Bubbles
In sparkling wine the carbon dioxide must be its own, at an excess pressure in the bottle of at least 3.5 bar at 20 °C.36 In Champagne the second fermentation happens in the bottle itself.37
Wine from zero
A course for people starting from a blank page. No jargon to memorise and no required raptures: just what happens in the berry, in the winery and in your mouth.
16 chapters · about 30 minutes
Start with chapter one- 1What is wine?
- 2What is wine made of?
- 3What is inside a grape?
- 4Where does the colour come from?
- 5What makes up the taste?
- 6Why can wine smell of strawberry or pepper?
- 7What is a grape variety?
- 8How does a vine spend its year?
- 9Where do grapes grow?
- 10Why does climate change the taste of wine?
- 11What does soil give to wine?
- 12What happens in the winery?
- 13How do white and red differ in the winery?
- 14Why are wines so different?
- 15What does the bottle tell you?
- 16How do you taste wine?
6 chapters
What is in the glass
Chapter 1
What is wine?
Put simply, wine is fermented grape juice. Grapes are crushed to release their sweet juice, and fermentation then turns it into an alcoholic drink.1
There is also a strict definition. The International Organisation of Vine and Wine (OIV) calls wine only a drink made by the alcoholic fermentation, complete or partial, of fresh grapes or grape must.2 It must have at least 8.5% alcohol by volume, though local rules may lower the minimum to 7%.2
Yeast does all the work. Yeasts are microscopic fungi: they eat the grape's sugar and give off alcohol and carbon dioxide.3 Usually one species takes over the fermenting juice, Saccharomyces cerevisiae.4
Along the way yeast makes other substances too. Glycerol, for example, forms as a by-product of fermentation.5 We will come back to it.
sugar
alcohol
C6H12O6 → 2 C2H5OH + 2 CO2
Chapter 2
What is wine made of?
Most of what is in the glass is plain water: about 85% of the volume. The exact share depends on how much alcohol and sugar the wine has.1
Second comes alcohol (ethanol). Most wines have roughly 8 to 15% by volume; fortified wines, which have alcohol added, 15 to 22%.1 '12% abv' on a label means that 12% of the wine's volume is alcohol.1 In dry wines glycerol comes third.1 There is usually 1 to 15 grams of it per litre.5
Acids give wine its freshness. The main ones, tartaric and malic, come from the grape, while lactic and acetic acid usually appear during winemaking and ageing. Total acidity in most wines is 5.5 to 8.5 g/L.1 Very little sugar is left in a dry wine: usually 2 to 3 g/L.1
The rest is traces. Aroma compounds are a tiny part of the wine,1 yet more than 800 of them have been found, and some act at levels of nanograms per litre.8 Inorganic matter (potassium, magnesium, iron and others) is about 0.2%.9,1
Chapter 3
What is inside a grape?
A grape can be roughly divided into three parts: skin, pulp and seeds. Each has a different chemical make-up, and that strongly shapes the wine.10
The pulp is mostly water, sugars and acids.1 The main sugars of a ripe berry are glucose and fructose, the main acids tartaric and malic.10 As the berry ripens, its malic acid goes down.10
The skin holds most of the colour, tannin and aroma compounds.1 Pigments, mainly anthocyanins in red grapes, start to build up in the skin when the berry changes colour, and so do many aroma compounds.10 On the outside the skin is covered with a waxy layer, the cuticle.10
The seed coat also holds a fair amount of tannin.10 As the berry ripens, skin tannins change their structure and become less astringent and less bitter.10
Chapter 4
Where does the colour come from?
Wine gets its colour from the grape skin. The juice itself is usually colourless.11 The colouring agents are anthocyanins, pigments in the skin.1
For white wine the skins are usually removed straight away. Red wine is pressed only after fermentation, and all that time the skins colour the wine. Most rosé is made by leaving crushed grapes on their skins for a short time, then separating the juice and fermenting it like a white.11
So black grapes can make wine of any of the three colours. Take the juice off the skins at once and you can even make white wine, though almost all white wines come from white grapes. A famous example is Champagne, where white sparkling wine is also made from black grapes.11 Its most planted grape is the black Pinot Noir, on 38% of the vineyards.12
- Skin contact
- The time the juice or fermenting wine stays with the skins and draws colour from them.11
Chapter 5
What makes up the taste?
