Packaging film with engineered surface topography for controlled otr and wvtr

Abstract

A packaging material for perishable produce comprises a polymeric or biopolymeric film which includes an engineered surface topography to simultaneously control oxygen transfer rate (OTR) and water va

Description

Prakash Damodar KORDE FIELD OF THE INVENTION The present invention relates to polymeric or biopolymeric packaging materials for perishable food products that are respiring, moisture-sensitive, or prone to spoilage. More particularly, to surface topography engineered films that enable modified atmosphere packaging by simultaneous control of oxygen and water vapour transmission rates without the application added coatings and material. BACKGROUND OF THE INVENTION

[001] The present invention relates to a packaging material for perishable produce, comprising a film made from polymeric materials derived from fossil fuels such as polyethylene terephthalate (PET), polyethylene (PE), or oriented polypropylene (OPP) and / or biopolymers such as poly lactic acid (PLA), Polyhydroxyalkanoates (PHA), or cellulose-based bioplastics. The film’s surface topography is engineered by increasing the surface area and thickness manipulation to provide a controlled oxygen transmission rate (OTR) and water vapour transmission rate (WVTR). Further, the present invention relates to a packaging material for enhancing the shelf-life of perishable produce.

[002] Conventional methods of modifying the permeability of packaging films for perishable produce—such as laser microperforation—typically involve creating through-holes that can result in uneven gas exchange or undesired moisture accumulation. However, this results in loss of oxygen and subsequent loss of atmosphere control in the package. In contrast, the invention enables simultaneous and precise control of OTR and WVTR by altering the surface structure of the film without creating perforations as is current commercial practice.

[003] The scoring pattern, depth, and density are adjustable to tailor the permeability of the film to match the respiration characteristics of various types of produce. This results in a controlled internal atmosphere and optimised water vapour transmission rate and managing the head space atmosphere in a packaged item, thereby extending the shelf-life of the packaged produce. The invention is particularly advantageous as it avoids the drawbacks associated with microperforated films, offering improved consistency, shelf-life extension, and potential for use in recyclable monomaterial packaging without the addition of any materials such as coatings and spray.

[004] The packaging of perishable produce requires careful management of the internal atmosphere within the pack to balance two competing requirements: the control of headspace gases (typically oxygen, carbon dioxide, and nitrogen) and the removal of excess moisture. Existing commercial packaging systems typically address one of these requirements at the expense of the other. As a result, combination of laser micro perforations, film coating and or modified atmosphere packaging are resorted to at an implicit additional cost.

[005] In one conventional approach, packaging films are produced with large perforations to allow moisture to escape, thereby preventing condensation and microbial spoilage. However, these large perforations expose the contents directly to the ambient atmosphere, eliminating any possibility of controlling the internal gas composition. As a result, the respiration rate of the produce is not adequately managed, leading to accelerated spoilage and reduced shelf-life. In an alternative approach, packaging materials may incorporate microperforations or be entirely unperforated, with the aim of achieving a modified atmosphere by limiting the ingress and egress of gases. While this can provide acceptable control over headspace gas concentrations, the low permeability of these films to water vapour often leads to moisture accumulation within the package, resulting in fogging, decay, and poor visual presentation of the product. Thus, optimal control of both gas composition and moisture vapour is difficult to achieve using existing methods.

[006] Another strategy involves the use of bioplastic films, which typically exhibit high water vapour permeability due to their hydrophilic nature, and moderate oxygen permeability. These films can, in some cases, allow simultaneous control of both moisture and gas transmission. However, bioplastics tend to be significantly more expensive than conventional petrochemicalbased films—often costing four to eight times as much—and can suffer from reduced mechanical performance, lower thermal resistance, and variable behaviour when exposed to high humidity. Some bioplastics are also hygroscopic and alter their permeability and physical properties as they absorb moisture, making them difficult to convert and handle during packaging operations. For these reasons, while bioplastics offer environmental benefits, they are often not commercially viable for high-throughput packaging of perishable produce.

