Section 2 · Factors Affecting the Style, Quality and Price of Wine

White and Sweet Winemaking

White winemaking is often described as simpler than red, but that undersells it. The choices a winemaker makes, from how quickly the grapes are pressed, to whether the juice ferments in steel or oak, to how the lees are handled, determine whether the finished wine is crisp and aromatic, rich and complex, or lusciously sweet. This chapter covers the entire process from grape to glass for white wines, and then explores the fascinating world of sweet winemaking, where nature and human ingenuity combine to concentrate sugar in extraordinary ways.

Aroma kit focus: lime, green apple, peach, honey, apricot, vanilla, toast, petrol

Why White Winemaking Is Different

The fundamental difference between white and red winemaking is when pressing happens. In red winemaking, the juice stays in contact with the grape skins during fermentation to extract colour, tannin, and flavour. In white winemaking, the juice is usually separated from the skins before fermentation begins. This is why white wines are pale, low in tannin, and dominated by fruit and floral aromas rather than the structural, grippy character of reds.

Because white wines lack the protective tannins and colour compounds that reds have, they are more vulnerable to oxidation. This means white winemaking generally involves more careful handling to preserve freshness and prevent browning, though some styles deliberately embrace a degree of oxidation for complexity.

Key principle: White winemaking is largely about protection, protecting delicate aromas, preserving acidity, and preventing unwanted oxidation. Every step, from harvest to bottling, reflects this priority.

The White Winemaking Process: Step by Step

1. Harvesting

White grapes are often harvested earlier than red grapes to preserve acidity, a critical component of balance in white wines. Many producers harvest in the cool early morning hours to keep the grapes as cold as possible, which slows oxidation and prevents premature fermentation.

Machine vs hand harvest: Machine harvesting is common for large-volume, inexpensive white wines. Hand harvesting is preferred for premium wines, especially when whole-bunch pressing is used (since machines crush the grapes, releasing juice that may oxidise before reaching the winery).

2. Pressing

In white winemaking, the grapes are pressed before fermentation. The goal is to separate the juice from the skins, seeds, and stems as gently as possible.

Whole-bunch pressing is the gentlest method: entire bunches of grapes are loaded into the press without being crushed first. This reduces the risk of oxidation and can produce wines with more purity and delicacy.

Some winemakers crush and destem before pressing, which is faster and more efficient but can release more phenolic (bitter/astringent) compounds from the skins and seeds.

As pressing continues, the juice quality changes. The first juice to emerge (the free-run juice) is the lightest and most delicate. As more pressure is applied, the juice becomes coarser, with more bitter and astringent compounds. Winemakers may separate the wine from different stages of pressing (called press fractions) and use them selectively in the final blend.

3. Skin Contact (Optional)

In most white winemaking, the juice spends little time in contact with the skins to reduce the risk of oxidation and keep flavours clean. However, some winemakers deliberately allow a short period of skin contact before pressing, typically a few hours at a cool temperature.

Why do it: Skin contact can increase flavour intensity and aromatic complexity, extracting more varietal character from the skins. This is sometimes used for aromatic varieties like Gewürztraminer or Muscat.

Why avoid it: It increases the risk of oxidation and can extract unwanted bitter or astringent phenolic compounds. For wines intended to show pure varietal character with crisp freshness, minimal skin contact is preferred.

4. Must Clarification (Settling)

After pressing, the juice (called must) is cloudy with fragments of grape skin, pulp, and other solids. If fermented in this state, unpleasant aromas can develop and the fermentation may stop prematurely.

The juice is therefore clarified before fermentation begins. The most common methods are:

  • Settling (débourbage): the juice is left in a tank for several hours (often overnight) at a cool temperature. Solids sink to the bottom and the clear juice is racked off the top. This is the most common method.
  • Centrifugation: a machine spins the juice to separate solids mechanically. Faster but less gentle.
  • Fining and filtration: agents can be added to help solids clump together and settle out.