The tongue picks up only basic tastes: sweet, sour, salty, bitter and umami.14 So on the palate a taster first judges not 'what fruit' but the wine's structure: sweetness, acidity, tannin, alcohol and body.13
Sweetness comes from residual sugar. Most wines have so little that you cannot taste it, usually 2 to 3 g/L.1 Under EU rules a still wine may be called dry with up to 4 g/L of sugar (up to 9 g/L if acidity is high enough).15
You judge acidity by saliva: the more and the longer your mouth waters, the higher the acidity.16 Tannins bind to proteins in saliva, so the mouth feels dry and rough.17 They come from skins, seeds and stems,1 and oak can add more.17
Alcohol is felt as warmth and weight.17 Body is the overall sense of weight built from all these elements: think of water next to a creamy milkshake.17 Alcohol, sugar and glycerol all add body.1
Sweetness
from: grape sugar left unfermented
Acidity
from: the berry's tartaric and malic acid
Tannin
from: skins, seeds, stems, oak
Alcohol
from: yeast fermenting sugar
Body
from: alcohol, sugar, glycerol and tannin together
Chapter 6
Why can wine smell of strawberry or pepper?
Wine rarely smells of grapes; Muscat varieties are the well-known exception.18 If a wine smells of peach or green pepper, it contains the same compound as the peach or the pepper. That is chemistry, not imagination.14
Primary aromas are those of the grape and of alcoholic fermentation: flowers, fruit, berries, herbs.13 Some are already in the berry, some are released from precursors during fermentation, and fruity esters smelling of apple, pineapple and banana are born in the fermenting juice itself.18
Secondary aromas come from winemaking after fermentation: from yeast lees (biscuit, bread), from malolactic conversion (butter) and from oak (vanilla, cloves, coconut).13
Tertiary aromas come with maturation and time: dried fruit, leather, earth and mushroom in reds; honey, nuts and sometimes petrol in whites.13 Fresh aromas lose intensity over time, and some wines develop new ones.18
- Primarygrape and fermentation
- Secondarywinemaking after fermentation
- Tertiarymaturation
5 chapters
Where wine comes from
Chapter 7
What is a grape variety?
A grape variety is like a dog breed. Each one has an entry in the Vitis International Variety Catalogue (VIVC): species, berry colour, country of origin and other names.19
Varieties have parents. Cabernet Sauvignon is the offspring of Cabernet Franc and Sauvignon Blanc, proven by DNA analysis in 1997.20
The variety sets much of the aroma. Sauvignon Blanc, Cabernet Franc and Cabernet Sauvignon are known for green notes of bell pepper and tomato leaf, which come from methoxypyrazines.14 Gewürztraminer is recognised by its smell of rose and lychee.14
The chart shows the eight largest atlas varieties by vineyard area worldwide in 2015. The largest of them is Cabernet Sauvignon.21
Chapter 8
How does a vine spend its year?
From leaf fall to spring the vine is dormant: nothing is left but woody parts.22 As it warms up, stored starch turns into sugar and sap starts to move.22
Then shoots grow fast, flower clusters appear and the vine flowers. In warm dry weather flowering can take a day or two, in cool wet weather up to a month.22
About five to seven weeks after the berries set, véraison begins: the berries soften and start to store sugar.22 This is when they take on their variety's colour.23 Over the next four to six weeks sugar, pigments and aromas go up while acids go down.22
In the Northern Hemisphere grapes usually ripen in September, in the Southern in March.24
- Brix
- A measure of sugar in juice: one degree is one gram of sugar per 100 grams of juice.25
Chapter 9
Where do grapes grow?
In 2025 the world's vineyards covered 7.0 million hectares.26 Spain has the most vines, 919,000 hectares, ahead of France with 740,000.26
The regions of our atlas lie roughly between 30 and 50 degrees of latitude, north or south of the equator. On the map these are the two pale bands, the wine belts.
Even within these belts warmth varies a lot. Over 1950 to 1999 the average growing season temperature was 13.0 °C in the Mosel Valley and 19.9 °C in the Barossa Valley in Australia.27
- Growing season
- The warm part of the year when the vine grows: for calculations, April to October in the north and October to April in the south.27
Chapter 10
Why does climate change the taste of wine?
