JP3460004B2 - Retort sterilized food packaging - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retort-sterilized package for processed meat foods such as hamburgers and meatballs. [0002] Conventionally, as a retort pouch of processed meat food, an ethylene / vinyl acetate copolymer having a melting point of 65 to 124 ° C,
A low-density polyethylene, a heat-sealing resin layer such as Surlyn is provided, and a transparent film such as polypropylene, polyethylene, or polyethylene terephthalate is laminated on the outer surface.
This bag is filled with processed foods such as hamburgers and meatballs and meat juice, and then the bag opening is heat-sealed at 120 to 140 ° C., and this is heat-sterilized in a retort pot at about 125 ° C. for 20 to 30 minutes. Retort pouches are sold. [0003] Recently, some consumers have requested that the contents of the retort pouch be visible from outside the package,
A gas barrier resin is used as a base layer (A1), and a thermoplastic resin heat seal layer (A) having a melting point of 65 to 124 ° C.
The laminated sheet obtained by laminating 2) is thermoformed to store food in the food storage recess of the transparent food container (A) provided with the food storage recess, and then the opening of the food container is removed by removing the surface layer. The product name, manufacturer, date of manufacture, etc. are printed on the back surface of the oriented polypropylene film (b1), and a biaxially stretched polyethylene terephthalate film (b3) is printed on the adhesive layer of a mixture of linear low-density polyethylene and branched low-density polyethylene (b1). b1 / b2 / b3 / b4 provided with a heat sealing layer (b4) having a melting point of 60 to 124 ° C. on the opposite surface.
With a transparent laminated sheet-like lid material (b)
Then, the heat seal layer (A2) of the container and the heat seal layer (b4) of the lid material were heated from 120 to 140 ° C. with a heating roll from the side of the lid material (b) and fused to seal the container. The sealed food container is placed in a retort kettle at a temperature of about 110 to 135 ° C. for 5 to 30 minutes and sterilized. [0004] This retort pouch food is put in boiling water as it is, or cooked, or the lid is opened, and the container is cooked in a microwave oven, or the contents are transferred into a pan, cooked and eaten. I have. Such a retort food curls to a height of 2 to 3 mm toward the lid at the heat-sealed portion of the container (A) and the lid (b) after the retort sterilization, particularly at the edge (flange portion) of the container. There is a drawback (Fig. 2), and since the lid material (b) is also transparent, the contrast with the printing of the lid material is poor due to the gravy, and the printed recipe,
There is a disadvantage that the date of manufacture is difficult to read. SUMMARY OF THE INVENTION The present invention relates to a retort-sterilized food package in which the contrast of characters and patterns printed on a cover material is clear and no curling of the edge of the container is observed. The purpose is to provide. According to the present invention, a gas barrier resin is used as a base layer (A1), and its surface has a melting point of 65-1.
A laminated sheet on which a thermoplastic resin heat seal layer (A2) of 24 ° C. is laminated is thermoformed to store food in the food storage recess of the transparent food container (A) provided with the food storage recess,
Next, a synthetic paper (B1) having an opacity of 85% or more and a whiteness of 85% or more made of a stretched microporous propylene-based resin film containing an inorganic fine powder was used as a base material. A gas barrier resin layer (B2, B2 ') made of a transparent stretched polyethylene terephthalate film is provided on the front and back surfaces of the substrate layer, and at least one surface of the gas barrier resin layer has a melting point. 65-
124 ° C. thermoplastic resin heat sealable resin layer (B3)
And a laminated sheet-like lid member (L4) provided with prints (B4, B4 ') between the synthetic paper (B1) and the gas barrier resin layers (B2, B2'). B) and then heat-sealing the container (A
2) and the heat sealing layer (B3) of the lid material is heat-sealed to seal the container, and then the sealed food container is heated to a temperature lower than the melting point of the propylene resin as the base resin of the synthetic paper (B1). The present invention provides a retort sterilized food package obtained by sterilizing using a retort pot. Since opaque synthetic paper is used for the base material layer of the lid material,
The contents of the container are not visible from the side of the lid material on which the product name, manufacturer, recipe, and pattern are printed, and the contrast between the printing and the whiteness of the synthetic paper is excellent, and the printing is easy to read. In addition to the biaxially stretched polyethylene terephthalate film for the cover material, a microporous synthetic paper made of an inorganic filler-containing propylene-based resin stretched film is used, and the biaxially stretched polyethylene terephthalate film is used on both front and back surfaces of the synthetic paper. Since the layers were laminated, no curl was observed at the flange portion of the container even after the retort sterilization treatment. (Specific Description of the Invention) Food container (A ) The food container (A) which has excellent gas barrier properties and can see through the inside has a gas barrier resin as a base layer (A1), and the surface thereof has a melting point of 65 to 124. It is a transparent food container (A) provided with a food accommodating concave portion by thermoforming a laminated sheet on which a thermoplastic resin heat seal layer (A2) at ℃ is laminated. Gas barrier resin (A1) Examples of the gas barrier resin include polyamides such as nylon 6, nylon 6,6, nylon 6,10 and nylon 12, having an ethylene content of 20 to 60 mol% and a saponification degree of 90.
