulfur compounds and acetaldehyde.
79
Saccharomyces cerevisiae
It's the most common yeast, good for high acidity and high alcohol, resistant to SO2, musts to dryness.
80
Saccharomyces bayanus
Used for must with high potential alcohol or for re-fermenting sparkling wine.
81
Main types of yeasts
Ambient yeast and cultured yeast.
82
Ambient yeast - what it is, pros/cons
Also called wild yeast, present in the vineyard and in the winery, range of yeast species (Kloechera and Candida), most of which will die out as the alcohol rises past 5%.
✅ add complexity, free, terroir idea, marketing
❌ slow start of fermentation (volatile acidity, spoilage yeasts, bacteria, off-flavours), long fermentation or even stuck, no consistent product
83
Cultured yeast - what it is, pros/cons
Also called selected or commercial yeast, selected in a laboratory and then grown in volumes suitable for sale, often single strains of Saccharomyces cerevisiae, cool down the must or add SO2 to kill wild yeast before adding cultured yeast.
✅ fast fermentation, low levels of volatile, less danger from spoilage yeasts and bacteria, consistent product, large choice to influence the style
❌ industrial wine, cost
84
The temperature at which there is the possibility to have stuck fermentation
Above 35°C.
85
Range of temperatures fermentation and relative consequences in the wine style
- Cool (12-16°C) – retention of fruity aroma and flavour; ideal for fresher, fruiter white wines and rosé.
- Mid-range (17-25°C) – less fruity white wines, barrel-fermented white wines, low tannin extraction, easy-drinking fruity red wines.
- Warm (26-32°C) – maximum extraction of tannins and colour, loss of fruity aromas; ideal for powerful red wines.
86
Factors that temperature influences during fermentation
It determines the speed of fermentation and defines the wine style.
87
Ways to manage the temperature during fermentation
Temperature control by specific vessels or pumping over/délestage (release heat).
88
Types of fermentation vessels
- Stainless steel.
- Concrete.
- Wood.
- Plastic.
- Terracotta.
89
Stainless steel vessel for fermentation - pros/cons
Easy to clean, different sizes, temperature control, oxygen protection, possibility of mechanisation, initial cost.
90
Concrete vessel for fermentation - pros/cons
Inexpensive in the last century (large scale), high thermal inertia, auto currents (egg), expensive (egg-shaped).
91
Wood vessel for fermentation - pros/cons
Retains heat well, oxygen exchange, hard to clean, initially expensive, then inexpensive over the long term.
92
Plastic vessel for fermentation - pros/cons
Light, versatile, useful for small-batch fermentations, permeable to oxygen, no temperature control.
93
Terracotta vessel for fermentation - pros/cons
Historic use, small-scale production.
94
Malo fermentation - what it is, when it happens, how to encourage, how to inhibit, effects, where it happens
From malic acid to lactic acid and carbon dioxide (heat).
When: After alcoholic fermentation and occasionally during it (increase fruit characteristics and reduce production costs).
How to encourage: 18-22°C, moderate pH (3.3-3.5), low SO2, adding cultured lactic acid bacteria.
How to inhibit: <15°C, low pH, moderate SO2, use of enzyme lysozyme, move the wine to another part of the winery to avoid the spread of lactic acid bacteria, filtration of lactic acid bacteria.
Effects:
- reduction in acidity and rise in pH – lactic acid is weaker than malic acid, softer and smoother wine;
- some colour loss in red wines – problem for very pale red wines;
- greater microbial stability – prevention that malo spontaneously happens;
- modification of the flavour – buttery notes and increment of volatile acidity.
Where: usually malo in barrels, so ability to be able to stir the lees at the same time and better integration of the flavours, a lot of work (different temperatures).
95
How to encourage malo fermentation
18-22°C, moderate pH (3.3-3.5), low SO2, adding cultured lactic acid bacteria.
96
How to inhibit malo fermentation
<15°C, low pH, moderate SO2, use of enzyme lysozyme, move the wine to another part of the winery to avoid the spread of lactic acid bacteria, filtration of lactic acid bacteria.
97
Effects of malo fermentation
- reduction in acidity and rise in pH – lactic acid is weaker than malic acid, softer and smoother wine;
- some colour loss in red wines – problem for very pale red wines;
- greater microbial stability – prevention that malo spontaneously happens;
- modification of the flavour – buttery notes and increment of volatile acidity.
98
Post-fermentation adjustments
- Acidity.
- pH.
- Removal of alcohol.
- Colour.
99
Removal of alcohol (post-fermentation adjustments) - what it is, types
It's applied to produce a reduced alcohol wine or to adjust the level of alcohol marginally. Adding water is the simplest solution (law) but reduce the intensity of flavour.
- Reverse osmosis – cross-flow filtration that removes a flavourless permeate of alcohol and water, which can be distilled to remove the alcohol. The permeate is then blended back to recreate the wine. Cost (rented or bought).
- Spinning cone – extraction of volatile aroma compounds and then alcohol removal. The flavour components are then blended back of the desired alcohol level. Only for large volumes of wine.
100
Reverse osmosis - what it is, pros/cons
Removal of alcohol (post-fermentation adjustments). Cross-flow filtration that removes a flavourless permeate of alcohol and water, which can be distilled to remove the alcohol. The permeate is then blended back to recreate the wine. Cost (rented or bought).
101
Spinning cone - what it is, pros/cons
Removal of alcohol (post-fermentation adjustments). Extraction of volatile aroma compounds and then alcohol removal. The flavour components are then blended back of the desired alcohol level. Only for large volumes of wine.
102
Colour (post-fermentation adjustments) - what it is
Reduction by fining the wine or enhancing by adding very small amounts of the grape-derived colouring agent (MegaPurple). Not allowed in some regions (Douro Valley).
103
Elements that influence the style and quality of wine during the maturation process
Oxygen, new wood, and yeast lees.
104
Effects of oxygen during the maturation process
- A gradual reduction in many primary aromas and development of tertiary aromas. If the wine has a structure suitable for extended ageing, quality may improve otherwise reduction.
- Influence on the colour. White wines become darker. Greater colour stability and intensity for young red wines (anthocyanins bind with tannins, which protect anthocyanins from being adsorbed by yeast lees or bleached by SO2 additions – Pinot Noir becomes paler and browner).
- Softening of tannins in red wines.
105
Factors that influence the speed of oxidation
The amount of oxygen exposure, the compounds in the wine and temperature (warm increases the speed).