Sugar in the berry is future alcohol: yeast turns it into ethanol.1 So warmth decides not only ripeness but also how strong the wine will be.27
In cooler regions grapes ripen more slowly and keep more natural acidity; Chablis and the Mosel are classic examples.16 The warmer the nights in late summer and autumn, the more acid the berry loses to respiration.28
When it is too hot for a variety, the vine runs through its stages faster: sugar is ready early, and while the grower waits for flavours, acidity is lost. The result is a wine high in alcohol and low in freshness.27 High alcohol and low acidity are already named among the effects of warming on Australian vineyards.29
Climate changes aroma as well. In cool climates, in shade or with early picking, Sauvignon Blanc and the Cabernets show stronger green notes, because less ripe grapes hold more methoxypyrazines.14
- Methoxypyrazines
- Compounds that smell of green pepper and grass; less ripe grapes have more of them.14
Chapter 11
What does soil give to wine?
Soil acts on the vine mainly through water and nitrogen. A review of terroir research found little evidence that soil minerals are a major driver of terroir.30
How much water reaches the roots depends largely on soil texture: about 5% available water in a very sandy soil against about 10% in a very clayey one.30
So a 'taste of stone' in the glass is more metaphor than chemistry. Inorganic matter is about 0.2% of a wine, and it is nearly tasteless.9
- Terroir
- The conditions of a place: climate, soil, relief. Within it, soil acts on the vine mainly through water and nitrogen.30
3 chapters
How it is made
Chapter 12
What happens in the winery?
First comes the picking date: growers track sugar, acidity and pH.31 Sugar is measured in degrees Brix, grams of sugar per 100 grams of juice.25
The berries are crushed to release the must. For white wine they are pressed straight away, slowly and gradually; for red, after fermentation.6,32 Yeast ferments the sugar.7
Often a further, malolactic fermentation follows: Oenococcus oeni bacteria turn malic acid into lactic acid, and the wine softens.33,34
In an oak barrel the wine takes in a little oxygen, 5 to 45 mg/L a year depending on the study, and compounds from the wood.35 A new oak barrel can give the wine a vanilla aroma.18
Chapter 13
How do white and red differ in the winery?
The key difference is when the skins come off. For white wine the berries are usually pressed right after crushing, and only the clear juice ferments.32,11
Red wine ferments with its skins and is pressed only after fermentation; all that time the skins give the wine colour.11 Along with colour, tannins pass from the skins and seeds into the wine.1
Almost all red wines and many whites go through malolactic conversion: they contain lactic acid made from malic acid.16 Some producers deliberately block it to keep bright acidity.16
- Pressing
- Separating juice or wine from skins and seeds; before fermentation for white, after it for red.32
White
- Picking
- Crushing
- Pressing
- Juice ferments
- Ageing
- Bottling
Red
- Picking
- Crushing
- Ferments on skins
- Pressing
- Malolactic
- Ageing
- Bottling
Chapter 14
Why are wines so different?
The same must can become very different wines. Here are four techniques and processes that change the style the most.
There is a fifth, simpler one: add alcohol. That is how fortified wines are made, at 15 to 22% by volume.1 Sweet wines can be very sweet: Sauternes can have 150 g/L of sugar, Pedro Ximénez sherry up to 400 g/L.1
Noble rot
In Tokaj, aszú berries shrivel on the vine under the fungus Botrytis cinerea. Their sugar must read at least 45% on a refractometer.38
A veil of yeast
In Jerez some wines (fino, manzanilla) are aged under the velo de flor, a living film of yeast on the surface of the wine.39
Time in wood
Red Rioja Reserva spends at least a year in oak,40 Barolo at least 18 months in wood.41
2 chapters
Wine and you
Chapter 15
What does the bottle tell you?
In the EU a wine label must show the actual alcoholic strength, the provenance and who bottled the wine.42 Strength is given in whole or half percent, followed by '% vol'.15
Vintage and variety are optional.42 But if a vintage is shown, at least 85% of the grapes must come from that year; if a single variety is named, it must make up at least 85%.15
Above 10 mg/L of sulphur dioxide, sulphites count as an allergen and must be declared.43 The warning is the word 'contains' followed by the substance, as in 'contains sulphites'.42
Even the bottle size is set by law. In the EU, between 100 and 1,500 ml, still wine may be sold in only eight volumes and sparkling wine in five.44
Chapter 16
How do you taste wine?
