DK179029B1

DK179029B1 - A method of producing cheese in a container

Info

Publication number: DK179029B1
Application number: DKPA201670068A
Authority: DK
Inventors: Henrik Sahlberg
Original assignee: Primoreels As
Priority date: 2016-02-08
Filing date: 2016-02-08
Publication date: 2017-09-04
Also published as: WO2017137049A1; DK201670068A1

Abstract

The present invention relates to a method for producing cheese in a container as well as a container for use in such a method. The method relates to producing acidified cheeses from milk by use of ultra filtration. In the method of the invention, retentate containing rennet and culture are filled into the container and is left to coagulate in the container. After coagulation, a membrane is placed on the coagulated cheese, and salt is dosed on top of the membrane, whereupon the container is sealed. According to the invention, the membrane is delayed penetration to liquid to ensure that no liquid will pass through the membrane before acidification. This is advantageous, in that liquid passing through the membrane will create brine when dissolving the salt on top of the membrane; this brine may pass back into the cheese curd due to osmosis, which will stop the acidification process. This problem is overcome by the method of the invention.

Description

A method of producing cheese in a container FIELD OF THE INVENTION

The present invention relates to a method for producing cheese. The method of the invention is particularly suited for use in the production of cheeses produced from milk by ultra filtration or by recombination in which production the cheese is contained in a brine produced as a result of mixing liquid separated from the concentrate or mix with e.g. salt.

BACKGROUND OF THE INVENTION

Cheeses produced from milk by use of ultra filtration or recombination are becoming very popular. The types of cheeses produced by this method can be divided into two main groups: un-acidified cheeses and acidified cheeses.

The latter are produced by adding cheese culture and rennet to the UF (ultra filtrated) retentate or recombinated mix. The culture will start an acidification process in the retentate or mix and within approx. 8-24 hours, the pH of the retentate or mix will drop from approximately 6.6 to approximately 4.6.

The acidified cheeses usually contain salt, frequently approximately 3.5% of the weight. The salt can not be mixed into the retentate or mix before acidification as it would prevent the culture from developing and thus stop the acidification.

The first plants for filling UF retentate or recombined cheese in retail containers came on the market in the late 1990s. They are all working according to the following principle: • Retentate mix containing rennet and culture are filled into the retail container; • The mixture is left to coagulate in the container, which take approx. 20 min; • On top of the newly coagulated cheese curd and in the container, is placed a parchment membrane and dry salt is dosed on top of the membrane, whereupon the container is sealed.

The reason for placing a membrane on top of the freshly coagulated curd is to keep the salt separated from the cheese curd until acidification of the curd has taken place - it means until the pH value in the curd has dropped to approx. 4.6.

The parchment membranes, which so far have been used in all cheese plants will allow permeate from the freshly coagulated cheese curd to penetrate the membrane and reach the salt, creating a quantity of saturated brine, which in turn will seep down into the still not fully acidified curd below the membrane along the walls of the container and inactivate the culture there. This method results in cheeses with different pH values in the centre and in the periphery of the cheese.

In order to overcome this problem many factories are turning the containers upside down after sealing. The cheese curd will then during the acidification process be hanging above the membranes effectively separated from the salt until acidification has taken place and the syneresis will release some permeate. The cheese will drop down on the membrane when the syneresis sets in. By this method, the permeate will dissolve the dry salt but in order that the brine created should be able to salt the cheese it is necessary to turn the containers back again. This process of turning the containers twice is time and space consuming and undesirable in a modern processing line.

Hence, a more efficient method for making cheese would be advantageous. Moreover, it would be advantageous if the cheese produced would be of homogeneous quality.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an alternative to the prior art.

In particular, it may be seen as an object of the present invention to provide a method of producing cheese that requires fewer working steps than the methods of the prior art. Moreover, it may be seen as an object of the present invention to provide a method of producing cheese with a homogeneous quality.

SUMMARY OF THE INVENTION

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a method of producing cheese in a container, which method comprising the steps of: - filling a coagulatable liquid substance into an open ended container; - leaving the coagulatable liquid substance to coagulate; - arranging an delayed penetration membrane on top of the coagulated liquid substance; - dosing a solid substance on top of the delayed penetration membrane; and - liquid sealing the open ended container by a lid.

