PACKAGING COMPRISING A FOOD PRODUCT

Abstract

Packaging comprising a container having an open top and comprising a food product selected from vegetables, fruits and mushrooms, a film closing the open top of the container and being tightened over the food product to secure the food product in the container and so having contact areas with the food product. The film has a moisture vapour transmission rate (MVTR according to ISO 12572:2001, condition B at 1 bar, 38° C. and 50% relative humidity) of at least 350 g/m2.day.

Description

The invention relates to a packaging comprising a container having an open top and comprising a food product selected from vegetables, fruits and mushrooms, a film closing the open top of the container and being tightened over the food product to secure the food product in the container and so having contact areas with the food product.

In this way food products are often packed for transport and storage in the supermarket. Examples of such food products include mushrooms.

A problem is that the durability of the food products is limited by such a packaging, because at the contact areas the food product rots or deteriorates in another way. For example if mushrooms are packed in this way, at the contact areas the mushrooms show a discoloration, so that the mushrooms cannot be sold anymore. This while the parts were the mushrooms are not in contact with the film, the mushrooms are still in an excellent condition.

Aim of the invention is to diminish the rot, discoloration or any other way of deterioration at the contact areas of the food product and the film.

Surprisingly this object is obtained if the film has a moisture vapour transmission rate (MVTR according to ISO 12572:2001, condition B at 1 bar, 38° C. and 50% relative humidity) of at least 350 g/m².day.

In this way the decay of the food products at the contact areas where the film is in contact with the food product is retarded. This increases the shelf life of the products.

The container may be a box, a punnet, a basket, a tray, a platter etc.

Moisture vapour transmission rate (MVTR) is measured according to ISO 12572:1200, condition B at 1 bar, 38° C. and 50% relative humidity. The distance between the test sample and the desiccant is 10 mm.

The MVTR is preferably at least 800 g/m².day, more preferably at least 1200 g/m².day, even more preferably at least 1600 g/m².day. In order to prevent drying out of the food product the MVTR is preferably at most 10.000 g/m².day, more preferably at most 5000 g/m².day.

The film is tightened over the food product to secure the food product into the container and so having contact areas with the food product. Mushrooms are for example placed in a punnet or a basket and a film is tightened over the open top. In most cases the punnet or basket is just more than fully loaded, so that the mushrooms stick out of the open top. In this way the film is tightened over the mushrooms. Furthermore mushrooms tend to grow further in the packaging, so creating contact areas with the film or increasing the size of existing contact areas. A further example is fruit placed on a tray, for example apples or pears. To secure the fruit in the tray the film must be tightened over the fruit, so creating the contact areas.

Preferably the film comprises perforations, more preferably in the form of micro-perforations that may have a diameter of between 50 microns and 1000 microns, preferably between 100 and 800 microns. The density of the perforations may be up to about 1000 per m², preferably up to about 500 m². Perforation may take place either in a continuous or in a batch process. For example, the perforation may be effected by contacting the film with one or more rollers comprising pins or needles to punch the micro-perforations. Perforation may also be effected by use of laser technology. The perforation may take place in line with the production of the film.

Preferably the film is produced from a thermoplastic elastomer. One example is a thermoplastic copolyetheramide elastomer, comprising hard segments of a polyamide and soft segments of an aliphatic polyether. A further example of a suitable thermoplastic elastomer is a thermoplastic polyurethane (TPU). TPUs may be formed by the reaction between isocyanates, short chain doils or diamines and long chain diols or diamines. Preferably as long chain diols polyetherdiols are used.

Preferably a thermoplastic copolyester elastomer (TPE) is used as the thermoplastic elastomer. More preferably a copolyether ester is used as the thermoplastic polyester elastomer.

The copolyether ester suitably contains hard segments that are built up from repeating units derived from at least one alkylene diol and at least one aromatic dicarboxylic acid or an ester thereof. As alternative to segment, also the term block is being used. The linear or cycloaliphatic alkylene diol contains generally 2-6 C-atoms, preferably 2-4 C-atoms. Examples thereof include ethylene glycol, propylene diol and butylene diol. Preferably propylene diol or butylene diol are used, more preferably 1,4-butylene diol. Examples of suitable aromatic dicarboxylic acids include terephthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid or combinations of these. The advantage thereof is that the resulting polyester is generally semi-crystalline with a melting point of above 150, preferably above 175, and more preferably of above 190° C. The hard segments may optionally further contain a minor amount of units derived from other dicarboxylic acids, for example isophthalic acid, which generally lowers the melting point of the polyester. The amount of other dicarboxylic acids is preferably limited to not more than 10, more preferably not more than 5 mol %, so as to ensure that, among other things, the crystallization of the copolyether ester is not adversely affected. The hard segment is preferably built up from ethylene terephthalate, propylene terephthalate, and in particular from butylene terephthalate as repeating units. Advantages of these readily available units include a high melting point, resulting in copolyether esters with good processing properties, excellent thermal and chemical resistance and good puncture resistance.

Suitable the copolyether ester contains soft segments of an aliphatic polyether. The polyether may have a glass-transition temperature (T_g) of below 0° C. Preferably, the T_g is below −20° C., more preferably below 40° C., and most preferably below 50° C. The molar mass of the segments may vary within a wide range, but preferably the molar mass is chosen between 400 and 6000 g/mol, more preferably between 500 and 4000 g/mol, and most preferably between 750 and 3000 g/mol. Suitable aliphatic polyethers include a poly(alkylene oxide)diol derived from an alkylene oxide of 2-6 C-atoms, preferably 2-4 C-atoms, or combinations thereof. Examples include poly(ethylene oxide)diol, poly(tetramethylene oxide)diol or poly(tetrahydrofuran)diol, poly(neopentylene oxide-co-tetramethylene oxide)diol, poly(propylene oxide)diol Preferably copolyether ester contains soft blocks derived from a polyethylene oxide-terminated poly(propylene oxide)diol.