The WSET Systematic Approach to Tasting has four parts: appearance, nose, palate and conclusions.13 It is an order of steps, not an exam: even on the courses the list of descriptors is a prompt you do not need to memorise.45
Pour only a little: you cannot swirl a full glass. Swirling mixes the aromas with air so they reach your nose; it is easiest with the glass kept on the table.46
Take a small sip and draw a little air through the wine. Most of what we call taste we actually smell: aromas rise to the nose through the back of the throat.46 Notice whether your mouth waters (that is acidity) and whether it dries (that is tannin).16,17
Temperature matters too. 'Room temperature' for wine means 15 to 18 °C, cooler than a normal room; a full-bodied white needs only light chilling to 10 to 13 °C, and below 6 °C the cold masks the flavours of white, rosé and sparkling wines.47
1
Look
clarity, intensity and colour: lemon to amber for whites, purple to brown for reds
2
Swirl and smell
is the smell clean, how strong is it, what does it remind you of
3
Sip
sweetness, acidity, tannin, alcohol, body and length of finish
4
Conclude
do you like it, and how well is the wine made
Test yourself
-
1 / 8
What is there most of in wine?
Water makes up about 85% of the volume of wine.1
-
2 / 8
Where does red wine get its colour?
Colour comes from the skins; the juice is usually colourless.11
-
3 / 8
What sign in the mouth points to high acidity?
The more and the longer the mouth waters, the higher the acidity.16
-
4 / 8
What do tannins feel like?
Tannins bind to saliva proteins and dry the mouth.17
-
5 / 8
In which aroma layer does WSET place vanilla from oak?
In the WSET lexicon oak sits among the secondary aromas, those of winemaking after fermentation.13
-
6 / 8
What usually happens to grape acidity in a climate that is too hot?
In the heat sugar is ready early and acidity is lost through respiration.27
-
7 / 8
What does malolactic fermentation do?
Oenococcus oeni bacteria turn malic acid into lactic acid.33
-
8 / 8
If an EU label names a single variety, how much of it must the wine contain?
A single named variety must make up at least 85%.15
Beginner's glossary
The words you will meet most often in the atlas, one sentence each.
- Must
- The juice released when the berry skins are broken during crushing.6 Crushing and pressing
- Alcoholic fermentation
- The conversion of grape sugars into ethanol, carbon dioxide and by-products.7 Alcoholic fermentation
- Yeast
- The microorganisms of fermentation; Saccharomyces cerevisiae usually dominates.4 Alcoholic fermentation
- % abv
- Alcohol by volume: 12% abv means 12% of the wine is alcohol.1 Label decoder
- Residual sugar
- Unfermented sugar left in the wine; usually 2 to 3 g/L in dry wines.1 Label decoder
- Dry wine
- A still wine with no more than 4 g/L of sugar (up to 9 g/L with enough acidity).15 Label decoder
- Glycerol
- A by-product of fermentation, usually 1 to 15 g/L; it adds smoothness.5,1 Alcoholic fermentation
- Acidity
- The freshness of a wine, recognised by a watering mouth.16 Malolactic fermentation
- Tannins
- Compounds from skins, seeds, stems and oak that dry the mouth.1,17 Oak ageing
- Anthocyanins
- Skin pigments that make red wine red.1 Crushing and pressing
- Body
- The sense of weight in the mouth, the sum of alcohol, sugar, tannin and other elements.17 Compare grapes
- Primary aromas
- Aromas of the grape and of alcoholic fermentation.13 Aroma molecules
- Secondary aromas
- Aromas of winemaking after fermentation: yeast lees, malolactic conversion, oak.13 Aroma molecules
- Tertiary aromas
- Aromas of maturation: dried fruit, mushroom, honey, nuts.13 Aroma molecules
- Methoxypyrazines
- Compounds that smell of green pepper; less ripe grapes have more of them.14 Aroma molecules
- Véraison
