EP0374071B1 - Food tray - Google Patents

Description

The present invention relates to a tray for packaging a food product, in particular a meat (for example a minced steak) or a fish, a preparation based on meat or fish.

More precisely, it relates to a tray having the general shape of a small dish with a flat bottom which is intended to receive the product and to be then covered (at the same time as the product) with a thin and transparent plastic film.

Trays of this type are now widely used, in particular for the packaging of meats and meat products, with a view to their presentation in stores, in particular in the refrigerated butchery departments of department stores. These are generally trays of light synthetic material, such as expanded polystyrene, covered with a stretch film of hot-welded plastic, for example polyethylene. The tray ensures the packaging its rigidity and allows easy gripping of the article by customers; the plastic film protects the product from the outside environment. Such packaging is therefore perfectly hygienic and allows good preservation of the product for several days.

In known traditional trays, the underside of the product rests directly on the bottom of the tray; this face is therefore not accessible to the air trapped in the tray.

We know that in contact with oxygen, the myoglobin which is present in the cells of the meat transforms into oxymyoglobin. This chemical phenomenon is accompanied by a change in cell color, particularly marked in beef. The natural dark red, even blackish, color of the meat turns bright red under the action of oxygen. However, it is well known that consumers are much more attracted by a bright red meat color, deemed appetizing, than by a dark red color, which suggests that the meat is not not fresh (although this is untrue).

In traditional trays, if the upper side of the product (which is not in contact with the covering film, because the height of the tray is generally chosen greater than the height of the product) is subject to this phenomenon, and takes therefore a bright red color, it is not the same for the underside which, isolated from the air, retains its dark natural color. This therefore results in an inconvenience for the consumer when the latter finds, after having removed the product from the tray, that the underside of the latter does not have the same appetizing color as the top; the consumer then has the feeling of having been deceived, considering not only that the product he has bought is not healthy, but also that the unhealthy part has been deliberately hidden from him.

This phenomenon is therefore a psychological brake on the sale of certain meat products in this type of tray, and in particular the sale of beef products such as minced steaks.

Another disadvantage of traditional trays, which also results from the fact that the product rests directly on the bottom of the tray, is that the underside of the product will constantly bathe in the exudation which is inevitably emitted by it. Now we know that the exudation liquid, very sensitive to heat, constitutes a medium favorable to the development of microbial germs; its direct contact with the product therefore compromises the good conservation of the latter. This is especially true for meats and fish. We tried to overcome this drawback by covering the bottom of the tray with blotting paper which is intended to absorb the exuded liquid; this solution is however not entirely satisfactory insofar as the product is in contact with the blotting paper, which in no way prevents the risk of contamination.

The tray described in FR-A-1 350 420 (= US-A-3 151 799) is designed to solve these problems. It is intended for receive meat and be wrapped in a wrapping sheet.

This tray has the general shape of a rectangular dish with a flat bottom having lateral edges, at least certain zones of which protrude outwards relative to the external face of the side wall of the tray, the latter being intended to receive the product - in this case the meat - and then to be covered with a thin plastic film, the latter then enveloping the tray to form opposite each of said overflowing zones an air pocket which is located outside of the tray, in the space delimited by the external face of its wall, the lower face of the projecting rim and the plastic film.

In addition, the flat bottom of the tray is lined with a series of fine ribs arranged to support the product at a certain distance above the bottom so that the product does not come into contact with the areas of this bottom. which are located between the ribs, and that the air trapped under the thin film can circulate freely in the free space thus formed between the product and the bottom.

Thus, the phenomenon mentioned above of myoglobin oxidation is well achieved; moreover, the projections isolate the meat from its exudate.

However, for reasons of space of the trays, they generally have an interior volume which is little greater than the volume of the product which they contain. The quantity of air trapped under the plastic film, inside the tray, is therefore low, and often insufficient to achieve complete oxygenation of the product.

This is why the main objective of the invention is to improve the oxygenation capacity of the product, by supplying for this a greater quantity of available air.

Another objective is to improve the quality and homogeneity of this oxygenation by promoting the circulation of air around the product.

Document LU-A-77 581 describes a tray adapted to receive stacked flat articles, such as slides. This tray has a peripheral rim projecting outwards, intended to allow its connection with a cover fitting onto the tray. In this rim are provided recesses which bottom communicate the inside of the tray with the outside. They form ventilation channels, preventing condensation, even if the slides enclosed in the tray are still wet.

