GB2453590A

GB2453590A - Packaging tray with lid having apertures

Info

Publication number: GB2453590A
Application number: GB0720002A
Authority: GB
Inventors: Mark Tollman
Original assignee: Sharp Interpack Ltd
Current assignee: Sharp Interpack Ltd
Priority date: 2007-10-12
Filing date: 2007-10-12
Publication date: 2009-04-15
Also published as: GB0720002D0; WO2009047539A1

Abstract

The present invention is concerned with improved packaging, particularly for fruits and vegetables and other plant products which undergo a ripening process and are liable to rot or otherwise go off, with packaging containing same, and with methods of packaging. A method of packaging fruit or vegetables comprises a tray having a base and at least one wall, and a lid defining at least one opening. The at least openings may be provided in the base of the tray and may be covered by seal means to restrict the flow of gasses.

Description

Packaging The present invention is concerned with improved packaging, particularly for fruits and vegetables and other plant products which undergo a ripening process and are liable to rot, with packaging containing same, and with methods of packaging.

Certain fresh produce such as fruit and vegetables will ripen whilst in their packaged state, with the production and release of ethylene and carbon dioxide, and are liable to rot. Ethylene acts as a ripening signal to trigger ripening (or further ripening and eventual senescence), and can thus shorten the durability of fresh produce. Carbon dioxide causes, amongst other things, unwanted fermentation processes and thus also causes shortened durability.

It is thus desirable to inhibit the generation of a modified atmosphere inside of packaging containing fresh produce in order to enhance durability. In particular, it is known that it can be desirable to retain a Continuous oxygen level and to have less than 5% ethylene and carbon dioxide.

It is well known in the art to provide packaging for fruits and vegetables which is designed to improve the shelf-life of packages containing such fruit and vegetables. For example, US 2652335 discloses packaging for fruit and vegetables with spaced ventilation holes in its sidewalis and endwalls. This is further exemplified in the packaging used by modern-day supermarkets for fruit and vegetables, which packaging will frequently have holes defined in a top or sides of the packaging.

Relevant prior art includes DEl020060l7887IEPl7l4885, which discloses a packaging machine in which packaging having a base and side walls defining a trough and containing fresh produce is sealed with a perforated film lid. Other packaging is well known, for example in the form of a tray or punnet which is provided with a lid having perforations several millimetres in diameter.

Such prior art packaging with large (herein "macroscopic") perforations allows for the escape of moisture and for the large-scale ventilation of gases inside the packaging to the atmosphere (and vice versa) and thus e.g. the removal of some ethylene during ripening. However, none of the prior art packaging provides any kind of a solution which is tailored to the specific fruit or vegetable which is contained within the packaging.

The present inventors have found that the shelf-life of fruit and vegetables which undergo ripening and are liable to rot can be substantially enhanced by the use of specific numbers and sizes of openings in the packaging. The location of the openings can further enhance shelf-life. In particular, it has been found that a specific arrangement of perforations in packaging can provide for a substantial increase in the shelf-life of strawberries.

According to a first aspect of the present invention there is provided packaging comprising: (i) a tray comprising a base and at least one wall; and (ii) a lid; said lid defining at least one opening, each at least one opening having a surface area of between 0.00157mm2 and 0.00471mm2.

Examples of trays of the present invention include containers, trays and punnets that have a base and at least one wall.

Preferably, the tray is manufactured from a rigid or semi-rigid plastic, particularly a petrochemical-(preferably petroleum oil) based plastic or a biopolymer such as corn starch or cellulose or derived from vegetable oils. Alternatively, moulded cardboards can be used to fabricate the tray, and such cardboards can include a plastic barrier layer.

Importantly, in all embodiments, the tray provides a barrier to limit gas flow across the tray. Preferable plastics include polyester (PET), polypropylene and polyvinylchloride (PVC).

A wide range of shapes of tray are suitable for use in the present invention, and include circular, square and rectangular trays. Preferably, said at least one wall comprises side and end walls.

Preferably, said lid is attached to said tray. Thus, a packaging volume is defined.

In certain embodiments, the at least one opening has an elliptical shape. In other embodiments, the at least one opening has a circular shape. Alternative shapes may also be used. For example, the at least one opening may be triangular, square, pentagonal, hexagonal, septagonal or octagonal.

The surface area referred to above is the cross-sectional area of the at least one opening defined by the lid.

Preferably, the surface area of each at least one opening is between 0.00188mm2 and 0.00440mm2, 0.00220mm2 and 0.00408mm2, 0.00236mm2 and 0.00393mm2, 0.00251mm2 and 0.00377mm2, 0.00283mm2 and 0.00346mm2, or 0.00298mm2 and 0.00330mm2. Preferably, the surface area of each at least one opening is about 0.00314mm2 Preferably, each at least one opening in the lid has permeability values of between 100 ml 02/hole.day.bar and 75 ml C02/hole.day.bar, and 300 ml O2fhole.day.bar and 225 ml C02/hole.day.bar. More preferably, each at least one opening in the lid has permeability values of between 120 ml O2fhole.day.bar and 90 ml C02/hole.day.bar, and 280 ml O2fhole.day.bar and 210 ml C02/hole.day.bar. More preferably, each at least one opening in the lid has permeability values of between 140 ml 02/hole.day.bar and 105 ml C02/hole.day.bar, and 260 ml 02/hole.day.bar and 195 ml CO2fhole.day.bar. More preferably, each at least one opening in the lid has permeability values of between 160 ml O2fhole.day.bar and 120 ml CO2Ihole.day.bar, and 240 ml 02/hole.day.bar and 180 ml C02/hole.day.bar. More preferably, each at least one opening in the lid has permeability values of between 180 ml 02/hole.day.bar and 135 ml C02/hole.day.bar, and 220 ml 02/hole.day.bar and 165 ml C02/ho!e.day.bar. More preferably, each at least one opening in the lid has permeability values of about 200 ml 02/hole.day.bar and 150 ml CO2fhole.day.bar Preferably, between 1 and 19 openings are provided. More preferably, 12-19, 13-18, 14- 17 or 15-16 openings are provided. More preferably, 2-18, 3-17, 4-16, 5-15, 6-14, 7-13, 8-12 or 9-1 1 openings are provided.