106
How the oxygenation happens by the wooden vessels
Wooden vessels are the traditional method of gaining slow and gradual exposure to oxygen. Some oxygen is released from the pores in the vessels (first month) and a very small amount continues to pass through the gaps between the staves and the bung hole. Maximum exposure during any transfer of wine (racking, lees stirring, topping up). Some wine is lost during the maturation process, water and alcohol impregnate the wood, they turn to vapour and diffuse to the air outside the vessel, concentration of other components. Large surface area to volume ratio for small vessels, so more wine is lost, more topping up, more oxygen exposure.
107
Micro-oxygenation - what it is, pros/cons
A cheaper alternative of oxygenation process, gentle and quicker exposure than wooden vessels, use of stainless steel tanks. Used to increase colour stability and intensity, soften tannins, improve texture, and reduce herbaceous flavours. More control, possibility to integrate the influence of the oak with chips or staves. Initially, for inexpensive and mid-priced wine, now also premium and super-premium.
108
Temperatures of storing the wines
Storing at 8-12°C for white wines and 12-16°C for red wines. Warm temperatures speed up the ageing and create undesirable reactions in terms of wine quality.
109
Wine factors influenced by wooden vessels
Wooden vessel influences the wine by oxygenation and various extractable compounds (tannins and aroma compounds) that depend on the age of the vessel, the size of the vessel, the type of the wood, and the production of the vessel.
110
Barrique
Wooden vessel, 225 l, small volume of liquid compared to the surface area of the vessel, greater extraction from the wood and exposure to oxygen, slow return on investment, labour intensive (check the wine in more vessels), expensive, used for mid-price, premium or super-premium wines.
111
Difference between American and European oak
- American oak influences aromas/flavour (coconut) – 300/600€ (sawn).
- European oak (French, Hungarian, Russian or Slavonian) imparts more tannins – 600/1200€ (split to create staves).
112
Contribution of the tightness of the grain in wooden vessels
The tightness of the grain makes the difference in the extraction of compounds. The tightest grains for Russian and Hungarian oak (cool climate, slow growing), so slows down the extraction.
113
Types of wood used for vessels
Oak, chestnut, cherry and acacia.
114
Way of production of the wooden vessel
Seasoned for 2-3 years (lowers humidity of the wood, reduces bitter flavours and increases some aroma compounds); heat the staves to design the shape (transformation of tannins and aroma compounds); level of toasting can be light, medium or heavy (temperature and length of heat exposure) and contributes note of spice, caramel, roasted nuts, char and smoke; barrels from a range of coppers to increase blending options.
115
Cons of barrel maturation
Barrel maturation is expensive, used for mid-priced, premium or super-premium wines. Initial investment, labour intensive (monitoring), slow process, barrique doesn’t hold much liquid.
116
Oak chips and oak staves
The alternative of the wooden vessel for producers of inexpensive and mid-priced wines. Attached to the inside of the stainless steel or concrete vessel, or they can float in the wine. Different species of wood and different seasoning and toasting levels. Cheaper, possibility to use micro-oxygenation.
117
Lees
The sediment that settles at the bottom of a wine vessel, made up of dead yeast, dying yeast and bacteria, grape fragments, precipitated tannins, nutrients and other insoluble compounds.
118
Gross lees
Sediment after the end of fermentation (24h), larger and heavier particles, more significant effect.
119
Fine lees
Smaller particles that settle more slowly.
120
Autolysis
When the yeast cells die and break down, releasing compounds that contribute flavours, body and texture to the wine. Binding with phenolic compounds in the grapes (reducing colour and softening tannins) and with components of the wood (reduction of astringency and changing the flavours).
121
Effects of the lees in still wine maturation
- Lees ageing helps in the stabilisation (unstable proteins).
- Protection from oxygen (slow and controlled oxidation, low levels of SO2). Thick layer can produce volatile and reductive sulfur compounds (unpleasant aromas if not controlled).
- Lees provide nutrients for microbes (growth of lactic acid bacteria for malo) but also encourage the development of spoilage microbes (Brettanomyces).
- Increment of costs.
122
Racking
The process of transferring the wine from one vessel to another with the aim of removing sediment from the wine. It can be an oxidative process, otherwise, fill the vessel with inert gas. It may be carried out once or several times during the maturation process.
123
Main reasons for blending
Balance, consistency, style, complexity, minimise faults, volume, price.
124
Balance - reason during blending decision
Increase or moderate the levels of certain characteristics of the wine (Merlot for body and ripe fruit with Cabernet Sauvignon that is too astringent if not fully ripe).
125
Consistency - reason during blending decision
Variation among bottles of a single product in a single vintage (NV Champagne).
126
Style - reason during blending decision
House style for the winery or certain quality-level in the range.
127
Complexity - reason during blending decision
A different range of flavours.
128
Minimise faults - reason during blending decision
Reduce the presence of a wine fault (one barrel with significant volatile acidity will be sterile-filtered and blended into a large volume of un-faulty wine).
129
Volume - reason during blending decision
From small vineyard holdings or in poor vintages.
130
Price - reason during blending decision
Expensive varieties with cheaper to keep low the cost (Chardonnay with Trebbiano or Semillon).
131
The best moment for blending
Before stabilisation, in case any instabilities arise for the blend.
132
Types of post-fermentation clarification
- Sedimentation
- Centrifugation
- Fining
- Filtration
133
Techniques to clarify grape must
- Sedimentation
| - Centrifugation
134
Clarification - what it is, types
All the processes, physical and chemical, that are used to make wine clear. Sedimentation, centrifugation, fining, filtration.
135
Sedimentation - what it is, pros/cons
The simplest form for clarification, both must and wine.
Storing in cool cellar conditions (natural clarification), suspending matter precipitating over time, sediment at the bottom, racking off (depends on the size of the container and the available labour). Longer in large, tall vessels than in smaller, shorter vessels (depth to fall). If wine is barrel-aged, sedimentation is part of barrel ageing process. Times of 12-24 h.
In case of must sedimentation, solids at the bottom will be filtered by cross flow or depth filters to extract extra juice.
No loss of texture and flavour compared to fining and filtering (wine sedimentation).
The cheapest method (no specific equipment). It takes the most time (energy cost). Batch process. Used for small-volume production of premium wines.
