FR2796923A1 - Valve for package containing food or other product destined to be heated has seal of paraffin wax or similar which softens on heating - Google Patents

Abstract

The valve (5) covers an aperture (7) in the packaging (4) and contains a seal (11) of a solid or paste-like substance which is impermeable in its solid state to gases, liquids and micro-organisms, but softens when heated to allow gas to pass through and avoid excessive pressure inside the package.

Description

<B> <U> VALVE AND VALVE PACKAGING. The present invention relates to a valve for a package in which a product is subjected to a treatment causing degassing, said valve being disposed above or below at least one hole drilled in the package and cooperating with sealing means to allow degassing through said hole during the treatment and to prevent return of air at the end of treatment. It also relates to a packaging equipped with such a valve, applicable in very diverse fields such as cooking food, sterilization of single-use products in the medical field, packaging of pharmaceutical, medicinal, cosmetic preparations.

When it comes to cooking food, its realization in a valve package has a number of advantages, including preserving the color and taste of food. It has indeed been found that the degassing carried out during cooking, thanks to the valve, has the effect of maintaining the green chlorophyll with respect to cooking under vacuum which would have denatured. On the other hand, the taste is preserved because it is a cooking in the atmosphere. Finally, compared to cooking under vacuum, cooking in a valve package generates more limited amounts of exudates.

To carry out the cooking, the food is first placed in a package that is closed by a sealing cap, a crimped lid or any other suitable means. A valve is disposed above a degassing hole, pierced in said package. This valve must allow the evacuation of pressurized gases during cooking and must close the sealing of the packaging at the end of cooking, especially during the cooling of the packaging.

During the heat treatment that is cooking food, the packaging is subjected to an internal pressure resulting in particular degassing food, reactions of the various constituents contained in the package, the expansion of the head space, c that is to say, the space between the lid and the food and finally the pressure of the water vapor. The valve must therefore react taking into account the two main operating parameters that are pressure and temperature.

Many types of packaging valves for cooking have already been proposed. In the document FR 2 656 280, the valve is constituted by a tongue hinged on the edge of the package, folded towards the inside thereof after filling with food and before sealing the lid, said tongue having on its horizontal face a perforated seat in which is deposited a drop of composite resin becoming porous at a predetermined temperature; in addition, the seal is pierced at the precise location where the drop of composite resin is located. Although this is not explicitly described in this document, it is understood that during cooking the temperature is such that the resin is porous and allows the pressurized gases to escape from the package, while during cooling at the end of cooking, the temperature drop is such that the resin loses its porous character and closes the hole made in the seat of the rim.

In the document FR 2 698 082, the valve is formed solely by a hole in the rim of the package and by a layer of substance having a melting point between 65 and 150 C, interposed between the lid and the part rim around the hole. When cooking, the lid lifts under the effect of the internal pressure. Degassing can take place through the hole in the rim. At the end of cooking, during cooling, a vacuum is created inside the packaging which closes the lid on the rim. The layer interposed between the cap and the portion of the rim around the hole provides tight sealing of the cap on the rim, preventing outside air from entering. The substance, having a melting point between 65 and 150 ° C., is preferably a fusible glue, especially a food glue, such as a hot-melt glue based on terpene resin and / or vinyl polymer.

In the first document FR 2 656 280, it is the fuse composite resin, with a porous nature at a predetermined temperature, which acts as a non-return valve of the valve, by sealing the hole made in the seat of the flange.

In the document FR 2 698 082, it is the seal seal which acts as a check valve, the hot melt adhesive having the function of adhering said seal on the periphery of the hole in the rim of the package .

There is a third type of degassing valves for packaging but these packages are not used for cooking food. They are more particularly used for the vacuum packaging of coffee. Such a valve package makes it possible to bag, as soon as roasting, the ground coffee, thus avoiding any risk of oxidation. The valve, while preventing the entry of air, allows the coffee to gradually release the natural surplus of gas that occurs after roasting.

In this package, the valve comprises a flexible sheet which is fixed only by certain areas, preferably longitudinal, on an annular base, itself fixed, in particular by bonding or heat sealing, around a degassing hole pierced in the package . In addition, said valve comprises a sealing means which is a silicone oil located between the flexible sheet and the annular base. Upon release of gases after roasting, the flexible sheet is lifted under the effect of the internal pressure, which gives rise to an exhaust channel between the flexible sheet and the package in the area where said flexible sheet is not fixed on the ring base. At the end of degassing, the silicone oil is distributed between the sheet and the base and forms a seal preventing any entry of air into the package.

