ES2303781A1 - Reduction of volatile acidity in hydroalcoholic liquids for food use - Google Patents

Abstract

The method described reduces the content of acetic acid and optionally of ethyl acetate by a dialysis process. The membrane features eliminate said substances in short time periods and without energy consumption. The system includes a device substantially comprising two stainless steel chambers separated by a membrane. The design of the membrane is the most appropriate for selective elimination of acetic acid and ethyl acetate because of the rapid diffusion thereof, while the more useful compounds in hydroalcoholic beverages (organic acides, sugars, polyphenols, etc) diffuse more slowly because of their greater molecular size. Also the systems does not require the use of potential gradients prohibited by legislation, such as pressure gradients.

Description

Reduction of volatile acidity in liquids hydroalcoholics for food use.

Sector

Wine industry (Production).

Food (Use).

State of the art

Today, the advance of oenological techniques and the hygiene in the cellars has brought about a reduction almost Total undesirable substances in the wines produced. Without However, there are substances that are produced essentially during the  fermentation process and whose presence has not yet been demonstrated That is beneficial for the quality of the final product. Between them Acetic acid and its derivative acetate occupy an important place of ethyl, whose presence in relatively small proportions (> 1 gram / liter in the case of acetic acid) produces a serious deterioration in the quality of the wines that contain it. Since time immemorial excess acetic acid and ethyl acetate in the wines has been the cause of the so-called "acetic chopped" that has caused, especially in the past, countless losses economic.

Wines, in general, contain after fermentation a quantity of acetic acid variable between 0.1 and 0.4 grams / liter, and its presence in these proportions is inevitable (reference Emile Peynaud, Practical Oenology, Ed. Mundiprensa Books, 1999) since it is intrinsically linked to fermentation alcoholic Its concentration will be higher or lower depending on the class of yeast that is used, the health of the grape, the temperature of fermentation, etc., and at the same time it increases with the aging as a result of the aeration of the wines and the subsequent action of acetic bacteria, always present in The cellar environments. The laws in force in different countries allow a maximum acetic acid content of the order of 1 gram / liter and, therefore, wines with higher contents are considered unfit for consumption, being necessary to allocate them to distillation.

In spite of the great advances in matter oenological, there is no acceptable way to reduce the volatile acidity in wines (acetic and ethyl acetate) by use of conventional physical techniques. Vacuum distillation does not It is effective for the reduction of acetic acid due to the high point boiling this one. The decrease in acidity content volatile that owns a wine can be obtained, as of today, only by one method: mixing it with another volatile acidity Minor. This is a risk and this can trigger the appearance of an undesirable microbial activity that leads to content in acetic acid higher than normal.

When the wine exceeds a volatile acidity of 0.7 g / l a practice is used that combines two joint techniques: reverse osmosis and anion exchange resins. A patent granted in 1954 (US2682468 US Process of treating wines) proposes the exchange of anions in wine as an acetic acid reduction system; The method implies a direct contact between the wine and the resins, and the same text indicates that there is a substantial loss of aromas. There is a reference to cation exchange membranes " Ph modification of Cynthiana wine using cationic exchange ", Walker T, Morris J, Threlfall R, Main G, Journal of Agricultural and food chemistry, 50 (22) 6346, 2002).

In 1994 another patent in the US (Apparatus and method for removing compounds from a solution No. US 5,480,665) advocates an effective means for the reduction of acetic acid and ethyl acetate and that does not alter the composition or character of The treated wines. The process consists of temporary separation of wine, by reverse osmosis, of a colorless permeate constituted by water, alcohol and volatile acidity and a return that It contains the other substances that give color, flavor and character to the came. Said permeate passes through a series of exchange resins phonic that separate acetic acid from water and alcohol, which are combined again with the retentate continuing the process until the level of acetic acid has been reduced to the level wanted. Process studies have been carried out by different entities with satisfactory results but also argue that given the complexity of the process the treatment must be limited to the reduction of excess acetic acid with certain guidelines to continue as they are: that adsorption resins must be of type weak base, which can only be treated a minimum part of the wine, etc.