- The start of ripening, when berries soften, change colour and store sugar.22 The vine's year
- Malolactic fermentation
- The conversion of malic acid into lactic acid by bacteria, above all Oenococcus oeni.33 Malolactic fermentation
- Bordeaux barrel
- The classic 225-litre oak barrel.35 Oak ageing
- Sparkling wine
- Wine with its own carbon dioxide at a pressure of at least 3.5 bar at 20 °C.36 Traditional method
- Fortified wine
- Wine with added alcohol, usually 15 to 22% by volume.1 Jerez-Xérès-Sherry
- Vintage
- The harvest year; in the EU at least 85% of the grapes must come from that year.15 Label decoder
Sources
- What is wine? (Lucy Stevenson DipWSET). Wine & Spirit Education Trust (WSET), 2021. level 4
- International Code of Oenological Practices, I.3.1 Basic definition (wine). OIV, n.d.. level 2
- Le vin, subtile alliance de l'alcool, du sucre et de l'acide. Dujon P., Colard-Thomas J. CultureSciences-Chimie, École normale supérieure, 2016. level 4
- Microbial Resources and Enological Significance: Opportunities and Benefits (Petruzzi et al., Frontiers in Microbiology 8:995). Frontiers in Microbiology, 2017. level 3
- Scanes K. T., Hohmann S., Prior B. A. Glycerol production by the yeast Saccharomyces cerevisiae and its relevance to wine: a review. S. Afr. J. Enol. Vitic. 19(1): 17-24. South African Journal of Enology and Viticulture, 1998. level 3
- International Code of Oenological Practices, II.1.2 Crushing. OIV, n.d.. level 2
- International Code of Oenological Practices, II.2.3 Alcoholic fermentation. OIV, n.d.. level 2
- Instrumental and sensory approaches for the characterization of compounds responsible for wine aroma (Chem Biodivers 5:1170-83). Barbe JC, Pineau B, Ferreira AC, 2008. level 3
- On rocky ground: The science of soil and wine taste (Prof. Alex Maltman). Decanter, 2018. level 4
- Basic Grape Berry Structure (William McGlynn, Oklahoma State University; reviewed by Sara Spayd, NC State, and Jim Wolpert, UC Davis). eXtension Grapes (Cooperative Extension), 2019. level 4
- What determines the colour of wine?. Wine & Spirit Education Trust (WSET), 2021. level 4
- Champagne and its grape varieties. Comité Champagne, n.d.. level 4
- WSET Level 2 Systematic Approach to Tasting Wine and Wine-Lexicon, Issue 2. Wine & Spirit Education Trust (WSET), 2023. level 4
- Strawberry, pepper and petrol: why wine smells the way it does (Deniz Bayram DipWSET). Wine & Spirit Education Trust (WSET), 2026. level 4
- Commission Delegated Regulation (EU) 2019/33 (consolidated text 08.12.2023), Articles 40-58 and Annexes I, III, VI. European Commission (EUR-Lex), 2023. level 1
- Understanding acidity in wine (Martin Green). Wine & Spirit Education Trust (WSET), 2026. level 4
- The secret language of wine: what is mouthfeel? (Heather Dougherty DipWSET). Wine & Spirit Education Trust (WSET), 2026. level 4
- Why doesn't wine taste like grapes? (Lucy Stevenson DipWSET). Wine & Spirit Education Trust (WSET), 2022. level 4
- Vitis International Variety Catalogue (VIVC) – passport data. Julius Kühn-Institut (JKI), Geilweilerhof, 2026 (accessed 2026-10-13). level 2
- Bowers J. E., Meredith C. P. The parentage of a classic wine grape, Cabernet Sauvignon. Nature Genetics 16, 1997. level 3
- Focus OIV 2017: Distribution of the world's grapevine varieties. OIV, 2017. level 2
- Annual Cycle of the Grapevine (William Nail, Connecticut Agricultural Experiment Station; reviewed by W. Shoemaker and E. Stafne). eXtension Grapes (Cooperative Extension), n.d.. level 4
- Growth stages of mono- and dicotyledonous plants. BBCH Monograph (ed. U. Meier), section 1.3.17: Phenological growth stages and BBCH-identification keys of grapevine (Vitis vinifera L. ssp. vinifera), Lorenz et al.. Julius Kühn-Institut (JKI), Quedlinburg, 2018. level 4
