WO2007054726A1 - Thermal stabilization of packaged foodstuffs - Google Patents

Thermal stabilization of packaged foodstuffs Download PDF

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Publication number
WO2007054726A1
WO2007054726A1 PCT/GB2006/004225 GB2006004225W WO2007054726A1 WO 2007054726 A1 WO2007054726 A1 WO 2007054726A1 GB 2006004225 W GB2006004225 W GB 2006004225W WO 2007054726 A1 WO2007054726 A1 WO 2007054726A1
Authority
WO
WIPO (PCT)
Prior art keywords
foodstuff
flexible package
shaking
package
process according
Prior art date
Application number
PCT/GB2006/004225
Other languages
French (fr)
Inventor
Nick Hazell
Steve Tearle
Marcel Velthuis
Edwin Brouwer
Josefine Treijtel
Original Assignee
Mars, Incorporated
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mars, Incorporated filed Critical Mars, Incorporated
Publication of WO2007054726A1 publication Critical patent/WO2007054726A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B4/00—General methods for preserving meat, sausages, fish or fish products
    • A23B4/005—Preserving by heating
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23C—DAIRY PRODUCTS, e.g. MILK, BUTTER OR CHEESE; MILK OR CHEESE SUBSTITUTES; MAKING THEREOF
    • A23C3/00—Preservation of milk or milk preparations
    • A23C3/02—Preservation of milk or milk preparations by heating
    • A23C3/023—Preservation of milk or milk preparations by heating in packages
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
    • A23L3/10—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by heating materials in packages which are not progressively transported through the apparatus
    • A23L3/14—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by heating materials in packages which are not progressively transported through the apparatus with packages moving on the spot
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
    • A61L2/02—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using physical phenomena
    • A61L2/04—Heat

Definitions

  • the present invention relates to processes for the thermal treatment of food products stored in flexible packages, and to the packaged food products obtainable thereby.
  • the flexible packages are filled in special filling and sealing equipment.
  • the sealed flexible packages are then subjected to a thermal treatment to stabilise the contents.
  • Flexible packages such as pouches are especially used for packaging of pourable materials, in particular liquids such as sauces, and semi-solid compositions such as petfood.
  • the thermal stabilisation may be by pasteurisation or by sterilisation.
  • Pasteurisation consists of heating the food product to a temperature generally between 60 0 C and 9O 0 C for a predetermined time to inactivate vegetative microorganisms in the food product.
  • Pasteurisation allows long-term storage at ambient temperature except in the presence of strains highly resistant to acidity.
  • the minimum lethality factor F 0 (equivalent to number of minutes of treatment at 121.1 0 C) needed to achieve 12D reduction is 2.4 minutes.
  • a higher lethality factor generally of at least 3 is applied in order to provide a safety margin and optionally to inactivate other, more resistant spores, such as B. Stearotherniophilus.
  • veterinary regulations require an Fo value in the range 20 to 40.
  • a drawback of autoclave sterilisation arises from the appearance of a temperature gradient between the periphery and the core of the food product being sterilised inside the package. It is necessary to heat the package for a sufficiently long time for the defined lethality factor F 0 to be reached throughout the product. This results in excessive heat treatment of the periphery of the product, with adverse effects on organoleptic quality. Moreover, the overall time required for the sterilisation is thereby increased. These problems are exacerbated for large packages. It is conventional to rotate the packages inside the autoclave to assist heat transfer within the packages, but the improvement in processing time achieved by conventional rotating autoclaves is slight.
  • WO96/11592 describes an improved process for autoclave sterilisation of canned food products.
  • the cans are sterilised in a retort whilst being reciprocated along their axis with a vigorous linear motion.
  • the food products are packaged in the cans with a headspace.
  • the combination of the headspace and the vigorous shaking of the cans results in a reduction of more than 90% in the heating time of the cans in the retort, with consequent reduction in overall process time and improvement in organoleptic properties of the product.
  • the use of sufficiently vigorous shaking results in a process that is reliable and reproducible. However, it is essential to have a headspace in the cans.
  • the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the heated environment and the shaking conditions are selected to achieve F 0 greater than about 3.0 in a treatment time less than about 20 minutes.
  • the conditions are selected to achieve F 0 greater than about 4.0, still more suitably greater than about 5.0, and still more suitably greater than about 10.
  • the treatment time required to achieve said Fo is less than about 15 minutes, more preferably less than about 10 minutes.
