FLUID RETAINING SUBSTRATE
The invention concerns a substrate for increased retention capacity of fluids, ideally for use in or as part of a packaging tray, wherein said substrate comprises a plurality of wells provided therein; and a packaging tray comprising said substrate.
The invention concerns a substrate for increased retention capacity of fluids, ideally for use in or as part of a packaging tray, wherein said substrate comprises a plurality of wells provided therein; and a packaging tray comprising said substrate.
BACKGROUND OF THE INVENTIONFood chains and markets have rapidly been expanded and connected due to the globalization and economic growth. These showed the key roles of food packaging in containing, preserving, and delivering food products within the global food chains. Therefore, various packaging solutions have been developed to drive the food packaging from its passive to active role. This involves addressing the challenges of food packaging in prolonging shelf life, maintaining freshness, quality, and safety of the packaged food.
Packaging of liquid-exuding foods such fresh meats is the most crucial among food products due to their perishability and susceptibility to the microbial contamination. Besides, meat, poultry and fish naturally exude juice (exudate) during storage resulting in limited shelf life and large waste of the meat products. This exudate primarily contains sarcoplasmic proteins generated from protein denaturation in muscles during post-mortem period. The expressed exudate in meat packaging accounts for 1-3% wt. of the fresh meat piece and can rise to 10% wt. for very exudative type of meat. Meat exudate facilitates deterioration of meat quality and safety due to high water activity, hence accelerated growth of spoilage and pathogenic microorganisms. Further, the accumulated exudate may leak from the packaging trays and it is perceived as unsanitary liquid by customers. Therefore, different packaging solutions have been developed to isolate the free exudate accumulated in meat and other food packaging Plastic trays with absorbent pads placed on their floor are widely used as a soak-away for the exudate released from fresh meat, poultry, and fish. The 1 soaking pads can be in various forms, such as paper sheet, fibrous mat including cellulose fibres or hygroscopic salts (superabsorbent) in granular and fibre forms, such as polyacrylate and carboxymethyl cellulose. The meat exudate is absorbed and immobilised in the absorbent pad structure to maintain low water activity and inhibit microbial growth. However, certain materials still lead to substantial microbial growth that causes contamination and can also break up and delaminate when the absorbent layers are saturated with liquid resulting in contamination of contained meat. Further, absorbent pads with absorptive layers of tissue, paper or pulp have a limited capacity of liquid absorption and retention, or conversely when using super absorptive materials can lead to exudate draw from the produce adversely affecting produce quality and/or lead to accelerated spoiling. The absorbed drip can also be released back to the meat product, especially when the compressible pad undergoes pressure from the meat weight or packaging handling by customers.
Double-walled absorbent trays have also been devised with a cavity to trap the meat and food exudates. However, this technique fails to retain the liquid when the tray is tilted and the liquid can leak out. Although double walled trays have been developed to trap a sandwiched pad in the cavity between the walls, these pads have limited absorption capacity and the liquid can still escape from their edges. Further, this type of absorbent tray has higher cost of manufacturing.
Further, open-cell foam trays have also been used to absorb the meat exudate inside their porous structure. The polymeric foam can be used to form a single absorbent tray or absorbent pad inside a packaging tray. However, liquid absorbency of the open cells can be limited under stresses originated from product overloading. Further, liquid collected within the foam structure can lead to end of life recycling issues with that product.
Furthermore, all of the above solutions include additional materials within the packaging which has extended to the increasing concern about eco-friendly food packaging as more pressure is exerted to reduce the use of non-recyclable packaging materials, especially for polymeric materials such as those widely used in food packaging. The polymeric packaging waste was estimated about 20 million metric tons within EU in 2015.
To overcome this, recent advances in food packaging have led to the development of absorbent trays with integrated capillary features to trap the exudate under capillary forces. The trays have small floor and wall moulded features for holding the excreted exudate in food packaging. This liquid retention inside the features depends on capillary forces, which account for liquid rise on tilted surfaces or inside thin tubes in contact with a wetting liquid reservoir. However, despite their improved environmental footprint, the absorbent trays with moulded capillary features gain their exudate retention functionality for only small-sized features, with larger features losing retention capacity. Thus, such absorbent trays with capillary features can only be provided in limited sizes before leakiness occurs/retention is lost, and so only offer limited retention capacity suitable for packaging food exuding small quantities of liquid.
Accordingly, we herein disclose a substrate, and a packaging tray comprising same, that due to its nature provides for improved fluid retention by capillary action. In this manner, capillary action is retained even when using larger capillary recesses, or wells, thus increasing overall volumes of fluid that can be retained. This therefore provides for an improvement over conventional capillary recess trays/pads, and preferable recyclable alternative to other absorptive pads.
STATEMENTS OF INVENTIONAccording to a first aspect of the invention there is provided an substrate for retaining a fluid, ideally for use in or as part of a packaging tray, wherein said substrate is substantially planar and comprises a plurality of wells provided therein each having a wall and a base wherein each one of said wells has a cross-sectional shape and cross-sectional length configured to retain fluid by capillary action and further wherein the walls of said wells extend above the upper surface of said substrate forming a rim.
Reference herein to cross-sectional shape refers to the transverse, or horizontal cross-sectional shape with respect to the upper surface of the substrate.
As used herein, ‘cross-sectional length’ refers to the length of the major axis, i.e. the longest straight line that can be drawn between any two points on the periphery or boundary of a 2-dimensional shape. Thus, for a circle, cross-sectional length is equal to diameter. For irregular or elongate shapes, cross-sectional length preferably refers to both the major axis and the minor axis, i.e. the length of the longest straight line that can be drawn between any two points on the periphery or boundary whilst remaining perpendicular to the major-axis.
