DE102015109344A1 - Process and apparatus for removing or reducing nitrogen or sulfur compounds from liquid foods or precursors thereof - Google Patents

Abstract

The invention relates to a process for the removal or reduction of the odor or taste negatively affecting nitrogen or sulfur compounds from liquid foods or precursors thereof, which compounds diffuse through a membrane and are thus converted or adsorbed so that their diffusion back into the liquid food becomes impossible.

Description

The invention relates to a process for the removal or reduction of nitrogen and / or sulfur compounds from liquid foods or precursors thereof, and to an apparatus for carrying out the process.

As with any organic product, wine is sometimes subject to strong fluctuations in quality and taste. An undesirable influence on smell, taste and appearance can result in high losses for the producer.

Weinfehler is a collective name for unwanted taste, smell or visual impressions in the wine. These can either be produced during production (eg during fermentation), brought into the wine during storage (eg oxidation) or through external materials (eg cork faults). If the deficiencies are caused by microorganisms, they are called wine sickness.

In addition to cloudiness, odor and taste defects due to microbiological metabolites and chemically caused color, odor and taste defects are of great importance. Thus Essignote or Lösungsmittelton can arise by the presence of acetic acid or ethyl acetate.

As a mousse is a rare occurring Fehlton called, reminiscent of ammonia and the smell of mouse harn. Although the cause has not been fully elucidated, heterocyclic nitrogen compounds such as acetylpyrroline (ACPY) are considered to be important causative agents. In addition, two other important causative agents are two isomers of 2-acetyltetrahydropyridine, such as 2-acetyl-3,4,5,6-tetrahydropyridine, 2-acetyl-1,4,5,6-tetrahydropyridine, 2-ethyltetrahydropyridine and 2-acetyltetrahydropyridine. acetyl-1-pyrroles.

An important class of flavorings in wine are derivatives of methoxypyrazine. Examples of such compounds are IBMP (2-isobutyl-3-methoxypyrazine) and IPMP (2-isopropyl-3-methoxypyrazine). Methoxypyrazines enter the wine from unripe grapes, but also from grape leaves or as secretions of certain insect-infested insects. This can lead to a grassy, vegetal taste and smell impression.

An error recently described is called an untypical aging sound (UTA). This can affect white wines already at a relatively young stage. Such wines are recognized in the smell of unwanted aroma notes after mothballs, naphthalene, acacia flowers, soap, washing powder or washing machine. In taste, they have a disturbing bitterness, are short in the finish and usually of a pale color.

The essential impact substance responsible for UTA was identified as 2-aminoacetophenone (AAP), which is already detected in very small amounts of <1 μg / l. This error is particularly associated with drought stress on the plant during ripening, inadequate nutrition, high yield and inadequate grape ripeness. Due to global climate change, the importance of this error has increased.

The perceived threshold for the perception of AAP in white wines is 0.5-1 μg / l, with the perception threshold being significantly dependent on the wine matrix. The formation of AAP takes place predominantly chemically from the odorless precursor stage indole-3-acetic acid, which in turn represents a degradation product of the amino acid tryptophan.

So far there is no way to remove AAP from wines or to reduce the content.

Another mistake, the so-called "foxtone", is associated with methyl anthranilate, another aromatic amine. For wines obtained from non-vinifera grape varieties and the z. For example, if grown and marketed in the US and Canada, this Foxton is even distinctive and accepted by the consumer.

Other nitrogen compounds in the wine are biogenic amines, especially degradation products of amino acids. They are predominantly formed by certain strains of bacteria that undergo spontaneous malolactic fermentation in the wine (transformation of malic acid into lactic acid), but also by fungi that colonize rotten grapes.

There are also wine defects caused by sulfur compounds. As Böckser a wine defect is referred to, which is caused by volatile, foul-smelling sulfur compounds such as mercaptans or hydrogen sulfide. The yeast can enzymatically reduce sulfite ions, which are introduced into the wine by sulfurization, into hydrogen sulphide, a substance with a typical smell of rotten eggs. This wine defect is found especially in young wines. If this is not recognized in time or even overlooked, it can develop into a so-called "Lagerböckser". This is due to various (sometimes not fully clarified) subsequent reactions to the formation of volatile sulfur compounds, in particular of ethyl and methyl mercaptan. The smell such mercaptans are reminiscent of burned gum, garlic, rotten onions, rotten eggs, cooked cabbage, etc.

