IE85428B1 - Process for fully cooking bivalves with and without a sauce - Google Patents

Abstract

ABSTRACT The present invention provides a process for packing and treating mussels or other bivalve seafood, the process comprising arranging the bivalves in at least one layer in a flexible container; at least partially evacuating the container such that the container is drawn tightly around the bivalves; heating the bivalves and container for sufficient time and at sufficient temperature to at least partially cook the bivalves; characterized in that the container is formed from a lower layer and an upper layer of plastics material, and the upper layer is positioned over and secured to the lower layer after the bivalves have been arranged in the at least one layer on the lower layer, wherein, the upper and lower layers of plastics material compri se a plastics sheet having a thickness of 180-210 microns; the container is evacuated to a reduced pressure between approximately 30 — 70 mBar, the bivalves and container are heated at approximately 90 - 100° c in a steam oven for a time period of between 340 — 500 seconds, to fully cook the bivalves.

Description

Process For Fully Cooking Bivalves With and Without :1 Sauce The present invention is concerned with a process for packing bivalve seafood, For example mussels.

Seafood, and notably bivalve seafood for example mussels, has become an increasingly popular source of food. Although bivalve seafood, in particular mussels, are naturally occuning in coastal waters, they are now in many instances harvested in coastal waters on a commercial scale to meet market demands. However, one problem is that the major markets for the mussels are often distant from the source of the mussels and it is necessary to trans- ship the food over long distances.

One basic problem is that mussels cannot be frozen live or raw, nor can they be kept live by chilling. tor long periods of time in a ready to cook state, ie. graded, cleaned and debyssed.

The meat in a mussel generally forms a coating on the inside surface of the mussel shell. In order to facilitate the removal of the meat from the shell it is necessary that the mussel be cooked while it is still live or raw‘ The cooking process induces the meat to contract or curl up so that it is easily eaten. However, if the mussel is frozen while live or raw in its shell, when cooked the mussel meat will not curl up or contract to give the vendable appearance of normal cooked mussel meat. Once the mussel dies after being out of its natural environment for about a week or so, the meat will not curl up when it is being cooked. Thus, two methods of shipping mussels have been used to date.

First, live or raw mussels, after being harvested from the sea, are purified and trained to retain their juices in deputation tanks for about forty-eight hours, and in conventional manner are then graded and packed in ventilated bags and shipped to customers at ambient temperatures. This method has a number of disadvantages. First changes in temperatures during shipping can induce premature spawning which may render an entire consignment I0 ‘J- useless. Further, the mussels are in some instances at least one full week out of the sea when received by the customer. Most mussels are only seasonally available and the product does not enjoy a high level of acceptability with top rank chefs and caterers due to lack of freshness, long preparation time and wastage.

Second. mussels can be trans-shipped in a pre-cooked frozen state. In this method the mussels are harvested, purified in conventional manner, graded, debyssed and washed, pressure cooked or boiled, and then frozen, packed and shipped to the customer. This method also has some disadvantages, namely in the cooking process the shell opens and the natural juices and hence much of the flavour is lost. Also, the handling creates a danger of bacterial contamination. This product does not find great favour with top rank chefs and caterers, as the mussel meat without the protection of the juices around it, acting as a protective glaze, is deteriorated in both taste and texture by the action of the freezaing process.

Furthemiore. mussels which have been cooked and are subsequently chilled, although not frozen, are also less highly regarded since, because of the loss of juices, the meat tends to deteriorate by becoming dry with subsequent loss of taste.

EPO2-42183 discloses a process for packing and cooking mussels or similar bivalve seafood in which the mussels are located in a plastic envelope through an open end of the envelope, and are subsequently manipulated into a single layer within the envelope. The envelope is then evacuated and heat shrunk, in order to conform tightly around the shell of each of the mussels to prevent same from opening during cooking. Once the envelope has been scaled, the envelope and the contents are subjected to a heat process to cook the mussels, and the cooked mussels are then preferably frozen for transport/storage.

Thus, it is an object of the present invention to provide a process for packing and treating bivalve seafood, in particular mussels, which improves the known process disclosed above.