% Or more of a saponified ethylene / vinyl acetate copolymer (ethylene / vinyl alcohol copolymer), polyethylene terephthalate, polyvinylidene chloride, etc., having an air permeability coefficient of 0 to 10 cc / m ² · 24 hours · atmospheric pressure, JIS Z- 0
The water vapor transmission rate measured at 20 ° C. according to Example No. 208 is 0.1-4 g /
A pressure of m ² · 24 hours / atmosphere is used. Heat sealable resin (A2) Examples of the heat sealable resin having a melting point of 65 to 124 ° C. include ethylene / vinyl acetate copolymer, maleic anhydride-grafted ethylene / vinyl acetate copolymer, ethylene / acrylic acid Copolymer, ethylene / methacrylic acid copolymer,
Ethylene / acrylic acid lower alkyl ester copolymer,
Ethylene / methacrylic acid lower alkyl ester copolymer, low density polyethylene, linear low density polyethylene, Surlyn, etc. can be used. [0011] laminated sheet laminated sheet, the above gas barrier resin (A1),
The laminated sheet may be manufactured by co-extrusion with the heat-sealable resin (A2), or may be manufactured by melt-extruding and laminating a heat-sealable resin film on the surface of the gas-barrier resin sheet. Since the gas barrier resin (A1) is expensive, polypropylene, propylene / ethylene copolymer, poly (4-methylpentene-1), propylene / ethylene / butene-1 copolymer, propylene / 3-methylpentene- An inexpensive and transparent polyolefin resin sheet (A3) such as copolymer 1 may be laminated to reduce the thickness of the gas barrier resin sheet of A1. When the adhesion between the gas barrier resin (A1) and the polyolefin is poor, the heat sealing resin, the polyether polyol / polyisocyanate, the polyester polyol / polyisocyanate, the polyethylene imine, the polyamine polyamide are used between the two. A primer such as an epichlorohydrin adduct is used to increase the adhesion between the two. The thickness of the laminated sheet is 0.3-2m
m, preferably 0.5 to 1 mm, and the thickness of the gas barrier resin is 5 μm to 1.98 mm, preferably 10 μm.
μm to 100 μm. The thickness of the heat-sealing resin layer is 5 to 80 μm, preferably 20 to 45 μm.
The thickness of the polyolefin resin layer is 0.27 to 1.95 m
m, preferably 0.3 to 0.9 mm. The thickness of both adhesive layers is 0.5 to 40 μm. Container (A) The container is formed by subjecting the laminated sheet to thermoforming such as vacuum forming, pressure forming, press forming and the like. The part is provided on the edge. Lid (B) The lid (B) has an opacity (JI) consisting of a stretched microporous propylene resin film containing inorganic fine powder.
SP-8138) is 85% or more, and whiteness (JIS L)
-1015) is 85% or more of synthetic paper (B1) as a base layer, and a gas barrier resin (B) made of a transparent stretched polyethylene terephthalate film is formed on the front and back surfaces of this base layer.
2, B2 ') and at least one surface of the gas-barrier resin layer is provided with a thermoplastic resin heat-seal layer (B3) having a melting point of 65 to 124 ° C and a thickness of 60 to 25.
It is a laminated film of 0 μm. Synthetic paper (B1) The microporous synthetic paper used for sharpening printing and preventing curling of the container of the retort-sterilized food packaging is as follows:
Opacity of 90% or more, preferably 93 to 100%, whiteness of 85% or more, preferably 95 to 110%, and a porosity calculated by the following formula (1) of 10 to 60%, preferably Is 15 to 45%, the thickness is 30 to 300 μm, preferably 50 to 120 μm, and the density is 0.6 to 1.0 g / c.