As used herein, substantially planar refers to a surface of two-dimensions from which the wells protrude, however, as will be appreciated by those skilled in the art includes surfaces with an appreciable thickness to permit incorporation of the wells in the surface.
As known to those skilled in the art, capillary action is the ability of a liquid to flow or retract in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. Liquid flow in capillary systems like capillary channels is controlled by integrating a capillary passive valve in the flow path of the liquid. This valve can be a sudden geometric enlargement of the capillary channel or a change in surface wettability of the internal channel walls. The introduced capillary valve can restrict the liquid flow under capillary forces. This results in a capillary pressure barrier inducing pinning effect to trap the liquid inside the capillary channel. The liquid flow will be initiated as the capillary forces are overcome by encountering external forces as in case of centrifugal or gravitational forces.
In the present context, the wells retain liquid by capillary action through generating a liquid bridge under the effect of liquid surface tension. This liquid barrier prevents the liquid drainage from the wells. Unexpectedly, considered in the context of dimensions of the wells to permit capillary action, the provision of a raised rim on the wells vastly improves liquid retention capacity of the wells considerably, even when tipped, in comparison with corresponding wells without rim.
Without wishing to be bound by theory, the raised well rim increases the opening angle of the wells relative to the substrate surface, which improves their valving pressure barrier acting on the well openings. This allows a liquid meniscus to form a more stable liquid bridge to prevent the liquid drainage from the well. Further, and advantageously when utilised in the context of a packaging tray wherein meat, for example, is placed on the substrate the provision of the rim on the wells also supports the meat in an elevated position such that instead exudate can drain into the wells and not contact the meat, which is important for preservation. In yet a further preferred embodiment, said rim has a height, as measured perpendicular to the horizontal/transverse plane of the substrate, selected from between 0.10 mm and 5.00 mm including both 0.10 mm and 5.00 mm and every 0.05 mm therebetween extending above the substrate surface. More preferably said rim has a height of about at least 0.2 mm and, in particular embodiments, the rim has a height selected from between 0.20 mm and 2.50 mm including both 0.20 mm and 2.50 mm and every 0.05 mm therebetween extending above the substrate surface. More preferably still, said rim has a height selected of at least 1.00 mm. In this preferred range, maximum retention capacity is achieved, even when the substrate is rotated upside down.
As it will be appreciated by those skilled in the art, said rim comprises an elongate structure, mirroring the well boundary and extended above the upper surface of the substrate. In a preferred embodiment, said rim has a cross-sectional width, as measured in the horizontal/transverse plane, within the range of about 0.10-1.90 mm including both 0.10 mm and 1.90 mm and all 0.01 mm therebetween, and more preferably within the range of about 0.20-1.00 mm including both 0.20 mm and 1.00 mm and all 0.01 mm therebetween. More preferably, said has a cross-sectional width within the range of about 0.20-0.60 mm including both 0.20 mm and 0.60 mm and all 0.01 mm therebetween and most preferably selected from the group comprising 0.20 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.30 mm, 0.31 mm. 0.32 mm. 0.33 mm. 0.34 mm. 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.40 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.50 mm, 0.51 mm, 0.52 mm, 0.53 mm, 0.54 mm, 0.55 mm, 0.56 mm, 0.57 mm, 0.58 mm, 0.59 mm, 0.60 mm. Most ideally, said rim comprises a tapered rim edge, essentially forming a pointed upper rim surface to achieve maximum well opening angle. In this manner, it has been found that the opening angle of the well with respect to the substrate surface is at a maximum, thus achieving highest improvement in retention capacity of the well. For example, for a well having no wall taper, the opening angle is increased from 270° upwards towards 359°.
In a preferred embodiment said wells have a diameter or maximum cross-sectional length selected within the range of about 1-15 mm including both 1 mm and 15 mm and all 0.01 mm therebetween. More preferably still, said wells have a diameter or maximum cross-sectional length selected within the range of about 6-13 mm including both 6 mm and 13 mm and all 0.01 mm therebetween. Most preferably, said wells have a diameter or maximum cross-sectional length selected from the group comprising 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm and all 0.01 mm therebetween.
In a preferred embodiment, said wells have a depth, measured from the upper surface of the substrate, selected within the range of about 1.0-10.0 mm including both 1.0 mm and 10.0 mm and all 0.01 mm depths therebetween. Most preferably, said wells have a depth within the range of about 1.0-8.0 mm including both 1.0 mm and 8.0 mm and all 0.01 mm depths therebetween and most ideally selected from the group comprising 1 mm, 2 mm, 3 mm, 4 mm, 5 mm 6 mm, 7 mm, 8 mm and all 0.01 mm therebetween.
In yet a further preferred embodiment, said wells are positioned immediately adjacent to one another. In this embodiment, each well at its closest point with the next adjacent well(s) is merely separated from one another by the rim and wall of each well. As will be appreciated, in the context of, e.g., circular wells there will be additional spacing owing to the curvature of the well. Alternatively, said wells are spaced apart from one another by an amount selected from the range of about 0.1 mm-10.0 mm including both 0.1 mm and 10.0 mm and every 0.05 mm therebetween. More preferably still, said wells are spaced apart from one another by an amount of at least 0.1 mm and more preferably between 0.5 mm-5.0 mm including both 0.5 mm and 5.0 mm and every 0.05 mm therebetween. More preferably still said wells are spaced apart between 0.5 mm-2.0 mm including both 0.5 mm and 2.0 mm and every 0.05 mm therebetween. Without wishing to be bound by theory, smaller spacing allows for more wells per unit area of substrate, which will allow more fluid to be retained which is important in the context of retaining fluid exudate from meat, for example. However, in certain embodiments, the presence of spacing between each well can help further reduce leakiness of the substrate and its ability to retain fluid; nevertheless, the spatial distance between wells has not been found to detrimentally effect retention. Accordingly, this range for separation has been found to achieve both maximum overall fluid retention volumes per unit area and high fluid retention capacity.