Preferably, the at least one opening is in communication with the packaging volume, i.e. gas flow from the packaging volume to the exterior of the packaging occurs through the at least one opening.

In certain embodiments, the lid is made from a rigid or semi-rigid material, for example a plastic. In other embodiments, the lid is made from a flexible material such as a plastic film. Preferably, the lid is made from a PET plastic.

In certain embodiments, the lid is a film lid sealed to the tray. In other embodiments, the lid can be in-use detached from and re-attached to the tray.

Methods of manufacture of packaging and of making openings are well known in the art and are within the capabilities of a person of ordinary skill in the art.

Preferably, the packaging is dimensioned to hold 200-l000g of fruit, more preferably 227-904g, 250-750g, 400-750g, more preferably about 450, 454 or 500g of fruit or vegetables which undergo a ripening process and which are liable to rot.

Also provided according to the present invention is a packaging according to the present invention containing within it fruit or vegetables which undergo a ripening process and which are liable to rot. The packaging can similarly contain other plant material which undergoes a ripening process and which is liable to rot.

Preferably, the packaging contains strawberries.

Preferably the packaging containing fruit or vegetables does not contain a preservative gas. As is detailed in the experiments below, such a packaging containing fruit or vegetables and not containing a preservative gas shows substantial improvements in shelf-life.

Preservative gases include carbon dioxide, nitrogen, oxygen as well as gases such as nitrogen dioxide, sulphur dioxide, and argon. Their use is well known in the art for preserving fruit and vegetables.

As above, in certain embodiments the packaging containing fruit or vegetables does not contain a preservative gas. However, in other embodiments where the packaging containing fruit or vegetables is kept at a low temperature (as detailed below), the packaging may contain a preservative gas. in particular, the packaging may contain an atmosphere enriched in carbon dioxide and/or depleted in oxygen. Preferably, the atmosphere is enriched in carbon dioxide and depleted in oxygen. Preferably, the atmosphere contains no greater than 20, 19, 18, 17, 16, 15, 14, 13, 12, Il, 10, 9, 8, 7, 6 or 5% 02. Preferably, the atmosphere contains at least 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10% CO2. More preferably, the atmosphere comprises about 5% 02 and about 10% Co2.

Such packaging containing fruit or vegetables and a preservative gas is preferably maintained at a temperature of no more than 11 °C, preferably no more than 10, 9, 8, 7, 6, 5, 4, 3 or 2 °C.

Also provided according to the present invention is method of packaging fruit or vegetables which undergo a ripening process and which are liable to rot, comprising the steps of: (i) placing said fruit or vegetables in a packaging comprising a tray comprising a base and at least one wall; and (ii) applying a lid to said tray; said tray and lid defining a packaging, said lid defining at least one opening, each at least one opening having a surface area of between 0.00157mm2 and 0.00471mm2.

As noted above, the present invention and this method is also equally applicable to other plant material which undergoes a ripening process and which is liable to rot.

The method may comprise the step of defining at least one opening in a lid material, each at least one opening having a surface area of between 0.00157mm2 and 0.00471mm2. Preferably, each at least one opening is defined by a needle. More preferably, each at least one opening is defined by a needle on a rotating wheel, the wheel moving relative to the lid material.

As detailed below, the openings of the lids of the present invention are found to be best made using a rolling wheel having needles extending from its surface, the lid moving relative to the needles. Examination of the openings so made shows that they have a generally elliptical shape, and that the dimensions of the openings so made are highly repeatable and generally uniform, and that in use they allow for a repeatable extension of shelf-life of packaged fruit or vegetables which undergo a ripening process and are liable to rot, as detailed below.

Experiments have also been undertaken using a laser perforation device and these show that the perforations so created in the lid have a "ripped" effect and are not uniform in their size or shape and that such a lid was not able to provide an equivalent extension in shelf-life as that achieved with the needle perforation.

Preferably, said tray and said lid are packaging according to the present invention.

Preferably, the method is a method of prolonging the shelf-life of said fruit or

vegetables.

Preferably, said packaged fruit or vegetables are maintained at a temperature of no more than 18 °C. Preferably, said packaged fruit or vegetables are maintained at a temperature ofno more than 12, 11, 10, 9, 8, 7,6, 5,4, 3 or 2°C.

As discussed above, in certain embodiments, the method does not include the step of introducing a preservative gas into said packaging containing said fruit or vegetables.

This is particularly desirable since such manufacturing methods are simpler and more convenient than methods which require that the packaging volume (i.e. the volume t I defined between the tray and lid) is flushed with a preservative gas. The provision of a conventional atmosphere in the packaging volume is also generally more attractive to consumers than the provision of an atmosphere which comprises a preservative gas.

