Method for manufacturing a blank for packaging a food portion

Abstract

The invention relates to a method for manufacturing a blank formed of a complex (2) comprising an exterior layer (3) based on cellulose fibers and an interior sealing substrate (4) comprising at least one outer layer (4a) associated with the exterior layer (3), said method providing for forming at least one tear line (33) by ablation of material by means of a laser beam at a wavelength of between 9.6 and 10.6 μm, at least the outer layer (4a) being formed of a material of which the absorption of said laser beam is less than that of the exterior layer (3) and / or of which the reflectivity to said laser beam is greater than 50%, said laser beam being configured to induce at least partial ablation of only the exterior layer (3).

Description

[0001] DESCRIPTION

[0002] Title: Process for manufacturing a blank for packaging a food portion

[0003] The invention relates to a method for manufacturing a blank for packaging a food portion, as well as a blank obtained by implementing such a method.

[0004] It applies in particular to the packaging of individual food portions of fresh dairy products, such as, for example, fresh and / or processed cheese, which are packaged in an envelope formed by folding a blank.

[0005] To obtain an envelope, in particular of quadrilateral or prismatic geometry with a triangular base, blanks are known on which fold lines are formed to delimit different panels forming, after folding, a wall of the envelope.

[0006] The blank comprises at least one sealing layer having barrier properties to oxygen and / or water vapor, and the closure of the packaging must preserve this sealing in order to guarantee the preservation of the packaged portion.

[0007] To achieve this seal while benefiting from an ecologically designed packaging, in particular by facilitating its recycling after consumption of the food portion, the blank is formed from a complex comprising an outer layer based on cellulose fibers which is combined with an inner substrate mainly ensuring the sealing function, in particular against oxygen and / or water vapor.

[0008] In relation to such a blank design, there arises the problem of the antagonism between the ease of opening the packaging to be able to consume the portion, in particular by young children and / or for soft portions, and the aforementioned sealing constraints which require a robust blank and closure. To overcome this problem, document WO-2023 / 148163 provides for the formation of at least one tear line arranged so that a manual pull induces a tear of said blank with a view to opening it.

[0009] In particular, a tear line can be formed by laser ablation over approximately 4 / 5 of the total thickness of the outer layer, which allows a good compromise between preserving the tightness of the package and the ease of its opening by tearing along said lines.

[0010] To do this, the laser beam can be configured to be absorbed by the outer layer of cellulose fibers so that the absorbed energy is transformed into heat and changes its state, melting or vaporizing it to a greater or lesser depth.

[0011] However, in relation to the costs and rates imposed by the food industry, which can be in the order of 1,000 blanks per minute, simply controlling the parameters of an industrial laser does not guarantee the ablation depth, and risks damaging the sealing substrate and therefore compromising the proper preservation of the packaged portion.

[0012] The invention aims to improve the prior art by proposing in particular a method for manufacturing a blank comprising a layer based on cellulose fibers in which at least one tear line is formed by laser ablation, said method making it possible to obtain a good compromise between the ablation depth necessary to facilitate opening and the preservation of the functional sealing substrate.

[0013] To this end, according to a first aspect, the invention proposes a method of manufacturing a blank for packaging a food portion, said blank being formed from a complex comprising an outer layer based on cellulose fibers and an inner sealing substrate comprising at least one outer layer associated with the outer layer, said method providing for:

[0014] - forming fold lines on said blank to allow it to be shaped into an envelope in which said portion can be packaged before closing said envelope;

[0015] - forming at least one tear line arranged so that manual pulling induces a tear in said blank with a view to opening it; the tear line being formed by ablation of material by means of a laser beam at a wavelength of between 9.6 and 10.6 pm, said method providing that at least the outer layer of the sealing substrate is formed of a material whose absorption to said laser beam is lower than that of the outer layer and / or whose reflectivity to said laser beam is greater than 50%, said laser beam being configured to induce at least partial ablation of only the outer layer.