Some winemakers choose to retain a small amount of fine solids in the juice. This makes the finished wine less susceptible to oxidation and can add complexity and a richer texture. However, the risk of off-flavours increases, so this technique is not common for wines intended to show pure varietal character.

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Exam Angle

If the exam asks you to describe white winemaking, always mention that pressing happens before fermentation: this is the defining difference from red winemaking. Then explain the key decisions: skin contact, clarification, fermentation vessel, temperature, and lees contact.

Fermentation: Vessel, Temperature, and Yeast

Fermentation Vessel

The choice of fermentation vessel has a profound impact on the style of the finished wine. There are two main options:

Stainless Steel Tanks

The most widely used vessel for white wine fermentation worldwide. Stainless steel is inert, it does not add any flavour to the wine. It is easy to clean, allows precise temperature control (via cooling jackets built into the tank walls), and is ideal for producing wines where pure fruit character and freshness are the priority.

Best for: Aromatic varieties (Sauvignon Blanc, Riesling, Gewürztraminer), crisp unoaked styles, high-volume commercial wines.

Examples: Marlborough Sauvignon Blanc, Alsace Riesling, most Pinot Grigio.

Oak Barrels

Fermenting in oak barrels (typically 225-litre barriques) produces a fundamentally different style of wine. The oak contributes flavour compounds (vanilla, toast, spice, cedar) and allows a small amount of oxygen exchange through the wood, which softens the wine and adds complexity.

Barrel fermentation also creates a more integrated oak character than simply ageing a steel-fermented wine in oak afterwards. Because the yeast activity during fermentation binds the oak flavours into the wine's structure, the result feels more seamless and less "oaky."

New vs old oak: New barrels contribute the most flavour. Older barrels (used for two or three previous vintages) impart progressively less flavour but still provide the benefits of micro-oxygenation and texture. Many winemakers use a mix of new and old barrels.

Best for: Full-bodied Chardonnay, white Bordeaux blends, premium Viognier, some Chenin Blanc.

Examples: White Burgundy, Pessac-Léognan dry whites, Napa Chardonnay.

Other Vessels

Concrete vats: increasingly popular. They allow slow, gentle oxygen exchange (like oak) but without adding flavour. Concrete also provides good natural temperature stability. Winemakers who want texture and complexity without oak character favour concrete.

Large old oak vessels (foudres): big old wooden barrels that are flavour-neutral (the wood is too old to contribute flavour) but allow micro-oxygenation. Traditional in Alsace and parts of Germany and Austria.

Fermentation Temperature

Temperature control is one of the most important tools in white winemaking. The optimum temperature for white wine fermentation is between 12°C and 22°C (54°F and 72°F).

The connection: Stainless steel makes temperature control easy (built-in cooling systems). Oak barrels are much harder to cool, they are small and sit in cellars, so temperature control relies on cellar temperature and the natural insulation of the barrel. This is one reason barrel fermentation tends to produce richer, more complex wines: the fermentation naturally runs slightly warmer.

Yeast Selection

The winemaker can choose between relying on the various ambient yeast strains found on the grape skins and in the winery, or adding a cultured yeast strain to the must.

Post-Fermentation Decisions

Malolactic Conversion (MLF)

Malolactic conversion (also called malolactic fermentation or MLF) is a secondary process where bacteria convert sharp malic acid (think green apples) into softer lactic acid (think milk). It also produces a compound called diacetyl, which gives a buttery flavour.

In white winemaking, MLF is a stylistic choice, not automatic:

Lees Contact and Bâtonnage

After fermentation finishes, dead yeast cells settle to the bottom of the vessel. This sediment is known as the lees. The fine lees (the very small particles) are the most important.