A tray of this type is however not suitable for receiving certain food products, in particular meat or fish, which must be completely isolated from the outside by the plastic covering film.

The tray according to the invention is of the same general type as that according to FR-A-1 350 420. It has the general shape of a rectangular bowl with a flat bottom having lateral edges, at least certain zones of which project outwardly through relative to the external face of the side wall of the tray, the latter being intended to receive the product and then to be covered with a thin plastic film, the latter then enveloping the tray to form opposite each of said zones an air pocket which is located outside the tray, in the space delimited by the external face of its wall, the underside of the overflowing rim and the plastic film, the flat bottom of the tray also being lined with a series of fine ribs arranged to support the product at a certain distance above the bottom in such a way that the product does not come into contact with the areas of this bottom which are between the ribs, and that the air trapped under said thin film can circulate freely in the free space thus formed between the product and the bottom.

The objectives set out above are achieved by virtue of the fact that, in accordance with the invention, these overflowing zones are crossed by channels which merge into communicating the interior of the tray with the interior of the air pocket.

The volume of the pocket naturally depends on the height of the tray, the length of the area to be overflow, and the amplitude of the overflow. By properly determining these values, it is therefore possible to obtain a relatively large volume, which is not negligible compared to the volume of air trapped under the film inside the tray.

Thanks to the presence of the channels, the air contained in the external pockets is added to the internal air to achieve the desired oxygenation effect.

In addition, when - at the point of sale - the tray is placed in a refrigerated display, the air in these pockets cools faster than the indoor air, and the temperature difference generates an air movement which circulates all around the product in a particularly beneficial way.

• les zones traversées par des canaux sont les zones de coin des rebords latéraux ;
• les nervures ont une section approximativement trapèzoïdale isocèle, dont la grande base est solidaire du fond et dont la petite base sert d'appui au produit, cette petite base étant avantageusement arrondie ;
• la hauteur des nervures est comprises entre 1,5 mm et 3 mm, et est de préférence de l'ordre de 2 mm ;
• les nervures sont disposées parallèlement les unes aux autres et sont équidistantes ;
• à leur base les nervures ont une largeur de l'ordre de 2 mm et leur espacement est de l'ordre de 8 mm ;
• les nervures sont parallèles à deux des rebords de la barquette, et au moins la série de nervures située dans la région centrale de la barquette se raccorde à une série de nervures similaires formées sur les parois latérales de la barquette qui correspondent aux deux autres rebords, ces nervures étant séparées par des renfoncements (cavités) qui autorisent le passage de l'air ;
• au moins une série de nervures située au voisinage de l'un des bords de la barquette se raccorde à la paroi latérale à laquelle elle aboutit par l'intermédiaire de nervures sensiblement plus larges et plus hautes que les nervures du fond, ces nervures constituant des pavés de centrage du produit sur le fond de la barquette ; l'emplacement et les dimensions de ces nervures additionnelles de centrage sont naturellement déterminés en fonction de la forme du produit ;
• lorsque la barquette est destinée à recevoir côte à côte plusieurs produits identiques - par exemple deux ou trois produits -, elle est pourvue d'éléments aptes à assurer le centrage de chacun des produits sur le fond de la barquette, sans contrarier la libre circulation de l'air autour de ces produits ;
• ces éléments de centrage comprennent au moins une paire de plots qui sont disposés en vis-à-vis l'un de l'autre contre deux parois latérales opposées de la barquette, et la hauteur de ces plots est légèrement inférieure à celle de la barquette (pour permettre la passage de l'air au-dessus des plots), tout en étant supérieure à l'épaisseur du produit, ce qui permet l'empilage des barquettes sans dommage pour le produit.
• chacun des plots est muni sur ses côtés de nervures prolongeant les nervures du fond qui aboutissent à ce plot ;
• dans la région qui s'étend entre deux plots d'une même paire, certaines des nervures du fond sont interrompues par des nervures sensiblement plus larges et plus hautes, qui constituent des pavés de centrage sur le fond de la barquette de deux produits voisins ;
• la barquette est en matériau synthétique léger obtenu par moulage, par exemple en polystyrène expansé, et lesdites nervures de fond ainsi que - le cas échéant - lesdits éléments de centrage forment parties intégrantes venant de moulage avec le reste de la barquette.