The procedure requires the use of high pressures and chemicals that undoubtedly they can contribute to the deterioration of a product as delicate as the came. This procedure, according to our information, although allowed in the US, Switzerland and Australia, is prohibited by the European Union legislation and must first be incorporated as practice admitted to the OIV (Groupe d'Experts sur le Technologie du Vin) where it is in full discussion.

There are other processes, of difficult effectiveness to value, which use osmosis instead of dialysis (Process and plant for the separation of undesirable substances from alimentary liquids, in particular from wine. (Publication number EP1412063 / US2003235640)). Other processes, less effective than described here, in addition to using several stages, involve the addition of sodium hydroxide or bicarbonate (Process and apparatus for wine treatment to reduce its contents of volatile acidity. (Number of Publication EP1481051 / US2004197439)).

Description of the invention - Brief description of the invention

The technique described below allows to reduce, in hydroalcoholic liquids such as wine, cider, etc. for human consumption, the content of acetic acid and eventually of ethyl acetate in short periods of time and without application of potential gradients not allowed by legislation, such as for example pressure gradients.

It is a separation by dialysis through of a membrane, where the only potential of the process is the concentration gradient The membrane structure allows that there is a rapid initial flow of acetic acid, followed by one somewhat slower than ethyl acetate, and finally, temporarily very away, the flow of other species present in this type of Beverages: larger molecular acids, polyphenols, sugars, etc This peculiar distribution of the flow of each of the species across the membrane makes it possible to eliminate a minimum 25% acetic acid without elimination detectable by HPLC Chromatography or Ultraviolet Spectroscopy of other species present.

- Detailed description of the figures

Figure 1: Device used in the example set out in section 5.

Figure 2: pH and absorbance values of the UV band at 201 nm measured in aliquots obtained from the chamber dialyzer for sample wine (solid symbols) and for standard solution of 0.6 g / l acetic acid (open symbols). The absorbance of the band at 201 nm. is proportional to the concentration of acetic acid in the wine in section I, not being proportional in section II. Section (I): The pH decreases rapidly to as acetic acid balances its concentration on both sides of the membrane, the UV absorption of the 201 nm band increases by similar way in the experiment with standard solution and with wine shows. The striped band represents the slowdown of the pH decrease Section II: The pH is not modified, the band of absorption at 201 nm continues to increase for the sample wine and it stabilizes for the standard solution.

Figure 3: pH and absorbance values of the UV band at 201 nm measured in aliquots obtained from the chamber dialyzer as a function of time for sample wine +0.5 gr / l of acetic acid (solid symbols) and for the standard solution of 1 g / l acetic acid (open symbols). The absorbance of the band at 201 nm is proportional to the concentration of acetic acid in section I not being proportional in section II. Section (I): The pH decreases rapidly as acetic acid balances its concentration on both sides of the membrane, the UV absorption of the 201 nm band. similarly increases in the experiment with standard solution and with sample wine. The striped band represents the slowdown of the pH decrease. Section (II): The pH is not modify, the absorption band at 201 nm. keeps increasing for the Sample wine and stabilize for the standard solution.

- Detailed description of the invention

The device used (figure 1), consists of two stainless steel chambers, in one the drink is introduced hydroalcoholic (wine, beer, cider, its derivatives and its partially de-alcoholic derivatives) that you wish to deacidify, camera which will be called A from now on and in the other the hydroalcoholic solution of the same concentration in alcohol as the drink, that is, the dialysate solution (Chamber B). These cameras are joined by a centerpiece where the membrane used for dialysis. The three pieces are assembled by means of a special flange making a tight seal on the entire system. Each chamber has two exit holes; in camera A one is used to introduce the sample and into chamber B for the aliquot extraction or replacement of the dialysate solution. The remaining hole is used to introduce a mechanical stirrer so that the concentration in each chamber is homogeneous and does not produce concentration gradients within one's own camera.