  • treatment time refers to the total time from the start of heat-up of the products.
  • the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the heated environment and the shaking conditions are selected to reduce the time required for the foodstuff to reach a temperature of at least about 110°C (the heat-up time) to less than about 10 minutes.
  • the said time required for the foodstuff to reach a temperature of at least about 110°C is less than about 5 minutes.
  • the heated environment and the shaking conditions are selected to reduce the time required for the foodstuff to reach a temperature of at least about 120°C to less than about 10 minutes, preferably to less than about 5 minutes.
  • heat-up time refers to the time from the start of heat-up of the products.
  • the heat-up time and the treatment time will depend on the size of the package. Large packages, for example packages having capacity greater than about 1 liter, may require longer heat-up times and treatment times than those specified above.
  • the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the the shaking conditions are selected to achieve a peak acceleration of the flexible package of at least about 0.5g.
  • the said peak acceleration is greater than about 1.Og, preferably greater than about 1.5g, more preferably greater than about 2.Og. It has been found that there is a threshold peak acceleration above which the time required for the foodstuff to reach a predetermined temperature is substantially insensitive to further increase in the shaking acceleration. This threshold generally lies between 2g and 3g. Accordingly, the peak acceleration is preferably in the range from about 2.Og to about 3.0g.
  • the term "shaking" refers to any regular or irregular reciprocating movement, and therefore does not encompass simple rotation of the flexible packages as in a rotating retort. The shaking is suitably by substantially linear reciprocation, preferably substantially simple harmonic motion.
  • the maximum displacement (peak to peak) of the shaking is suitably from about 5cm to about 50cm, for example from about 10cm to about 30cm.
  • the frequency of the shaking is suitably from about lOOrpm to about 250 rpm, for example from about 120rpm to about 200rpm.
  • the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the flexible package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the shaking conditions are selected to reduce the time required for the foodstuff to reach a predetermined temperature by at least about 50% relative to the time required for a stationary package.
  • a stationary package refers to a flexible package of identical type containing the same amount of the same foodstuff with substantially zero headspace.
  • the flexible package is preferably a pouch.
  • the term "pouch” herein refers to a closed container formed substantially or completely of a flexible sheet material.
  • the sheet material normally comprises at least one continuous layer of thermoplastic film, or it may be a laminated sheet made up of more than one thermoplastic film layer. At least a portion of the sheet material may be transparent to allow inspection of the pouch contents.
  • the sheet material is substantially impermeable to liquids, and it is normally also substantially impermeable to gases such as oxygen.
  • the sheet material making up the pouch may further comprise a metal layer, such as an aluminium layer, to render the material air-and light-impermeable and to provide aesthetic effects.
  • the package preferably consists essentially of the flexible sheet, material.
  • the package may, for example, be a so-called pillow pouch, typically formed by continuous form-fill- seal equipment, or it may be formed by bonding together front and back faces of flexible sheet materials around their marginal edges.
  • the pouch may be a stand-up pouch. That is to say, a pouch formed by bonding together front and back faces of sheet material around three edges, with a gusset sheet inserted and bonded to the respective fourth edges of the front and back sheets to form a base for the pouch.
  • the total thickness of each flexible wall of the pouch is suitably in the range of from 50 micrometers to 1000 micrometers, for example 100 micrometers to 500 micrometers.
  • the package may be provided with a nip and/or a line of weakness and/or a tear strip to allow the container to be opened after filling.
  • the flexible package contains from about 100ml to about 10000ml of said foodstuff, preferably from about 150 ml to about 1000ml of said foodstuff.
  • the foodstuff may be any foodstuff that can be packaged with substantially zero headspace, for example a liquid, paste or gel foodstuff. Suitable foodstuffs include sauces, spreads, beverages and pet foods.
  • the foodstuff is packaged with substantially zero headspace.
  • headspace refers to a volume of air or other gases entrapped inside the package after sealing of the pouch.
  • the headspace height is less than about 3cm, preferably less than about 2cm, for example less than about lcm.
  • the headspace volume at atmospheric pressure is less than about 30ml, preferably less than about 20ml, more preferably less than about 10 ml and most preferably less than about ImI.
  • the headspace volume at atmospheric pressure is less than about 5% of the internal volume of the pouch, preferably less than about 2% thereof, and more preferably less than about 1% thereof.
  • the package is preferably gripped along at least two opposed edges during the shaking.
  • the shaking direction is substantially parallel to an edge of the package, and preferably it is substantially parallel to the longest edge of the package in order to maximize agitation of the foodstuff.