[0016] According to a second aspect, the invention provides a blank for packaging a food portion, said blank being formed from a complex comprising an outer layer based on cellulose fibers and an inner sealing substrate comprising at least one outer layer associated with the outer layer, said outer layer being formed from a material whose absorption to a laser beam of a wavelength between 9.6 and 10.6 pm is lower than the absorption of the outer layer and / or whose reflectivity to said laser beam is greater than 50%, said blank being manufactured according to such a method to comprise:

[0017] - folding lines allowing its conformation into an envelope in which said portion can be packaged before closing said envelope;

[0018] - at least one tear line arranged so that manual pulling induces a tear in said blank with a view to opening it, said tear line being formed by at least partial removal of only the outer layer.

[0019] Other features and advantages of the invention will appear in the following description, given with reference to the appended figures, in which: [Fig.1] schematically represents in front view a blank according to one embodiment before its folding;

[0020] [Fig.2] represents in perspective the blank of figure 1 during its folding to form a package;

[0021] [Fig.3] represents, in perspective view from above, the opening of the packaging of figure 2;

[0022] [Fig.4] schematically represents in partial view a complex for forming a blank according to an embodiment of the invention, said complex having several pre-cutting lines of different depths.

[0023] In relation to these figures, a method of manufacturing a blank for packaging a food portion 1 is described below, as well as a blank obtained by implementing such a method.

[0024] The flan is particularly suitable for packaging an individual portion 1 of fresh dairy product, for example fresh and / or processed cheese.

[0025] The blank is formed from a complex 2 which has an outer layer 3 based on cellulose fibers, as well as an inner sealing substrate 4 comprising at least one outer layer 4a associated with the outer layer 3.

[0026] The outer layer 3 can be made from cellulose fibers from wood and shaped by the paper industry to form a layer of paper or cardboard, or be in the form of a non-woven fabric.

[0027] Such an arrangement allows for environmentally friendly packaging design. In particular, the outer layer 3 can be made from recycled cellulose fibers.

[0028] According to an exemplary embodiment, the outer layer 2b has a surface mass of between 30 g / m 2 and 150 g / m 2 , in particular between 50 g / m 2 and 110 g / m 2 , and more particularly of the order of 80 g / m 2 . Advantageously, the complex 2 comprises between 60% and 90% by weight of cellulose fibers. For this purpose, the outer layer 3 may have a thickness of the order of 60 μm, and the inner substrate 4 a thickness of between 4 μm and 20 μm.

[0029] In particular, the inner substrate 4 has oxygen and / or water vapor sealing properties which are sufficient to guarantee the preservation of the packaged portion 1.

[0030] To improve the overall properties of the packaging, the complex 2 may comprise at least one additional layer, for example in the form of a film and / or a varnish, having suitable properties.

[0031] In particular, as shown in Figure 4, the outer face of the outer layer 3 can be coated with a first additional layer 5 of varnish with anti-condensation properties, the outer face of which can itself be coated with a second additional layer 6 of permanent heat-sealable varnish.

[0032] The complex 2 may have decorations and / or markings, for example patterns and / or inscriptions of an aesthetic and / or commercial nature linked to the food portion 1. These elements may be formed by printing and / or embossing directly on the outer layer 3 of cellulose fibers.

[0033] According to one embodiment, the external layer 4a of the substrate 4 has properties of sealing against oxygen and / or water vapor.

[0034] As a possibly complementary variant, the substrate 4 comprises at least one internal layer 4c associated with the external layer 4a opposite the cellulosic external layer 3, said internal layer having properties of impermeability to oxygen and / or water vapor. In particular, the external layer 4a may have barrier properties essentially to oxygen or water vapor, the internal layer 4c having complementary barrier properties to guarantee impermeability.

[0035] In relation to Figure 4, the sealing substrate 4 comprises:

[0036] - an external layer 4a based on polyethylene which has sealing properties essentially against water vapour;

[0037] - an internal layer 4c based on ethylene-vinyl alcohol (EVOH), which has sealing properties mainly against oxygen;

[0038] - an opposite layer 4b associated with the internal layer 4c opposite the external layer 4c, made from polyethylene to protect said internal layer.

