NITROGEN GENERATORS FOR WINEMAKING
The following article is the result of the dialogue with various managers of wineries and experts in the wine sector. Its purpose is to illustrate the advantages deriving from the use of Nitrogen through the whole process of vinification, from the bunch of grapes to the bottle. Even more evident advantages if, instead of a traditional supply, the Nitrogen is produced directly at the cellar.
Modern enology is currently experiencing a small silent revolution. After the era of chemistry and sulphites, the sector rediscovers and now invents new physical processes. On the other hand, one does not exclude the other; on the contrary, the two approaches should now be integrated into an intelligent, clean and convenient process.
At the same time, the globalization of trade leads to market prices that tend to conform, so wine becomes a raw material like any other. It therefore becomes difficult for most wineries to sell their wine more expensive, and the only way to guarantee good margins is to reduce production costs while maintaining quality.
DISSOLVED OXYGEN AND POLYPHENOLS
For some years now the role of Oxygen in musts and wines has been fully understood. Today the management of the DISSOLVED OXYGEN along the whole process of vinification appears as a foundation of modern enology. In a must or in a wine, the present Oxygen is consumed. If the consumption speed is higher than the dissolution rate, we will not have an increase in the dissolved Oxygen content. On the contrary, it causes an increase in the dissolved Oxygen content. The main responsible for the consumption of Oxygen are the POLYPHENOLS, whose important content can justify the oxygenation of certain white and rosé musts. It is therefore a good rule to make regular adjustments to the exact amount of Oxygen that the polyphenols will consume, so as not to increase the dissolved one. An optimal level of dissolved Oxygen in the bottle should be below 0.5 mg/L, considering that each additional mg of dissolved Oxygen decreases the shelf life of a bottle by one month. The phase following bottling takes the name of “bottle disease”, that is an oxidation-reduction reaction leading dissolved oxygen to consume free SO2.
NITROGEN IN ENOLOGY
The use of NITROGEN immediately involves benefits:
– decrease in labor and time savings in key oenological processes
– correct management of dissolved Oxygen
The best way to protect wines against unwanted oxygenation is BLANKETING with Nitrogen. Similarly, STRIPPING is the best technique for deoxygenating (elimination of dissolved Oxygen) or decarbonizing (elimination of dissolved Carbon Dioxide) wines.
The first occurs with the injection of Nitrogen up to saturation of the volumes of wine and musts storage, so as to prevent contact with the Oxygen and the consequent dissolution. The second is performed by injecting Nitrogen microbubbles into the wine: the Oxygen molecules, the most volatile, are the first to be eliminated. In this case, the effectiveness of deoxygenation is a function of the concentration gradient between the Oxygen dissolved in the wine and the Oxygen contained in the micro-bubbles. On the other hand, carbon dioxide, which is considerably more soluble in wine, is much more difficult to obtain.
It should be emphasized that Nitrogen does not tend to migrate to wine, being this saturated in Nitrogen already at standard temperatures (15°C). For maximum efficiency, blanketing and stripping require 99.5-99.9% pure Nitrogen. The pressure of the Nitrogen is of little importance, what matters is to regulate the flow rate of the gas according to the volume to be filled or in relation to the flow of wine passing through the canalization. Usually the pressure is between 3 and 5 bar(g), the goal to be reached is to fall below the 0.5 mg/L of dissolved Oxygen at the end of the process.
USES OF NITROGEN AT THE CELLAR
The Nitrogen also has a great advantage compared to other inert gases (e.g. Argon): the air contains about 78%. With an on-site Nitrogen generator producing Nitrogen directly from compressed air, the cost of the material becomes practically derisory. It thus becomes possible to intelligently and extremely conveniently integrate Nitrogen into the whole of the oenological process. It no longer has to be considered as an additional tool, but rather as a basic technique to be integrated into the different phases of work. The following are the different phases and the relative use of Nitrogen:
DESTEMMING/CRUSHING: once the mechanical separation of the grapes from the stalks is carried out, the grapes are pressed and the juice is released. In this phase, the average Oxygen content is about 6 mg/L. Blanketing with Nitrogen is therefore necessary to avoid the excessive intake of dissolved Oxygen in the solid matter/juice mixture. This is why many cellars install a detachment for Nitrogen injection downstream of the pump that feeds the press. The injection pressure of Nitrogen is about 4 bar(g), and depends on the distance and the manometric height to be overcome to reach the press. The flow rate in Nitrogen is about 20% of the pump flow rate.