The centerpiece (or disk) consists of two parts: one, the external part that with two o-rings makes closure sealed between the two chambers, and the inner part, which is where insert the membrane capable of reducing the acid concentration acetic. Said membrane is placed between two grilles to keep it stretched while the entire system closes. This part which contains the membrane closes with the centerpiece of the set-up by means of the corresponding O-rings and some screws that seal the inner part that It contains the membrane.

The membrane structure will be Teflon type with a commercial thickness of 175 µm that is sufficiently tortuous and with a pore diameter between 0.5 and 1 µm. for allow effective separation of acetic acid (and acetate ethyl to a lesser extent) of all other species contained in dissolution Membranes of other materials were tested as polycarbonate with different pore diameters that did not work adequately.

Watertightness tests of the team with optimal results that allow us to ensure the reliability of the results obtained.

The use of the device is as follows: in chamber A is placed the hydroalcoholic drink whose volatile acidity it is desired to reduce, while dissolution is placed in chamber B suitable dialyzer according to use; in general it will be a dissolution hydroalcoholic of the same concentration as that of the beverage and in case of drinks ethanol must be wine, suitable for consumption human. From the moment both cameras have been filled net transport of species from the drink to the dialysate solution, being the flow of small species (essentially acetic acid) considerably faster than that of the largest species. The flow analysis of each species in the calibration stage indicates the moment at which stop the process, this moment being characterized by a considerable reduction of the concentration of acetic acid in the drinking chamber and the absence of variation detectable by UV and HPLC spectroscopy concentration of the rest of species.

The optimal time to stop the process is characterized by prior calibration. In this calibration, extract aliquots from chamber B, which are analyzed by UV and HPLC spectroscopy, and aliquots of chamber A that are analyzed by volatile acidity detection.

It is important to highlight, on the other hand, that same experiments performed without agitation, led practically the same results, indicating that they do not exist acetic concentration gradients during the process in both cameras simply due to the high diffusion coefficient of acetic acid in both wine and mixture hydroalcoholic

The transport through the membrane has been studied by four complementary methods: spectroscopy UV, pH determination, HPLC and acidity assessment volatile. The first three techniques are applied to the solution dialyzer and the fourth on wine. They are shown below. two embodiments of the invention.

The first technique is used as follows: acetic acid has, in its ultraviolet spectrum, a band a 201 nm., Which is the one to be used to determine the Acetic acid concentration in chamber B. When in chamber A there is only standard hydroalcoholic solution, when the balance of concentration between the two chambers will observe a constant value in the UV absorption of this band. The case of wine It is very different, because in its composition there are many compounds that absorb in the vicinity of 201 nm, so that from a certain moment a deformation is observed and intensification of this band, due to the passage of other compounds from chamber A to B.

PH titration is not able to discriminate some compounds of others, however clearly indicates the moment in which the balance in acidity between chambers is reached. He HPLC analysis of aliquots indicates the presence or absence in chamber B of compounds other than acid acetic, including those that do not involve modification of the ultraviolet or pH spectrum.

Finally volatile acidity is a technique that It is used routinely in oenology and practiced on the wine of chamber A at the end of the experiment will report the reduction Effective of this parameter after treatment.

Examples of embodiment of the invention Example 1

With stirring, sample wine with acidity of 0.55 g / l. Calibration performed with 13% hydroalcoholic solution and with 0.6 g / l acetic acid.

Determination of acetic acid in the dialysate solution by UV spectroscopy

As can be seen in Figure 2, during first 72 h the flow originating from the standard solution of Acetic acid and from wine is the same within experimental error.  Analytical detection techniques (HPLC) confirm the flow in that time interval (0-72 h) exclusively from acetic acid and small amounts of ethyl acetate. TO from 72 h, however, it is detected by UV spectroscopy and by HPLC the presence of other species of wine. The moment optimal stopping of the separation process is marked on the graph.

