Drying and gas or vapor contact with solids – Process – With nondrying treating of material
Patent
1993-08-23
1995-12-12
Gromada, Denise L.
Drying and gas or vapor contact with solids
Process
With nondrying treating of material
34438, 34493, 34218, 426456, F26B 700
Patent
active
054738253
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for continuously drying and stabilizing pasta and like, and an apparatus for implementing the process.
Production processes for pasta generally comprise a final drying stage in which the water content of the pasta is reduced to an average of 10-13% by weinght, to ensure a long product shelf life. This drying stage does not result in uniform drying throughout the entire pasta mass, but involves water evaporation from its outer surface and migration of further water from the pasta interior to the surface layers, to recreate the equilibration which the surface evaporation alters.
This drying is sometimes done slowly so as not to create mechanical stresses within the pasta which could result in product damage during its subsequent packaging, storage, transportation and cooking, but in this case the drying time is excessively long and the plant is very large, with high operating costs.
The pasta drying can also be done at a high rate, but alternating the drying stages with stabilization stages, in which the pasta, the surface of which has dried to an extent greater than that desidered, is subjected to a surface remoisturizing stage which restores the plasticity lost during the preceding rapid drying stage.
In Italian Application Nr. 41583 A/86 the pasta is remoisturized after an intense drying stage, by spraying water into a part of the drier. However with this method there is the danger of wetting the product to be treated.
It is also known to remoisturize the pasta after an intense drying stage, by injecting steam. This method requires a steam generator, the cost of which is added to the plant cost, and also involves an energy cost in its operation.
It also carries the danger of introduction of chlorine compounds into the drier because of possible imperfect operation of the water treatment plant used for generating the steam. This can result in rapid corrosion of the stainless steel used in the drier construction.
Finally, the steam produces a temperature increase in the pasta, whereas in this stage a temperature reduction would be desiderable to avoid an excessive heat load for the final cooler and a corresponding increase in energy costs.
In addition to these drawbacks of known pasta stabilization processes, it should be noted that generally a single drying and stabilization cycle is insufficient, but instead several cycles are required in which the pasta is subjected to alternations of only a limited extent, in order as far as possible to liken the forced drying process to the natural tendency of the pasta to continuously vary its moisture content. Moreover, this alternation of drying and remoisturizing stages means that different climates must be provided, with obvious high installation and running costs.
DE-B-1.142.794 describes a tunnel dryer for long pasta goods with a conveyor tunnel subdivided into ventilated areas and not ventilated areas.
U.S. Pat. No. 2,790,250 relates to an automatic and continuous process for drying alimentary pasta goods in which the goods are continuously and alternatively conveyed through areas of circulating heated air and "dead" or not circulating air areas.
FR-A-2.562.647 describes a drying process for pasta comprising additional phases of ventilations, of resting and of cooling.
U.S. Pat. No. 2,732,627 relates to the drying of alimentary pasta comprising a drying chamber in which ventilated zones are alternatively followed by zones having still air therein.
According to the invention, a satisfactory continuous drying and stabilization of pasta and the like is achieved by a process as described in claim 1.
To implement the aforedescribed process the invention uses an apparatus as described in claim 5.
Some preferred embodiments of the present invention are described hereinafter with reference to the accompanying drawings in which:
FIG. 1 is a schematic section through a first embodiment of the apparatus according to the invention;
FIG. 2 shows the outline scheme of the circuit for air conditioning the environment in which an intense dryi
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patent: 5216949 (1993-06-01), Bertozzi
Conselvan Pier L.
Didone' Gastone
Gromada Denise L.
Pavan Mapimpianti S.p.A.
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