  • the edge through which the package was filled may be clamped during shaking.
  • the shaking direction preferably lies substantially in the plane of the edge seams of the pouch and/or the plane of the edge through which the package was filled.
  • the package is a pouch that is substantially rectangular, with two longer and two shorter edges, at least the two longer edges of the pouch are clamped during the step of shaking, and the shaking comprises a linear reciprocating motion in a direction substantially perpendicular to the longer edges and substantially in the plane containing the longer edges.
  • the steps of heating and shaking are carried out inside an autoclave.
  • the autoclave is heated by steam, for example steam at from about 40 to about 50 psig.
  • the temperature of the heated environment is from about 110°C to about 150°C, preferably from about 120°C to about 130°C, for example about 125°C.
  • the invention according to the third and fourth aspects above may alternatively be used for pasteurisation, in which case the temperature of the heated environment is from about 60°C to about 95°C, suitably from about 80 0 C to about 90°C.
  • the shaking is sufficiently vigorous that the time required for the foodstuff to reach a predetermined temperature is substantially insensitive to further increase in the shaking acceleration. It has been found that the process efficiency substantially reaches a plateau as the shaking peak acceleration increases. Further increases in shaking acceleration do not significantly increase the heat-up speed or efficiency. Once the shaking acceleration is in this regime the process has high reproducibility.
  • the shaking is maintained substantially throughout the whole of the heat-up and sterilization phase of the cycle, and optionally also throughout the cooling phase of the stabilization cycle.
  • the process of the present invention further comprises a step of cooling said pouch after said heating step, while simultaneously shaking the pouch to agitate the foodstuff inside the pouch.
  • the cooling may be by means of a water spray. The shaking greatly increases the speed of cooling of the pouch contents, thereby reducing the overall cycle time.
  • the present invention provides a pouch filled with a stabilized foodstuff and having substantially zero internal headspace, obtainable by a process according to any preceding aspect of the invention.
  • the foodstuff is commercially sterile.
  • the foodstuff is substantially free of the "cooked" flavor and color characteristics of conventionally heat-sterilized foods.
  • any feature that is disclosed in connection with any one aspect of the present invention may also be present in a process or product according to any other aspect or embodiment of the invention.
  • the process according to the present invention may achieve F 0 greater then about 3.0 in a treatment time less than about 15 minutes, and also reduce the time required for the foodstuff to reach a temperature of at least about 110°C to less than about 10 minutes.
  • the process may achieve F 0 greater then about 3.0 in a treatment time less than about 15 minutes, and also the shaking conditions may be selected to achieve a peak acceleration of the flexible package of at least about 0.5g.
  • Fig. 1 shows a top view of a moveable shelf for an autoclave showing the position of three pouches clamped thereto, and also showing thermocouples inserted into two of the pouches for test measurements;
  • Fig. 2 shows graphs of temperature against time and cumulative F 0 against time as measured for a sterilisation process with shaking for flexible packages containing headspace (Fig. 2A, reference example) and for flexible packages containing no headspace (Fig.2B);
  • Fig. 3 shows a graph similar to those of Fig. 2 for a comparative process with static flexible packages containing a headspace
  • Fig. 4 shows a graph similar to those of Fig. 2 for a pouch in a conventional rotating retort.
  • FIG. 1 three conventional stand-up sauce pouches 1 are shown in position on a specially adapted autoclave shelf 2.
  • the pouches 1 have nominal capacity 400ml, and dimensions 140mm x 185mm.
  • Each pouch 1 was filled with 340 grams of a white pasta sauce and secured to the shelf by adhesive tape (not shown) along the edges of the pouches.
  • the orientation of the pouches 1 was with their long edges 3 substantially perpendicular to the shaking direction in the retort.
  • the shelf 2 is loaded into the retort substantially coplanar with the shaking direction.
  • Thermocouple probes 4 were inserted into two of the pouches 1 to measure the temperature of the contents.
  • a plurality of the shelves may be stacked in a suitable, moveabie frame inside the autoclave.
  • the shelf was then shaken by a mechanism substantially as described in WO96/11592.
  • the frame holding the shelves is mounted on rails inside the autoclave to permit linear motion, and coupled to a horizontal drive rod that extends through the wall of the autoclave through a pressure-tight seal.
  • the distal end of the drive rod is coupled through a crank to a drive motor that drives the rod in a reciprocating motion.
