WO2010091856A2

WO2010091856A2 - Pre-cooked food manufacturing system

Info

Publication number: WO2010091856A2
Application number: PCT/EP2010/000839
Authority: WO
Inventors: Maurizio Vilona
Original assignee: Giardinetto Restaurants Ltd
Priority date: 2009-02-13
Filing date: 2010-02-11
Publication date: 2010-08-19
Also published as: GB0902478D0; WO2010091856A3; GB201002539D0

Abstract

An industrial method of preparing a pre-cooked food, wherein the method comprises the sequential steps of: a) cooking the food; b) portioning the food and packing each portion or multiple portions into a respective pack; c) creating a partial vacuum in the pack sufficient not only to prevent evaporation from the pack but also substantially remove all oxygen from the pack; d) heat treating the pack to pasteurise or sterilise it; and e) flash freezing/ chill blasting the pack.

Description

Pre-cooked food manufacturing system

TEXT OF THE DESCRIPTION

Field of the Invention

The present invention concerns improvements in and relating to preservation of cooked foods that may be stored in a freezer for lengthy periods of time and readied for eating simply by limited re-heating. It provides a method of manufacturing pre-cooked foods of any of the various food types including meat, fish, vegetables and pasta amongst others. The method may be used, inter alia, for making TV dinners/ microwave meals.

Background to the Invention

Pre-prepared/ pre-cooked frozen meals suitable for re-heating in a microwave oven or convection oven constitute a major sector of the modern food industry in the West and have a turn-over of billions of pounds annually in the UK and many billions of dollars in the USA.

The industrialised techniques for preparing micro-wave meals generally entail firstly processing the incoming food, cooking it, loading it as portions into individual meal trays and then flash freezing it. In the initial processing stage vegetables are washed on a conveyor and then put into a container and steamed or boiled briefly to blanch. Meat is trimmed of fat and cut up, poultry is washed and dressed and fish is cleaned, descaled and cut up. The meals are then prepared in bulk with the meat being flavoured, seasoned and then cooked in an oven. Vegetables may be mixed with flavouring and other ingredients and then cooked. Once all of the food is cooked it is ready to be packaged and is sent to the filling conveyor lines where empty meal trays pass under various filling machines and the cooked food is placed in the tray compartments with the amount of food placed on each tray being controlled to provide consistent portion size from one tray to the next. After a tray is completely filled with food, it next moves to the packaging station to be covered over with an aluminium foil or other cover

SUBSTITUTE SHEET (RULE 26) i layer. The food is packed tightly and a low quality partial vacuum is created sufficient simply to ensure that the container is airtight so that no evaporation takes place. From the tray loading station the dinners are moved to the freezing units for rapid freezing by one of three primary methods: cold air blast, direct liquid immersion and indirect contact with refrigerated plates. The cold air blast method is most often used and entails passing the food packs through refrigerated coils with fans blowing cold air around the trays at temperatures as low as -59° C, freezing the dinners instantly. As the dinners exit the freezing units, they are stacked, boxed and palleted and then kept in a freezer at -18° C during shipping and storage.

One of the alternative flash freezing techniques, cryogenic freezing, using liquid Nitrogen or CO₂ is a flash freezing technique of choice for some food items, such as seafood. In the case of liquid nitrogen this vaporizes when it comes in contact with a foodstuff and freezes the food instantaneously. In the case of liquid carbon dioxide, snow is formed when the liquid expands, and this snow is then vaporized on the product.

Despite their convenience and popularity microwave meals have come in for much bad press lately. They are generally less nutritious than fresh cooked food, often very high in salt and fat for preservation and to boost flavour lost in freezing, are usually heavily processed, and are formulated to remain edible after long periods of storage, thus often requiring unhealthy additives such as BHT ( butylated hydroxyl toluene). Attempts have been made in recent years to improve the processes and improve nutritional value but have not yet reached a point where the cooked and processed food is high in nutritional value yet safely storable for protracted periods of time of the order of a year or more without having to resort to use of the undesired additives. It is a general objective of the present invention to address these problems. It should be understood, however, that the scope of the present invention is not limited solely to TV dinners or microwave meals but may apply to any industrial process for preparing pre-cooked food .to be stored frozen for protracted periods of time before simply re-heating to eat.