In a preferred embodiment said wells are of a cross-sectional shape selected from substantially circular, elliptical, triangular, cross-shaped, hexagonal, or otherwise polygonal shapes in cross-section. More preferably, said wells are of a cross-sectional shape selected from substantially circular, triangular, cross-shaped, or hexagonal shape in cross-section. Most preferably, said wells are circular or triangular shape in cross-section. As will be appreciated, where appropriate, both recti-linear shapes and round edge polygons are envisaged within the scope of the invention, with the latter having advantages in certain manufacturing processes.
Further, ideally, said wells are provided as at least one array having a two dimensional shape, a first dimension of which is aligned or staggered with a first axis of said substrate (in which it is provided) and a second dimension of which is aligned or staggered with a second axis of said substrate. As will be appreciated by those skilled in the art, this provides for wells arranged in a series of rows and columns, which may be aligned or staggered with respect to one another. The exact arrangement of which can vary and will be determined by the skilled person according to the shape and geometry of wells and having regard to requisite spacing for retention and also density of the wells on the surface (the number of which determines overall retention volume of the substrate).
In a further preferred embodiment of the invention said substrate is provided with a plurality of arrays of wells.
In a further preferred embodiment, said wells are provided without taper. In this arrangement, increased volume per well can be achieved in addition to increased capillary force. However, in alternative embodiments said wells are tapered whereby their cross-sectional length diminishes from the top of the well to the base, or vice versa. Such arrangements can be advantageous in certain situations, such as thermoforming manufacturing processes wherein the taper assists demoulding. Preferably the wells are tapered by an angle selected from the range of about 1-15° including both 1° and 15° and every 0.1° therebetween. More preferably, the wells are tapered by an angle selected from the range of about 5-15° including both 5° and 15° and every 0.1° therebetween. Most preferably, the wells are tapered by an angle selected from group comprising 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15° and every 0.1° therebetween. As will be appreciated by those skilled in the art, well wall taper is measured relative to the axis perpendicular to the well base.
In a preferred embodiment, the substrate is manufactured from, including but not limited to, a material selected from the group comprising: Polyethylene terephthalate, polyethylene, polypropylene, and polystyrene, or combinations thereof, including thermoformed or expanded polymer forms thereof. However, numerous other such materials are known in the art and can be utilised according to the invention. More preferable, said material is Polyethylene terephthalate or polyethylene.
In a further preferred embodiment said substrate is for use in, or as part of, a packaging tray such as, but not limited to food packaging trays or the like. In this preferred embodiment, as taught herein, the fluid to be retained is typically a liquid such as food produce exudate including blood, juices, water, and further comprising sarcoplasmic proteins generated from protein denaturation in muscles during post-mortem period. Typically, such fluid is defined as having a surface tension of about 30-80 mN/m, and more typically 45-75 mN/m.
In a particular, but not exclusive, embodiment of the invention said wells are provided as at least one array, wherein said array comprises circular cross-sectional wells. Preferably said wells have a cross-sectional length within the range of about 8-10 mm including both 8 mm and 10 mm and all 0.1 mm therebetween and most ideally 9 mm. More preferably still, said wells have a rim height, as measured perpendicular to the horizontal/transverse plane, of about at least 0.2 mm and more preferably about 0.2-2.0 mm including both 0.2 mm and 2 mm and all 0.01 mm therebetween, most ideally with a tapered rim edge. Alternatively or additionally, said rim has a cross-sectional width, as measured in the horizontal/transverse plane, within the range of about 0.20-1.00 mm including both 0.20 mm and 1.00 mm and all 0.01 mm therebetween. This substrate, when tested for retention, showed the greatest retention capacity compared to similar wells without presence of a rim.
In a further particular, but not exclusive, embodiment of the invention said wells are provided as at least one array, wherein said array comprises triangular cross-sectional wells. Preferably said wells have a cross-sectional length within the range of about 8-12 mm including both 8 mm and 12 mm and all 0.1 mm therebetween and most ideally 10 mm. More preferably still, said wells have a rim of height, as measured perpendicular to the horizontal/transverse plane, of about at least 0.2 mm and more preferably about 0.2-2 mm including both 0.2 mm and 2 mm and all 0.1 mm therebetween, most ideally with a tapered rim edge. Alternatively or additionally, said rim has a cross-sectional width, as measured in the horizontal/transverse plane, within the range of about 0.20-1.00 mm including both 0.20 mm and 1.00 mm and all 0.01 mm therebetween. This substrate, when tested for retention, showed the greatest retention capacity compared to similar wells without presence of a rim. Notably, whilst offering slightly less retention capacity due to a smaller volume capacity compared when compared to circular wells, due to the shape triangular shaped wells potentially offer increased packing density on the surface. Therefore, as will be appreciated, overall a greater number of triangular shaped wells can populate the same area when compared to circular wells therefore providing for an overall increased fluid retention capacity per unit area of substrate.