In other embodiments, the method includes the additional step of introducing a preservative gas into the packaging containing the fruit or vegetables. In such embodiments, said packaged fruit or vegetables are preferably maintained at a temperature of no more than 11, 10, 9, 8, 7, 6, 5, 4, 3 or 2 °C.

As detailed below, it has been found that the provision of a preservative atmosphere in the packaging of the present invention when the packaged fruit or vegetables are kept at a low temperature shows that a synergistic enhancement in shelf-life can be achieved beyond that which would otherwise be expected from the low temperature or the use of a preservative gas alone.

In another aspect of the present invention, there is provided packaging containing fruit or vegetables which undergo a ripening process and are liable to rot, said packaging comprising: (i) a tray comprising a base and at least one wall; and (ii) a lid; said lid defining at least one opening, at least one opening being defined in said base and being covered with seal means which restricts the flow of gases through said opening in said base.

Fruit and vegetables are often grown in polypropylene tunnels, which generally means that even whilst it is raining, picked produce is not covered in rain and can thus be conveniently packaged in a dry state. However, polypropylene tunnels and suchlike are not used everywhere, and produce is also frequently picked from open fields where it can be rained on. Thus, in such situations the picked produce can be wet.

When such wet produce (fruit or vegetables) is packaged in the wet state in conventional packaging, the water contained in the packaging can have an adverse effect upon shelf-life. This is particularly so where the fruit or vegetables undergo a ripening process and are liable to rot.

As is detailed above with regard to the first aspect of the present invention, the shelf-life of fruit and vegetables which undergo a ripening process and are liable to rot can be enhanced by controlling the atmosphere in the packaging by the provision of openings in the lid. However, such openings clearly cannot assist in the problems resulting from having water in the packaging.

Thus, with the second aspect of the present invention, wet fruit or vegetables can be placed in the tray (without the seal means covering the at least one hole in the base) and water allowed to drain from them and Out of the tray. The lid can then be applied to the tray, and the seal means applied to the at least one opening in the base. Thus, the fruit or vegetables can be picked and allowed to drain, reducing the problems resulting from water in the packaging, whilst at the same time the final packaging including the lid and seal means allows for the control of the atmosphere in the volume defined by the packaging (the "packaging volume') and the shelf-life of the fruit or vegetables can be extended.

Preferably, the at least one opening in the base is dimensioned to allow the flow of water through it. Preferably the at least one opening in the base has a diameter of between 4mm and 12mm, more preferably 5-1 1mm, 6-10mm, or 7-9mm. More preferably, the at least one opening in the base has a diameter of about 8mm. More preferably still, the at least one opening in the base is a single opening with a diameter ofabout8mm.

A wide range of seal means are suitable for use and include conventional sticky labels applied to packaging. Thus, after the fruit or vegetables has been placed in the tray and a suitable time has elapsed to allow for draining of any water from the tray through the at least one opening in the base, an adhesive label can be applied over the at least one opening in the base.

In certain embodiments, seal means incorporate materials which hinder gas flow. For example, a plastic layer can be provided in the seal means.

Preferably, each at least one opening in the lid has a surface area of between 0.00157mm2 and 0.00471mm2.

Also provided according to the present invention is a method of packaging fruit or vegetables which undergo a ripening process and which are liable to rot, comprising the steps of: (i) placing said fruit or vegetables in a packaging comprising a tray comprising a base and at least one wall, at least one opening being defined in said base; and (ii) applying a lid to said tray, said lid defining at least one opening, and covering said at least one opening in said base with seal means which restricts the flow of gases through said opening in said base.

Preferably, the method additionally comprises the step of allowing any water in said tray to drain through said at least one opening in said base prior to applying said seal means.

The present invention will be further apparent from the following examples with reference to the accompanying figures, which show by way of example only forms of packaging of fruit and vegetables.

Of the Figures: Figure 1 shows an applied classification scheme for strawberry fruit decay; Figure 2 shows an applied classification scheme for the freshness of calyxes; Figure 3 shows the development of the gas composition of the packaging headspaces at 18 °C; Figure 4 shows development of the gas composition of the packaging headspaces at 12 °C; Figure 5 shows an overall comparison between three types of packaging (top -MV 18/0.7, middle -reference, bottom -MV 2x14/0.5) at 18 °C after 6 days (left) and at 12 °C after 12 days (right); Figure 6 shows strawberries that have packed in the 2x14/0.5 top-seal package after 12 days at 12 °C that show fruit decay that is typical for the top-seal packages; Figure 7 shows quality development over time of the strawberries at 1 8 °C in the three types of packaging by way of the averaged decay number. Diamonds indicate values for reference (Ref), triangles indicate values for MV 2x1410.5, and squares indicate values for MV 18/0.7. Y-axis shows averaged decay numbers, [0-5]. X-axis shows time [days]. Dashed line at Y=1.5 shows acceptance limit; Figure 8 shows development of the Calyx freshness in time for the three packages at 18 °C. Diamonds indicate values for reference (Ref), triangles indicate values for MV TS 2x14/0.5, and squares indicate values for MV IS 18/0.7. Y-axis indicates calyx freshness number. [0-3]. X-a.xis indicates time, [days]; Figure 9 shows quality development over time of the strawberries at 12 °C in the three types of packaging by way of the average decay number. Diamonds indicate values for reference (Ret), triangles indicate values for MV TS 2x1410.5, and squares indicate values for MV TS 18/0.7. Y-axis shows averaged decay numbers, [0-5].