Furthermore, according to a certain number of advantageous (but not limiting) characteristics of the invention:

• the areas crossed by channels are the corner areas of the side edges;
• the ribs have an approximately isosceles trapezoidal section, the large base of which is integral with the bottom and the small base of which serves as a support for the product, this small base being advantageously rounded;
• the height of the ribs is between 1.5 mm and 3 mm, and is preferably of the order of 2 mm;
• the ribs are arranged parallel to each other and are equidistant;
• at their base, the ribs have a width of the order of 2 mm and their spacing is of the order of 8 mm;
• the ribs are parallel to two of the edges of the tray, and at least the series of ribs located in the central region of the tray is connected to a series of similar ribs formed on the side walls of the tray which correspond to the other two edges, these ribs being separated by recesses (cavities) which allow the passage of air;
• at least one series of ribs located in the vicinity of one of the edges of the tray connects to the side wall at which it terminates via ribs substantially wider and higher than the bottom ribs, these ribs constituting blocks for centering the product on the bottom of the tray; the location and dimensions of these additional centering ribs are naturally determined according to the shape of the product;
• when the tray is intended to receive several identical products side by side - for example two or three products -, it is provided with elements capable of ensuring the centering of each of the products on the bottom of the tray, without hampering the free movement of the air around these products;
• these centering elements comprise at least one pair of studs which are arranged opposite one another against two opposite lateral walls of the tray, and the height of these studs is slightly less than that of the tray (to allow the passage of air above the studs), while being greater than the thickness of the product, which allows stacking of the trays without damage to the product.
• each of the studs is provided on its sides with ribs extending the ribs of the bottom which lead to this stud;
• in the region which extends between two studs of the same pair, some of the ribs at the bottom are interrupted by substantially wider and higher ribs, which constitute centering blocks on the bottom of the tray of two neighboring products;
• the tray is made of light synthetic material obtained by molding, for example in expanded polystyrene, and said bottom ribs as well as - where appropriate - said centering elements form integral parts coming from molding with the rest of the tray.

Other characteristics and advantages of the invention will emerge from the description and the appended drawings which show preferred embodiments thereof.

• la figure 1 est une vue de dessus d'un premier mode de réalisation de barquette selon l'invention, destinée à recevoir un steak haché ;
• la figure 2 est une vue de face partielle, à plus grande échelle, coupée par le plan II-II de la figure 1 ;
• la figure 3 est une vue de dessus d'un détail de la figure 1, à plus grande échelle, en l'occurence d'un coin de la barquette ;
• la figure 4 est une vue de côté partielle, en coupe, toujours à plus grande échelle, de la figure 1 (plan de coupe IV-IV) ;
• la figure 5 est une vue schématique en coupe transversale (correspondant au plan IV-IV) de la barquette de la figure 1 dans laquelle est conditionné, sous film plastique, un steak (S) ;
• la figure 6 est une demi-vue en coupe, analogue à la figure 5, mais selon un plan de coupe longitudinal (parallèle au plan II-II) ;
• la figure 7 est une vue analogue à celle de la figure 1, à échelle légèrement réduite ; cette vue représente un second mode de réalisation de la barquette selon l'invention, destinée à recevoir côte à côte deux steaks hachés ;
• la figure 8 représente en coupe selon le plan VIII-VIII de la figure 7 un détail de la barquette, en l'occurence un plot de centrage ;
• la figure 9 représente en perspective ce même plot et montre sa liaison avec une paroi latérale de la barquette et avec le fond de celle-ci ;
• la figure 10 est une vue analogue aux figures 1 et 7 cette vue montre un troisième mode de réalisation de barquette conforme à l'invention, destinée à recevoir trois steaks côte à côte.

In these drawings:

• Figure 1 is a top view of a first embodiment of a tray according to the invention, for receiving a minced steak;
• Figure 2 is a partial front view, on a larger scale, cut by the plane II-II of Figure 1;
• Figure 3 is a top view of a detail of Figure 1, on a larger scale, in this case a corner of the tray;
• Figure 4 is a partial side view, in section, always on a larger scale, of Figure 1 (section plane IV-IV);
• Figure 5 is a schematic cross-sectional view (corresponding to plane IV-IV) of the tray of Figure 1 in which is packaged, under plastic film, a steak (S);
• Figure 6 is a half sectional view, similar to Figure 5, but in a longitudinal section plane (parallel to the plane II-II);
• Figure 7 is a view similar to that of Figure 1, on a slightly reduced scale; this view represents a second embodiment of the tray according to the invention, intended to receive side by side two minced steaks;
• Figure 8 shows in section along the plane VIII-VIII of Figure 7 a detail of the tray, in this case a centering stud;
• Figure 9 shows in perspective this same pad and shows its connection with a side wall of the tray and with the bottom thereof;
• Figure 10 is a view similar to Figures 1 and 7 this view shows a third embodiment of tray according to the invention, for receiving three steaks side by side.

