MACHINE FOR DRYING PASTE FOOD PRODUCTS OR THE LIKE

Abstract: The machine comprises a pre-heater (1) followed by a first chamber (3), incorporating heated plates (4) wherebetween a food product to be dried is passed. The machine also comprises a successive section (6), wherethrough the food product is conveyed to a second chamber (7), incorporating cooled plates (8), where­ between the food product is passed. The plates (8) are adapted for rapidly condensing moisture contained in the ambient air and in the food product itself, to further rapidly reduce its moisture content to approximately 13-14%.

Description: This invention relates to a machine for drying paste food products or the like. It is known that paste food products is dried, for long-term preservation, to a moisture content as low as 12% to 13%. On completion of the processing cycle, prior to drying, paste food products with a high moisture content (15-35%) behave like a plastic material within which capillarly grids form which spread moisture throughout the product, enabling it to migrate from the middle toward the periphery as the outer surface is being subjected to evaporation. For a smooth drying process, it is mandatory that such capillaries be left open, and the product quality rating requires that associated volume shrinkage upon drying creates no stresses within the product. These stresses, in fact, if retained on completion of the drying process originate a consequent phenomenon of micro-cracks being formed in the product, which is a cause of the product fragility. In practice, a microcracked product is easily crumbled during the storage, packaging, and cooking steps. Such a product type has a low commercial quality rating. From FR-A-1 457 877, in the name of the same applicant, is known a machine for drying pasta according to the pre-characterizing portion of Claim 1. It is an aim of this invention to provide a machine which affords optimum drying of paste food products or the like. Within the above aim, it is an object of the invention to provide a machine which affords a high-temperature drying process yielding a product which is not microcracked and, accordingly, sufficiently strong to resist crumbling during the storage, packaging and cooking steps. A further object is to provide a machine which affords a good quality product and a reduction of processing waste. Another object is to provide a machine which affords an improved process with savings both in time and machine wear. These objects are achieved by a machine for drying paste food products or the like food products according to the appended Claim 1. Figure 1 shows diagrammatically a machine according to the invention; Figure 2 is a fragmentary cut-away perspective view of a heating or cooling chamber of the machine; Figure 3 is a partly sectional perspective detail view of a heating or cooling plate incorporated in the chamber of figure 2; and Figure 4 is a cut-away perspective view of a conveyor for transporting paste food product or the like food from a first heating chamber to a second cooling chamber in the machine for drying paste food product according to the invention. With reference to the cited drawing figures, the machine for drying paste food product or the like food products according to the invention comprises a conventional pre-drier 1, wherein cams or rods from which the paste food product, e.g. spaghetti, is suspended, follow a path 2 in a hot, damp climate which can be conditioned as desired. Along this path, by virtue of air convection and change, the paste food product is heated and loses moisture until its moisture content is reduced to between 16% to 18%. The pre-drier 1 temperature is substantially in the order of 85° to 90°C and the residence time is approximately 30 to 60 minutes, though obviously these conditions may be varied according to contingent requirements, for example it may be convenient to increase the temperature and decrease the residence time or vice versa. Of course, it will be appreciated that whilst, by way of example, reference is made to spaghetti, the machine according to the invention may be used for processing any types of paste food product, or similar food product, by the mere adoption of different and adapted elements, already known in the art and unrelated to this invention. On completion of the first pre-drying step, the paste food product is fed into a first substantially vertical labyrinth chamber 3 wherein plates indicated by the reference numeral 4a in figure 1, are adapted for maintaining a high temperature and high humidity environment. More precisely, and with reference to drawing figure 2, the paste food product is transported from the pre-drier 1 to the first chamber 3 by a conveyor mechanism, advantageously comprising a pair of chains 14 having rods 16 extending therebetween for supporting the paste food product, generally indicated by the reference numeral 17. The chain runs may be composed of a series of closed loop chains, as shown schematically in Figure 1, or may alternatively comprise just two continuous closed loops. The chains are expediently guided by means of sprocket wheels 15, rotatably mounted on the chamber walls. One or more of the sprocket wheels, corresponding in number to the number of closed loop chain runs, may be driven by a convenient power source such as an electric motor unit and appropriate transmission means. The first chamber 3 comprises an outer wall 11, covered by a panel or layer of thermal insulating material 12, and a pair of plates 4 extending laterally across the chamber 3. As illustrated in figure 3, the plates 4 advantageously comprise a series of tubular elements or tubes 20, interposed by plates 21, and being closed by a head member 22, such that fluid such as water may be caused to flow through the tubes 20. In the case of the first chamber 3, hot fluid is caused to flow through the tubes 20 to heat the plates 4, (indicated at 4a in figure 1), wherebetween the chains 14, and rods 16 extending therebetween for carrying paste food product 17, are guided by means of sprocket wheels 15. Obviously, the layout of tubes 20 and the configuration of the head 22 may be selected to obtain any desired flow pattern according to contingent requirements, and any suitable fluid heating means may be used. Moving along the path defined by the chain 14 runs, as schematically illustrated in figure 1 and indicated by the reference numeral 5, inside said first substantially vertical chamber 3, the paste food product loses no appreciable amounts of moisture, while there occurs homogenization of both temperature and degree of moisture throughout the paste food product mass. Downstream of this second path 5, the paste food product is next conveyed via a variable length horizontal connection 6, illustrated in figure 4, to a second substantially vertical labyrinth chamber 7 wherein further plates 4b (figure 1), also consisting of flat plates or smooth or finned pipes, are maintained at a low temperature. The structure of the second chamber 7, is exactly the same as the structure of the first chamber 3, as illusstrated in figure 2, however, in the second chamber, the tubes 20 of the plates 4 are utilized for conducting a cold fluid, which may be for example, water maintained at a suitably low temperature by a refrigeration unit. Thus, the surfaces of the plates 4 are adapted to rapidly condensate intensive amounts of moisture contained in the ambient air and the paste food product itself. By virtue of the cited structural arrangement, the paste food product undergoes in this labyrinth chamber 7, a very sudden and sharp drop in moisture content and temperature but without this being accompanied by any detrimental changes in capillarity characteristics and without the generation of stresses or microcracks in the paste food product structure. At the end of this treatment and upon leaving the second chamber 7, the moisture content of the paste food product may be conveniently close to 13-14%, thereby it becomes possible to convey the paste food product to a final drying station comprising a conventional type of drier. It will be appreciated that an improvement in the machine consists, according to one aspect of the invention, of interposing a hot labyrinth chamber between a pre-drier and a cold labyrinth chamber, adapted for suitably lowering the temperature and moisture content of the heated paste food product to selected levels for introduction into the end drier. In order to provide a flow of fluid through the tubes 20, pump means may be provided, or alternatively, fluid may be gravity fed from a suitable header tank. Furthermore, the system may be completely sealed and even pressurized, depending upon operating temperature requirements, production rate, etc.. From actual tests carried out it has been found that the rapid removal of moisture and sudden drop in temperature prevent alteration of the internal grid and the structure of the paste food product, and above all, that the paste food product is neither microcracked nor fragile at the end of the process. The improvements made to the machine are especially simple, being substantially composed of interposing a further labyrinth chamber where the hot plates, already known, have been merely replaced with plates or systems adapted to be maintained at a low temperature. Construction-wise, the improvements are neither complicated nor expensive, while the benefits of product quality are considerable and significant. In fact, the machine according to the invention permits the obtainment of a finished product which is strong, with inherently low waste in the storage and packaging operations, and which is of excellent quality. Of course, the machine herein may be embodied in several different ways while observing the same concept of interposing, in the drying process, a step involving a sharp reduction in temperature and humidity within a short time lapse by passing the paste food product between cold plates, without making recourse to artificially induced convection.