According to this invention an delayed penetration membrane (such as a PP membrane or the like) is used. By use of such a membrane the solid substance dosed on the membrane is prevented from drawing liquid, such as permeate, from the coagulated liquid substance through the membrane. The amount of liquid substance filled into the open ended container should be so that a free space above the coagulatable liquid substance is left, i.e. that the container is not filled to the top of the wall thereof.

Delayed penetration membrane as used herein is used to mean a membrane which is configured to delay liquid penetration though the membrane for a given time scale At, which may be provided for instance by selecting a membrane having characteristics diffusion coefficient "D", porosity "ε", constrictivity "δ" and/or tortuosity "T" so as to delay penetration, and/or applying a liquid soluble material to a permeable membrane which soluble during the time scale At. The liquid soluble material may be applied as a coating on the membrane and/or as a pore filing material to the membrane.

According to aspects of the invention the coagulatable liquid substance comprises ingredients for producing White cheese such as FETA cheese, and the coagulatable liquid substance may comprise retentate or mix containing rennet and cheese culture. Moreover, the solid substance may be a salt, preferably NaCI.

By using an delayed penetration membrane for producing white cheese, the salt dosed on the membrane is prevented from drawing water from the coagulated liquid substance, viz. the coagulated cheese curd, through the membrane, which means that creation of brine will be prevented on top of the membrane until syneresis takes place - i.e. until the curd is acidified. The use of this type of membrane has the potential to create cheeses with the same pH in all sections, and it eliminates the need for turning the cheeses after manufacture. Thus, the container may be sealed and left stationary, until the rennet and the cheese culture of the retentate or mix acidify. By applying the delayed penetration membrane on top of the coagulated curd, the dry salt dosed on top of the delayed penetration membrane, will remain on top of the delayed penetration membrane until the pH in all the coagulated curd has dropped to approximately 4.6 and syneresis sets in. This syneresis will release some permeate which will rise to the top of the membrane and mix with the salt on top of the delayed penetration membrane. The brine thus created will seep down under the membrane to the cheese curd. By using this type of membrane no turning of the container will be required to ensure a uniform mixture of the brine and the cheese curd. Moreover, the pH value of the cheese curd will substantially be uniform throughout the cheese.

According to an aspect of the invention, the delayed penetration membrane is shaped so as to fit snugly with the inner side of the wall section in a horizontal plane of the open ended container. Alternative, the extension of the delayed penetration membrane is smaller than the inner extension of a horizontal cross section of the wall section of the container, the extension of the wall section being measured at a distance h from the base section. Thus, there is a gap between the membrane and the wall section of the container. This facilitates that the liquid created by the acidification process may rise up above the membrane to dissolve the salt placed on top of the membrane. It moreover facilitates the brine thus created to seep back into the cheese curd by osmosis.

According to an aspect of the invention, the delayed penetration membrane is arranged to at least partly rest on the surface of the coagulated liquid substance inside the container.

According to another aspect of the invention, the delayed penetration membrane is made of a plastic material. Such plastic material could be PP (polypropylene), PS (polystyrene), HDPE (High-density polyethylene), LDPE (Low-density polyethylene), PET (polyethylene terephthalate) or by parchment coated by plastic or the like.

Further aspects and embodiments of the present invention will be set forward in the following.

It should be noted that throughout this document, the term "delayed penetration" as used in this document is meant to denote "delayed penetration to liquid".

BRIEF DESCRIPTION OF THE FIGURES

The method according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing present invention.

Figures la to lg disclose steps of a prior art method, wherein a container is turned twice;

Figures 2a to 2d show an alternative prior art method;

Figures 3a and 3b show a method of the invention;

Figure 4 is a flow-chart of a method according to the invention, and

Figure 5a and 5b is a preferred embodiment of a delayed penetration membrane.

DETAILED DESCRIPTION OF AN EMBODIMENT

The invention will be described in more details in the following by way of examples and the with reference to the schematic drawing. Throughout the figures, like reference numerals denote like elements.

