MXPA99000455A - Method for producing cold-filtered beer - Google Patents

Abstract

The invention relates to a method for producing cold-filtered beer. According to this method, the beer is filtered through a membrane filter which can then be cleaned and re-used. The invention is characterized in that in order to clean the membrane filter, said filter is brought into contact with an aprotically polar solvent and then washed. The inventive method enables the membrane filter used to have a longer service life.

Description

METHOD TO PRODUCE BEER FILTERED IN FRIÓ FIELD OF THE INVENTION The present invention relates to a method for producing beer filtered in cold, in which the beer is filtered through a membrane filter which is cleaned after filtration and used for a new filtration.

BACKGROUND OF THE INVENTION Due to the extended marketing channels, germs have to be removed from the beer to make it storable. Currently, beer is mainly pasteurized for the elimination of germs. For this purpose, beer, for example bottled or canned, is heated to a temperature between 62 and 68 ° C, which destroys germs. However, this pasteurization includes considerable energy consumption. It has the additional disadvantage that the energy supplied can activate chemical reactions that deteriorate the product and are difficult to control. These reactions can adversely affect for example the taste of the product ("pasteurized flavor") and there is also the danger that unwanted substances are formed. In this way, pasteurization is a relatively expensive method of eliminating germs that involves high energy expenditure and consequently, has harmful effects on the environment and occasionally reduces the quality of the product. As an additional germ removal method, cold filtration is known. Cold-filtered beers are offered as so-called "bar-ril beers" for example in the United States of America, in Japan and in Korea. In Europe, these beers are banned because they contain technical enzymes. With these technical enzymes, a disadvantage of the cold filtration inherent in this is counteracted. ^ technique: the rapid clogging of the filter. This obstruction is due to the deposits of the substances separated by filtering the beer on the inlet side of the membrane filter. It is difficult or impossible to remove the deposits from the filter, and the filter life is reduced. This increases the cost of beer production, since membrane filters are expensive. ^ f To prolong the life of the filter, manufacturers of membrane filters recommend cleaning the 20 membranes used by treating them with proteases, glucanases and xylanases, as well as with chemical agents such as surfactants, acids / bases, and with oxidizing agents, thus making them reusable This cleaning can be carried out for example in two stages, where in a first stage cleaning is done with the enzymes mentioned, followed optionally by additional cleaning with the chemical agents mentioned. An exemplary cleaning procedure, for example for a filter area of approximately 320 m, includes enzymatic cleaning after every 5,000 hectoliters (hl) 5 filtered and additional chemical cleaning after every 20,000 hectoliters filtered. The typical duration of the filters with the mentioned filter area subjected to said cleaning is approximately 100,000 hectoliters (hl). However, the known cleaning procedures have the disadvantage that they are only capable of ^ Insufficiently remove deposits on the filter, which causes the cleaning action to decrease considerably as the membrane filter ages.

DESCRIPTION OF THE INVENTION Therefore, an object of the invention is to provide a method for producing beer of the type mentioned initially, in which the problems described above do not occur and increase the durations of the membrane filters. According to the invention, this object is achieved in a method for producing cold filtered beer, wherein the beer is filtered through a membrane filter, said membrane filter is cleaned after filtration and used for a new one. filtration, since the membrane filter for cleaning purposes is brought into contact with an aprotic polar solvent. It has surprisingly been shown that membrane filters can be cleaned better with an aprotic polar solvent than with common cleaning agents such as for example proteases, xylanases and glucanases or surfactants and other substances. By cleaning according to the invention, a substantial increase in the durations of the membrane filters used in beer filtration is achieved. In the method according to the invention, dimethyl sulfoxide, dimethylformamide or tetrahydrofuran are preferably used as aprotic polar solvents. Preferably, the dimethyl sulfoxide is applied in the presence of an alkali metal hydroxide. A preferred embodiment of the method according to the invention is characterized in that the solvent is present as a mixture with water, most preferably between 30 and 100% by mass, based on the total mass of the mixture. The cleaning is carried out conveniently until the current potential and the zeta potential, respectively of the membrane filter, no longer change during the operation. It has been shown that the adjustment of current potential in the membrane filter and the zeta potential calculable therefrom (see below), are good indicators of the magnitude in which, the substances that clog the membrane filter, and They have been removed.