According to a first aspect ofthc invention there is provided a process for packing and treating mussels or other bivalve seafood. the process comprising arranging the bivalves in at least one layer in a flexible container; at least partially evacuating the container such that the container is drawn tightly around the bivalves; heating the bivalves and container for stitlicient time and at suffieient temperature to at least partially cook the bivalves; eharacteri'/.ed in that the container is formed from a lower layer and an upper layer of plastics material, the lower layer is vibrated when the bivalves are located thereon and the upper layer is positioned over and secured to the lower layer after the bivalves have been arraiiged in the at least one layer on the lower layer wherein the upper and lower layers of plastics material comprise a plastics sheet having a thickness of 130 — 210 microns; the container is evacuated to a reduced pressure between approximately 30 — 70 mBar. the bivalves and container are heated at approxiniately 90 - l0O°e in a steam oven for a time period of between 340 — 500 seconds. to fully cook the bivalves. l’ret‘er;tbly. in one embodiment, the bivalves are mussels ofa weight between approximately -tt)0gms to l.0l in Bar.

In another embodiment preferably. the bivalves are mussels ofa weight oi’ approximately 4ttt_Igms and the vacuum pressure is within the range ol‘appro> in a i‘urther embodiment preferably the bivalves are mussels ofa weight ofappro.\'imately l.0kgm and the vacuum pressure is approximately 50 — 70 mBar.

In yet a further embodiment preferably, a volume of sauce of a weight between appro.\'imatcly 20gms and l50gms is also contained within the container. the bivalves are mussels oi“-a weight of approximately 30()gms to 430gms and the vacuum pressure is within the range oi‘ approximately 30 — 50 mBar.

Pt‘et‘ei‘;il3lyx the lower layer is in the form ola tray.

Pre ferably, the process comprises the step of forming the tray by the heated deformation of a First sheet ofplastics material.

Preferably. the process comprises the step of vibrating the lower layer when the bivalves are located thereon.

Preferably, the process comprises the step of applying pressure, from above. to the bivalves located on the lower layer, in order to substantially level the lower layer.

Preferably. the process comprises the step of vibrating the bivalves, from above, when located on the lower layer and before positioning of the upper layer.

Preferably, the process comprises the step of providing the container as a heat-shrinltable plastics inatenal, the heat shrinking the container simultaneously or sequentially with the evacuation of the Container.

Preferably, the process comprises arranging the bivalves in a single layer with a substantially common orientation.

Preferably, the process comprises the step of freezing the container and bivalves following heating.

Preferably, the process comprises, prior to arranging the bivalves in the container, storing the bivalves in a reservoir of water at a temperature ofbetween 0° and 10°.

Preferably, the reservoir of water is salt water.

The invention further provides a pack of bivalves whenever prepared in accordance with the process according to the first aspect of the invention.

The present invention will now be described with reference to the accompanying drawings, in which: Fig. l illustrates a perspective view of a double line of trays formed in a plastic sheet, which trays form the lower portion of a container for ; Fig. 2 illustrates the trays of Fig. 1, one having been filled with a single layer of mussels; Fig. 3 illustrates a sectioned side elevation oftlie filled tray ofFig. 2, with a second sheet of plastic material having been applied over the first sheet of material, in order to close or seal the trays; and F i g. 4 illustrates the sectioned side elevation of Fig. 3, after the partial evacuation of the trays such that the upper and lower sheets of material have confirmed tightly around the mussels.

Refening now to the accompanying drawings, the process for packing mussels according to the present invention will now be described. Mussels 10 are harvested and purified in conventional manner, for example, in purification tanks (not shown). Next, the mussels 10 are graded by size in a conventional grading machine (not shown). Once the mussels 10 are graded they are "debyssed” which is the know term used to describe the removal of the long threads or cords by which the mussels 10 attach themselves to rocks or the like in the sea.

