PROCESS AND APPARATUS FOR THE RAPID REHYDRATION OF LEGUMES AND THE LIKE

Abstract: The process consists of alternately subjecting the mass of loose product to be rehydrated to a treatment with a hot fluid, for an adjustable preset time interval, and with a cold fluid, for another preset time interval, and of alternately and successively repeating the treatment with hot fluid and with cold fluid until the preset rehydration percentage is attained. The apparatus includes an assembly (1) introducing the product into a tank (2) containing hot water and having a screw feeder (3) which feeds the product to a discharge collector (4). Transfer means (5), in the discharge collector, conveys the product to a cooling assembly.

Description: The present invention relates to a process and an apparatus for the rapid rehydration of legumes and the like. As is known, in the food-preserve industry, in order to rehydrate legumes and the like to be packaged, tanks are currently used, generally having considerable dimensions, in which the product to be rehydrated is immersed and has to remain in the water for a relatively long period of time, of the order of a few hours, so as to absorb the required amount of water. Considerable productive disadvantages are usually encountered with this procedure, since it is necessary to provide a high number of tanks in order to ensure production continuity. Moreover, the processing occurs discontinuously, since a large amount of product to be processed is accumulated at the end of the rehydration, followed by idle times which depend on the number of available tanks; the fact must furthermore be observed that it is necessary to set an organization of production which does not allow to vary the program, since once the product is rehydrated it must be packaged quite immediately; on the other hand, there is no possibility of programming a short rehydration, due to the high number of hours required to obtain rehydration. Trying to eliminate this disadvantage, machines have already been tested on the market which treat the product to be rehydrated with hot water, achieving, however, not fully satisfactory results in terms of the percentage of water absorbed by the dry product and in terms of the uniformity of the treatment, so that these machines have had no practical development. GB-A-2 137 070 discloses a process for the preparation and heat treatment of food products containing a preponderant fraction of constituting liquid which comprises an operation involving the mixing of an appropriate volume of constituting liquid with a concentrate containing the basic ingredients of the food product, and also a heat treatment operation intended for preserving the product. Specifically, when the constituents of the food product are initially in powder form, the process includes the steps of: converting the powder to a concentrate by adding a small amount of water, adding larger amounts of superheated reconstituting water to the concentrate to thereby obtain the reconstituted food product, subjecting the reconstituted food product to a heat treatment operation for preserving the product, and then cooling the product to a suitable temperature for packaging. The aim proposed by the invention is indeed to eliminate the above described disadvantages by providing an apparatus for the continuous rapid rehydration of dried products such as legumes and the like, which drastically reduces the times required for the desired rehydration, furthermore allowing a continuous flow of the rehydrated product. Within the scope of the above described aim, a particular object of the invention is to provide a rehydration apparatus and a rehydration process which, though executing the rehydration in extremely reduced times, assessable at approximately half an hour, create no appreciable variations in the organoleptic characteristics of the product. Still another object of the present invention is to provide an apparatus which makes the dry product absorb the desired percentage of water, without having to resort to modifications in the subsequent packaging treatments with respect to conventional methods. Not least object of the present invention is to provide an apparatus and a process which allow to pack the rehydrated legumes without requiring long programming times which currently entail the introduction of the dried products in the rehydration tanks at least the day before, so as to have them ready the following day for packaging. The above described aim, as well as the objects mentioned and others which will become apparent hereinafter, are achieved by a process and apparatus for the rapid rehydration of legumes and the like, as defined in the appended claims. Further characteristics and advantages of the invention will become apparent from the description of a preferred, but not exclusive, embodiment of an apparatus and of the related process for the rapid rehydration of legumes and the like, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a schematic view of the apparatus according to the invention; figure 2 is a schematic partial sectional view of an assembly of the apparatus for the execution of the step of treatment with hot fluid and with cold fluid; figure 3 is a schematic view of an apparatus for treatment with hot fluid constituted by steam. With reference to the above described figures, and in particular to figures 1 and 2, the apparatus comprises an assembly generally indicated by the reference numeral 1, which introduces the loose product to be rehydrated in a tank 2 containing water at a temperature above 80°C, preferably at a temperature of 95°C. Inside said tank 2 there acts advancement means constituted by a first advancement screw feeder 3 which transfers the product to an output collector 4, arranged at the other end of the tank 2, where the product is taken up by transfer means such as for example a delivery pump 5, or by another mechanical elevator device, introducing it into a dripping and cooling assembly 10 which is preferably arranged at a higher level or elevation with respect to the tank 2. The assembly 10 is provided with a first dripping region 11 where the hot water is separated from the product and reintroduced into the tank 2, thereby contributing to the prevention of energy waste. Inside the assembly 10 an advancement element 15 is provided, for example again constituted by a screw feeder, which conveys the product from the first region 11 to a second region 21 where the product is sprayed with cold water