Refrigeration – Processes – Treating an article
Patent
1992-11-23
1994-04-05
Capossela, Ronald C.
Refrigeration
Processes
Treating an article
62374, F25D 1306
Patent
active
052994260
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a process and an apparatus for freezing a product, for example a food product, in order to freeze at least one of its surfaces.
The freezing of food products is normally carried out in freezing tunnels where the cold is obtained by mechanical means.
These food products which are intended to be frozen are often sticky and adhere to the moving carpets of the freezing tunnel on which they are conveyed, thus causing a problem of maintenance and hygiene.
Moreover, these products may not be too compact and they easily fall into pieces, thus losing the shape intended therefore, during their handling. This is the case, for example, of balls of vegetable puree, which are extremely difficult to handle.
Processes for freezing food products have already been proposed, according to which the products to be frozen are placed on a metallic support of which the temperature has previously been lowered so that only the surface of the products in contact with the metallic support is frozen. The temperature of the support may for example be lowered by means of a cryogenic gas which circulates in a trough placed below said support. Depending on the nature of the support and its heat conductivity, temperatures of the order of -60.degree. C. to -90.degree. C. may be reached.
However, it has been observed that these processes could have disadvantages, in particular when treating products which are particularly sticky, such as balls of vegetable puree.
According to these processes, these balls adhere to the wall until their surface could be sufficiently cooled down, thus resulting in a period of latency which delays the treatment of products upstream of the production line.
Such a period of latency may then lead to a substantial decrease of productivity.
The process according to the present invention enables to prevent the adhesion of the products to be frozen on the support, even when they are very sticky, thereby permitting a substantially improved productivity and a great facility of maintenance.
Moreover, according to such a process, the nature of the support has little importance, in particular the support does not have to be made of a material which has a good heat conductivity.
According to another aspect of the process of the invention, the means used may easily be adapted to any type of products to be frozen, by relying on simple adjustments.
The present invention therefore concerns a process for freezing a product, for example a food product, characterized in that said product is contacted with a film made of a liquefied gas of which the boiling point is below -30.degree. C., which is disposed at the surface of a horizontal or downwardly sloping vibrating support, and the product at least partially frozen is separated from said film of liquefied gas.
Surprisingly, it has been observed that even very sticky products, do not adhere to the support, in spite of the fact that the film may be very thin.
Without being bound to a theoretical explanation, it is believed that the treated product floats at the surface of the film of liquefied gas through a phenomenon of calefaction, thereby preventing any risk of adhesion on the support. Moreover, the direct contact between the product and the film of liquefied gas whose temperature may be very low, enables a nearly immediate freezing of the surfaces of the product in contact with the film of liquefied gas.
Within the scope of the invention, the products to be frozen are essentially food products which can be in solid state, in particular slices of fish or meat, minced or not minced, cakes, pizzas, whole or cut vegetables, which can be in a pasty state, such as balls of vegetable puree. These products may be possibly in semi-liquid or even liquid state.
Besides food products, it is also possible to treat industrial products such as fatty materials or waxes whose melting points are near room temperature. The process according to the invention is particularly suitable for the treatment of solid or pasty products which are in final shape and for which th
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Capossela Ronald C.
L'Air Liquide, Societe pour l'Etude et l'Exploitation des Prooce
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