[0039] Furthermore, to allow the formation of the packaging and its closure after conditioning of the food portion 1, the sealing substrate 4 has a sealing layer 4d arranged opposite the outer cellulosic layer 3, in particular on the inner face of the layer 4b.

[0040] Advantageously, the sealing layer 4d is made of a food-grade material, so that it can be brought into contact with the food portion 1 during the formation of the packaging. To do this, the sealing layer 4d may be based on a peelable and / or heat-sealable varnish, for example based on polylactic acid (PLA).

[0041] The manufacture of a flan formed from a complex 2 as described above and the packaging of a food portion 1 in said flan are now described.

[0042] The manufacturing method firstly provides for forming on the blank fold lines 7 arranged to allow the shaping of said blank into an envelope 8, in which the food portion 1 can be packaged before closing said envelope to form a package. The fold lines can be configured to obtain an envelope, in particular of quadrilateral or prismatic geometry with a triangular base, by delimiting different panels forming after folding a wall of said envelope.

[0043] Advantageously, these fold lines 7 are formed by creasing the outer layer 3 of cellulose fibers, which makes it easier to fold the blank while maintaining the integrity of the sealing substrate 4.

[0044] In relation to the figures, the method provides for forming on the blank fold lines arranged to allow the folding of said blank into a prismatic envelope 8 with a triangular base.

[0045] To do this, the method provides for forming such lines 7 on the side so as to define:

[0046] - a side panel 9 of quadrilateral geometry intended to form a side wall 10 of the envelope 8;

[0047] - two panels, respectively lower 11 and upper 12, of triangular geometry, each having an internal edge which is connected by a fold line 7a to respectively a large external side of the side panel 9, said lower and upper panels being intended to form respectively a lower wall and an upper wall 13 of the envelope 8;

[0048] - two side panels 14 each having a quadrilateral geometry presenting an internal edge which is connected by a fold line 7b to respectively an external side of a respectively lower 11 and upper 12 panel, said side panels being intended to form together a side wall 15 of the envelope 8;

[0049] - a border having two outer strips 16 each having an inner edge which is connected by a fold line 7d to respectively an outer edge of a side panel 14, said outer strips being arranged to be sealed to each other to form a sealing backing 17 of the side wall 15 of the envelope 8; - a rear panel 18 having a front edge which is connected by a fold line 7c to a rear edge of the lower 11, side 9, 14 and upper 12 panels, said rear panel being intended to form a rear wall of the envelope 8.

[0050] The lower 11 and upper 12 panels each have a geometry in the shape of an isosceles triangle, the base of which forms the rear edge which is defined by the fold line 7c separating said lower panel from the rear panel 18.

[0051] The outer strips 16 of the border extend to the rear edge 19 of the blank, and the border has a rear strip 20 which extends between the rear ends of said outer strips and all along the rear edge 19 of said blank, said rear strip being connected by a fold line 7e to a rear edge of the rear panel 18, being arranged to be sealed on itself to form a sealing hem of the rear wall of the packaging.

[0052] In the embodiment shown, the packaging provides for folding the blank along its fold lines 7a, 7b, 7c, 7d, 7e to form a prismatic envelope 8 with a triangular base having a lower wall, two side walls 15, an upper wall 13 and an open rear mouth 21.

[0053] To do this, we plan to fold successively:

[0054] - lines 7a defining the large external sides of the side panel 9, so as to erect the lower 11 and upper 12 panels to form the lower and upper walls 13 of the envelope 8;

[0055] - lines 7b defining the respective external edges of the lower 11 and upper 12 panels, so as to fold the side panels 15 opposite the side panel 9 to form the side wall 15 of the envelope 8;

[0056] - the lines 7d defining the respective external edges of the side panels 14, so as to erect the outer strips 16 of the border by arranging their respective inner faces against each other (figure 2). In particular, at the end of these folding steps, an envelope 8 is obtained with an open rear mouth 21 (figure 2), and the inner face of the rear strip 20 of the border delimits an inner periphery of said rear mouth.

