WO2017133899A1

WO2017133899A1 - Packaged food product

Info

Publication number: WO2017133899A1
Application number: PCT/EP2017/051122
Authority: WO
Inventors: Gaëlle Marie Laure SCHLUP-OLLIVIER; Yves Wyser; Fernand BEAUD; Mireille THERAULAZ; Jean-Marc GRIMAUX; Amira KASSIS
Original assignee: Nestec S.A.
Priority date: 2016-02-01
Filing date: 2017-01-19
Publication date: 2017-08-10

Abstract

A method for manufacturing a packaged food product, said method comprising the steps of: (a) providing raw food ingredients combined in a pouch, wherein said pouch is liquid-impermeable and gas-impermeable; (b) sealing the pouch; and (c) subjecting the sealed pouch to a high-pressure heat treatment comprising a temperature of at least 122°C and a pressure of at least 2 bar, for a duration of at least 15 minutes.

Description

Packaged food product

FIELD OF INVENTION The present invention relates to packaged food products and methods for their manufacture. In particular, the invention relates to packaged food products that are suitable for long-term storage.

BACKGROUND

Packaged food products are popular for their convenience and storage properties. Packaged food products are often used to provide pre-prepared foods that simply require re-heating before they can be consumed. Examples of packaged food products include such common products as canned soup and pre-prepared meals in pouches (for example, risotto). Such pre- prepared meals are popular both with individual consumers, who may lack the time to prepare a meal from raw ingredients, and with organisations such as airlines, who have a need to prepare nutritious meals for passengers in a short timeframe using the limited facilities available on an aeroplane. Traditionally, canning techniques were used to prepare packaged food products the contents of which could be stored and re-heated at a later date. More recently, it has become popular to use flexible pouches instead of metal cans. Such pouches are often referred to as "retort pouches" due to the retorting process of heating at high temperature that may be used to sterilise them. To ensure that packaged food products may be safely stored prior to use, it is necessary to treat the food contents to ensure that any microorganisms that could cause food spoilage are reduced in number or destroyed entirely. Treatment methods used will depend on the desired storage conditions and duration. For example, short term storage of several days under refrigerated conditions (approximately 3-5°C) requires only that microorganisms in the food are reduced in number, as the cold temperatures will serve to inhibit their growth and reproduction. By contrast, storage under warmer conditions, such as at room temperature (approximately 20- 25°C), may require effectively all microorganisms to be destroyed. Treatment methods used in food preservation may include acidification to reduce the pH of the food to a level that does not support microbial growth, and/or heat treatments such as pasteurisation or sterilisation that can destroy microorganisms. Pasteurisation involves the application of heat to kill a majority (but not all) of microorganisms present in the food, leaving the food suitable for storage under refrigerated conditions. A common usage of pasteurisation is to treat milk. Typically, a pasteurisation process will heat a food to a temperature of at least 71°C for at least one minute. Pasteurisation may be carried out by heating a sealed container of food in a water bath at about 82-99°C for about to 10-40 minutes. An example pasteurisation process is described in US 2004/0156960.

In contrast to pasteurisation, sterilisation is intended to kill all microorganisms present in the food, leaving it suitable for long-term storage at room temperature. Sterilisation processes using heat therefore involve significantly higher temperatures than pasteurisation. A number of different methods are available for producing sterile packaged food products. By way of example, a pre-prepared food product (such as a cooked meal) may be subjected to a sterilisation process and then packaged in a sterile container in a clean-room type environment. However, the preservation of sterile conditions in a clean-room is laborious and costly. A commonly used method of preparing a packaged food product in a pouch is to pre-cook ingredients such as meat and vegetables before combining them in the pouch, which is subsequently sealed. The filled and sealed pouch then undergoes a separate heat treatment step to sterilise both the pouch and its contents. Such a step may be carried out using high-pressure steam in a retort or autoclave. This method however has a number of disadvantages. In particular, sterilisation of the filled pouch in this manner means that the cooked food contents are subjected to an additional period of high temperature, which can have deleterious effects on the taste, texture and other organoleptic properties of the food. This in turn can make it necessary to add additional chemical flavourings to the food to try and compensate for these problems.