As a preventive measure against Böckser, the turbidity of the must should be removed as part of the must preclarification or yeast strains used for fermentation, which are characterized by a low tendency to form such volatile sulfur compounds. Already existing wine defects of this kind can be corrected by the addition of copper compounds or silver chloride.

However, such a treatment of the wine is problematic, since other characteristics of the wine can be changed by the treatment agents used. In addition, the legal provisions allow only very limited the addition of such auxiliaries, which incidentally later have to be separated again.

Especially nitrogen and sulfur compounds lead to very disturbing wine defects. In addition, UTA often occurs only during the maturation of the wine. At this time, a treatment of the wine is only very limited possible.

Although the causative agents of most wine defects are known, it is difficult to remove selected compounds from the wine without altering the sensory properties of the wine or leaving residues of the treating agent in it. Moreover, the addition of substances for fining is permitted only within narrow limits and also the subsequent separation of such additives can be difficult. It is often sufficient that the content of compounds causing wine defects is only reduced below their odor or taste threshold value.

In addition to cations and anions, wine also contains a large number of organic molecules from the grape and the metabolism of the microorganisms involved in the vinification, which are of great importance for the taste, smell and appearance.

There are known analytical methods by which organic components can be extracted from an aqueous matrix by offering them a hydrophobic medium in which they dissolve better. This medium may also be a hydrophobic solid. This is used, for example, to determine volatile organic compounds (VOCs). This is z. For example, a polydimethylsiloxane (PDMS) coated stir bar is placed in a sample. According to their octanol-water partition coefficient, volatile organic compounds diffuse from the aqueous phase into the PDMS. For analytical determination, the adsorbed volatile compounds are subsequently extracted from the PDMS, e.g. B. by thermal desorption.

From viticulture methods are known to remove so-called volatile acid. US6913776 describes a method for removing unwanted substances from wine. Volatile substances are transferred from the wine into an alcohol-containing extraction liquid via a porous hydrophobic membrane (polypropylene, polytetrafluoroethylene). The extraction liquid is purified via a circuit which may also contain an anion exchange column. The method is mainly used for the removal of volatile acid or ethyl acetate.

Out Ferreira et al. (New Insights into Membrane Science and Technology: Polymeric and Biofunction Membranes; Editors D. Bhattacharyya, DA Butterfield; Elseviers Science BV 2003; Chapter 8: Fereira et al Membrane Aromatic Recovery System (MARS) - A new process for recovering phenols and aromatic amines from aqueous streams; pp. 165-181;) is known that z. B. Aniline can be extracted from industrial wastewater by diffusion through a silicone membrane (0.5 mm thickness) in a highly acidic solution (pH below 1). Since large volumes are extracted, the pH is constantly updated.

The object of this invention is to provide a method for removing or reducing nitrogen and / or sulfur compounds from liquid foods or precursors thereof.

solution

This object is achieved by the inventions having the features of the independent claims. Advantageous developments of the inventions are characterized in the subclaims. The wording of all claims is hereby incorporated by reference into the content of this specification. The inventions also include all reasonable and in particular all mentioned combinations of independent and / or dependent claims.

• a) Kontaktieren des Lebensmittels mit einer Seite einer Membran;
• b) Diffusion der zu entfernenden oder zu vermindernden Substanzen in und durch die Membran hindurch;
• c) Umwandlung und/oder Adsorption der Substanzen in einer Weise, dass eine Diffusion dieser Substanzen zurück in das flüssige Lebensmittel oder die Vorstufen davon ausgeschlossen ist.

The object is achieved by a process for the removal or reduction of basic compounds or sulfur compounds from liquid foods, comprising the following steps:

• a) contacting the food with one side of a membrane;
• b) diffusion of the substances to be removed or reduced into and through the membrane;
• c) Conversion and / or adsorption of the substances in such a way that diffusion of these substances back into the liquid food or the precursors thereof is excluded.

The reduction may also include a complete removal.

In the following, individual process steps are described in more detail. The steps do not necessarily have to be performed in the order given, and the method to be described may also have other steps not mentioned.

