"Gas injection lance for food extruder"

Abstract

A lance (1) for injecting a cryogenic fluid into a food product circulating in an installation for shaping this product by cryoextrusion, the lance comprising the following elements: A non-return valve (2), positioned upstream of the point of injection of the fluid into the product, capable, in the event of the presence of product in the lance, of preventing this product from flowing further upstream of the lance; A spring-loaded check valve (3), calibrated, the check valve being thus capable of opening only when the pressure at the point of injection into the product is less than a given setpoint, for example 1 bar below the pressure in the lance; A hollow ring (4), located downstream of the check valve, at the end of the lance, which allows the opening and closing of the check valve; And comprising, where applicable, a porous element or a grid (5), at the end of the lance, integral with the ring, capable of breaking the gas flow and promoting the formation of small gas bubbles.Figure 1 .

Description

Title of the invention: "Gas injection wand for food extruder"

[0001] The present invention relates to the field of the food industry, and more particularly to cold extrusion processes of food products for shaping.

[0002] In what follows we will speak interchangeably of extrusion, cryoextrusion, cold extrusion, extruder, these terms are perfectly identified for the person skilled in the art, some also use the term "mixer" or "screw mixer".

[0003] The shaping of food products has become a major issue for manufacturers in recent years. Indeed, consumers are increasingly demanding portioned food products in original and varied shapes, allowing them to easily measure the quantities needed for their meals and also appealing to their taste buds. Another challenge is to provide food professionals with easily usable portioned products.

[0004] To meet this requirement, manufacturers have various techniques at their disposal, which are however not entirely satisfactory.

[0005] The simplest technique is the cookie cutter or mold technique. The major drawback of this technique is that it does not allow for complex shapes or the use of liquid raw materials; moreover, it is a significant source of waste that is difficult to reuse given increasingly stringent food standards.

[0006] Another commonly used technique is the "ball machine," consisting of two counter-rotating hollow cylinders between which a pre-frozen or unfrozen food paste is poured. The paste then emerges in the form of "balls," i.e., "pellets," which can then be frozen. This process is used to manufacture frozen food products such as block soup, portioned spinach, etc. The products obtained in this way are unsatisfactory because not only do they have an unattractive appearance, requiring the use of opaque packaging, but their shape is also limited by the geometry of the machine, which only allows for the production of balls, and certainly not playful shapes, for example, for children. Finally, it is impossible to precisely measure the quantity of food product in the "balls." Product losses are also significant.

[0007] Another technique now favored is the extrusion of food products, in particular cold extrusion. Many food products can be Extradermated materials, whether solid or semi-solid, such as dough for bread, biscuits or snacks, starches, vegetables, meats, ice cream, chocolate, soft candies, chewing gum, fruit paste, caramel, cereals, vegetable proteins, casein, processed cheese, animal feed, etc. (this list is by no means exhaustive). It should also be noted that this technique is increasingly being considered for the production of protein-based products that are alternatives to conventionally extracted proteins.

[0008] Typically, an industrial extruder consists of a long cylinder containing at least one extrusion screw, with a product feed hopper at one end and an outlet nozzle at the other. Generally, the extrusion screw is driven by a rotary motor whose rotational speed is controlled by a frequency inverter.

[0009] During low-temperature extrusion, the products are either cooled or even frozen upstream of the extrusion step, as described, for example, in document US-4,795,650, or the products are directly cooled or even frozen in the extruder itself. In the latter case, either the cooling is carried out externally on the extruder, i.e., a cooling fluid circulates around the body of the extruder, for example, brine, ammonia, glycol water, liquid nitrogen, carbon dioxide, as described, for example, in US2003 / 0211192 or US2005 / 0132902; or the cooling is carried out by direct contact by injecting a cooling fluid into the extruded product, as described, for example, in documents EP-0250381 or US-2006 / 0283196.

[0010] According to one known version of cryoextrusion, the refrigerant circulation system consists of a double jacket surrounding the extrusion screw and through which a refrigerant circulates. The double jacket can be made up of several independent modules connected to each other by pipe-type conduits, allowing the refrigerant to pass from one module to another. The extrusion screw(s) are positioned within the cylinder formed by the combined modules of the double jacket. Each module is equipped with its own refrigerant inlet and gas outlet. In some cases, some of the modules are connected in series for gas circulation, two by two.