PH determination in the dialysate solution

Figure 2 shows the evolution over time of the pH in the dialysate solution when in chamber A there is a concentration of 0.6 g / l in solution and when there is sample wine. As seen in the graph in the first 50 h, the pH reaches a minimum at which it stabilizes, which reasonably coincides with the plateau of acetic acid concentration observed in the standard solution by UV spectroscopy.

Example 2

With stirring, sample wine with acidity of 0.55 g / l to which 0.5 g / l acetic acid has been added. Calibration made with 13% hydroalcoholic solution and with 1 g / l acetic acid.

Determination of acetic acid in the dialysate solution by UV spectroscopy

By adding more acetic acid in chamber A, the results are very similar to the previous case; the decrease in pH is observed both when using acetic acid standard solution and when using acidified wine, and in the same way it is observed, in the study of the intensity of the band at 201 nm, the plateau when standard solution is used and the continuous one progression of that band when using acidified sample wine.

Claims (7)

1. Device for reducing volatile acidity in hydroalcoholic solutions characterized by understanding a) A chamber, receptacle or reservoir of material that does not alter the composition of the solution as per stainless steel example, in one the solution or drink is introduced hydroalcoholic to be deacidified (Chamber A). b) A chamber, receptacle or reservoirs of material that does not alter the composition of the solution where introduces another hydroalcoholic solution of equal concentration in alcohol than the drink, that is, the dialysate solution (Chamber B) c) A communication between a) and b) separated, by a porous and non-dense membrane for acetic acid dialysis Y d) A recharge system of a) and b) e) Optionally a) and b) may include a mixing device to avoid internal gradients being able to operate cameras A and B in discontinuous or continuous, in the second case with a flow dice. 2. Device for reducing volatile acidity in hydroalcoholic solutions according to claim 1, characterized in that it is a) and b) two sealed stainless steel chambers, so that a) it has an outlet and an inlet opening to introduce the beverage or solution to deacidify and b) has another hole for extraction or replacement of the dialysate solution, both chambers are separated by c) a central part where the dialysis diaphragm is inserted, fixed between two grids by two o-rings and assembled by a special flange making a tight seal on the entire device. 3. Device for reducing volatile acidity in hydroalcoholic solutions according to claims 1 and 2, characterized in that the structure of the membrane in c) is Teflon type with thickness 175 µm, is sufficiently tortuous and with a pore diameter between 0, 5 and 1 µm. to allow effective separation of acetic acid (and ethyl acetate to a lesser extent) from all other species contained in the solution. 4. Device for reducing volatile acidity in hydroalcoholic solutions according to claim 3, characterized in that the membrane structure results in a flow of acetic acid (and to a lesser extent ethyl acetate) temporarily far from the flow of the other species present in this type of drinks: acids of greater molecular size, such as polyphenols, sugars, eliminating 25% of acetic acid in periods of time less than half the time necessary for the rest of species to be detected. 5. Procedure for reducing volatile acidity in hydroalcoholic solutions characterized by using the device of claims 1 to 4 using a concentration gradient. 6. A process for reducing volatile acidity in hydroalcoholic solutions according to claim 5, characterized by using a polymeric membrane according to claim 4, which allows the flow through the membrane caused by the concentration gradient to eliminate a minimum of 25% of the acid. acetic acid without elimination detectable by HPLC Chromatography or Ultraviolet Spectroscopy of species of molecular size greater than acetic acid, except for ethyl acetate. 7. Procedure for reducing volatile acidity in hydroalcoholic solutions according to claim 5 and 6, characterized in that it is concluded when, from the calibration carried out with standard solutions, the decrease in pH is observed. It slows below 2/3 pH units / hour in the device of claims 1.