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Centrifugation - what it is, pros/cons
Both must and wine clarification. A machine that comprises a rapidly rotating container which uses centrifugal force to separate solids from liquids. Quick clarification, continuous use (saving time and labour costs). Oxygen exposure (otherwise use of inert gas but adds cost).
It can replace depth filtration and allow early bottling, in case of wine clarification.
Very effective with wines with a lot of matter in suspension. High-volume wineries (initial cost).
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Fining - what it is, pros/cons
Adding of a fining agent (protein or mineral origin) in the wine to speed up the process of the precipitation of suspended material. Removing a small proportion of unstable colloids. It helps to clarify and stabilize. Trial to determine the minimum amount to use. Too much fining agent (over-fining) can remove positive compounds and make the wine unstable. The fining agent must have the opposite charge from the wine colloid to attract each other and fall to the bottom of the liquid.
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Categories of fining agents
Categories of common fining agents:
- removing unstable proteins – not necessary in red wines (tannins, naturally precipitation and racking);
- removing phenolics that contribute undesirable colour and bitterness – use of bentonite and an agent to avoid an unstable wine;
- removing colour and off-odours.
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Over-fining
When too much fining agent is added for clarification. It can remove positive compounds and make the wine unstable.
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How to remove unstable proteins in post-fermentation clarification
Bentonite.
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Bentonite
Fining agent. Clay which adsorbs unstable proteins and unstable colloidal colouring matter; minimal effect of the flavour and texture; some colour loss in red wines and large amounts of sediments (wine is lost when it is racked off).
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How to remove phenolics that contribute to undesirable colour and bitterness in post-fermentation clarification
Using of bentonite and the following agents to avoid an unstable wine: egg white, gelatin, casein, isinglass, vegetable protein products, PVPP.
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Egg white
Used in fresh or powdered form; for high-quality red wines, it removes harsh tannins and clarifies wines; allergen (declared on the label).
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Gelatin
Protein collagen extracted from pork; clarification, removes bitterness and astringency in red, and browning in white wine pressings; use of the smallest effective amount otherwise risk of stripping flavour and character, and risk of protein haze forming later; no for vegetarian wines.
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Casein
Milk-derived protein that removes browning from white and clarifies wines to some extent; allergen (declared on the label).
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Isinglass
Protein collagen that very effectively clarifies white (bright appearance); use of the smallest effective amount otherwise formation of a protein haze later and fishy smell; no for vegetarian wines.
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Vegetable protein products
Fining agents that remove phenolics that contribute undesirable colour and bitterness. Derived from potato or legumes; vegan-friendly wines.
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PVPP
Polyvinylpolypyrrolidone is an insoluble plastic in powder form that removes browning and astringency from oxidised white; gentler than charcoal; rarely used for red (reduce astringency and brighten the colour).
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Fining agents that remove colour and off-odours
Charcoal.
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Charcoal
Removes brown colours and some off-odours; it can remove also some desirable aromas and flavours; it’s suggested to treat only one batch and then blend it with the rest.
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Filtration - what it is, types
The most common way of clarifying. Physical separation technique used to eliminate solids from a suspension by passing it through a filter medium consisting of porous layers that trap solid particles.
Depth filtration and surface filtration.
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Depth filtration - what it is, types, pros/cons
It traps particles (many irregular channels) in the depth of the material that forms the filter. It doesn’t block easily. No reliable.
- Diatomaceous earth (DE or Kieselguhr) – most common, pure silica and inert; used in rotary vacuum filters for very thick and cloudy wines (oxidative); enclosed DE filters work with inert gas (nitrogen) then avoid oxidation; range of particle sizes so can remove large or very small particles; cost.
- Sheet filters (plate and frame or pad filters) – wine passes through a sheet of the filtering material; more sheets then quicker operation; used to remove remaining yeasts at bottling; initial investment and trained personnel.
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Diatomaceous earth
Type of depth filtration.
The most common, pure silica and inert; used in rotary vacuum filters for very thick and cloudy wines (oxidative); enclosed DE filters work with inert gas (nitrogen) then avoid oxidation; range of particle sizes so can remove large or very small particles; cost.
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Sheet filters
Type of depth filtration.
Wine passes through a sheet of the filtering material; more sheets then quicker operation; used to remove remaining yeasts at bottling; initial investment and trained personnel.
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Surface filtration - what it is, types, pros/cons
It stops particles that are bigger than the pore size of the filter from going through.
- Membrane filters (cartridge filters) – catch particles that will not go through the pore size of the filter; slower than depth filtration (< 1 µm); pre-filtration first; final precaution before bottling (clear and microbiologically stable); not entirely accurate; small initial investment but high cost for the cartridge.
- Cross-flow filters (tangential filters) – wine passes through the filter while uniquely cleaning the surface of the filter as it works; no solid particles; high load, very quick; no cartridge; expensive; large productions.
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Membrane filters
Type of surface filtration.
Catch particles that will not go through the pore size of the filter; slower than depth filtration (< 1 µm); pre-filtration first; final precaution before bottling (clear and microbiologically stable); not entirely accurate; small initial investment but high cost for the cartridge.
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Cross-flow filters
Type of surface filtration.
Wine passes through the filter while uniquely cleaning the surface of the filter as it works; no solid particles; high load, very quick; no cartridge; expensive; large productions.
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Stabilisation - what it is
Several winemaking interventions which, if not carried out, could lead to undesired effects in the finished wine.
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Types of stabilisation
- Protein
- Tartrate
- Microbiological
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How to obtain protein stability
Fining with bentonite.
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How to obtain tartrate stability
Harmless deposits of crystals (potassium bitartrate and calcium tartrate) that have been removed by:
- cold stabilisation;
- contact process;
- electrodialysis;
- ion exchange;
- CMC (Carboxymethylcellulose);
- metatartaric acid.
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Cold stabilisation
A way to obtain tartrate stability.
Wine held at -4°C for 8 days (tartrate are less soluble at cold temperatures), crystals forming, filtering; cost of equipment and energy; used only for potassium bitartrate.
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Contact process
A way to obtain tartrate stability.
Quicker way, potassium bitartrate is added to the wine and speeds up the start of the crystallisation process, cooling at 0°C for 1-2h, filtration.
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Electrodialysis
A way to obtain tartrate stability.
Charged membrane to remove selected ions; high initial investment (lower than cold stabilisation); less energy, faster; used for potassium and calcium ions and tartrate ions; allowed in the EU and other territories.