  • Example 1 and Reference Example 1 Stand-up pouches containing 340 grains of white pasta sauce were packaged with 25 ml headspace (Reference Example 1) and with zero headspace (Example 1). The pouches were treated in an autoclave heated with steam in conventional fashion to a nominal sterilisation temperature of 125°C. The pouches inside the autoclave were subjected to a substantially linear reciprocation approximating simple harmonic motion. The shaking amplitude was 150mm, and frequency was ISOrpm. This gives a calculated peak acceleration of approximately 2.3 g.
  • the measured time-temperature profiles of the thermocouples immersed in the sauces are shown in Figs. 2A and 2B as solid lines.
  • the measured time-temperature profile for the autoclave chamber is shown as the dot-dash line in Figs. 2 A and 2B.
  • the figures also shows graphs of cumulative F 0 for the samples as dashed lines. It can be seen that the autoclave chamber reaches the sterilisation temperature of 125°C within about two minutes. The temperature of the sauces rises rapidly and smoothly, reaching 120°C about three minutes later. Cumulative Fo exceeds 4.0 within about seven minutes at the start of the cycle.
  • Example 1 The procedure of Example 1 was repeated on pouches that were identical to those of Example 1.
  • the autoclaving was carried out in the same autoclave as Example 1, with the pouches held static, i.e. no movement of the pouches.
  • Fig. 3 shows time-temperature profiles for Reference Example 1, in similar fashion to the graphs of Fig. 2. It can be seen that the pouch contents take about 27 minutes to reach 120°C, and nearly 30 minutes for F 0 to exceed 4.0.
  • the shaking motion inside the autoclave reduces the heat-up time of the pouches by about 75% relative to the static flexible packages, whether or not there is a headspace.
  • the 75% reduction is somewhat less than the 90+% reduction in heat-up time reported for cans in WO96/11592.
  • the difference between the performance of pouches and the performance of metal cans is accounted for by the lower thermal conductivity of the pouch walls as compared to can walls.
  • Fig. 4 shows time-temperature graphs for the pouches as described in Example 1 being sterilised in a conventional rotating retort of the kind currently in commercial use. It can be seen that the total cycle time is almost one hour, and the heat-up time of the pouch is more than 20 minutes.
  • the commercial rotating retort is therefore seen to be comparable in performace to the static test retort of the preceding example. It can thus be seen that the shaking processes according to the present invention achieve very much faster heating of the pouch contents than conventional rotating retort processes, which have much lower peak accelerations.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Polymers & Plastics (AREA)
  • Health & Medical Sciences (AREA)
  • Food Science & Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Nutrition Science (AREA)
  • Animal Behavior & Ethology (AREA)
  • Veterinary Medicine (AREA)
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  • General Health & Medical Sciences (AREA)
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  • Food Preservation Except Freezing, Refrigeration, And Drying (AREA)

Abstract

A process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously vigorously shaking the package to agitate the foodstuff inside the package, wherein the heated environment and the shaking conditions are selected to achieve rapid, reproducible heat-up of the foodstuff. Preferably the flexible package is a pouch.

Description

THERMAL STABILIZATION OF PACKAGED FOODSTUFFS
The present invention relates to processes for the thermal treatment of food products stored in flexible packages, and to the packaged food products obtainable thereby.
Flexible packages, especially pouches, are commonly used today for the packaging of food and drink products. Advantages of using such packaging include decreased material and processing costs and ease of shipping.
In conventional food manufacturing, the flexible packages are filled in special filling and sealing equipment. The sealed flexible packages are then subjected to a thermal treatment to stabilise the contents. Flexible packages such as pouches are especially used for packaging of pourable materials, in particular liquids such as sauces, and semi-solid compositions such as petfood. The thermal stabilisation may be by pasteurisation or by sterilisation.
Pasteurisation consists of heating the food product to a temperature generally between 600C and 9O0C for a predetermined time to inactivate vegetative microorganisms in the food product. For acidic food products having a pH less than about 4.5, pasteurisation allows long-term storage at ambient temperature except in the presence of strains highly resistant to acidity.
