Noble rot (; ; ; ) is the beneficial form of a grey fungus, Botrytis cinerea, affecting wine .[ Grapes typically become infected with cinerea when they are ripe. If they are then exposed to drier conditions and become partially , this form of infection is known as noble rot. Grapes picked at a certain point during infestation can produce particularly fine and concentrated sweet wine. Wines produced by this method are known as botrytized wines,][
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The primary distinction between botrytized wines and other naturally sweet, non-fortified sweet wines, such as late-harvest wines, , or Straw wine wines, lies in the range and richness of aroma compounds generated by Botrytis cinerea.[ Descriptors frequently used for these wines highlight flavours of peach, apricot, pear, quince, raisin, and honey, along with unique "botrytis" or roti characteristics.][
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Effect on grapes
When Botrytis cinerea infects grapes, it initiates several physiological changes that are crucial for the development of noble rot wines. The fungus penetrates the grape skins while feeding on the grapes, causing microscopic wounds that lead to the evaporation of water from the berries.[
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The fungus primarily consumes tartaric acid, which is more prevalent than Malic acid or citric acid in healthy grapes, with remaining tartaric acid transformed into gluconic acid and glycerol.[ The grapes' metabolic stress response also leads to the production and concentration of various Aroma compound. The berries concentrate precursors for citrus aromas like lemon and grapefruit, and also generate compounds for stone fruit aromas such as apricot and peach in a direct metabolic response to the fungal attack. Some of these aromatic characteristics, including the distinct honey aroma, are directly attributable to the botrytis fungus itself.][
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The stress response of grapes to botrytis infection is similar to their response to drought. The breakdown of grape skin cells by the fungus facilitates water evaporation, intensifying the dehydration process. This stress response allows the grapes to adapt metabolically, slowing down the infection rate compared to grey rot, which spreads too quickly for the plant to respond effectively.[
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Origins
According to Hungarian legend, the first Tokaji (a wine using botrytised grapes) was made by Laczkó Máté Szepsi in 1630. However, mention of wine made from botrytised grapes appears before this in the Nomenklatura of Fabricius Balázs Sziksai, which was completed in 1576. A recently discovered inventory of aszú predates this reference by five years. When vineyard classification began in 1730 in the Tokaj-Hegyalja region, one of the gradings given to the various centered on their potential to develop Botrytis cinerea.
There is a popular story that the practice originated independently in Germany, where the Riesling producers at Schloss Johannisberg (Geisenheim, in the Rheingau region) traditionally awaited the say-so of the estate owner, Heinrich von Bibra, Bishop of Fulda, before cutting their grapes. In 1775, the story claims the abbey messenger was robbed en route to delivering the order, delaying cutting by three weeks, time enough for the botrytis to take hold. The grapes were presumed worthless and given to local peasants,[ A Short History of Riesling] who produced a surprisingly good, sweet wine which became known as Spätlese, or late harvest wine. In the following few years, several different classes of increasing must weight were introduced, and the original Spätlese was further elaborated, first into Auslese in 1787[ Karen MacNeil The Wine Bible Workman Publishing 2001 page 540 ] and later Eiswein in 1858 (although Eiswein is usually made from grapes not affected by Botrytis).
Viticulture and uses
In some cases, inoculation occurs when of the fungus are sprayed over the grapes, while some vineyards depend on natural inoculation from spores present in the environment.
Some of the finest botrytized wines are picked berry by berry in successive tris (French language for "selections").
Internationally renowned botrytized wines include the aszú of Tokaj-Hegyalja in Hungary (commonly called Tokaji or Tokay),
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