The tray shown in Figures 1 to 4 is a small bowl of light synthetic material, for example polystyrene expanded obtained by molding. It has an approximately rectangular outline, with rounded corners. In Figure 1 the tray is shown roughly at scale 1; it is dimensioned so as to receive a flat-shaped hamburger with an oval outline; this steak, designated (S), is shown in strong dashed lines inside the tray in FIG. 1.

The tray has a bottom 16 and a side wall 15. The inner face of the bottom has been designated by the reference 10, while the inner face of the side walls has been designated by the reference 11. The side wall 15 has, over the entire periphery of the tray, a rim 12; the parts of the rim corresponding to the large side of the rectangle have been designated by the reference 12a and by 12b the parts of the rim corresponding to the small side. The corner parts (corners of the rim) have been designated by the reference 13.

It will be noted that the parts 12a have an outer edge slightly set back, which gives them a narrower width than that of the rim 12b and the angular parts 13. On the other hand, the rims 12b and the corner areas 13 have a relatively wide large, so that they project substantially outwardly relative to the corresponding external face of the side wall 15 (see Figure 2 in particular).

The side walls 11 diverge very slightly towards the opening of the tray, by an angle (u) (see FIG. 2) which is of the order of a few degrees.

The bottom wall 10 is provided with a series of fine ribs 2; these are arranged parallel to each other and are equidistant; they extend over the surface 10 throughout the zone which corresponds to the surface of the steak (S). In the central region of the tray, these ribs extend over the entire width of the bottom, and consequently connect the two opposite side walls 15; on the contrary, when approaching the short sides of the tray, the length of these ribs decreases progressively, and their connection with the side walls of the tray is made by means of ribs 3 which have a width and a height substantially greater than those of the ribs 2. The lengths of the ribs 3 are determined to follow the outline of the steak (S), as is clear from the observation of FIG. 1.

The ribs 2 - which form integral parts of the bottom 16 - have a section approximately in the form of an isosceles trapezium, the large base of which is integral with the bottom while the small base is rounded. The width (l) of the rib is preferably close to its height (e), this common dimension being for example 2 mm. The spacing (k) of the ribs 2 is of the order of 8 mm.

The ribs 3 also have a cross-section in the shape of an approximately trapezoid with a rounded apex, similar to that of the ribs 2, but of substantially larger dimensions. The height (i) of these ribs 3 is for example of the order of 5 mm while their width at the base is of the order of 4 mm.

The series of central ribs, which directly connects the two large side walls of the tray, is connected to a series of similar ribs 20 which are formed on these side walls. As seen more particularly in Figure 2, the ribs 20 have a conical shape, and their width gradually decreases towards the opening of the tray. Between the ribs 20, recesses 4 are provided in the side walls 11.

The tray rim parts located at the corners and designated 13, have a thickness greater than that of the rest of the rim and, according to an essential characteristic of the invention, this additional thickness is hollowed out by a series of channels 130, the number of four in the embodiment shown; the role of these channels will be explained later.

Finally, it should be noted that the outer face of the bottom 16 has a peripheral recess 14 intended to facilitate the stacking of empty trays by nesting in one another.

Figures 5 and 6 show a minced steak (S) conditioned inside the tray, the whole being covered with a plastic film stretched and heat welded. The steak (S) rests on the series of ribs 2 and is therefore raised relative to the areas of the bottom 10 which are located between these ribs. The steak is kept in the correct position, centered in the tray, thanks to the ribs of larger dimensions 3, which act as centering blocks. It will also be noted that the tray is dimensioned in height so that the thickness of the steak is smaller than the height of free space inside the tray once the film 5 has been put in place. There is therefore a certain clearance (j) (for example of the order of 5 mm) between the film 5 and the top of the ground steak (S).

As a result, the air trapped inside the tray under the plastic film can circulate freely all around the chopped steak (S), and the oxygen it contains can therefore access any point on its surface. The shape of the ribs, their height and their spacing is such that the bearing zones of the underside of the steak with these ribs are very fine and of negligible area, these ribs nevertheless ensuring sufficient retention of the ground steak in the raised position for that the latter cannot be supported by deformation, or as a result of the penetration of the ribs inside the steak, against the free areas of the surface 10 (areas located between the ribs 2).