In order to achieve long-term shelf stability of non-acid food products at ambient temperature, it is usually necessary to resort to sterilizing. This requires heat treatment at temperatures above 1000C, usually in an autoclave under pressure to prevent bursting of the flexible packages. In practice it is not possible to obtain complete sterilisation, the aim being to achieve so-called "commercial sterility". Commercial sterility is defined as freedom from viable forms of micro-organisms having public health significance, as well as any micro-organisms of non-health significance capable of reproducing in the food under the normal non-refrigerated conditions of storage and distribution. For a majority of food products, commercial sterilisation aims to obtain a reduction of 12D (i.e. 12 orders of magnitude) of the population of the microorganism Clostridium botulinum. The minimum lethality factor F0 (equivalent to number of minutes of treatment at 121.10C) needed to achieve 12D reduction is 2.4 minutes. In practice, a higher lethality factor, generally of at least 3 is applied in order to provide a safety margin and optionally to inactivate other, more resistant spores, such as B. Stearotherniophilus. In the case of animal food packaged in flexible packages, veterinary regulations require an Fo value in the range 20 to 40.
A drawback of autoclave sterilisation arises from the appearance of a temperature gradient between the periphery and the core of the food product being sterilised inside the package. It is necessary to heat the package for a sufficiently long time for the defined lethality factor F0 to be reached throughout the product. This results in excessive heat treatment of the periphery of the product, with adverse effects on organoleptic quality. Moreover, the overall time required for the sterilisation is thereby increased. These problems are exacerbated for large packages. It is conventional to rotate the packages inside the autoclave to assist heat transfer within the packages, but the improvement in processing time achieved by conventional rotating autoclaves is slight.
WO96/11592 describes an improved process for autoclave sterilisation of canned food products. The cans are sterilised in a retort whilst being reciprocated along their axis with a vigorous linear motion. The food products are packaged in the cans with a headspace. The combination of the headspace and the vigorous shaking of the cans results in a reduction of more than 90% in the heating time of the cans in the retort, with consequent reduction in overall process time and improvement in organoleptic properties of the product. According to WO96/11592, the use of sufficiently vigorous shaking results in a process that is reliable and reproducible. However, it is essential to have a headspace in the cans.
It has now been found that the process of WO96/11592 can be extended to food products packaged in flexible packages. It has further been found that the process is equally applicable to flexible packages containing a food packaged with substantially zero headspace. The elimination of headspace reduces the oxygen content of the pack and thereby improves shelf life.
Accordingly, in a first aspect the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the heated environment and the shaking conditions are selected to achieve F0 greater than about 3.0 in a treatment time less than about 20 minutes.
Suitably, the conditions are selected to achieve F0 greater than about 4.0, still more suitably greater than about 5.0, and still more suitably greater than about 10. Suitably, the treatment time required to achieve said Fo is less than about 15 minutes, more preferably less than about 10 minutes. The term "treatment time" refers to the total time from the start of heat-up of the products.
In a second aspect, the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the heated environment and the shaking conditions are selected to reduce the time required for the foodstuff to reach a temperature of at least about 110°C (the heat-up time) to less than about 10 minutes.
Suitably, the said time required for the foodstuff to reach a temperature of at least about 110°C is less than about 5 minutes. Suitably, the heated environment and the shaking conditions are selected to reduce the time required for the foodstuff to reach a temperature of at least about 120°C to less than about 10 minutes, preferably to less than about 5 minutes.
The term "heat-up time" refers to the time from the start of heat-up of the products. The heat-up time and the treatment time will depend on the size of the package. Large packages, for example packages having capacity greater than about 1 liter, may require longer heat-up times and treatment times than those specified above.
In a third aspect, the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the the shaking conditions are selected to achieve a peak acceleration of the flexible package of at least about 0.5g.
Suitably, the said peak acceleration is greater than about 1.Og, preferably greater than about 1.5g, more preferably greater than about 2.Og. It has been found that there is a threshold peak acceleration above which the time required for the foodstuff to reach a predetermined temperature is substantially insensitive to further increase in the shaking acceleration. This threshold generally lies between 2g and 3g. Accordingly, the peak acceleration is preferably in the range from about 2.Og to about 3.0g. The term "shaking" refers to any regular or irregular reciprocating movement, and therefore does not encompass simple rotation of the flexible packages as in a rotating retort. The shaking is suitably by substantially linear reciprocation, preferably substantially simple harmonic motion. The maximum displacement (peak to peak) of the shaking is suitably from about 5cm to about 50cm, for example from about 10cm to about 30cm. The frequency of the shaking is suitably from about lOOrpm to about 250 rpm, for example from about 120rpm to about 200rpm.
In a fourth aspect, the present invention provides a process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the flexible package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the shaking conditions are selected to reduce the time required for the foodstuff to reach a predetermined temperature by at least about 50% relative to the time required for a stationary package. The term "a stationary package" refers to a flexible package of identical type containing the same amount of the same foodstuff with substantially zero headspace.