GB 2423690- A describes a method for obtaining food goods packed in pouches that are stable at room temperature. The method comprises steps of providing raw food ingredients such as beef and tomatoes, cooking said ingredients, placing the cooked ingredients into a plastic container such as a pouch, sealing the pouch, and sterilising the sealed pouch using an autoclave. While the final product may be stored at room temperature, the combination of a pre-cooking step and a subsequent heat sterilisation step will have deleterious effects on the food as outlined above.

US 2004/0156960 describes a food product preservation method. The method comprises steps of placing a food product in a sealable, heat stable container; adding an amount of an edible acid to the container to achieve a pH of less than 5 in the preserved food product; sealing the container; thermally treating the food product in the sealed container at a temperature of approximately 82-99°C for 10-40 minutes to pasteurise the food product; cooling the thermally treated food product; and storing the cooled food product under refrigerated conditions to obtain the preserved food product. While a pre-cooking step is not required, the final product is not suitable for storage at room temperature and requires cooking before use. WO 00/19830 describes a sealed cooking pouch which includes a frozen portion of raw protein and raw or partially cooked vegetables. The pouch is suitable for storage in a freezer only (i.e. at temperatures below 0°C), and is designed to be heated by the consumer in a microwave or conventional oven in order to cook the contents for immediate consumption. In order to prevent excessive pressure build-up in the pouch during the cooking process, steam is released through a pinhole sized opening formed in one seam of the pouch during the manufacturing process.

There is therefore a need in the art for alternative and/or improved methods of producing packaged food products that address the above prior art problems.

SUMMARY OF THE INVENTION

The present invention solves the above prior art problems by providing methods for manufacturing packaged food products, as specified in the claims.

In one aspect, the invention provides a method for manufacturing a packaged food product, said method comprising the steps of: (a) providing raw food ingredients combined in a pouch, wherein said pouch is liquid- impermeable and gas-impermeable; (b) sealing the pouch; and (c) subjecting the sealed pouch to a high-pressure heat treatment comprising a temperature of at least 122°C and a pressure of at least 2 bar for a duration of at least 15 minutes.

The packaged food product may be suitable for storage at room temperature for at least 8 weeks, at least 10 weeks or at least 12 weeks. For example, the packaged food product may be suitable for storage at room temperature for about 10 weeks, about 11 weeks or about 12 weeks.

The high-pressure heat treatment may comprise a temperature of at least 122°C, at least 123°C, at least 124°C or at least 125°C. For example, the high-pressure heat treatment may comprise a temperature of about 122°C, about 123°C, about 124°C or about 125°C. The high-pressure heat treatment may comprise a pressure of at least 2 bar, at least 2.5 bar or at least 3 bar. For example, the high-pressure heat treatment may comprise a pressure of about 2 bar, about 2.5 bar or about 3 bar.

The high-pressure heat treatment preferably has duration of at least 20 minutes. For example, the high-pressure heat treatment may have a duration of about 20 minutes.

In a particularly preferred embodiment, the high-pressure heat treatment comprises a temperature of at least 122°C and a pressure of at least 2.5 bar for a duration of at least 20 minutes. For example, the high-pressure heat treatment may comprise a temperature of about 122°C and a pressure of about 2.5 bar for a duration of about 20 minutes.

In one embodiment, the high-pressure heat treatment simultaneously cooks and sterilises the raw food ingredients. Preferably, the sealed pouch is subjected to a single high-pressure heat treatment.

Preferably, the high-pressure heat treatment is a high-pressure steam treatment.

In one embodiment, the raw food ingredients do not comprise any preservatives apart from salt and/or sugar.

Preferably, the raw food ingredients have not been subjected to any acidification treatment.

In one embodiment, the pH of the combined raw food ingredients is 4 or greater (e.g. about 4, about 5, about 6, or about 7).

The raw food ingredients may be provided at, for example, a temperature above 0°C (e.g. about 5°C, about 10°C, about 15°C, about 20°C, or about 25°C).