Summary of the Invention According to a first aspect of the present invention there is provided an industrial method of preparing a pre-cooked food, wherein the method comprises the sequential steps of: a) cooking the food; b) portioning the food and packing each portion or multiple portions into a respective pack; c) creating a partial vacuum in the pack sufficient not only to prevent evaporation from the pack but also substantially remove all oxygen from the pack ; d) heat treating the pack to pasteurise or sterilise it; and e) flash freezing/ chill blasting the pack.

In a further embodiment, a step f) of chill blasting the food is provided after the step of cooking the food and before the step of portioning and packing the same food; this step is carried out especially if high in liquid content, soft or otherwise vulnerable to compaction to increase its density and improve its stability in handling.

Advantageously, in another embodiment of the present invention the process comprise a further final step g) of maintaining the pack for a given period of time at a temperature lower than -40⁰C, and preferably lower than -50°C, more preferably in a range between -5O⁰C and -70°C. The period of time may be from 12 hours to several days, and particularly is comprised between one day and three months. By this way the bacterial load of the food is substantially deleted and the food could be preserved for long periods of time without a significant loss of nutritional and organoleptic properties. In step a) the cooking of the food may comprise any form of cooking including, for example, steaming, roasting, frying or boiling, and cooking under increased pressure or partial vacuum and by convection, microwave or other ovens. It may even involve alternatives to cooking by heat, such as use of air-, salt- or smoke- curing, Maillard browning or otherwise treating of meat, fish or vegetables in a way that modifies the liquid retention or the nature or amount of protein, fiber, starch, fat or other key nutritional content of the foodstuff.

When flash freezing/ chill blasting the pack in step e) this is preferably done by cryo-freezing with liquid nitrogen or liquid carbon dioxide, and in the latter case down to temperatures of -18°C and suitably -23°C and below. In the optional step f) the chill blasting is done at a temperature that allows the portioning and vacuum packing to be carried out and which suitably is at or around 0⁰C to 5°C, preferably 3°C. This step helps to avoid possible steam contamination of an oil operated vacuum pump when evacuating the tray and it is especially suitable if the food is high in liquid content, soft or otherwise vulnerable to compaction and serves to increase its density and improve its stability in handling for portioning and vacuum-packing. It is particularly useful for foods like pasta that are liable to compact into block-form like cement if subject to vacuum packing. For pasta the subsequent re-heating of the vacuum-packed frozen product does not lead to cementing since the time to re-heat is very short the vacuum compression has no opportunity to interact with the starch content to cause gluing to occur.

In a variant of the process that is unsuitable for many foodstuffs but may be adequate for a more limited range of foodstuffs where crystallisation is less of a problem or for manufacturers with more limited resources, the flash freezing/ chill blasting of the food in step f) or the pack in step e) may be replaced by freezing in a freezer /freezing chamber (not flash freezing) to -18°C or below in a more leisurely fashion over time. Nevertheless, flash freezing in step e) is superior to slower freezing for the purposes of the present invention since it increases thermal shock thus reducing bacterial contamination.

In step b) the portioning of the food suitably entails dividing the food into portions, preferably while maintained at a temperature of about O⁰C to 5°C if the food was chill-blasted in a step f). The portions are defined as being intended for eating by one person in one meal or as comprising a mass of no greater than 70Og and preferably no greater than 50Og per portion and particularly preferably of the order of 200 to 30Og per portion. The portions may each comprise a single foodstuff or ingredient or several ingredients as a recipe or as a meal. The pack may be a sealed tray, bag or a can or any other pack/ vessel provided that it is suitable for vacuum-packing being of suitable material, shape and configuration to ensure an effective airtight seal and to maintain the required quality of vacuum, ie vacuum that is substantially free of oxygen. The packs may be transparent to view their contents. Preferred vacuum-packing bags and machinery are those manufactured by Orved AS of Verona Italy, which were designed vacuum pack storage and subsequent sous vide cooking of raw meat etc but which suit the purpose of the present invention. Orved AS hold a number of patents on their technology including GB 2, 211 , 161.