- A multicriteria climatic classification system for grape-growing regions worldwide (J. Tonietto, A. Carbonneau), Agricultural and Forest Meteorology 124: 81–97. Agricultural and Forest Meteorology (Elsevier); PDF via Embrapa Alice repository, 2004. level 3
- Evaluating Cold Hardy Wine Grape Maturity (A4154), Atucha & van Zoeren. University of Wisconsin-Extension, 2018. level 4
- State of the World Wine Sector in 2025. International Organisation of Vine and Wine (OIV), 2026. level 2
- Climate and Wine: Quality Issues in a Warmer World (G.V. Jones, M.A. White, O.R. Cooper, K. Storchmann); manuscript summarising the Jones et al. analysis of 27 wine regions, 1950–1999. Southern Oregon University / author's site climateofwine.com, n.d.. level 4
- Klimafolgenmonitoring Hessen, Indikator-Kennblatt: Weinbau - Reifeentwicklung und Weininhaltsstoffe. Hessisches Landesamt für Naturschutz, Umwelt und Geologie (HLNUG); data RP Darmstadt, Dezernat Weinbau Eltville, 2017. level 4
- Rogiers S. Y. et al. Impact of climate change on grape berry ripening: an assessment of adaptation strategies for the Australian vineyard. Front. Plant Sci. 13: 1094633. Frontiers in Plant Science (PMID 36618637), 2022. level 3
- Soil-related terroir factors: a review (van Leeuwen, Roby, de Rességuier, OENO One 52(2):173-188). OENO One, 2018. level 3
- 2025 Post-Veraison in Pennsylvania – October 7 (Hickey, Kwasniewski, Kelly, Centinari). Penn State Extension, 2025. level 4
- International Code of Oenological Practices, II.1.5 Pressing. OIV, n.d.. level 2
- Genome-Scale Reconstruction of the Metabolic Network in Oenococcus oeni to Assess Wine Malolactic Fermentation (Mendoza et al., Frontiers in Microbiology 8). Frontiers in Microbiology, 2017. level 3
- International Code of Oenological Practices, II.3.1.2.3 Microbiological de-acidification by lactic acid bacteria. OIV, n.d.. level 2
- Oxygen gas transfer through oak barrels: a macroscopic approach (Junqua, Zeng, Pons, OENO One 55(3)). OENO One, 2021. level 3
- International Code of Oenological Practices, I.4.4 Sparkling wines. OIV, n.d.. level 2
- Modifications du cahier des charges de l'AOP « Champagne » (draft approved by INAO national committee, 11 Sept 2024). INAO, 2024. level 1
- TOKAJ termékleírás (OEM product specification), 2020. Agrárminisztérium (Hungary), boraszat.kormany.hu, 2020. level 1
- Pliego de condiciones de la DOP « Jerez-Xérès-Sherry » (consolidado según Orden de 4 de octubre de 2022, BOJA núm. 195). Consejo Regulador de las DD.OO. Jerez-Xérès-Sherry, Manzanilla-Sanlúcar de Barrameda y Vinagre de Jerez, 2022. level 1
- Classification. Consejo Regulador DOCa Rioja, n.d.. level 1
- Barolo DOCG — Production regulations (English translation of the disciplinare). Consorzio di Tutela Barolo Barbaresco Alba Langhe e Dogliani, 2019. level 1
- Regulation (EU) No 1308/2013 establishing a common organisation of the markets in agricultural products (consolidated text 08.12.2023), Articles 112, 118-122. European Parliament and Council of the EU (EUR-Lex), 2023. level 1
- Regulation (EU) No 1169/2011 on the provision of food information to consumers, Articles 9, 13, 16, 23 and Annex II. European Parliament and Council of the EU (EUR-Lex), 2011. level 1
- Directive 2007/45/EC laying down rules on nominal quantities for prepacked products, Annex. European Parliament and Council (EUR-Lex), 2007. level 1
- WSET Level 3 Systematic Approach to Tasting Wine and Wine-Lexicon, Issue 2. Wine & Spirit Education Trust (WSET), 2022. level 4
- How to taste wine? A guide to tasting wine (Pauline O'Connor DipWSET). Wine & Spirit Education Trust (WSET), 2023. level 4
- Ideal serving temperatures and top tips for wine storage. Wine & Spirit Education Trust (WSET), 2022. level 4
- Ancient Georgian traditional Qvevri wine-making method. UNESCO Intangible Cultural Heritage, 2013. level 2
Sources checked 2026-10-13.