After caffeine-free coffee, lactose-free milk, gluten-free flour, we have also removed alcohol from the alcoholic drink par excellence: wine. When we talk about dealcoholized wine we are in fact referring to wine without an alcoholic component, that is,ethanol. For the Italian legislationthe wines considered non-alcoholic they have less than 0.5% v/v. After this group we find wines with low alcohol content, then reduced and finally those with real alcohol content. The same division does not apply in other countries around the world. There dealcoholization it can be total or partial, in any case, the flavor of the wine is not remains exactly unchanged: there may be slight differences in color or loss of some volatile aromatic compounds which determine the odor. The “corrective” action of the wine, as for non-alcoholic beer, can occur before, after or during fermentation. How? Reducing sugars (from which ethanol is obtained) Before of fermentation, reducing alcohol production during fermentation or by removing ethanol molecules After their formation, a solution that more than any other allows maintaining flavors and aromas closer to the original.
Limit alcohol production before wine fermentation
In the production of wine everything starts from harvesting the grapes during the right period harvest. The way the grape is crushed allows winemakers to understand the exact moment when the grape is ready. Already at this stage you can act if you want to make a dealcoholized wine.
What makes wine alcoholic is ethanol. We know that ethanol is formed when the sugars contained in grapes are transformed into alcohol and carbon dioxide thanks to the action of yeast enzymes. So to have less alcohol we can act on sugars from the beginning.
There sugar concentration in grapes increases when the ratio of leaf to fruit area increases. To manage the concentration of sugars in grapes it is therefore necessary to intervene on (or modify) this ratio. So it is possible choose to harvest grapes late or early and to prune the plants in a certain way and in a certain period to have a less sugary starting point.
An alternative is lengthen the must with water and therefore reduce the concentration of sugars in the mixture. Other methods involve a filtration of pressed grape juice, through membrane filters which allow some molecules to pass and block others. Finally, you can also act on the compound by adding an enzyme: la glucose oxidase. This ingredient reduces glucose from the wort even before fermentation. Less sugar will mean less alcohol.
Plan B: act on the fermentation phase of the must
The grapes are pressed and the must, to which i. are added yeasts and the phase is activated fermentation: the sugars contained in grapes are transformed into alcohol and carbon dioxide. Even during this phase you can intervene to make less alcohol form.
One of the first ways is use different yeasts that is, yeasts that are not the classics Saccharomyces used normally. In fact, some strains can naturally ferment less sugar.
In reality we don’t necessarily have to change strains, we can also use one modified through genetic alteration (like GMOs). In the laboratory you can make sure that the yeast functions lessi.e. you ferment less to produce less ethanol. Another option is the fermentation stoppedthat is, deliberately interrupting the fermentation process before its total completion: in this way we give the alcohol little time to fully form.
Last possibility: remove the ethanol from the wine after its formation
Processes are used to remove ethanol from post-fermentation wine membrane filtration. These methods exploit a membrane with pores small enough to allow the passage of some molecules rather than others. These processes are also used to produce non-alcoholic beer.
One of the best known processes is thereverse osmosis. In typical osmosis processes, when we have two solutions with different concentrations, to restore the balance between the two parts, the solvent moves from the less concentrated solution to the more concentrated oneas if to dilute it. By applying a certain control on the pressure, however, a reverse osmosis process can be activated the solvent moves in the opposite directionfrom the most concentrated solution to the least concentrated one.
There are many variations of this process. In one variant, water and wine are circulated countercurrently on opposite sides of a hydrophobic (i.e. water-repellent) hollow fiber membrane. Pressure applied from the outside does evaporate theethanolwhose vapor comes out of the pores of the membrane, condensing in the water. This is one of the best known methods because it leaves the aromatic compounds of the wine almost unchanged, maintaining its original flavour. Furthermore, it can take place at temperatures that are not too high and allows both solutions (water and wine) to be recovered.
Another well-known method is that of rotating cone column which operates at low temperatures and is very effective. The wine is passed through this machine which has several cones arranged vertically that rotate on themselves. The rotation causes the wine to deposit in very thin layers on the surface of the cones. All this contact area between drink and cone causes the ethanol molecules to evaporate very easily, at low pressure and temperature. Another advantage of this method is that wine aromas are recovered separately from ethanol and therefore they can be reintegrated into the dealcoholized wine.
All dealcoholization methods illustrated they alter the flavor of the winesimply because the same wine with alcohol and without alcohol cannot be exactly identical. Of all the methods, however, post-fermentation dealcoholization manages to maintain the flavor of the wine best. In fact, the rotating cone column and reverse osmosis remain the most used and appreciated.