Liquid foods or precursors thereof are liquids or liquids suitable for consumption, which are processed into such. These further steps may be, for example, dilution, filtration and / or fermentation processes. Examples of such liquid foods are fermented or unfermented fruit juices. These may be fruit juices which are directly consumable, or precursors from processing, such as must or concentrates. Other examples of such liquid foods are liqueurs or distillates.

In a first step, the foods or precursors thereof are contacted with one side of a membrane.

It is preferably a hydrophobic membrane. Hydrophobic membrane means that the material of the membrane is substantially water-insoluble and immiscible with water. In this case, water-insoluble means that the membrane or the material forming the membrane is soluble in water less than 50 ppm, preferably less than 30 ppm, in particular less than 10 ppm.

The membrane is preferably non-porous.

Such a membrane ensures that only sufficiently non-polar compounds can traverse the membrane.

The material of the membrane must therefore have a suitable polarity in order to form a solution space for the compounds to be depleted. Such materials are also known from solid phase extraction (SPE) or solid phase microextraction (SPME).

It is preferably a polymer membrane.

The material can be adapted according to the application. Preference is given to materials which have already been approved for use with foods. Examples are membranes based on silicones (polyoctylmethylsiloxane (POMS), polydimethylsiloxane (PDMS)), N-vinylpyrrolidone, polyetherimides, polyimides, acrylates, methacrylates or copolymers thereof.

In order to achieve sufficiently selective extraction of the basic compounds and sulfur compounds, the polymers of the membrane preferably include heteroatoms such as oxygen or nitrogen. These may be present, for example, in carbonyl groups, ester groups, ether groups, amide groups, hydroxyl groups, amino groups, heterocycles. These can also be present as page groups. Insofar, polyolefins modified with polar groups, such as polyvinyl alcohols, are also suitable. Particularly preferred are polymers based on silicones whose polarity can be varied very well. Thus, copolymers of silicones with other polymers containing the aforementioned heteroatoms or groups, such as ethylene glycol, may also be used. Thus, polymers based on silicones or silicone copolymers are preferred.

Preference is given to membranes based on silicones, such as PDMS. The surface of the membrane can also be treated to obtain a certain hydrophilicity or hydrophobicity of the surface (plasma, UV treatment). This can facilitate the diffusion of the compounds to be removed into the membrane.

The membrane may also contain up to 50 wt .-% additives, such as fillers.

The thickness of the membrane can be chosen differently. Preferred is a thickness of less than 2 mm, in particular less than 1 mm, for example 0.01 to 1 mm, in particular less than 0.8 mm or less than 0.6 mm. Examples are thicknesses between 10 nm to 0.8 mm or 15 nm to 0.6 mm. The thickness can be chosen depending on the requirements of stability and diffusion.

The thickness of the membrane is the rate-limiting parameter for the diffusion of the compounds.

After diffusion through the membrane, the diffused substances are converted and / or adsorbed. The conversion and / or adsorption takes place in such a way that a diffusion of these substances back into the liquid food or the precursors thereof is excluded. As a result, the diffusion through the membrane is maintained. In particular, the conversion and / or adsorption prevents the compounds from being able to diffuse back into the membrane. Thus, no equilibrium can be established between the external medium and the membrane. This promotes continuous diffusion. By a conversion, it is not so important whether the substance passes only slightly from the membrane into the inner compartment.

In one embodiment of the invention, the transformation comprises protonation. The basic compounds are protonated. Preferably, the protonation forms a positively charged group, for example, amino groups are converted into charged ammonium groups. As a result of this increase in their polarity, those compounds can no longer diffuse back through the hydrophobic membrane. This is achieved by having proton sources on the other side of the membrane. This may be an acid with a sufficient pKa.

Examples are inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, or organic acids, preferably mono- or polyhydric carboxylic acids such as citric acid, tartaric acid, malic acid, stearic acid, acetic acid, formic acid, oxalic acid, benzoic acid, vinylogous acids such as ascorbic acid, sulfuric acid esters or sulfonic acids such as p-toluenesulfonic acid, phosphoric acid esters, phosphonic acids, or mixtures of these compounds.