[007] Technologies based on laser perforation have also been developed to enable selective gas transmission through flexible films. These methods typically involve the creation of microholes using laser ablation, which allows control over oxygen and carbon dioxide transfer rates. In some cases, laser-perforated films are used in conjunction with Modified Atmosphere Packaging (MAP) systems, where the headspace is flushed with a predetermined gas mix during sealing. However, these approaches still rely on through-holes, which often allow uncontrolled water vapour exchange and can compromise moisture management within the pack. In addition, laser perforation systems often require complex calibration and may struggle to maintain consistency across different film types and thicknesses.

[008] Accordingly, there is a need for an improved packaging solution that permits simultaneous control of headspace gas composition and water vapour transmission, without requiring the use of expensive bioplastics or relying on full perforation of the film preferably without use of additional materials and coatings. Such a solution should be adaptable to standard packaging materials, be compatible with existing packaging lines, and provide enhanced shelf-life for perishable produce through optimised permeability characteristics in an efficient scalable way for manufacture.

[009] According to the present invention there is therefore provided surface topography engineered polymer or biopolymer films, engineered using laser scoring, embossing, or texturing during polymer extrusion, that enables modified atmosphere packaging by simultaneous control of oxygen and water vapour transmission rates and subsequently enhancing the shelf-life of the perishable produce stored within as described in the accompanying claims. SUMMARY OF THE INVENTION

[0010] In view of the foregoing, for overcoming the disadvantages of the existing packaging products, the object of the invention is to provide surface topography engineered polymer or biopolymer films that enables modified atmosphere packaging by simultaneous control of oxygen and water vapour transmission rates and subsequently enhancing the shelf-life of the produce stored within.

[0011] The present invention provides a packaging material for food products that are respiring, moisture-sensitive, or prone to spoilage, comprising a flexible polymeric film selected from polyethylene terephthalate (PET), polyethylene (PE), or oriented polypropylene (OPP), or a combination thereof. In one method, the film’s surface topography is modified by non-penetrating laser scoring to form a defined surface pattern that increases the surface area and adjusts the film’s permeability to oxygen and water vapour. In another method a calendaring roller is used as a tool to impart the required textured on the film’s surface as the film passes through effectively embossing. The resulting material has increased surface area and allows for the simultaneous control of oxygen transfer rate (OTR) and water vapour transfer rate (WVTR), thereby establishing a modified atmosphere within the package that significantly extends the shelf-life of the packaged produce. In yet another method, the surface of the film is textured while polymer or biopolymer extrusion. This is achieved by using extrusion dies designed to generate specific surface texture. Once again, the resultant material has increased surface area and allows for simultaneous control of OTR and WVTR,

[0012] Unlike traditional laser perforation or microperforation techniques that create through-holes in the film, the present invention employs a non-penetrating marking method, which preserves barrier integrity while enabling fine-tuned permeability control. This marking pattern is achieved through laser scoring, embossing, or texturing during the extrusion process. The marking pattern may take the form of lines, dimples, or other textured geometries and can be tailored for specific product types or moisture management needs.

[0013] The invention may be implemented using common recyclable films and is compatible with standard packaging machinery. It may be applied as an inline laser modification or by embossing using patterned rollers. The packaging material provides a commercially scalable, cost-effective, and sustainable solution to improve the storage life and reduce spoilage of perishable food products. DETAILED DESCRIPTION OF THE INVENTION

[0014] To clarify the above and other purposes, features, and advantages of this invention, specific embodiment of this invention is especially listed and described in detail as follows. The principal and mode of operation of this invention have been described and illustrated in its embodiments and examples. At the outset, a person skilled in the art will appreciate that this invention may be practiced otherwise than is specifically described and illustrated. The invention should not be limited by the above-described embodiment, method, and examples alone.

[0015] The said packaging that simultaneously controls OTR and WVTR is particularly valuable for food products that are respiring, moisture-sensitive, or prone to spoilage. Examples of such food products are fresh produce like fruits and vegetables, mushrooms; minimally produced or cut produce such as precut fruit mixes, salads, etc.; moist bakery products; cheeses; fresh seafood; ready-to-eat-meals and so on. A person skilled in the art shall appreciate that this invention does not relate to generating or manufacturing a material, but it relates to engineering the resulting topography of the packaging material to achieve simultaneous control OTR and WVTR.