Suitably, the time required for the foodstuff to reach a predetermined temperature is reduced by from about 65% to about 85% relative to the time required for a stationary package, for example by about 70% to about 80%. The flexible package is preferably a pouch. The term "pouch" herein refers to a closed container formed substantially or completely of a flexible sheet material. The sheet material normally comprises at least one continuous layer of thermoplastic film, or it may be a laminated sheet made up of more than one thermoplastic film layer. At least a portion of the sheet material may be transparent to allow inspection of the pouch contents. The sheet material is substantially impermeable to liquids, and it is normally also substantially impermeable to gases such as oxygen. The sheet material making up the pouch may further comprise a metal layer, such as an aluminium layer, to render the material air-and light-impermeable and to provide aesthetic effects.
The package preferably consists essentially of the flexible sheet, material. The package may, for example, be a so-called pillow pouch, typically formed by continuous form-fill- seal equipment, or it may be formed by bonding together front and back faces of flexible sheet materials around their marginal edges. In certain embodiments, the pouch may be a stand-up pouch. That is to say, a pouch formed by bonding together front and back faces of sheet material around three edges, with a gusset sheet inserted and bonded to the respective fourth edges of the front and back sheets to form a base for the pouch. The total thickness of each flexible wall of the pouch is suitably in the range of from 50 micrometers to 1000 micrometers, for example 100 micrometers to 500 micrometers.
The package may be provided with a nip and/or a line of weakness and/or a tear strip to allow the container to be opened after filling. Suitably, the flexible package contains from about 100ml to about 10000ml of said foodstuff, preferably from about 150 ml to about 1000ml of said foodstuff.
The foodstuff may be any foodstuff that can be packaged with substantially zero headspace, for example a liquid, paste or gel foodstuff. Suitable foodstuffs include sauces, spreads, beverages and pet foods.
The foodstuff is packaged with substantially zero headspace. The term "headspace" refers to a volume of air or other gases entrapped inside the package after sealing of the pouch. Suitably, the headspace height is less than about 3cm, preferably less than about 2cm, for example less than about lcm.. Suitably, the headspace volume at atmospheric pressure is less than about 30ml, preferably less than about 20ml, more preferably less than about 10 ml and most preferably less than about ImI. Suitably, the headspace volume at atmospheric pressure is less than about 5% of the internal volume of the pouch, preferably less than about 2% thereof, and more preferably less than about 1% thereof.
The package is preferably gripped along at least two opposed edges during the shaking. Preferably, the shaking direction is substantially parallel to an edge of the package, and preferably it is substantially parallel to the longest edge of the package in order to maximize agitation of the foodstuff. In these and other embodiments, the edge through which the package was filled may be clamped during shaking. The shaking direction preferably lies substantially in the plane of the edge seams of the pouch and/or the plane of the edge through which the package was filled.
Suitably, the package is a pouch that is substantially rectangular, with two longer and two shorter edges, at least the two longer edges of the pouch are clamped during the step of shaking, and the shaking comprises a linear reciprocating motion in a direction substantially perpendicular to the longer edges and substantially in the plane containing the longer edges.
Suitably, the steps of heating and shaking are carried out inside an autoclave. Suitably, the autoclave is heated by steam, for example steam at from about 40 to about 50 psig. Accordingly, the temperature of the heated environment is from about 110°C to about 150°C, preferably from about 120°C to about 130°C, for example about 125°C. I will be appreciated that the invention according to the third and fourth aspects above may alternatively be used for pasteurisation, in which case the temperature of the heated environment is from about 60°C to about 95°C, suitably from about 800C to about 90°C.
Preferably, the shaking is sufficiently vigorous that the time required for the foodstuff to reach a predetermined temperature is substantially insensitive to further increase in the shaking acceleration. It has been found that the process efficiency substantially reaches a plateau as the shaking peak acceleration increases. Further increases in shaking acceleration do not significantly increase the heat-up speed or efficiency. Once the shaking acceleration is in this regime the process has high reproducibility. Suitably, the shaking is maintained substantially throughout the whole of the heat-up and sterilization phase of the cycle, and optionally also throughout the cooling phase of the stabilization cycle.
Suitably, the process of the present invention further comprises a step of cooling said pouch after said heating step, while simultaneously shaking the pouch to agitate the foodstuff inside the pouch. For example, the cooling may be by means of a water spray. The shaking greatly increases the speed of cooling of the pouch contents, thereby reducing the overall cycle time.
