METHOD AND PLANT FOR COATING FOOD PRODUCTS

Description

[0001] The present invention relates to a method and an installation for coating food products with a liquid or pasty coating substance, of the type comprising a step of bringing the food products into contact with the coating substance and a step of supplying external cold to cause the coating substance to freeze around the products.

[0002] Frozen ready meals commonly have a center made up of a food product such as meat, fish, a vegetable, or even a pastry, completely surrounded by a frozen coating (sauce, oil, chocolate, etc.).

[0003] The coating of food products, from the initially liquid or pasty sauce, is carried out in a mixing device, commonly called a "churn", which is equipped with a device for injecting refrigerant, for example liquid nitrogen or liquid carbon dioxide.

[0004] The mixing device consists of a rotating cylindrical tank with a horizontal axis. It has internal blades for mixing the products. The refrigerant is most commonly injected along the axis of the tank.

[0005] To ensure the coating of the products, a batch of pre-cooled, most often pre-frozen, food products is introduced into the tank. While the tank is rotated, phases of injection of sauce at room temperature and phases of injection of refrigerant fluid are carried out. Thus, the frozen food products, being constantly mixed in contact with the sauce, are gradually coated by the sauce solidifying under the action not only of the frigories provided by the injected refrigerant fluid but also by transfer from the product which was pre-frozen.

[0006] Food products coated in such an installation have a number of appearance defects resulting from the mechanical stresses applied to the product when the tank and blades rotate.

[0007] It is further noted that some sauce particles are frozen away from the products to be coated, and therefore constitute unwanted particles commonly referred to as "fines".

[0008] Document FR-2 789 270 illustrates this prior art. Documents EP 0 893 070, EP 0 530 014, US 4 708 881, EP 0 091 497 and WO 00 / 16645 also disclose examples of the prior art.

[0009] The present invention aims in particular to provide a method and an installation for coating food products making it possible to provide a solution to the technical problems mentioned above, and in particular: to obtain coated products with an improved visual appearance; to obtain better control of the coating rate achieved; to improve process consumption.

[0010] To this end, the invention relates to a method for coating food products with a coating substance, of the type comprising a step of bringing the food products into contact with the coating substance, and where before bringing the food products and the coating substance into contact, the food products are sub-cooled by supplying external frigories to a temperature lower than their initial temperature, and where the food products and said coating substance are then subsequently brought into contact without supplying external frigories, the coating around the products being frozen under the action of the transfer of frigories from the sub-cooled products to said coating substance, characterized in that the sub-cooling of the products is carried out in a hopper (which may in particular have a cylindrical or pyramidal base), capable of being supplied with the product to be coated, which hopper is provided with means for supplying a cryogenic fluid,the hopper being provided in its lower part with a hollow screw provided with turns ensuring the conveyance of the product and allowing the product to be poured out of the hopper towards the step of bringing the food products into contact with the coating substance, said means for supplying a cryogenic fluid into the hopper comprising an injection pipe, for example of the orifice clarinet type, which is positioned inside the turns of the hollow screw, extending in a direction substantially parallel to the axis of the screw.,

[0011] Depending on particular methods of implementation, the method may include one or more of the following characteristics: 1.the initial temperature of the products, before the subcooling phase in the hopper, corresponds to a frozen state, therefore typically at a temperature between -12 and -20°C. In fact, it is necessary to consider the fact that depending on the subcooling temperature obtained in the hopper, a given coating rate is obtained (depending on the temperature of the sauce), the objective here being to try to obtain a stable average temperature of the product to be coated. 2. the initial temperature of the products, before the sub-cooling phase in the hopper, is less than or equal to 6°C. 3.the method comprises, after the step of bringing the sub-cooled products into contact with the coating substance, a subsequent step of cooling the coated food products by supplying external frigories. As will be clear to those skilled in the art, during or after the deposition of coating (for example of sauce), the sub-cooling energy has made it possible to freeze the sauce on the surface, also to stabilize the product and avoid sticking phenomena it is advantageous to implement cooling equipment which can for example be a freezing tunnel or equipment using a cryogen bath. 4. the food products are sub-cooled in the hopper to a temperature between -20°C and -80°C, and advantageously between -30°C and -60°C. 5. the coating substance is substantially at room temperature when it comes into contact with food products.

[0012] As we have seen, the supply of cryogen into the hopper is carried out, in whole or in part, using an injection rod (of the orifice clarinet type), positioned within (inside) the hollow screw, i.e. its turns. According to the invention, in addition to this injection rod, it is possible to use an additional means of supplying cryogen into the hopper (for example those conventionally used such as an injection torus).

[0013] We will not dwell here on the structure of such injection clarinets, well known to those skilled in the gas field, the sizing of which and in particular the number of injection holes will be determined on a case-by-case basis by a thermal calculation of the need for frigories for the maximum flow rate of products.

[0014] Preferably, the rod in question is vacuum insulated or otherwise.