In a further particular, but not exclusive, embodiment of the invention said wells are provided as at least one array, wherein said array comprises cross-shaped cross-sectional wells. Preferably said wells have a cross-sectional length within the range of about 9-11 mm including both 9 mm and 11 mm and all 0.1 mm therebetween and most ideally 10.5 mm. More preferably still, said wells have a rim of height, as measured perpendicular to the horizontal/transverse plane, of about at least 0.2 mm and more preferably about 0.2-2 mm including both 0.2 mm and 2 mm and all 0.1 mm therebetween, most ideally with a tapered rim edge. Alternatively or additionally, said rim has a cross-sectional width, as measured in the horizontal/transverse plane, within the range of about 0.201.00 mm including both 0.20 mm and 1.00 mm and all 0.01 mm therebetween. This substrate, when tested for retention, showed the greatest retention capacity compared to similar wells without presence of a rim. Notably, whilst offering slightly less retention capacity due to a smaller volume capacity compared when compared to circular and triangular wells, due to the shape triangular shaped wells potentially offer increased packing density on the surface particularly when used with higher surface tension fluid.
In a further particular, but not exclusive, embodiment of the invention said wells are provided as at least one array, wherein said array comprises hexagonal cross-sectional wells. Preferably said wells have a cross-sectional length within the range of about 6-14 mm including both 6 mm and 14 mm and all 0.1 mm therebetween and more preferably 9 m-13 mm. Most ideally said wells have a cross-sectional length selected from the group comprising: 8 mm, 9 mm, 10 mm, 11 mm, 12 mm and every 0.1 mm therebetween. More preferably still, said wells have a rim of height, as measured perpendicular to the horizontal/transverse plane, of about at least 0.2 mm and more preferably about 0.2-2 mm including both 0.2 mm and 2 mm and all 0.1 mm therebetween, most ideally with a tapered rim edge. Additionally or alternatively, said rim has a cross-sectional width, as measured in the horizontal/transverse plane, within the range of about 0.20-1.00 mm including both 0.20 mm and 1.00 mm and all 0.01 mm therebetween. This substrate, when tested for retention, showed the greatest retention capacity compared to similar wells without presence of a rim. Notably, whilst offering slightly less retention capacity due to a smaller volume capacity compared when compared to circular wells, due to the shape the potentially offer increased packing density on the surface. Therefore, as will be appreciated, overall a greater number of triangular shaped wells can populate the same area when compared to circular wells therefore providing for an overall increased fluid retention capacity per unit area of substrate.
The afore arrangements, advantageously, showed considerably improved fluid retention throughout testing compared to those wells without rim. These substrates are characterised by having a common hole cross-sectional size or diameter and notably the provision of a rim, which increases the well opening angle to enhance well capillary action (and so retention capacity). Accordingly, the invention described herein is ideally characterised by at least this feature.
In arriving at the invention optimisation of shape and size of the wells, as well as their positioning with respect to one another and the configuration of the rims, was investigated to improve the fluid retention.
According a further aspect of the invention there is provided a packaging tray comprising at least one substrate according to the invention.
In a preferred embodiment, said packaging tray comprises a floor and side walls extending upwardly from said floor, wherein said floor comprises said at least one substrate.
In yet a further preferred embodiment, said at least one substrate is provided as a removable insert for positioning in the floor of said tray. As will be appreciated by those skilled in the art, in this arrangement the substrate can be used in a variety of trays or other arrangements wherein fluid exudate can be absorbed and retained. Advantageously, this permits the substrate containing the fluid exudate to be disposed of.
Alternatively, and more preferably, said substrate defines the floor, or at least a part thereof, of said tray. As will be appreciated, according to this preferred arrangement the tray is manufactured from a material wherein the floor, and optionally walls, is/are moulded to provide at least one or more integrally associated substrates as defined herein. Ideally, the walls and floor are manufactured from the same material. In this manner, the tray is formed from a single material which is moulded with fluid-holding wells according to the invention, offering increased fluid retention properties.
Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, mean “including but not limited to” and do not exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
All references, including any patent or patent application, cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. Further, no admission is made that any of the prior art constitutes part of the common general knowledge in the art.
Preferred features of each aspect of the invention may be as described in connection with any of the other aspects.
Other features of the present invention will become apparent from the following examples. Generally speaking, the invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including the accompanying claims and drawings). Thus, features, integers, characteristics, compounds or chemical moieties described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein, unless incompatible therewith.
Moreover, unless stated otherwise, any feature disclosed herein may be replaced by an alternative feature serving the same or a similar purpose.
The Invention will now be described by way of example only with reference to the Examples below and to the following Figures wherein:
With reference to
The floor 3 comprises at least one substrate 2 for retaining a fluid. The substrate 2 is substantially planar and comprises a plurality of wells 5. The wells 5 are arranged and configured to retain a fluid, such as a liquid exudate from a product packed in the tray 1.
Each well 5 comprises a base 5a and walls 5b extending from said base 5a. The walls 5b of the wells extend above the surface of the substrate 2, thereby forming a rim 5c. In an embodiment, the substrate 2 defines the floor 3, or part thereof, so that the walls 5b of the wells extend above the surface of the floor 3, thereby forming a rim 5c. Thus, the rim 5c extends above the surface of the substrate 2 or the surface of the floor 3. Preferably, each well 5 comprises a peripheral rim 5c extending around the opening of the well 5. Most preferably, the peripheral rim 5c extends completely around the opening of the well 5.