It is also possible to use salts which can still give off protons, for example hydrogen sulfates, hydrogen bases, dihydrogen phosphates, preferably of alkali metals, such as sodium or potassium.

The molar amount of protons which are provided by the proton source is preferably at least as large as is required for the protonation to be removed amount of the compound, in particular at least twice as large. At least one excess is preferred by a factor of 10.

In the case of the liquid foods to be treated, the amount of substance to be reduced is usually determined before the method is used. Depending on what amount of substance is to be removed, the amount of protons required at least can be determined. Frequently, the content of substance to be removed should only be lowered below a certain value, namely the threshold of perception.

In particular, there are conditions in which a protonation of the basic compounds takes place. These conditions can only in certain areas, eg. B. on the functional groups of the ion exchanger.

If only small amounts of water and / or free hydroxyl groups are contained in the medium of the interior, it is possible, for example, to avoid or reduce hydrolysis of optionally diffused aroma esters.

In a preferred embodiment of the invention, the proton source is a cation exchanger, in particular an acidic cation exchanger, wherein the ion exchanger should provide sufficient protons for protonation of basic compounds. The anchor groups of such ion exchangers include carboxylate groups, phosphate groups, sulfonate groups (sulfoethyl groups, sulfomethyl groups or sulfopropyl groups). It can be used with different matrices, for example based on polymers or cellulose ion exchangers, for. Styrene DVB or cellulose. Strongly acidic cation exchangers with sulfonate groups are preferred.

The membrane ensures that the food has no contact with the proton source. Thus, a direct influence of the food by the proton source is excluded. Such an effective separation between food and proton source thus allows the use of agents whose direct contact with the food is excluded due to legal requirements.

In addition, the conditions of the process can be very selectively adapted to the substance / substance group to be extracted.

Basic compounds to be removed from the liquid food are nitrogen-containing compounds, in particular amines or heterocyclic bases. Preferred are aromatic amines such as 2-aminoacetophenone or heterocyclic bases such as pyrazines. Examples of such compounds are 2-aminoacetophenone or 2-methoxypyrazines, in particular MDMP.

In particular, the basic compounds to be reduced are present only in small amounts, in particular in concentrations of less than 10 μg / l. Surprisingly, the process according to the invention was suitable for the treatment of liquids with such low concentrations.

In a further embodiment of the invention, thiophilic compounds are arranged on the inner side of the membrane. These are understood to mean compounds, complexes or surfaces which react with sulfur-containing compounds, in particular with SH groups. These are preferably copper and / or silver compounds, in particular copper and / or silver ions. Sulfur compounds, in particular foul-smelling volatile organic sulfur compounds, diffuse through the membrane and form salts with the thiophilic metal compounds, ie the durchiffundierten compounds are converted accordingly and thus immobilized. Thus, these sulfur compounds are removed from the food.

The copper and / or silver ions can be obtained, for example, by introducing and at least partially dissolving the corresponding salts or precursor compounds. For this purpose, a corresponding salt solution can be present on the other side of the membrane. Alternatively, elemental silver or copper may be present, with the sulfur-containing compounds binding to the surface of the metal. It may, for example, be metallic plates, grids, nets, chips or powder.

The copper and / or silver ions can also be present in a matrix, for example an organic or inorganic compound which has corresponding binding sites. The ions may, for example, be bound in an ion exchanger. Due to the higher affinity of the copper and / or silver ions for the sulfur compounds, they are still able to bind the sulfur compounds.

Possible copper salts are, for example, copper chloride, copper sulfate, copper hydroxide, copper (I) oxide, copper (II) oxide, copper salts of organic acids, preferably mono- or polyhydric carboxylic acids, such as citric acid, tartaric acid, malic acid or stearic acid.

The arrangement behind the membrane is particularly avoided that the metal compounds must be added directly to the wine. Thus, a later removal of possibly too much added copper and / or silver ions from the product becomes superfluous. So far, when using z. B. in wine excess copper be removed by a blue shade, which requires elaborate precipitation and filtration and affects the product quality.

The molar amount of copper and / or silver ions which can be provided for the reaction with the sulfur compounds is preferably at least as large as that required for the amount of compound to be removed, in particular twice as large. At least one excess is preferred by a factor of 10.