In one embodiment, the raw food ingredients are provided at room temperature (e.g. about 20- 25°C). In another aspect of the present invention, there is provided a packaged food product obtainable by the method of the invention as described above.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing a packaged food product, said method comprising the steps of: (a) providing raw food ingredients combined in a pouch, wherein said pouch is liquid- impermeable and gas-impermeable; (b) sealing the pouch; and (c) subjecting the sealed pouch to a high-pressure heat treatment comprising a temperature of at least 122°C and a pressure of at least 2 bar, for a duration of at least 15 minutes. The resultant packaged food product is preferably suitable for storage at room temperature for at least 8 weeks. The present inventors have discovered that a packaged food product can be prepared by sealing raw food ingredients in a pouch and subjecting the pouch to a single heat treatment using specific high temperatures and pressures. The single heat treatment simultaneously cooks and sterilises the food in the pouch, thus avoiding the need for any pre-cooking or other pre- treatment steps (such as acidification). Advantageously, the inventors have discovered that use of a single heat treatment step in this fashion retains desirable tastes, textures and other organoleptic properties of the food, thus avoiding the need to add additional chemical flavourings. By not requiring any pre-cooking or other pre-treatment steps, the method of the invention also advantageously provides a more efficient method of preparing a packaged food product, thus reducing associated costs.

In the method of the invention, raw food ingredients are combined to form a food preparation in a pouch. As used herein, the term "raw" means that the food ingredients have not been cooked, partially cooked (e.g. blanched or parboiled), or subjected to any other heat treatment prior to their use in the method of the invention. The raw ingredients may undergo processing steps such as chopping and mixing prior to being combined in the pouch. Suitable food processing techniques that do not involve the application of heat will be familiar to a skilled person, and may include cutting, chopping, slicing, dicing and mixing of raw ingredients. In one embodiment, the raw food ingredients have not undergone any preservation or curing process such as salting, drying, smoking or pickling prior to their use in the method of the invention.

The method of the invention is suitable for use with all standard food retort pouches used in the art. Such pouches are typically flexible and made of plastic or metal foil, or a combination of both, and are liquid-impermeable and gas-impermeable. As used herein, "liquid- impermeable" and "gas-impermeable" mean that the pouches, once sealed, are highly resistant to the exit or ingress of any liquid or gases, as well as microorganisms, which is a requirement to ensure that the contents remain sterile once heat-treated.

A pouch may be a laminate of several layers. An example of a laminate pouch features (from inside to outside): a polypropylene inner layer, providing a flexible, chemically-resistant surface in contact with the food, and which can also be heat-sealed; a nylon layer providing abrasion-resistance; an aluminium foil layer, providing an impermeable barrier to protect the food from external light and gases as well as contaminating microorganisms; and a polyester outer layer providing strength and a printable surface. The pouch according to the method of the invention may be a self-heating container, for example as described in GB2372492 or W09749319.

As the filled pouch will undergo a sterilisation treatment, the method of the invention does not require that pouches are pre-sterilised and filled under clean-room conditions. This therefore advantageously reduces the complexity of the facilities required to prepare a packaged food product of the invention.

Once filled with the raw food ingredients, the pouches are sealed. The sealing step provides a hermetic seal. The step of sealing the pouches may be accomplished using any suitable technique known in the art, for example the application of heat to fuse the open ends of the pouch together. Once sealed, the contents of the pouch are isolated from the external environment, ensuring that the contents of the finished packaged food product will remain sterile during storage. The filled and sealed pouches are subjected to a high-pressure heat treatment comprising a temperature of at least 122°C and a pressure of at least 2 bar, for a duration of at least 15 minutes.

The present inventors have discovered that a high-pressure heat treatment using these specific parameters can be used to simultaneously cook and sterilise the raw food ingredients in the pouch. This has the advantage that pre-cooking of the food ingredients is not required, thus simplifying the manufacturing process. Furthermore, as discussed above, subjecting foods that have undergone a pre-cooking step before incorporation into a pouch or other container to a further heat-treatment step as part of a sterilisation process, has deleterious effects on organoleptic properties such as taste, texture and smell. However, through testing, the present inventors have discovered that when raw food ingredients are cooked and sterilised in a pouch in a single step using the method of the invention, the resultant food product has significantly improved organoleptic properties. In more detail, testing has established that food products of the invention retain desirable organoleptic properties that are otherwise lost when pre-cooked foods are subjected to a high- pressure heat treatment. Food products of the invention have a desirable "natural" flavour that does not require the presence of additional, artificial chemical flavourings.

