GB2519135A

GB2519135A - Method of processing and packaging foodstuffs

Info

Publication number: GB2519135A
Application number: GB1318038.5A
Authority: GB
Inventors: David Peel; Tony Thorpe; Allan Christie; Leslie Woodward
Original assignee: Tilda Ltd
Current assignee: Tilda Ltd
Priority date: 2013-10-11
Filing date: 2013-10-11
Publication date: 2015-04-15
Also published as: GB201318038D0

Abstract

A method of preparing foodstuffs in containers comprises purging substantially all oxygen from the interior of the container by introducing a gas or mixture of gases. A foodstuff is introduced into the container before sealing the container. The foodstuff is processed and sterilised, wherein in said processing step the foodstuff is fully hydrated/elongated prior to sterilisation by applying a stepped temperature profile/gradient at pressure while under rotation. The foodstuff may be rice, pasta or noodles. Preferably the container is a plastics pouch. The processing conditions ensure that the packaged foodstuff does not agglomerate.

Description

Method of Preparing and Packaging Foodstuffs

Field:

The present invention relates to a method of preparing and packaging cereal or grain-based foodstuffs. Particularly, the present invention is directed towards an improved method for cooking and packaging rice to improve the quality of the cooked rice.

Background:

It is known to produce packaged cooked rice by a process of placing the uncooked rice inside packaging such as a pouch, flushing the packaging with an inert gas, such as nitrogen, sealing the packaging, heating the rice in the packaging to sterilise the rice and packaging and simultaneously cook the rice.. Flushing the packaging with an inert gas produces what is generally referred to as Modified Atmosphere Pack (MAP). This technique is used to reduce the atmospheric air, and in particular, oxygen content within a sealed pack. By reducing the oxygen content of a sealed pack, the shelf life of a product can be significantly increased by delaying the onset of oxidative rancidity, particularly in products containing oils.

The conventional MAP process involves filling the pouches with a foodstuff and flushing the pouches with inert gases (such as nitrogen and carbon dioxide) to reduce their oxygen content. The pouches are then mechanically squeezed to remove substantially all of the gas mixture and then sealed to achieve a residual oxygen content of typically below 2% and ideally below 1%. After sealing, the pouch is subjected to the full retort sterilisation process. As well as delaying the onset of oxidative rancidity the inert gas or gas mixture inhibits proliferation of some micro-organisms (moulds and bacteria) in combination with sterilization with no significant chemical alteration of the product.

A problem encountered in known methods is that the conventional process may result in the individual rice grains clumping or agglomerating together to form large lumps.

This is undesirable as the resulting texture is generally not acceptable to consumers.

Furthermore, the clumped or agglomerated rice is difficult to pour out of the pouch.

Accordingly, when emptying conventionally processed pouches the contents are often lumpy and unappealing to the consumer. The consumer is compelled to squeeze the pouch during or subsequent to emptying its contents in order to break up and separate the agglomerated foodstuff. Indeed some packs now contain instructions to squeeze or break-up their contents before heating. The compressed or "blocked" grains may be very dry and under-cooked or under hydrated. This comes from a drive for product efficiency and cost rather than achieving a quality product.

Certain methods have been developed to overcome this problem. For example, in European Patent No. 1723036, a method was developed providing a step of partially inflating the pouch which was found to reduce agglomeration of its contents and promote conditions wherein the foodstuff retains its original and familiar characteristics.

It is an objective of the present invention to provide an improved method of cooking and packaging rice, such as for example, Basrnati rice and other foodstuffs which provides separate and free-flowing grains with a texture (when re-heated) which is similar to a home-cooked product.

Summary:

In accordance with one aspect of the present invention there is provided a method of preparing foodstuffs in containers, the method comprising: purging substantially all oxygen from the interior of the container by introducing an inert gas or mixture of gases; introducing a foodstuff into the container; sealing the container; and processing and sterilising the foodstuff, wherein in said processing step the foodstuff is fully hydrated/elongated by applying a stepped temperature profile at a pressure above ambient temperature while under rotation.

In one embodiment of the invention, the temperature in said processing step may be raised to and controlled at a temperature of between 40 to 85°C during the a first processing stage.

Additionally, or alternatively, the pressure in said processing step may be raised to and controlled at an overpressure of 0.2 to 0.60 bar during the first processing stage. The temperature may be controlled over a period of 6 to 13 minutes.

