GB2336350A

GB2336350A - Preservation of food

Info

Publication number: GB2336350A
Application number: GB9828470A
Authority: GB
Inventors: David John Humphreys; Kevin Christopher Spencer
Original assignee: Safeway Stores Inc
Current assignee: Safeway Inc
Priority date: 1998-04-18
Filing date: 1998-12-24
Publication date: 1999-10-20
Also published as: GB9808117D0; GB9828470D0

Abstract

A method of preserving and a process for packaging food comprises packaging the food in an argon rich environment in a substantially gas impermeable container. Preferably the argon rich environment is formed by applying an argon rich gas which preferably comprises at least 50% argon, 0-40% carbon dioxide and optionally up to 10% oxygen. The food is preferably a ready meal type product and may be pre-cooked or cooled prior to packaging.

Description

2336350 -1DESCREPTION PRESERVATION OF FOOD The present invention relates

to the preservation of food and in particular, but not exclusively, to the preservation of pre-prepared "ready meals" or their constituents.

The popularity of pre-prepared "ready meals" which are purchased in-store and subsequently cooked or reheated at home has increased significantly over recent years. A very wide variety of ready meals is now available and although some ready meals are preserved by freezing and therefore have a relatively long storage life the popularity of chilled (as opposed to frozen) is increasing, primarily as a result of the perceived superior flavour and texture as compared with frozen products.

The fact that chilled ready meals are not frozen means that great care must be taken to store the products continuously at reduced temperatures, failing which the products can deteriorate to an unacceptable level. By their very nature, chilled ready meals have a relatively short shelf life which contributes to their increased cost.

It is known to prolong the shelf life of some food products by gaspackaging them in a mixture of nitrogog and carbon dioxide. The nitrogen content varies from 50% to 80% and the carbon dioxide content varies from 50% to 20%, a typical mixture comprising 65% nitrogen and 35% carbon dioxide.

Such gas mixtures are effective in reducing the severity of the oxidising atmosphere and therefore help to increase the shelf life of the product. However, -2one disadvantage with such known gas mixtures is that the carbon dioxide content can discolour some foods. Thus, whilst the use of such gas mixtures increases the time for which a product may be safely kept, the product itself may not be particularly visually appealing (or sellable) to potential customers.

It is an object of the present invention to extend the useful shelf life of foods, in particular but not exclusively ready meals by preventing unacceptable deterioration of the product during storage. This is particularly applicable to chilled foods but is also applicable to frozen foods.

In accordance with a first aspect of the present invention, a method of preserving food comprises packaging the food in an argon-rich atmosphere in a substantially gas-impermeable container.

The use of an argon-rich atmosphere in contact with the product is found both to prolong the shelf life of the product and, just as importantly, greatly reduce the deterioration in taste quality and appearance. Taste tests have consistently resulted in very high scores for food preserved in accordance with the present invention.

The argon-rich environment may comprise substantially 100% argon or may comprise one or more other gases in addition to argon.

Preferably, the products are stored in an environment comprising argon and carbon dioxide. Contrary to what might be expected, if the argon and carbon dioxide are mixed in the correct proportions, the carbon dioxide content of the mixture does not produce the unwanted effects of the prior art mentioned above.

Preferably, an argon-rich gas mixture is applied to the food. The gas 0 CI mixture may comprise substantially 100% argon or may comprise one or more other gases in addition to argon. Preferably, the gas mixture applied to the food comprises from 50% to 100% argon by volume. More preferably, argon forms at least 70% of the gas mixture.

The balance of the gas may comprise carbon dioxide andlor oxygen. For example, the gas may comprise (all proportions are by volume): 50% argon, 50% carbon dioxide 60% argon, 40% carbon dioxide 65% argon, 35% carbon dioxide 70% argon, 30% carbon dioxide argon, 25% carbon dioxide argon, 20% carbon dioxide argon, 10% carbon dioxide argon, 20% carbon dioxide and 10% oxygen argon, 25% carbon dioxide and 10% oxygen argon, 30% carbon dioxide and 10% oxygen argon, 40% carbon dioxide and 10% oxygen 75% 80% 90% 70% 65% 60% 50% The present invention includes all gases or gas mixtures comprising at least 50% argon by volume with the balance comprising carbon dioxide and/or oxygen in proportions ranging from 0% to 50% each. The mixture may comprise other gases instead of, or in addition to, those mentioned.

Preferably, the oxygen content of the mixture does not exceed 10% of the 4- total gas volume.

Preferably, the carbon dioxide content of the mixture is from 10% to 40% (and more preferably 20% to 30%) of the total gas volume.