A further advantage of the method of the invention is that it allows for the increased retention of vitamins and minerals in the food product. Pre-cooking steps may lead to nutritionally- important vitamins and minerals leaching out of food and being lost before the food is packaged. For example, cooking vegetables through boiling can lead to vitamins and minerals leaching into the boiling water; these are lost when the water is discarded at the end of the boiling process. By contrast, by using a single combined cooking and sterilisation step, the method of the invention ensures that all vitamins and minerals are captured in the pouch and thus retained in the food product. Accordingly, food products of the invention may have improved nutritional properties.

Yet a further advantage of the method of the invention is that it provides for increased sustainability by reducing energy and water consumption. The absence of a pre-cooking step means a saving in terms of the energy and water usage that would otherwise be required for such a step. Furthermore, packaged food products of the invention may be stored for long periods without requiring freezing or refrigeration, and therefore provide for considerable energy savings during storage.

The high-pressure heat treatment used in the method of the invention comprises a temperature of at least 122°C (for example, at least 123, 124 or 125°C) and a pressure of at least 2 bar (for example, at least 2.5 or 3 bar), for a duration of at least 15 minutes (for example, at least 20, 25 or 30 minutes). The duration may be, for example, 15-30 minutes, 15-25 minutes, 15-20 minutes or 20-25 minutes). These conditions represent minimum acceptable parameters to ensure complete sterilisation of raw food ingredients. The resultant packaged food product is preferably suitable for storage at room temperature for at least 10 weeks. The use of temperatures, pressures or durations less than the above values may not guarantee sterilisation (and thus represents a safety risk to the end user) of raw food ingredients that have not been subjected to additional treatment steps to reduce microorganism levels (such as an acidification treatment to reduce pH levels of the food product). Thus, the method of the invention is advantageously suitable for food preparations that have not been subjected to any acidification treatment. By way of example, the pH of a food preparation that has not been subjected to any acidification step may be 4 or greater (for example, 4, 4.5, 5, 5.5, 6, 6.5, or 7). An example of an acidification treatment is the addition to a food preparation of an acid such as citric acid.

The present inventors have found that particularly advantageous results can be achieved when the high-pressure heat treatment comprises a temperature of at least 123°C, a pressure of at least 2.5 bar, and/or a duration of at least 20 minutes. Thus, in one embodiment, the high- pressure heat treatment comprises a temperature of at least 123°C and a pressure of at least 2.5 bar, for a duration of at least 20 minutes.

Methods for subjecting a sealed pouch to a high-pressure heat treatment are well known in the art and would be familiar to a skilled person. By way of example, a high-pressure heat treatment may be a high-pressure steam treatment. Such a treatment is commonly applied using a retort or autoclave; these devices apply saturated steam at high pressures and temperatures in order to sterilise items. Thus, in a related embodiment, the high-pressure heat treatment is an autoclave treatment. As discussed above, the method of the invention obviates the need to include additional preservatives in the food product (with the exception of salt (sodium chloride) and/or sugar (sucrose), which may be present for reasons of taste), thus simplifying the production process. In addition, the absence of additional, artificial flavourings or preservatives in a food product can be perceived by consumers as desirable.

The packaged food products produced according to the method of the invention are preferably suitable for storage at room temperature for at least 8 weeks (for example, at least 10, 11, 12, 13, 14, 15 or 16 weeks; or at least 2 months; or at least 3 months; or at least 4 months). As used herein, "suitable for storage" means that the packaged food product may be stored for the indicated time and at the indicated temperature without undergoing spoilage. As used herein, "room temperature" means a temperature of between 20 and 25°C, preferably about 20°C. Thus, after being stored for at least 8 weeks at room temperature, the contents of a packaged food product of the invention remain edible with good organoleptic properties and without microorganism contamination. Packaged food products of the invention can therefore advantageously be stored for long periods without requiring freezing or refrigerating.

The contents of a packaged food product of the invention may be prepared for consumption by an end user by re-heating, for example in an oven (e.g. a conventional oven or a microwave oven) or by the application of direct heat, such as by using a pan on a stove.