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Ion exchange
A way to obtain tartrate stability.
| Replacing potassium and calcium ions with hydrogen or sodium ions; not allowed in some countries (health).
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CMC
A way to obtain tartrate stability.
Carboxymethylcellulose, cellulose extracted from wood and prevents tartrates from developing to a visible size; used for cheap white and rosé wines, no red (tannins); cheaper than chilling; wines stable for a few years.
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Metatartaric acid
A way to obtain tartrate stability.
It prevents the growth of potassium bitartrate and calcium tartrate crystals; unstable (when storing the wine at high temperatures); quick and easy process; used for red wines; long-lasting.
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How to obtain microbiological stability
Wines with RS can start re-fermentations, then removing yeast through sterile filtration or adding sorbic acid (people can detect the smell) and SO2 (less common); lactic acid bacteria so complete malo or filtering the wine; Brettanomyces with DMDC.
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Amounts of free SO2 at the point of filling
- white wines 25-45 mg/l;
- red wines 30-55 g/l;
- sweet wines 30-60 g/l.
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Sparging
Removing the oxygen from the wine by flushing the wine with an inert gas.
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Final adjustments before bottling
- Adjusting the level of sulfur dioxide.
- Reducing dissolved oxygen.
- Adding carbon dioxide.
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Types of faults in the wine
- Cloudiness and hazes.
- Tartrates.
- Re-fermentation in bottle.
- Cork taint.
- Oxidation.
- Volatile acidity.
- Reduction.
- Light strike.
- Brettanomyces.
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Cloudiness and hazes (fault)
Growth of yeast or bacteria (better hygiene in the winery, pre-bottling chemical analysis, filtering the wine), poor filtering, protein haze (fine correctly).
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Re-fermentation in bottle (fault)
Cloudiness and bubbles (failure during stabilisation and filtration/fining), CO2 in cheap wines.
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Cork taint (fault)
Wet cardboard smell.
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Volatile acidity (fault)
Activity of acetic acid bacteria, inadequate levels of SO2, excess exposure to oxygen (sorting grapes, hygiene in winery, topped up vessels, careful racking, adequate levels of SO2).
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Reduction (fault)
Sulfur-like odours (from onion to rotten eggs), high levels of volatile, reductive sulfur compounds, complete exclusion of oxygen during ageing in closed vessels; sufficient nutrients and oxygen for yeasts, adequate temperature for the must.
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Light strike (fault)
Light (UV radiation) reacts with certain compounds in the wine to form volatile sulfur compounds (dirty drains); dark glass provides more protection.
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Brettanomyces (fault)
Off-aromas from animal, spicy or farmyard smells, fruity flavours are reduced and acidity/tannins become more prominent; hygiene, effective SO2 levels, keeping low pH and short period between alcoholic fermentation and malo so adding of SO2 as soon as possible.
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Tartrates (fault)
Colourless or white crystals in the bottom of the bottle, natural process triggered by low temperatures, harmless.
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Oxidation (fault)
Excessive oxygen exposure in the winemaking process, or once in bottle or other container.
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OTR
Oxygen Transmission Rate
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Where you can find oxygen in the wine bottle
- dissolved oxygen in the wine;
- oxygen in the head space;
- oxygen in the cork or other closure;
- OTR (oxygen transmission rate).
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Types of packaging for wine
- Glass.
- PET.
- Bag-in-box.
- Brick (Tetra Pak).
- Pouch.
- Can.
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PET - what it is, pros/cons
Type of packaging. Polyethylene terephthalate, wines of short term storage and early drinking.
✅ light, tough, inexpensive, recyclable, impermeable (lined with a barrier), range of sizes
❌ waterproofing treatment, no ageing
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Bag-in-box - what it is, pros/cons
Type of packaging. Famous in Sweden and Australia. Cardboard box with a flexible bag inside of thin aluminium foil otherwise plastic.
✅ flexible pour size, protection from oxygen after pouring (collapse), range of sizes (1.5-20 l), easy to store, low environmental impact
❌ higher SO2 (oxidation), low dissolved oxygen (no head space), low CO2, no ageing (max 1 year)
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Glass - what it is, pros/cons
The most common type of packaging.
✅ inert material, impermeable to oxygen, sterile condition to the wineries, inexpensive to manufacture, range of colours, 100% recyclable, best option for ageing
❌ high carbon footprint to manufacture, heavy to transport, fragile, rigid (oxidation when opened), light strike
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Brick (Tetra Pak) - what it is, pros/cons
Type of packaging. Paper card with plastic layers and an aluminium foil.
✅ protection from oxygen and light, entirely filled, lower price points, designs
❌ filling equipment, no ageing
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Pouch - what it is, pros/cons
Type of packaging. Similar to the bags inside bag-in-boxes, larger and single serve sizes.
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Can - what it is, pros/cons
Type of packaging. Wines of early consumption.
✅ weight, robust, easy to open, impermeable to oxygen, recyclable
❌ plastic treatment (acidity could be a problem), big investment
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Main options for the closures
- Cork
- Synthetic closures
- Screwcap
- Glass stoppers
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Key characteristics of the closure
Protect from oxidation, inert, easy to remove, cheap, recyclable, free from faults.
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Cork - what it is, pros/cons
60% of wine bottles.
- Natural
✅ light, flexible, inert, natural resource
❌ TCA (3-5%), variable rates of oxygen ingress
💡 cleaning cork with stream extraction (Amorim), quality control during production (gas chromatography), membrane between the cork and the wine
- Technical – manufacturing process (agglomerated cork)
💡 closures from recomposed cork particles that have been cleaned and reconstituted with a plastic (Diam)
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Synthetic closure - what it is, pros/cons
Food-grade plastic with a silicone coating, plastic can absorb aromas, same bottles for cork
- Moulded – cheap, rigid to re-insert, no ageing;
- Extruded – more elastic, limited oxygen protection (Nomacorc).
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Screwcap - what it is, pros/cons
Aluminium closure, seal of a wad of either tin (no oxygen) or Saran (low permeability to oxygen).
✅ easy to open, no TCA
❌ special bottle, reductive wine (decrease SO2), consumers not yet ready (double production)
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Glass stopper - what it is, pros/cons
Glass with a plastic ring.
✅ long ageing, attractive
❌ special bottle, expensive
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Key points of post-bottling maturation
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Ageing improves costs to the wineries.
Some PDOs (Chianti Classico Riserva DOCG) specify minimum ageing before the wine can be distributed and sold.