This third type of valve is not transferable in the state- valve packaging for cooking food. Indeed, in this case, the cooling of the packaging is generally at low temperatures, where the silicone oils lose their sealing property. In addition, in the case of wet foods having a liquid phase such as a sauce, there is a risk of contamination of the silicone oil of the valve by the liquid, which can change the properties of the silicone oil sealing and rendering the valve ineffective. Moreover, in the event of a decrease in ambient pressure, particularly with regard to a packaging intended for air transport, the valve that uses the silicone oil may open spontaneously because of this pressure decrease, with the risk of contamination by the liquid contained in the package leading to a leakage of the valve.

The goal set by the applicant is to propose a valve provided with a durable and effective sealing means, whether for cooking food or for other types of use.

It is a valve for a package in which a product is subjected to a treatment causing degassing, valve which is disposed above or below at least one hole drilled in the package and which cooperates with sealing means for allowing degassing through said hole during the treatment and preventing air return at the end of treatment.

Typically, according to the invention, the sealing means is a paraffin or a paraffinic component having a melting point, with solidification plateau, of less than about 70 ° C., the solidification being in the form of crystals.

Paraffins are mixtures of solid hydrocarbons belonging to the family of alkanes, whose melting point is between 48 and 70 ° C maximum. It is possible to obtain a paraffin having a melting point, accurate to 1 C.

In contrast to hot-melt type hot melt resins, or even in contrast to waxes, paraffin has a melting point which has a solidification plateau. In other words, the passage from the solid phase to the liquid phase and vice versa, for a given paraffin, occurs in a very low temperature zone of a few degrees.

This presents the undeniable advantage of obtaining for the valve of the invention a threshold in precise operation, at a temperature determined according to the choice of the paraffin or the component with paraffinic behavior. This can not be the case when using a hot melt resin which does not have a solidification bearing but a continuous variation of the viscosity as a function of temperature.

In addition, in the liquid state, the paraffin has a behavior, from the point of view of its fluidity, which is quite comparable to a silicone oil, so that it can be divided at the end of treatment, between the constituent elements of the valve.

Moreover, the crystalline macro-crystal nature of solid paraffin, which is explained by the high proportion of straight-chain hydrocarbons, forms, by the interlocking of the crystals with each other, a barrier which is difficult to pass through by water, fats and even gases when paraffin is in the solid state. Solidified paraffin between the constituent elements of the valve thus makes it possible to ensure perfect sealing thereof.

Preferably, the paraffin or paraffinic component has a melting point of 48 to 53 ° C, preferably 51 ° C.

This relatively low melting temperature has the advantage of being able to subject the valve package to a heat treatment at a relatively low temperature, for example when cooking food from 60 C, which does not is not the case of conventional valve packaging using hot-melt resins type hot melt, the resin remaining substantially solid at this temperature.

Of course, the fact of being able to implement the valve package according to the invention in the context of a heat treatment at relatively low temperature from 60 C does not prevent it is possible to use it at more high temperatures, including the order of 130 C. The user therefore has a much wider temperature range for the implementation of the same package.

It is another object of the invention to provide a valve package that is suitable for being used for cooking food and whose valve comprises a sealing means consisting of a paraffin or a component with behavior paraffinic as above.

The valve package, of the invention, comprising a sealing cap, and pierced with a degassing hole, is equipped with a valve which comprises a flexible sheet fixed only by certain zones, preferably longitudinal, on a base annular fixed around the degassing hole. It is therefore a valve according to the third aforementioned type which, through the use of paraffin or paraffinic component component as a sealing means, can be used for cooking food.

In a preferred embodiment, the valve, specially designed for the above packaging, is a self-adhesive valve, the base of the annular base having a pressure-sensitive adhesive; in this case, preferably, a solid paraffin deposit is formed on the inner face of the flexible sheet.

The present invention will be better understood on reading the description of an exemplary embodiment of a valve packaging, for cooking food, comprising, as sealing means, a paraffin, illustrated by the accompanying drawing in which - FIG. 1 is a schematic top view of the exemplary embodiment of a valve package whose sealing is ensured by paraffin; - FIG. 2 is a partial schematic representation, in perspective, of the packaging of Figure 1 along the axis II-II, and - Figure 3 is a schematic sectional representation of the package of Figure 1 along the axis 111-11I.