PRESSING: this is the operation by whom a must is obtained from the bunch of grapes for vinification. To avoid the contribution of Oxygen during this phase, the ambient air is replaced with Nitrogen. Depending on the conditions of use, the maximum gas pressure varies between 1.8 and 2 bar(g), generally more than enough to extract the whole juice. The collection of the juice under a flow rate of 30-50 L/min of Nitrogen allows the saturation of the gaseous volume above the liquid in the collection tube.
FLOTATION: before putting the must in fermentation tanks, the so-called skimming is carried out, which frees the must from solid impurities. Also in this phase, the blanketing in Nitrogen avoids the contribution of Oxygen. The flotation can be done in a static or sedimentation way. In this case, the must is pressured and saturated in Nitrogen, then pressure is reduced to form micro-bubbles carrying the impurities to the surface. It is therefore a down-top flotation, that is to say in the opposite direction to what happens in the static process. The consumption of Nitrogen varies between 2% and 6% of the volume treated.
REPLACEMENT: during the maceration on the skins, the so-called replacement is carried out by returning the liquid phase (grape must or wine in alcoholic fermentation) from the bottom of the maceration tank towards the upper part. On red wines, a strong injection of Nitrogen causes the breakage of the pomace cap, extracting the constituents of the solid parts of the grapes (anthocyanin, tannin, aromatic compounds). On white wines, the injection of Nitrogen allows to homogenize the leavening. In both cases, the intensity of the action depends on the frequency and duration of the replacement, with an important gain of time and quality. Both on whites wines and red ones, the required Nitrogen pressure is 3-5 bar(g), with a flow rate of about 3% of the volume to be reassembled and an injection duration between 1 and 3 minutes.
ASSEMBLY, SIZING AND ADDITIVES ADDITIONS: following the fermentation we proceed to the homogenization of the wines, to the sizing or to the additives addition without Oxygen. For the injection of Nitrogen it is advisable to use a macro porous diffuser, able to generate large bubbles. A Nitrogen purity of 99.5% is more than satisfactory: if the purity is 99.9%, there is a risk of deoxygenating or decarbonizing wine, even more important if the bubbles are small. Also in this case the pressure is 3-5 bar(g), with durations of the order of 2-3 minutes.
POURING: the injection of low pressure Nitrogen into the barrel allows the evacuation of the wine towards the tank. The pressure of the Nitrogen depends on the counter-pressure given by the difference between the height of the wine in the barrel and that of the destination tank. A difference of 10 m, for example, requires 1 bar(g), with an average time of 5/6 minutes to empty a barrel of 225 L. For optimal protection of wine from dissolved Oxygen it is also possible to perform stripping on the transfer line.
PHYSICAL TREATMENTS: injection of Nitrogen into musts or wine before physical treatments (centrifugation, electro dialysis, filtration, cold stabilization, etc.). Nitrogen injection usually takes place between the pump and the treatment tools, with a pressure at the reducer between 3 and 5 bar(g) and a variable flow rate depending on the potential Oxygen supply of each treatment. In-line stripping at the output of the treatment apparatus is also recommended. A flow rate of about 15 L/min allows to keep the dissolved Oxygen level stable. At the end of the operation it is usual to re-flux the line with Nitrogen at 2-3 bar(g) to clean and dry it.
TANKS BLANKETING: it is a process that ideally would require a continuous analysis of the presence of Oxygen in the internal atmosphere of the tank. The pressure of the Nitrogen is kept low, usually no more than 20 mbar, and the entire volume is changed 3 or 4 times to obtain and maintain a satisfactory purity between 0.5% and 1% in Oxygen. The Nitrogen is in fact lighter than the Oxygen, so it escapes quite quickly in its presence (the tanks are rarely sealed in their upper part). If the presence of Oxygen is high, then it is necessary to intervene and recondition the atmosphere. Without an Oxygen sensor it is however impossible to know the rate of residual Oxygen in the atmosphere and therefore to effectively intervene. For this reason, Gasgen offers specific analysis sensors and PLC-based control systems.