[0057] The packaging then provides for sealing the outer strips 16 of the border, in particular by sealing on itself, by a “flesh-flesh” type association, the sealing layer 4d covering the respective inner faces of said outer strips, so as to form a sealing backing 17 of the side wall 15 of the envelope 8.

[0058] In particular, since the outer strips 16 extend to the rear edge 19 of the blank, their sealing makes it possible to obtain a sealing backing 17 which closes the periphery of the rear mouth 21.

[0059] Then, the backing 17 is folded back onto the side wall 15 of the envelope 8 after it has been sealed.

[0060] The food portion 1 can then be packaged in the packaging through the rear mouth 21, before folding the rear panel 18 to close said mouth.

[0061] Thus, a mold is formed by means of the envelope 8, into which the food portion 1 can be poured in liquid or viscous form before closing said envelope, which makes it possible to limit production costs by avoiding an additional step of shaping said food portion before packaging in the package.

[0062] This arrangement also makes it possible to produce food portions 1 packaged more hygienically and with better storage conditions. Indeed, by pouring the food portion 1 directly into its individual packaging, its exposure to ambient air is limited, which limits the risk of contamination, particularly by germs. Furthermore, if the food portion 1 is poured at a temperature higher than the pasteurization temperature, this further improves its storage properties.

[0063] To fold the rear panel 18, the method provides for extending the fold lines 7a, 7b and / or 7d defining the outer and inner edges of the lower 11, side 9, 14 and upper 12 panels on said rear panel, so as to form lower 22, side 23 and upper 24 sectors therein, said folding being carried out by folding flat the side sectors 24 to fold down the upper 24 and lower 22 sectors, as shown in Figure 2e.

[0064] To be able to close the mouth 21 tightly, the process then provides for:

[0065] - folding the rear strip 20 flat, by placing an upper portion of the inner face of said rear strip on a lower portion of said inner face;

[0066] - seal the inner face of the rear strip 20, by a “flesh-flesh” type association of its upper and lower portions, in order to form the sealing hem of the rear wall.

[0067] This embodiment allows in particular continuous sealing of the inner face of the rear strip 20, guaranteeing optimal sealing due in particular to the absence of any excess thickness in said sealing.

[0068] In the embodiment shown, the method provides for extending the fold lines 7a, 7b and / or 7d of the rear panel 18 onto the rear strip 20 of the border, so as to form on said rear strip lower 25, lateral 26 and upper 27 sectors in the rear extension of the corresponding sectors 20, 21, 22 of said rear panel.

[0069] Thus, the flat folding of the rear strip 20 is carried out by placing the inner face of the upper sector 27 on the inner face of the lower sector 25, and by folding on itself the inner face of each of the lateral sectors 26.

[0070] Especially :

[0071] - the different folding lines 7a, 7b and / or 7d are extended in a rectilinear manner, which makes it easier to manufacture the blank and fold the envelope 8; and

[0072] - the respective lateral sectors 23, 26 of the rear panel 18 and the rear strip 20 are provided with fold line patterns arranged to allow them to be folded flat.

[0073] In particular, the folding lines formed on and near the lateral sectors 23, 26 are arranged to allow the folding of said sectors in the form of lateral bellows of triangular geometry, the sealing of the rear mouth 21 then being carried out:

[0074] - by folding said triangular gussets towards the inside of the packaging and on either side of the rear wall, then “flesh-flesh” sealing of the rear strip 20, the sealing hem thus formed then being folded over a lower portion of the rear wall of the envelope 8; or

[0075] - by folding said triangular gussets towards the outside of the packaging then, after “flesh-flesh” sealing of the rear strip 20 and folding the sealing hem onto the rear wall, by folding each of said external gussets onto the adjacent side wall 15.

[0076] To facilitate opening of the packaging, in particular by young children and / or in connection with a soft food portion 1, the method provides for forming the fold lines so that the blank further has a front panel 28, which has a rear edge connected by a fold line 7f to a front edge of the outer strips 16 and the side panels 9, 14.

[0077] Each of the fold lines 7a defining the outer edges of the central side panel 9 extends to the front edge 29 of the front panel 29, forming, on either side of said line, an outer sector 30, in the extension of an outer side panel 14 and an adjacent outer strip 16, and a central inner sector 31.