The mussels 10 are then ready to be packed according to the process of the present invention. Prior to packing, it is preferable that the mussels 10 are stored in a reservoir of cooled water, preferably salt water. This ensures that while the mussels 10 are waiting to be packed, the low temperature of the water, which is preferably between 0° and 10°C, the mussels 10 remain tightly shut, and so do not lose any of the water or juices contained therein. The mussels 10 comprise a top shell portion 12 and a bottom shell portion 14 which are hinged together and which remain tightly shut when the surrounding temperature is sufficiently low. to U1 When the mussels 10 are to be packed according to the process of the present invention, a quantity or portion of the mussels 10, in the example illustrated twenty four, are deposited into the lower half ofa respective container 16 (not shown in Figs. 1 and 2). Each container 16 comprises a lower layer or half in the form ofa tray 18, and an upper layer or halfin the foim of a cover 20 which closes and ultimately seals the respective tray 18, as will be desciibed in detail hereinafter. In the preferred embodiment illustrated, in order to facilitate the assembly line packing ofthe mussels 10, an array ofthe trays 18 are formed in a lirst sheet 22 of plastics material, as illustrated in Figs. 1 and 2. It is preferable that the first sheet 22 is provided in roll form (_not shown), and is drawn off the roll along the asseinbly line through a number of stations (not shown) or the like. at which various activities are carried out as set out in detail hereinafter. Thus at a first station, the array of trays 18 is fonned in the first sheet 22. in particular, the sheet 22 is momentarily halted while a pair ofheated dies or the like (not shown) are pressed into the sheet 22 and a suction pressure applied in order to form each row of the trays 18. Although in the embodiment illustrated the trays 18 are formed in rows of two on the first sheet 22, it will be appreciated that any other arrangement of the trays 18 may be provided.

Once. the trays 18 have been formed in the first sheet 22, the sheet 22 is advanced along the assembly line and at the next station (not shown) a quantity of mussels 10 are deposited into each tray 18, as illustrated in Fig. 2. Although only one of the trays 18 is shown with a poition of mussels 10 therein in Fig.2, it will be appreciated that each of the trays 18 will be similarly filled. The process of the invention also preferably includes the step of vibrating the trays 18, preferably from an underside thereof by way of a vibrating bed (not shown) or the like, once the mussels 10 have been deposited into the trays 18. This vibration serves to substantially level the mussels 10 into a single layer, as illustrated in Fig. 2.

One of the major benefits of utilising the two pait form of container 16, namely the tray 18 and cover 20, as opposed to a sleeve, is in allowing an operator, piior to the application of the cover 20, to directly contact the mussels 10 in order to manually manipulate same within each of the trays 18, to achieve the single layer as illustrated in Fig. 2. Although this manual manipulation could be achieved ifthe musselsl0 were located in a plastic sleeve or envelope, the mussels 10 could not be directly contacted and would have to be manipulated through one layer ofthe envelope. It will be appreciated that it is quicker and easier to manipulate the mussels 10 when an operator is able to directly contact the mussels 10.

The use of the tray 18, which is in the form of a depression providing a well-defined boundary at the edges thereof, ensures that during both the vibrational levelling and the manual levelling, the mussels 10 are constrained within the tray 18. It is not therefore possible for any ofthe mussels 10 to spill out ofthe tray 18, or in other words the tray 18 provides 3 positive barrier to the mussels 10 when they are being spread into a single layer.

This feature speeds up the process of spreading the mussels 10 into the single layer illustrated in Fi g 2, by reducing the care required by an operator in arranging the mussels 10 The trays 18 are preferably dimensioned to hold a pre-defined number into a single layer. ofmussels l0.

Once the mussels l0 have been deposited into the trays 18 and, optionally manually or vibration levelled, the first sheet 22 is then advanced on to a further station (not shown), in order to continue the packing process according to the present invention. As an optional step before the cover 20 is applied to each of the trays 18, downward pressure may be applied to the mussels 10 in each tray 18, in order to further effect the substantial levelling of same. This downward pressure may be applied, for example, by manually pressing a flat plate or the like (not shown) downwardly onto the exposed mussels 10. Such a plate would preferably be slightly smaller in dimension than that of the individual trays 18. The pressure applied is preferably achieved using hydraulic or pneumatic means. It is also preferable that while said pressure is being applied. the plate (not shown) is vibrated, which will further sen/C to level the mussels 10 within each tray 18. The vibration applied to the plate (not shown) may be achieved through any conventional means.