[0015] According to an advantageous embodiment of the invention, the injection into the rod is regulated (and if an additional torus is present, the injection into this torus is advantageously fixed and not regulated), using a temperature measurement (preferably by thermocouple) at the outlet of the hollow transfer screw, in the product outlet zone of the screw towards the equipment for contacting with the coating (in this zone, the product falls, it is no longer in the hollow screw), TOR regulation (all or nothing), or preferably a PID regulation with a TOR valve, or even a proportional valve for the injection rod and TOR for the complement of the torus in the hopper.

[0016] The invention further relates to an installation for coating food products with a substance, for example a sauce, of the type comprising means for bringing the food products into contact with the coating substance, as well as means for, before bringing the food products and the coating substance into contact, sub-cooling the products by supplying external frigories to a temperature lower than their initial temperature, and thus the fact that the food products and said coating substance are then subsequently brought into contact without supplying external frigories, the coating around the products being frozen under the action of the transfer of frigories from the sub-cooled products to said coating substance, characterized in that the means for sub-cooling the products comprise a hopper, capable of being supplied with the product to be coated, which hopper is provided with means for supplying a cryogenic fluid,the hopper being provided in its lower part with a hollow screw provided with turns allowing the conveying and pouring of the product out of the hopper towards the step of bringing the food products into contact with the coating substance, said means for supplying a cryogenic fluid into the hopper comprising an injection pipe, for example of the orifice clarinet type, which is positioned inside the turns of the hollow screw, extending in a direction substantially parallel to the axis of the screw.,

[0017] There Figure 1 attached provides a partial schematic view of a hopper 10 according to the invention, equipped in its base part with a hollow transfer screw 11 and a cryogen injection rod 12 located within the hollow screw, i.e. within the rings of the hollow screw. The screw 11 allows the product to be poured out of the hopper towards the subsequent step (13) of bringing the sub-cooled food products into contact with the coating substance.

[0018] The results of the experiments carried out by the Applicant under these conditions showed the following points: homogeneity of the sauce rate on the products, no deviations over time. Fine regulation of the subcooling temperature in the hopper, even for very high flow rates (up to 4 tonnes / h) with a very short residence time. No deterioration of the product in this subcooling system (contrary to what was observed in churns) therefore no creation of product fines to be coated.

Claims

1. Method for coating food products with a coating substance, of the type comprising a step of bringing the food products into contact with the coating substance, and wherein, before the food products and the coating substance are brought into contact, the food products are subcooled to a temperature below their initial temperature by adding external cold energy, and wherein the food products and said coating substance are then subsequently brought into contact without adding external cold energy, the coating around the products being frozen by cold energy being transferred from the subcooled products to said coating substance, characterized in that the subcooling of the products takes place in a hopper (10), which can be supplied with the product to be coated, said hopper being provided with means for supplying a cryogenic fluid, the hopper being provided, in its lower part, with a hollow screw (11) provided with turns allowing the product to be conveyed and discharged out of the hopper towards the step of bringing the food products into contact with the coating substance, said means for supplying a cryogenic fluid into the hopper comprising an injection tube (12), for example of the manifold type with orifices, which is positioned inside the turns of the hollow screw, extending in a direction substantially parallel to the axis of the screw.

2. Method according to Claim 1, characterized in that the temperature of the products entering the hopper is in the range from -12 to -20°C.

3. Method according to Claim 1, characterized in that the temperature of the products entering the hopper is less than or equal to 6°C.

4. Method according to one of the preceding claims, characterized in that, after the step of bringing the products subcooled in the hopper into contact with the coating substance, a subsequent step of deep-freezing the coated products is carried out by adding external cold energy.

5. Method according to one of the preceding claims, characterized in that the food products are subcooled in the hopper to a temperature of between -20°C and -80°C, and advantageously of between -30°C and -60°C.

6. Method according to one of the preceding claims, characterized in that the coating substance is substantially at ambient temperature when it is brought into contact with the subcooled products.

7. Method according to one of the preceding claims, characterized in that said supplying means comprise, in addition to the injection tube, a torus for injection of cryogen into the hopper.

8. Method according to one of the preceding claims, characterized in that the injection of cryogen into the tube is regulated by measuring the temperature of the product at the outlet of the screw, in the region in which the product falls from the screw towards the equipment in which it is brought into contact with the coating substance.

9. Installation for coating food products with a substance, for example a sauce, of the type comprising means for bringing the food products into contact with the coating substance, as well as means enabling, before the food products and the coating substance are brought into contact, the products to be subcooled to a temperature below their initial temperature by adding external cold energy, characterized in that the means for subcooling the products comprise a hopper (10), which can be supplied with the product to be coated, said hopper being provided with means for supplying a cryogenic fluid, the hopper being provided, in its lower part, with a hollow screw (11) provided with turns allowing the product to be conveyed and discharged out of the hopper towards the step of bringing the food products into contact with the coating substance, said means for supplying a cryogenic fluid into the hopper comprising an injection tube (12), for example of the manifold type with orifices, which is positioned inside the turns of the hollow screw, extending in a direction substantially parallel to the axis of the screw.

10. Installation according to Claim 9, characterized in that said supplying means further comprise a torus for injection of cryogen into the hopper.