In another embodiment, temperature in said processing step may raised to and controlled at a temperature of 80 to 122°C during a second processing stage. Additionally, or alternatively the pressure in said processing step may be raised to and controlled at an overpressure of 0.47 to 1.455 bar during the second processing stage. The temperature and pressure may in this embodiment controlled over a period of 13 to 23 minutes during the second processing stage.

In another embodiment, the temperature in said processing step may be raised to and controlled at a temperature of 121 to 121.5°C during a third processing stage. Additionally or alternatively, the pressure in said processing step may raised to and controlled at an overpressure of 1.25 to 2 bar during a third processing stage. The temperature and pressure may becontrolled over a period of 18 to 25 minutes during the third processing stage.

In another embodiment of the invention, the temperature may be reduced to at least 29°C during the fourth action. Additionally or alternatively, the pressure may be reduced to an overpressure of 0 to 0.1 bar during the fourth action. The fourth action may have a duration of 22 to 30 minutes.

Preferably, the rotation occurs during at least one of the first, second and fourth processing stages. The rotation may be at a speed of up to 2.7 rotations per minute during the first processing stage and up to 1 rotation per minute during the second processing stage and up to 1 rotation per minute during the fourth action.

The foodstuff according to the invention is preferably cereal based. The cereal may be selected from the group consisting of rice, couscous, wild rice, barley, wheat, oats, rye, millet and maize. In a preferred embodiment, the cereal is rice and the rice may be basmati rice.

In one embodiment of the invention, a rice product has contents in the pouch comprising rice in the range 16.0% to 42%, other food solids in the range 2% to 41%, and liquid in the range 36% to 72%.

In another embodiment, the foodstuff may comprise rice in the range 16% to 42%, other food solids in the range 2% to 24%, and liquid in the range 53% to 72%.

In an even further embodiment, the foodstuff may comprise rice in the range 17% to 39%, other food solids in the range 2% to 24%, and liquid in the range 54% to 72%.

In a further embodiment, the foodstuff may comprise rice in the range 18% to 28.5%, other food solids in the range 12% to 18.5%, and liquid in the range 55% to 67%.

In the method according to the invention, the container may be a flexible-walled container. Preferably, the flexible-walled container may be a plastics pouch with oxygen and vapour barrier. In one embodiment, the container may be a semi rigid container with an oxygen and vapour barrier. In another embodiment, the semi rigid container may be a tray or pot.

It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration.

As will be realised, the invention is applicable to other and different embodiments and its specific details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

The invention will now be further described with reference to the following exemplary embodiment.

Brief description of the Drawings:

Referring to the drawings an embodiment of the present invention is illustrated by way of example, and not by way of limitation, wherein: Figure 1 is a flow diagram showing the various steps in the method of the present invention.

Detailed Description of the Various Embodiments:

The present description is directed towards a method of cooking and packaging foodstuffs; particularly, the method relates to the cooking and packaging of rice, in particular the method relates to the cooking and packaging of Basmati rice. However, it will be appreciated that although the following description will refer to the packaging of rice, the method is equally suitable for packaging other cereal or grain based foodstuffs.

For example, but not limited to, couscous, wild rice, barley, wheat, oats, rye, millet, maize etc. The method is also suitable for packaging rehydrated or expandable starch based products, for example, but not limited to pasta and noodles.

Additionally, the method described herein is equally applicable for the use of par-boiled and non par-boiled grains. Furthermore, it will be appreciated that the foodstuffs may comprise one or more types of cereal or grains and may comprise other foodstuffs.

In general, the method described herein is applicable to foodstuffs, which are potentially subject to agglomeration, but where a separated, free flowing consistency and appearance is desired.

General Overview of Packaging Method Fig. 1 outlines the various steps involved in implementing the method of preparing and packaging a foodstuff according to the present invention.

In this embodiment the method is used to cook and package Basmati rice. In other examples the method may be applied to other types of rice, or other foodstuffs.

The first stage involves sealing the uncooked Basmati rice into a package, for example a flexible gusseted pouch.

In order to do this the pouch is picked up by its top corners, and then held at its top corners during the remainder of the process. Throughout the description, the terms "pouch" and "container" are interchangeable. The pouch is preferably a retort pouch with an oxygen and vapour barrier and may optionally comprise a plastic and metal foil laminate pouch. Additionally or alternatively, the pouch has a bottom gusset and therefore is a "stand-up pouch".

In other examples the package may be a retort semi-rigid container with an oxygen and vapour barrier rather than a pouch. Such semi-rigid containers may for example comprise trays or pots. In such examples suitable changes should be made to the methods used to handle the containers.