Following the above optional step in the packing process, the first sheet 22 is advanced onto the next station, where the cover 20 is applied to each of the trays 18, in order to close the trays 18 and thus form the completed containers 16. The cover 20 of each of the trays 18 is preferably initially provided as a continuous second sheet 24 of plastics material in roll form, which is advanced into position overlying the first sheet 22. The second sheet 24 is preferably of a similar or identical width to the first sheet 22. Once the second sheet 24 has been positioned over and in contact with the first sheet 22, the second sheet 24 is scaled onto the first sheet 22 as hereinafter described. In the present embodiment, each of the trays [8 are separated from one another by a border 26, which border 26 provides an area around each ofthe trays 18 at which the second sheet 24 can be heat-sealed onto the first sheet 22 in conventional fashion.

As the second sheet 24 is being heat-sealed onto the first sheet 22. each of the trays l8 are evacuated. In a preferred embodiment, in order to facilitate this evacuation. one side ofeach of the containers 16 is left unsealed, and a conventional vacuum system (not shown) is suitably applied to that open side of the container 16. Simultaneously or sequentially, the container [6 is subjected to a suitable temperature to cause it to shrink. Thus as the container lb shrinks and is sucked onto the top and bottom shell portions 12, 14 respectively of the mussels 10, substantially all of the air within the container 16 is also removed. The one remaining open side of the container 16 is then heat-sealed in conventional fasliion, under the vacuum conditions. Thus, as illustrated in Fig.4, the tray 18 and cover 20 of each container 16, as defined by the first sheet 22 and second sheet 24 respectively, are drawn tightly around the layer of mussels 10, so that the top and bottom shell portions 12, 14 are securely held together in a closed position.

Next. the sealed containers 16 are subjected to a heat process, for example by immersion in heated water, steam, or air, or a combination of same, to cause the meat within the mussels to contract and curl up to form the normal vendable appearance. This heating step may be achieved using any suitable equipment, but is preferably implemented using a steam oven or a spiral oven in order to minimise the footprint of the oven.

DJ C.» Following this heating process, the vacuum sealed containers 16 are preferably cooled to ambient temperature and may then be frozen for transport/storage, or remain at ambient temperature. As with the heating step, it is preferably that the freeze step is implemented using a spiral freezer.

The individual containers 16 are preferably separated from one another at this stage by cutting along the borders 26, although it will be appreciated that this separation could be undertaken at any other suitable point in the packing process.

In one embodiment of the invention, it has been found that the thickness of the plastics film which forms the container 16 should have a thickness of between approximately 180 microns to 210 microns. This can be dependent on the quantity of mussels to be held in the container 16, and also on the cooking time and temperature to which the product is subjected.

In a fully cooked product, the containers 16 including the mussels 10 are heated in a steam oven at between 90 — 100°C for a time period between 340 — 500 seconds. This cooking phase enables the inner core of the mussels 10 to reach a temperature of 90°C for a period of at least 90 seconds to destroy any relevant bacteria.

Willi this process the container 16 is evacuated to a pressure of between approximately 30 — 70 mbar and this pressure depends on the weight of the mussels 10 and whether or not the container 10 also includes a sauce. The vacuum source (not shown) needs to be at a level of approximately 1020 mbar before the vacuum is applied to the containers 16 before they are sealed. As a fully cooked product reaches approximately 90°c or more for a certain time period, any residual air in the container 16, will expand, so this higher level of achieved vacuum in the container 16 is essential to prevent the air in the container 16 from expanding sufficiently to the level that it could puncture the container 16 or at least render the product unusable as the mussels 10 may open if the bag expands. Also, the thickness and strength of the plastics film which constitutes the container 16 is important in terms of maintaining the integrity of the container where the heating time is relatively long and at a relatively high temperature. Also, the plastics sheet or film of the container cannot be so thick that it would result in difficulty in enabling correct cooking ofthe mussels 10. A careful balance tnust therefore be found between the thickness of the plastics sheet 22, or film of the container 16, the cooking protocol, the product to be held in the container and finally the optimum vacuum pressure which can be applied to the container 16.

