FLUID RETAINING SUBSTRATE

Abstract

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.

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.

Description

[0042] FIG. 1. 3D models of the insert with capillary wells (a) circular, (b) circular with raised rim, (c) triangular, (d) triangular with raised rim, (e) cross, (f) cross with raised rim.

[0043] FIG. 2. Thermoformed PET insert with capillary wells, (a) circular, (b) circular with raised rim, (c) triangular, (d) triangular with raised rim.

[0044] FIG. 3. Retention capacity of circle-shaped well samples (8-well arrays) with DI water (y: 72.6 mN/m) with and without rim.

[0045] FIG. 4. Retention capacity of circle-shaped well samples (8-well arrays) with DI water (y: 52.3 mN/m) with and without rim.

[0046] FIG. 5. Retention capacity of circle-shaped well samples (8-well arrays) with pork exudate (y: 60.0 mN/m) with and without rim.

[0047] FIG. 6. Retention capacity of triangle-shaped well samples (8-well arrays) with DI water (y: 72.6 mN/m) with and without rim.

[0048] FIG. 7. Retention capacity of triangle-shaped well samples (8-well arrays) with DI water (y: 52.3 mN/m) with and without rim.

[0049] FIG. 8. Retention capacity of triangle-shaped well samples (8-well arrays) with pork exudate (y: 60.0 mN/m) with and without rim.

[0050] FIG. 9. Retention capacity of cross-shaped well samples (9-well arrays) of different sizes with and without rim with DI water (y: 72.6 mN/m).

[0051] FIG. 10. Retention capacity of cross-shaped well samples (9-well arrays) of different sizes with and without rim with DI water (y: 52.3 mN/m).

[0052] FIG. 11. Retention capacity of cross-shaped well samples (9-well arrays) of different sizes with and without rim with pork exudate (y: 60.0 mN/m).

[0053] FIG. 12. Retention capacity of triangular well samples (15-well arrays) (side length: 10 mm) with different heights of raised rims.

[0054] FIG. 13. Retention capacity of triangular well samples (15-well arrays) (side length: 10 mm, raised rim: 1 mm) with different spacing distances between the wells.

[0055] FIG. 14. Retention capacity of hexagon-shaped well samples (8-well arrays) with DI water (y: 72.6 mN/m) with and without rim.

[0056] FIG. 15. Retention capacity of hexagon-shaped well samples (8-well arrays) with DI water (y: 52.3 mN/m) with and without rim.

[0057] FIG. 16. Retention capacity of hexagon-shaped well samples (8-well arrays) with pork exudate (y: 60.0 mN/m) with and without rim.

[0058] FIG. 17. Retention capacity of circular well samples (8-well arrays) (diameter: 9 mm) with different heights of raised rims.

[0059] FIG. 18. Retention capacity of hexagonal well samples (8-well arrays) (long diagonal: 10 mm) with different heights of raised rims.

[0060] FIG. 19. Retention capacity of circular well samples (8-well arrays) (diameter: 9 mm) with different spacing distances between the wells.

[0061] FIG. 20. Retention capacity of hexagonal well samples (8-well arrays) (long diagonal: 10 mm) with different spacing distances between the wells.

[0062] FIG. 21. Retention capacity of circular well samples (8-well arrays) (diameter: 9 mm) with different thicknesses of well rims.

[0063] FIG. 22. Retention capacity of hexagonal well samples (8-well arrays) (long diagonal: 10 mm) with different thicknesses of well rims.

[0064] FIG. 23. Packaging tray according to the present invention comprising a substrate for retaining a fluid.

[0065] FIG. 24. Bottom view of a substrate according to the present invention. Table 1. Cavity volume of the capillary PET well.

[0066] With reference to FIG. 23, there is illustrated a packaging tray 1 according to the present invention. The tray 1 comprises a floor 3 and side walls 4 extending upwardly (in use) from said floor 3.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] As illustrated in FIG. 23, the base 5a of the well 5 is positioned below (in use) the floor 3 of the tray 1, and the rim 5c of the well 5 extends above (in use) the floor of the tray 1.

[0072] 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.

[0073] 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).

