♦ The Noble Rot
The formation of noble rot is a particular and fortunate combination of many factors linked to the climate and the territory.
Grape drying, to obtain MUFii, occurs due to physical phenomenon, dehydration and biochemical phenomenon, that is, the formation of noble rot due to a microscopic fungus (Botrytis Cinerea).
CORRELATION BETWEEN ACINI AND BRIX GRADES
The phenomenon of botrytis cinerea in unprotected and unforced rooms is unique for this territory and it is to its climate, apparently disadvantageous, to the alternation of sunny days, to easy rains or to morning mists, that the transformation into a large advantage, that of obtaining a unique, elegant and local wine: the MUFii.
Considerations on evolution
of the Noble Mold in Passitaia
on white grapes from the Novara hills
The drying of the grapes, to obtain MUFii, occurs by physical phenomenon, a dehydration by ventilation and by biochemical phenomenon, that is, the formation of noble rot.
The "noble rot" is the consequence of the invasion of the grape by a microscopic fungus (Botrytis cinerea) and develops only in particular favorable climatic conditions.
In fact, this is the name by which that particular type of mold that allows the birth of botrytized or botrytized wines is generically called.
Not all molds naturally do a good job on grapes, and not all types of grapes are suitable for being attacked by mold; and not even all the territories are suitable for giving birth to the Noble Mold.
The formation of the Noble Mold is therefore a particular and fortunate combination of many factors, morning humidity, windy climate during the day, temperature range between day and night.
The drying of the grapes is also a function of the suitable blend, the strength of the skin and the protective layer of bloom (the waxy substance that protects the skin of the berry) which are typical characteristics of each variety.
There must be no mechanical or natural damage to the bunches. The decrease in the volume of the harvest, caused by noble rot, can even reach 40/50%, but there is no consumption of sugars and organic acids.
The quality, therefore, is obtained at the expense of the yield which undergoes a great decrease.
The behavior of withering and botrytis varies from year to year. In conditions of excessive and constant humidity, it can easily degenerate into another type of mold with opposite effects: gray mold or rot, a factor that irreparably ruins the grapes making them unusable for the production of wine.
In the vineyard, the fungus can be kept as a saprophyte in the soil, however it hibernates in the form of a spore on the shoots, or as a mycelium inside the buds.
The maximum production occurs towards the end of May-first decade of June (between flowering) and in autumn near the harvest.
When the spores of Botrytis cinerea are deposited on the moist grape skin, usually carried by the wind, they begin to withdraw the surface water and therefore increase in size.
Subsequently, in Passitaia, the formation of a germinal appendix begins which perforates the peel in order to seek nourishment.
A filament (hypha) is thus inserted into the cuticular microcracks which reaches the epithelial parietal structures leading to a degradation of the wall, rupture of the cellular structures and subsequent release of the mycelium with the formation of conidiophores and conidia.
When the mycelium arrives inside the grapes, thanks to the enormous amount of nutrients, its development is quite rapid and the surface of the skin is literally covered by the Noble Mold.
The holes in the peel caused by the spores favor the reduction of water in the grape, thus concentrating the sugar and aromatic substances.
The propagation of Botrytis cinerea occurs both by the propagation of the spores that detach from the conidia, and by the contact of the infected grape with the healthy one.
Spots and larval form
The formation of “infavato” berries lasts for a long time and is particularly affected by the temperature, at temperatures below 5 ° the phenomenon stops (Optimal development temperature 18-25 ° C).
When Botrytis cinerea attacks a grape, it causes, first of all, one or more circular spots on the skin.
These spots extend to cover the entire surface of the grape.
The peel undergoes a digestion process, becomes thin, brittle, has hollows and superficial lesions.
In this larval stage, the berries, which are still turgid, are called by the French "pourri plein" that is moldy.
The mycelium, in these conditions, does not bear fruit and generates the so-called "infavata grape".
The berry changes color, taking on the light brown color of the cooked bean up to brown - violet.
The mycelium does not develop on the surface of the epidermis of the berry, but only inside the grape.
When the action of mold is prolonged, the grape appears wrinkled, as if shriveled.
If the mold has developed in humid weather, the berries have more or less abundant flockiness on the surface.
The French indicate the grapes thus transformed, "pourri ròtis". If this condition continues it can lead not to rot but to the loss of the liquid content, drying out the berries.
If, on the other hand, the temperature and humidity conditions are unfavorable to the aerial development of the fungus, the grape can wither and dry out without these flakes appearing.
of the “Noble Rot”
Botrytis cinerea never attacks the whole bunch at the same time and not even all the grapes at the same time, so all the morphological aspects of the infection that occurs slowly and randomly (random) can coexist in the same bunch, without being able to predict which grapes will be free and which more attacked. There is no synchrony in the evolution of berry infections that appear gradually, more or less affected.
Some berries remain unscathed and retain their original color without prejudice to variations in withering.
The action of noble rot continues with the transformation of some substances present in the grapes and is added to these giving it its own aroma and flavor.
At the end of the process, the grapes take on an appearance that is anything but inviting, apparently rotten, but within them unique magic has occurred that will give rise to a nectar.