The underside of the steak (S), the bottom 10 and the ribs 2 therefore define a series of parallel channels in which the air can circulate; these channels open freely at their ends, either between the blocks 3, or (for the central series) in the recesses 4. Thus the air passing under the steak (S) can join the space located above this steak, and vice versa.

Because the parts 12b and 13 project outwards, the film 5 is kept spaced from the tray by spaces - or air pockets - 8 (see FIGS. 5, 6).

The quantity of air which is trapped under the film 5 outside the tray, in these pockets, is not negligible. Thanks to the fact that the corners 13 are raised relative to the edges of the tray, the film 5 does not come into direct contact with certain areas of the edges 12a, 12b, so that the air included in the spaces 8 can communicate with the interior of the tray; this possibility of communication is further increased by the presence of the channels 130.

It is therefore understood that all of the air trapped under the film 5 can come into contact with the ground beef (S), which increases the oxidation capacities of myoglobin, in accordance with the desired goal. In addition, as already said, the possible temperature differences between the inside and the outside of the tray promote the circulation of this air.

The tray 1 ′ which is the subject of the second embodiment shown in Figures 7, 8 and 9 is intended to receive side by side two minced steaks (S₁, S₂). The constituent elements of the tray identical or similar to those of the first embodiment have been given the same references.

The bottom 10 of the tray is lined with a series of grooves which this time are arranged longitudinally relative to the major axis of the rectangular tray (but always transversely relative to the major axis of the steaks). The ribs of the central region of the tray connect to similar ribs 20 provided on the walls corresponding to the short sides of the tray. The outer ribs are connected to these same walls by means of larger ribs 3 which constitute blocks for centering the steaks.

The tray is partially compartmentalized by two studs 6 which are arranged opposite one another. These studs form integral parts of the central zone of the walls constituting the long sides of the tray. Their height is slightly lower than the height of the side walls of the tray, which leaves a free space (h) above the studs (see Figure 9). It is however greater than the thickness of a steak.

The sides of these studs 6 are provided with vertical ribs 61 which extend the bottom ribs 2 leading to the studs 6, as is clearly visible in FIG. 9. A series of centering blocks is also provided between the two studs 6 7 similar to the blocks 3 previously described. By simply observing FIG. 7, it is understood that the two steaks (S₁) and (S₂) are perfectly positioned and immobilized in the tray 1 ′ thanks to the centering means 3, 7 and 6.

These centering means do not disturb the air circulation around the minced steaks; thus, as illustrated by the arrows (f) in FIG. 9, the air circulating in a channel delimited by two bottom ribs 2 leading to a stud 6 can continue to circulate in the channel delimited by two adjacent ribs 61, and bypass the stud from above.

As in the first embodiment, the rim parts 12b and 13 with an outer overhang make it possible to provide outside the tray, without the plastic film, air pockets which communicate via the channels 130 provided in the corners, with the inside of the tray to increase the desired oxygenation effect.

The contact areas of the minced steaks with the tray are very fine lines, both on the underside of the steak (resting on the ribs 2) and on its edge (resting against the ribs 61 and 20); similarly the bearing zones of the lower edge of the steaks with the blocks 3 and 7 have negligible areas. The steaks are therefore perfectly ventilated.

Because the studs 6 have a height slightly less than that of the walls of the tray, but nevertheless greater than the thickness of the product contained in the tray, these studs serve as supports of nestable nature. It is indeed possible to stack one on top of the other several trays without the product coming into contact with the upper film on the one hand and having to support the weight of the trays on the other. Thus designed, the studs therefore guarantee the maintenance of air circulation on the upper face of the product, even in the case where the trays are stacked.

The tray 1˝ which is the subject of the third embodiment illustrated in Figure 10 is dimensioned so as to receive side by side three minced steaks (S₁, S₂ and S₃). This embodiment is quite similar to that of FIG. 7, with the exception that two pairs of studs 6 are provided ensuring triple compartmenting of this tray.

It should be noted that the ribs 2 and the centering elements 6, 3, which come from molding with the rest of the tray, play a non-negligible role in stiffening the tray.

It will be noted from the observation in FIG. 8 that the stud 6 is preferably lightened in order to avoid excess thicknesses of molding materials; for this purpose a recess 62 is produced by molding in the underside of the tray.