The method of the invention is suitable for application to many different types of raw food ingredients, such as meat, fish, vegetables, mushrooms and other edible fungi, rice, and pasta. Suitable meats include beef, lamb, pork and poultry (e.g. chicken, duck, goose, turkey). Examples of suitable fish include cod, haddock, mackerel, salmon, and trout, and also crustaceans such as crab, lobster, and shrimp. Examples of suitable vegetables include aubergine, beetroot, beans (e.g. broad beans, green beans, haricot beans, runner beans), broccoli, cabbage, carrots, cauliflower, celery, cucumber, garlic, leeks, lettuce, onion, parsnip, peas, peppers, potatoes, radishes, swede, sweetcorn, sweet potato, and tomatoes. In one embodiment, the raw food ingredients do not comprise rice.

The method of the invention is suitable for application to a porridge or pap. A porridge is a dish made by boiling ground, crushed, or chopped starchy plants - typically grain - in water or milk. For example the method of the invention is suitable for application to a porridge of grains with water or milk. Milk may for example be whole milk, skimmed milk, soy milk, coconut milk, cream, evaporated milk, or combinations thereof. The porridge may further contain ingredients to enhance the sweetness of the porridge (sweetening agents) such as sugar, brown sugar, honey, sweetened condensed milk, fruit, syrups, artificial sweeteners, or combinations thereof. The grains in the porridge may be so-called ancient grains such as sorghum, teff, millet, quinoa or amaranth. The grains in the porridge may be oats. The high- pressure heat treatment in the method of the invention may simultaneously cook and stabilize the raw food ingredients, for example stabilize the raw food ingredients by deactivating enzymes. Undesirable flavours may form in oat-containing products due to lipid hydrolysis. The high pressure treatment of the invention may deactivate enzymes such as lipase and lipoxygenase and so prevent or reduce the formation of off flavours.

The raw food ingredients may be combined with probiotic micro-organisms in the method of the invention. The health benefits of probiotics are well accepted in the art and were summarized, e.g., by Blum et al. in Curr Issues Intest Microbiol. 2003 Sep;4(2):53-60. Oftentimes probiotics are administered together with prebiotics in symbiotic formulations which may even have enhanced health benefits. In one embodiment of the present invention, the probiotic micro-organisms may be non-replicating probiotic micro-organisms. The probiotic micro-organisms may be rendered non-replicating by the high-pressure heat treatment of the method of the invention. By using a single combined step to cook raw food ingredients and render any probiotics non-replicating, the method of the invention provides a saving in terms of the energy and ensures that all probiotics are captured in the pouch and thus retained in the food product.

Non-replicating probiotics can provide the health benefits of probiotics and may even have improved benefits. The amount of non-replicating micro-organisms in the packaged food product of the method of the invention may correspond to about 10⁶ to 10¹² cfu per pouch. Obviously, non-replicating micro-organisms do not form colonies, consequently, this term is to be understood as the amount of non-replicating micro-organisms that is obtained from 10⁴ and 10¹² cfu/g replicating bacteria. This includes micro-organisms that are inactivated, nonviable or dead or present as fragments such as DNA or cell wall or cytoplasmic compounds. In other words, the quantity of micro-organisms which the composition contains is expressed in terms of the colony forming ability (cfu) of that quantity of micro-organisms as if all the microorganisms were alive irrespective of whether they are, in fact, non-replicating, such as inactivated or dead, fragmented or a mixture of any or all of these states.

"Non-replicating" probiotic micro-organisms include probiotic bacteria which have been heat treated. This includes micro-organisms that are inactivated, dead, non-viable and/or present as fragments such as DNA, metabolites, cytoplasmic compounds, and/or cell wall materials.

"Non-replicating" means that no viable cells and/or colony forming units can be detected by classical plating methods. Such classical plating methods are summarized in the microbiology book: James Monroe Jay, Martin J. Loessner, David A. Golden. 2005. Modern food microbiology. 7th edition, Springer Science, New York, N.Y. 790 p. Typically, the absence of viable cells can be shown as follows: no visible colony on agar plates or no increasing turbidity in liquid growth medium after inoculation with different concentrations of bacterial preparations ('non replicating' samples) and incubation under appropriate conditions (aerobic and/or anaerobic atmosphere for at least 24h). Probiotics are defined for the purpose of the present invention as "Microbial cell preparations or components of microbial cells with a beneficial effect on the health or well-being of the host." (Salminen S, Ouwehand A. Benno Y. et al "Probiotics: how should they be defined" Trends Food Sci. Technol. 1999: 10 107-10). The raw food ingredients may be combined with prebiotics in the method of the invention. The pouch may comprise an amount of probiotics corresponding to an amount of at least 10³ cfu per g of prebiotic, preferably 10⁴ to 10⁷ cfu/g of prebiotic, for example. "Prebiotic" means food substances that promote the growth of probiotics in the intestines. They are not broken down in the stomach and/or upper intestine or absorbed in the GI tract of the person ingesting them, but they are fermented by the gastrointestinal microflora and/or by probiotics. Prebiotics are for example defined by Glenn R. Gibson and Marcel B. Roberfroid, Dietary Modulation of the Human Colonic Microbiota: Introducing the Concept of Prebiotics, J. Nutr. 1995 125: 1401- 1412.