Figures la to lg disclose steps of a prior art method, wherein a container is turned twice. Fig. la shows schematically a cross sectional view of a container assembly 1. The container assembly 1 has a base section 2 and a wall section 3 made integral with base section 2, e.g. the base section 2 and wall section 3 is moulded in one piece and form an open ended container. In Fig. la, the container assembly 1 is filled with retentate or mix 4 from a dispensing unit 8. The retentate or mix 4 is filled into the open ended container in an amount leaving free space above the retentate or mix amount in Fig. la.

The retentate or mix is e.g. ultra filtrated (UF) retentate or recombined mix with mixed-in cheese culture and rennet. The retentate or mix is left for some time, typically about 20 minutes, whereafter the retentate or mix is coagulated.

In Fig. lb, a membrane 6, typically of parchment, has been placed upon the coagulated retentate or mix. In Fig. lc, dry salt 5 has been dosed on top of the membran 6. Typically, the dry salt comprises NaCI.

In Fig. Id, a lid 7 has been sealed on top of the container 1.

In Fig. le, the container has been reversed or turned upside down in order to prevent the salt from extracting liquid from the retentate or mix through the parchment. It can be seen from Fig. le that the membrane 6 does not touch the surface of the retentate or mix in this turned round or reversed position of the container, which hinders the salt from extracting liquid or water from the retentate or mix.

When syneresis sets in at the end of the acidification to a pH at about 4.6, the cheese will drop due to seeping of permeate from the curd. This is shown in Fig.

If. Permeate will dissolve the salt 5 and create a brine 9.

In order to make the brine salt the cheese, the container is turned again, to an upright position shown in Fig. lg.

The method illustrated in figs, la to lg has the disadvantage of requiring the working steps of turning the container twice. Moreover, this turning of the container may require extra work space.

Figures 2a to 2d show an alternative prior art method. Fig. 2a has been preceded by steps corresponding to Figs, la to lc, so that Fig. 2a corresponds to Fig. Id. In Fig. 2a, however, the container 1 has not been reversed or turned upside down subsequent to dosing salt 5 on top of the membrane 6. Therefore, the salt 5 will draw water or permeate from the cheese curd 4 below the membrane, due to the parchment membrane 6 being permeable to water or liquid. In Fig. 2a, the drawing of permeate form the cheese curd is illustrated by arrows.

In Fig. 2b, the water has dissolved some of the salt 5 and has created a saturated brine 9. In Fig. 2c, the brine 9 is seeping down around the edges of the membrane 6 close to the wall section of the container 1. This is shown by the brine being shown as bending downwards into the cheese curd. The seeping of the brine 9 into the cheese curd will stop the action of the cheese culture and acidification is stopped prematurely. This results in a final product as shown in Fig. 2d, wherein the zone A comprises cheese curd with a too high solid content due to water extraction, the zones B comprise cheese curd with a too high pH value due to the cheese culture having been inactivated prematurely by the brine, and a zone C comprising cheese curd with a proper texture and pH value.

The invention is i.a. based upon the finding that in the method illustrated in Figs. 2a-2d, when a membrane is placed on a freshly coagulated curd, the salt dosed on top of the membrane will draw liquid, viz. water or permeate, out of the curd, which is below the dry salt, through the membrane. This water will dissolve some of the salt and the brine thus created will seep along the walls of the container into the cheese curd below, and the high salt concentration in that brine will prevent the proper acidification of the cheese curd along the walls of the container.

The result will be a cheese with soft layers along the container walls and a hard core. The hard core is partly due to proper acidification of the cheese and partly due to the increase in the total solid content caused by the drainage of water from the cheese curd caused by salt on top of the membrane. Such a product is not well accepted by the consumers and has a very short shelf life.

The method of the invention alleviates the above problems of the prior art.

Figures 3a and 3b show a method of the invention, in that Fig. 3a and 3b schematically show a cross sectional view of a container assembly 1 in two different time instances of the method of the invention.

In Figs. 3a and 3b is seen a cross sectional view of a container 10. The container assembly 10 has a base section 12 and a wall section 13 made integral with base section 12, e.g. the base section 12 and wall section 13 is moulded in one piece and form an open ended container. The container 10 in Figs. 3a and 3b is shown containing retentate 14 and salt (NaCI) 15. The retentate 14 containing rennet and cheese culture has been filled into the open ended container in an amount leaving free space above the retentate (indicated by h) in Fig. 3a.