The actual gas mixture in contact with the product may comprise traces of atmospheric gases which were not displaced andlor gases which emerge from the product itself after packaging but the preserving gas mixture preferably comprises one or more of only argon, carbon dioxide and oxygen.

It has been found that the use of a gas mixture having an argon content as indicated above results in a noticeable improvement in shelf life. The improvement in the shelf life appears to be largest when the argon content is from 70% to 90% by volume of the total gas mixture and the organoleptic quality is maximised when the argon content is from 80% to 100% by volume of the total gas mixture.

The present invention has been found to be particularly suitable for preserving chilled pre-prepared "ready meals" which tend to have a relatively short shelf life. An additional advantage of using argon, in contrast to the nitrogen of the prior art, is that argon is denser than air and the air formerly surrounding the food is more efficiently displaced during packaging of the food, thus resulting in lower residual oxygen levels as compared with the prior art, but with the use of a similar amount of gas (or even less) to that used in the prior art.

In accordance with a second aspect of the present invention, a process for packaging food comprises enclosing the food in a substantially gasimpermeable packaging, introducing an argon-rich gas into the packaging and sealing the packaging to enclose the argon-rich gas within the packaging.

-S- Reference to a "substantially gas-impermeable" container means a container which is effective in maintaining the gas mixture within the container substantially constant during storage of the product.

By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawing which is a schematic flow diagram of a method of production of ready meals in accordance with an embodiment of the present invention.

Referring to the Figure, at step 10 (hereinafter referred "step" will be replaced by "S") the ingredients for a ready meal are prepared and at S12 the ingredients (whether raw, part-cooked or cooked) are assembled in individual trays 18. At S 14 the assembled meal is cooked or part-cooked. The cooked or partcooked meal is then cooled at S 16. The ready meals in their trays are then placed on a packing line indicated generally at 20. The packing line is shown schematically and comprises an endless conveyor 22. The container is shown as transporting a series of equally-spaced trayed ready meals 24.

As for the conventional use of nitrogen and carbon dioxide, a so-called Iance" 26 is displaced into each filled tray 18 such that it ends lies within the tray. A charge of a mixture of argon-rich gas is then dispensed over the surface of the meal 24 within the tray. The tray is then passed sequentially into a sealing apparatus 28 where a lid 30 of gas-impermeable plastic is heat sealed to the upper periphery of the tray. The sealed trays are then taken sequentially for further packaging.

The above packaging process is described schematically only. In practice, -6it would be more common for a charge of the gas mixture to be dispensed into the tray virtually at the same time as the lid 30 is heat sealed to the periphery of the tray. However, the apparatus required for this embodiment is conventional, the only difference being in the gas applied to the food. The apparatus is thus illustrated and described only schematically since it is well known to those skilled in the art.

As indicated previously, the atmosphere in contact with the product is argon-rich. Preferably, argon is present in the gas dispensed from the lance onto the prepared ready meal in a proportion of 65% to 100% by volume of the total gas mixture. More preferably, argon forms at least 70% by volume of the total gas mixture.

The balance of the gas mixture comprises carbon dioxide. The balance of the mixture may also comprise oxygen.

Examples of some typical gas mixtures are as follows (all proportions are by volume):

50% argon, 50% carbon dioxide 60% argon, 40% carbon dioxide 65% argon, 35% carbon dioxide 70% argon, 30% carbon dioxide 75% argon, 25 % carbon dioxide 80% argon, 20% carbon dioxide 90% argon, 10% carbon dioxide 70% argon, 20% carbon dioxide and 10% oxygen 65% argon, 25% carbon dioxide and 10% oxygen 60% argon, 30% carbon dioxide and 10% oxygen 50% argon, 40% carbon dioxide and 10% oxygen The invention includes all mixtures comprising at least 50% argon by volume with the balance comprising carbon dioxide andlor oxygen in proportions ranging from 0% to 50% by volume each. The mixture may comprise other gases instead of, or in addition to, those mentioned.

As a variation of the method illustrated, it will be appreciated that it would be possible for the ready meals to be assembled in their trays and for the meals then to pass directly to the packing line without undergoing a cooking or cooling step, as indicated by dotted line 32 in the Figure. Alternatively, and as indicated by line 34 in the Figure, the chilling step S 16 may be omitted. In either case, a chilling step 36 may be incorporated after the packing of the trayed meals.

Moreover, although the embodiment described suggests that the ingredients for the ready meal are placed into a container individually (prior to cooking if a cooking step is included) this need not be the case. For example, for a stew or hotpot type meal it is likely that a batch will be prepared (and probably cooked) prior to dispensing into individual containers.

