Yeasts in the service of Franciacorta.
Our research

Ten years’ research by Ricci Curbastro.
How yeasts are used to make pleasant-tasting and preservable Franciacorta wines

The world market of wines puts a lot of pressure on wine-making companies to develop their own production methods, in order to obtain good quality wines and to create their own identity, with the aim of being more and more competitive.
Our company is no exception to the rule. For years now the main “ingredient” of Franciacorta DOCG production is time. It is not by chance that eight out of the twelve available Franciacorta wines are vintage wines that are aged in vats for longer than required by standard PDO rules.
The ageing process favours the development of the most interesting aromas and time is, therefore, an important ingredient in the production of these wines.
Many professional wine critics acknowledge our work. Here are some comments
“The richness of Ricci Curbastro Franciacorta wines is exceptional and higher than the average richness of PDO wines…” 1
“The aroma profile and the “sprint” of taste of Rosé and Satèn, two Franciacorta wines of that kind, are unique…”2.
For years Ricci Curbastro has been trying to find its own personal style and character. To that end, batches of Franciacorta base wine (made from Chardonnay and Pinot Nero grapes) are stored in steel vats with fine lees, in an oxygen-poor environment, in order to obtain wines with a more harmonious and homogeneous aromatic profile. These wines are then used in proportions ranging from 10-15% up to 50-100% for the tirage cuvées of vintage Franciacortas.s

 

THE ACTION OF THE saccharomyces cerevisiae ON THE PRESERVABILITY OF A WINE:
The yeast cell is surrounded by a thick wall that ensures for its shape and integrity. This wall constitutes the primary interface between the yeast and its environment. It consists of three types of polymers: the β-glucans, mannans bonded to the proteins - their entirety forms mannoproteins - and chitin. Each of these polysaccharides has some interesting biotechnological property. The wall of the yeast is of considerable technological relevance, due to its role in the hygienic and organoleptic stability of wines.
Currently, consumers have little interest in wines that are insufficiently fruity and round. In such cases, fining on lees seems an appropriate technique to reduce this loss. The lees can be defined as the deposits that accumulate 24 hours after moving the wine. The fine lees are, therefore, all the elements that remain suspended during these 24 hours. Proper handling of the lees consists in eliminating the coarse lees, which are likely to depreciate the wine, immediately after their formation. The quicker this occurs, the longer the fining process will last. The fine lees are mainly composed of yeasts, where autolysis - natural enzymatic self-degradation - releases many interesting compounds. The composition of fresh lees is variable, but the compounds that are released in the wine are always nucleotides, fatty acids, amino acids, peptides, polysaccharides, and glycoproteins (mannoproteins), which have a positive effect on the sensory profile and on the stability of the wine, with regards to tartaric deposits and protein precipitations, as well as color. Aromatic stability also depends on the quantity and on the nature of the mannoproteins released during autolysis. Then again, mannoproteins are released into the wine by an enzyme β-1, 3 glucanase enzymatic activity, which that is a slow phenomena, even if some techniques, such as bâtonnage, can increase the quantity of mannoproteins released into the wine.
In light of the above, it is evident how the contribution of yeasts is interesting for the long-term development of a Franciacorta wine. However, this "discovery", by now acquired by international research, is based on the addition of exogenous compounds to the wine itself (mannoproteins, LSI, ß-Glucanase, etc...)

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Anche la stabilità aromatica dipende dalle quantità di mannoproteine liberate nel corso dell'autolisi così come dalla loro natura. D'altra parte, le mannoproteine sono liberate nel vino da un'attività enzimatica β-1,3 glucanasi, che è un fenomeno lento, anche se certe tecniche come il bâtonnage possono incrementare la quantità di mannoproteine rilasciate nel vino.
Alla luce di quanto sopra risulta evidente quanto l'apporto dei lieviti sia interessante per l'evoluzione di lungo periodo di un Franciacorta ma questa "scoperta" ormai acquisita dalla ricerca internazionale si basa sull'aggiunta di composti esogeni al vino stesso (mannoproteine, LSI, ß-Glucanasi ecc.).

 

THE RICCI CURBASTRO EXPERIMENTS:
The experiments conducted so far in our winery have, instead, always focused on the natural extraction of these compounds from the fine lees produced by the wine itself.
While trying to age the Franciacorta bases in oak barrels (barriques) for extended periods of time (over one year), we found oxidation phenomena affected aroma and color. The addition of SO2 as a protection against these phenomena, partially inhibits the aromatic developments, which would be guaranteed by the lysis of the yeasts.
When aging in small stainless steel barrels (5 Hl), a limit is always represented by the need for sulfur dioxide as an anti-oxidative protection for the wine, and by the limited surface size of the bottom of the barrel, which does not guarantee for an optimal contact between wine and fine lees. Consequently, this involves a reduced exchange of compounds, also in relation to the barrel.


AN OPERATIVE SOLUTION:
The ideal solution to the problem of reducing the sulfur dioxide to very low limits (moreover, also required for the subsequent second fermentation in bottles) and, at the same time, ensuring enough contact surfaces between the yeasts and the Franciacorta base wine, and benefiting from the contribution of a protective inert atmosphere, was found in the use of 1.5 liter magnums for preservation, closed with stainless steel crown caps, which guarantees a perfect seal for several years.
This further development in our research needed to obtain a special authorization for the preservation of base wines, no longer in barrels, but in magnum bottles, which were then to be re-opened after a few years. The MIPAAF (Ministry of Agricultural, Food, and Forestry Policies) has recently authorized the Ricci Curbastro Farm Estate Winery to test this system of preservation and extraction of yeast compounds for five years.
The experimentation in bottles began in spring 2010.

 

Capriolo, April 2010