The copolyether ester may further contain a compound with two or more functional groups that can react with an acid- or hydroxyl-group, acting as chain extension or chain branching agent, respectively. Examples of suitable chain extension agents include carbonylbislactams, diisocyanates and bisepoxides. Suitable chain branching agents include e.g. trimellitic acid, trimellitic acid anhydride and trimethylol propane. The amount and type of chain extension or branching agent is chosen such that a block copolyester of desirable melt viscosity is obtained. In general, the amount of a chain branching agent will not be higher than 6.0 equivalents per 100 moles of dicarboxylic acids presenting the copolyether ester. The copolyether ester can further contain the usual catalysts and stabilizers.

Examples and preparation of copolyether esters are for example described in Handbook of Thermoplastics, ed. O. Olabishi, Chapter 17, Marcel Dekker Inc., New York 1997, ISBN 0-8247-9797-3, in Thermoplastic Elastomers, 2nd Ed, Chapter 8, Carl Hanser Verlag (1996), ISBN 1-56990-205-4, in Encyclopedia of Polymer Science and Engineering, Vol. 12, Wiley & Sons, New York (1988), ISBN 0-471-80944, p.75-117, and the references cited therein.

Particularly preferred is a copolyether ester with hard segments built up from butylene terephthalate units and soft segments derived from polyethylene oxide-terminated poly(propylene oxide)diol.

The film may suitably be prepared by extrusion, for example by the blown film process or cast film process.

Food products that may be stored in the packaging according to the invention generally include food products with a smooth surface, since such food products give rise to the presence of contact areas with the film. Examples of such food products include mushrooms, apples, pears, tomato's, mango's, peaches, paprika's, grapes, strawberries etc.

In the packaging according to the invention contact areas between the food product and the film may be present that have a surface of at least 10 mm². The invention shows its benefits especially if contact areas are present having a surface of at least 100 mm², even more if contact areas are present having a surface of at least 1000 mm².

The invention will be further explained in the figure.

FIG. 1 is schematic intersection of a box comprising mushrooms.

FIG. 2 is a schematic intersection of a tray comprising apples.

In FIG. 1 a schematic intersection of a box comprising mushrooms is shown. The box (1) is just more than fully loaded with mushrooms (2). The mushrooms stick somewhat out the box, so that the mushrooms are secured in the box by tightening the film (3) over the mushrooms, so to create contact areas (4) between the film and the mushrooms.

In FIG. 2 a schematic intersection of a tray (1) comprising apples is shown. At the tray apples (2) are placed. The film (3) has been tightened over the apples, to keep the apples in place at the tray. Between the apples and the film contact areas (4) are present.

COMPARATIVE EXPERIMENT A, B AND EXAMPLE I

Three boxes of length of 190 mm, a width of 135 mm and a height of 55 mm were just more than fully filled with mushrooms, as indicated in FIG. 1. A 25 micron nylon film (Akulon F 136, delivered by DSM, the Netherlands) (comp. exp. A) a 30 mm perforated PVC film (comp. exp. B) and a 25 mm copolyetherester film (Arnitel Arnitel VT3104) (Exp. I) were tightened over the mushrooms.

Moisture vapour transmission rate (MVTR) is measured according to ISO 12572:1200, condition B at 1 bar, 38° C. and 50% relative humidity. The distance between the test sample and the desiccant is 10 mm.

The MVTR of the nylon film is 100 g/m².day, the MVTR of the PVC film is 240 g/m².day, the MVTR of the copolyester film is 1880 g/m².day.

The boxes were stored at 8° C. and 50% relative humidity. In the boxes according to comparative experiment A and B the mushrooms showed discoloration at the contact areas between the mushrooms and the film after 7 days. The mushrooms of example I showed discoloration only after 10 days.

Claims

1. Packaging comprising a container having an open top and comprising a food product selected from vegetables, fruits and mushrooms, a film closing the open top of the container and being tightened over the food product to secure the food product in the container and so having contact areas with the food product, characterized in that the film has a moisture vapour transmission rate (MVTR according to ISO 12572:2001, condition B at 1 bar, 38° C. and 50% relative humidity) of at least 350 g/m2.day.

2. Packaging according to claim 1, wherein the MVTR of the film is at least 800 g/m2.day.

3. Packaging according to claim 1, wherein the MVTR of the film is at least 1200 g/m2.day.

4. Packaging according to claim 1, wherein the film is perforated.

5. Packaging according to claim 1, wherein the film comprises a thermoplastic elastomer.

6. Packaging according to claim 1, wherein the film comprises a thermoplastic copolyether ester elastomer.

7. Packaging according to claim 6, wherein the thermoplastic copolyether ester contains soft segments derived from polyethylene oxide-terminated poly(propylene oxide)diol.

8. Packaging according to claim 4, wherein the thermoplastic copolyether ester elastomer contains hard segments comprising repeating units of butylene terephthalate.

9. Packaging according to claim 1 containing as food product mushrooms, apples, pears, lemons, oranges, tomato's, mango's, peaches, apricots, paprika's, grapes or strawberries.