X-axis shows time [days]. Dashed line at Y=1.5 shows acceptance limit; Figure 10 shows development of the Calyx freshness in time for the three packages at 12 °C. Diamonds indicate values for reference (Ret), triangles indicate values for MV TS 2x14/0.5, and squares indicate values for MV TS 1 8/0.7. Y-a.xis indicates calyx freshness number. [0-3]. X-a.xis indicates time, [days]; and Figure 11 shows crude permeability results of the 18/0.7 mm packages (left hand side) and of the 2x14/0.5 mm packages (right hand side). Y-axis shows gas permeability in [mi/rn2 bar day].

A

S

The following experiments detail a comparative packaging test performed with strawberries cv. Sonata and three types of packaging at two storage temperatures (12 and 18 °C). Two different top-seal packages with micro-perforated top-lids (herein referred to as "top-seal packages") were compared in protective performance with a reference of macro-perforated clamshells. The visual quality of packed strawberries was evaluated four times. The gas composition of the headspace of the micro-perforated packages was also determined over time.

In both micro-perforated top-seal packages, similar equilibrium gas concentrations developed within 4 days: 3% oxygen and 22% carbon dioxide at 18 °C. At 12 °C, the equilibrium was reached after a longer period of time and the concentrations were less pronounced: 8% oxygen and 17% carbon dioxide.

The micro-perforated top-seal packages protect the strawberries better against fruit decay than the clamshells. In the clamshells the predominant fruit decay is fungal growth (white, grey and light brown). In the micro-perforated top-seal packages the predominant type of fruit decay is softening spots (either dark-red or light red). Based on a critical quality evaluation, the shelf-life after packaging of the strawberries at 12 °C is 6 days for the clamshells and 8 days for the micro-perforated top-seals, and at 18 °C is 5 days for the clamshells and 7 days for the micro-perforated top-seals.

Additionally, the top-seals keep the calyxes greener and fresher looking than the clamshells. Hence, in general the strawberries in the top-seals look better than in the clamshells, due to: * the greener calyxes, * lesser level of fruit decay, * lesser visible fruit decay.

METHODS

Gas analysis The headspace of the micro-perforated packages was analysed with a Chrompack Micro GC CP 2002 (Varian Inc., CA, USA / Chrompack, NL) gas chromatograph for air gases (02, CO2 and N2) with 16 channels. Connections were made with a needle and samples were taken directly from the gaseous headspace. The rough GC-curves were automatically converted into volume percentages air gases.

Subjective evaluation The strawberries were taken out of the package and inspected visually one by one. The strawberries were classified in six classes [0-5] of decay. This classification is visualised in Figure 1. The amount of strawberries per class was recorded and average decay numbers were calculated with weight factors equalling the class numbers.

Moreover, an arbitrary weighing factor for the type of fruit decay was applied: 100% for fungal growth and 75% for softening spots.

Class 0 represents perfect strawberries without any defects.

Class 1 has less than 5% of surface defects, usually a small dark red softening spots, white fungal spots, light brown botrytis spots, etc. Class 2 has less than 20% of surface defects.

Class 3 has less than 33% of surface defects.

Class 4 has less than 50% of surface defects Class 5 is decayed more severely and this class also harbours completely rotten fruits.

Subsequently, the calyxes of the strawberries were classified in four classes [0-3] of freshness. This scale is visualised in Figure 2. The amount of strawberries per class was recorded and average calyx freshness numbers were calculated with weight factors equalling the class numbers Class 0 represents fully fresh green calyxes Class 1 has a small amount of little dark spots or one yellow/brown leaf Class 2 has more substantially discoloured (yellow or red) and dehydrated calyxes Class 3 has dark brown and yellow calyxes that are completely dehydrated Origin of the strawberries and handling Jover BV (Breda) supplied the strawberries. These were of the cultivar Sonata and originated from one Dutch grower, which harvested the strawberries on a first harvesting day. These were transported and were packed the next day. Three types of packages (500 grams) were used: I. Reference package: clamshell package with macro-perforations (approx. 5-10 mm diameter), 2. Top seal package 1 of Multivac, with one row of micro-perforations made with a 18/0.7 mm needle-wheel. This package was filled with 5% 02 and 10% CO2 prior to sealing. This package is denoted as MV 1 8/0.7.

3. Top seal package 2 of Multivac, with two rows of micro-perforations made with two 14/0.5 nmi needle-wheels. This packages contained normal air prior to sealing. This package is denoted as MV 2x14/0.5.

The Multivac packaging was provided using apparatus of EP1714885 with a micro-perforation wheel device (above) which defines micro-perforations in the film lid used for manufacture of the packaging. Such packaging is also referred to herein as "micro-perforated top seal packages" and suchlike.

The packaged strawberries underwent initial quality evaluationone day later (i.e. two days after harvesting), and this is referred to as "Day 0" herein and in the Figures. From the grower to quality evaluation, the strawberries were maintained at 12 °C.

Storage and moments of evaluation The strawberries were divided into two equal groups, an initial evaluation performed (shown as Day 0 in Figures 7 and 9), and were stored in two temperature-controlled cells: one at 18 °C and one at 12 °C. The packages stored at 18 °C were evaluated after 2, 5, 6 and 7 days, with respect to the moment of initial evaluation. The packages stored at 12 °C were evaluated after 5, 7, 9 and 12 days, with respect to the moment of initial evaluation.