WINE TRANSFER: the transfer of wine is a delicate operation that requires blanketing with Nitrogen to avoid the contribution of Oxygen. The injection of Nitrogen usually takes place at the exit of the transfer pump, with a pressure of 3-5 bar (g) and a flow rate of the order of 5% of the volume of wine in transit. If the objective is also to deoxygenate or decarbonize the wine by stripping, then the flow must be increased. The blanketing of the origin and destination volumes, as well as of the connecting hoses, is of fundamental importance. In case of partial emptying of the tank, it is necessary that the volume of Nitrogen supplied dynamically compensates the volume of poured wine. The maximum flow must be adjusted on the capacity of the generator and its storage tank. Following the decanting it is good practice to check the CO2 and SO2 values. The fluxing of the ducts at the end of the operation guarantees their drying and cleaning.
BOTTLING: in this phase it is important to avoid the contribution of Oxygen in the wine and in the space at the head of the bottles by means of Nitrogen. In fact, in the bottle the contribution of Oxygen has two origins: the Oxygen already dissolved at the origin and the Oxygen dissolved in the head space. By doing the vacuum as per normal practice (e.g. 200 mbar), about 5% of Oxygen remains in the bottle. If, on the contrary, the volume in Nitrogen of the bottle is injected once and the vacuum is carried out twice, the Oxygen content drops to 1%. For an optimal injection we recommend inserting a tube inside the bottles, with an instantaneous flow rate between 10 and 20 m3/h at 5-6 bar (g). A standard bottling brings up to 2 mg/L of dissolved Oxygen, for a total of about 4 mg/L in bottles and values that often touch saturation. On the contrary, a quality bottling should be able to drop below 0.5 mg/L, considering that every additional mg of dissolved Oxygen decreases the duration of bottled wine by one month. The phase following bottling takes the name of “bottle disease”, that is an oxidation-reduction reaction that leads to dissolved Oxygen to consume free SO2.
NITROGAS® NG – NITROGEN GENERATORS FOR WINEMAKING
Based on the above, Gasgen has designed and conceived NITROGAS® NG series, a complete range of Nitrogen generators for winemaking, wine blanketing and bottling at the cellar. The on-site generation is in fact a simple and smart solution to save money, improve efficiency and take full control of the gas supply process, generating the exact amount of Nitrogen to the purity required by the process.
NITROGAS® NITROGEN GENERATORS ELIMINATE THE NEED FOR GAS TRANSPORT AND STORAGE
Through the Pressure Swing Adsorption (PSA) technology, NITROGAS® NG Nitrogen generators for winemaking produce food-grade Nitrogen from industrial air class 1.4.1 standard ISO 8573.1-2010. The dry, purified air from a standard industrial compressor and an air treatment system is essentially “sieved” to remove Oxygen and other trace gases, while the Nitrogen passes through the adsorbers. Using specially selected molecular sieves (CMS), NITROGAS® NG Nitrogen generators for winemaking produce pure Nitrogen (up to 99.999%) with moderate air consumption. Non-cryogenic air separation is a well-known process, but the design and control features applied to NITROGAS® NG Nitrogen generators help maximize gas production and reduce air consumption, achieving the highest levels of efficiency. As a consequence, the choice of entrusting its own supply of Nitrogen to an on-site generator rather than to traditional supply can lead to a cost reduction of up to 90%.
THE PAY-BACK PERIOD IS IN GENERAL BETWEEN 6 AND 24 MONTHS
In addition, NITROGAS® NG Nitrogen generators help to make work environments safer as they eliminate security risks related to external supplies such as storage, handling and replacement of high-pressure cylinders or cryogenic tanks. In conclusion, considering all the previous points, NITROGAS® NG Nitrogen generators for wine cellars are the winning solution for your winemaking, wine blanketing and bottling process.
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