The prebiotics that may be used in accordance with the present inventions are not particularly limited and include all food substances that promote the growth of probiotics in the intestines. Preferably, they may be selected from the group consisting of oligosaccharides, optionally containing fructose, galactose, mannose; dietary fibers, in particular soluble fibers, soy fibers; inulin; or mixtures thereof. Preferred prebiotics are fructo-oligosaccharides (FOS), galacto- oligosaccharides (IOS), isomalto-oligosaccharides, xylo-oligosaccharides, oligosaccharides of soy, glycosylsucrose (GS), lactosucrose (LS), lactulose (LA), palatinose-oligosaccharides (PAO), malto-oligosaccharides (MOS), gums and/or hydrolysates thereof, pectins and/or hydro lysates thereof. Typical examples of prebiotics are oligo fructose and inulin.

A number of different raw food ingredients may be combined in order to produce a complete meal. Examples of meals that may be provided using the method of the invention include curry, gratin, goulash, soup, stew, and risotto; further examples include minced meat Parmentier, eggplant and tomatoes risotto, vegetable mousse, tuna mousse, tuna pasta, and Bolognese pasta. Other food products may also be produced, for example sauces (e.g. Bolognese sauce).

The method of the present invention is suitable for use with foodstuffs that have a liquid component (e.g. a liquid water component). Liquid water may also be added to the raw food ingredients during preparation steps prior to the filling of the pouches. Thus, in one embodiment the combined raw food ingredients comprise liquid water.

In one embodiment, the raw food ingredients are provided at a temperature above 0°C (e.g. 5, 10, 15, 20 or 25°C). In another embodiment, the raw food ingredients are provided at room temperature (for example 20-25°C). Because the high-pressure heat treatment step of the method of the invention simultaneously cooks and sterilises the raw food ingredients for storage at room temperature, the use of frozen ingredients may be unnecessary. In a further aspect, the invention provides a packaged food product obtainable by the above described method.

Those skilled in the art will understand that they can freely combine all features of the present invention described herein without departing from the scope of the invention as disclosed.

Description of Figures

Figure 1 presents a flow-chart showing an example process according to the method of the invention.

Examples

Various preferred features and embodiments of the present invention will now be described by way of non-limiting examples.

Example 1

Four different types of packaged meal were prepared according to the method of the invention:

Meal 1, Mushroom Risotto: bottom mushrooms; dried Boletus; plain rice; cooked white wine; shallots; vegetable and mushroom stock; olive oil; salt; white and black pepper. Meal 2, Potato Gratin: potatoes; milk; cream 35% fat; salt; black and white pepper; potato starch; Swiss cheese.

Meal 3, Thinly-sliced chicken and vegetables: tender parts of chicken; black olives; tomato; zucchini; olive oil; paprika powder; cream 35%> fat; white wine; plain rice; black and white pepper; chicken and vegetable stock.

Meal 4, Hungarian Goulash: potato; beef paleron; wheat flour; onion; tomato; garlic; bell pepper; olive oil; tomato concentrate; paprika; cooked red wine; salt; black and white pepper Each type of meal was stored at 4, 20 or 42°C and subsequently re-heated and assessed for organoleptic properties after 0, 6, 10, 11, 12 or 13 weeks storage. Testing showed that each type of packaged food product had acceptable organoleptic qualities after storage at 20°C for at least 10 weeks.

Results

Meal 1 : Mushroom risotto.

