Visit to IL Glicine winery
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In the afternoon of 25th of September we visited a small vineyards and winery Il Glicine in Emilia Romagna wine producing region close to Cesena in east Italy. We had an interesting walk all around the vineyards of sangiovese and trebbiano; the local varieties of Emilia Romagna region. This winery has a beautiful country side and is a part of wine dine route of Romgna. During our visit in this winery we observed practical use of microoxigination in wines. So below I have described in brief the process of microoxigination in quality wine making.
Micro oxygenation
Micro-oxygenation is a process used in winemaking to introduce oxygen into wine in a controlled manner. Developed in 1991 by Patrick DuCournau, working with the exceptionally tannic grape Tannat in Madiran, the process gained usage in modern winemaking following the 1996 authorization by the European Commission. Today the technique is widely employed in Bordeaux as well as at least 11 different countries, including the United States and Chile
Process
The process of micro-oxygenation involves a large two chamber device with valves interconnected to a tank of oxygen. In the first chamber the oxygen is calibrated to match the volume of the wine. In the second chamber the oxygen is injected into the wine through a porous ceramic stone located at the bottom of the chamber. The dosage is controlled and can range anywhere from .75 to 3 cubic centimeter per liter of wine. The process normally occurs in the form of multiple treatments that can last anywhere from one or two treatments during the early stages of fermentation (to help avoid stuck fermentation) to a more prolong treatment during the maturation period that can last four to eight months.
Benefits
The exposure of wine to oxygen in limited quantities can be beneficial to the wine. There needs to be a balance where too much oxygen can lead to oxidation and too little can lead to reduction and the ensuing wine faults. In oak barrel aging, the natural properties of the wood allows for a gentle aeration of the wine to occur over a prolonged period. This aids in the polymerization of tannin into larger molecules, which are perceived on the palate as softer. The process of micro-oxygenation aims to mimic the effects of slow barrel maturation within a shorter period and for less of the long-term cost associated with oak barrels. It also enables more control over this process, as opposed to barely observe it in such natural material containers as barrels.
During fermentation, the added oxygen can help maintain the viability of the yeast to minimize the risk of stuck fermentation and the production of undesirable sulfides. After fermentation it can aid in the clarification and stabilization of the wine without resorting to the use of fining agents.
The bevy of studies on micro-oxygenation with red wines is one expression of interest in colour adjustment. The slow or periodic addition of oxygen favours the polymerization of anthocyanins with tannins
Regardless of origin, limited oxygen uptake, either periodically or slowly over a protracted period, apparently results in no measurable oxygen build-up. The oxygen is rapidly consumed in oxidation reactions. Quinone production is probably the principal oxidation by-product. Polymerization and restructuring regenerate phenol groups capable of consuming additional oxygen. These reactions also favour colour stabilization in red wines (by encouraging anthocyanin–tannin polymerization). In addition, tannin–tannin complexes reduce the bitterness and astringency of tannins, donating a smoother mouth-feel. Furthermore, acetaldehyde produced in the oxidation of ethanol can combine with other wine constituents, notably sulfur dioxide, anthocyanins and tannins. This limits acetaldehyde accumulation, avoiding development of an oxidized attribute. During maturation, oxidation is limited by restricting air access, as well as by adding SO2. However, the benefits of limited oxygen ingress for red wine maturation are changing attitudes. Corresponding, there is considerable interest in regulating oxygen uptake. This is especially so for producers, who wish to avoid oak flavours, but still desire the perceived benefits of minimal oxygen uptake. This has led to the term microoxygenation, and procedures for regulating oxygen uptake via inert cooperage (Parish et al., 2000; Lemaire et al., 2002; Jones et al., 2004).
Micro-oxygenation may involve the use of high-density polyethylene cooperage (Flecknoe-Brown,2005). They can be designed to have a relatively precise oxygen diffusion rate. Oxygen uptake in oak cooperage, though generally thought to be negligible, appears to occur through the ends of the barrel or via the bung hole (if not tightly bunged). The rates most often quoted are estimates, and could vary considerably, due to differences in construction, wood porosity, wood thickness, and the number of repeat uses.
To facilitate micro-oxygenation, silicone tube diffusers may be used to achieve oxidative control in large cooperage. Silicone tubing is about a thousand times more oxygen-permeable than other plastics. Oxygen ingress can be controlled, and kept below the rate of consumption, by adjusting the length, thickness and oxygen pressure in the tubing. Instruments, such as Microdue® or Parsec, can also supply oxygen at various rates, via microporous diffusers. Castellari et al. (2004) consider that about 5 ml O2/litre/month (at 15–20 ºC) is roughly equivalent to barrel uptake, and lower than the rate of oxygen consumption in red wine. Whether these procedures adequately mimic the limited oxidation in barrels is a moot point (du Toit et al., 2006). What microoxygenation clearly offers is better control.
micro-oxygenation (microOx) techniques and equipment have made significant advancements since the first experiments, carried out in the 1990s, to soften heavy red wines of the Madiran region of France.
There are many reasons why winemakers use this process to introduce controlled amounts of oxygen into a wine – from wine enhancement, to better oak integration, faster barrel ageing, to fix problem wines – in almost all stages of the winemaking process.
Bibliography:
J. Robinson (ed) “The Oxford Companion to Wine” Third Edition pg 442-443 Oxford University Press 2006 ISBN 0198609906
Wine Science, Principle, Practice, Perception by- Ron S. Jackson
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