In trays and substrates comprising wells without a rim 5c, fluid retained in the well fills the well and “excess” fluid has a tendency to bulge above the opening of the well. This excess fluid is not efficiently retained by the substrate, so that the excess fluid, as well as the fluid within the well leak back into the inner space of the tray. Consequently, the food product is in contact with extrudate and its shelf life will decrease. By providing the wells 5 with a rim 5c extending above the upper surface of the substrate 2 or above the floor 3 of the tray 1, the fluid retention of the full well is improved. The pinning angle of the excess fluid is modified (in particular increased) so that the fluid is more efficiently retained by the well 5. This increase in the pinning angle results in an increase in the diameter of the rim 5c, and therefore an increase in the total capacity of the well 5.
The presence of the rim 5c also facilitate the process of manufacturing the substrate 2 or tray 1. More particularly, when the substrate 2 or tray 1 is obtained through a thermoforming process, the increased diameter improves material draw, thereby enabling the formation of deeper wells, with further increased fluid retention capacity.
As illustrated in
The tray 1 and/or substrate 2 may be formed by methods such as thermoforming or injection moulding. The tray 1 and/or substrate 2 are preferably thermorformed. Thermorforming processes may results in tray areas of differing thicknesses, with thinner (and therefore structurally weaker) areas. In order to impart strength and provide protection to these weaker areas, the tray 1 and/or substrate 2 may comprise one or more of the following features. Trays and/or substrates obtained via processes other than a thermoforming process may also comprise one or more of these features.
In an embodiment, the floor 3 of the tray 1 comprises one or more raised platforms 6. Preferably, the platforms 6 are raised above (in use) the upper surface of the floor 3 of the tray 1 (or the upper surface of the substrate 2 if comprised in a substrate 2).
The platforms 6 may be elongated in shape. In the tray 1 illustrated in
The platforms 6 are particularly advantageous, not only because they reinforce the structure of the tray 1, but also because the product (packed in the tray 1) is elevated above the floor 3 of the tray 1. The platforms 6 may be arranged and configured to provide support across the product's lower surface. This configuration keeps the product (for example a meat product) away from the released exudate, and therefore further increases the product's shelf life. In addition, this configuration permits allows drip release as the product ages, and the exudate have unrestricted access to the wells 5. Where the tray 1 is a controlled- or modified-atmosphere packaging (CAP or MAP applications), the MAP gas circulation around the product further improves shelf life and reduces meat discolouration (browning).
Similarly, an insertable substrate 2 may comprise one or more platforms 6, wherein the platforms 6 are raised above (in use) the surface of the substrate 2.
The tray 1 may comprise one or more bumpers 7. Preferably, the one or more bumpers 7 are formed adjacent or in the floor 3 of the tray 1. Preferably, the one or more bumpers 7 are formed adjacent a corner of the tray 1. The bumpers 7 provide structural protection and support to the wells 5 during transport and usage of the tray 1 (e.g. product processing and packing, retail or end user usage). For optimum protection, the bumpers 7 may be lower (in use) than the bases 5a of the wells 5. That is, the lowest point of the bumpers 7 is lower than the bases 5a of the wells 5. For example, the lowest point of the bumpers 7 may be about 1 mm lower than the bases 5a of the wells 5. Alternatively, the lowest point of the bumpers 7 and the bases 5a of the wells 5 are co-planar.
In an embodiment, the tray 1 or substrate 2 comprises a plurality of wells 5, each well 5 comprising walls 5b extending substantially symmetrically from and relative to the base 5a of the well 5. Additionally or alternatively, the tray 1 or substrate 2 comprises a plurality of wells 5′, each well 5′ comprising the walls 5b′ of a well 5′ extend in an asymmetrical manner from and relative to the base 5a′ of the well 5′. For example, one of the walls 5b′ or part of the wall 5b′ may be chamfered. In a preferred embodiment illustrated in
The side walls 4 of the tray 1 may comprise a plurality of ribs, to strengthen the structure of the tray 1.
The tray 1 may comprise one or more denesting recesses, preferably at or adjacent the corners of the tray 1. These denesting recesses may be positioned adjacent the peripheral flange of the tray 1, and/or adjacent or on the floor 3 of the tray 1.
Material & Methods
In the following testing simulated fluids of varying surface tensions was undertaken, in addition to exudate from meat (pork). However, the invention is not limited only to the use of the invention with a sputum or, indeed, a fluid sample, rather the invention may be used with any biological sample that is to be dried prior to or whilst performing FTIR.
Materials
Polyethylene terephthalate (PET) sheets with nominal thickness of 0.5 mm (Klockner Pentaplast Group, UK) were thermoformed against mould to produce capillary wells. Isopropyl alcohol (IPA) (Propan-2-ol≥99.5%, Fisher Scientific, UK) was used to clean the well samples. 4-Hydroxy-4-methyl-2-pentanone (Sigma Aldrich-boiling point: 166° C., density: 0.931 g/ml, surface tension: 32.37 mN/m) with methylene blue dye (Sigma Aldrich-M9140-25G) were used for volume measurement of well cavities. Deionised (DI) water was used as test liquid. Triton X-100 surfactant (Sigma Aldrich, UK) was used with DI water to prepare a test liquid with low surface tension of 52 mN/m.
The use of test liquids of varying surface tension values is to reflect the diversity of exudate surface tensions. Pork meat exudate was collected from packaged pork meat (Aldi, UK) and used for retention test. Red azorubine colorant-E122 (FastColours LLP, UK) was used to dye the simulant liquids for retention tests.