RESULTS

Gas composition of the headspace The gas development in the headspace of both top seal packages at 18 °C and 12 °C is shown in Figures 3 and 4 respectively. Respiration and permeability clearly cause the oxygen levels to drop to less than 5%, and cause carbon dioxide levels to exceed 20% within 4 days. From the 4th to the 9th day equilibrium is reached and maintained. The equilibrium gas composition is equal for both types of top seal packages. The active gas flushing of the MV 18/0.7 packages with 5% oxygen and 10% carbon dioxide only makes these packages reach the equilibrium values a little bit faster and have a little bit more protective atmospheres during the first 2 days.

A potential protective effect of this active gas flush cannot be determined from these graphs, but is apparent from differences in quality development.

As illustrated in Figures 3 and 4, the gas development within the headspace of the top-seal packages is comparable at both temperatures. The major difference is that the equilibrium gas values are less pronounced at the lower temperature: 25% CO2 at 18 °C versus 20% CO2 at 12°C and 3% 02 at 18 °C versus 5% 02 at 12 °C. This is a logical consequence of the increased respiration at elevated temperatures.

Overall appearance Strawberries packed in the Multivac top-seals looked more attractive than strawberries packed in the reference clamshells. Several comparative photos have been made at 18 and 12 °C at various evaluation moments; see Figure 5 for some clear examples. The overall visual differences are: The calyxes remain greener in the top- seal packages; and Fruit decay is less visible in the top-seal package than in the clamshell. The most predominant type of fruit decay in the top-seal package is tissue softening spots, which can be dark red and light red (see Figure 6), whereas in the clamshell white, grey and brown fungal growth spots are most predominant (see Figure 5).

The taste of the strawberries was mildly acidic and sweet and remained constant during the packaging test. Only the strawberries that had been stored for 12 days after packaging at 12 °C smelled mildly alcoholic and also possessed a mild alcoholic taste.

Quality development at 18 °C The development of the average decay number in time is shown in Figure 7 for the three types of packaging at 18 °C. The strawberries packed in the micro-perforated top-sealed trays aie clearly less decayed than those in the clamshell. Moreover, the types of fruit decay present are also less clearly visible than those on the reference strawberries.

The acceptance limit was set to a level of 1.5 to correspond to the 5 days of shelf-life after packaging which is deemed to be acceptable when using the reference clamshell tray. With the acceptance level on 1.5, it is clearly observed that in comparison the strawberries in the Multivac top-seal packages have a shelf-life of 7 days after the moment of packaging. Hence, the Multivac top-seal packages extend the shelf-life by two days.

There is no substantial difference in shelf-life between both types of top-seals. The 18/0.7 appears to protect the fruits better than the 2x14/0.5, but this difference remains insignificant even on last of shelf-life.

The effect of the micro-perforated packages on the calyx freshness is even more pronounced. The calyxes remain much greener in the Multivac top-seal packages with respect to the clamshell, as can be seen in Figure 8 as much lower calyx freshness numbers.

shelf-lifeshelf-lifeThe reference package performs poorly. After 5 days, the calyxes of the strawberries in the clamshells have an average score of 2.4, and are almost completely discoloured and dehydrated. In contrast, the calyxes of the strawberries packed in the micro-perforated top seal packages are still green (scores of 1.2 -1.4).

Quality development at 12 °C The development of the average decay number in time is shown in Figure 9 for the three types of packaging at 12 °C. The strawberries packed in the micro-perforated top-sealed trays show less decay than those in the clamshell. Moreover, the types of decay present are also less clearly visible than those on the reference strawberries.

Both top-seals are able to prolong the shelf-life by two day at 12 °C -from 6 days in the clamshell to 8 days in the top-seal packages. The largest difference between the clamshell and the top seals is observed after the shelf-life has passed.

The calyxes are clearly greener in the top-seal packages as compared to the clamshell package at 12 °C (see Figure 10). The calyxes in the MV 18/0.7 packages hardly brown and hardly dehydrate. This contributes to an improved overall fresh appearance of the strawberries.

Permeability measurements The gas permeability values of both types of strawberry trays (18/0.7 and 2x14/0.5) were determined at 18 °C. The packages were polyester (PET)-based trays top-sealed with a thin polyester (PET)-top-film on which a row of small perforations had been applied. The amount of observed perforations is listed in Table 1. The volumes of the trays were determined by weighing the amount of water that fits in: tray with bubble wrap inlay: 1320 � 10 ml and tray without inlay: 1340 � 10 ml.

First, one needle per tray was placed in a side wall, this needle was glue to the tray and the glue was allowed to dry overnight. The next day, carbon dioxide was flushed through the trays and the trays were connected to an automated GC (gas chromatographer) with 16 channels. During 18 hours, automatic gas analyses were made of the headspaces. From the obtained slopes in gas concentrations, the permeability values were calculated. These were expressed as [ml/m2.day.bar] with the top-lid surface or as [rnl/hole.day.bar] with the amount of perforations as factor.

First, the amount of perforations were counted in the top-lids, see Table 1. Again, the needle wheel with 0.7 mm length needles proved to yield more reproducible perforations than the needle wheel with a length of 0.5 mm.