In the case of the liquid foods to be treated, the amount of substance to be reduced is usually determined before the method is used. Depending on what amount of substance is to be removed, the amount of at least required copper and / or silver ions can be determined. In general, the content of the volatile sulfur compounds should only be lowered below a certain value, d. H. below the sensory perception threshold.

In particular, the sulfur compounds to be reduced are present only in small amounts, in particular in concentrations of less than 100 μg / L. Surprisingly, the process according to the invention was suitable for the treatment of liquids with such low concentrations.

On the inner side of the membrane, a polar medium is preferably also present.

The medium does not have to be an aqueous solution. Other media may also be used, for example, alcohols, glycols or polyols such as polyethylene glycols. Thereby, the reactivity of the proton source present in the medium or the thiophilic compound can be controlled.

The medium on the inner side of the membrane is liquid to solid. It is not gaseous. It may be, for example, a liquid, a paste or a solid. In the liquid or paste solid bodies may be present, for. B. granules of an ion exchanger.

The process can be carried out at various temperatures, for example at 5 to 30 ° C.

The process is preferably used at a pressure of less than 4 bar, in particular less than 3 bar, preferably without an elevated pressure.

The method preferably does not include a step of reduced pressure, such as pervaporation.

Preferably, the concentration-of-concentration difference caused by the conversion and / or the adsorption or chemisorption is the driving force for the diffusion of the target molecules from the food through the membrane into the capsule.

The duration of the contacting can be chosen differently and also depends on the content and the chemical nature of the compounds to be reduced. It can be a contact for several hours to several days or weeks. The liquid food can be mixed during this time.

In a preferred embodiment of the invention, the medium on the inner side is not actively agitated or pumped during the process. It is preferably static. This allows that the process requires no expensive equipment. However, it is possible that the liquid food is mixed during the period of contact with the membrane.

It is also possible that the medium is guided on the inner side as an extraction circuit and is cyclized, for example, via the cation exchanger or bound copper and / or silver compounds.

During the process, the decrease in the compounds to be reduced can be controlled. When an appropriate level is achieved in the liquid food or precursor thereof, the contacting of the membrane with the food or precursor is terminated.

The method can be applied to different liquid foods or precursors thereof. Preference is given to fermented or unfermented fruit juices on the basis of grapes, preferably with a base of grapes in the volume of at least 50% by volume. Fruit juices are preferred in the context of the production of wine. This may be the unfermented grape must or the fermented grape must.

Particularly preferred is the application to fermented fruit juices based on grapes. Especially through the fermentation process and storage, the substances to be reduced by the method according to the invention can be formed.

The invention also relates to a device for carrying out the method according to the invention.

The invention also relates to an apparatus for removing or reducing basic compounds or sulfur compounds from liquid foods or precursors thereof, which comprises at least one inner compartment and at least one membrane, wherein at least one membrane is arranged such that diffusion through this membrane between an inner compartment Compartment and a device surrounding the medium is possible, wherein the surrounding medium is the liquid food or a precursor thereof.

There is no mixing of the inner compartment and the liquid food or precursor thereof. There is only a mass transfer by diffusion through the boundaries of the inner compartment, in particular by the at least one membrane.

Means for converting and / or adsorbing the compounds are present in at least one inner compartment, it being possible for the device to be introduced into a medium containing the substances to be reduced, via at least one membrane to diffuse the compounds into at least one inner membrane Compartment takes place, wherein the compounds are converted or adsorbed in the inner compartment.

In one embodiment of the invention, the means for converting or adsorbing the compounds are selected from at least one proton source or at least one thiophilic compound. Preferred are agents as described for the method.

The device may also comprise several compartments, each with different means.

In a preferred embodiment, at least one proton source is present in the inner compartment. In this case, the device is one for removing or reducing nitrogen compounds. Preferred proton sources are described for the method.

In a further preferred embodiment, at least one thiophilic compound, in particular at least one copper and / or silver compound, is arranged in the inner compartment. Preferred such compounds are described for the method.

In one embodiment of the invention, the volume of all internal compartments of the device is less than 1/100 of the volume of food to be contacted.