In general the rice can be heated by consumers within the package using a microwave oven, or the rice can be removed from the package before being heated. In examples where a metal foil laminate pouch is used it will not be possible to heat the rice within the package using a microwave oven.

Step 1: The first step involves mechanically separating the walls of the unsealed end of the pouch by introducing a nozzle between the walls of its open end. A gas, such as Nitrogen gas is then introduced between the walls to increase the pressure within the pouch and thus deploy the pouch from a substantially flat, folded configuration to an open unfolded configuration. Although the inert gas described herein is nitrogen, it will be appreciated that other inert gases such as carbon dioxide, helium, argon, neon and xenon could be used. In other examples a blend of gases could be used. As will also be appreciated by one of skill in the art, such a blend of gases could also include for example, oxygen, but in different proportions depending on the nature of the product.

The nature of the gas is not a limiting feature as any suitable gas may be used, depending on the product to be included in the pouch, in order to inflate the pouch.

Step 2: In the second step a mixture of rice and liquid is introduced into the opened pouch whilst the flow of gas is maintained. This step ensures that oxygen is flushed from the pouch before being trapped by the rice and liquid. In some examples a mixture of gasses may be used to flush the pouch. In some examples the rice and liquid are introduced simultaneously as a mixture. In other examples the rice and liquid may be separately introduced into the package.

In order to ensure proper cooking of the rice an appropriate ratio of rice to liquid must be used. This selection will generally vary from case to case depending on the desired properties of the cooked rice product. Further, this may vary from case to case depending on the properties of the specific batch or strain of rice used, and on any other materials, such as vegetables, included with the rice.

In one example, a rice product has contents in the pouch comprising rice in the range 16.0% to 42%, other food solids in the range 2.% to 41%, and liquid in the range 36.% to 72%.

In a more specific example, a rice product has contents in the pouch comprising rice in the range 16.0% to 42%, other food solids in the range 2% to 24%, and liquid in the range 53% to 71%.

In another more specific example, a rice product has contents in the pouch comprising rice in the range 17% to 39%, other food solids in the range 2% to 24%, and liquid in the range 54% to 72%.

In another more specific example, a rice product has contents in the pouch comprising rice in the range 18% to 28.5%, other food solids in the range 12% to 18.5%, and liquid in the range 55% to 67%.

In another more specific example, a rice product has contents in the pouch comprising rice in the range 19% to 26%, other food solids in the range 27% to 41%, and liquid in the range 36% to 53%.

In another more specific example, a rice product has contents in the pouch comprising rice in the range 20% to 27%, other food solids in the range 25% to 32%, and liquid in the range 47% to 57%.

The other food solids may for example be herbs, spices and vegetables, If other foodstuffs are cooked rather than rice, the amount of liquid required will depend on the identity of the foodstuff but the amounts listed in relation to rice above may also be applicable to other grain based products.

Step 3: In a third step, after the rice and liquid has been introduced into the pouch, a flat nozzle is inserted into its unsealed end. The walls of the unsealed end are pulled tight against the nozzle, which then inflates the pouch with nitrogen gas. Once the pouch is inflated, the flat nozzle is removed from the pouch, and the pouch is sealed.

The nitrogen or other suitable gas or gases may be introduced into the pouch in a controlled manner to inflate it to a desired volume. Once the pouch reaches the desired volume, the nozzle is removed. The desired volume will vary depending upon the amount and type of rice being packaged.

In an alternative option, the pouch may be over-inflated. It is to be understood that by over-inflate, it is meant that the pouch is inflated to a volume which is greater than the desired volume. After this over-inflation the pouch is squeezed in a controlled manner thus removing a selected volume of nitrogen gas and reducing the overall volume of the pouch from its over-inflated level to a desired volume. In this option, this squeezing controls the final volume of the pouch. Again, in this option the desired volume will vary depending upon the amount and type of rice being packaged.

Step 4: The fourth step involves sealing the pouch. The pouch is heat sealed immediately after the correct volume has been reached and the nozzle has been removed, to prevent air re-entering the pouch.

Step 5: The fifth step involves placing the pouch in a retort vessel. The retort vessel is a sealed vessel having a controllable temperature and pressure. Although only a single pouch is referred to in this description, it will be understood that a large number of pouches may be placed in the retort vessel and processed simultaneously.

Once the required number of pouches are placed within the retort vessel, they are subject to thermal processing with controlled over pressure.

Step 6: In the sixth step the rice is processed by heating over a period of time at an over pressure, that is, at a pressure above ambient atmospheric pressure, while the pouch is rotated according to a predetermined movement profile. The temperature and pressure are increased gradually over time following a predetermined temperature and pressure profile.