A small amount of oxygen can be positive (slow development in the bottle), primary aromas become tertiary, tannins are softened, better integration of oak aromas, darker colour in white wines and paler in red.
Too little oxygen before bottling, so formation of volatile, reductive sulfur compounds in the bottle (struck match and smoke for low level and rotten egg for high level).
Ideal conditions of constant temperature of 10-15°C, constant humidity, bottles on their side (cork), no light.
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Procedures for hygiene
- cleaning (removal of surface dirt);
- sanitation (reduction of unwanted organisms by water and detergent, 1 l of wine = 10 l of water);
- sterilisation (elimination of unwanted organisms with high strength alcohol or steam).
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Quality control
The set of practices by which the company ensures a consistently good quality product.
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Quality assurance
The complete way a business organises itself to deliver a good product consistently and to protect itself from legal challenge.
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HACCP
Hazard Analysis of Critical Control Points is the common approach in which the company identifies all the possible hazards that could affect final wine quality. For each hazard, the HACCP document will state how serious it is, how it can be prevented and how it can be corrected. It’s carried out by the company producing the wine with no checking by a third party.
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The reason to use ISO standards
To give assurance to all the parties down the supply chain: the wholesaler and the retailers who will sell the wine and the end consumer. The ISO sets the standards and separate certification bodies carry out the audits.
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Traceability
Through the lot number, to respond to and investigate complaints about wine or improve its practice so that similar problems do not occur in the future. The possibility to trace back all the activities at every point of production and also transportation.
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Ways to transport wine
Bulk shipping or in the bottle.
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Bulk shipping - what it is, pros/cons
30-40% of volume.
- Flexitank – single-use, recyclable polyethylene bag into a standard container, coated with a barrier (preventing taint and reducing oxygen);
- ISO tank – stainless steel vessel (ISO standard), reused many times, additional insulation.
✅ cheaper, more environmentally friendly (24,000 – 26,000 bottles in liquid), thermal inertia, strict quality control, wine can be adjusted, extended shelf life
❌ no relationship with producer, less employment opportunities
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Shipping wine in the bottle - what it is, pros/cons
✅ control by the producer (wine, bottling, labelling, packaging)
❌ cost (small amount, weight), potential fluctuating of temperatures, potential spoilage of labels and packaging, shorter shelf life for inexpensive wine (bottling), low environmental (9,000 – 10,000 bottle)
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Skin contact in white wines - what it is
The process of leaving the juice in contact with the skins to extract compounds from the skins. The main purpose is to enhance the extraction of aroma and flavour compounds and precursors, and to enhance the texture of the wine by extracting a small amount of tannin. Not indicated for all the styles. Minimal skin contact for wines with delicate fruity flavours, minimal colour and a smooth mouthfeel, early drinking style.
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Consequences of skin contact for under-ripe white grapes
They can extract bitter flavours and astringent tannins.
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The most suited white grapes for skin contact
Most effectively used on aromatic varieties because they have a lot of aroma compounds to extract (Riesling, Gewurztraminer, Viognier, Muscat, Sauvignon Blanc), enhancing texture, homogenisation.
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How to control the extraction during skin contact
Chilling reduces the extraction rate, permits more control, reduces the oxidation rate and microbial spoilage; down to below 15°C.
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Orange wines
White wines made by white grapes, skin contact, no temperature control or sulfur addition, oxidation compounds, dry, notable levels of tannins, tertiary characteristics (nuts and dried fruit).
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Whole bunch pressing - pros/cons
Whole bunch to reduce the chance oxidation especially with the use of inert gas (nitrogen, carbon dioxide, dry ice). Stems provide channels for the juice to drain. Only possible when hand harvest. More press cycles (fewer grapes can be loaded). Suitable for small batches of premium wines, no for large volumes of inexpensive and mid-priced.
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Free run juice
The juice that can be drained off as soon as the grapes are crushed. Low in solids, tannin and colour. High cost by producing a wine made entirely with free run juice (small volume).
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Press juice
The juice that runs off through the pressing. Initially, it’s similar to free run juice but more pressings extract more solids, tannin and colour. Lower acidity and less sugar than free run juice, for full-bodied wines. Separated into different fractions (press fractions) that may be blended later. The last press fractions tend to be too astringent and bitter (discarded).
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The proportion of solids in the must
0.5-2%
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Consequences of a high level of solids
Improve the texture of the wine, greater range of aromas, and greater complexity (premium Chardonnay). Fermentation can give reductive sulfur compounds, good at low levels (struck match, smoke) but negative at higher levels (rotten eggs). It needs regular monitoring (cost).
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Consequences of a low level of solids
Usually for fruity wines (inexpensive Pinot Grigio). Less risk of off-flavours that could reduce quality. Less labour (no regular monitoring).
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Types of must clarification
- Sedimentation.
- Flotation.
- Centrifugation.
- Clarifying agents.
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The usually moment to apply must clarification
Between pressing and fermentation.
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Flotation - what it is, pros/cons
Must clarification. Bubbling inert gas (nitrogen) up through the must. Rising, they bring solid particles. Speeds up the rate of clarification. Hyperoxidation in case of oxygen use. Adding of fining agents. More expensive than sedimentation (equipment), effective, quick, continuous or batch process. Saving energy cost (no chilling).
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Pectolytic enzymes - what they are, pros/cons
To speed up the rate of sedimentation. Pectolytic enzymes break down pectins (found in plant cell walls) in the must. So more rapid separation between solids and liquid. Only for the must, others for must and wine. Cost of purchasing the agents but less time and energy than sedimentation.
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Temperatures and vessels for white fermentation
```
Cooler than red (around 15°C) for the volatile aroma and flavour compounds. Stainless steel tanks for fruity, floral white wines (Sauvignon Blanc and Pinot Grigio).
Slightly warmer (17-25°C) for no fruity styles, to promote yeast health and avoid the production of certain esters (isoamyl acetate). Concrete and old oak vats (some Chablis and white Rioja).
Small oak barrels (premium and super-premium Chardonnay) give deeper colour, fuller body, improve texture, more blending options. No for aromatic grape varieties.
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When malo for white wines
Usually for low-aromatic varieties (Chardonnay), avoided in aromatic (Riesling and Sauvignon Blanc).
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When barrel maturation for white wines
Usually, premium and super-premium with low-aromatic varieties (Chardonnay) to improve texture and complexity.