Within the container 10 and above the retentate 14 an delayed penetration membrane 16 is arranged. This delayed penetration membrane 16 is arranged on the surface of the retentate 14, typically right after the retentate 14 has coagulated. The delayed penetration membrane 16 is made of an delayed penetration material and rest on the surface of the coagulated retentate 14. On the surface of the delayed penetration membrane 16 salt (NaCI) 15 is dosed an due to the delayed penetration nature of the delayed penetration membrane 16 no liquid substances will be transported from the retentate 14 through the delayed penetration membrane 16 to the salt 15 and no brine may be created in this manner.

The delayed penetration membrane 16 is preferably shaped as a disc which fit snugly to the inner surface of the wall section 13 when the delayed penetration membrane 16 rest on the surface of the coagulated retentate. The term "fit snugly" is used to designate the situation where the outer rim of the delayed penetration membrane 16 abuts the inner surface of the wall section 13 without this abutment introducing wiggles in the delayed penetration membrane 16. Such a snug fit may prevent salt from getting in contact with the coagulated retentate or mix.

However, the delayed penetration membrane 16 may be shaped as a disk having a smaller size than a horizontal cross section, at height h, of the container assembly 10 whereby the delayed penetration membrane will not fully cover the retentate 14. The wall section 13 is typically shaped as a truncated cone (as shown in Figs. 3a and 3b) and in this case the snug fit or the smaller diameter is measured at the height h of the retentate 14 within the container assembly 10.

The delayed penetration membrane 16 could typically made of plastic such as PP, PS, HDPE, LDPE, PET or parchment coated with plastic or the like. The thickness of the membrane is typically in the order of 13-80 pm. The container used with the method of the invention is preferably capable of holding 25-1000 ml, and typically it has a height of 20-150 mm.

After dosing of salt 15 on top of the delayed penetration membrane, the container assembly 10 has been sealed by a lid 17 to the wall section 13, e.g. along a flange 18 provided on the upper end of the wall section 13 thereby constituting a fluid tight container assembly 10 containing the retentate 14 and salt 15. The container can alternatively be sealed by a water-tight snap on lid.

Fig. 3b shows the container at a later instance of time compared to Fig. 3a. Due to the application of an delayed penetration membrane, e.g. of a plastic material, on top of the coagulated curd, the dry salt 15 dosed on top of the membrane (see Fig. 3a) has remained on top of the membrane until the pH value in all the cheese curd below the membrane has dropped to approx. 4.6; this is a pH value where syneresis sets in. The set in of syneresis facilitates releasing some permeate which rises to the top of the membrane 16 and dissolves the salt 15 deposited on the membrane 16, thus creating brine 19. This brine 19 will seep down under the membrane 16 and salt the cheese. This is shown in Fig. 3b by the curved lines 20. Thus, by using this type of membrane no turning of the container 10 is required in order to obtain a correctly acidified cheese with proper salting. The solid content of the cheese 14' as well as the pH value will be the same in all the cheese 14'.

Figure 4 is a flow-chart of a method 100 according to the invention. The method starts in step 110 and continues to step 120, wherein retentate or mix containing rennet and culture are filled into an open ended container, e.g. the container 10 of Figs. 3a and 3b. Subsequently, in step 130, the retentate is left to coagulate. This coagulated retentate is denoted cheese curd. This takes approximately 20 minutes. In the next step, step 140, an delayed penetration membrane is placed on top of the coagulated retentate or mix or curd.

Subsequently, in step 150, dry salt, preferably NaCI, is dosed on top of the delayed penetration membrane. Thereafter, in step 160, the open ended container is sealed by a lid. Finally, in step 170, the container 10 is left for some time so as to let the retentate or mix or cheese curd react, viz. acidify, until the pH value of the cheese curd has reached approximately pH 4.6. This process takes approximately 8-24 hours. After acidification of the cheese curd, syneresis takes place. When the cheese curd has acidified, permeate comprising water with lactose and ashes will be created. Since this permeate has a lower density than the cheese curd, it will move up along the wall sections 13 (see Fig. 3a), past the edge of the membrane 16, and above the membrane to get into contact with the salt 15 (see Fig 3a) and dissolve the dry salt deposited on top of the membrane. The brine created in this way will subsequently drop below the membrane and effect salting of the cheese curd due to osmosis. Throughout the processes of acidification of the cheese curd and the subsequent salting, the container assembly may be left untouched. There is thus no step of turning the container in order to prevent premature mixture of permeate and salt and the resulting cheese with lower quality as explained above. The process 100 ends in step 180.