It is a water-resistant synthetic paper made of a stretched film made of a propylene resin containing m ³ inorganic fine powder. [Equation 1] Examples of such microporous synthetic paper include the following papers, and their production methods are described in the aforementioned patent publications. Biaxially stretched thermoplastic resin biaxially oriented film containing inorganic fine powder or organic filler at a ratio of 8 to 65% by weight (Japanese Patent Publication No. 54-31032, U.S. Pat.
No. 775521, U.S. Pat. No. 4,191,719, U.S. Pat. No. 4,377,616, U.S. Pat. No. 4,560,614). A biaxially stretched propylene-based resin film containing 5 to 40% by weight of inorganic fine powder is used as a base layer (1a), and a uniaxially stretched propylene-based resin containing 8 to 65% by weight of inorganic fine powder is formed into a paper-like layer ( 1b) (refer to JP-B-46-40794, JP-A-57-149363, JP-A-57-181829, etc.). This synthetic paper has a two-layer structure or a three-layer structure in which a paper-like layer of a uniaxially stretched film is present on the front and back surfaces of a base material layer (Japanese Patent Publication No. 46-40794). 3 layers in which another resin film layer exists between the paper-like layer and the substrate layer
Even in the case of a seven-layer synthetic paper (Japanese Patent Publication No. 50-29738, JP-A-57-149363, JP-A-56-126155 and JP-A-57-181829), the back surface is made of ethylene / methyl acrylate. Polymer, metal salt of ethylene / (meth) acrylic acid copolymer (Na, Li, Zn,
K), three or more layers of synthetic paper having a heat seal layer made of a resin having a lower melting point than the base layer resin such as chlorinated polyethylene (Japanese Patent Publication No. 3-13973). In order to further improve the offset printability on the surface of the synthetic paper, polyethyleneimine, poly (ethyleneimine-urea), an ethyleneimide adduct of a polyamine polyamide, an epichlorohydrin adduct of a polyamine polyamide, a tertiary to A coating layer for improving water-soluble printability selected from the group consisting of quaternary nitrogen-containing acrylic resins may be provided. An example of a three-layer synthetic paper is a uniaxially oriented film obtained by stretching a thermoplastic resin film containing 5 to 40% by weight of inorganic fine powder in one direction at a temperature lower than the melting point of the resin. 8 fine inorganic powders on both sides of the film
A paper-like layer obtained by laminating a thermoplastic resin-containing molten film containing up to 65% by weight and then stretching this laminated film in a direction perpendicular to the above direction is uniaxially oriented and has many fine voids. It is a film, and the base material layer is a laminated structure oriented biaxially. Of course, a layer of the primer (coating agent) may be provided on this surface to further improve the offset printability, and the base layer (1a) of the biaxially stretched film imparts a vertical and horizontal strength balance to the synthetic paper. And a uniaxially stretched film of a paper-like layer (1b, 1c)
Has a paper texture. On the paper-like layer side of the synthetic paper,
Highly glossy synthetic paper having a structure in which a transparent thermoplastic resin laminate layer having a thickness of 0.1 to 20 μm containing no inorganic fine powder is provided (Japanese Patent Publication No. 4-60437, 1
-60411, JP-A-61-3748).
For example, a biaxially stretched film of a propylene-based resin is used as a base layer (1a), and a surface layer (1b) and a backside layer (1c) composed of a uniaxially stretched film of a propylene-based resin containing 8 to 65% by weight of an inorganic fine powder. Is used as a support, a transparent film layer of a thermoplastic resin containing no inorganic fine powder is provided on the surface layer (1b) side of the support, and a coating layer (1d) having an antistatic function is further provided. Obtained synthetic paper (Japanese Patent Application Laid-Open No. 61-3748) or a biaxially stretched propylene-based resin film as a base material layer (1).
a) a paper-like layer (1b) composed of a uniaxially stretched film of a propylene-based resin containing 8 to 65% by weight of an inorganic fine powder on at least one surface of the substrate layer; A synthetic paper provided with a laminate with a surface layer (1d) composed of a stretched film, wherein the thickness (t) of the surface layer (1d) is determined by the average particle size of the inorganic fine powder present in the paper-like layer. Synthetic paper comprising a multilayer resin film satisfying the following formula (2) when the diameter is (R) (Japanese Patent Publication No. 1-60411). ## EQU2 ## R ≧ t ≧ 1/10 × R (2) As a propylene-based resin for synthetic paper, propylene homopolymer, propylene as a main component, ethylene, butene-1 And hexene-1, pentene-1, octene-1, 4-methylpentene-1, and 3-methylpentene-1. The copolymer may be a random copolymer or a block copolymer. In order to improve the stretchability, a resin having a melting point lower than that of polypropylene, such as polyethylene, polystyrene, or ethylene / vinyl acetate copolymer, is used in the base layer in an amount of 3 to 2 times.