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Lees stirring
Also called bâtonnage, it can increase the release of yeast compounds into the wine. Use a rod and manually stir the lees into the wine. This method increases oxygen exposure (removing the bung) so more effect from dead yeast and less fruity aromas. Barrel rack to agitate and/or mix the lees without open the vessel. It increases cost and labour.
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Ways of producing wines with residual sugar
- Concentrating the grape must
- Stopping the fermentation
- Blending in a sweetening component
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Methods of concentrating the grape must
- Drying grapes on the vine
- Drying grapes off the vine
- Noble rot
- Freezing grapes on the vine
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Characteristics of the wine obtained from the reduction of the water
Concentration of the sugars, acidity and flavours thanks to the reduction of the water content in the grape. The increase of acidity and flavours is in balance with sugars (very good to outstanding quality).
More complexity, dried fruit flavours, water is depleted, low juice volume. Hard extraction of sugary pulp during pressing, so more production costs.
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How to stop manually the fermentation
By chilling to below 10°C and/or adding high dose of SO2 to inhibit the yeast. Racking the wine and sterile filtration. Fortification is another option.
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Ways of drying grapes on the vine in the sweet wine production
During ripening, water is lost by grape transpiration (shrivelling) and then sugars concentrate, developing of very ripe flavours (Pinot Gris - stone fruit when ripe, tropical and dried stone fruit when extra-ripe). Long and dry autumns are needed (no grey rot). Late Harvest wines (Vendages Tardives from Alsace and Spätlese from Germany and Austria).
Another method by cutting the cane of the vine a short time before harvest. Shrivel is quicker (concentration of sugars, acids and flavours), less risk of grey rot, very high levels of sugars, no extra-ripe flavours. Used for wine in Jurançon and Australia.
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How to dry grapes off the vine in the sweet wine production
Grapes are picked and dried (from days to months). Drying process by the sun in warm climates (southern Italy or Spain) or in a temperature- and humidity-controlled room (Valpolicella, more costs). Water evaporates, so concentration of sugars, acids and flavours. Passito wines in Italy (Recioto di Valpolicella e Vin Santo).
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Requirements for the development of noble rot
It’s needed fully ripening of the grapes, region that provides humidity, misty mornings followed by sunny and dry afternoons (slow development of the rot and water evaporation, not always these conditions).
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How noble rot operates
The fungus punctures the grape skin with microscopic filaments, leaving tiny holes in the skin. Modifying of the aroma compounds with distinctive flavours such as honey, apricot, citrus zest, ginger and dried fruit aromas.
The fungus contributes an enzyme (laccase), resistant to SO2 and able to oxidise grape must and wine. So chilling, high dose of SO2 and use of inert gas. Difficulty to clarify, press and ferment the high-sugar-content must.
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Ageing for sweet wines by noble rot
Maturation in oak if neutral grape varieties (Semillon) to improve texture and adding flavours, otherwise stainless steel tanks if aromatic grape varieties.
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Cryoextraction
A technique used in sweet wine production. Picking the grapes in autumn and freezing them at a winery. When not typical climate conditions, no risk of leaving the grapes in the vineyard. Not allowed for Eiswein and Icewine. Energy cost for freeze the grapes but cheaper than traditional Eiswein/Icewine production.
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How to produce sweet wine by freezing grapes on the vine
Leave healthy grapes on the vine during late autumn and winter. Freezing temperatures freeze the water in the grape pulp. Then, picking and pressing, the ice remains in the press and the sugar content is concentrated.
Fermenting and storing in stainless steel tanks (sometimes oak to add extra flavours).
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Key characteristics and examples of grape varieties used in sweet wine production by freezing grapes on the vine
Hard vines against cold temperatures, resilient skins from disease and can withstand the strain of freeze-thaw cycles.
Riesling, Vidal and Cabernet Franc (occasionally).
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Pros/cons of stopping fermentation in sweet wine production
Quick, simple and low risk process, used for inexpensive or mid-priced wines, different intensity and complexity from the wines produced with sugar concentration.
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How to produce sweet wine by blending in a sweetening component
The easiest way to produce a sweet wine. Storing the dry wine until bottling and then blend it with the sweetening component. Dry wines are less susceptible to microbial spoilage than wines with residual sugar.
More control by the winemaker (trial, measure and add the component), large volumes, consistent product. It can increase the volume of the final wine. Acceptable to good quality and inexpensive prices.
Sugar, RCGM (rectified concentrated grape must) and unfermented grape juice (Süssreserve in Germany) are common sweetening components.
Local law regulations (no sugar in the EU), same wine region for the unfermented grape juice and the wine made in the PDO.
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Sweetening components used in the sweet wine production
Sugar, RCGM (rectified concentrated grape must) and unfermented grape juice (Süssreserve in Germany) are common sweetening components. Unfermented grape juice contributes a grape-juice-like character, RCGM is processed so that it just contains the sugar from the grape (no extra flavours, small quantities). Both are inexpensive.
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Factors that affect the extraction of anthocyanins, tannins and flavours in red wines
- temperature (higher temperatures);
- time on skins (longer time);
- management of the skins and juice (more mix between skins and juice);
- the medium in which the extraction is taking place (tannins are most soluble in alcoholic solutions, anthocyanins in aqueous solutions).
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Common ways of maceration before fermentation for red wines
- Cold soaking.
| - Macerations using heat.
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Cold soaking - what it is, pros/cons
Also called cold maceration or pre-fermentation maceration. Chilling the juice and skins (4-10°C, slow extraction) to reduce the rate of oxidation, microbial spoilage and spontaneous fermentation. It’s typical for pre-fermentation maceration to last 3-7 days, punching down and/or pumping over to mix up the skins and juice (aiding extraction). No growth of spoilage microbes that need oxygen (acetic acid bacteria) on the top of the cap of skins. Cold soaking is a gentle technique, premium wines. Applied on Pinot Noir. Energy cost for chilling the wine, long time (no for high volume and inexpensive wines).
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Macerations using heat - what they are, pros/cons
Also extraction of some tannins. Flash détente and thermovinification.
Thermovinification – heating the must at 50-60°C (from minutes to hours, higher temperatures shorter macerations).
Flash détente – quick heating to 85-90°C and cooling under a vacuum (max 2 minutes, no risk of cooked flavours). Bursting the cells of the grape skins allows very rapid extraction of anthocyanins and flavours. High cost for the vacuum system (large volumes).