In one embodiment, the membrane constitutes at least 20% of the inner surface of all inner compartments. Hydrophobic membrane means that the material of the membrane is substantially water-insoluble and immiscible with water. In this case, water-insoluble means that the membrane or the material forming the membrane is soluble in water less than 50 ppm, preferably less than 30 ppm, in particular less than 10 ppm.

The at least one membrane is preferably non-porous. The mass transfer through the membrane takes place only by diffusion through the material of the membrane.

Such a membrane ensures that only sufficiently non-polar compounds pass through the membrane.

The material of the membrane must therefore have a suitable polarity in order to represent a solution space for the compounds to be reduced.

Such materials are known from solid phase extraction (SPE), solid phase microextraction (SPME) or stir bar sorptive extraction (SBSE).

The material can be adapted according to the application. Preferred are materials which are approved for use with food. Examples are membranes based on silicones (polyoctylmethylsiloxane (POMS), polydimethylsiloxane (PDMS)), N-vinylpyrrolidone, polyetherimides, polyimides, acrylates, methacrylates or copolymers thereof.

In order to achieve sufficiently selective extraction of the nitrogen and sulfur compounds, the polymers of the membrane preferably include heteroatoms such as oxygen or nitrogen. These may be present, for example, in carbonyl groups, ester groups, ether groups, amide groups, hydroxyl groups, amino groups, heterocycles. These can also be present as page groups. Insofar, polyolefins modified with polar groups, such as polyvinyl alcohols, are also suitable. Particularly preferred are polymers based on silicones whose polarity can be varied very well. Thus, copolymers of silicones with other polymers containing the aforementioned heteroatoms or groups, such as ethylene glycol, may also be used. Thus, polymers based on silicones or silicone copolymers are preferred.

Preference is given to membranes based on silicones, such as PDMS.

The membrane may also contain up to 50 wt .-% additives, such as fillers.

The thickness of the membrane can be chosen differently. Preferred is a thickness of less than 2 mm, in particular less than 1 mm, for example 0.01 to 1 mm, in particular less than 0.8 mm or less than 0.6 mm. Examples are thicknesses between 10 nm to 0.8 mm or 15 nm to 0.6 mm. The thickness can be chosen depending on the requirements of stability and diffusion.

The thickness of the membrane determines the rate of diffusion of the volatile compounds.

If multiple membranes are present, not all must be the same material. Preferably, all membranes are made of the same material.

The device can be designed very differently. In one embodiment, the device is designed as a hollow body whose outer walls at least partially comprise a membrane according to the invention. The interior of the hollow body corresponds to the inner compartments. The hollow body may be cylindrical, cube-shaped, cuboid, flat or irregular. Depending on the type of use, it does not have to be completely closed, as long as it is ensured that when it is used, the liquid food can not get into the inner compartment.

The device may comprise means for opening and closing the hollow body. This allows the replacement and / or renewal of the contents of the inner compartments or the inner compartments depending on the usage. This can be, for example, a screw cap or a clamp connection.

In addition to the at least one membrane, the boundary walls of the device forming the inner compartment can be made of any materials approved for use in liquid foods. These can be plastics, glass or metallic materials.

The internal volume of the device is preferably at least 100 times less than the volume of the liquid food or precursors thereof to be treated.

In another embodiment of the invention, the device in the inner compartment comprises an ion exchanger, wherein the material of the membrane has been applied to at least part of the surface of the ion exchanger. The ion exchanger can additionally be applied to a carrier material. The material of the membrane on the surface of the ion exchanger simultaneously forms the membrane. The ion exchanger completely fills the inner compartment.

Such a device can be obtained, for example, by enclosing ion exchangers, preferably in the form of granules, with the material of the membrane. Such granules can be added to the liquid food in a simple manner and removed again by filtration or sedimentation.

For applying the ion exchanger on a support, the ion exchanger is preferably applied to a support, which consists for example of a planar flat body made of a flexible material, and coated the carrier with ion exchange with the membrane-forming material, coated or laminated. In this way, surfaces can be obtained which have the desired effect.

The device according to the invention is preferably completely or at least partially introduced into the liquid food to be cleaned. This means that at least a part of the membrane is contacted with the liquid food.