It is better to mix 5% by weight. In addition, as inorganic fine powder, calcium carbonate, calcined clay, silica, diatomaceous earth,
Talc, titanium oxide, barium sulfate, etc., with a particle size of 0.03
16 microns are used. The stretching ratio is preferably 4 to 10 times in both the vertical and horizontal directions, and the stretching temperature is 140 to 1
62 ° C. The stretching speed is 50 to 350 m / min. If the opacity of the synthetic paper is less than 90% and the whiteness is less than 85%, the appearance of the print will be poor. The thickness of the synthetic paper is 30 to 300 μm, preferably 50 to 120 μm
If it is less than 30 μm, it is difficult to stably produce synthetic paper, and if it exceeds 300 μm, there is no difference in the effect of curl prevention, the cost of the lid material is high, and it is only economically disadvantageous. . The presence of fine voids (voids) in the synthetic paper contributes to the improvement in the opacity of the synthetic paper. However, the presence of the voids has a heat insulating effect, and the flange of the container is heated and sterilized in a retort pot. It seems that this also contributes to the fact that the part does not curl. Stretched polyethylene terephthalate film
(B2, B2 ') stretched polyethylene terephthalate film (OPET)
Is transparent and usually has a thickness of 8 to 80 μm from the market. Preferably 8 to 25 μm is economical. The stretching temperature of this film is about 100-130 ° C
In general, Heat-Sealable Layer (B3) The resin of the heat-sealable resin layer (B3) of the lid material fused to the heat-sealable resin layer (A2) of the container is the same as the heat-sealable resin layer of the container. The listed ones can be used.
The thickness of the heat-sealing resin layer (B3) is 5 to 50 μm.
m, preferably 20 to 40 μm. [0027] Print product name, manufacturer, recipes, printing of images, etc. (B4) is,
It may be performed on synthetic paper or on a stretched polyethylene terephthalate film. Also, printing (B4 ') for improving the appearance of the contents may be performed on either side of synthetic paper or OPET. This printing is performed by solid printing such as yellow, orange, and ultramarine, yellow / ultramarine. Is printed on the stripe pattern. The laminate of the stretched polyethylene terephthalate film and the heat-sealable resin is melt-laminated with the stretched polyethylene terephthalate film at a temperature at which the stretched film does not thermally shrink, or both films are bonded using a primer. Laminate. As the primer, a liquid polyisocyanate / polyether polyol, for example, EL-150 (trade name) or BLS-20 of Toyo Morton Co., Ltd.
A mixture of 80A and BLS-2080B is a polyisocyanate / polyester polyol such as the company's AD
-503 (trade name), and polyvinyl acetate aqueous emulsion, for example, MB-100 manufactured by Seiden Chemical Co., Ltd.
(Trade name) and vinyl acetate / alkyl acrylate copolymer emulsion can be used. Lamination of the synthetic paper and the stretched polyethylene terephthalate film is performed using the above primer. The coating amount of the primer is 0.1 to ²⁰ g / m ² , preferably 0.5 to 8 g / m ² in terms of solid amount.
² [0030] retorting food package diagram container 1 of the storage recess 2 as shown in 1, hamburger, and processed foods 3 meatballs, put gravy 4 necessary, the lid to the opening of the container 1 5 is led so that the printing of the manufacturer, product name, etc. is on the outside, and the heat sealing resin layer side of the lid material is heated to 120 to 140 ° C. to soften it,
By pressing with a roll, the container 1 and the lid material 5 are
And heat-sealed. Then put this in the retort pot,
By heat sterilization at 110 to 140 ° C. for 5 to 40 minutes, the retort sterilized food package 7 of the present invention is obtained. The present invention will be described in more detail with reference to the following examples. Production Example of Synthetic Paper (Example 1) (1) Melt Flow Rate (MFR) 0.8 g / 10
% Of polypropylene (melting point: about 164 to 167 ° C.), 3% by weight of high-density polyethylene and average particle size of 1.