In step c) the partial vacuum in the pack is deemed suitable at least 95% vacuum (at most about 5 kPa) and preferably at least 97% vacuum (at most about 5 kPa). Particularly preferably the partial vacuum is 99% vacuum, 99.9% vacuum or greater (1 kPa or less or 0.1 kPa or less) to the limits of vacuum packing technology. Orved's Cuisson SV41 , for example, achieves final pressures of the order of 0.5 mbar (99.95% vacuum). In step d) the pack is preferably pasteurised under suitable lower temperature, longer time pasteurisation conditions for food such as, for example, of the order of 85⁰C for 6 minutes rather than of the order of 110⁰C for 3 minutes. This reduces the energy burden to sequentially heat and then cool the product in steps d) and e). Alternatively the package may be subjected to heating conditions traditionally used to ensure full sterilisation. Even simply using the proposed lower temperature, longer time pasteurisation conditions has been found to be sufficient, when in the context of our process, to substantially eradicate bacteria, reducing the bacterial load to under 5,000 cfu per gram and which is far below the minimum 800,000 cfu per gram standard accepted by EU food regulation authorities. Specific pathogenic bacteria such as E. coli, C simpliciter, and Salmonella were generally under 100 cfu per gram or at such low levels as to be undetectable using standard laboratory test equipment.

The organoleptic qualities and colour of the food are exceptionally good and very close to that of freshly cooked food and the frozen shelf-life of the food is extended far beyond the norm without need of additional preservatives of any sort. The food prepared according to the process of the present invention may be stored for periods of as a much as a year or more but, like other frozen ready meals can be re-generated to cooked food/ meal state ready for eating within a matter of minutes using any of the conventional means such as microwave or convection oven, boil-in-bag, steam cooking or indeed any suitable heating means.

The steps of the manufacturing process that entail re-heating to pasteurise or sterilise followed by flash freezing gives rise to an exceptionally steep temperature fall in a short period of time. It is thought that this is a significant factor contributing to successfulness of the present invention in providing exceptionally low bacterial count, good organo-leptic qualities and giving exceptionally long analytic life/ frozen storage life. The combination of pasteurisation or sterilisation in vacuum and subjecting the vacuum-packed food to abrupt thermal shock by directly flash freezing is unique. According to a second, more general, aspect of the present invention there is provided an industrial method of preparing a pre-cooked food, wherein the method comprises the sequential steps of: a) cooking the food; b) portioning the food and packing each portion or multiple portions into a respective pack; c) creating a partial vacuum in the pack sufficient not only to prevent evaporation from the pack but also substantially remove all oxygen from the pack ;and d) flash freezing/ chill blasting the vacuum pack.

The method of the present invention provides a unique method of preparing a pre-cooked ready meal or food item that is re-generable simply by brief heating in a micro-wave oven or by any heating means and extends to a wide range of activities and products in the food industry. The process could even be used in preparation of frozen pizzas or frozen sandwiches. The sandwich filling or indeed any part of the frozen food or meal may be cooked, cured etc on-site or elsewhere first and then steps b) to d) above are followed. Whatever the end product, the process allows for preparation in relatively confined areas and can require minimal storage and gives immense benefits in food quality and longevity and can greatly reduce overall costs despite the combination of energy input stages involved in the process. That combination of energy inputs has no doubt been responsible for prejudicing the food industry against exploring a process such as that of the present invention in the past but it has considerable benefits as we have now discovered. Some examples of the invention will now be described. Uncooked sauces. ( walnut sauce, pesto, gazpacho, cimichurry)

1) Emulsions of the sauces were made in a vacuum blender machine

2) Each sauce was portioned, bagged and vacuum sealed at max. vacuum pack machine setting obtainable (99.9% on Orved AS machine)

3) The bagged sauces under vacuum were pasteurised for 4 minutes at 82°C

4) The bags were then Nitrogen chillblasted and then stored in freezers at -18⁰C

Cooked sauces ( tomato, marinara, ragout)

1) Emulsion and cooking was done in a vacuum blender machine

2) The sauces were then Nitrogen chill blasted in the vacuum machine for densification 3) Then bagged and vacuum sealed in vacuum at max vacuum setting

4) Then Pasteurized in vacuum for 6 minutes at 86°C

5) The bags were then Nitrogen chillblasted and then stored in freezers at -18°C

Braised meat and/or meat with long fibre tissue 1) The meat was Maillard browned

2) Then chill blasted to above freezing temperature

3) Then vacuum packed as whole pieces/ joints

4) Then cooked for 12 to16 hrs at 62 to 86°C according to size

5) Then chill blasted to above freezing and portioned 6) Then filled into bags with sauce, the vacuum machine at max setting

