Refrigeration – Processes – Treating an article
Patent
1998-04-07
1999-04-13
Capossela, Ronald
Refrigeration
Processes
Treating an article
62 63, 62374, F25D 1304
Patent
active
058932704
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement and a method for continuous cooling of food products which have been heat treated by heating to a high temperature in a heat treatment unit.
When heat treating food products to high temperatures one strives after achieving a certain combination of time and temperature at a desired high sterilization temperature. The temperature and the time are then in contradiction with each other in such a way that the higher the temperature the shorter is the holding time needed in order to achieve a desired killing of microorganisms. Usual temperature combinations at sterilization are within the field 135-150.degree. C. at 10-2 seconds. In order to avoid any influence on the different nutritive substances in the product one tries both to heat and cool rapidly and at that desires to keep the time during which the product is heated to temperatures above 100.degree. C. as short as possible.
During the latest time one has found certain especially heat resistant spores in different food products, which means that one has been forced to heat treat at a very high temperature in order to obtain sterility.
In indirect cooling from such a high temperature one usually works with a relatively large difference in temperature between the cooling medium and the food product in order to obtain a high cooling rate. In such a rapid cooling there may be problems with fouling on the product side in the cooling means (heat exchanger) that are used. This fouling may impair the heat capacity and at that lower the cooling effect. The fouling may also lead to a short operation time, such that cleaning of the heat exchangers must take place after only 10-12 hours.
According to the invention there is now proposed a solution to these problems which makes the operation time considerably longer before the heat treatment plant must be stopped to clean the cooling means.
The arrangement according to the invention is mainly characterized in that it is connected between a holding cell in a heat treatment unit and a further treatment unit and that it comprises at least two indirectly working cooling sections through which the product is forced to pass. During a first period only the first cooling section is active, i.e. cooling medium passes in counter current through the cooling section, while during a second following period a second cooling section is activated in that cooling medium passes also this cooling section in counter current. The second cooling section is arranged after the first cooling section as seen in the flow direction for the product. In such an arrangement there is obtained a rapid increase of the available cooling effect in a simple manner.
Each cooling section may comprise one or several tubes or plate heat exchangers connected in series.
The further treatment unit may consist of a flashing step if the heating of the product to sterilization temperature has taken place by direct steam injection into the product. If the heating takes place by indirect heat exchange the following treatment may consist of a further cooling step.
With advantage the arrangement is designed such that the product channels of the first and the second cooling sections are connected in such a way that the product during the first as well as the second period passes through both cooling sections.
Alternatively, a change over may take place in the product conduit in such a way that this second cooling section is put in circuit first during the second period. However, this means a change of the flow conditions for the product which momentarily may give rise to pressure drops which disturb the function of the heat treatment unit.
The arrangement according to the invention may preferably have a conduit for cooling medium connected to the outlet side of the first cooling section and means arranged to gradually increase the flow in a second conduit during the second period until the whole flow of cooling medium has been brought to pass as well the first as the second cooling section.
An arrangement according to the i
REFERENCES:
patent: 3805538 (1974-04-01), Fritch, Jr. et al.
patent: 4265096 (1981-05-01), Andersson
patent: 4278698 (1981-07-01), Mauer
Capossela Ronald
Tetra Laval Holdings & Finance S.A.
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