The present invention is applicable to the preservation of any ready meal, whether uncooked, part-cooked or fully cooked. It is also applicable to the preservation of many other food products, in particular, but not exclusively, to constituents of ready meals. For example, some ready meals are prepared in separate portions of, say, rice and meat in a sauce which are required to be stored separately prior to final cooking or re-heating, in order to retain optimum colour and texture.

Examples of food products which may be preserved by the method of the invention include cooked or partiallycooked fresh pasta (with or without an accompanying sauce), meat lasagne or other pasta dishes. It is also applicable to freshly grated cheese (e.g. cheddar cheese), sliced ham and other cooked meats.

The invention is not restricted to the details of the foregoing embodiment.

Claims

-9CLAIMS

1. A method of preserving food, comprising enclosing the food in an argonrich environment in a substantially gas-impermeable container.

2. A method as claimed in claim 1, wherein the argon-rich environment comprises substantially 100% argon.

3. A method as claimed in claim 1, wherein the argon-rich environment further comprises one or more other gases in addition to argon.

4. A method as claimed in claim 3, wherein the argon-rich environment comprises argon and carbon dioxide.

5. A method as claimed in claim 4, wherein the argon-rich environment further comprises oxygen.

6. A method as claimed in any of the preceding claims, wherein an argonrich gas mixture is applied to the food.

7. A method as claimed in claim 6, wherein the gas mixture comprises substantially 100% argon.

8. A method as claimed in claim 6, wherein the gas mixture further comprises one or more other gases in addition to argon.

9. A method as claimed in claim 8, wherein the gas mixture comprises from 50% to 100% argon by volume.

10. A method as claimed in claim 9, wherein the gas mixture comprises at least 70% argon by volume.

11. A method as claimed in claim 10, wherein the gas mixture comprises from 70% to 90% argon by volume.

12. A method as claimed in claim 10, wherein the gas mixture comprises from 80% to 100% argon by volume.

13. A method as claimed in any of claims 8 to 12, wherein the gas mixture further comprises carbon dioxide.

14. A method as claimed in claim 13, wherein the gas mixture comprises from 10% to 40% carbon dioxide by volume.

15. A method as claimed in claim 14, wherein the gas mixture comprises from 20 to 30% carbon dioxide by volume.

16. A method as claimed in any of claims 8 to 15, wherein the gas mixture further comprises oxygen.

17. A method as claimed in claim 16, wherein the gas mixture comprises no more than 10% oxygen by volume.

18. A method as claimed in any of claims 8 to 17, wherein the gas mixture comprises at least 50% argon by volume, and the balance of the gas mixture comprises carbon dioxide andlor oxygen in proportions ranging from 0% to 50 % each.

19. A process of packaging food, comprising enclosing the food in a substantially gas-impermeable packaging, introducing an argon-rich gas into the packaging and scaling the packaging to enclose the argon-rich gas within the packaging.

20. A process as claimed in claim 19, wherein the argon-rich gas comprises substantially 100% argon.

21. A process as claimed in claim 19, wherein the argon-rich gas further comprises one or more other gases in addition to argon.

22. A process as claimed in claim 21, wherein the argon-rich gas comprises from 50% to 100% argon by volume.

23. A process as claimed in claim 22, wherein the argon-rich gas comprises at least 70% argon by volume.

24. A process as claimed in claim 23, wherein the gas mixture comprises from 70% to 90% by volume.

25. A process as claimed in claim 23, wherein the gas mixture comprises from 80% to 100% argon by volume.

26. A process as claimed in any of claims 21 to 25, wherein the argonrich gas further comprises carbon dioxide.

27. A process as claimed in claim 26, wherein the argon-rich gas comprises from 10% to 40% carbon dioxide by volume.

28. A process as claimed in claim 27, wherein the argon-rich gas comprises from 20% to 30% carbon dioxide by volume.

29. A process as claimed in any of claims 21 to 28, wherein the argonrich gas further comprises oxygen.

30. A process as claimed in claim 29, wherein the argon-rich gas comprises no more than 10% oxygen by volume.

3 1. A process as claimed in any of claims 21 to 30, wherein the argonrich gas comprises at least 50% argon by volume with the balance comprising carbon dioxide andlor oxygen in proportions ranging from 0% to 50% each.

32. A process as claimed in any of claims 19 to 31, wherein the food is cooked before being enclosed in packaging.

33. A process as claimed in claim 32, wherein the food is cooled before being enclosed in packaging.

34. A process as claimed in any of claims 19 to 32, wherein the food is cooled after being enclosed in packaging.

35. A method of preserving food, substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

36. A process for packaging food, substantially as herein described, with reference to, and as illustrated in, the accompanying drawings.