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The "Noble Rot"

The formation of Botrytis Cinerea noble rot is a unique and successful combination of many factors related to the climate and the land.
The drying of the grapes, to get the MUFii, results from a physical phenomenon, a dehydration through ventilation and a biochemical process, that is the formation of “noble rot” caused by a microscopic fungus: Botrytis Cinerea.

The Botrytis Cinerea phenomenon in protected but not closed rooms, it is only due to this soil and its climate, apparently detrimental, to the alternation of sunny and rainy days or morning mists that transform the disadvantage into a great benefit, the means to obtain a unique and elegant wine tied to the territory: the MUFii.

Considerations and evolution
of the Noble Rot in Passitaia
on white grapes of Colline Novaresi
affected by
Botrytis Cinerea
The grapes withering to obtain the MUFii is achieved by a physical phenomenon, a dehydration through ventilation and a biochemical process, that is the formation of “noble rot”.

The “noble rot” is a consequence of the grape invasion by a microscopic fungus that develops only in particular and favourable climate conditions: Botrytis Cinerea.

This is in fact the name by which we generally identify a particular kind of mould that allows the creation of mouldy or “botrytized” wines.

Obviously, not every rot makes such a good action on the grapes and not all the grape types are suitable to be affected by this particular mould, not even all the territories are appropriate to grow the “noble rot”.

The noble rot formation is therefore a peculiar combination of many factors, morning moisture, windy climate during the day and a temperature range between day and night.

The grapes withering is also related to an adequate type of grape, to the strenght of the peel and to the protection layer of bloom (the waxy substance protecting the grape surface), that are characteristics typical of each variety.

The bunches must not be damaged by any natural or mechanical touch.
The vintage volume decrease, caused by the noble rot, may reach a 40-50%, but this never gives a sugar and organic acid consumption. The quality is obtained, therefore, to the detriment of the yield that is subject to a great reduction.

The withering result and the Botrytis Cinerea process is different every year.

A continuous and excessive humidity may develop another type of mould taking to opposite effects: the grey rot or ignoble rot, a factor that ruins irreparably the grapes making them unusable for the wine production.


In the vineyard the microscopic fungus may rest as a saprophyte in the soil, anyway it winters as a spore on the branches, or as a mycelium inside the buds.

We get the top production at the end of May-first decade of June (in between the flowering) and in autumn about the vintage.

When the Botrytis Cinerea spores, normally brought by the wind, pose on the wet grape peel, they begin to absorb the water on the surface, thus growing in size.

Afterwords, in the withering room La Passitaia, a germinal appendix starts forming and it pierces the peel to look for nutriment.

Through the cuticle micro fissures a filament enters and reaches the side epithelial structures causing a degradation of the side, the breaking of the cellular structures and the consequent mycelium spillage with conidiophores and conidia formation.

When the mycelium arrives into the grape, thanks to the great quantity of feeding substances its development is rather fast and the peel becomes literally covered by the “noble rot”.

The holes on the peel made by the spores facilitate the water reduction in the grape, thus concentrating the sugar and the aromatic substances.

The spread of the Botrytis Cinerea happens both for the propagation of the spores detached from the conidia and for the contact of the infected grape with the helthy one.

Larval Spots


The botrytization process lasts for a long period and it is particularly sensible to temperature. Under 5° the phenomenon stops.

The best temperature is between 18- 25°C. As the Botrytis Cinerea attacks a grape, first of all it causes one or more round spots on the peel.

These spots extend covering the entire grape surface.

The peel then suffer a digestive process, it becomes thinner and fragile, showing hollows and shallow hacks.

At this stage of the larval form, the grapes are still swollen, the Frenches call them “pourri plein”, that is mouldy.

The mycelium, in this condition, cannot fructify and develops the so called “uva infavata”: the berry changes its colour into a light brown one, proper of the baked bean, untill it reaches the brown-violet colour, sometimes up to the blue.

The mycelium does not develop on the surface of the berry peel, but only inside the grape.

When the action of the mould prolongs, the grape becomes wrinkled and wizened.

Manifest Appearance

If the mould develops with wet weather, the grapes will show some tufty parts more or less abundant on the surface.

The Frenches indicate them with “pourrì ròtis”. If this condition lasts, it can bring not to rotting but to a loss of the liquid content, thus drying the berries.

On the contrary, if the temperature and humidity conditions are unfavourable to the air development of the fungus, the grape can wither and dry without the growing of such tufty parts.
Sequential Observations of the Noble Rot in "La Passitaia"

The Botrytis Cinerea never attacks entirely the bunch at the same time and even not all the grapes together, therefore in the same bunch there may exist all the morphological aspects of the infection that evolves slowly and random, without knowing which grapes will be saved or more infected. It does not exist a synchrony in the infection evolution of the grapes, which appear by and by more or less interested. Some grapes remain safe and maintain their original colour, except for some variations due to the withering process.


The “noble rot” action continues with the transformation of some substances present in the grapes and it adds to these giving its own aroma and flavour. At the end of the process the grapes have a bad appearance, apparently rotting, but inside them a sort of unique magic occurred, creating a nectar.

Azienda La Passitaia

Via Paola Bellini 18 28010 Barengo (NO) Italia
P.IVA 08160190156

Per contattarci: info@lapassitaia.it
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