In the following, the invention is described in more detail. As a membrane filter, a NB type filter made of Nylon 66 (manufacturer: Pall Filtrationstcchnik GmbH, Germany) was used. In the prior art, said filter was frequently used for cold filtration of beer. To determine the filtering behavior of a filter, the so-called membrane filter test was applied according to Esser (Monatszeitschrift für Braucrci [Monthly Magazine for Breweries], year 25 number 6 pages 145 - 151, 1972). This test is reliable for revision measurements of the improvement of filtration capacity. To determine the filtering behavior of a new, ie unused, membrane filter, a pressure filtration apparatus (type SM 16526, 200 ml filling capacity, manufacturer: Sartorius GmbH, Gottingen, Germany) was used for a filter membrane made of polyamide and nylon 66 (47 mm, pore size 0.2 μm). Beer cooled to 0 ° C, pressed through the filter under isobaric conditions (1 bar), and the amount of filtrate was weighed every 10 seconds. The test was stopped after obtaining 200 g of filtrate. The result is shown graphically as a diagram in Figure 1. Figure 1 shows that under the conditions indicated above, the 200 g filtrate can be obtained with the unused filter after approximately 210 seconds.

Under identical conditions, the filtering behavior of a clogged, ie used, filter was tested. The result is illustrated in Figure 2, which shows that even in 720 seconds, only about 60 g of the filtrate was obtained. The clogged filter was cleaned according to a method of the prior art, wherein the filter was first cleaned enzymatically and then chemically, as described below. For enzymatic cleaning, the clogged filter was treated for 1 hour with a 1% aqueous solution of a mixture of β-glucanases and xylanases (P3-Ultrasil 65, manufacturer: Henkel) having a pH of 5 (adjusted by means of a 0.05% aqueous solution of a mixture of surfactants and an acid component (P3-Ultrasil 75, manufacturer: Henkel) at a temperature of 50 ° C. Then, this treatment was repeated, then the filter was treated for 3 hours with a 0.5% aqueous solution of a mixture of surfactants, glucanases and proteases (P3-Ultrasil 62, manufacturer: Henkel) having a pH of 9 to 9.5 (adjusted by means of a 0.15% aqueous solution of a mixture of surfactants and an alkaline component (P3-Ultrasil 91, manufacturer: Henkel)) at a temperature of 50 ° C and then rinsed with warm water (50 ° C). For chemical cleaning, the filter was treated for 30 minutes with a solution water at 1% of a mixture of surfactants and an acid component (P3-Ultrasil 75; manufacturer: Henkel) at 60 ° C and then rinsed with fresh water. After this, the filter was treated for 30 minutes with an aqueous solution containing 1% of a mixture of surfactants and an alkaline component (P3-Ultrasil 91, manufacturer: Henkel) and 1% of a mixture of surfactants and a donor. of oxygen (P3-Ultrasil 05, manufacturer: Henkel) at a temperature of 60 ° C and then rinsed with fresh water. Then, the filter was treated once again for 30 minutes with a 0.5% aqueous solution of a mixture of surfactants and an acid component (P3-Ultrasil 75, manufacturer: Henkel) and then rinsed with fresh water until the water of rinsing get the electrical conductivity of the new water. Then, the filtering behavior of this cleaned filter was tested again, under the conditions indicated above. The result is illustrated in Figure 3. Figure 3 shows that the filtering behavior has improved slightly, since the 200 g of the filtrate could be obtained already after about 600 seconds. The same clogged filter whose filtration behavior is illustrated in figure 2, was cleaned according to an embodiment of the method according to the invention, wherein the filter was treated for 20 minutes with a mixture of dimethyl sulfoxide (DMSO) -water (50% DMSO, 49% water, 1% KOH) at a temperature of 55 ° C. Then, the filter was rinsed with hot water (60 ° C) both in the direction of the filtration and in the opposite direction to it. Then the filter was washed until the rinse water was free of DMSO. The release of DMSO was tested chromatographically. With this filter cleaned according to the invention, the filtration behavior was tested again according to the above method. The result is illustrated in Figure 4. Figure 4 shows that 200 g of filtrate could be obtained already after about 250 seconds. It was possible to obtain similarly good results also with other aprotic polar solvents. This constitutes a significant improvement over the prior art (FIG. 3) . Thus, the method according to the invention allows a cleaning of a used membrane filter considerably better than was possible with cleaning methods of the prior art. With the cleaning method according to the invention, the duration of a membrane filter can be increased in this way.