Keeping the wine in contact with the fine lees (sur lie ageing) can have several beneficial effects:

Bâtonnage (lees stirring) is the practice of stirring the lees back into suspension, usually with a stick (bâton) inserted through the barrel's bung hole. This increases the contact between the wine and the lees, intensifying the textural and flavour effects. It is most commonly used for barrel-fermented Chardonnay and white Bordeaux blends.

Muscadet example: The classic white wine of the Loire Valley, Muscadet, is often labelled sur lie, meaning it was aged on its lees before bottling. This transforms what would otherwise be a very simple, neutral wine into something with noticeably more texture and interest. This is a great illustration of how lees contact can elevate a wine's quality.

Oak Maturation (Post-Fermentation)

Even wines fermented in stainless steel can be transferred to oak barrels for maturation after fermentation. However, the oak character in these wines tends to feel more applied, like a layer sitting on top of the wine, compared to the more integrated character of barrel-fermented wines.

As an alternative to barrels, some producers use oak staves or chips added to stainless steel tanks. This is a much cheaper way to add oak flavour, and is common for everyday commercial wines. The flavour is less subtle, but the cost savings are significant. Oak alternatives are not permitted for wines in many European PDO categories.

Blending

Many white wines are blends, either of different grape varieties, different vineyard parcels, or different lots fermented in different ways (for instance, one portion in steel and another in oak). Blending allows the winemaker to balance freshness, body, complexity, and fruit character. Classic examples include Bordeaux whites (Sauvignon Blanc + Sémillon) and Rhône whites (Viognier, Marsanne, Roussanne in various combinations).

Clarification and Stabilisation

Most white wines undergo some form of fining or filtration to improve clarity and stability before bottling. Fining agents bind to unwanted particles and settle out, while filtration physically removes them.

Some producers choose minimal intervention, bottling with little or no fining or filtration. This can preserve more complexity, but increases the risk of faults developing in bottle.

How Winemaking Choices Create Different White Wine Styles

The same grape variety can produce dramatically different wines depending on the winemaking decisions. Understanding this chain of cause and effect is fundamental to the exam.

Decision Crisp, Aromatic Style Rich, Complex Style
Skin contact Minimal or none Short skin contact possible
Fermentation vessel Stainless steel Oak barrels
Temperature Cool (12–16°C) Warmer (16–22°C)
MLF Blocked Encouraged (full or partial)
Lees contact Little or none Extended, with bâtonnage
Oak character None Vanilla, toast, spice, cedar
Resulting style Fresh, fruity, floral, light-bodied Creamy, toasty, full-bodied, complex
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Exam Tip

Chardonnay is the classic exam grape for illustrating this spectrum because it is made in both styles worldwide. If asked to compare an unoaked Chablis with an oaked Napa Chardonnay, use this table as your framework: same grape, completely different winemaking, completely different wine.

Sweet Winemaking

Sweet wines contain residual sugar: sugar that remains in the wine after fermentation. There are several fundamentally different ways to produce sweet wine, and the exam expects you to know all of them. The method used has a direct impact on the style, quality, and price of the finished wine.

The key question: To make a sweet wine, you need either (a) grapes with so much sugar that the yeast cannot ferment it all, (b) a way to stop fermentation before all the sugar is consumed, or (c) a way to add sweetness after fermentation. Every sweet winemaking method is a variation on one of these three approaches.

Late Harvest

The simplest method. Grapes are left on the vine beyond the normal harvest date, allowing them to accumulate more sugar. As grapes hang longer, water evaporates and sugar concentrates. The resulting wines have naturally high sugar levels, and fermentation may stop before all the sugar is consumed (because the yeast runs out of nutrients or the alcohol level becomes toxic to it).

Risks: Leaving grapes on the vine increases the danger of rot, bird damage, and autumn rain diluting the fruit. It also represents a gamble, if the weather turns bad, the entire crop can be lost.

Label terms: Vendange tardive (France/Alsace), Spätlese and Auslese (Germany/Austria), Late Harvest (New World).