In one example, the bivalves are mussels of a weight between approxiniately 400grns to l.0l{g and the vacuum pressure is within the range of approximately 50 — 70 mBar. The mussels and container 16 are heated in a steam oven at approximately 100‘r‘c for a time period of between 400 —- 480 seconds so that the inner core of the mussels reach a temperature of at least 90°C for a time period of at least 90 seconds. in a further example, the mussels 10 in the container 16 have a weight of approximately 400 gins and the vacuum pressure is within the range of approximately S0-60mbar. The mussels and container 16 are heated in a steam oven at approximately 100°C for a time period of between 400 ~ 480 seconds so that the inner core of the mussels reach a temperature of at least ‘)0°c for a time period of at least 90 seconds.

In another example, the mussels in the container 16 have a weight of approximately l.Okg and the vacuum pressure is approximately 50 — 70 mbar. The mussels and container 16 are heated in a steam oven at approximately 100°C for a time period of between 400 ~— 480 seconds so that the inner core of the mussels reach a temperature of at least 90°C for a time period of at least 90 seconds. ln a further example, the mussels 10 in the container 16 have a weight between approximately 300 gms to 430 gins and the container 16 also includes a sauce of weight Ix.) Lh between approximately 20 gms to 150 gins and the vacuum pressure is within the range of approximately 30 — 50 mbar. The mussels and container 16 are heated in a steam oven at approximately 100°C for a time period of between 340 — 500 seconds. depending on the weight of the sauce, so that the inner core of the mussels reach a temperature of at least 90% for a time period of at least 90 seconds.

For a partially cooked product, the containers 16 including the mussels are heated in a steam oven at between 90 — 100°C for a time period of between 300 — 380 seconds to enable the mussel meat within the mussel shell [0 to curl up, into the normal vendable appearance.

This cooking phase enables the inner core of the mussels to reach a temperature of approximately 90°c for a time period to partially cook the mussels, but further cooking being necessary by the end user.

With this process, the container 16 is evacuated to a pressure of between approximately 30 — 90 mbar and this pressure depends upon the weight of mussels 10 in the container 16 and whether or not the container 16 also includes a sauce. As the cooking temperature and time in the steam oven is reduced compared to the fully cooked product discussed above, the thickness ofthe plastics sheets 22, 24 of the container 16 may be of a reduced thickness and in this case it can be between approximately 160 to 180 microns. This thickness of plastic sheets 22. 24 has been found to maintain the integrity of the container 16 and together with the relevant cooking protocol and vacuum pressure, results in an optimum product in particular the maintaining of the mussel shells 10 is a substantially closed condition throughout the process according to the invention.

In one example, the bivalves are mussels of a weight between approximately 450gms to 10kg and the vacuum pressure is within the range of approximately 50 — 90 mBar. The mussels and container are heated in a steam oven at approximately 100°C for a time period of between 300 -380 seconds so that the mussels are partially cooked and the mussel meat curls up within the mussel shells.

'.»J C) In a further example, the thickness of the plastic sheets 22, 24 of the container 16 is between 160 ~ 180 microns and the weight ofmussels 10 in the container 16 is approximately 450gms and vacuum pressure is between approximately 50 — 60 mbar. The mussels and container are heated in a steam oven at approximately 100°C for a time period of between 300 — 380 seconds so that the mussels are partially cooked and the mussel meat curls up within the mussel shells.

In another example, the thickness of the plastic sheets 22, 24 of the container I6 is between 160 — 180 microns and the mussels in the container 16 have a weight of approximately 1.0 kg and the vacuum pressure is between approximately 60-90 mbar. The mussels and container are heated in a steam oven at approximately 100°C for a time period of between 300 — 380 seconds so that the mussels are partially cooked and the mussel meat curls up within the mussel shells.

In a further example, the mussels 10 in the container 16 have a weight between approximately 300 — 430 grins and the container also includes a sauce of weight between approximately 20gms to l50gms and the vacuum pressure is within the range of approximately 3080 mbar. The mussels and container 60 are heated in a steam oven at approximately 100°C for a time period of between 300 — 380 seconds so that the mussels are partially cooked and the mussel meat curls up within the mussel shells.