Table 1: Amount of perforations in the top-lids for both types of package.

l8/0.7mm 2xl4/O.5mrn A 10 G 17 B 10 H 15 C 10 I 16 D 10 J 15 E 10 K 15 F 10 L 15 Average 10�0 15.5�0.8 The packages were partially filled with carbon dioxide via a glued-in needle and mounted to the air gases GC. The crude results of the permeability study at 18 °C are shown in Table 2 and Figure 11 for the 18/0.7 mm packages and Table 3 and Figure 11 for the 2x 14/0.5 mm packages.

These results show that both types of packages (18/0.7 and 2x14/0.5) are equally permeable to air gases. The variation in the obtained results is smaller for the 18/0.7 trays as compared to the 2xl4/0.5 trays: 2 versus 6% (expressed as standard deviation/average). This will be caused by the variation in amount of perforations, see

Table 1.

The permeability value per hole is clearly larger for the packages that were perforated with 0.7 mm needles than for the packages perforated with 0.5 mm.

Thble 2: Determined gas permeability values for oxygen and carbon dioxide expressed per unit of area of top-film or per perforation.

No. Amount 18/0.7 mm of perf. ml ml ml ml 02/m2.bar.day 02/hole.bar.day C02/m2.bar.day C02/hole.bar.day A 10 20400� 600 200� 6 15260� 370 150�4 B 10 20414� 600 201� 6 15326� 360 151�4 C 10 19920� 540 196� 5 14890� 340 146� 3 D1 10 20483�540 201�6 15271�360 150�4

I

E 10 20670� 600 203�5 15240� 320 150�3 F 10 21183� 500 208� 6 15310� 360 150� 3 Average 20500�420 202�4 15220� 160 150�2 Table 3: Determined gas permeability values for oxygen and carbon dioxide expressed per unit of area of top-film or per perforation.

Na Amount 2x14/0.5 mm of perf. ml ml ml ml 02/rn2. bar.day O2fhole. bar.day C02/m2. bar.day C02/hole.bar.day 0 17 22060� 620 128� 4 16380� 360 95�2 H 15 24332�740 159�5 21000�220 137�1 1 16 21000� 700 138� 5 16200�400 106�3 J 15 20800�600 136�4 15500�360 101�2 K 15 21460 � 660 141 � 4 20700 � 110 135 � 1 L 15 20100� 560 132�4 15020� 330 98�2 Average 21620� 1400 139� 12 17450� 2650 112�20 The observed gas selectivity 02/C02 was 1.35 for the 18/0.7 mm packages and 1.23 for the 2x 14/0.5. These values are typical for permeation through perforations. Moreover, the smaller selectivity value for the 2x 14/0.5 package further supports the expected smaller perforation diameter for this package.

DISCUSSION

Strawberries packaged in modi fled atmospheres The top-seal packages protect Dutch grown strawberries cv. Sonata better than the reference macro-perforated clamshells. The overall appearance of the strawberries is much better in the top-seals, since the calyxes remain green for longer, the fruits are less decayed, and the type of fruit decay is less visible. In the reference clamshell packages, clearly visible fungal growth develops, whereas in the top-seal packages dark-red and light-red softening spots develop, which are more difficult to observe and more acceptable to consumers. In conclusion: with the top-seals supermarkets are able to display packed strawberries in a more attractive manner and for longer.

In order to determine the shelf-life extension for the top-seals as compared to the clamshells in a correct manner, it is important to distinguish in both types of fruit decay: fungal growth and softening spots. The consumer acceptance of fungal growth spots (white, grey or light-brown) is very low, whereas the consumer acceptance of softening spots is not so low. To reflect this difference in acceptance, the softening spots were given an arbitrary weighing factor of 75% as compared to fungal rot spots. Based on this weighing factor, shelf-life values were deduced from the measured quality development curves and the top-seals of Multivac are able to extend the shelf-life by two days. If a weighing factor of 50% was applied then the shelf-life after packaging would be extended by 3 days, going from 5 to 8 days at 18°C and from 6 to 9 days at 12 OC.

Shelf lives at 12 °C were 6 days after packaging for the clamshells and 8 days for the top-seals. At 18 °C the shelf lives were 5 and 7 days, respectively. This limited difference is caused by the perforation pattern. The current perforation patterns (18/0.7 and 2x14/0.5) are most suited for 18 °C than for 12 °C, as can be observed from the gas development curves (Figures 3 and 4). At 18 °C, the desired protective atmosphere is attained within four days, whereas less protective atmospheres are attained slower at 12 °C. Therefore, for the strawberries at 12 °C and lower temperatures the number of perforations can be reduced accordingly in order to speed the development of a protective atmosphere, without enlarging the risk of the development of anaerobic conditions in temperature abuse situations. -In the case of strawberries that are transported and displayed at beneficial lower temperatures (e.g. 4-7 °C), the perforation patterns can be further adjusted to reduce gas flow: a further reduction in the number or size of perforations should be present in the top-film to compensate for the slower respiration. However, such a packaging can only be introduced in supply chains with sufficiently well managed temperatures, since temperature abuse situations would speed the decay up instead of retarding it.

The taste of the strawberries is well maintained by the micro-perforated top-seal packages up to and beyond normal and extended shelf-life conditions. In fact, it was only after 12 days at 12 °C that an alcoholic off-taste developed in some top-seal packages. This must be caused by fermentation, due to nearly anaerobic conditions.shejf-ljfe Both top-seals performed similarly. The 18/0.7 tends to give a bit better results, but these were usually not significantly different from the results with the 2x14/0.5. This implies that active gas flushing with 5% oxygen, 10% carbon dioxide does not have a substantial beneficial effect at the temperatures of the relevant experiments. However, when the strawberries are maintained at lower temperatures, particularly below 12 °C, gas flushing is beneficial for shelf-life.