Li a further aspect, the present invention provides a pouch filled with a stabilized foodstuff and having substantially zero internal headspace, obtainable by a process according to any preceding aspect of the invention. Preferably, the foodstuff is commercially sterile. The foodstuff is substantially free of the "cooked" flavor and color characteristics of conventionally heat-sterilized foods.
It will be appreciated that any feature that is disclosed in connection with any one aspect of the present invention may also be present in a process or product according to any other aspect or embodiment of the invention. Thus, for example, the process according to the present invention may achieve F0 greater then about 3.0 in a treatment time less than about 15 minutes, and also reduce the time required for the foodstuff to reach a temperature of at least about 110°C to less than about 10 minutes. Alternatively or additionally the process may achieve F0 greater then about 3.0 in a treatment time less than about 15 minutes, and also the shaking conditions may be selected to achieve a peak acceleration of the flexible package of at least about 0.5g. All other combinations of features from the above description of the invention and the accompanying claims are included within the scope of the present disclosure.
Specific embodiments of the present invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a top view of a moveable shelf for an autoclave showing the position of three pouches clamped thereto, and also showing thermocouples inserted into two of the pouches for test measurements;
Fig. 2 shows graphs of temperature against time and cumulative F0 against time as measured for a sterilisation process with shaking for flexible packages containing headspace (Fig. 2A, reference example) and for flexible packages containing no headspace (Fig.2B);
Fig. 3 shows a graph similar to those of Fig. 2 for a comparative process with static flexible packages containing a headspace; and
Fig. 4 shows a graph similar to those of Fig. 2 for a pouch in a conventional rotating retort.
Referring to Figure 1, three conventional stand-up sauce pouches 1 are shown in position on a specially adapted autoclave shelf 2. The pouches 1 have nominal capacity 400ml, and dimensions 140mm x 185mm. Each pouch 1 was filled with 340 grams of a white pasta sauce and secured to the shelf by adhesive tape (not shown) along the edges of the pouches. The orientation of the pouches 1 was with their long edges 3 substantially perpendicular to the shaking direction in the retort. The shelf 2 is loaded into the retort substantially coplanar with the shaking direction. Thermocouple probes 4 were inserted into two of the pouches 1 to measure the temperature of the contents. A plurality of the shelves may be stacked in a suitable, moveabie frame inside the autoclave.
The shelf was then shaken by a mechanism substantially as described in WO96/11592. Briefly, the frame holding the shelves is mounted on rails inside the autoclave to permit linear motion, and coupled to a horizontal drive rod that extends through the wall of the autoclave through a pressure-tight seal. The distal end of the drive rod is coupled through a crank to a drive motor that drives the rod in a reciprocating motion.
Example 1 and Reference Example 1 Stand-up pouches containing 340 grains of white pasta sauce were packaged with 25 ml headspace (Reference Example 1) and with zero headspace (Example 1). The pouches were treated in an autoclave heated with steam in conventional fashion to a nominal sterilisation temperature of 125°C. The pouches inside the autoclave were subjected to a substantially linear reciprocation approximating simple harmonic motion. The shaking amplitude was 150mm, and frequency was ISOrpm. This gives a calculated peak acceleration of approximately 2.3 g.
The measured time-temperature profiles of the thermocouples immersed in the sauces are shown in Figs. 2A and 2B as solid lines. The measured time-temperature profile for the autoclave chamber is shown as the dot-dash line in Figs. 2 A and 2B. The figures also shows graphs of cumulative F0 for the samples as dashed lines. It can be seen that the autoclave chamber reaches the sterilisation temperature of 125°C within about two minutes. The temperature of the sauces rises rapidly and smoothly, reaching 120°C about three minutes later. Cumulative Fo exceeds 4.0 within about seven minutes at the start of the cycle. These data confirm the rapid heating times for vigorously shaken pouches. No significant difference was observed for the pouches without headspace. This result is surprising, since the presence of a headspace was previously thought to be essential to achieve good mixing of the container contents in agitated autoclave sterilisation. It may be that the flexible nature of the pouches permits effective mixing to take place by peristaltic movements of the pouch without the need for any headspace.
Reference Example 2
The procedure of Example 1 was repeated on pouches that were identical to those of Example 1. The autoclaving was carried out in the same autoclave as Example 1, with the pouches held static, i.e. no movement of the pouches.