In one embodiment, the device is designed as a completely insertable into the liquid food capsule. As a result, devices with a specific capacity of compounds to be reduced can be obtained, for example. Depending on the amount of compounds to be reduced, the number and duration of application of the capsules can be determined. In such an application, no filtration or pumping of the liquid food is necessary, which can often lead to quality losses.

In a further embodiment of the invention, the device comprises as acidic cation exchanger correspondingly modified cellulose, for. B. with sulfonyl or phosphoryl groups, which is coated with the material of the membrane, for example PDMS. This structure allows the construction of areal cation exchangers, which can be easily introduced into the liquid to be treated.

Thus, a sheet of cellulose, for. B. blotting paper, are functionalized to an acidic ion exchanger and coated with the appropriate membrane.

Further details and features will become apparent from the following description of preferred embodiments in conjunction with the subclaims. In this case, the respective features can be implemented on their own or in combination with one another. The possibilities to solve the problem are not limited to the embodiments. For example, area information always includes all - not mentioned - intermediate values and all imaginable subintervals.

The embodiments are shown schematically in the figures. The same reference numerals in the individual figures designate the same or functionally identical or with respect to their functions corresponding elements. In detail shows:

1 Course of UV-VIS absorption of the different samples;

2 Schematic representation of the method according to the invention;

3 Schematic representation of the conversion of amines by protonation;

4 Schematic representation of a membrane according to the invention with ion exchanger; and

5 Schematic representation of an embodiment of the invention;

6 Schematic representation of an embodiment of the invention;

7 Schematic representation of an embodiment of the invention.

2 shows a schematic sequence of the method according to the invention. First, the membrane is contacted with the liquid food 100 , This leads to the diffusion of the substances to be reduced through the membrane 110 , These are appropriately converted or adsorbed after passing through the membrane 120 ,

3 shows a schematic representation of the conversion of amines by protonation. The amines (R-NH ₂ ) in the external medium, ie the liquid food 210 diffuse into the membrane 200 and through the membrane into the inner compartment 220 , There they are protonated to R-NH ₃ ⁺ . Charged ammonium ions can not diffuse back into the membrane and are therefore removed from the equilibrium between the inner compartment and the membrane. This promotes the diffusion of other amines from the outer medium into the membrane.

4 shows a schematic representation of the method using an ion exchanger. The compounds (nitrogen and / or sulfur compounds) diffuse from the external medium 210 in the membrane 200 , On the other side of the membrane in the inner compartment 220 is an ion exchanger 230 arranged. This may be an acidic cation exchanger in the case of the nitrogen compounds to protonate the nitrogen compounds. In the case of sulfur compounds, it may be a copper ion-loaded ion exchanger.

5 shows a cross section through an embodiment of the device according to the invention. This includes an outer wall 300 and at least one membrane 310 , These enclose an inner compartment 320 , In this compartment can be an ion exchanger 330 be arranged. The inner compartment is completely closed so that mass transfer can only take place by diffusion. Such a device can be completely surrounded by the medium to be cleaned, or be introduced into this in a simple manner.

6 shows a further embodiment. In this case is an interior 420 , or even a carrier material such as an ion exchanger, completely of a coating 420 jacketed. These Coating is also the membrane. In this embodiment, the device resembles a coated granule. This in turn can be easily introduced into the medium to be cleaned.

7 shows in the figures a) to d) an embodiment of the invention. Here is the device 500 executed as a flat body similar to a leaf. This can, for example, be rectangular, as shown in a). The shape can however be adapted according to the use. b) shows a cross section through this embodiment. It shows 510 the membrane and 520 the interior, which is preferably filled in this case with an ion exchanger. The ion exchanger is preferably a cellulosic sheet modified as an acidic ion exchanger. The leaf 520 is on both sides with the material of the membrane 510 coated. In c) it is shown that the material of the membrane 510 prefers the whole sheet 520 envelops. This type of device has a particularly large surface area for diffusion and can be easily manufactured. As shown in d), the capacity can be easily increased, in which several leaves 540 be used side by side. As a result, the capacity of the device can be easily adapted to the application.