Design and Thermoforming of Inserts with Capillary Wells
The 3D model design of an absorbent insert with arrays of capillary wells was generated by computer-aided design (CAD) SolidWorks software. The wells had circle, triangle, and cross-sectional profiles with internal depth of 5 mm, draft angle of 10° and fillets with a radius of 0.5 mm. The opening diameters of the circular wells and opening side length of triangular wells were (7, 8, 9, 10, 11 or 12 mm). Cross-shaped wells with three different cross-sectional profiles (3×9 mm, 10.5×4 mm, 11×5 mm) were prepared. Hexagonal wells with different maximum cross-sectional length (i.e. the diagonal) of 6, 8, 10, 12, 14 or 16 mm were prepared. Wells were primarily designed with and without positive raised rims with height of 1-2 mm, with the exception of studies investigating rim height where various rim heights were explored. Varying thicknesses of well rims were investigated. The insert was configured with arrays of 8 even-spaced wells of the same diameter (circular and triangular wells) and 9 even-spaced wells (cross wells) as shown in
Volume Measurement of PET Capillary Wells
-
- Cavity volume of the wells was determined by measuring the mass of a liquid, with known density, occupying the well spaces. A low surface tension liquid (4-Hydroxy-4-methyl-2-pentanone stained with methylene blue dye) was used to give a better levelling with the well edges. The mass of the liquid occupying well cavity was measured on an analytical scale (Model: A200S, Sartorius-Instruments Ltd, UK) with a resolution of 0.0001 g. The liquid volume was then calculated by its known density as it represents the volume of the corresponding well cavity.
Preparation of Test Liquids
-
- Test liquids having a surface tension value of 72.6 or 52.3 mN/m were prepared by adding a surfactant (Triton X-100) to DI water. Surface tension of the simulant liquids was determined by pendant drop technique using (First Ten Angstroms FTA1000c) analyser. The test liquids were dyed with red azorubine colorant-E122 (FastColours LLP) to be distinguished during the liquid retention tests. Real exudate of fresh packaged pork meat (surface tension: 60.0 mN/m) was used for the retention test to compare it with the simulant liquids.
Retention test of capillary wells
-
- Liquid retention capacity of the capillary wells was evaluated for various combinations of well size and presence of raised rim by retention test under normal gravity (1g). The test included tilting the well samples for an angle of 180° after filling with test liquids. The weight of simulant liquid in full sample (8 or 9-well array) was measured before tilting. The sample was then inverted upside down for a time of 5 s. The weight of trapped liquid was then measured representing the liquid retention capacity.
Results
Geometry and Volume Capacity of Thermoformed Wells
The thermoformed PET capillary wells (circular, triangular, hexagonal and cross shapes) had a good replication of their CAD models as shown in the FIGS. (1) and (2) (hexagonal not shown). All wells had internal depth of 5 mm. The rim height was 2 mm for wells integrated with positive rim. The cavity 5 volume of the PET well was proportionate to the well size (opening dimensions) as shown in the Table (1). The wells with raised rim show no significant difference in their cavity volumes with the corresponding well without rim. However, circle-shaped wells exhibited larger volumes than the corresponding triangle-shaped wells.
Retention Capacity of Capillary Wells
Circle-Shaped WellsRetention capacity of circle-shaped well samples (8-well arrays) of each size (opening diameter: 7, 8, 9, 10, 11, 12 mm) was measured under normal gravity (1g). FIG. (3) shows a comparison between retention capacities of the circleshaped wells with and without rim using DI water (y: 72.6 mN/m), while
Triangle-Shaped Wells
-
- Well samples with triangular cross-sectional profiles exhibited high retention capacity with DI water (y: 72.6 mN/m). The well samples without rim showed full retention capacity until well with side length of 11 mm before losing their retention capacity for wells with side length of 12 mm. The wells with incorporated rim had full retention capacity even until wells with side length of 12 mm (
FIG. 6 ). For DI water (y: 52.3 mN/m), liquid retention capacity of the wells without rim dropped for wells with well side length >7 mm, while the wells with rim showed a significant increase in their retention capacity. Well samples with rim (well side length: 10 mm) showed full retention capacity (FIG. 7 ). However, the improvement in retention capacity of the wells with pork exudate due to the raised rim was demonstrated for wells with side length of 11 mm and 12 mm (FIG. 8 ).
- Well samples with triangular cross-sectional profiles exhibited high retention capacity with DI water (y: 72.6 mN/m). The well samples without rim showed full retention capacity until well with side length of 11 mm before losing their retention capacity for wells with side length of 12 mm. The wells with incorporated rim had full retention capacity even until wells with side length of 12 mm (
Cross-Shaped Wells
-
- All wells samples (all dimensions) with DI water (y: 72.6 mN/m) showed full retention capacity with and without raised rim (
FIG. 9 ). On the other hand, lower surface tension liquid, such as DI water (y: 52.3 mN/m) or pork exudate (y: 60.0 mN/m) resulted in lower retention capacity of the well samples with well dimensions of 10.5 mm×4 mm and 11 mm×5 mm. Well samples with incorporated rim showed an enhancement in their liquid retention capacity for both test liquids, while no significant increase was found for the wells with dimensions of 11 mm×5 mm (FIGS. 10 and 11 ).