The packaging 1, intended for cooking food 3, consists of a tray 2, a sealing cap 4 and a degassing valve 5.

The lid 4 covers the open portion of the tray 2, once the food 3 have been placed there and is fixed on the peripheral rim 6 of said tray 2 by heat sealing. This technique is well known. It implements peelable polypropylene heat-sealing films, for example films marketed under the name steril'up by the company ALSACIENNE D'ALUMINUM or under the name bialon S 65 VFP by the company WIPAK or under the reference E63598 by the company SOPLARIL. It may also be pre-cut lids using for example aluminum.

The cover 4 covers the upper part of the peripheral rim 6 of the tray 2, with an extension forming an opening tab 17. It suffices for the user to grip this tongue 17 and to exert traction to achieve the opening of the tray 2 by peeling the lid 4.

In the central zone of the cap 4 is drilled a degassing hole 7, which may have a diameter of the order of 1 mm. This degassing hole 7 is covered with a valve 5.

In the example illustrated in Figure 2, this valve has a structure according to the teaching of EP 0 023 703. It consists of a flexible sheet 8 - for example polyethylene or polypropylene - which is fixed by gluing , on an annular base 9, itself fixed by gluing on the cover 4, so that the recessed central portion 10 of the base 9 is in line with the degassing hole 7. The flexible sheet 8 is not completely fixed on the annular base 9, but simply according to the two longitudinal edges 9a, 9b of it. In addition, in the central recess 10 of the base 9, forming the inner chamber of the valve 5, a certain amount of solid paraffin 11 has been deposited prior to the introduction of the valve 5 on the cover 4.

It is preferably a low-melting food paraffin, for example paraffin called 50/52 by TOTAL, which has a melting point of 51 C with a tolerance of 1 C.

Starting from a valve presenting as a self-adhesive label, as described in document EP 0 023 703, the solid paraffin deposit 11 is made under the following conditions. The paraffin is melted beforehand in a forced air oven at 100 ° C. A rod, for example of wood, having a diameter of 7.5 mm and having a flat end is dipped in liquid paraffin, moved over the valve 5, so that a drop of liquid paraffin is deposited hot on the inner face of the flexible sheet 8 to the right of the central recess 10 of the annular base 9. This operation can be performed continuously and automatically using a paraffin melter and a specific metering device, unwinding upside down, a ribbon supporting the valves 5, the base of the base 9 is covered with an adhesive 12 sensitive to mechanical pressure.

Each valve 5, already provided with paraffin, is deposited on the lid 4 as an adhesive label.

The packaging 1 thus formed is subjected to a heat treatment at a temperature of between 60 ° C. and 130 ° C. In the present text, reference is made in the usual way to a cooking treatment; it may be a cooking proper or any other type of heat treatment of the type sterilization or pasteurization.

The heat transfer fluid is preferably steam but it can also be pulsed air or moist air, or even hot water. - The cooking can be done discontinuously, for example in a rack oven with racks, an autoclave or a tank filled with hot water. It can also be done continuously, for example by means of a linear conveyor or a conveyor belt passing through a chamber regulated in temperature.

During the heat treatment, the package 1 is subjected to an internal pressure which is the result of four partial pressures, namely the water vapor pressure, which is a direct function of the temperature, the pressure resulting from the expansion of the head space 13, that is to say the space between the inner face 4a_ of the lid 4 and the level 3a_ food 3, the pressure of degassing food and finally the pressure resulting from the reactions different constituents between them under the effect of heat.

During the heat treatment, the paraffin 11 melts instantly when its temperature reaches its melting point, for example 51 C. In the molten state, the paraffin has a consistency and fluidity that is close to that of a silicone oil. Under the effect of the pressure in the head space 13, and therefore in the central recess 10 of the annular base 9, the flexible sheet 8 deforms and this deformation causes the formation of an exhaust channel according to the zones 14 not fixed between the sheet 8 and the base 9. This is the degassing phase, the latter for as long as the internal pressure of the package 1 is sufficient to cause the deformation of the flexible sheet 8. This pressure can be of the order of 10 mbar.

During degassing, paraffin 11 in the liquid state is distributed between the flexible sheet 8 and the annular base 9, in particular along the longitudinal edges 9a, 9b thereof.