Examples

1.1 Encapsulated ion exchanger

From a PDMS monomer mixture, thin films having a thickness of 0.1 to 0.3 mm were cast. With such a film, an annular piece of a silicone tube (1.5 cm diameter, length 8 mm) was closed on one side. In the resulting cavity, a cation exchanger (in H ⁺ form) was filled and the open end of the silicone tube also sealed with one of the cast films. Thus, a drum-shaped cylinder was obtained, which has a membrane according to the invention on both sides. The inner compartment is formed by the silicone tube and the two membranes. A mass transfer outside - inside is only possible by diffusion, especially through the membrane.

A capsule so formed was placed in a model wine (500 mL) containing 2-AAP (100 mg / L). The content of 2-AAP was analyzed daily (UV-Vis spectroscopy at 362 nm, the main absorption of 2-AAP, PCIE). The control used was a capsule filled with Na.sup. ⁺ Ion exchangers and a sample without addition of a capsule (Control). The measured values shows 1 , It can be clearly seen that only in the capsule with ion exchanger in the H ⁺ form, the content of 2-AAP significantly decreases.

1.2. Sodium bisulfate

NaHSO ₄ and glycerol (propane-1,2,3-triol) were triturated to a pasty crystal pulp and filled in place of the ion exchanger in a capsule analogous to Example 1. This capsule was placed in a solution of 2-AAP and the vessel sealed airtight. After about 10 days, any odor of 2-AAP had disappeared over the solution.

2.2. Removal of thiols

The under 1.1. described capsule was filled with a Cu ²⁺ -loaded IDA ion exchanger and added to a "böcksrigen" wine. After a short time, the wine error could no longer be detected by sensor. In addition, no copper ions could be detected in the wine.

2.3. Encapsulation on a support

A strip (1 × 5 cm) of a nonwoven fabric was coated with a Cu ²⁺ -loaded IDA ion exchanger (see 2.2.) And completely coated with PDMS. To 100 ml of a dry white wine was added approximately 10 mg of NaS nonahydrate with one drop of 2M HCl. There was a distinct smell of H ₂ S. The encapsulated ion exchanger applied to the support was placed in this mixture and the vessel was closed. Within a week, the bright blue of the ion exchanger turned into a brownish-black, while the smell of hydrogen sulfide significantly decreased.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6913776 [0020]

Cited non-patent literature

• Ferreira et al. (New Insights into Membrane Science and Technology: Polymeric and Biofunction Membranes; Editors D. Bhattacharyya, DA Butterfield; Elseviers Science BV 2003; Chapter 8: Fereira et al Membrane Aromatic Recovery System (MARS) - A new process for recovering phenols and aromatic amines from aqueous streams; pp. 165-181;) [0021]

Claims (11)

 A process for removing or reducing basic compounds or sulfur compounds from liquid foods or precursors thereof, comprising the steps of: a) contacting the food or precursors thereof with one side of a membrane; b) diffusion of the substances to be removed or reduced into and through the membrane; c) Conversion and / or adsorption of the substances on the inner side of the membrane in such a way that diffusion of these substances back into the liquid food or the precursors thereof is excluded. A method according to claim 1, characterized in that the membrane is non-porous. Method according to one of claims 1 or 2, characterized in that on the inner side of the membrane, a polar medium is present. Method according to one of claims 1 to 3, characterized in that the conversion of the compounds comprises a protonation. Method according to one of claims 1 to 4, characterized in that a cation exchanger is arranged on the inner side of the membrane. Method according to one of claims 1 to 5, characterized in that the basic compounds to be reduced are nitrogen-containing compounds. Method according to one of claims 1 to 3, characterized in that thiophilic compounds are arranged on the inner side of the membrane. A method according to claim 7, characterized in that the compounds are copper and / or silver compounds.  Apparatus for carrying out the method according to one of claims 1 to 8.  Device for removing or reducing basic compounds or sulfur compounds from liquid foods, comprising at least one inner compartment and at least one membrane, wherein at least one membrane is arranged so that via this membrane diffusion of the compounds to be reduced between an inner compartment and the one Device surrounding medium is possible, wherein the surrounding medium is the liquid food or a precursor thereof, wherein the compounds in the inner compartment are converted there by means for converting and / or adsorption, and / or adsorbed. Apparatus according to claim 10, characterized in that the means for converting or for adsorption are selected from at least one proton source or at least one thiophilic compound.

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