Gas exchange in modified atmosphere packages for strawberries The gas permeability study has shown that needle wheels with 0.7 mm long needles render more reproducible perforations than needle wheels with 0.5 mm long needles.

The longer needles render less variation in the amount of perforation per top-lid and in the permeability values per package.

Furthermore, the perforations made with 0.7 mm needle wheels are slightly more permeable than those made with 0.5 mm needle wheels. This suggests that the perforations made with the 0.7 mm needle wheel are larger than those made with the 0.5 mm needle wheel. The measured permeability values for oxygen and carbon dioxide were: 0.7 mm perforation: 200 ml 02/hole.day. bar and ISO ml CO2fhoIe.day.bar 0.5 mm perforation: 140 ml O2fhole.day.bar and 110 ml C02/hole.day.bar The respiration rates at equilibrium modified atmospheres at 12 and 18 °C were calculated from the measured permeability values arid the measured equilibrium head space compositions at both temperatures. The calculated vales are listed in Table 4.

Table 4: Equilibrium respiration values calculated from the measured permeation values and the measured equilibrium gas composition values.

Calculated respiration Measured equilibnum values, [mI/kg. product.

Package Gas values [%} day] 12°C 18°C 12°C 18°C 02 4.7 3.0 115 128 18/0.7 ___________ ___________ ____________ ___________ ____________ CO2 21.3 24.5 119 137 02 5.6 4.2 114 126 2x 14/0.5 ____________ _____________ _____________ ____________ ____________ CO2 20.1 23.4 129 150 These equilibrium respiration rates were fitted in the simplified respiration rate equation to obtain approximated values for: Vm02, Km02, KmnCO2 and RQ (respiration quotient V02 /VCO2) until the modelled development of the gas concentrations almost looked identical to the measured development of the gas composition, see Equation I. It must be stressed that this procedure yields only first approximated values and these values should be used carefully. The results of this fit are summarised in

Table 5.

Equation 1: Simplified Michaelis-Menten kinetics model for product respiration Vm *02 V02 = (I( + 02) * (1+ CO2JKmnco2) V02: respiration rate in terms of consumed oxygen [ml/kg.hour} 02: oxygen concentration [%] C02: carbon dioxide concentration [%] Vm02: the maximum oxygen consumption rate [ml/kg.hour] Km02: oxygen concentration at which the oxygen consumption rate is half [%} KmnCO2: carbon dioxide concentration at which the oxygen consumption is halved [%] Table 5: Fit results of respiration parameters to the observed development of the head space composition in time. These are only approximated numbers.

Respiration parameter 18/0.7 2x14/0.5 12°C 18°C 12°C 18°C Vm02 [nil/kg.hour] 220 250 220 250 Km02 [%] 2,5 1,6 5,5 4 KmnCO2 [%] 17,5 19,2 21 23 RQ 1,2 1,2 1,2 1,3 The approximated respiration parameters at 12 °C were used to forecast what a better perforation level would be for both type of packages. The calculated equilibrium gas compositions with different amount of perforations in the top-lid are given in Table 6.

From these results we can estimate that for strawberries packed and displayed at 12 °C it would be beneficial to lower the perforation level from the current levels to 9-10 for 2xl4/0.5 and 7-8 for the 18/0.7 packages.

Table 6: Predictions made with gas exchange model of equilibrium gas compositions when the perforation level of the top-lids is reduced at 12 °C.

Amount of 18/0.7 (now 10 perf.) 2x14/0.5 (now 15.5 perf.) perforations 02 CO2 02 CO2 11 --4.0 21.3 --3.6 21.6 9 4.2 22.3 3.3 21.9 8 3.6 22.8 2.9 22.1 7 3.0 23.3 --

CONCLUSIONS

The top-sealed packages with micro-perforated top-lids of Multivac protect Dutch grown strawberries cv. Sonata better than the current reference (a macro perforated clamshell). The differences in overall appearance are relatively large. The top seals keep the calyxes greener and retard the development of fruit decay. Moreover, the type of fruit decay that develops in the top-seal package is less easily observed than in the clamshell.

Based on a critical evaluation it has been established that Multivac top-seals extend the shelf-life of the strawberries with two days from the moment of packaging, both at 12 and 18 °C, going from 6 to 8 and from 5 to 7 days, respectively.

Furthermore, to improve the shelf-life of strawberries in the micro-perforated top seals at 12 °C further, it is recommended to reduce the level of perforations from 15.5 for the 2x14/0.5 packages to 9-10 and for the 18/0.7 packages from 10 to 7-8. Obviously, this will only be beneficial for supply chains in which the 12 °C is well managed and there are seldom temperature abuse situations.

Claims

1. Packaging comprising: (i) a tray comprising a base and at least one wall; and (ii) a lid; said lid defining at least one opening, each at least one opening having a surface area of between 0.00157mm2 and 0.00471mm2.

2. Packaging according to claim 1, wherein said at least one opening has an elliptical shape.

3. Packaging according to claim 1, wherein said at least one opening has a shape selected from the group consisting of: circle, triangular, square, pentagonal, hexagonal, septagonal and octagonal.