At the end of the heat treatment, especially when opening the cooking door, when this treatment is performed in such an oven, there is a rapid drop in temperature which causes almost instantaneous depression within the oven. Packing 1, called vacuum also draw vacuum. This vacuum draw is a function of the temperature reached by the food 3 at heart. If for example the core temperature is 95 C, it is considered that there is in this case a steam saturation in the head space 13. The vacuum drawing obtained by brutal condensation of this steam corresponds almost to a vacuum total.

The depression in the head space 13 causes a suction effect through the hole 7, which has the effect of pressing the flexible sheet 8 against the base 9. The paraffin 11 which, in the liquid state, has been distributed between the sheet 8 and the base 9 solidifies as soon as the temperature reaches its melting point, in this case 51 C in the case of paraffin 50/52 from the company TOTAL.

Paraffin solidifies in the form of macro-crystals whose interlocking forms a barrier to gases. The solidified paraffin, distributed between the flexible sheet 8 and the base 9 thus constitutes a perfectly effective seal for the valve 5 and durable over time.

Because the paraffin used as sealing means of the valve 5 has a very precise melting point, the operating threshold, in temperature, of said valve 5 is constant both opening and closing. It is also possible to work at a relatively low temperature, for example from 60 C, preferably in the vapor phase, to be able to take advantage of the latent heat of condensation of the steam ceded to the packaging.

In order to avoid excessive deformation of the package 1 and in particular of the lid 4, it is necessary to limit the height h of the head space 13 in a range of 5 to 10 mm.

It should be noted that if the paraffin is replaced by a hot-melt glue, there is a leakage at the valve 5 because during the cooling of the package 1 glue, still in a more or less melted state; is sucked by the hole 7 and does not distribute homogeneously between the film 8 and the annular base 9.

It should also be noted that the valve 5, using paraffin as sealing means, can be reused during the temperature rise of the product in an oven and this several times in succession, and without it being necessary to pre-drill the seal before reheating. In other words, this valve is completely reversible, when the heating is by heat input. As regards reheating by the action of microwaves, it is necessary that the sealing means comprises, in addition to paraffin or paraffinic component, a activator additive, reacting with microwaves.

The cooling of the package 1 can be carried out by ventilation of cold air or by supply of cryogenic gas, or in chilled water. There is no disadvantage that the cooling temperature is negative, since even at temperatures of this order paraffin does not lose its sealing properties.

The present invention is not limited to the embodiment which has just been described by way of non-exhaustive example. In particular, if paraffin is the preferred sealing means of the invention, it would be possible to substitute a component having a paraffinic behavior as described above with a relatively low melting point, with solidification stage and a solidification which takes the form of macro-crystals. In addition, the valve of the invention is not limited to its use in a packaging for cooking food. It can be used in packages containing pharmaceutical, medicinal or cosmetic preparations and in particular in a packaging where the sterilization of disposable products in the medical field will be carried out during the treatment causing degassing.

Finally, the use of paraffin or a component with paraffinic behavior as effective and durable sealing means is not limited to the type of valve which has been described in the above example; it can be implemented in any type of valve requiring a sealing means. Similarly, it can be any type of packaging, including a flexible plastic bag.

Claims (7)

1. Valve for a package in which a product is subjected to a treatment causing degassing, said valve being disposed above or below at least one hole drilled in the package and cooperating with a sealing means for allow degassing by said hole during the treatment and preventing air return at the end of treatment, characterized in that the sealing means is a paraffin <B> (11) </ B> or a component with paraffinic behavior having a melting point, with solidification plateau, of less than approximately 70 ° C., the solidification being in the form of macro-crystals. 2. Valve according to claim 1 characterized in that the paraffin or paraffinic component has a melting point between 48 and 53 C, preferably 51 C. 3. Valve according to one of claims 1 or 2 for cooking food at a temperature from 60 C. 4. Valve according to one of claims 1 or 2 for the sterilization of disposable products in the medical field. 5. Packaging for cooking food, which packaging comprising a sealing cap, is pierced with a degassing hole and is equipped with a valve provided with a sealing means, according to one of claims 1 to 3, characterized in that said valve (5) comprises a flexible sheet fixed only by certain zones, preferably longitudinal (9a, 9b), on an annular base (9) fixed around the degassing hole. 6. Packaging according to claim 5 characterized in that the hole (7) of the order of 1 mm is pierced in the lid (4). 7. Packaging according to one of claims 5 or 6 characterized in that the valve is a self-adhesive valve, the base of the annular base comprising an adhesive (12) sensitive to mechanical pressure and in that a paraffin deposit solid is made on the inner face of the flexible sheet (8).