The circular contours (C) shown in broken lines in Figures 7 and 10 simply correspond to the traces left by the ejectors provided in the manufacturing molds.

To further improve the aeration quality of the steak, provision may be made to line the underside of the ground steak with streaks crossed with respect to the ribs provided in the tray; the contact of the steak with the bottom of the tray will therefore be in point areas, which will further improve air circulation.

Although such a tray is particularly suitable for packaging a minced steak, it can be used for other meat food products, in particular slices of meat, pieces of meat (roast for example) or poultry.

It could also be used for packaging fish, meat and fish products and preparations, and - in general - any food product which is subject to exudation and / or for which it is desirable to provide aeration complete on the surface (for example fruit and vegetables).

The shape of the tray will naturally be adapted to the product concerned.

Claims (14)

1. A tray for the packaging of a food product which has the general shape of a rectangular flat-bottomed dish (1) with edging (12a, 12b) some parts of which (13) at least project outward with respect to the outer face of the side wall (15) of the tray, this being designed to receive the product and then to be covered by a thin film (5) of plastics material, the latter then enveloping the tray to form an air pocket (8) facing each of the said projecting parts (13) which is located outside the tray in the space bounded by the outer face of its wall, the inner face of the projecting edging and the plastics film (5), the flat base (10) of the tray being also provided with a set of thin ribs (2) constructed to support the product (S) at a given distance (e) above the base (10) in such a way that the product does not come into contact with the flats of this base (10) lying between the ribs, and so that the air trapped beneath the said thin film (5) can circulate freely in the free space so formed between the product (S) and the base (10), characterised in that the said projecting parts (13) are crossed by channels (130) which provide communication between the interior of the tray and the interior of the air pocket (8).
2. A tray according to claim 1, characterised in that the said parts (13) crossed by the channels (130) are the corner parts of the lateral edging (12a, 12b).
3. A tray according to either of claims 1 or 2, characterised in that the said ribs (2) have an approximately isosceles trapezoidal cross-section where the long side is integral with the base (10) and the short side is rounded and acts as a support for the product (S).
4. A tray according to one of claims 1 to 3, characterised in that the height (e) of the said ribs lies between 1.5 mm and 3 mm, and is preferably of the order of 2 mm.
5. A tray according to any one of claims 1 to 4, characterised in that the said ribs (2) are located parallel to each other and are equally spaced.
6. A tray according to one of claims 2, 3, 4 and 5 taken in combination, characterised in that the said ribs have a width (l) of the order of 2 mm at their base and a spacing (k) of the order of 8 mm.
7. A tray according to one of claims 5 or 6, characterised in that on the one hand the said ribs (2) are parallel to two of the edging portions (12a) thereof, and in that on the other hand at least the set of ribs (2) located in the central region of the tray is connected to a set of similar ribs (20) formed on the side walls (11) of the tray corresponding to the two other edging portions (12b), these ribs being separated by recesses (4) which allow the passage of air.
8. A tray according to any one of claims 1 to 7, characterised in that the said corner parts (13) of the lateral edging (12a, 12b) have a rounded shape and a greater height than the edging, the additional thickness being crossed by the said channels (130).
9. A tray according to any one of claims 1 or 8, characterised in that at least one set of ribs (2) located in the vicinity of one of the edges of the tray is connected to the side wall at which it ends by means of substantially wider and higher ribs (3) which form lands centering the product (S) on the base of the tray.
10. A tray according to one of claims 7 to 9, intended to receive several identical products (S) side by side, characterised in that it is provided with members (3, 6, 7) for centering the product on the base of the tray without obstructing the free circulation of air around the product.
11. A tray according to claim 10, characterised in that the said centering members comprise at least one pair of pads (6) each located against the opposing side walls (11) of the tray, the height of these pads (6) being slightly less than the depth of the tray, but greater than the thickness of the product.
12. A tray according to claim 11, characterised in that each of the said pads (6) is provided at its sides with ribs (61) which extend the ribs (2) of the base (10) which end at the pad.
13. A tray according to one of claims 11 or 12, characterised in that in the region extending between two pads (6) in one pair some of the said ribs (2) of the base (10) are interrupted by substantially wider and higher ribs (7) which form lands on the base of the tray for centering two adjacent products.
14. A tray according to any one of the foregoing claims, characterised in that the tray (1) is of light synthetic material obtained by moulding, e.g. expanded polystyrene, the said centering members (3, 6, 7) forming integral parts which are moulded together with the remainder of the tray.

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