The composition (A) in which 16% by weight of 5 μm calcium carbonate is mixed is kneaded with an extruder set at a temperature of 270 ° C., extruded into a film, and further cooled by a cooling device to obtain an unstretched film. Was. After the film was heated again to a temperature of 150 ° C., it was stretched five times in the machine direction to obtain a five-fold machine film. (2) A composition (B) obtained by mixing 54% by weight of polypropylene (melting point: about 164 to 167 ° C.) having an MFR of 4 g / 10 minutes and 46% by weight of calcium carbonate having an average particle size of 1.5 μm was prepared. And kneaded at 210 ° C. with an extruder, extruded into a film by a die, and laminated on both sides of the 5-fold longitudinally stretched film obtained in the above step (1) to form a three-layer structure. A film was obtained. Next, after cooling the laminated film having the three-layer structure to a temperature of 60 ° C., the film is heated again to a temperature of about 155 ° C., stretched 7.5 times in a transverse direction using a tenter, and then heated at a temperature of 165 ° C. Annealing treatment, cooling to a temperature of 60 ° C., slitting of ears, three-layer structure (uniaxial stretching / biaxial stretching / uniaxial stretching)
60 μm (B / A / B = 15 μm / 30 μm / 1
5 μm) with a porosity of 33% and a density of 0.7
A multilayer synthetic paper having 8 g / cm ³ , 85% whiteness, 91% opacity, and breaking strength of 7 kg / cm ² was obtained. After the surface of this three-layer laminated film was subjected to corona discharge treatment, the following coating solution containing an antistatic agent (A) and (B) was applied on both surfaces in 0.05 g / solid as solid content.
m ² (thickness: about 0.1 μm), dried, and wound up. The composition of the aqueous coating solution is as follows. (A) “Antistatic agent” manufactured by Mitsubishi Yuka Corporation
Acrylic resin aqueous solution "ST-1100" (trade name)
[Including the following group (1) in the molecular molecular chain]: 100 parts by weight (B) Epichlorohydrin adduct of water-soluble polyamine polyamide (Tick Hercules “Kaimen 5
57H ": 25 parts by weight of the obtained synthetic paper had a glossiness of the coating agent layer of 15% and a Beck smoothness of 680 seconds. Example 2 (1) Melt flow rate (MFR) 4.0 g / 10
(A) obtained by mixing 25% by weight of high-density polyethylene and 20% by weight of calcium carbonate having an average particle size of 1.5 μm with 55% by weight of polypropylene (melting point: about 164 to 167 ° C.) at a temperature of 270 ° C. After being kneaded by the extruder, the mixture was extruded into a film and further cooled by a cooling device to obtain a non-stretched film. (2) Then, after the film was heated again to a temperature of 150 ° C., it was stretched 5 times in the machine direction to obtain a 5 times stretched film. Next, the film was heated again to a temperature of 155 ° C., stretched 7.5 times in the transverse direction using a tenter, and annealed at a temperature of 165 ° C.
Cool to a temperature of 0 ° C. and slit the ears to a density of 0.
88 g / cm ³ , opacity 86%, burst strength 3 kg / c
A microporous film composed of a biaxially stretched film having an m ² thickness of 45 μm and a porosity of 37% was obtained. After the surface of the biaxially stretched film is subjected to a corona discharge treatment, an aqueous solution of the coating agent is solidified on both surfaces in 0.05 g / m ² on one side (thickness: about 0.1 μm).
It was applied and dried so as to obtain a film, and was wound up. The composition of the aqueous coating solution was as follows. (A) Aqueous resin solution "ST-1100" of "Antistatic agent" manufactured by Mitsubishi Yuka Co., Ltd. "ST-1100": 100 parts by weight (a) Epichlorohydrin adduct of water-soluble polyamine polyamide ("Caimen 5" manufactured by Tick Hercules)
57H ": 25 parts by weight of the obtained synthetic paper had a glossiness of the coating agent layer of 33% and a Beck smoothness of 3800 seconds. (Example 1) (Molding of container) Propylene homopolymer (melting point: about 168)
° C), maleic anhydride-grafted polypropylene (Modic; trade name, manufactured by Mitsubishi Yuka), polyethylene terephthalate (melting point: about 234 ° C), and an ethylene content of 95.