With both techniques, the juice may be pressed off the skins before fermentation if a low tannin and fruit style is desired. Possibility of colour instability (low levels of tannins). Used for inexpensive and mid-priced wines. In premium wines, as a blending to add juicy and fruity flavours. Intensification of the wine fruitness but a little reduction of varietal characters.
They’re useful against botrytis, high temperatures denature oxidative enzymes (laccase) produced by rot. Flash détente is useful against smoke taint.
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Main cap management techniques
- Punching down.
- Pumping over.
- Rack and return.
- Ganimede tanks.
- Rotary fermenters.
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Factors of maceration during fermentation that can influence the style of the wine
- different techniques (punching down, pumping over, rack and return, ganimede tanks, rotary fermenters);
- winemaker can alter the frequency and the duration (more extraction by pumping over three times a day for 15’ than 10’ once a day);
- the timing of mixing can influence what compounds are extracted (more mixing at the start and less mixing at the end to obtain more colour and fewer tannins).
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The reasons to mix cap with the juice during fermentation
Without mixing, cap macerates in the same small volume of liquid and therefore dissolution of these compounds into the liquid would stop (saturated with colour, tannins and flavours). Mixing promotes extraction, otherwise cap dries out and no extraction. Mixing helps to distribute the heat produced (essential for temperature control).
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Punching down
Cap management technique. A plunger is used to submerge (by hand or mechanically) the cap of grape skins in the liquid. Labour intensive, by hand for low production of premium wines. Possibility to punch down the cap and ensure adequate mixing of the skins in relatively small, open top vessels. Gentle process, also called pigeage.
249
Pigeage
French term for punching down.
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Pumping over
Cap management technique. Juice/wine is taken (1/3 to 1/2) from near the bottom of the vessel and sprayed over the cap of skins. Gentle extraction of colour, tannins and flavours passing through the cap. It can be carried out aerobically (splashing the wine into a new container). Oxygen exposure (yeast health and no reductive off-flavours). Possibility to carry out pumping over anaerobically in closed vessels (attaching the hose to a tap at the top of the vessel or keeping the hose close to the cap in an open vessel). Used for all black varieties, all price points and quality, suitable for use in large vessels. Modern wineries have pumps and hoses installed at each tank, possibility of scheduling. Also called remontage.
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Remontage
French term for pumping over.
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Rack and return
Cap management technique. Similar to pumping over, 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 original vessel and is sprayed over the skins. Breaking up of the cap, mixing of juice/skins. More extraction than punching down or pumping over. Only 1-3 times during fermentation, alongside punching down and pumping over. Used for red wines where medium to high levels of flavour, colour and tannin are desired (Cabernet Sauvignon and Syrah). Not fully automation, labour to setup and monitor the process, a clean vessel (not ideal for small wineries). Also called delestage.
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Delestage
French term for rack and return.
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Ganimede tanks
Cap management technique. Specialised tanks bubble CO2 up through the must/wine. Pressure builds up under the cap, until finally the cap bursts. Quick breaking up of the cap, like rack and return, relatively extractive and suited to produce wine with medium to high levels of colour, tannins, and flavours (Cabernet Sauvignon and Syrah). New technique, fully automated, less labour intensive than rack and return, more expensive than standard stainless steel tanks. Possibility to use oxygen instead of CO2.
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Rotary fermenters
Cap management technique. Horizontal, closed, stainless steel tanks. The whole tank rotates and internal blades break up the cap and ensure adequate mixing. More surface area between grape skins and juice. Used for wines with medium to high levels of colour, tannin and flavours (Cabernet Sauvignon and Syrah). Fully automated, less labour. High volume, inexpensive or mid-priced wines with acceptable or good quality. Very effective extraction, high cost.
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Must concentration for maceration
Drawing off some of the juice just after crushing and before the start of the ferment, concentrating the remaining must. Less volume for the red wine production, implication for the price. The juice remove is typically used for rosé wine production (light colour), also called saignée.
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Co-fermentation
Fermenting different grape varieties together in the same vessel (max 5% of white grapes). Taking advantage of some of the phenolic compounds found in the white that can increase colour intensity and stability through binding with anthocyanins (higher quality). Contribution also for aroma compounds. Dilution if too much white grapes (lower colour intensity). Originated in the Rhone Valley, with the Côte-Rôtie appellation (Syrah and Viognier). No adding costs. Now, it’s more a blend operation to improve aroma compounds.
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The reason to use the whole berry/bunch during fermentation
To create an oxygen-free environment for the uncrushed fruit. Lack of oxygen has several outcomes. Grapes change from aerobic respiration to anaerobic metabolism (sugar is converted to alcohol without yeast, intracellular fermentation). Malic acid is also broken down to create ethanol (decrease up to 50%), decrease of acidity and increment of pH. Glycerol levels increase (more texture) and a range of distinctive aromas is created (kirsch, banana, bubble gum and cinnamon).
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Forms of whole berry/bunch fermentation
- Carbonic maceration.
- Semi-carbonic maceration.
- Whole berries/bunches with crushed fruit.
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Carbonic maceration
Only whole, uncrushed munches into vessels that are filled with CO2 to remove all the oxygen. Intracellular fermentation starts. Reaching 2% abv, the grape skins start to split and the grapes release their juice. Draining the juice and pressing the grapes (separation of skins from juice). Yeast complete the fermentation off the skins.
Colour extraction from the grapes but little tannin (they need alcohol). The wine obtained has low tannin with distinctive notes of kirsch, banana, bubble gum and cinnamon, alongside the fruit notes from the grape variety. Consumption within a year after harvest. Distinct flavours but not complex. Acceptable or good quality, inexpensive and mid-priced. Beaujolais Nouveau from Beaujolais.
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Semi-carbonic maceration
Similar to carbonic maceration, no filling with CO2. Only whole bunches, grapes at the bottom crushes under the weight of the grapes above and some juice is released. Ambient yeast start to ferment the juice, production of CO2 and so carbonic maceration.
If the winemaker wants more concentration, body and tannin, the alcoholic may continue on the skins and involve some punching down or pumping over. Then, it’s possible post-fermentation maceration and/or maturation in oak to add complexity. Better integration of the aromas from intracellular fermentation with the aromas from the grape variety. Wines with more fruitiness and a softer mouthfeel than crushed fruit fermentations. Pinot Noir, Malbec, Tempranillo, Gamay and Carignan.