[0078] In particular, the top of each of the upper 12 and lower 11 panels opens at the intersection between the internal sector 31 and one of the external sectors 30.

[0079] In relation to Figure 2, the front panel 28 is intended to be sealed to form, in the extension of the back panel 17, a sealing tab 32 for the tip of the packaging.

[0080] To do this, the method provides for sealing on itself the portion of the layer 4d covering the inner face of the front panel 28, so as to allow the formation of the tab 32 by “flesh-flesh” type sealing of said front panel.

[0081] To finalize the formation of the envelope 8, the method provides, after sealing the lateral backing 17 and the front tab 32, to:

[0082] - fold the backing 17 onto the side wall 15 of the envelope 8, so as to arrange the external part of the tongue 32 horizontally, formed by sealing the external sectors 30;

[0083] - fold down onto the other side wall the part of the tab 32 protruding in front of the tip of the packaging.

[0084] The method provides for forming on the blank at least one tear line 33 arranged so that manual pulling on the tab 32 induces a tear in said blank with a view to opening it.

[0085] In relation to Figures 1 to 3, the tear line 33 has two lateral segments 33a extending on the upper panel 12 along respectively a lateral edge of said panel, from a rear zone to a front zone of said panel, each of the segments 33a extending from said front zone to the external edge of an outer strip 16 crossing a side panel 14.

[0086] Thus, the tear line 22 is arranged so that manual pulling on the sealing tab 32 causes the blank to tear on either side of its tip, followed by propagation of said tear on either side of the upper wall 12.

[0087] This arrangement makes it possible to provide the consumer with packaging with a rigid tab 32 whose large dimensions make it easier to grasp it with the fingers, said tab also forming a lever arm to facilitate the initiation of tearing of said packaging along the line 33 formed for this purpose in said packaging.

[0088] In particular, each lateral segment 33a of the tear line 33 extends parallel to a respective lateral edge of the upper panel 12, which allows the consumer to open the packaging on either side of the front point and on the upper wall 13 of the envelope 8, and in particular outside the sealing backing 17, which is offset on a lateral wall 15 of said envelope, being crossed on its front zone by a portion of the tear line 33.

[0089] Thus, the consumer does not need to open the backing 17 to open the packaging, which makes it possible to optimize the sealing of said backing during storage of the packaged food portion 1 and to facilitate access to said food portion when opening its packaging, in particular thanks to the presence of a portion of the tear line 33 on a front zone of said backing.

[0090] Advantageously, the lateral segments 33a of the tear line 33 delimit between them and on the upper wall 12 of the envelope 9 a tearable zone whose surface area is greater than at least 80%, and in particular greater than 95% of the total surface area of ​​said upper wall. To do this, each lateral segment 33a extends in particular over more than 90% of the length of the adjacent upper lateral edge, while having an intrinsic length which remains less than 100% of said lateral edge length, in order to guarantee the separation of the tip from the rest of the packaging when it is opened.

[0091] Thus, the tear line 33 makes it possible to form in the envelope 8 a large opening to facilitate the extraction of the food portion 1 from the packaging.

[0092] In particular, each lateral segment 33a of the tear line 33 extends along the adjacent upper lateral edge, forming a strip 34 between them, so that, after opening the packaging, each strip 34 rests on an upper wall of the food portion 1, so as to keep a lateral wall 15 of the envelope 8 with which it is integral resting against it. This arrangement makes it possible to wedge the food portion 1 laterally on the lower wall of the envelope 8, while awaiting its extraction by the consumer, as shown in FIG. 3.

[0093] Each of the strips 37 has a width which is less than 10% of the width of the side panel 9 or of the sum of the widths of the adjacent side panel 14 and outer edge 16, and in particular less than 5% of said width or of said sum of widths. This arrangement makes it easier for the consumer to extract the food portion 1, who then simply has to move the side walls 15 apart to be able to remove said food portion from the lower wall of the casing while retaining its shape integrity, in particular in the case of a soft food portion 1.