[0016] The film used in the invention is typically of monomaterial construction to facilitate recyclability, though in some applications, laminate or blended material structures may be used. Suitable materials include polymeric film selected from PET, PE, PBAT, or OPP films; or biopolymeric film selected from polylactic acid (PLA), Polyhydroxyalkanoates (PHA), bio-based materials derived from renewable resources such as corn starch, sugarcane, and wood pulp, rice waste such as paddy straw, or cellulose-based bioplastics, which may optionally incorporate foodsafe coatings or treatments to enhance sealing or barrier performance. The thickness of the film generally ranges from about 10 pm to about 60 pm, depending on application and produce type.

[0017] With respect to surface topography engineering of the packaging film, it is desirable to increase the effective surface area of the film without compromising its integrity. An increased surface area can facilitate improved control over gas and moisture transmission rates by altering the diffusional pathways and interaction sites at the film interface. Such surface area modification may be achieved, as a second operation after the film is manufactured through non-penetrating techniques such as laser scoring, embossing, or engraving. Alternatively, it can also be achieved by generating textures during extrusion process. In all cases, the scoring, embossing, or texturing during extrusion is preferably non-penetrating and reducing the thickness meaning it does not create through-holes or continuous channels that breach the film structure, thereby preserving the barrier properties of the film. The design and arrangement of the mark patterns—whether linear, grid-based, random, or textured—play a critical role in determining the extent of surface area enhancement and the corresponding functional performance of the film. The selection of pattern geometry, depth, and density must therefore be carefully tailored to achieve the desired transmission characteristics while maintaining mechanical strength and product protection.

[0018] The synthesis and conversion of polymer or biopolymer films suitable for use in packaging applications, particularly for perishable produce, may broadly be categorised into three stages: blow moulding or extrusion, rolling or calendaring, and the final stage of converting to a product packaging using techniques such as printing. Surface modification techniques, such as laser scoring or embossing, may be applied at any of these stages depending on the desired process integration, equipment configuration, and film characteristics. During the moulding stage, surface topography may be introduced by incorporating texturing elements into the mould or casting surface. Alternatively, in the rolling or calendaring stage, embossing may be applied via engraved rollers to impart a defined pattern onto the film surface as its thickness is being changed and formed. To generate texture on films embossing or engraving rollers can be made using commonly used machining methods to generate desired pattern. The topography change can be performed as an option at the final packaging stage, such as during flow wrapping or lidding, laser scoring may be employed in-line to create precise, non-penetrating patterns without significantly altering the material’s mechanical or barrier properties. The selection of the modification stage may be determined based on production efficiency, desired feature resolution, and compatibility with downstream processing.

[0019] In case of PE and PP films, the polymers are typically extruded. It is submitted that surface textures can also be created during the extrusion stage. Required texture can be generated by using a texture die during extrusion. Specifically, this surface texturing is achieved by designing specialized extrusion dies, which are calibrated with specific parameters to produce grooves or other surface features as required. The configuration of the die directly influences the geometry and distribution of the texture formed on the extruded film. Die design parameters that may be calibrated include die lip geometry, die gap width, surface patterns on the die, temperature profile, extrusion pressure, polymer melt viscosity, draw ratio or stretching rate, chill roll design and texture, line speed or throughput rate, and optional inline embossing systems.