[0011] These processes, while theoretically attractive, are difficult to implement industrially. Indeed, they present the major drawback of jamming the extruder screw(s) due to an excessively rapid drop in product temperature. Specifically, when the temperature of the extruded food product falls too quickly, its viscosity increases very rapidly, leading to an increase in torque on the screw(s) and therefore in motor current, thus triggering the motor's thermal protection and causing it to jam. For this reason, this type of The cold extrusion process is difficult to use as such in industry for shaping food products with high viscosity.

[0012] Furthermore, it should be noted that controlling the exit temperature of the products proves to be very difficult in practice.

[0013] Since the product temperature is not easily controllable, the output product tends to gradually become too cold, which has the effect of hardening the product and risking the machine blocking, conversely if the modules are too hot it is difficult to obtain the desired temperature.

[0014] The present invention is concerned with improving the structure and performance of injectors or injection wands allowing, as described above, the injection of a cryogenic fluid directly into the extruded product.

[0015] It can be noted that current rods are made of a simple stainless steel tube.

[0016] Inside an extruder, a food product is cooked at high temperatures (80 to 180 °C) and high pressures (often around 20 bar). When the pressure in the extruder tube exceeds the pressure in the extruder, some of the product can enter the injection orifice and travel far up the piping. The high temperatures promote the drying of the product in the tube and the formation of a blockage. This blockage can only be removed by dismantling the tube. This operation requires a complete shutdown of the process, which is very disruptive.

[0017] Furthermore, it is sometimes necessary to stop the gas flow for product quality reasons. In this situation, the operator risks creating a blockage in the nozzle and subsequently disrupting the injection process. Today, all gas flow control elements are located at the nozzle end, upstream of the nozzle's attachment point on the extruder.

[0018] As will become clear from what follows, the present invention proposes a new structure for the injection rod of the cryogenic fluid into the product to be extruded circulating inside an extrusion screw, characterized by the presence of the following elements, which can be better understood and visualized in connection with the attached [Fig. 1]: - 1: injection cane - 2: Non-return valve in the injection lance, positioned as close as possible from the injection point, typically a few centimeters, or even a few millimeters (less than 1 cm). If product is present in the tube, the valve prevents it from flowing further up the system. - 3: A spring-loaded valve (calibrated). The valve only opens when the pressure at the injection point in the extruder is less than a given setpoint, for example, 1 bar below the pressure in the tube. - 4: A hollow ring at the end of the rod that allows opening and closing the flap without exceeding the length of currently known rods. - 5: according to an advantageous option, the presence of a porous element or a grid at the end of the cane, in order to break the flow of gas and promote the formation of small bubbles.

[0019] A rod typically has a diameter of a few millimeters, generally between 6 and 20 mm. The length of the rod can, of course, vary depending on the extruder model, but it can be considered that this length is generally between 10 and 30 cm. The rod is preferably made of stainless steel.

[0020] The invention then relates to an injection lance for a cryogenic fluid in a food product circulating in an installation for shaping this product by cryoextrusion, the lance comprising the following elements: - A non-return valve, positioned upstream of the point of injection of the fluid into the extrusion screw or into the product, as close as possible to this point of injection, typically a few centimeters, or even a few millimeters from the point of injection (less than one cm), suitable in case of presence of product in the tube, to prevent this product from going further upstream of the tube; - A spring-loaded valve, calibrated, the valve being thus able to open only when the pressure at the injection point in the extruder is less than a given setpoint, for example 1 bar below the pressure in the tube; - A hollow ring, located downstream of the valve, at the end of the rod, which allows the opening and closing of the valve; - According to an advantageous option, the presence of a porous element or a grid at the end of the rod, attached to the ring, in order to break the flow of gas and in particular to promote the formation of small bubbles.

Claims

[Claim 1] Demands A nozzle (1) for injecting a cryogenic fluid into a food product circulating in an installation for shaping that product by cryoextrusion, nozzle comprising the following elements: - A non-return valve (2), positioned upstream of the point of injection of the fluid into the product, suitable in case of presence of product in the tube, to prevent this product from going further upstream of the tube; - A valve (3) equipped with a spring, calibrated, the valve being thus able to open only when the pressure at the point of injection into the product is less than a given setpoint, for example 1 bar below the pressure in the can; - A hollow ring (4), located downstream of the valve, at the end of the rod, which allows the opening and closing of the valve; - And including, where appropriate, a porous element or a grid (5), at the end of the rod, attached to the ring, capable of breaking the flow of gas and promoting the formation of small gas bubbles.

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