The open ended container may be a retail container. Preferably, a retail container is sealed by a lid after all ingredients are placed in the open ended container and only opened upon consuming. The term "retail container" is preferably used to designate a container in which a dairy product, preferably cheese, is produced and presented to a consumer. When the open ended container is a retail container, the method 100 may be carried out using the retail container which is sold to the the consumer. Thus, no step for opening the container and moving the cheese to any other container is needed. Thereby, the invention provides a simple method comprising fewer steps than prior art methods. The method of the invention is based on the realization that the membrane should be delayed penetration in order to prevent liquid passing through the membrane. When an delayed penetration membrane is used, the cheese curd will acidify to a pH value of 4.6 and upon acidification throughout the cheese curd, permeate is created. This permeate will pass in between the membrane and the wall sections of the container due to the permeate having lower density than the cheese curd. The brine created by mixture of the permeate and the salt will pass downwards (in the downwards direction as seen in Figs. 3a and 3b) due to osmosis and create a substantially uniform salting of the cheese curd.

In short, the present invention relates to a method for producing cheese in a container as well as a container for use in such a method. The method relates to producing acidified cheeses from milk by use of ultra filtration. In the method of the invention, retentate containing rennet and culture are filled into the container and is left to coagulate in the container. After coagulation, a membrane is placed on the coagulated cheese, and salt is dosed on top of the membrane, whereupon the container is sealed. According to the invention, the membrane is delayed penetration to liquid to ensure that no liquid will pass through the membrane. This is advantageous, in that liquid passing through the membrane before acidification has taken place will create brine when dissolving the salt on top of the membrane; this brine may pass back into the cheese curd due to osmosis, which will stop the acidification process. This problem is overcome by the method of the invention.

Reference is made to fig. 5a and 5b illustrating schematically a preferred embodiment of delayed penetration membrane 16. The delayed penetration membrane 16 comprises permeable membrane 16a, illustrated by channel 21 through which the liquid may penetrate the permeable membrane 16a, and a coating 16b on the lower side of the permeable membrane 16a. It is noted that the orientation "lower side" refers to the side of the membrane 16 facing the coagulated liquid substance 14, when the membrane 16 is arranged in a container.

The coating is made from a material being soluble in the permeate coming from the coagulated liquid substance 14. Example on such materials are gelatine or the like.

In an alternative embodiment of the invention, the delayed penetration membrane 16 is non-coated and is made from a material allowing penetration but at a slow rate, that take at least 4 hours, such as at least 8 hours or more, for the permeate to penetrate the membrane and get into contact with the salt dosed on top of the membrane 16. A given configuration of the delayed penetration membrane 16 is typically provided through experiments according to which for instance the thickness of the sheet 16a and the thickness of the coating 16b is determined in accordance with a desire as to the time scale for which no penetration takes place. Similarly, the characteristic of a non-coated permeable membrane 16 may be provided by experiments.

Figure 5b illustrates the delayed penetration membrane 16 after a period of at least 4 hours, such as at least 8 hours or more, wherein the permeate has soluble the water soluble coating 16b and the permeate may now penetrate the permeable membrane 16a.

The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. Fremgangsmåde til fremstilling af ost i en beholder, hvilken fremgangsmåde omfatter trinnene at: - fylde en koagulerbar flydende substans (14) i en åbenendet beholder (10), hvilken beholder (10) omfatter en basissektion (12) og en vægsektion (13) forbundet til eller integreret med basissektionen (12); - lade den koagulerbare flydende substans (14) koagulere; - anbringe en forsinket gennemtrængelig membran (16) (engelsk term: delayed penetration membrane) på toppen af den koagulerede flydende substans (14); - dosere en fast substans (15) på toppen af den forsinket gennemtrængelig membran; og - forsegle væsketæt den åbenendede beholder med et låg (17).A method of making cheese in a container, comprising the steps of: - filling a coagulable liquid substance (14) into an opening container (10), said container (10) comprising a base section (12) and a wall section (13) ) connected to or integrated with the base section (12); - coagulating the coagulable liquid substance (14); applying a delayed permeable membrane (16) (English term: delayed penetration membrane) to the top of the coagulated liquid substance (14); dosing a solid (15) on top of the delayed permeable membrane; and - sealing the liquid container tightly with a lid (17).