Style: Medium to high sweetness, good varietal character preserved, typically lighter and fresher than botrytis wines.

Noble Rot (Botrytis Cinerea)

Noble rot is a very specific, beneficial form of the fungus Botrytis cinerea. Under the right conditions, morning mist or humidity followed by warm, dry afternoons: the fungus penetrates the grape skin without breaking it, creating tiny holes that allow water to evaporate. The result is shrivelled, raisin-like grapes with incredibly concentrated sugar, acid, and flavour compounds.

Botrytis also adds its own unique flavour compounds to the wine, giving characteristic notes of honey, marmalade, candied citrus peel, saffron, ginger, and dried apricot. These flavours cannot be achieved by any other method.

Critical conditions: Botrytis needs alternating humidity and dryness. If it stays too wet, the fungus causes destructive grey rot instead, which ruins the grapes. This is why botrytis wines can only be made reliably in specific locations with the right microclimate (typically near rivers that produce morning fog).

Harvesting: Affected grapes must be picked by hand in multiple passes (tries) through the vineyard, selecting only the berries at the optimal stage of botrytis each time. This is extremely labour-intensive and expensive.

Yields: Because the grapes lose so much water, yields are tiny, sometimes as low as one glass of wine per vine. This, combined with the labour cost, is why botrytis wines are expensive.

Key regions: Sauternes and Barsac (Bordeaux), Tokaji (Hungary), the Rhine and Mosel (Germany, Beerenauslese and Trockenbeerenauslese), Alsace (Sélection de Grains Nobles), Loire Valley (Bonnezeaux, Quarts de Chaume).

Drying Grapes (Passito / Appassimento)

Grapes are harvested healthy and then dried after picking, either on straw mats, hanging from rafters, or in special drying rooms with controlled ventilation. As the grapes dehydrate, sugar concentrates in the remaining juice.

This technique is independent of weather conditions during the growing season, the drying happens under the winemaker's control, so it is more reliable than noble rot or late harvest.

Flavour profile: Dried fruit, fig, raisin, honey, caramel. These wines tend to have a rich, almost raisiny character that distinguishes them from botrytis wines.

Key examples: Vin Santo (Tuscany, from Trebbiano and Malvasia), Recioto della Valpolicella (Veneto, from Corvina, a sweet red), and Recioto di Soave (Veneto, from Garganega). The technique is also used for the dry wine Amarone della Valpolicella, where the concentrated juice is fermented fully to dryness.

Freezing Grapes (Ice Wine / Eiswein)

Grapes are left on the vine into winter until they freeze naturally on the vine. When pressed while still frozen, the ice (water) stays behind in the press as solid crystals, and only the highly concentrated, sugary juice flows out.

Critical requirement: The temperature must drop to at least −7°C (19°F) for the grapes to freeze sufficiently. Grapes must be pressed while still frozen, often requiring harvest in the middle of the night.

Flavour profile: Very high acidity and very high sweetness, giving these wines a piercing, electric quality. Flavours of stone fruit, tropical fruit, citrus, and honey. The acidity is what distinguishes ice wine from other sweet styles, it never tastes cloying.

Key regions: Canada (Niagara Peninsula, the world's largest producer), Germany, and Austria. Canadian ice wine uses primarily Vidal (a hybrid) and Riesling. German Eiswein is typically Riesling.

Why it's expensive: Enormous risk (the grapes may rot before they freeze, or the freeze may never come), tiny yields, and labour-intensive night-time harvesting.

Fortification (Stopping Fermentation)

Sweet wines can be made by adding grape spirit (high-strength brandy) to the fermenting wine, which raises the alcohol level high enough to kill the yeast before all the sugar has been consumed. The unfermented sugar remains in the wine as residual sweetness.

This is the method used for sweet fortified wines like Port, sweet Sherry, and Vin Doux Naturel (such as Muscat de Beaumes-de-Venise and Banyuls). Fortified wines are covered in detail in Section 5 of the course.