[0094] Each lateral segment 33a has, at the junction between its front extension on the corresponding lateral panel 9, 14, a connecting elbow of curved geometry, the radius of curvature of which is arranged to guarantee a tear along the entire length of said segments. Each lateral segment 33a of the tear line 33 extends rectilinearly to the rear edge of the upper panel 12, and extends in particular onto the rear panel 18, as shown in FIG. 2.

[0095] Thus, by continuing his pulling force on the tab 32, the consumer can partially, but not completely, tear the rear wall of the envelope 8, so as to hold the food portion 1 between the untorn rear wall portion and the side walls 15, while waiting for the extraction of said food portion from the packaging by said consumer.

[0096] Furthermore, the lower panel 11 is devoid of a tear line, in order to remain attached to the envelope 8 after opening the packaging, thus forming a tray on which the food portion 1 can be held while waiting to be taken by the consumer.

[0097] The tear line 33 is obtained by partial ablation of material from the thickness of the blank, to a depth sufficient to form a weakening line allowing the tearing of said blank to be guided along said line. Advantageously, the line 33 can be formed by laser cutting with a different parameter setting at the connection bends described above, in order to facilitate tearing along said bends.

[0098] The method provides for forming the tear line 33 by ablation of material using a laser beam at a wavelength between 9.6 and 10.6 pm, in particular using a carbon dioxide laser beam at a wavelength close to 10.6 pm.

[0099] This solution makes it possible to use an industrial laser whose beam parameters can be configured so that the energy absorbed by the layer 3 based on cellulose fibers is sufficient to melt or vaporize said layer to a greater or lesser depth in order to form the tear line 33. In particular, the laser beam is configured to induce the formation of the tear line 33 by at least partial ablation of only the outer layer 3, insofar as the ablation of the substrate 4 would be detrimental to the sealing.

[0100] Advantageously, the laser beam is configured to ablate more than 80% of the thickness of the outer layer 3, in particular substantially 100% of said thickness, which allows a good compromise between preserving the sealing of the packaging and the ease of its opening by tearing along the tear line 33 thus formed.

[0101] Indeed, as shown in Figure 4, a line 33' formed by laser cutting at too shallow a depth leaves an outer layer 3 of cellulose fibers that is too thick to be easy to tear along said line.

[0102] Conversely, a 33” line formed by laser cutting to a depth that is too great, in particular greater than the total thickness of the outer layer 3, alters the integrity of the substrate 4, and therefore potentially the sealing properties of the packaging.

[0103] According to the invention, at least the outer layer 4a of the substrate 4 is formed from a material whose absorption to the laser beam is lower than that of the outer layer 3 and / or whose reflectivity to said laser beam is greater than 50%.

[0104] Thus, in the case where the laser beam would come onto the external layer 4a, for example due to the energy dispersions of said laser beam and / or the thickness and / or the density of the external layer 3, the low absorption and / or the high reflectivity of said beam by the external layer 4a makes it possible to avoid its damage.

[0105] Advantageously, the sealing substrate 4 in its entirety has a laser beam absorption which is lower than that of the outer layer, so as to guarantee its total integrity and therefore the sealing which it provides. According to one embodiment, the substrate 4 and / or the outer layer 4a of said substrate has a laser beam absorption which is less than 50% of the absorption of the outer layer 3, and in particular less than 10%.

[0106] In particular, such transparency can be obtained with an external layer 4a formed from a polyolefin, in particular a polyolefin which belongs to the polyethylene family.

[0107] In particular, as shown in Figure 4, the sealing substrate 4 preferably comprises, from the outside to the inside:

[0108] - an external layer 4a based on polyethylene;

[0109] - an internal 4c layer based on EVOH;

[0110] - an opposite layer 4b based on polyethylene;

[0111] - a food-grade 4d sealing layer, notably based on polylactic acid.

[0112] Alternatively or additionally, the outer layer 4a has a reflectivity to the laser beam which is greater than 80%, and in particular greater than 90%.

[0113] In particular, such reflectivity can be obtained with an external layer 4a based on metallic material, in particular based on aluminum, or whose external face is covered with a metallic film.