Fig. 3 shows time-temperature profiles for Reference Example 1, in similar fashion to the graphs of Fig. 2. It can be seen that the pouch contents take about 27 minutes to reach 120°C, and nearly 30 minutes for F0 to exceed 4.0.
Thus, it can be seen that the shaking motion inside the autoclave reduces the heat-up time of the pouches by about 75% relative to the static flexible packages, whether or not there is a headspace. The 75% reduction is somewhat less than the 90+% reduction in heat-up time reported for cans in WO96/11592. The difference between the performance of pouches and the performance of metal cans is accounted for by the lower thermal conductivity of the pouch walls as compared to can walls.
Finally, Fig. 4 shows time-temperature graphs for the pouches as described in Example 1 being sterilised in a conventional rotating retort of the kind currently in commercial use. It can be seen that the total cycle time is almost one hour, and the heat-up time of the pouch is more than 20 minutes. The commercial rotating retort is therefore seen to be comparable in performace to the static test retort of the preceding example. It can thus be seen that the shaking processes according to the present invention achieve very much faster heating of the pouch contents than conventional rotating retort processes, which have much lower peak accelerations.
The above embodiments have been described by way of example only. Many further embodiments falling within the scope of the accompanying claims will be apparent to the skilled reader.

Claims

1. A process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the heated environment and the shaking conditions are selected to achieve F0 greater than about 3.0 in a treatment time less than about 20 minutes.
2. A process according to claim 1, wherein the said conditions are selected to achieve Fo greater than about 3 in a treatment time less than about 10 minutes.
3 A process according to claim 1 or 2, wherein said Fo is greater than about 4.0.
4. A process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the heated environment and the shaking conditions are selected to reduce the time required for the foodstuff to reach a temperature of at least about 110°C to less than about 10 minutes.
5. A process according to claim 4, wherein the said time required for the foodstuff to reach a temperature of at least about 1100C is less than about 5 minutes.
6. A process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the the shaking conditions are selected to achieve a peak acceleration of the flexible package of at least about 0.5g.
7. A process according to claim 6, wherein the said peak acceleration is greater than about 1.Og, preferably greater than about 1.5g.
8. A process for thermal stabilization of a foodstuff comprising the steps of: packaging the foodstuff in a flexible package with substantially zero headspace, and subjecting the flexible package containing the foodstuff to a heated environment while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package, wherein the shaking conditions are selected to reduce the time required for the foodstuff to reach a predetermined temperature by at least about, 50% relative to the time required for a stationary package.
9. A process according to claim 8, wherein the time required for the foodstuff to reach the predetermined temperature is reduced by from about 55% to about 75% relative to the time required for a stationary package.
10. A process according to any of claims 6 to 9, wherein the temperature of the heated environment is from about 60°C to about 1000C5 preferably from about 80°C to about 95°C.
IL A process according to any of claims 1 to 9, wherein the temperature of the heated environment is from about 110°C to about 1500C, preferably from about 1200C to about 1300C.
12. A process according to any preceding claim, wherein the flexible package contains from about 100ml to about 10000ml of said foodstuff, preferably from about 150 ml to about 1000ml of said foodstuff.
13. A process according to any preceding claim, wherein the flexible package is a pouch.
14. A process according to any preceding claim, wherein the flexible package consists essentially of flexible sheet material.
15. A process according to any preceding claim, wherein the flexible package is a pouch having at least two sealed edges, and the shaking comprises a linear reciprocating motion in a direction substantially in the plane containing the clamped edges.
16. A process according to any preceding claim, wherein the steps of heating and shaking are carried out inside an autoclave.
17. A process according to any preceding claim, wherein the shaking is sufficiently vigorous that the time required for the foodstuff to reach a predetermined temperature is substantially insensitive to further increase in the shaking acceleration.
18. A process according to any preceding claim, further comprising a step of cooling said flexible package after said heating step, while simultaneously shaking the flexible package to agitate the foodstuff inside the flexible package.
PCT/GB2006/004225 2005-11-14 2006-11-13 Thermal stabilization of packaged foodstuffs WO2007054726A1 (en)

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ES2351912A1 (en) * 2010-10-05 2011-02-14 Jose Maria Alonso Marrodan Procedure for the thermal treatment of foodstuffs. (Machine-translation by Google Translate, not legally binding)
WO2017021735A1 (en) * 2015-08-05 2017-02-09 Convenience Foods Limited Pasteurisation

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