The key point: The earlier in fermentation you add the spirit, the sweeter the wine will be (more sugar remains). The later you add it, the drier and more alcoholic the wine will be.

Adding Süssreserve

Süssreserve is unfermented grape juice that is held back before fermentation, preserved (usually by chilling and adding SO₂), and then blended back into the dry wine after fermentation is complete. This adds sweetness without relying on stopping fermentation.

Where it's used: Primarily in Germany for mass-produced, off-dry to medium-sweet wines. It is a simple, reliable, and inexpensive way to achieve a desired sweetness level.

Advantages: Precise control over the final sugar level. The winemaker can ferment the wine completely dry and then add exactly the right amount of süssreserve to reach the target sweetness.

Disadvantage: The sweetness can taste somewhat disconnected from the wine rather than integrated. It is generally not used for premium wines.

Stopping Fermentation (without Fortification)

There are also non-fortification ways to stop fermentation before all the sugar is consumed:

  • Chilling: dropping the temperature below about 5°C (41°F) temporarily halts the yeast. The wine can then be filtered to remove the yeast entirely.
  • Adding SO₂: sulphur dioxide can kill the yeast, though the dosage required can be high.
  • Sterile filtration: physically removing the yeast through very fine filters.

In practice, winemakers often combine these methods. For example, chilling to stop fermentation, then sterile filtering to ensure it cannot restart in bottle.

Sweet Winemaking Methods Compared

Method How Sugar Concentrates Distinctive Character Key Examples
Late harvest Extended hang time on vine Ripe fruit, moderate complexity Alsace Vendange Tardive, German Spätlese/Auslese
Noble rot Botrytis dehydrates berries + adds compounds Honey, marmalade, saffron, extreme concentration Sauternes, Tokaji Aszú, TBA
Drying grapes Post-harvest dehydration Dried fruit, raisin, fig Vin Santo, Recioto
Freezing Ice crystals separate water from sugar Electric acidity, stone fruit, piercing sweetness Canadian Icewine, German Eiswein
Fortification Spirit stops fermentation early High alcohol + sweetness, rich and warming Port, Muscat de Beaumes-de-Venise
Süssreserve Unfermented juice added back Simple, grapey sweetness German Liebfraumilch

Residual Sugar and the Perception of Sweetness

Residual sugar (RS) is measured in grams per litre (g/L). But the amount of sugar in a wine does not tell the whole story, how sweet a wine tastes depends on the balance between sugar and other components, especially acidity.

General Sweetness Categories
Dry
0–4 g/L RS. Most table wines. No perceptible sweetness.
Off-dry
4–12 g/L RS. A hint of sweetness, often balanced by acidity so it may not taste sweet. Many German Kabinett Rieslings fall here.
Medium-sweet
12–45 g/L RS. Noticeably sweet. German Spätlese, some Vouvray.
Sweet
45+ g/L RS. Clearly sweet. Sauternes, Tokaji, ice wine. Some botrytis wines exceed 200 g/L.

Why Acidity Matters

A wine with high residual sugar can taste balanced and refreshing if it also has high acidity. A wine with moderate sugar but low acidity can taste cloying and heavy. This is why Riesling makes such exceptional sweet wines, the variety naturally maintains very high acidity even at extreme sugar levels, creating the tension between sweetness and freshness that makes great sweet wines so compelling.

Conversely, a wine like cheap white Zinfandel may have a similar sugar level to a German Spätlese but taste much sweeter because it lacks the acidity to balance it.

Exam trap: The exam may present a wine's residual sugar level and ask you whether it tastes sweet. The answer is: it depends on acidity. A Riesling with 30 g/L of sugar and high acidity may taste only off-dry, while a Gewürztraminer with 15 g/L and low acidity can taste noticeably sweet. Always discuss the balance between sugar and acidity.

