GB2524022A - Thermal treatment of food products - Google Patents

Abstract

The thermal treatment of food products is characterised by sterilising to a required Sterilisation Value and concurrently cooking to a targeted range of Cook Values by steps of heating, cooling and agitation of liquid-based foods or beverages. The foods or beverages are typically low-acid (pH>4.5) and generally transfer heat via conduction. The foods may contain particles, such as vegetable soup, and are packaged in containers. The preferred process for a particular product container combination is determined via the steps of: agitating by essentially horizontal agitation at a rate or rates sufficient to provide homogeneity within individual containers; determining and controlling best case and worst case values of parameters including variability of sterilisation temperature, initial product temperature, fill weight/headspace, product viscosity, liquid/solid ratio, particle size and agitation rate; selecting or determining a degree of cooking for the food or beverage; and selecting the appropriate sterilising temperature.

Description

THERMAL TREATMENT OF FOOD PRODUCTS

TECHNICAL FIELD

This invention relates to thermal treatment for the preservation of food products for storage under ambient conditions for subsequent consumption. It is concerned with a novel batch retort thermal process which provides greatly improved control over the food being processed and hence facilitates both the production and the quality of many long shelf life foods packed in ambient stored containers. It is mainly concerned with liquid-based foods and beverages, including those containing particles, that in conventional static retorts would transfer the heat required for sterilisation largely by conduction, and that have a pH above 4.5. These are known as low-acid conduction products' and include a wide range of preserved foods such as soups, sauces, ready meals', desserts, baby foods, pet foods as well as some food ingredients and catering products. It is also concerned with low acid beverages, such as milk-or protein-based products that would transfer the required heat in conventional retorts by a combination of conduction and convection.

BACKGROUND ART

The sterilisation by heat providing for the indefinite safe preservation of foods in sealed containers has been known for some two hundred years. Retorts that heat cans, jars or other containers under pressure are widely used in the food industry around the world. In more recent times aseptic continuous processes in which liquid foods are passed through heat exchangers and packed under carefully controlled sterile conditions into sterile containers have set new standards for quality and other processes such as microwave heating, ohmic heating and high pressure sterilisation are made use of to sterilise certain types of food products.

The most common type of retort is static'. Static retorts are relatively simple and inexpensive but heat is transferred slowly by conduction into the containers for sterilisation and out of the containers during cooling. With conduction products' static retorts produce cold spots', generafly towards the centre of each container and thus also hot spots' or hot regions, generally towards the surface of the container. Thus the food experiences much more heat at the outer parts of the container than in the centre. As it is essential that the cold spots are thoroughly sterilised, this leads inevitably to over-sterilisation in the hotter regions. It is practice in the food industry to seek out and determine the position of cold spots both within individual containers and within the retort itself, and then process the foods to ensure that the foods in all the cold spots are fully sterilised. They thus produce foods that are unevenly processed, over-processed in part, and with little control over the parts away from the cold spot, these parts become over-sterilised, over-cooked and possibly even scorched in part.

More complex and expensive rotary agitation retorts of various designs were introduced in the last century to induce some degree of mixing of the foods in the container. In operation they reduce the difference in processing between the cold spot and the hotter regions. Such retorts produce foods which are less unevenly processed than foods from static retorts but which are nevertheless uneven'y processed, partly or significantly over-processed and, with Httle control over the parts away from the cold spot, are also partially over-cooked.

European Patent 0804095 describes an improved technology, now commercialised as the Shaka' (RTM) process, in which containers are shaken horizontally inside a retort. This process enables sterilisation to be carried out up to 10 times as fast as rotary retort processes and up to 20 times as fast as static processes.

Static and rotary retorts make up the overwhelming majority (over 95%) of retorts used in this sector of the thermal processing industry.

DEFINITIONS

In considering food processing in terms of the presently proposed concept it is helpful to consider definitions of concepts widely used in the industry and some additional ones.

STERILISATION VALUE (To') The degree of sterilisation for a wide range of products for which pH is above 4.5 (low-acid), is expressed as Sterilisation Value Fo' using the formula: T-12 LIJ Fo=Jl0--c/t Where: 121.1°C is reference temperature, T°C is the sterilisation temperature, t is the sterilisation time (mm), and z is temperature difference required for a 10-fold change in thermal death time.

The usual reference organisms are spores of Clostñdium Botulinum giving z =10°C.

It is essential for safety to determine the temperature and time necessary to produce a sterile product. For low acid products (pH>4.5) this means achieving a set minimum Sterilisation Value (Fo), often to a minimum value of 6. Depending on the exact nature of the product, a Sterilisation Va'ue in the range Fo = 6-20 would generally be necessary to ensure food safety.

COOK VALUE (Co) In commercial practice the degree of cooking can be expressed as a Cook Vakie (Co') which is a summation of the heat treatment the food receives. Cook Value rethtes the quality change during high temperature thermal processing to an equivalent 100°C cooking process, using the lower reference temperature of 100°C, as follows: rr-u,o co=JioLz di Where: T °C is the process temperature, t is the process time (mm), and z values ranging from 25°C to 33°C are generally used to compute Cook Values.

The exact z value selected depends on the particular food and the characteristics of most interest e.g. taste, vitamin retention, colour or texture change etc. tt can be observed that at 100°C the value of the power in the bracket becomes 0.

PASTEUR ISA TION UNIT (PU) For products where the pH is less than 4.5 (high acid), only pasteurisation is necessary. The Pasteurisation Units are determined using the formula below T-Trcf pu=JloL z Where: t = time in minutes, T = Fasteurisation temperature, T ref is reference temperature in degree C usually between 60 & 80°C and z = is temperature difference required for a 10-fold change in therma' death time usually between 5 & 10°C.

The worst case' heating conditions for a container of product are those that cause the contents to heat in the slowest way. Worst case' heating conditions for a particular product, process, container combination will occur in the coMest spot in the slowest heating container of all in the batch or batches of containers being treated when all the relevant variables are set, within their allowed limits, to be at their most adverse. These variaHes can include such things as fill temperature, retort temperature, agitation rate, fill weight, product viscosity, solid/liquid ratio and overpressure. Overpressure in the retort above that generated by the temperature alone is sometimes required to balance the pressure in the container to avoid distortion and other defects mainly when processing flexible and glass containers.

BEST CASE' The best case' heating conditions for a container of product are those conditions that cause the contents to heat in the fastest way. Best case' heating for a particular product, process, container combination will occur in the honest spot in the fastest heating container of all in the batch or batches of containers being treated when all the relevant variables are set, within their allowed limits, to produce the fastest heating. These variables can include such things as fill temperature, retort temperature, agitation rate, fill weight, product viscosity, solid/liquid ratio and overpressure.

DEGREE OF PROCESS 1-TOMOGENETTY (DoPED' The Degree of Process Homogeneity' is the ratio, expressed as a percentage, of the Cook Values from the coldest arid hottest regions of individual containers arid dividing one by the other, the closer to an ideal of 100%, the more homogeneous the process conditions.

SCHEDULED HEAT PROCESS

A scheduled process is determined from heat penetration tests, using all the worst case' conditions in the thermal process necessary to give the required minimum Sterilisation Vakie at suitably selected temperature or temperatures.

DISCLOSURE OF THE INVENTION

According to a first aspect of the present invention there is provided a process for the thermal treatment of liquid based food or beverage products, including those containing particles, characterised by sterilising to a required Sterilisation Value and concurrently cooking within or dose to a targeted range of Cook Values or other measure of quality by steps of heating, cooling and agitation of the foods or beverages in containers and determining the preferred process for a particular product/container combination via the steps of: a. agitating by essentially horizontal agitation at a rate or rates sufficient to provide the required degree of process homogeneity (DoPH' as hereinbefore defined) within individua' containers making up a load for processing and b. determining and controlling best case' and worst case' values, as hereinbefore defined, of parameters including variability of sterilisation temperature, initial product temperature, fill weight/headspace, product viscosity, liquid/solid ratio, particle size and agitation rate, and hence likely variation within the given retort load and between other loads for processing and c. selecting or determining a suitable z value for the food or beverage and d. selecting the appropriate sterilising temperature or temperatures.

According to a first preferred version of the first aspect of the present invention the process provides for the in-container sterilisation for long term storage at ambient temperatures liquid-based foods or beverages, including those containing particles, which without agitation would heat and cool hrgely by conduction, such products generally known as Conduction Products'.

According to a second preferred version of the first aspect of the present invention or of the first preferred version thereof a targeted Cook Value is selected lying in a ramge of Cook Values that a competent cook would consider gave a satisfactory or ideal result when cooking foods or beverages for immediate consumption.

According to a third preferred version of the first aspect of the present invention or any preceding preferred version thereof the process is characterised in that the contained foods or beverages are low-acid', that is they have a pH > 4.5.

According to a second aspect of the present invention there is provided a process according to the first aspect or any preferred version thereof in which heat penetration data is used to determine the scheduled processes at selected temperatures, and also to calculate the minimum Cook Values at these temperatures and maximum Cook Values are calculated by applying the times and temperatures of the scheduled processes to the heat penetration data from the best case' filling and processing conditions, and thus determine and select the preferred range of Cook Values.

According to third aspect of the present invention there is provided a process according to the first or second aspects or of any preferred versions thereof further characterised in that the determination of z value as aforesaid is established by thermafly processing the given contained food using a scheduled or other suitable process to give the required level of sterilisation and then cooking a separate sample of the given food at 100°C, at which temperature the z value drops out of the equation, to the same flavour development or other measure of cooking as that of the sterilised sample, noting the time taken in minutes which will be the reference Cook Value, and then using the reference Cook Value and time and temperature from the scheduled or other suitable process in the Co equation to calculate the appropriate z value for the given food.

According to a fourth aspect of the present invention or any preceding aspect or preferred version thereof the process is further characterised by a method of determining and adjusting the contribution to the range of Cook Values from variations in individual containers using the degree of process homogeneity (DoPH) calculated by determining the Cook Values from the coldest and hottest regions of an individual container and dividing one by the other so that in the event the determined range of Cook Values is more than desired, a higher agitation rate can generally be used to enable a lower DoPH to be generated and thus narrow the Cook Value range.

According to a fifth aspect of the present invention or any preceding aspect or preferred version thereof the process is further characterised by a method of determining the contribution to the range of Cook Values from variations within and between retort loads from both the best case' and worst case' parameters and, by adjustment of these parameters which include variability of sterilisation temperature, initial product temperature, fill weight/headspace, product viscosity, liquid/solid ratio, particle size, agitation rate, optimise, normally minimise as far as reasonaHy possible, the contribution to the range of Cook Vakies to target a preferred cook value range.

According to a sixth aspect of the present invention or of any preceding aspect or preferred version thereof the process is further characterised by determining the contribution to the range of Cook Values from the sterilising temperature or temperatures derived from the relationship shown itt Figure demonstrating that the Cook Value (Co) and Sterilisation Value (Fo) are related and that for the required minimum Fo the Co will vary with temperature and for a given case selecting a different temperature to enable the range of Cook Values to be changed to better target a preferred range.

According to a seventh aspect of the present invention or any preceding aspect or preferred version thereof the process is further characterised itt that for the contained liquid-based foods or beverages other suitable measures of quality are applied including targeting a nutritional value or vitamin content or preferred organ o epti c properties.

According to an eighth aspect of the present invention there is provided a process according to any preceding aspect or a preferred version thereof characterised by increasing and/or decreasing the temperature and/or agitation rates in a step-wise fashion to obtain for the contained liquid-based foods or beverages a targeted range of Cook Vakies or preferred nutritional or organoleptic properties.

According to a ninth aspect of the present invention there is provided a process according to any preceding aspect or a preferred version thereof characterised by processing in a number of stages to obtain for the contained liquid-based foods or beverages a targeted range of Cook Va'ues or preferred nutritional or organoleptic properties.

According to a tenth aspect of the present invention the process according to any preceding aspect or preferred version thereof is further characterised by the DoPH being determined by means of temperature measuring devices inserted in different positions within separate similar containers as an alternative, particulady for smaller containers and those containing significanl particles, to positioning them within the same container.

According to a eleventh aspect of the present invention there is provided a process according to any previous aspect or preferred version thereof is further characterised in that the highest Cook Value within the contents of similar containers in a single load is limited to some 50% above the lowest Cook Value.

According to a twelfth aspect of the present invention there is provided Products produced by a process as claimed in any preceding claims including soups, sauces,, ready meals', baby foods, milk-based and other protein-based beverages, desserts, and pet foods.

According to a thirteenth aspect of the present invention there is provided preserved foods and beverages processed by the method of any preceding aspect of the present invention or a preferred version thereof as catering products and ingredients for subsequent use in the preparation of other food products.

According to an fourteenth aspect of the present invention there is provided a process according to any preceding aspect of the present invention or a preferred version thereof in which the foods or beverages are pasteurised rather than sterilised.

According to a fifteenth aspect of the present invention there is provided preserved foods and beverages pasteurised by the process of any of the preceding first to eleventh aspects or any preferred version thereof and include soups, sauces, dips, ready meals', baby foods, milk-based and other protein-based beverages, desserts, and pet foods.

According to a sixteenth aspect of the present invention there is provided preserved food and beverage ingredients and catering products pasteurised rather than sterilised by the process of any of preceding aspects from first to the eleventh aspects or a preferred version thereof.

FURTHER BACKGROUND ART

To date in-container thermal processes have been able to satisfy the requirement for sterilisation, but generally fail to achieve a Cook Value anywhere near the desired range for a wide variety of food products. However using the invention disclosed above it is now possible to target a range of Cook Values while concurrently achieving the necessary commercial sterility. A targeted range of Cook Values required for a particular food can be defined as that achieved by a competent cook when cooking food for immediate consumption. The process can now be specified to produce product with a set minimum Sterflisation Value, and a Cook Value within or near a targeted range, for example:-Minimum Fo 6, and Co 30 -40.

In the industry a procedure similar to that outlined below is used to determine the time and temperature necessary to achieve the required sterilisation. Firstly the sthwest heating region of the container and ifiso the s'owest heating region of the retort or retorts is identified. Generally in both static and rotary retorting the cold spot in a product that is heated largely by conduction is likely to be near the geometric centre of the container and so thermocouples or other temperature measuring devices are concentrated in this region. The worst case' condition with regard to potential variables in the product, package and process, such as fill temperature, fill weight, product consistency, solid/liquid ratio, free headspace' within a container, retort temperature, agitation rate etc., needs to be found. These parameters are then adjusted and the worst case heating conditions in the product determined. With products containing particles the worst case' heating may well be that at the centre of the largest particle so heat penetration tests need to be carried out with such particles impaled on the thermocouple probes. Once the worst case' with regard to the above parameters has been established these are then used for heat penetration tests to determine the position of the cold spot.

Then the coldest region of the retort also needs to be found using multiple thermocouples placed in different parts of the retort. Finally heat penetration tests using all the worst case' conditions are run to allow the producer to determine the thermal process necessary to give the required minimum Sterilisation Value, often cafled the scheduled heat process'. The schedified heat process defines at a specific temperature the time the retort takes to come up to temperature, the time at temperature and the cooling time to achieve sterility. It also defines, as necessary, such parameters as agitation rates and overpressure. These tests are typically carried out at a variety of sterilisation temperatures in the range 110°C to 125°C. The determination of the scheduled heat process, the process that will ensure commercial sterility' of all the contents of all the containers, is vital to the safety of the product produced. More detailed descriptions of the methods can be found in the literature.

Quality is currently usually assessed by opening containers sterilised at the different temperatures and speeds of rotation if applicable and deciding by taste and appearance which is best, for example by noting which has the east burn-on against the wall of the container or the least change in colour. In current practice Cook Values are rarely calculated as neither static nor rotary processing provide any effective means to control areas away from the cold spot to allow the production of a better product, so their determination woLild have little point, If they were calculated then typical Co vakies for a conduction product in a 400g can, sterilised to an Fo 6, would for a static retort, range from around Co = 100 in the centre to perhaps Co = 600 at the side and, for a rotary retort, from around Co = 100 at the centre to perhaps Co = 200 at the side. In both cases the mean and maximum Cook Values are far higher than ideal for many products and the range so large that much of the food may be severely overcooked with loss of flavour, colour, texture and vitamin retention and other organoleptic qualities. It should be noted that the ranges of Cook Values above are those from within a single container due to temperature differences and the range would be even greater when variations within and between retort loads are taken into account.

It should be noted that the prices of foods sterilised as above are typically half or less than similar recipe foods that are so'd as fresh, or that are merely pasteurised -a milder process -and sold from the chill cabinet. This is despite the great convenience advantage of sterilised foods -that they can be stored indefinitely at ambient temperatures. Both static and rotary sterilisation processes can compromise the quality of foods sufficiently to affect their value negatively.

If both Sterilisation and Cook Values could be controlled independently with some degree of precision, it was realised that ambient foods of far more consistent quality might be produced, foods of a quality that could be comparable to fresh cooked or pasteurised and probably of higher value than currently produced from retorts.

Starting with the Shaka® process referred to earlier, retort work was undertaken to see if it could be the basis for a further improved thermal process.

Experiments were initiated to find not only the cold spot in the container but also the hot spot' and so determine the temperature variation within a single container, as it is this variation that contributes so much to the wide range of Cook Values seen with products processed in current retorts..

The thermal data from both the hot and cold spots were taken, including those from both the heating and cooling part of the process, and the hot spot and cold spot Cook Values determined. The Cook Value from the cold spot can then divided by the value from the hot spot and converted to a percentage, defined as the Degree of Process Homogeneity (D0PH)'. A DoPH of 50% indicates a Cook Value at the hot spot twice that of the cold spot whereas a DoPH of 100% indicates complete homogeneity in the food container.

Using a variety of conduction products, foods and food simulants (Bentonite and starch solutions), a number of container types with thermocouples in a range of positions were tested. Tests on containers with up to four thermocouples in a single container were also undertaken. It was found that as the intensity of the reciprocal horizontal agitation increased so did the degrees of homogeneity. However, it initially appeared that, regardless of how high the rate of agitation, the degree of homogeneity would plateau and that co'd and hot spots could be not be eliminated.

It seemed unlikely that the degree of homogeneity would plateau in the manner seen so the experimental methodology was closely examined.

On closer examination it was found that the thin needle type thermocouples (- 1.5mm diameter) typically used for this type of experiment had to be of sufficient length to avoid undue conduction of heat from the outside of the container down the thermocouple casing which could cause higher temperatures to register than those actually present. It was found that thermocouples should be in excess of 30mm in length to avoid this effect. However, particularly with small containers, thermocouples of this length can be difficult to position to test all areas of the container and so flexible thin wire thermocouples were used.

Once the new methodology had been characterised it was found that, if high enough agitation rates were employed, hot and cold spots could be essentially eliminated and virtually 100% degree of process homogeneity achieved within individual containers.

The next phase was to determine the range due to variations between containers in a single retort load and between loads. The minimum Cook Value can be calcuthted, using the equation above and after selection of an appropriate z vfflue, from the same data used to determine the minimum Sterilisation Value (Fo), in the scheduled heat process, worst case' conditions. To determine the maximum Cook Value the best case' filling and processing conditions need to be determined. Best case' conditions can be regarded as the opposite of worst case', and are the conditions that give the fastest heating. In this context best case' conditions, even with particulate products, will be in the liquid phase. By using heat penetration data from the best case' together with the times and temperatures from the scheduled heat process the maximum Cook Value experienced in the liquid phase can be cakulated.

As noted above when determining Cook Values both the heating and cooling phases of the process need to be included.

When calculating Cook Values it is necessary to select suitable z values, as can be seen from the formula and discussion above. Typical z values fall in the range 25 - 33, the exact value depending on the characteristic of interest. If this characteristic is something such as retention of a particular vitamin then a suitable z value may be found and recommended in the literature. This is rarely the case if an organoleptic property for a particular product is of most interest. From the formuhi above, however, it can be noted that if a cooking temperature is near the reference temperature of 100°C then the value of z has little or no influence on the calculation of Cook Values. The z value can therefore be determined by using a scheduled or other suitable sterilisation process and retaining samples to test for taste and/or any other organoleptic properties of interest. Then the same product can be cooked, with stirring, at 100°C until its organoleptic properties matches as near as possible the sterilised samples, noting the time taken in minutes. This time in minutes will be the reference Cook Value, so using this reference Cook Value and time and temperature from the scheduled or other suitable sterilisation process in the Co equation above the z value for the given food can be calculated.

As will be seen from the formulae above the balance between Sterilisation Value (Fo) and Cook Value (Co) depends on the sterilisation temperature chosen. A high degree of homogeneity (DoPH) allows the use of a significanfly higher temperature range than that normally used in static or rotary retort sterilisation.

Thus by selecting the appropriate sterilising temperature, and agitation rate to achieve a high DoPH, suitable best case' and worst case' filling and processing conditions and correct z value, food products can be sterilised to the required Sterilisation Value for commercial sterility and now, at the same time, processed to be within, or close to, a targeted range of Cook Values, or other quality attribute, generally without the over-cooking, scorching and other disadvantages suffered by current ambient long shelf-life foods.

Agitation conditions close to DoPH of 100% would generally be targeted but for some situations particular features of the food product may need special attention so in that case other conditions may be selected.

In a further variation of this invention a stepped or multi stage process can be used in which the process is carried out in a number of phases to achieve a preferred Cook Value or other measure of quality. For example containers in the retort could be first heated to 100°C to accumulate some of the Cook Values required and then sterilised at, say, 130°C to give the target Sterilisation Value and remaining Cook Values required. Alternatively some of the Cook Values required can be accumulated in the product preparation phase before filling. Another option is to cook some components more than others and then, after filling and sealing the containers, sterilise as in the previous example.

Long shelf life foods to be stored under ambient conditions can thus be prepared to, or close to, a targeted range of Cook Values. So, for example, spring vegetable soups might be sterilised very quickly at a relatively high temperature to give a lightly cooked product, whereas a Hungarian stew might be sterilised more slowly at a much lower temperature to give a long cooked product.

As mentioned above, a targeted range of Cook Values for a particular food can be defined as the range of Cook Values that competent cooks would consider gave a satisfactory result when cooking food for immediate consumption. Competent cooks' would normally not determine Cook Values but as can be seen from the formula above at 100°C one unit of Cook Value is equal to one minute at 100°C, so, for example simmering a casserole for one hour would give a Cook Value of 60. The food should show no undesiraHe signs of discolouration or burning. For many recipe products, such as lightly flavoured sauces the amount of cooking required is Hmited and the Cook Vathe and range small, with a preferred Co of, say, around 15- 20. Other foods such as stews and casseroles which require more cooking to develop the desired flavour and texture will have a much wider range. For example a casserole might be simmered for 1-2 hours on the top of the stove giving a Cook Value, Co = 60 -120. In commercial production the Cook Value range should not be made unnecessarily tight.

From the formulae defined above it is evident that Sterilisation Values, where z = 10°C, increase with temperature much faster than Cook Values, where z = 25°C to 33°C.

In the accompanying graph below Sterilisation and Cook Values are shown plotted against temperature. As can be seen from the slope of the graph, once temperatures of around 130°C are reached, Fo values accumulate much faster than Co values thereby giving scope to target Co values independent to a significant extent of the Fo Sterilisation Value required. While it may not be possible to have an exceptionally low Cook Value at the same time as an exceptionally high Sterilisation Value, the range of Cook Values obtainable is sufficiently wide to encompass most desired cooked products from lightly cooked milk drinks and vegetable soups to well-cooked Hungarian goulashes or even pet foods.

For products where the pH is less than 4.5 (high acid), only pasteurisation is necessary (see definition above). This takes place at lower temperatures, up to a maximum of around 100°C, to produce containers of food that can be stored indefinitely. As will be appreciated from the much lower temperatures used in pasteurisation over-cooking is not usually an issue but for sensitive conduction products particularly in larger containers this method can be used to ensure the production of homogeneously pasteurised foods with minimal or no over-cooking.

INDUSTRIAL APPLICABILITY

Using in-container batch thermal processing, the present invention makes possiHe the production of long shelf-life ambient stored food products for which two of the most important process parameters can concurrently be tightly controlled to targeted values, independently to some sitificant extent. These parameters are the Sterilisation Value (or pasteurisation value), and the Cook Value or other expression of food organoleptic and quality attributes. The ability to control these two critical parameters with considerable precision, independently to a considerable extent, facilitates the production of significantly higher quality foods, such as soups, sauces, ready meals, desserts, baby-foods and pet foods, than have been achievable heretofore with in-container batch thermal processes.

Claims (19)

1. CLAIMS1. A process for the therma' treatment of food and beverage products characterised by concurrently sterilising to a required Sterilisation Value and cooking to a targeted range of Cook Values or other measure of quality by steps of heating, cooling and agitation of liquid-based foods or beverages, including those containing particles, in containers and determining the preferred process for a particular product container combination via the steps of: a. agitating by essentially horizontal agitation at a rate or rates sufficient to provide the required degree of process homogeneity (DoPH' as hereinbefore defined) within individual containers making up a load for processing and b. determining and controlling best case' and worst case' values, as hereinbefore defined, of parameters including variability of sterilisation temperature, initial product temperature, fill weight/headspace, product viscosity, liquid/solid ratio, particle size and agitation rate, and hence likely variation within the given retort load and between other loads for processing and c. selecting or determining a suitable z value for the food or beverage and d. selecting the appropriate sterilising temperature.
2. 2. A process as claimed in Claim 1 providing for in-container sterihsation for long term storage at ambient temperatures liquid-based foods or beverages, induding those containing particles, which without agitation would heat largely by conduction (Conduction Products').
3. 3. A process as claimed in any preceding claim in which the targeted range of Cook Values is selected as the range of Cook Vakies that competent cooks would consider gave a satisfactory or ideal result when cooking foods or beverages for immediate consumption.
4. 4. A process as claimed in any preceding claim in which the contained foods or beverages are low-acid', that is they have a pH> 4.5.
5. 5. A process as claimed in any preceding claim in which heat penetration data is used to determine scheduled processes at selected temperatures, and also to calculate the minimum Cook Values at these temperatures and maximum Cook Values are calculated by applying the times and temperatures of the scheduled processes to the heat penetration data from the best case' filling and processing conditions, and thus determine and select the preferred range of Cook Values.
6. 6. A process according to any preceding claim wherein there is provided an improved method for the determination of z value as aforesaid by thermally processing the given contained food using a scheduled or other suitable process to give the required level of sterilisation and then cooking a separate sample of the given food at 100°C, at which temperature the z value drops out of the equation, to the same flavour development or other measure of cooking as that of the sterilised sample, noting the time taken in minutes which will be the reference Cook Value, and then using the reference Cook Value and time and temperature from the scheduled or other suitable process in the Co equation to calculate the appropriate z value for the given food.
7. 7. A process according to any of preceding claim wherein there is used a method of determining and adjusting the contribution to the range of Cook Values from variations in individual containers using the degree of process homogeneity (D0PH) calcifiated by determining the Cook Values from the coldest and hottest regions of individual containers and dividing one by the other so that in the event the determined range of Cook Values is more than desired, a higher atation rate is used to enable a lower DoPH to be generated and thus narrow the Cook Value range.
8. 8. A process as claimed in any of preceding claims including a method of determining the contribution to lhe range of Cook Values from variations within and between retort toads from both the best case' and worst case' parameters and, by adjustment of these parameters which include variability of sterilisation temperature, initial product temperature, fill weight/headspace, product viscosity, liquid/solid ratio, particle size, agitation rate, adjust the contribution to the range of Cook Values to target a preferred cook value range.
9. 9. A process for the thermal treatment of food and beverage products characterised by determining the contribution to the range of Cook Values from the sterilisirig temperature or temperatures derived from the relationship shown in the Figure demonstrating that the Cook Value (Co) and Sterilisation Value (Fo) are related and that for the required minimum Fo the Co will vary with temperature and for a given case selecting a different temperature to enable the range of Cook Values to be changed to better target a preferred range.
10. 10. A process as claimed in any of the preceding claims in which for the contained liquid-based foods or beverages other suitable measure of quality include targeting a nutritional value or vitamin content of particular vitamin or vitamins, or preferred organoleptic property or properties.
11. 11. A process as claimed in any preceding claim characterised by increasing and/or decreasing the temperature and/or agitation rates in a step-wise fashion to obtain for the contained liquid-based foods or beverages a targeted range of Cook Values or preferred nutritional or organoleptic property or properties.
12. 12. A process as claimed in any preceding claimed characterised by being carried out in a number of stages to obtain for the container liquid-based foods or beverages a targeted range of Cook Values or preferred nutritional or organoleptic property or properties.
13. 13. A process as claimed in any preceding claim wherein the DoPH is determined by means of temperature measuring devices inserted in different positions within separate similar containers as an alternative, particularly for smaller containers and those containing significant particles, to positioning them within the same container.
14. 14. A process as claimed in any preceding claim in which the highest Cook Value within the contents of similar containers in a single load is limited to some 50% above the lowest Cook Value.
15. 15. Products produced by a process as claimed in any preceding claims including soups, sauces, dips, ready meals', baby foods, milk-based and other protein-based beverages, desserts, and pet foods.
16. 16. Products produced by a process as claimed in any preceding daim including catering products and preserved ingredients for subsequent use in the preparation of other food products.
17. 17. A process as claimed in any of preceding daim in which the sterilisthg step is replaced by a pasteurising step.
18. 18. Foods and beverages pasteurised as claimed in claim 17 including soups, sauces, ready meals, dips, baby foods, milk-based and other protein-based beverages, desserts', and pet foods.
19. 19. Food and beverage ingredients pasteurised as in daim 17 above including catering products and ingredients preserved for subsequent use in the preparation of other food products.Amendments to the claims have been filed as foHows:CLAIMS1 A method for establishing enhanced thermal treatment processes for liquid based food and beverage products including those containing particles which enable preferred closely defined Cook Values and Cook Value ranges for a given food products to be targeted while concurrently commercially sterilising to a required Sterilisation Value, comprising the steps of: a) selecting a preferred Cook Value and a range of Cook Values within which the product quality remains acceptable or alternatively determining a preferred Cook Value and range for example by preparing the product as if for immediate consumption and then varying the cooking time and hence Cook Value to determine the preferred Cook Value and the range within which the product quality remainsacceptable;b) selecting a sterilising retort and conditions estimated to have a suitable degree of r process homogeneity DoPH' within a single container, as previously defined, to target the Cook Value range determined as in a) above; c) se'ecting an estimated sterilising temperature, and determining the time needed to meet the required Sterilisation Value while targeting the preferred Cook Value and range as selected or determined as in a) above; d) repeating b) and c) above and by adjusting the DoPH, temperature and hence time, until Cook Values and range close to or within the preferred Cook Value and range are achieved; e) determining the Cook Vfflue zcfor the product by the method as hereinbefore described and then recalculating Cook Value and range achieved in the best process as in d) above; F) determining both Best Case and Worst Case Cook Values and ranges between different contathers in the load or loads as hereinbefore described, thus necessarily broadening the range from e) above; g) comparing Cook Values and ranges from a) and f) and controlling Best Case and Worst Case parameters, selecting the DoPH and/or sterilising temperature and hence time, possibly reformulating the product, if necessary to better target the preferred Cook Value range; h) selecting and applying the optimum parameters from above to the manufacture of food and beverage products with closely targeted quality parameters, while concurrently commerciafly sterilising.2 A method as claimed in Claim 1 wherein a measure of quality other than Cook Value is chosen 3 A method as claimed in Claim 1 wherein the process is used for foods or beverages, which without agitation woffid heat and cool thrgely by conduction (Conduction Products').4 A method as claimed in any preceding claim wherein the foods or beverages being processed are low-acid', that is they have a pH >4.5.A method as claimed in any preceding claim wherein the targeted range of Cook Values, or other suitable quality measure, is selected as the range of Cook Values, or other suitable quality measure, that competent cooks would consider gave acceptable results when cooking foods or beverages for immediate consumption.6 A method as claimed in any preceding claim including the steps of determining and adjusting the contribution to the range of Cook Values, or other suitable quality measures, from variations in individual containers using the degree of process homogeneity (D0PH) cakuhited by determining the Cook Values, or other suitable quality measures, from the coldest and hottest regions of individual containers and dividing one by the other so that in the event the determined range of Cook Values, or other suitable quality measure, is more than desired, a sterilising retort and conditions with a higher DoPH is selected to narrow the Cook Value, or other suitable quality measure, range.7 A method as claimed in any preceding claim including the step of determining of ze values for selected orgamoleptic quality or other qualities for a given food or beverage product as hereinbefore described by thermally processing the given contained food using a scheduled or other suitable process to give the required eve of sterilisation and then cooking a separate sample of the given food at 100°C, at which temperature the Zc value drops out of the equation, to the same flavour development or other aspect according to any other (organoleptic) measure of cooking as that of the sterilised sample, noting the time taken in minutes which will be the reference Cook Value, and then applying the reference Cook Value and time and temperare from the scheduled or other suitable process in the Co equation to calculate the appropriate Zc value for the given organoleptic measure, or other measure of quality, of the given food or beverage (sJ and hence the more accurate calculation of Cook Values to be used in the determination r of the process parameters.8 A method as claimed in any preceding claim including the step of using heat penetration data to determine the scheduled processes, or other suitable sterilisation processes, at selected temperatures, and also to calculate the minimum and maximum Cook Values, or other suitable quality measures, at these temperatures calculated by applying the times and temperatures of the scheduled, or other suitable processes to the heat penetration data from the Worst Case and the Best Case filling and processing conditions respectively, and thus determine the Cook Value and range of Cook Values, or other suitable quality measures, in order to refine the control of the process.9 A method as claimed in any preceding claim including the step of determining the contribution to the range of Cook Values, or other suitable quality measures, from variations within and between retort loads from both the Best Case and Worst Case parameters and, by adjustment of these parameters which include variability of sterilisation temperature, initial product temperature, fill weight/headspace, product rheology, liquid/solid ratio, particle size, agitation rate, adjust the contribution to the range of Cook Values to target for the process a preferred Cook Value, or other suitaHe quality measure, range.A method as claimed in any preceding claim when characterised by the step of increasing and/or decreasing the temperature and/or agitation rates in a step-wise fashion to obtain for the contained liquid-based foods or beverages a targeted range of Cook Vathes or preferred nutritional or organoleptic property or properties.11 A method as claimed in any preceding claim when characterised by processing in a number of stages typically including pre-cooking to varymg degrees components making up the food product before they are combined together packed and sterilised to provide for the processed liquid-based foods or beverages the preferred range of Cook r Values or other nutritional or organoleptic property.12 A method as claimed in any preceding claim wherein the DoPH is determined by means of temperature measuring devices inserted in different positions within separate similar containers as an alternative, particuthrly for smaller containers and those containing significant particles, to positioning them all within the same container.13 A method as claimed in any preceding claim including the step of regulating the process so that the highest Cook Value within the process contents of conduction products in similar containers in a single load is limited to some 25% above the lowest Cook Value.14 Enhanced thermal treatment processes, induding scheduled processes developed in accordance with any of the above methods in any of the above claims.Products, when processed according to the method of any preceding claim, including soups, sauces, dips, ready meals', baby foods, milk-based arid other protein-based beverages, desserts, and pet foods.16 Products, when processed according to the method of preceding claims 1 -14 including catering products and preserved ingredients for subsequent use in the preparation of other food products.17 A method according to the method of preceding Claims 1 -14 wherein the sterilising step is replaced by a pasteurising step.18 Products, when processed according to Claim 17, including foods and beverages such as soups, sauces, ready meals, dips, baby foods, milk-based and other protein-based beverages, desserts, and pet foods.19 Products, when processed according to Claim 17, including catering products and ingredients preserved for subsequent use in the preparation of other food products. r (Si