2. Fremgangsmåde ifølge krav 1, hvor den forsinket gennemtrængelig membran er konfigureret til udsætte gennemtrængning af væske i mindst 4 timer, såsom mindst 8 timer, fortrinsvis mindst 10 timer, fortrinsvis mindst 12 timer såsom mindst 20 timer, eller derover.The method of claim 1, wherein the delayed permeable membrane is configured to expose liquid penetration for at least 4 hours, such as at least 8 hours, preferably at least 10 hours, preferably at least 12 hours, such as at least 20 hours, or more.

3. Fremgangsmåde ifølge krav 1 eller 2, hvor den forsinket gennemtrængelig membran omfatter en coatet gennemtrængelig membran (16a), coatingen (16b) er fremstillet af vandopløseligt materiale såsom gelatine.The method of claim 1 or 2, wherein the delayed permeable membrane comprises a coated permeable membrane (16a), the coating (16b) being made of water-soluble material such as gelatin.

4. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor den forsinket gennemtrængelig membran er fremstillet af pergament coatet med plast eller lignende.A method according to any one of the preceding claims, wherein the delayed permeable membrane is made of parchment coated with plastic or the like.

5. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor den koagulerbare flydende substans omfatter bestanddele til fremstilling af hvid ost såsom FETA-ost.A process according to any one of the preceding claims, wherein the coagulable liquid substance comprises ingredients for making white cheese such as FETA cheese.

6. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor den koagulerbare flydende substans omfatter retentat eller rekombineret blanding indeholdende osteløbe og ostekultur.A method according to any one of the preceding claims, wherein the coagulable liquid substance comprises retentate or recombined mixture containing cheese run and cheese culture.

7. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor den faste substans er salt, fortrinsvis NaCI.A process according to any one of the preceding claims, wherein the solid is salt, preferably NaCl.

8. Fremgangsmåde ifølge et hvilket som helst af kravene 1 til 7, den forsinket gennemtrængelig membran (16) er formet så at den passer stramt med indersiden af vægsektionen (13) i et vandret plan af den åbenendede beholder (10).Method according to any one of claims 1 to 7, the delayed pervious membrane (16) is shaped to fit tightly with the inside of the wall section (13) in a horizontal plane of the open container (10).

9. Fremgangsmåde ifølge et hvilket som helst af kravene 1 til 7, hvor forlængelsen af den forsinket gennemtrængelig membran (16) er mindre end den indre forlængelse af et vandret tværsnit af vægsektionen (13) af beholderen (10), forlængelsen af vægsektionen (13) er målt ved en afstand h fra basissektionen (12).The method of any one of claims 1 to 7, wherein the extension of the delayed pervious membrane (16) is less than the internal extension of a horizontal cross-section of the wall section (13) of the container (10), the extension of the wall section (13). ) is measured at a distance h from the base section (12).

10. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor den forsinket gennemtrængelig membran er anbragt til mindst delvist at hvile på overfladen af den koagulerede flydende substans (14) indvendigt i beholderen (10).A method according to any one of the preceding claims, wherein the delayed permeable membrane is arranged to rest at least partially on the surface of the coagulated liquid substance (14) inside the container (10).

11. Fremgangsmåde ifølge et hvilket som helst af de foregående krav, hvor den forsinket gennemtrængelig membran (16) er fremstillet af eller bestående af plastmateriale.A method according to any one of the preceding claims, wherein the delayed permeable membrane (16) is made of or consisting of plastic material.

12. Fremgangsmåde ifølge krav 11, hvor den forsinket gennemtrængelig membran (16) er pergament coatet med plast eller lignende.The method of claim 11, wherein the delayed permeable membrane (16) is parchment coated with plastic or the like.

13. En forsinket gennemtrængelig membran tilpasset til at blive anvendt i en fremgangsmåde ifølge et hvilket som helst af kravene 1 til 11.A delayed permeable membrane adapted to be used in a method according to any one of claims 1 to 11.