Claims: A machine for drying paste food products or the like comprising a preliminary drying section (1) extending substantially horizontally, followed by a first labyrinth section (3) having substantially vertical heating plates (4a) adapted to heat the paste food products to thereby diffuse and homogenize its internal moisture content, and by a final drying section extending substantially horizontally, characterized in that between said first labyrinth section (3) and said final drying section there is interposed at least a first horizontal connecting section (6) and a second labyrinth section (7) having substantially vertical cooling plates (4b) in which a cooling fluid flows at such low temperature to cause intensive condensation of both the ambient moisture and the moisture content of the paste food products to thereby concurrently provide a sharp drop in the paste food products temperature. A machine according to Claim 1, characterized in that said cooling plates (4b) comprise a plurality of tubular elements (20) connected by head connecting nests (22) through which the cooling fluid flows. A machine according to any preceding claim, characterized in that said cooling fluid is passed through an external refrigeration unit adapted to maintain said cooling plates at such temperature to cause sudden and intensive condensation of moisture in said second labyrinth chamber (7). A machine according to any preceding claims, characterized in that the temperature of the cooling plates is so selected to cause reduction of pasta moisture content to 13-14%.

Inventors: PAVAN, MARIO
Applicants: PAVAN MAPIMPIANTI S.P.A.
Application year: 1986
Main classification: F26B3
IPC codes: F26B3, A23L3, F26B15, A23L1