Claims

CLAIMS 1. Method for manufacturing a blank for packaging a food portion (1), said blank being formed from a complex (2) comprising an outer layer (3) based on cellulose fibers and an inner sealing substrate (4) comprising at least one outer layer (4a) associated with the outer layer (3), said method providing for: - forming fold lines (7a, 7b, 7c, 7d, 7e, 7f) on said blank to allow its conformation into an envelope (8) in which said portion can be packaged before closing said envelope; - forming at least one tear line (33) arranged so that manual pulling induces a tear in said blank for the purpose of opening it; said method being characterized in that the tear line (33) is formed by ablation of material by means of a laser beam at a wavelength between 9.6 and 10.6 pm, said method providing that at least the outer layer (4a) of the sealing substrate (4) is formed of a material whose absorption to said laser beam is lower than that of the outer layer (3) and / or whose reflectivity to said laser beam is greater than 50%, said laser beam being configured to induce at least partial ablation of only the outer layer (3).

2. Method according to claim 1, characterized in that it provides that the external layer (4a) of the sealing substrate (4) is formed from polyolefin.

3. Method according to claim 2, characterized in that it provides that the polyolefin belongs to the family of polyethylenes.

4. Method according to any one of claims 1 to 3, characterized in that it provides that the external layer (4a) of the substrate (4) has properties of sealing against oxygen and / or water vapor.

5. Method according to any one of claims 1 to 4, characterized in that it provides that the substrate (4) comprises an internal layer (4c) for sealing against oxygen and / or water vapor.

6. Method according to claim 5, characterized in that it provides a sealing substrate (4) comprising an external layer (4a) based on polyethylene, an internal layer (4c) based on ethylene-vinyl alcohol (EVOH) and an opposite layer (4b) based on polyethylene.

7. Method according to any one of claims 1 to 6, characterized in that it provides that the sealing substrate (4) has a sealing layer (4d) arranged opposite the outer layer (3).

8. Method according to any one of claims 1 to 7, characterized in that it provides that the external layer (4a) of the substrate (4) has a reflectivity to the laser beam which is greater than 80%, in particular greater than 90%.

9. Method according to any one of claims 1 to 8, characterized in that it provides that the sealing substrate (4) has an absorption to the laser beam which is lower than that of the outer layer (3).

10. Method according to any one of claims 1 to 9, characterized in that it provides a substrate (4) and / or an external layer (4a) of said substrate whose absorption to the laser beam is less than 50% of the absorption of the external layer (3).

11. Method according to claim 10, characterized in that it provides a substrate (4) and / or an external layer (4a) of said substrate whose absorption to the laser beam is less than 10%.

12. Method according to any one of claims 1 to 11, characterized in that the laser beam is configured for the ablation of more than 80% of the thickness of the outer layer (3), in particular of substantially 100% of said thickness.

13. Blank for packaging a food portion (1), said blank being formed from a complex (2) comprising an outer layer (3) based on cellulose fibers and an inner sealing substrate (4) comprising at least one outer layer (4a) associated with the outer layer (3), said outer layer being formed from a material whose absorption to a laser beam of a wavelength between 9.6 and 10.6 pm is lower than the absorption of the outer layer (3) and / or whose reflectivity to said laser beam is greater than 50%, said blank being manufactured according to a method according to any one of claims 1 to 12 to comprise: - folding lines (7a, 7b, 7c, 7d, 7e, 7f) allowing its conformation into an envelope (8) in which said portion can be packaged before closing said envelope; - at least one tear line (33) arranged so that manual pulling induces a tear in said blank with a view to opening it, said tear line being formed by at least partial removal of only the outer layer (3).

14. Blank for packaging a food portion (1) according to claim 13, characterized in that the complex (2) comprises between 60% and 90% by weight of cellulose fibers.

15. Blank for packaging a food portion (1) according to one of claims 13 or 14, characterized in that the outer layer (3) has a thickness of the order of 60 μm, the inner sealing substrate (4) having a thickness of between 4 μm and 20 μm.

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