7) Then pasteurized in vacuum for 12 minutes at same temp as max cooking temperature (i.e. 62°C if the cooking temperature was 62⁰C)

8) Then chill blasted and then stored in freezers at -18°C

Pasta ( troffiette al pesto) 1) The pasta was cooked in salted water for half cooking time

2) Then placed in a portioning tray with pesto

3) Then vacuum packed at max obtainable vacuum

4) Then pasteurized at 90⁰C for 1 minute 5) Then Nitrogen chillblasted and then stored in freezers at -18°C

Time and temperature may vary within normal cooking or pasteurisation limits according to nature and quality of ingredients. In each of the tested cases bacterial load of final product was negligible, projected freezer-life of product was far beyond that of conventional manufacturing processes and the colour and organoleptic quality of the product was exceptionally good. Some data sheets follow after the claims, in lieu of drawings sheets, showing test results for tagliatelle, for tagliolini rossi and for zucchini-peperoni including microbiological data and protein, lipid and carbohydrate content.

Claims

1. An industrial method of preparing a pre-cooked food, wherein the method comprises the sequential steps of: a) cooking the food; b) portioning the food and packing each portion or multiple portions into a respective pack; c) creating a partial vacuum in the pack sufficient not only to prevent evaporation from the pack but also substantially remove all oxygen from the pack ; d) heat treating the pack to pasteurise or sterilise it; and e) flash freezing/ chill blasting the pack.

2. An industrial method as claimed in claim 1 , in which a step f) of chill blasting the food is provided after the step a) of cooking the food and before the step b) of portioning and packing the same food.

3. An industrial method as claimed in claim 1 , wherein flash freezing/ chill blasting the pack in step e) is done by cryo-freezing with liquid nitrogen or liquid carbon dioxide down to temperatures of -18⁰C and below.

4. An industrial method as claimed in claim 2, wherein in step f) the chill blasting is done at a temperature that allows the portioning and vacuum packing to be carried out and which in a range between 0⁰C and 5°C.

5. An industrial method according to anyone of the preceding claims 1 to

4, wherein in step c) the portioning of the food entails dividing the food into portions having a mass of no greater than 70Og.

6. An industrial method according to anyone of the preceding claims 1 to

5, wherein the pack is a sealed tray, bag or a can or any other vessel that it is suitable for vacuum-packing being of suitable material, shape and configuration to ensure an effective airtight seal and to maintain the required quality of vacuum.

7. An industrial method according to anyone of the preceding claims 1 to 6, wherein in step c) the partial vacuum in the pack is an at least about 95% vacuum (5 kPa or less).

8. An industrial method as claimed in claim 7, wherein in step c) the partial vacuum in the pack is a 99% vacuum or greater (1 kPa or less).

9. An industrial method according to anyone of the preceding claims 1 to 8, wherein in step d) the pack is pasteurised under pasteurisation conditions for food where the temperature is of the order of 85⁰C or less.

10. An industrial method according to anyone of the preceding claims 1 to 8, wherein in step d) the pack is subjected to heating conditions used to ensure full sterilisation where the temperature is of the order of 100⁰C or more.

11. An industrial method according to anyone of the preceding claims 1 to 10, wherein the food is pasta and the pasta is subjected to step f) prior to step b).

12. A method of preparing a pre-cooked food, wherein the method comprises the sequential steps of: a) cooking the food; b) portioning the food and packing each portion or multiple portions into a respective pack; c) creating a partial vacuum in the pack sufficient not only to prevent evaporation from the pack but also substantially remove all oxygen from the pack ;and e) freezing or flash freezing/ chill blasting the vacuum pack.

13. A method according to anyone of the preceding claims 1 to 12, in which is further provided final step g) of maintaing the pack for a given period of time at a temperature lower than -4O⁰C.

14. A method according to claim 13, in which the said maintening temperature is in a range beween -50⁰C and -7O⁰C.

15. A method according to claim 13 or 14, in which the period of time may be from 12 hours to several days.

16. A method according to claim 15, in which the period of time is comprised between one day and three months.