6% by weight of ethylene / vinyl acetate copolymer (melting point: about 88
C.) and melt-kneaded in separate extruders, supplied to one co-extrusion die, laminated, co-extruded into a sheet, cooled, and cooled to 0.6 m polypropylene (PP).
m, Modic 20 μm, PET 20 μm, and 25 μm ethylene-vinyl acetate copolymer (EVA) transparent (4.8% haze) laminated sheet (PP / Modic / PE)
T / EVA; total thickness 665 μm). The laminated sheet was heated to about 260 ° C. and vacuum formed to obtain a container having a recess (2 cm deep) and a flange (5 mm width). (Manufacture of Lid Material) The synthetic paper obtained in Example 1 was subjected to multicolor gravure printing on a surface of a manufacturer, a trade name, a recipe, and a hamburger pattern, and solid printing was performed on the reverse side with yellow gravure printing ink. On both of these printing surfaces, a polyurethane anchor coating agent “BLS-” of Toyo Morton Co., Ltd. was used as a primer.
2080A "and" BLS-2080B "were applied at a rate of ² g / m2 (solid portion ratio), and then an ethylene / vinyl acetate copolymer (melting point of about 90
° C) Biaxially stretched polyethylene terephthalate film (OPET; laminated film (thickness 30 μm))
A biaxially stretched polyethylene terephthalate film (12 .mu.m
μm) to obtain a lid material having a thickness of about 118 μm. (Manufacture of the package) A processed meat hamburger is put in the container, and after pouring the gravy, the opening of the container is closed with a lid heated to 125 ° C, and the lid is pressed with a roll. The container was pressed and the lid material was fused. This was put in a retort pot and heat-sterilized at 125 ° C. for 30 minutes to obtain a retort-sterilized food package. No curl was observed at the container flange portion (0.1 mm or less), and the container was not deformed. (Example 2) Instead of the synthetic paper of Example 1, Example 2
A retort-sterilized food package was obtained in the same manner as in Example 1 except that the synthetic paper was used. The curl of this container was as small as about 0.5 mm, which was no problem as compared with the conventional product of 2 to 3 mm. (Examples 3 and 4) A retort was prepared in the same manner as in Example 1 except that the ethylene terephthalate used in the container was replaced by ethylene (about 22 mol%) / vinyl alcohol copolymer or nylon 6. A sterilized food container was obtained. The performance of the obtained food container is shown in Example 1.
Did not change. In the food package of the present invention, since the lid is opaque, the contents cannot be seen through from the lid side, and characters and designs printed on the lid can be clearly seen. Further, the conventional curl is not found in the flange portion of the container that has been sterilized by the retort.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a lid and a container according to the present invention. FIG. 2 shows a conventional retort sterilized food package curled toward the lid side. FIG. 3 is a manufacturing process diagram of the retort sterilized food package of the present invention. [Description of References] A Food container A1 Gas barrier resin base layer A2 Heat seal layer B Cover material B1 Synthetic paper base layer B2 Gas barrier resin layer B2 'Same as above B3 Heat seal resin layer B4 Print B4' Same as above b Cover material b1 Polypropylene film b2 Adhesive layer b3 Biaxially oriented polyethylene terephthalate film (OPET) b4 Heat seal layer

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B65D 81/24 B32B 27/00 B32B 27/10 B65D 3/22 B65D 77/00

Claims (1)

(57) [Claim 1] A laminated sheet in which a gas barrier resin is used as a base layer (A1) and a thermoplastic resin heat seal layer (A2) having a melting point of 65 to 124 ° C is laminated on the surface thereof. The food is stored in the food storage recess of the transparent food container (A) provided with the food storage recess by thermoforming, and the opening of the food container is closed with a microporous propylene-based material containing inorganic fine powder. A gas barrier comprising a transparent stretched polyethylene terephthalate film on the front and back surfaces of a synthetic paper (B1) having a opacity of 85% or more and a whiteness of 85% or more made of a stretched resin film as a base layer. Resin layer (B
2, B2 ′) and a thermoplastic resin heat-sealable resin layer (B3) having a melting point of 65 to 124 ° C. on at least one surface of the gas barrier resin layer, Printing (B4, B2) is provided between the synthetic paper (B1) and the gas barrier resin layer (B2, B2 ').
4 ') is covered with a sheet-like lid material (B) having a laminated structure provided with the heat-sealing layer (A2) of the container and the heat-sealing layer (B3) of the lid material are heat-sealed to seal the container. And
Next, a retort sterilized food package obtained by sterilizing the sealed food container using a retort pot at a temperature lower than the melting point of the propylene resin as the base resin of the synthetic paper (B1).