330 members who each year contribute 6.500 tons of grapes, of which approximately 5.000 are Barbera: these are the figures of the Cooperative Winery Barbera dei Sei Castelli di Agliano Terme, in the heart of the most prestigious denomination for the Piedmont variety, the Barbera d’Asti DOCG.
Ever attentive to the most modern vinification and refinement techniques, in 2013 the Barbera dei Sei Castelli cellar adopted a Parsec micro-oxygenation system adept in ensuring proper management of oxygen in macro- and micro-oxygenation in the majority of tanks distributed throughout various winemaking and storage areas. The structure is comprised of 7 basic multiple periphery units for micro-oxygenation (with the possibility also of macro-oxygenation and single-dose applications) of 24 tanks from 250 to 1500 hl and 4 units of multi-output macro-oxygenation (with macro-oxygenation and single-dose provision) serving 20 tanks with a capacity ranging from 500 to 1000 hl.
Macro- and micro-oxygenation are thus utilised in the necessary doses throughout entire life of the wine, from fermentation to refinement, as recounted by Enzo Gerbi, Oenologist and Technical Director of the Cantina, speaking about his experience with micro-oxygenation of the Barbera and other grapes processed within the winery.
How long have you been utilising macro- and micro-oxygenation?
E.G. My first encounter with micro-oxygenation dates back to around 10 years ago when I initially experimented with a micro-oxygenation system on Barbera in a small mono-tank. Following this, we continued to apply the oxygen dosages, still limited to Barbera d’Asti and always with small mono-vat dispensers that allowed for the effectuation of macro-oxygenation in vinification and micro-oxygenation further on in the course of storage, until we became equipped with a centralised system for a much more widespread use of oxygenation in the 2013 vintage, both in terms of macro- and micro-oxygenation.
What were your experiences and, on the basis of these, how has the relationship with oxygen and your wines evolved?
E.G. We commenced with the application of micro-oxygenation initially in a very reduced means, with very few tanks and always in the post-racking phase on a Barbera with an important structure both in polyphenolic and alcoholic terms. We subsequently implemented the use of macro throughout the fermentation -even utilising few units rotated on the set-up to various tanks each day- before turning to micro-oxygenation post-racking through to the beginning of malolactic fermentation. In these instances, I have always noticed better fermentation being effectuated and greater olfactory cleanliness and gustatory precision, associated with a better colour fixation. All this led me to installing the Parsec system so as to better manage oxygen throughout each part of the cellar and for each necessity.
In particular, I was driven to use macro-oxygenation throughout the fermentation of white wines (for us being Cortese and Chardonnay) and local red wines being Grignolino and Dolcetto.
During the first harvest, that of 2013, I commenced with dosages with a single 2/3 mg/l dose and, little by little, moved on to certain experiments with dosages of 2/3 mg/l/day of macro-oxygenation for a duration of 2 days. The results were a sharp olfactory cleanliness in the Cortese, no loss of perfumes and an optimum preservability of the wine throughout the vintage. In addition to the oxygen management, it has permitted me to completely eliminate the use of copper sulphate in winemaking.
As such, with the 2014 vintage and at this point on all the white wines I effectuated continuous macro-oxygenation with dosages ranging from 4 to 2 mg/l/day for 2/4 days, in accordance with the olfactory sensors of the moment, starting from the third day of fermentation, with the result of a regular fermentive process through to the complete fermentation of the sugars and a remarkable olfactory cleanliness.
In regards to the Barbera, our processing protocol foresees a dosage of macro-oxygenation during fermentation and maceration of 4-7 mg/l/day until the end of fermentation, before successively moving on to the racking (usually after 2-3 days) to effectuate a macro of approximately 2-3 mg/l/day for 4-5 days and then passing to the micro of 2 mg/l/month that normally, after several days and following a tasting check, is reduced to 1 mg/l/month until the exhastion of 50% of the malic acid.
After pouring off at the end of the malolactic fermentation, the micro-oxygenation continues at a dosage of 1 mg/l/month whilstever the temperatures allows it (unfortunately in areas of the cellar, it is still problematic to maintain the wines at an ideal temperature for micro-oxygenation).
What control parameters are utilised in the follow-up of the micro-oxygenation process?
E.G. Normally, our checks are based on the analytical evaluation of the index of total polyphenols, anthocyanins, the tannin/anthocyanin correlation, the state of the combination of anthocyanins with the dTat% index, the ethanale content and the management of free sulphur dioxide and, naturally, a great deal of attention to the tasting.
What challenges have been resolved with the use of micro-oxygenation?
E.G. I would not say that it has allowed me to resolve great difficulties in so much as having improved that which is possible to obtain. From an operational point of view it has allowed me to eliminate air-exposed pumpovers, with greater rationalisation of time spent working and of personnel. This has then allowed us to anticipate the commencement of the malolactic fermentation, particularly in wines with high alcohol and polyphenolic potential where I have, in fact, observed that the vats with micro-oxygenation normally commence their malolactic fermentation earlier than the same wine in simple tanks.
What qualitative results have you been able to achieve with the application of micro-oxygenation?
E.G. Definitely a greater olfactory clarity for both red and white wines, as well as a better obtainment of colour that I consider the greatest advantage garnered with Barbera.by