[0074] The platforms 6 may be elongated in shape. In the tray 1 illustrated in FIG. 23, the tray 1 comprises a plurality of substrates 2a, 2b, 2c, 2d. Adjacent substrates (for example 2a and 2b, 2b and 2c, 2c and 2d) may be separated by one or more raised platforms 6a. The platforms 6 may have a different shape, for example, the platforms 6 may have substantially the same overall shape as the wells 5. In FIG. 23, the tray 1 comprises wells 5 with a substantially hexagonal openings, and platforms 6b are inverted wells with a substantially hexagonal base and openings.

[0075] 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).

[0076] 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.

[0077] 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.

[0078] 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 FIG. 24, the tray 1 or substrate 3 comprises a first plurality of wells 5 with symmetrical walls and a second plurality of wells 5′ with chamfered or asymmetrical walls. The chamfered wells 5′ are preferably positioned, partly or completely, along the outer edge of the substrate 2. The chamfered wall 5′ is preferably facing outwards from the substrate 2. The configuration and positioning of the wells 5′ impart increased strength and protection to the wells and reduce the risk of damage.

[0079] The side walls 4 of the tray 1 may comprise a plurality of ribs, to strengthen the structure of the tray 1.

[0080] 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.

[0081] Material & Methods

[0082] 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.

[0083] Materials

[0084] 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.

[0085] 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.

[0086] Design and Thermoforming of Inserts with Capillary Wells

[0087] 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 FIG. 1. The mould designing and thermoforming process to produce PET replicates of the insert with capillary wells were carried out in Klockner Pentaplast Company, UK.

[0088] Volume Measurement of PET Capillary Wells [0089] 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.

[0090] Preparation of Test Liquids [0091] 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.

[0092] Retention test of capillary wells [0093] 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.

[0094] Results

[0095] Geometry and Volume Capacity of Thermoformed Wells

[0096] 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.

TABLE-US-00001 TABLE 1 Table 1. Circle-shaped wells Triangle-shaped wells Peripheral Volume (ml) ± SD Peripheral Side Volume (ml) ± SD Diameter No Positive Length No Positive (mm) Rim Rim (mm) Rim Rim 7 0.151 ± 0.148 ± 7 0.048 ± 0.047 ± 0.003 0.003 0.001 0.002 8 0.208 ± 0.202 ± 8 0.081 ± 0.081 ± 0.002 0.002 0.001 0.001 9 0.266 ± 0.262 ± 9 0.112 ± 0.115 ± 0.002 0.003 0.001 0.001 10 0.331 ± 0.329 ± 10 0.153 ± 0.153 ± 0.001 0.009 0.002 0.001 11 0.412 ± 0.409 ± 11 0.188 ± 0.188 ± 0.002 0.003 0.001 0.001 12 0.485 ± 0.478 ± 12 0.235 ± 0.236 ± 0.004 0.011 0.001 0.001

[0097] Retention Capacity of Capillary Wells

Circle-Shaped Wells

[0098] Retention 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 FIG. 20 (4) shows comparison of their retention capacity using DI water with lower surface tension (y: 52.3 mN/m). For circular wells with DI water (y: 72.6 mN/m), the wells without rim were able to fully retain the water until the well with diameter of 9 mm, while the wells with rim fully retain the water until well diameter of 10 mm. Further increase in the well diameters caused a dramatic drop in the liquid retention capacity. For circular wells with DI water (y: 52.3 mN/m), the wells without rim were only able to fully retain the test liquid for well diameter of 7 mm and the retention capacity decreased with well diameter. However, the wells with raised rim showed a substantial increase in their retention capacity in comparison with wells without rim. This was demonstrated in the full retention capacity of the wells (diameter: 9 mm) with rim to fully retain the test liquid. This corresponded to an increase in the retention capacity of well samples (diameter 9 mm) from 0.710 g (wells without rim) to 2.023 g (wells with rim). A comparable increase in the retention capacity of the wells (diameter: 9 mm) with pork exudate was sown in the FIG. (5). The raised rim introduced to the PET wells showed considerable improvement in their liquid retention capacity. The increased retention capacity of well samples with rim was notably magnified with the increase in surface tension value of the test liquid.

[0099] Triangle-Shaped Wells [0100] 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).

[0101] Cross-Shaped Wells [0102] 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).

[0103] Hexagonal-Shaped Wells [0104] 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).

[0105] Rim Height and Spacing on Fluid Retention Capacity [0106] 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. [0107] 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.

[0108] Rim Thickness on Fluid Retention Capacity [0109] 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.

SUMMARY

[0110] 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.

[0111] 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.

[0112] 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.