The pouches are sealed and each pouch contains a mixture of the gas and vapor from the liquid placed in the pouch. Accordingly, the internal pressure within each pouch will change in dependence on the temperature of the pouch. Further, because the pouches are flexible the volume of each pouch will vary depending upon the relative pressures within the pouch and outside the pouch, that is, the pressure within the retort.

By raising the pressure within the retort gradually over time at substantially the same time as the temperature within the retort is increased the pressure difference between the interior and exterior of each pouch, that is between the interior of each pouch and the interior of the retort, is controlled so that the volume of the pouch is kept large enough to avoid compression of the rice grains and to allow movement of the rice grains in response to the rotation of the pouches, and excessive pressures within the pouch, which could potentially rupture the pouch, are avoided.

In stage 1 of the processing step the pouches may be rotated at a speed of up to 2.7 revolutions per minute. In some examples the temperature applied to the rice containing pouch in the retort vessel may be raised to a temperature in the range 40°C to 85°C. In some examples in this embodiment, the pressure may be raised to an overpressure of 0.2 to 0.6 bar.

In some examples the pouches may be rotated at the same speed during the first and second stages. In some examples the processing temperature and pressure in the second stage may be at the maximum temperature and pressure reached at the end of the first stage.

In some examples the total duration of the first and second stages combined may be in the range 6 minutes 45 seconds to 12 minutes 15 seconds.

In stage 2 the pouches are rotated at a speed of up to 1 revolution per minute. In some examples the temperature in the retort vessel and applied to the rice pouch may be raised to a temperature in the range 80°C to 121.5°C. In some examples the pressure may be raised to an overpressure of 0.47 to 1.455 bar.

In the third stage, the rice may be sterilised at a temperature in the range 121.3°C to 121.5°C applied in the retort vessel. In some examples of this embodiment, the pressure applied for sterilisation may be at an overpressure of 1.25 to 2.20 bar. In some examples the duration of the third step may be in the range 18 minutes 15 seconds to 25 minutes.

In the fourth stage the rice is allowed to cool and the overpressure is gradually released, over a time period ranging from approximately 20 to 30 minutes and in some embodiments, 22 minutes 16 seconds to 29 minutes 46 seconds. The pressure and temperature within the retort are monitored and controlled to control the volume of the pouches.

In some examples the pouches may be rotated at a speed of up to 1 revolution per minute during this fourth stage. In some examples the temperature applied in the retort vessel may be cooled to a temperature in the range 29.1°C to 30°C. In some examples the pressure may be reduced to an overpressure of 0 to 0.2 bar. In some examples the duration of the fourth step may be in the range 22 minutes 16 seconds to 29 minutes 46 seconds.

Finally, the retort is dropped to ambient pressure and opened, and the pouches are removed. The pouches of cooked and sterilised rice are then handled as normal for distribution to consumers.

Without being limited to the underlying theory, it is thought that the use of a stepped pressure and temperature profile together with movement according to the invention provides the advantage that the grains, such as rice, are allowed to swell in length and girth or that the grains, advantageously remain as individual grains throughout the process.

As discussed above, during the grain cooking process, pouch volumes and movement patterns are monitored and determined. It is achieved in the following ways although other suitable ways will be readily available to those skilled in the art: Rice Process: During trials the temperature of the foodstuffs is measured and recorded through the process within the pouches; preferably wherein the temperature is measured at a pre-determined point. The pre-determined point is established by experimental means and is typically, the coldest part of the product from a thermal heat transfer perspective. A time versus temperature chart is prepared from the data and organoleptic attributes of the processed product are evaluated. The identified time/temperature profile is then used during production.

Pouch volume: Control of pouch volume is achieved by balancing pressure within the pouch and the applied overpressure in the retort environment throughout the process.

This may be accomplished during trials by measuring pressure inside the pouch, and within the retort environment and recording the data throughout the process at regular intervals. It will be appreciated that the time intervals may be adjusted to any suitable time interval; wherein the suitability of the time interval is dependent on the length of cooking of the type of foodstuffs itself. A time versus pressure chart is prepared from the data and organoleptic attributes of the cooked product are evaluated. The identified time/pressure profile is then used during production. It should be noted that the pouch movement and the temperatures and pressures are interdependent. That is, changes in the pouch movement will generally affect the required temperature and pressure.

Movement: The timing and duration of movement of the pouches is recorded during trials. A time versus movement chart is prepared from the data and organoleptic attributes of the cooked product are evaluated. The identified time/movement profile is then used during production.

