Packaged food products

Abstract

A method for the production of a stabilized packaged food product includes the steps of: filling a tray with a predetermined quantity of a food starting material; introducing the tray into a pressure vessel and conveying the tray through the pressure vessel while performing the following steps in sequence inside the pressure vessel: (i) treating the food starting material with high-temperature pressurized steam to sterilize the material, (ii) dosing the sterile food material inside the tray with a predetermined amount of sterile water; and (iii) applying a lid to the tray to seal the food product inside the tray while maintaining the tray in a sterile environment. Also provided are an apparatus for performing the method and packaged stabilized full moisture food products obtainable by the process.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a national stage filing of PCT / IB2008 / 002120 filed May 29, 2008 claiming priority to GB 0710228.8 filed on May 29, 2007; GB 0715579.9 filed on Aug. 9, 2007; and GB 0801052.2 filed on Jan. 21, 2008.TECHNICAL FIELD[0002]The present invention relates to stabilized, packaged, full moisture food products and to methods and apparatus for the preparation thereof. It relates in particular to stabilized, packaged, full-moisture food products containing cereals such as rice, wheat or pasta, and / or other ingredients such as vegetables and meat.BACKGROUND OF THE INVENTION[0003]It is known to provide packaged, full-moisture precooked food products, such as soups, stews, and rice, pasta or wheat (bulgur) products that can be reheated in a short time, for example in a microwave oven. These products are sometimes referred to as “ready-to-heat” or “one-minute” products.[0004]The high moisture content of these ready-to-heat products req...

AI Technical Summary

Benefits of technology

[0018]It is an advantage of the present invention that the food starting material generally does not require soaking or wetting before introduction into the pressure vessel. Indeed, at least a major portion by weight of the starting material is generally not soaked or wetted before introduction into the pressure vessel, since the sterilization step is preferably carried out on a dry product in order to minimize heating time, and to minimize thermal damage to the food components such as starch. This is a simplification over the process described in U.S. Pat. No. 5,860,356.

[0019]The trays containing the food starting material are introduced into a pressure vessel, for example through a suitable pressure lock. Preferably the pressure lock permits continuous feeding of the trays to the pressure vessel. Exemplary pressure locks and tray conveyors are described in EP-A-0691082.

[0020]The pressure vessel may consist of a single pressure chamber, or it may comprise two, three or more pressure chambers separated by pressure locks. The use of multiple pressure chambers to form the pressure vessel enables process parameters to be controlled further by varying the steam pressure and temperature between the chambers. In addition, it allows individual pressure chambers to be isolated for cleaning or maintenance. The pressure vessel (or chamber thereof) is suitably in the form of a tube having a conveyor therein for conveying the trays along the tube. The diameter of the tube is typically about 30 cm to about 100 cm, for example about 50 cm. The total length of the pressure vessel (i.e. the sum of the lengths of the pressure chambers) is typically about 10 m to about 50 m, for example about 15 m to about 40 m. The pressure vessel is thermally insulated to minimise heat loss and steam condensation within the vessel. The pressure vessel is pressurized with steam, optionally mixed with other gases. The steam may be saturated or superheated. The steam temperature is suitably from about 100° C. to about 160° C., preferably from about 125° C. to about 150° C., for example about 135° C. The temperature inside the pressure vessel (or each chamber thereof) is thereby maintained substantially at the steam temperature. Suitably, the gauge pressure in the pressure vessel (or each chamber thereof) is from about 0.05 MPa to about 1.0 MPa, preferably from about 0.1 MPa to about 0.5 MPa, for example about 0.3 MPa to about 0.4 MPa. The temperatures and pressures in each chamber of the pressure vessel may be the same or different within the above ranges.

[0021]The steam is may be injected through suitable nozzles. In certain embodiments, the steam impinges directly onto the top surface of the food bed as the trays move through the tube. In other embodiments, the steam in injected below and / or laterally to the trays. Steam injection may be intermittent or continuous. Improved energy efficiency is achieved by using intermittent injection of (preferably saturated) steam, preferably with forced flow inside the pressure vessel to circulate the steam. The forced flow can be achieved, for example, by providing fans within the vessel. The high temperature of the steam causes the core temperature of the food to rise quickly to a value sufficient to cause rapid sterilization. Uptake of water by the food in this stage of the process is minimal. Typically, with steam at about 135° C., trays containing only rice or wheat are exposed to the steam for a period of from about 20 seconds to about 1 minute, for example about 20 seconds to about 1 minute. Longer steam sterilization, typically about 3 to about 4 minutes, is needed if the trays contain larger pieces, such as vegetable pieces, meat pieces, or large pasta pieces, or if lower steam temperatures are used. The duration of the steam sterilization step is typically regulated by moving the location of the water dosing point in the pressure tube, as described further below. Alternatively or additionally, the duration of the steam sterilization step may be regulated by varying the speed of the conveyor.

[0022]The sterilization time and temperature are suitably selected to provide a reduction of 12D (i.e. 12 orders of magnitude) of the population of the microorganism clostridium botulinum. The minimum lethality factor Fo (equivalent to number of minutes of treatment at 121.1° C.) needed to achieve 12D reduction is 2.4 minutes. In practice, a higher lethality factor, generally of at least about 3, for example about 5, is applied in order to provide a safety margin and optionally to inactivate other, more resistant spores, such as B. Stearothermophilus.

[0023]It is an advantage of the present invention that the sterilization step may be performed on the food while the food is still dry. This avoids many of the problems caused by prior art processes in which the sterilization temperatures are applied to hydrated cereal grains, or to cereal grains in contact with liquid water. In particular, the present invention results in a more free-flowing final product exhibiting less damage to the starch structure, for example exhibiting less de-retrogradation of the starch and less extrusion of soluble starches from the product grains. Furthermore, the time required to heat the food particles to sterilization temperatures is greatly reduced, thereby further reducing the process time and damage to the starch and other ingredients as compared to prior art processes.

Problems solved by technology

Metal foil or metal / polymer laminate trays could also be used, but are not so suitable for subsequent microwave reheating of the food product before consumption.

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