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Whole berries/bunches with crushed fruit
Whole berries/bunches are submerged by the crushed grapes. No oxygen, so intracellular fermentation. More carbonic characteristics by raising the percentage of whole berries/bunches present. The whole berries/bunches are gradually crushed during fermentation (punching down the cap). It’s possible post-fermentation maceration and/or maturation in oak to add complexity. Smoother texture and more vibrant and fresh primary aromas. Used for a wide range of grape varieties of different qualities and prices.
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Intracellular fermentation
In an oxygen-free environment, the grapes change from aerobic respiration to anaerobic metabolism. Some of the sugar in the grapes is converted to alcohol.
Malic acid within the grape is also broken down to create ethanol (malic reduction up to 50%), pH increases. Distinctive aromas of kirsch, banana, bubble gum and cinnamon.
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Temperatures and vessels for red fermentation
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Warmer temperatures can cause volatile, fruity aromas to evaporate so balance is needed.
Cool temperatures (20°C) to produce fruity, low tannin wines.
Warmer temperatures (30°C) for more concentration and tannin structure to age.
Fermentation in stainless steel, concrete or wooden (usually large) vessels. They could be open at the top (extraction techniques). Fermentation in wooden vessels for premium and super-premium wines (more labour), it gives a rounder mouthfeel to the wine and better integration of oak compounds. Concrete and stainless steel to retain fruit flavours.
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Post-fermentation maceration in red wines
Further extraction of tannins, encourage the polymerisation of the tannins (improving tannin structure and texture). It takes space and time.
Usually for premium and super-premium wines, very good to outstanding quality.
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Timing of pressing in red wine production
Timing of pressing depends on the style. Carbonic maceration, pressing when 2% abv of fermenting must to produce a wine with medium levels of colour and fruity flavours but low tannins. During fermentation to create a wine with relatively little tannin. After post-fermentation maceration to maximise the tannin structure of the wines. Just before the end of alcoholic fermentation if the wine will finish fermenting in barrels (better integration of oak flavours and rounder mouthfeel).
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When malo for red wines
Routinely carried out. Oak barrels for better integration of oak characteristics during maturation.
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When barrel maturation for red wines
Significant impact on the style. More common in red than white.
No oak for inexpensive red wines. Possibility to obtain spicy flavours of wood by chips or staves.
Proportion of new oak to enhance the complexity of the wine.
The gentle oxidation helps to soften tannins, can lead to the development of tertiary aromas and flavours that can enhance complexity and quality.
Possibility to find mid-market and premium wines that have not been matured in oak or minimal ageing of old oak, focus on fruity aromas (Loire Valley Cabernet Franc, Spanish Mencia and Argentine Malbec).
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Lees ageing for red wines
It can help to soften tannins, possibility of colour reduction.
Racking to control the amount of lees in the vessel.
No gross lees or stirring the lees.
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Ways of rosé wine production
- Direct pressing.
- Short maceration.
- Blending.
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Direct pressing in rosé wine production
Ideal for some of the lightest-coloured rosé. Whole bunch or destemmed, no maceration. Pneumatic presses (use of inert gas). Fermentation like a white wine. Also called vin gris (Provence).
White grapes for the possibility of co-pressing and co-fermentation with black grapes to lend extra acidity and help to achieve a paler colour (Rolle in rosé wines from Côtes de Provence).
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Short maceration in rosé wine production
Short period of pre-fermentation maceration (from a couple of hours to a few days) before pressing. Protection with inert gas (oxidation and microbial spoilage). The longer the maceration, the more colour, flavour and tannin will be extracted. Draining of the juice and pressing of the skins. Wines with deeper colour and more pronounced flavours. Spanish rosé and rosé of Tavel.
Saignée, the by-product of must concentration in red wine production. Relatively cost effective production. Disadvantage of black grapes harvested for red wines, so lower acidity. Good to outstanding quality if quality-conscious producers.
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Blending in rosé wine production
A small proportion of red wine with white wine and it retains the aromas and flavours of the white grape. Sauvignon Blanc rosé. Law regulations (no in Europe, exception in Champagne). It’s thought that this method lowers the quality of rosé wines. Simple and cheap if already production of red and white wines. Used for inexpensive wines.
Colour is fundamental (clear glass). Pale colours are often associated with dry styles, more deeply coloured rosés are often associated (sometimes wrongly) with off-dry, medium-dry and medium-sweet styles. Colour decreases during fermentation, the winemaker has more control by blending.
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Saignée
French term for a way of rosé production. Black grapes are grown to be processed for red winemaking (lower acidity). After initial maceration, a part of the juice is drained off just after crushing and before the start of ferment. It's light in colour. The remaining part will be used to produce red wine. Relatively cost effective production. Good to outstanding quality if quality-conscious producers.
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Key points for viticulture in rosé wine production
Usually desirable for rosé wines to have medium-high acidity, low-medium alcohol and fresh fruit flavours. Grape growing in cool or moderate regions or cool to moderate sites within warmer regions. Cooling influence from latitude, altitude, aspect, large bodies of water. Higher yields than red wines (less concentration).
The current trend is for rosés that have pale colour, minimal tannins.
Harvest is earlier than black varieties (high acidity, delicate and fresh fruit characteristics). Ripe tannins if wine by short maceration (no green flavours), less important in direct pressing. Both machine (useful in warm climate, so night harvest, faster and cheaper in certain circumstances) and hand harvest (whole bunch pressing, low colour).
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Key points for fermentation and ageing in rosé wine production
Pre-fermentation adjustments for acidity or sugar levels.
Fermentation at cool temperatures (12-16°C). Usually stainless steel tanks, rarely oak (it’s needed fruit concentration). Use of cultured yeast (fruit flavours promotion).
Rosé with residual sugar by stopping fermentation or adding sweetening component.
Malo is usually avoided (buttery flavours mask fruity aromas). Freshness is a key characteristic of most rosés, so acidity is retained.
Short maturation on the lees and/or oak vessels to add texture and body to the wine. New oak for a different style of rosé. At least mid-priced for rosé that has spent time on the lees or in oak.
Blending between red and white wines just before finishing and packaging (to tweak the colour and flavour profile or to ensure consistency of colour across batches).
Appearance is a key characteristic, so fining and filtering to increase clarity. Sterile filtration on wines with some residual sugar to avoid the presence of unwanted microbes that could otherwise feed off this sugar in the bottle.