- All wells samples (all dimensions) with DI water (y: 72.6 mN/m) showed full retention capacity with and without raised rim (
Hexagonal-Shaped Wells
-
- Well samples with hexagonal cross-sectional profiles exhibited high retention capacity with DI water (y: 72.6 mN/m). The well samples without rim showed full retention capacity until well with maximal cross-sectional length (long diagonal length) of 10 mm before beginning to lose their retention capacity, with wells with a maximal cross-sectional length of 12 mm losing retention capacity. The wells with incorporated rim had full retention capacity even until wells with side length of 12 mm (
FIG. 14 ). For DI water (y: 52.3 mN/m) and pork exudate (y: 60.0 mN/m), liquid retention capacity of the wells without rim dropped for wells with maximal cross-sectional length well side length >8 mm, while the wells with rim showed a significant increase in their retention capacity. Well samples with rim (well side length: 10 mm) showed full retention capacity (FIGS. 15-16 ).
- Well samples with hexagonal cross-sectional profiles exhibited high retention capacity with DI water (y: 72.6 mN/m). The well samples without rim showed full retention capacity until well with maximal cross-sectional length (long diagonal length) of 10 mm before beginning to lose their retention capacity, with wells with a maximal cross-sectional length of 12 mm losing retention capacity. The wells with incorporated rim had full retention capacity even until wells with side length of 12 mm (
Rim Height and Spacing on Fluid Retention Capacity
-
FIGS. 12 and 13 shows the effect of rim height and spacing on liquid retention capacity of triangle-shaped well samples with DI water (y: 52.3 mN/m) respectively. The rim height had no effect on the liquid retention; however, the presence of the rim did improve the retention. The spacing between the raised rims had a small effect on decreasing the retention capacity of wells with joint rim (i.e. no spacing distance between each wells) with DI water (y: 52.3 mN/m). However, for higher surface tensions and alternative cross-sectional shapes spacing may play a role.- Accordingly, the effect of rim height and spacing was investigated for circular and hexagonal wells (
FIGS. 17-20 ).FIGS. 17 and 18 show the effect of differing rim height on fluid retention of fluids of varying surface tension. The presence of a rim improved fluid retention for both well types, with at least a 0.2 mm rim height found to significantly improve fluid retention for both cross-sectional shapes and when using the various simulant and pork exudate fluids, with a maximum retention achieved up to 1 mm. In contrast, rim spacing was found to have a negligible effect (FIGS. 19 and 20 ) on fluid retention.
Rim Thickness on Fluid Retention Capacity
-
FIGS. 21 and 22 shows the effect of rim thickness upon liquid retention capacity of circular and hexagonal wells, respectively. Rim thickness was measured at the lower part of the rim adjacent the substrate surface; in all cases rims tapered to a point. For both circular and hexagonal wells, a thin tapered rim of at least 0.2 mm thickness lead to maximum fluid retention capacity. This was observed up to 1 mm thickness. However, when the thickness of the rim exceeded 1 mm, fluid retention capacity was lost in both cases, indicating that a substantially thin and tapered rim is important to maximize capillary retention effect.
Packaging trays with capillary features capable of trapping and retaining larger quantities of liquids can be innovative solution for exudate isolation within meat packaging. This liquid retention inside the features is based on the effect of capillary forces of capillary recesses, such as wells, which hold liquids through generating a liquid bridge under the effect of liquid surface tension. This liquid barrier prevents the liquid drainage from the well cavities. The liquid undergoes a hydrodynamic pressure encountered by atmospheric pressure when full wells are turned upside down. The liquid is maintained trapped within the wells by pressure difference (atmospheric pressure is higher than hydrodynamic pressure) when the liquid meniscus can form a stable liquid bridge. This was demonstrated for small-sized wells. However, the liquid meniscus becomes unstable for larger wells allowing air to enter the well cavity, and therefore losing the retention capacity. Therefore, such arrangements are limited in their retention capacity especially such as for use in packaging trays.
We herein disclose a substrate having features or recesses/wells configured for increased liquid retention, suitable for use in packaging trays, by improving their liquid pinning effect. In this work, wells with varying sizes and geometries were used as exudate-holding wells with and without raised rims. The retention test of the wells was performed with a test liquid used as an exudate simulant of the meat products. Liquid retention capacity of the wells with raised rims was compared with the corresponding wells with no rims, also considering their size and shape.
The presence of raised rim on the wells improves valving and pinning effect of the well openings. In addition, the thickness of rim was found to be a contributory factor. The well rim increases the opening angle of the well, relative to the surface of the surrounding substrate, which improves their valving pressure barrier acting on the well openings. This allows liquid meniscus to form a more stable liquid bridge to prevent the liquid drainage. Therefore, the liquid retention capacity of larger wells with raised rim considerably increased in comparison with corresponding wells without rim. This has improved utility in applications, such as packaging trays for produce, where passive liquid retention is required with enhanced liquid retaining capacity.
Claims
1. A substrate for retaining a fluid wherein said substrate is substantially planar and comprises a plurality of wells provided therein each having walls and a base wherein each one of said wells has a cross-sectional shape and cross-sectional length configured to retain fluid by capillary action and further wherein the walls of said wells extend above the upper surface of said substrate forming a rim.
2. The substrate according to claim 1 wherein the rim has a height, as measured perpendicular to the horizontal/transverse plane, of about at least 0.10 mm, extending above the substrate surface.
3. The substrate according to claim 2 wherein the rim has a height, as measured perpendicular to the horizontal/transverse plane, of at least 0.2 mm extending above the substrate surface.
4. The substrate according to any preceding claim wherein the rim comprises an elongate structure, mirroring the well boundary and extended above the upper surface of the substrate.
5. The substrate according to claim 4 wherein the rim comprises a tapered rim edge.
6. The substrate according to any preceding claim wherein said rim has a cross-sectional width, as measured in the horizontal/transverse plane, within the range of about 0.10-1.90 mm including both 0.10 mm and 1.90 mm and all 0.01 mm therebetween.