It is noted that where there is no sauce in the container 16, and therefore only mussels 10, the vacuum pressure does not have to be as low as when the container 16 also includes a sauce. This is because in the mussel only product the plastic sheets 22, 24 forms very closely to the shape of the mussels and little air remains in the container 16.

For the fully cooked product therefore, the greater thickness of the plastic sheets 22, 24 is elteetively a protective measure to maintain the integrity of the container 16 and therefore minimise wastage through puncturing of the container 16.

Ix) 'Jn The invention thus, provides specific method steps and product specific constnictioiial features which according to the invention have been found to provide an optimal end product being a fully cooked vacuum pack of mussels containing no sauce and also a fully cooked vacuum pack of mussels containing a sauce. In addition, the invention fuitlier provides a partially cooked vacuum pack of mussels containing no sauce and a partially cooked vacuum pack of mussels containing a sauce.

The methods of the invention provide for the freezing and chilling of the product after the frilly cooking or partially cooking stage, depending on the cooking method and how the product will be shipped to the consumer.

Claims (4)

1. CLAIMS I. A process for packing and treating mussels or other bivalve seafood. the process comprising arranging the bivalves in at least one layer in a flexible container; at least partially evacuating the container such that the container is drawn tightly around the bivalves: heating the bivalves and container lor sufticient time and at suflicient temperature to ill least partially cook the bivalves; characterized in that the container is formed from a lower layer and an upper layer ofplasties material, the lower layer is vibrated when the bivalves are located thereon and the upper layer is positioned over and secured to the lower layer alter the bivalves have been arranged in the at least one layer on the lower layer, wherein, the upper and lower layers of plastics material comprise a plastics sheet having a thickness of 180 — 210 microns; the container is evacuated to a reduced pressure between approximately 30 ~ 70 mBar. the bivalves and container are heated at approximately 90 - l00°c in a steam oven for at time period ofbetween 340 -— 500 seconds, to fully cook the bivalves.

2. A process as claimed in claim I wherein the bivalves are mussels ofa weight between approximately 400gms to l.0kg and the vacuum pressure is within the range of approxiinately 50 - 70 mBar.

3. A process as claimed in claim I wherein the bivalves are mussels ofa weight of zipproximately 400gms and the vacuum pressure is within the range ofapprminiately S0 — 60 mB:tr.

4. A process as claimed in claim I wherein the bivalves are mussels ofa weigltt of ;tppro.\‘imately ltlkgtn and the vacuum pressure is approximately 50 70 mBar. S. A process as claimed in claim l. wherein a volume of sauce ofa weight between appro.\'imately 20gms and l50gms is also contained within the container. the bivalves are mussels ofa weight of approximately 300gms to 430gms and the vacuum pressure is within the range of approximately 30 — SO mBar. 6. A process according to any preceding claim in which the lower layer is in the form ofa tray. 7. A process according to claim 6 comprises the step of forming the tray by the heated deformation ofa first sheet of plastics material. 8. A process according to any preceding claim comprising the step of applying pressure, from above, to the bivalves located on the lower layer, in order to substantially level the lower layer. 0. A process according to any preceding claim comprising the step of vibrating the bivalves. from above. when located on the lower layer and before positioning oithe upper laycn I0. heat-slirinkable plastics material, and heat shrinking the container simultaneously or A process according to any preceding claim comprising providing the container as a sequentially with the evacuation ofthe container. single layer with a substantially common orientation. A process according to any preceding claim comprising arranging the bivalves in a 12. A process according to any preceding claim comprising the step ol‘ freezing the 30 container and bivalves following heating. 16 I3. A process according to any preceding claim comprising, prior to anranging the bivalves in the container. storing the bivalves in 21 reservoir of water at a temperature of hem-eel) 0° and I0’. . I4. A process according to claim 13 in which the reservoir ofwatcr is sail water. IS. A pack of bivalves whenever prepared in accordance with the process according to any ofcfaints 1 to 14.