It will be understood from the above description that the temperature, time, pressure and movement profiles are all interrelated and all affect the final product attributes. All three profiles must be controlled to optimize the final product attributes.

The preceding steps provide the means to manufacture long shelf-life ambient stable grain-based products in hermetically sealed pouches. Further, processing the grains in the specified manner using a specified temperature and pressure profile ensures that when re-heated, these grain-based products are presented to the consumer as free-flowing and separate grains with an optimum length of grain and texture.

A number of embodiments have been described herein. However, it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the embodiments as defined in the claims appended hereto.

Claims

Claims: 1. A method of preparing foodstuffs comprised in containers, the method corn prising: purging substantially all oxygen from the interior of the container by introducing a gas or mixture of gases; introducing a foodstuff into the container; sealing the container; and processing and sterilising the foodstuff, wherein in said processing step the foodstuff is fully hydrated/elongated prior to sterilisation by applying a stepped temperature profile/gradient at a pressure above ambient temperature while under rotation.
2. The method of claim 1, wherein the temperature in said processing step is raised to and controlled at a temperature of between 40 to 85°C during the a first processing stage.
3. The method of claim 1 or claim 2, wherein the pressure in said processing step is raised to and controlled at an overpressure of 0.2 to 0.60 bar during the first processing stage.
4. The method of claim 2 or 3 wherein said temperature is controlled over a period of 6 to 13 minutes.
5. The method of any preceding claim, wherein temperature in said processing step is raised to and controlled at a temperature of 80 to 122°C during a second processing stage.
6. The method of any preceding claim, wherein the pressure in said processing step is raised to and contolled at an overpressure of 0.41 to 1.455 bar during the second processing stage.
7. The method of any preceding claim, wherein the temperature and pressure are controlled over a period of 13 to 23 minutes during the second processing stage.
8. The method of any preceding claim, wherein the temperature in said processing step is raised to and controlled at a temperature of 121 to 121.5°C during a third processing stage.
9. The method of any preceding claim, wherein the pressure in said processing step is raised to and controlled at an overpressure of 1.25 to 2 bar during a third processing stage.
10. The method of any preceding claim, wherein the temperature and pressure are controlled over a period of 18 to 25 minutes during the third processing stage.
11. The method of any preceding claim, wherein the temperature is reduced to at least 29 °C during the fourth action.
12. The method of any preceding claim, wherein the pressure is reduced to an overpressure of 0 to 0.1 bar during the fourth action.
13. The method of any preceding claim, wherein the fourth action has a duration of 22 to 30 minutes.
14. The method of any preceding claim, wherein the rotation occurs during at least one of the first, second and fourth processing stages.
15. The method of claim 15, wherein rotation is at a speed of up to 2.7 rotations per minute during the first processing stage.
16. The method of claim 15 or 16 wherein the rotation is at at a speed of up to 1 rotation per minute during the second processing stage.
17. The method of any one of claims 14 to 17, wherein the rotation occurs at a speed of up to 1 rotation per minute during the fourth action.
18. The method of any preceding claim, wherein the foodstuff is cereal based.
19. The method of any preceding clairri, wherein the cereal is selected from the group consisting of rice, couscous, wild rice, barley, wheat, oats, rye, millet and maize.
20. The method of any preceding claim, wherein the cereal is rice.
21. The method of claim 20, wherein the rice is basmati rice
22. The method of claim 20 or claim 21, wherein a rice product has contents in the pouch comprising rice in the range 16.0% to 42%, other food solids in the range 2% to 41%, and liquid in the range 36% to 72%.
23. The method of claim 22, wherein the foodstuff comprises rice in the range 16% to 42%, other food solids in the range 2% to 24%, and liquid in the range 53% to 72%.
24. The method of claim 22, wherein the foodstuff comprises rice in the range 17% to 39%, other food solids in the range 2% to 24%, and liquid in the range 54% to 72%.
25. The method of claim 22, wherein the foodstuff comprises rice in the range 18% to 28.5%, other food solids in the range 12% to 18.5%, and liquid in the range 55% to 67%.
26. The method of any preceding claim, wherein the container is a flexible-walled container.
27. The method of claim 26, wherein the flexible-walled container is a plastics pouch with oxygen and vapour barrier.
28. The method of any one of claims ito 27, wherein the container is a semi rigid container with an oxygen and vapour barrier.
29. The method of claim 28, wherein the semi rigid container is a tray or pot.
30. The method of any preceding claim, wherein the gas is an inert gas selected from the group consisting of nitrogen, carbon dioxide, helium, argon, neon and xenon.