7. The substrate according to any preceding claim wherein the wells have a diameter or maximum cross-sectional length selected within the range of about 1-15 mm including both 1 mm and 15 mm and all 0.01 mm therebetween.
8. The substrate according to claim 7 wherein the wells have a diameter or maximum cross-sectional length selected within the range of about 6-13 mm including both 6 mm and 13 mm and all 0.01 mm therebetween.
9. The substrate according to claim 8 wherein the wells have a diameter or maximum cross-sectional length selected from the group comprising 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm and all 0.01 mm therebetween.
10. The substrate according to any preceding claim wherein the wells have a depth, measured from the upper surface of the substrate, selected within the range of about 1.0-10.0 mm including both 1.0 mm and 10.0 mm and all 0.01 mm depths therebetween.
11. The substrate according to any preceding claim wherein the wells are positioned immediately adjacent to one another.
12. The substrate according to any one of claims 1-10 wherein the wells are spaced apart from one another by an amount of about at least 0.1 mm.
13. The substrate according to claim 12 wherein the wells are spaced apart from one another by an amount between 0.5 mm-2.0 mm including both 0.5 mm and 2.0 mm and every 0.05 mm therebetween.
14. The substrate according to any preceding claim wherein the wells are of a cross-sectional shape selected from substantially circular, elliptical, triangular, cross-shaped, hexagonal, or otherwise polygonal shapes in cross-section.
15. The substrate according to claim 14 wherein said wells are of a crosssectional shape selected from substantially circular, triangular, crossshaped, or hexagonal shape in cross-section.
16. The substrate according to any preceding claim wherein the wells are provided as at least one array having a two dimensional shape, a first dimension of which is aligned or staggered with a first axis of said substrate (in which it is provided) and a second dimension of which is aligned or staggered with a second axis of said substrate.
17. The substrate according to claim 16 wherein the substrate is provided with a plurality of arrays of wells.
18. The substrate according to any preceding claim wherein the wells are tapered whereby their cross-sectional length diminishes from the top of the well to the base, or vice versa.
19. The substrate according to claim 18 wherein the wells are tapered by an angle selected from the range of about 1-15° including both 1° and 15° and every 0.1° therebetween.
20. The substrate according to claim 19 wherein the wells are tapered by an angle selected from the range of about 5-15° including both 5° and 15° and every 0.1° therebetween.
21. The substrate according to any preceding claim wherein the substrate is manufactured from a material selected from the group comprising: polyethylene terephthalate, polyethylene, polypropylene, and polystyrene, or combinations thereof, including thermoformed or expanded polymer forms thereof.
22. The substrate according to any preceding claim wherein the wells are provided as at least one array, wherein said array comprises circular cross-sectional wells having a cross-sectional length within the range of about 8-10 mm including both 8 mm and 10 mm and all 0.1 mm therebetween.
23. The substrate according to any one of claims 1-21 wherein the wells are provided as at least one array, wherein said array comprises triangular cross-sectional wells having a cross-sectional length within the range of about 8-12 mm including both 8 mm and 12 mm and all 0.1 mm therebetween.
24. The substrate according to any one of claims 1-21 wherein the wells are provided as at least one array, wherein said array comprises hexagonal cross-sectional wells having a cross-sectional length within the range of about 9-13 mm including both 9 mm and 13 mm and all 0.1 mm therebetween.
25. The substrate according to any one of claims 1-21 wherein the wells are provided as at least one array, wherein said array comprises crossshaped cross-sectional wells having a cross-sectional length within the range of about 9-11 mm including both 9 mm and 11 mm and all 0.1 mm therebetween.
26. The substrate according to any one of claims 22-25 wherein the wells have a rim of height of about at least 0.2 mm.
27. The substrate according to any one of claims 22-26 wherein the wells comprise a tapered rim edge.
28. The substrate according to any one of claims 22-27 said rim has a cross-sectional width, as measured in the horizontal/transverse plane, within the range of about 0.20-1.00 mm including both 0.20 mm and 1.00 mm and all 0.01 mm therebetween.
29. A packaging tray comprising at least one substrate according to any one of claims 1-28.
30. The packaging tray according to claim 29 wherein the packaging tray comprises a floor and side walls extending upwardly from said floor, wherein said floor comprises said at least one substrate.
31. The packaging tray according to claim 30 wherein the at least one substrate is provided as a removable insert for positioning in the floor of said tray.
32. The packaging tray according to any one of claims 29-31 wherein the at least one substrate defines the floor, or part thereof, of said tray.
33. The packaging tray according to claim 32 wherein tray is manufactured from a material wherein the floor, is/are molded to provide at least one or more integrally associated substrate(s) according to any one or more of claims 1-28.
34. The packaging tray according to any one of claims 29 to 33, further comprising one or more raised platforms.
35. The packaging tray according to any one of claims 29 to 34, further comprising one or more bumpers.
36. The packaging tray according to any one of claims 29 to 34, further comprising a plurality of wells having a chamfered wall.
37. A process for manufacturing a substrate according to any one of claims 1 to 28 or a tray according to any one of claims 29 to 36, comprising the step of thermoforming a sheet of material into a substrate or a tray.
Type: Application
Filed: Sep 9, 2021
Publication Date: Oct 12, 2023
Inventors: Craig HARDWICK (Wakefield, West Yorkshire), Tom HIRST (Huddersfield, Yorkshire), Alaa ALAIZOKI (Manselton, Swansea), Davide DEGANELLO (Swansea)
Application Number: 18/025,118