Storage 0 weeks 6 weeks 10 weeks 11 weeks 12 weeks 13 weeks temperature

4°C Very soft Soft texture Soft texture Soft texture Soft texture Soft texture texture for for rice, no for rice, no for rice, no for rice, no for rice, no rice, very off flavours, off flavours, off flavours, off flavours, off flavours, liquid, good brown- brown- brown- brown- brown- balance of yellow yellow yellow yellow yellow seasonings, colour. colour, colour, colour. colour, salty, brown strong taste strong taste Strong taste Less intense yellow of of of taste of colour. No mushrooms. mushrooms. mushrooms. mushrooms off taste. than week

12.

20°C [Not tested] Soft texture Soft texture Soft texture Firmer Texture for for rice, no for rice, no for rice, no texture for rice more off flavours, off flavours, off flavours, rice, no off granular, brown- brown- brown- flavours, slight paper yellow yellow yellow brown- taste, brown- colour. colour, no colour, slight yellow yellow

off-taste. paper taste. colour, colour, pepper taste. pepper taste.

42°C [Not tested] Soft texture Soft texture [Not tested] Soft texture Soft texture for rice no for rice no for rice no for rice no off flavours, off flavours, off flavours, off flavours, brown- brown- brown- brown- yellow yellow yellow yellow colour, colour, acid colour, acid colour, slight strong taste taste but no taste but no metallic but of off taste. off taste. no off taste. mushroom.

Meal 2: Potato gratin.

Storage 0 weeks 6 weeks 10 weeks 11 weeks 12 weeks 13 weeks temperature

4°C Firm texture Firm texture Firm texture Firm texture Firm texture Firm texture of potato, of potato, of potato, of potato, of potato, of potato, liquid, good liquid, good liquid, good liquid, good liquid but liquid but balance of balance of balance of balance of granular, granular, seasonings, seasonings, seasonings, seasonings, good balance good balance homogeneo- homogeneo- homogeneo- homogeneo- of of us sauce, us sauce, us sauce, us sauce, seasonings, seasonings, beige colour. beige colour. beige colour. beige colour. beige colour. beige colour

No off taste. a minority of a minority of a minority of Slightly metallic tasters found tasters found tasters found metallic taste, a acid taste of acid taste of acid taste of taste. minority of the sauce. the sauce. the sauce. tasters found rancid.

20°C [Not tested] Less firm Firm texture Firm texture Firm texture Firm texture texture of of potato, of potato, of potato, of potato, potato than liquid, good liquid, good liquid, good liquid, week 0 at balance of balance of balance of metallic

4°C, liquid, seasonings, seasonings, seasonings, taste, off good balance homogeneohomogeneohomogeneotaste. of us sauce, us sauce, us sauce,

seasonings, darker darker darker

homogeneocolour. No colour. Slight colour, slight

us sauce, off taste. metallic metallic

more dark taste. taste, slight

colour. No acid pepper

off taste. taste.

42°C [Not tested] Less firm [Not tested] [Not tested] [Not tested] [Not tested] texture of

potato than

week 0 at

4°C, liquid,

good balance

of

seasonings,

non- homogeneous sauce,

more dark

colour,

strong rancid

off taste.

Meal 3: Thinly-sliced chicken and vegetables.

Storage 0 weeks 6 weeks 10 weeks 11 weeks 12 weeks 13 weeks temperature

4°C Very firm Very firm Very firm Very firm Very firm Very firm texture of texture of texture of texture of texture of texture of rice, liquid, rice, dry rice, rice, dry rice, rice, dry rice, rice, dry rice, rice, dry good balance meat tender meat tender meat tender meat tender meat, white of No off taste, No off taste, No off taste, No off taste, wine taste, seasonings, no change of no change of no change of strong olive pungent. No meat tender. colour. colour. colour but taste. off taste.

No off taste. strong taste

of olive.

20°C [Not tested] Very firm Very firm Very firm Very firm Very firm texture of texture of texture of texture of texture of rice, dry rice, rice, dry rice, rice, dry rice, rice, dry rice, rice, dry meat tender meat dry meat dry meat very meat, white

No off taste, texture. No texture. No dry texture. wine taste, no change of off taste, no off taste, no No off taste, pungent, colour. change of change of no change of slight off colour. colour. colour. taste.