[0020] An effective packaging solution for fresh produce or other perishable food products is understood to require a precise balance of multiple interrelated parameters, including but not limited to the selection of film material, the implementation of surface modifications such as scoring or embossing, and the controlled regulation of oxygen transfer rate (OTR) and water vapour transmission rate (WVTR). Different food products exhibit distinct respiration profiles and varying sensitivities to oxygen and moisture ingress or egress, thereby necessitating individualized control of headspace gas composition to establish and maintain a modified atmosphere conducive to extending shelf life. For strawberries, which have a high respiration rate, an OTR in the range of 8,000-15,000 cc / m2 / day and a WVTR between 10-20 g / m2 / day is typically suitable. This allows for sufficient gas exchange while controlling humidity to prevent mold and dehydration. Mushrooms require even higher breathability, with OTR values ranging from 50,000 to 150,000 cc / m2 / day and WVTR between 15-40 g / m2 / day, due to their extremely high respiration and moisture content. Bread, on the other hand, is highly sensitive to oxygen and moisture loss; it benefits from a low OTR of 500-2,000 cc / m2 / day and a very low WVTR below 5 g / m2 / day to inhibit mold growth and maintain softness. Cheese packaging needs vary by type, but in general, soft and semi-soft cheeses require a low OTR of around 10-100 cc / m2 / day to limit oxidation and mold while maintaining some breathability, and a WVTR of 1-10 g / m2 / day to avoid drying or excessive moisture buildup.

[0021] As such, a single film composition or structure may not be universally applicable across diverse food types. The choice of film material must therefore be made based on the specific barrier and mechanical performance required for the intended food application. While laser scoring techniques are known in the art and may be suitable for certain applications, such techniques may not be viable for use with thin films due to limitations in structural integrity or process resolution. In such instances, surface embossing may provide a preferable alternative for imparting the desired surface topography. It is further recognized that the type of embossing tool and the texture imparted therefrom must be selected and optimized on a case-by-case basis in accordance with the properties of the film and the target food product. A person skilled in the art, having knowledge of food packaging requirements and material processing techniques, will be capable of determining the appropriate combination of film material, surface engineering method, and OTR / WVTR tuning necessary to achieve an optimal packaging solution tailored to a specific product.

[0022] The present invention relates to a packaging film for use in the packaging of fresh produce and other perishable food products. More specifically, the invention concerns a flexible film made from polyethylene terephthalate (PET), polyethylene (PE), or oriented polypropylene (OPP), which is selectively surface texture engineered to modify its permeability characteristics. The invention enables simultaneous control of oxygen and water vapour transmission rates (OTR and WVTR, respectively), thereby improving shelf-life and reducing food waste, without compromising recyclability or requiring expensive or difficult-to-handle materials.

[0023] To achieve the desired permeability characteristics, the film is subjected to surface modification using a laser-scoring process or alternatively embossing via a textured roller in the calendering step of production. Suitable laser types include, but are not limited to, CO2 lasers and nanosecond fiber lasers. The choice of laser system, along with the power settings, focal length, and scanning speeds, can be tailored according to the specific material type and thickness. Importantly, the scoring is non-penetrating — the laser modifies the surface of the film without creating through-holes, thereby maintaining the integrity of the packaging barrier while altering its gas and moisture permeability. In an alternate method, surface modification is achieved by embossing method. Rollers are employed for embossing. CNC milling can also be used where engraving is done by diamond tool for precision. It should be noted that both heat and pressure shall be required for achieving texturing via embossing. A person skilled in the art shall appreciate that this calibration of parameters is required for achieving optimal surface texture specific to the film material. For example, Texturing OPP film by hot roller typically involves heating the film between two rollers, often to temperatures ranging from 135°C to 150°C for preheating and slightly lower for the stretching roll (125-135°C). The optimal temperature range for texturing PET film using a hot roller process typically falls between 70°C and 90°C. However, embossing may require higher temperatures, potentially reaching 220°C. The specific temperature needed depends on the desired texture, the type of PET film, and the equipment used. These temperature range for PE films fall within 160-175°C.

[0024] The marking patterns directly correlates to the desired surface area increase. And can also be adjusted to achieve desired aesthetic aspects such as opacity of the final packaging material. The marking patterns may include linear grooves, non-continuous lines, dimples, or geometric textures, all designed to increase the effective surface area of the film. The groove depth is preferably less than 50% of the original film thickness. Line densities of approximately 1.0 mm, to 5.0 mm are typically used. The exact geometry and spacing of the scoring can be adapted to meet the OTR and WVTR targets required for different types of produce.