4. Packaging according to any of the preceding claims, wherein between I and 19 openings are provided.

5. Packaging according to claim 4, wherein between 12-19, 13-18, 14-17 or 15-16 openings are provided.

6. Packaging according to claim 4, wherein between 2-18, 3-17, 4-16, 5-15, 6-14, 7-13, 8-12 or 9-11 openings are provided.

7. Packaging according to any of the preceding claims, wherein said lid is made from a rigid or semi-rigid material.

8. Packaging according to any of claims 1-6, wherein said lid is made from a flexible material.

9. Packaging according to any of the preceding claims, wherein said lid is a film lid sealed to said tray.

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10. Packaging according to any of the preceding claims, wherein said lid can be in-use detached from and re-attached to said tray.

11. Packaging according to any of the preceding claims, wherein it is dimensioned to hold 200-l000g of fruit or vegetables.

12. Packaging according to any of the preceding claims, containing within it fruit or vegetables which undergo a ripening process and which are liable to rot.

13. Packaging according to claim 15, containing strawberries.

14. Packaging according to any of claims 15-17, having 5 or 6 openings having a surface area of about 0.00314mm2.

15. A method of packaging fruit or vegetables which undergo a ripening process arid which are liable to rot, comprising the steps of: (i) placing said fruit or vegetables in a tray comprising a base and at least one wall; and (ii) applying a lid to said tray; said tray and lid defining a packaging, said lid defining at least one opening, each at least one opening having a surface area of between 0.00157mm2 arid 0.00471mm2.

16. A method of packaging fruit or vegetables according to claim 15, said tray and said lid being packaging according to any of claims 1-11.

17. A method of packaging fruit or vegetables according to claim 15 or 16, said fruit or vegetables being strawberries.

17. A method of packaging according to claim 15 or 16, being a method of prolonging the shelf-life of said fruit or vegetables.

18. Packaging containing fruit or vegetables which undergo a ripening process and are liable to rot, said packaging comprising: (i) a tray comprising a base and at least one wall; and (ii) a lid; said lid defining at least one opening, at least one opening being defined in said base and being covered with seal means which restricts the flow of gases through said opening in said base.

19. A method of packaging fruit or vegetables which undergo a ripening process and which are liable to rot, comprising the steps of: (i) placing said fruit or vegetables in a packaging comprising a tray comprising a base and at least one wall, at least one opening being defined in said base; and (ii) applying a lid to said tray, said lid defining at least one opening, and covering said at least one opening in said base with seal means which restricts the flow of gases through said opening in said base.

Amendments to the claims have been filed as follows 1. Packaging comprising: (i) a tray comprising a base and at least one wall; and (ii) a lid; said lid defining at least one opening, each at least one opening having a surface area of between 0.00157mm2 and 0.00471mm2, said packaging containing strawberries.

4. Packaging according to any of the preceding claims, wherein between 1 and 19 openings are provided.

6. Packaging according to claim 4, wherein between 2-18, 3-17, 4-16, 5-15, 6-14, * ** 7-13, 8-12 or 9-11 openings are provided.

25 7. Packaging according to any of the preceding claims, wherein said lid is made from a rigid or semi-rigid material. *

** **** * 8. Packaging according to any of claims 1-6, wherein said lid is made from a * flexible material.

9. Packaging according to any of the preceding claims, wherein said lid is a film lid sealed to said tray. 2-f

11. Packaging according to any of the preceding claims, wherein it is dimensioned to hold 200-l000g of strawberries.

12. Packaging according to any of claims 15-17, having 5 or 6 openings having a surface area of about 0.00314mm2.

13. A method of packaging strawberries, comprising the steps of: (i) placing said strawberries in a tray comprising a base and at least one wall; and (ii) applying a lid to said tray; said tray and lid defining a packaging, said lid defining at least one opening, each at least one opening having a surface area of between 0.00157mm2 and 0.00471mm2.

14. A method of packaging strawberries according to claim 13, wherein said at least one opening has an elliptical shape.

15. A method of packaging strawberries according to claim 13, wherein said at least one opening has a shape selected from the group consisting of: circle, triangular, square, pentagonal, hexagonal, septagonal and octagonal. * *. *.**

16. A method of packaging strawberries according to any of claims 13-15, wherein between I and 19 openings are provided.

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*SSSS* * * 17. A method of packaging strawberries according to claim 16, wherein between 12-*S 5555 * 19, 13-18, 14-17 or 15-16 openings are provided.

*e.S.S * a 18. A method of packaging strawberries according to claim 16, wherein between 2- 18, 3-17, 4-16, 5-15, 6-14,7-13, 8-12 or 9- 11 openings are provided. 2,q

19. A method of packaging strawbenies according to any of claims 13-18, wherein said lid is made from a rigid or semi-rigid material.

20. A method of packaging strawberries according to any of claims 13-18, wherein said lid is made from a flexible material.

21. A method of packaging strawberries according to any of claims 13-20, wherein said lid is a film lid sealed to said tray.

22. A method of packaging strawberries according to any of claims 13-21, wherein said lid can be in-use detached from and re- attached to said tray.

23. A method of packaging strawberries according to any of the preceding claims, wherein said packaging is dimensioned to hold 200-l000g of strawberries.

24. A method of packaging according to any of claims 13-23, being a method of prolonging the shelf-life of said strawberries. * *. * S * * ** *0*S * * S...

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