Determination of the cleaning effectiveness The zeta potential of the membrane filters was determined by means of the EKA electrokinetic measuring system from Antón Paar GmbH, Austria. This measurement is based on the current potential method. An electrolyte flows through the filters, and the potential (current potential) that is produced by cutting off counterions is detected by means of electrodes, and the zeta potential is calculated from this measured amount (see below). QP The measurement cell by means of which the current potential and the zeta potential were determined, is illustrated schematically in FIG. 5. The reference number 1 designates the measurement cell in which the membrane filter 2 is held without warping in filter holder means 3, 4, made of Teflon. The filter holder means 3, 4 are the end pieces of two pistons 5 and 6, respectively, which are mounted for displacement in the cylindrical part 7 of the measuring cell 1. The end pieces 3, 4 of the pistons 5 and 6, respectively, have fine holes 10 and 11 for the fluid to filter, and press the perforated electrodes 8 and 9 against the membrane filter 2. The electrodes 8 and 9 are connected to the two electrical terminals 12 and 13 that extend inside the pistons 5 and 6, respectively, in such a way that you can measure the current potential generated when it flows to through the membrane 2. The electrodes are preferably silver or silver chloride electrodes which exhibit low polarization during current flow. The pistons 6 and 7 are mounted on the seals 14 and 15 respectively in such a way that on the one hand, they are displaceable and, on the other hand, they are not allow the leakage of no fluid from the measuring cell. The fluid to be filtered passes through the supply line 16 to the cylindrical part 7 of the measuring cell 1, flows through the fine holes 10 of the piston 6, through the electrode 8, generating an electric potential, and through of the membrane filter 2. The filtered fluid flows through the electrode 9, also generating a potential, passes through the fine holes 11 of the - piston and leaves the measuring cell through the discharge line 17. For To determine the zeta potential from the measured current potential or the current flow, further measurements (not shown) of the pressure difference in the measuring cell between the supply line 16 and the discharge line 17 are required. the conductivity of the fluid to be filtered and its viscosity. As is known, the zeta potential is calculated from these quantities measured in the following way: U LF V Potential zeta = "delta-p 0 where U is the current potential, delta-p denotes the pressure difference, LF the conductivity, V the viscosity, and Q ^ a dielectric constant. The change in the zeta potential of the membrane filter as the obstruction progresses is illustrated in Figure 6. This figure is a diagram in which the zeta potential in millivolts is plotted on the ordinate and the pH at which the zeta potential was determined. is plotted on the abscissa. The pH of the electrolyte solution (aqueous solution of KCl 0.001 N) was adjusted by means of 0.1 N HCl or 0.1 N NaOH. The specified pressure difference was 350 bar. The diagram was obtained by first determining, by means of the measurement cell described above, the zeta potentials of a new, ie unused, membrane filter made of polyamide (type NB, manufacturer: Pall Filtrationstechnik GmbH, D-6072 Dreieich 1, Germany) at various pH values. The results relating to the unused membrane filter are plotted as the "a" curve. It is evident that the unused filter has a zeta potential of approximately -18 mV at an alkaline pH, and that the zeta potential increases with decreasing pH values, and finally reaches zero at a pH of about 3. Curve "b" shows the dependence of the zeta potential on the pH of the previous filter under identical measurement conditions, as indicated previously, but after using it to filter beer and therefore, with partial obstruction. As is evident, the zeta potential has been raised slightly by partial obstruction, reaching a value of only about -15 mV at pH values of about 7. Curve "c" is plotted for the same membrane filter in the completely clogged state . It is evident that the zeta potential changes only slightly with the pH and even in the alkaline scale it does not decay below approximately -2 mV. To check the cleaning according to the invention, the zeta potential of the filter to be cleaned is determined, the cleaning being successful if the zeta potential of the cleaned membrane has changed as much as possible in the direction of the zeta potential of the unused membrane. It is clear to the skilled artisan that membrane filters whose zeta potentials change to a sufficiently large extent as a function of the degree of clogging, are particularly well suited for use in the method according to the invention. However, the skilled artisan can easily determine this by means of simple tests.

Claims (6)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for producing cold filtered beer, in which the beer is filtered through a membrane filter that is cleaned after filtration and used for a new filtration, characterized in that the membrane filter, for cleaning, is it comes in contact with an aprotic polar solvent and then it is washed.

2. A method according to claim 1, characterized in that dimethyl sulfoxide, dimethylformamide or tetrahydrofuran is used for cleaning.

3. - A method according to claim 2, characterized in that the cleaning is carried out in the presence of an alkali metal hydroxide if dimethyl sulfoxide is used.

4. - A method according to any of claims 1 to 3, characterized in that the solvent is present as a mixture with water.

5. A method according to claim 4, characterized in that the solvent is present in an amount between 30 and 100% by mass, based on the total mass of the mixture.

6. A method according to any of claims 1 to 5, characterized in that the cleaning is carried out until the zeta potential of the membrane filter no longer changes.