[0025] The modified films achieve an optimal balance between OTR and WVTR. Water vapour transmission is increased relative to unmodified films, helping to eliminate condensation and reduce microbial spoilage. Simultaneously, the oxygen transmission rate is maintained at a sufficiently low level to support modified atmosphere packaging (MAP) conditions that reduce plant metabolism, enzymatic browning, softening, and colour loss. For example, shelf-life extension trials have demonstrated that the shelf-life of strawberries was extended by up to 3 days, while mushrooms showed a shelf-life increase of 2 days when packaged using the laser-scored film.

[0026] The films are suitable for use in a range of packaging formats including tray lidding, skillet lidding, and pillow packs. They can be supplied in roll form and are compatible with standard packaging machinery. The laser-scoring process may be implemented as an in-line modification during film production, similar to traditional printing processes. Alternatively, film texturing can be achieved by the use of pre-patterned rollers which emboss the desired pattern onto the film surface, offering a scalable and efficient route for high-volume manufacture without requiring direct laser contact with each unit of film. CNC milling can also be used in this method where engraving is done by diamond tool for precision.

[0027] The invention offers significant advantages over existing packaging technologies. Current systems that rely on large perforations allow moisture to escape but provide no control over headspace gas composition. Conversely, systems using microperforations can regulate gases but trap excess moisture, leading to condensation and spoilage. Some bioplastics offer improved WVTR but are expensive, hygroscopic, and mechanically unstable, limiting their commercial viability. The present invention addresses these issues by using low-cost, readily available, recyclable materials, modified in a controlled manner to deliver optimal permeability properties.

[0028] Laser-perforated films and MAP systems are commonly used in the packaging of perishable produce. In these systems, a laser ablates through-holes in the film, allowing passive or active gas exchange. These are sometimes combined with MAP, where the headspace is flushed with a gas mix during sealing. However, such systems are sensitive to hole size and consistency, may allow uncontrolled moisture transmission, and do not permit independent control of OTR and WVTR. The present invention differs fundamentally by avoiding through-holes altogether, using non-penetrating scoring to precisely adjust surface area and thereby tune gas and vapour transmission. This results in a more consistent and tunable packaging environment, particularly suited to high-respiration produce items.

[0029] The invention provides strong sustainability credentials through the use of recyclable materials and reduction of product waste via improved shelf-life. It is cost-effective to produce, compatible with existing manufacturing lines, and applicable to a wide range of food products including fruits, vegetables, cheeses, and ready-to-eat meals. Example 1 - Test for assessing WVTR, OTR, and shelf-life enhancement of films on strawberries. Samples of PET with thickness of about 19 pm were used. A roller tool was engraved with a pitch of 1.5 mm between the grooves. Subsequently, films were embossed using these rollers to mark patterns of straight lines with 1 mm, 1.5 mm, and 2. Commercial control punch perforated films were used as control samples. Tests were performed in order to determine and evaluate changes in WVTR, OTR and improvement in shelf-life of strawberries. Any physical changes in the fruits, for e.g. softening, ripening, browning, colour loss, or microbial spoilage were also evaluated. Result - WVTR sufficiently high to remove excess moisture. OTR was sufficiently low to modify headspace gas atmosphere. The simultaneous control of OTR and WVTR was seen to slow plant tissue metabolism, slow the rate of softening and loss of texture, enzymatic browning and colour loss, and microbial spoilage. Shelf-life of Strawberries was increased by +3 days. Film / Treatment Film Gauge (thickness, pm) Test Product WVTR gH2O / m2 / day OTR (cm3O2 / m2 / day) Estimated Shelf- Life Gain (Days) Commercial Control Punch Perforated 19-42 Strawberries >900 > 1,000,000 (no modified atmosphere) 0 Pet 2.0 mm embossed 19 Strawberries 318.0 163 + 3 Pet 1.5 mm embossed 19 Strawberries 372.0 214 Pet 1.0 mm embossed 19 Strawberries 549.0 265 Example 2 - Test for assessing WVTR, OTR, and shelf-life enhancement of films on mushrooms. Samples of PET / PE films with thickness of about 42 pm were used. Films were scored to mark patterns of straight lines with 1 mm, 1.5 mm, and 2 mm using a 125 W CO2 laser marking system. 10.25 pm and 10.60 pm wavelengths were used. Commercial control needle perforated films were used as control samples. Tests were performed in order to determine and evaluate changes in WVTR, OTR and improvement in shelf-life of mushrooms upon using laser-scored films. Any physical changes in the fruits, for e.g. softening, ripening, browning, colour loss, or microbial spoilage were also evaluated. Result - WVTR sufficiently high to remove excess moisture. OTR was sufficiently low to modify headspace gas atmosphere. The simultaneous control of OTR and WVTR was seen to slow plant tissue metabolism, slow the rate of softening and loss of texture, enzymatic browning and colour loss, and microbial spoilage. Shelf-life of mushrooms was increased by +2 days respectively. Film / Treatment Film Gauge (thickness, pm) Test Product WVTR gH2O / m2 / day OTR (cm3O2 / m2 / day) Estimated Shelf- Life Gain (Days) Commercial Control Needle Perforated 19-42 Mushrooms >500 > 1,000,000 (no modified atmosphere) 0 Pet 2.0 mm scored 42 Mushrooms 126.0 285 + 2 Pet 1.5 mm scored 42 Mushrooms 144.0 340 Pet 1.0 mm scored 42 Mushrooms 180.0 455