Other Factors Affecting Perception

Producing High-Volume vs Premium White Wines

The exam frequently asks about the differences between inexpensive and premium winemaking. For white wines, the contrast is sharp:

High-Volume, Inexpensive White Wines

  • Machine harvested, high yields
  • Quick mechanical pressing
  • Fermented in large stainless steel tanks at cool temperatures
  • Cultured yeast for consistency
  • No MLF, no lees contact
  • Oak alternatives (staves/chips) if oak character is wanted
  • Early bottling to retain freshness
  • Designed for immediate consumption
  • Varietal fruit purity is the selling point

Premium White Wines

  • Hand harvested, low yields, careful sorting
  • Gentle whole-bunch pressing
  • Barrel fermented (often in a mix of new and old oak)
  • Ambient yeast for complexity
  • Full or partial MLF (for appropriate styles)
  • Extended lees ageing with bâtonnage
  • New oak barrels (expensive but contributes complexity)
  • Longer maturation before release
  • Designed to develop in bottle over years
  • Complexity, length, and texture are the selling points

Key Grape Varieties and Their Winemaking Styles

The textbook highlights Chardonnay, Sauvignon Blanc, Riesling, and Pinot Grigio/Gris as the major internationally important white grapes. Each has a typical winemaking approach, though variations exist everywhere.

Chardonnay

Chardonnay is the chameleon of white grapes, it can be grown and vinified in an enormous range of styles. It is the variety that best illustrates the winemaker's influence.

  • Cool climate, unoaked (Chablis): Stainless steel, cool fermentation, no MLF. Lean, steely, high acidity, mineral character.
  • Cool climate, oaked (Burgundy Côte de Beaune): Barrel fermented, full MLF, bâtonnage. Creamy, toasty, complex, with underlying acidity.
  • Warm climate, oaked (Napa Valley, parts of Australia): Barrel fermented, ripe tropical fruit, butter, vanilla, full body. Rich and opulent.
  • Warm climate, unoaked (many New World regions): Stainless steel, ripe fruit, moderate acidity. Fresh and approachable.

Sauvignon Blanc

Almost always vinified to preserve freshness and aromatic intensity. The dominant winemaking approach worldwide is stainless steel, cool fermentation, no MLF, early bottling. The Fumé Blanc style from California and parts of the Loire (Pouilly-Fumé) may include some oak contact, but this is the exception.

Blending: In Bordeaux, Sauvignon Blanc is frequently blended with Sémillon. The Sauvignon provides acidity and aroma; the Sémillon adds body and richness. The best dry white Bordeaux (Pessac-Léognan) are barrel fermented and aged.

Riesling

Riesling is almost never fermented or aged in oak. It is the purest expression of terroir and varietal character in white wine. The key winemaking decision with Riesling is when to stop fermentation to determine the residual sugar level. The same vineyard can produce wines ranging from bone-dry to intensely sweet depending on this single decision.

Riesling's extraordinarily high natural acidity means even sweet versions taste balanced and refreshing. It is the most age-worthy white grape variety.

Pinot Gris / Pinot Grigio

This grape demonstrates how the same variety can yield very different wines based on winemaking approach.

  • Pinot Grigio style (Italy): Early harvesting, cool stainless steel fermentation, no skin contact, no MLF. Light, crisp, neutral, high acidity, low body. Meant to be drunk young.
  • Pinot Gris style (Alsace): Later harvesting for more ripeness, sometimes with brief skin contact. Richer, fuller-bodied, with more stone fruit and spice character. Can range from dry to sweet.

What the Exam Expects You to Know

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Short Answer Strategy

If asked to explain how a particular white wine style is made, structure your answer as a step-by-step process: harvesting → pressing → clarification → fermentation (vessel + temperature) → MLF (yes/no) → lees contact → maturation → bottling. For each step, explain why that choice was made and how it affects the final wine.

Active Recall Prompts

Close this page and try to answer these from memory: