A METHOD FOR THE COOLING OF A PRODUCT FLOW CONTAINING SOLID AND/OR SEMISOLID FOODSTUFF PARTICLES

Abstract: A method for the cooling of a heated, e.g. heat-sterilized, flow containing particles of foodstuff character. The flow is separated into a high-particle and a low-particle fraction which is cooled separately and is used later as a cooling medium for the cooling of the high-particle fraction. The method is intended in the first place to be used in so-called aseptic packaging according to which the heat-treated, cooled foodstuff product, e.g. fruit soup, vegetable soup, meat broth etc. is packed in sterilized packing containers, or in packing containers manufactured from sterilized packing material, under aseptic packing conditions.

Description: The present invention relates to a method for the cooling of a heated flow containing solid and/or semisolid product particles of foodstuff character. In packing technology frequently so-called aseptic packaging is used for the packing of particularly bacteria-sensitive and storage-sensitive products, e.g. foodstuffs, which can be rapidly destroyed or seriously impaired if they are subjected to uncontrolled microbiological influences. Aseptic packaging in principle is based on the concept that the product which is to be packed should first be sterilized and subsequently be packed in separately sterilized packing containers, or in packing containers manufactured from sterilized packing material, under sterile or aseptic conditions so as to prevent a reinfection of the sterilized product. The aseptic packing technique has a number of advantages over other conventional, non-aseptic packing technique from a point of view of keeping property of the product as well as of distribution. This means, inter alia, that the aseptically packaged product, whilst preserving virtually unchanged freshness qualities can be stored during appreciably longer storage periods than is the case for a corresponding, non-aseptically packed product, and moreover such storage of the aseptic product during the whole of its handling, from the actual packaging to the final consumer, can take place without any need for cold storage or unbroken cooling chain, which appreciably facilitates the distribution of the product. Since bacteriia and other microorganisms generally are very temperature-sensitive and rarely survive at temperatures above approx. 100-110°C it is customary for product sterilization on aseptic packages to be carried out by means of a controlled heat treatment which means that the product according to a predetermined time/temperature scheme is heated to, and is maintained at, a temperature which is high enough for the desired killing or sterilizing effect, whereafter the product is cooled and is then packed. With the help of modern aseptic packing machines of the type which form, fill and close finished packages it is possible at present to carry out the whole aseptic packing procedure, including product sterilization, continuously on a large scale. A heat treatment of the type which has been described above is both simple and in general functions well with foodstuffs of the type of milk, juice or other liquid or pumpable, homogeneous products, but may become more problematic and difficult to carry out with more heterogenously composed foodstuffs which at the same time contain both solid and liquid components. Examples of products of the last-mentioned heterogeneous type are, for example, meat broths, vegetable soups and similar mixtures of sauces/juices and meat/fruit pulp particles. Foodstuffs, whether they are in solid or liquid form, are heat-sensitive and may easily be damaged by a heat treatment if the same is too extensive and/or is performed at too high a temperature. In order to avoid such a damaging heat effect it is important, therefore, for the sterilizing heat treatment to be carried out at a predetermined temperature, right for the particular foodstuff, which on the one hand should be sufficiently high so as to ensure the sterilizing effect aimed at, but which on the other hand should not be high enough for the foodstuff to suffer damage or even risk to suffer damage by the treatment, and that the extent of the heat treatment, moreover, is adapted so as to keep the total heat load on the foodstuff within such limits that the smallest possible negative effect on the qualities of the product is assured. This means in practice that the actual heating process to the desired sterilization temperature preferably should be as rapid as possible, and that the cooling process after the sterilization too ought to be carried out rapidly, so that the total heat load on the foodstuff can be kept to a minimum without the sterilization effect being neglected. With the help of so-called ohmic heating, which is based on converting electric energy into thermal energy directly in the foodstuff by allowing an electrically conductive flow of the product to pass between oppositely charged electric voltage poles, it is now possible to achieve a very rapid heating and accordingly a limited heat load on the product inasfar as the heating part of the sterilizing process is concerned. However, it has proved to be more difficult to cool the heated product flow equally quickly, or at least sufficiently quickly, in order to contribute here too to a minimizing of the total heat load on the product. The problem concerns in particular highly viscous, heterogeneous product types containing both liquid and solid or semisolid components of the afore-mentioned type, and to a large extent is connected with, or is due to, the fact that as a rule it is much easier to cool the liquid element in the product whereas the solid or semisolid components require longer cooling periods and thereby limit the possibilities of being able to carry out the cooling process with the desired minimum expenditure of time. The drawn-out cooling process and the increased heat load connected therewith often has led to the solid and/or semisolid components of the finished product to a corresponding degree having been subjected to an impairment of quality which expressed itself, among other things, in a partially lost nutritional content, impaired chewing resistance and also generally negatively affected organoleptic properties, at the same time as the enforced relatively long cooling transport distances by means of pumps, because of their mechanical effect on the product, contributed further to an impairment of the qualities of the product. It is an object of the present invention, therefore, to indicate a new method of cooling a heated or heat-treated flow containing solid and/or semisolid particles of foodstuff character without the associated inconveniences of the type discussed above. It is another object of the invention to indicate a method for the cooling of heterogeneously composed, highly viscous products which is both rapid and effective and which can be integrated very well in a continuous, aseptic packaging process using modern, rational packing machines. These objects have been achieved in accordance with the present invention in that the method described in the introduction has been given the characteristics described in detail in the following claim 1. Preferred practical embodiments of the method in accordance with the invention have been given, moreover, the characteristics specified in the following subsidiary claims. In the following the invention will be described and explained in detail with special references to the attached drawing which illustrates schematically how the method in accordance with a preferred embodiment of the invention is intended to be carried out in connection with the heat sterilization of a flow containing solid and/or semisolid foodstuff particles. The drawing thus shows schematically a system for heat sterilization and subsequent cooling of a foodstuff flow containing both liquid and solid or semisolid phases, e.g. a vegetable soup or a meat/sauce mixture. The system comprises a heating or heat-sterilizing device 1 with an inlet pipe 2 and an outlet pipe 3 which in turn is connected to a shunt or parallel duct 4 at branch points 5 and 6 located upstream and downstream respectively. In the duct circuit 4 is arranged a heat exchanger and cooling device 7 and a pump 8 located before the downstream branch point 6. The outlet pipe 3 may be connected after the downstream branch point 6, for example, to the product filling pipe of an aseptic packing machine, not shown, of the type which forms, fills and closes aseptic packages under aseptic conditions. The heating device 1 may be a conventional heat exchanger device of the plate type, but is preferably an ohmic heating device which very rapidly heats the product intended for sterilization to a predetermined, suitable sterilization temperature. The heat exchanger or cooling device 7 too may be of the plate type or of some other known kind. By means of the system shown, the method in accordance with the invention is carried out in the following manner. The product, for example vegetable soup or sauce/meat mixture, is conducted through the inlet pipe 2 into the heating device 1 and is heated to a predetermined sterilization temperature. The heated or sterilized product is discharged through the outlet pipe 3 and is divided into a high-particle flow and a low-particle flow. The low-particle flow is discharged from the pipe 3 through the duct 4 with the help of any suitable separating device which readily lets through the liquid product phase but which on the other hand prevents particles above a certain minimum particle size from passing through the separating unit into the duct 4 and be pumped with the help of the pump 8 through the heat exchanger and cooling device 7 for cooling by means of heat exchange with a colder medium in a manner known in itself. From the device 7 the cooled, low-particle flow is pumped back into the outlet pipe 3 at the branch point 6 where the cooled flow is remixed with the high-particle flow separated at the branch point 5. At the remixing point 6 a spontaneous intimate contact occurs between the cooled flow and the particles in the warmer flow which thereby are effectively cooled and partly continue to be cooled during the further progress of the combined flow through the pipe 3 into the packing machine, not shown in the drawing. With the help of the method in accordance with the invention it is thus possible to cool very rapidly the heated or heat-treated product flow containing solid and/or semisolid foodstuff particles, and, in particular, the method has been found to be specially effective in the cooling of more highly viscous product mixtures containing particle fractions larger by volume than the liquid phase . An effective and rapid cooling is achieved even if the volume of the liquid component of the product mixture amounts to not more than a few per cent (%) of the solid or semisolid phase.

Claims: A method for the cooling of a heated product flow containing solid and/or semisolid particles, of foodstuff character characterized in that the flow is separated into a high-particle flow and a low-particle flow and that the low-particle flow is cooled and is used subsequently as a cooling medium for the high-particle flow. A method in accordance with claim 1, characterized in that the cooled, low-particle flow is remixed with the high-particle flow at a point down-stream of the separation. A method in accordance with claim 1 or 2, characterized in that the cooled low-particle flow is pumped back to mix it again with the high-particle flow. A method in accordance with anyone of the preceding claims, characterized in that the separating is carried out in such a manner that the low-particle flow is smaller by volume than the high-particle flow. A method in accordance with claim 4, characterized in that the low-particle flow has a volume amounting to only a few per cent (%) of the volume of the high-particle flow. A method in accordance with anyone of the preceding claims, characterized in that the product flow is heat-treated by means of so-called ohmic heating. Use of the method as claimed in anyone of the preceding claims for packaging foodstuff comprising meat, fruit or vegetables as solid or semisolid particles.

Inventors: RAUSING, HANS
Applicants: TETRA ALFA HOLDINGS S.A.
Application year: 1990
Main classification: A23L1
IPC codes: A23L1, A23B4, A23L2, A23L3, B65B55