Claims

1. A packaging material for perishable produce comprising a polymeric or a biopolymeric film, wherein the film comprises an engineered surface topography configured to simultaneously control the oxygen transfer rate (OTR) and the water vapour transmission rate (WVTR), thereby creating a modified atmosphere within the package and extending the shelf-life of the produce contained therein.

2. A polymeric film of packaging material as claimed in claim 1, wherein the film is selected from polyethylene terephthalate (PET), polyethylene (PE), oriented polypropylene (OPP), Polybutylene Adipate Terephthalate (PBAT), or a combination thereof.

3. A biopolymeric film of packaging material as claimed in claim 1, wherein the film is selected from Polylactic acid (PLA), Polyhydroxyalkanoates (PHA), bio-based materials derived from renewable resources such as com starch, sugarcane, and wood pulp, rice waste, paddy straw or cellulose-based bioplastics, or a combination thereof4. A film of the packaging material according to claim 1, wherein the film has a thickness between about 15 pm and about 50 pm.

5. A packaging material as claimed in claim 1, wherein the engineered surface topography is formed by laser scoring.

6. A packaging material according to any preceding claim, wherein the scoring is performed using a CO2 laser or a nanosecond fibre laser.

7. A packaging material according to any preceding claim, wherein the laser scoring is applied as an inline process during film production.

8. A packaging material as claimed in claim 1, wherein the engineered surface topography is formed by embossing.

9. A packaging material according to any preceding claim, wherein the embossing is performed using a texture tools.

10. A packaging material according to any preceding claim, wherein the laser scoring or embossing forms a non-penetrating groove having a depth of less than 50% of the film’s total thickness.

11. A packaging material according to any preceding claim, wherein the marking pattern comprises one or more of: linear lines, non-continuous lines, dimples, or geometric textures.

12. A packaging material according to any preceding claim, wherein the marking pattern has a line density selected from 1.0 mm to 5.0 mm.

13. A packaging material according to any preceding claim, wherein the marked pattern is formed by an embossed roller configured to imprint a non-penetrating surface texture onto the film.

14. A packaging material according to any preceding claim, wherein the oxygen transfer rate (OTR) and water vapour transfer rate (WVTR) are selected to be optimal for the respiration characteristics of the specific produce to be packed.

15. A packaging material according to any preceding claim, wherein the film is suitable for use as a tray lidding, skillet lidding, or flow wrap.

16. A packaging material according to any preceding claim, wherein the film is suitable for packaging a food product that are respiring, moisture-sensitive, or prone to spoilage.