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Botrytized sweet wine

Also known as Botrytised sweet wine, Noble-rot wine

Botrytized sweet wine is made from ripe grapes affected by the beneficial form of Botrytis cinerea infection known as noble rot. The fungus helps the berries lose water, concentrating their juice, but it also changes grape metabolism and composition. The result is therefore different from simple late harvest or drying: both concentration and fungal transformation shape the wine.

Noble rot is a vineyard condition, not a guarantee of quality or even of sweet wine. The same fungus causes destructive grey rot, also called bunch rot, when infection develops under less favourable conditions. Variety, berry maturity, autumn weather, vineyard exposure, selection at harvest, fermentation, and ageing determine whether botrytized fruit becomes a precise, long-lived wine or an unstable, dull one.

When rot becomes noble

B. cinerea is a pathogen that feeds on grape tissue. On ripe or overripe berries, short humid periods can permit infection while longer dry intervals slow its spread and encourage evaporation. Fungal enzymes weaken the skin, and fine cracks allow the berry to shrivel. Sugar and other dissolved material then become more concentrated because there is less water, not because the fungus manufactures sugar.

The fungus is doing more than perforating a container. A three-year study of naturally infected Sémillon found changes in sugars, sugar alcohols, organic acids, phenolic pathways, terpenes, and aroma precursors; several of the altered compound classes remained distinguishable in the finished wines.[1] Noble rot can therefore modify acidity, texture, colour, and aroma as it concentrates the berry. These effects are not uniform: the fungus consumes some grape compounds, the berry mounts stress responses, and the degree of dehydration changes their final concentrations.

Persistent rain or high humidity instead favours rapid, destructive bunch rot. Fruit may split and support other fungi, yeasts, and bacteria before useful dehydration occurs, bringing oxidation and difficult flavours into the must. The boundary is not set by a single weather measurement. Ripeness, berry integrity, bunch compactness, canopy airflow, cultivar, infection timing, and the wider microbial community all influence the outcome. Scientific comparisons have identified different responses in noble-rotted and bunch-rotted berries, but the mechanisms that send an infection down one path rather than the other are not fully resolved.[1:1]

Harvest and fermentation

Noble rot rarely advances evenly across a vineyard or bunch. Pickers may make several passes, taking suitably shrivelled berries while leaving sound or less advanced fruit to develop. This selection separates desirable concentration from wet or otherwise unhealthy rot and lets a producer choose how much botrytized material enters a wine. It is slow, lowers the volume of juice, and leaves the crop exposed to changing weather; in some years the intended style may not be practical.

The shrivelled berries yield little, viscous juice and can be hard to press. Some traditions ferment that juice directly, while others steep selected berries in must, fermenting must, or wine. A wine may use only strongly affected berries or blend them with sound late-harvest fruit. These choices change the ratio of fungal transformation to simple ripeness and dehydration.

Fermentation and the point at which it stops determine how much grape sugar remains; noble rot does not by itself set the final sweetness. High sugar places yeast under osmotic stress, while the altered nutrients, polysaccharides, enzymes, and microbial population of botrytized must add further complications. Fermentation may proceed slowly or stop with considerable grape sugar remaining. Yeast choice, temperature, clarification, nutrient and sulfur dioxide management, and the decision to arrest and stabilise fermentation all affect alcohol, sweetness, volatile acidity, and aroma. Extremely concentrated must is not automatically better: it can be more difficult to ferment cleanly and may leave a heavier balance.

Character and variation

Botrytized wines share concentration and fungal influence, not a fixed sensory profile. The proportion and stage of affected fruit matter, as do the chemistry of the healthy grapes and the weather that preceded infection. A wine based on Riesling or Chenin Blanc may retain a different acid line from one based on Sémillon. Sauvignon Blanc can contribute its own aroma precursors; Gewürztraminer and Pinot Gris begin with still other balances of aroma, acidity, and skin composition. Noble rot can partly obscure varietal distinctions as its own transformations become more extensive, but it does not erase them.

Pressing, oxygen exposure, fermentation vessel, blending, and maturation widen the range. Inert vessels can preserve a more immediate contrast between fruit, acidity, and sweetness, while wood and controlled oxygen exposure can broaden texture and move the wine toward more developed, savoury character. Bottle age may deepen colour and integrate youthful fruit with fungal, fermentation, and maturation-derived aromas. Concentrated sugar, acidity, and extract can support long development, but longevity still depends on sound fruit, fermentation, stabilisation, closure, and storage; botrytization alone is not a guarantee.

Regional traditions

Sauternes in Bordeaux is based chiefly on Sémillon, with Sauvignon Blanc, Sauvignon Gris, and Muscadelle also permitted. The current specification connects nocturnal moisture near the Ciron and Garonne with rapid daytime ventilation, and requires overripe grapes showing noble rot to be harvested by successive manual selections.[2] Producers may ferment and mature parcels separately, often using barrels, so grape mix, selection severity, vintage, and élevage prevent the appellation from representing one uniform style.

Tokaj follows a different logic. Furmint and Hárslevelű are central among its permitted varieties. A proposed Union amendment published in March 2026 describes Aszú as individually selected botrytized berries macerated in must, fermenting must, or wine; Szamorodni instead processes bunches containing both botrytized and healthy grapes. It also specifies ageing in wood, with different minimum periods by category.[3] The contrast shows why “botrytized” does not describe a complete method: selected berries infused into a base wine are not equivalent to directly pressing fruit gathered through successive selections.

Germany's Beerenauslese and Trockenbeerenauslese traditions commonly rely on overripe, noble-rotted berries, especially Riesling, whereas Eiswein concentrates juice by freezing and is a separate process. In Alsace, Sélection de Grains Nobles denotes hand-picked noble-rotted berries from Riesling, Muscat, Pinot Gris, or Gewürztraminer. The Loire also makes botrytized Chenin Blanc, but its sweet wines may derive from noble rot, on-vine dehydration, or both. Regional names should therefore be read as particular rules and practices rather than as interchangeable labels for any sweet wine made from shrivelled grapes.

Sources

  1. Barbara Blanco-Ulate et al., “Developmental and Metabolic Plasticity of White-Skinned Grape Berries in Response to Botrytis cinerea during Noble Rot,” Plant Physiology 169 (2015), pp. 2422–2443, https://doi.org/10.1104/pp.15.00852. The authors caution that their direct comparison with bunch-rot data involved different cultivars and experimental methods. ↩︎ ↩︎

  2. Ministère de l'Agriculture et de la Souveraineté alimentaire, Cahier des charges de l'appellation d'origine contrôlée “Sauternes”, homologated 25 March 2026, sections VII and X. ↩︎

  3. Hungarian Ministry of Agriculture, Tokaj termékleírás, 10th version, listed as applicable to grapes harvested after 1 August 2025. The proposed Union amendment published in March 2026 describes grape-by-grape selection for Aszú, maceration in a same-vintage base, and at least 18 months in wooden barrels; it describes six months in wood for sweet or dry Szamorodni. ↩︎