42°C [Not tested] Very firm Very firm Very firm Off taste. [Not tested] texture of texture of texture of

rice, less dry rice, less dry rice, dry rice,

rice, meat rice, meat meat dry

tender. No dry. No off texture. Clear

off taste, no taste, no off taste, acid

change of change of taste, no

colour. colour. change of

colour.

Meal 4: Hungarian goulash.

Storage 0 weeks 6 weeks 10 weeks 11 weeks 12 weeks 13 weeks temperature

4°C Firm texture Firm texture Firm texture Firm texture Firm texture Firm texture of potato, of potato, of potato, of potato, of potato, of potato, liquid, strong liquid, meat liquid, meat liquid, meat liquid, meat liquid, meat taste of tender. No tender. No tender. No tender. No tender. No pepper, meat off taste. off taste. off taste. off taste. off taste. tender. No Pungent. A Pungent. Pungent. Pungent. off taste. minority of

tasters found

potato with

off notes.

20°C [Not tested] Firm texture Firm texture Firm texture Firm texture Firm texture of potato, of potato, of potato, of potato, of potato, liquid, strong liquid, strong liquid, strong liquid, strong liquid, meat taste of taste of taste of taste of tender. No pepper, meat pepper, meat pepper, meat pepper, meat off taste. tender. No tender. No tender. No tender. No Pungent. off taste. off taste. off taste. off taste.

42°C [Not tested] Firm texture Firm texture Firm texture [Not tested] of potato, of potato, of potato,

liquid, strong liquid, strong liquid, strong

taste of taste of taste of

pepper, meat pepper, meat pepper, meat

tender, acid tender, acid tender, acid

flavour but flavour and flavour and

not strong in metallic metallic

taste. No off taste, taste, clear

taste. beginning of off taste.

off taste. Example 2

An analysis was carried out to compare the vitamin content of a meal of thinly-sliced chicken and vegetables prepared using (i) prior art pre-cooking techniques or (ii) the "cook in pack" method of the invention.

The meal prepared according to the method of the invention had significantly higher vitamin content than the meal prepared using prior art pre-cooking techniques, indicating that the method of the invention preserves vitamins during the cooking process.

Thinly-sliced chicken and vegetables Pre-cooked Cook in pack

Vitamin E (IU/lOOg) < 0.5 1.4

Vitamin A as Retinol ^g RE/lOOg) 6.8 8.9

Vitamin C as ascorbic acid (mg/lOOg) 1.5 2.1

Vitamin Kl ^g /100g) 8.9 13.4

Claims

1. A method for manufacturing a packaged food product, said method comprising the steps of:

(a) providing raw food ingredients combined in a pouch, wherein said pouch is liquid- impermeable and gas-impermeable;

(b) sealing the pouch; and

(c) subjecting the sealed pouch to a high-pressure heat treatment comprising a temperature of at least 122°C and a pressure of at least 2 bar, for a duration of at least 15 minutes.

2. The method of claim 1, wherein the packaged food product is suitable for storage at room temperature for at least 8 weeks.

3. The method of claim 1 or claim 2, wherein the high-pressure heat treatment comprises a temperature of at least 123°C.

4. The method of any preceding claim, wherein the high-pressure heat treatment comprises a pressure of at least 2.5 bar.

5. The method of any preceding claim, wherein the high-pressure heat treatment has a duration of at least 20 minutes.

6. The method of any preceding claim, wherein the high-pressure heat treatment simultaneously cooks and sterilises the raw food ingredients.

7. The method of any preceding claim, wherein the sealed pouch is subjected to a single high-pressure heat treatment.

8. The method of any preceding claim, wherein the high-pressure heat treatment is a high- pressure steam treatment.

9. The method of any preceding claim, wherein the raw food ingredients do not comprise any preservatives apart from salt and/or sugar.

10. The method of any preceding claim, wherein the raw food ingredients have not been subjected to any acidification treatment.

11. The method of any preceding claim, wherein the pH of the combined raw food ingredients is 4 or greater.

12. The method of any preceding claim, wherein the raw food ingredients comprise oats and milk.

13. The method of any preceding claim, wherein the raw food ingredients comprise probiotic micro-organisms.

14. The method of any preceding claim, wherein the packaged food product is suitable for storage at room temperature for at least 12 weeks.

15. A packaged food product obtainable by the method of any one of claims 1-14.