having a temperature substantially lower than 60°C, preferably at tap temperature. In the initial portion of the cooling section there acts an auxiliary pump, indicated by 25, which in practice recovers the cold water which has been heated by the hot product moving upstream with respect to the inflow of said cold water. At the end of said second region 21 the product has a temperature approximating or possibily lower than 40°C. At the output from the second region 21 of the assembly 10, the product is introduced into a third preheating region, indicated by 31, which is affected in countercurrent by the preheated fluid drawn by the auxiliary pump 25, so that the product is preheated before it is again discharged into a section of the apparatus which is substantially identical to the one previously described, that is to say a further tank 2 containing hot water. In practice, the product is thus subjected in a successive cyclic and alternating manner to steps of heating with hot water and to steps of cooling with cold or tepid water; the difference in temperature between the hot water and the cold or tepid water being preferably above 30°C. Such alternate cycles of heating and cooling are repeated for a number of times which is a direct function of the type of legumes and of the rehydration characteristics which it is desired to obtain; on the average 4÷6 times are sufficient. At the end of the apparatus a discharge assembly is provided where the product is dripped and sent to packaging, having undergone the required rehydration step. It must be furthermore added that the step of treatment with hot fluid, as is schematically indicated in figure 3, can be provided by means of an inlet assembly for steam at 50 to 100°C, at atmospheric pressure, which strikes the product with jets of steam heating it. The steps of heating the product to be rehydrated can also be performed with pressurized water or steam at temperatures above 100°C. In practical operation, a process is provided which consists of alternately subjecting the loose product to be rehydrated to a step of heating with hot fluid, having a temperature substantially higher than 80°, preferably a temperature around 95°C, for a preset period of time, generally of the order of a few minutes and subsequently to a step of cooling with cold or tepid fluid at a temperature below 60°, preferably water at tap temperature, in a time generally shorter than the heating step, and in alternately and successively repeating the treatment with hot fluid and with cold fluid until the preset rehydration percentage is attained. Moreover, another important aspect of the above described process resides in the fact that energy is recovered employing the hot fluids which are not dispersed, in fact the hot fluid which surrounds the product after the heating step is dripped off and returned to the heating tank assembly, and the cold fluid, heated by the product in the cooling step, is in turn recycled, so as to perform a preheating of the product before returning it to the tank or assembly where it undergoes the heating treatment. From the experimental tests performed it has been observed that for each kind of legumes it is possible to achieve, with an optimum number of alternated treatments, degrees of regeneration proximate to 100% in relatively short times, of the order of 30-40 minutes. Experimentally it has been observed and verified that the alternated treatments with hot water-cold water or steam-cold water allow a much faster rehydration than the conventional one by immersion of the product in a room-temperature tank, the rate of rehydration depending on the characteristics of the product to be rehydrated and on the temperatures selected in the two treatment steps. The high rehydration rate achieved is probably due to the fact that, by alternating heating steps and cooling steps, a pressure differential is created between the inside and the outside of the legumes which facilitates the absorption of water, in practice providing a "pump effect" which, by causing in a way the dilatation of the pores during the heating step, with their subsequent contraction in the cooling step, enormously facilitates the absorption of water inside the legumes. From the experimental tests performed, it has been observed that the rapidly rehydrated legumes are perfectly suitable for the production of packaged sterilized products, indeed in some cases, such as for example with so-called "borlotti" beans, or round beans, a marked improvement in color and sheen has been observed with respect to the conventional treatment. According to another aspect of the invention which is conceptually connected to the embodiment described above, the process can be carried out by subjecting the product, carried for example by a basket conveyor, to a steam spraying treatment applied downwardly and upwardly. The steam injection can be constituted by saturated steam at atmospheric pressure or slightly overpressured. Subsequently the product to be rehydrated is sprayed by water. These treatment steps are repeated for a number of times depending on the desired amount of rehydration. From what has been described it can thus be seen that the invention achieves the intended aims and in particular the fact is stressed that a process is provided which allows considerable energy savings, since the hot fluids employed are not directly dispersed outwards, but are used to perform the preheating of the product after the cooling step, and furthermore the product immersed in the hot fluid is dripped completely before the cooling step, consequently allowing the full energy recovery of the hot fluid. The invention thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept. Furthermore, all the details may be replaced with other technically equivalent elements. In practice, the materials employed, so long as compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements.

Claims: Process for the rapid rehydration of legumes and the like, comprising the steps of subjecting a mass of loose product to be rehydrated to a treatment with a hot fluid for a preset time interval, and then subjecting the product to a treatment with a cold fluid for another preset time interval, characterized in that it further comprises the step of alternately and successively repeating said treatments with hot fluid and cold fluid until the preset rehydration percentage is attained. Process, according to claim 1, characterized in that the difference between the temperature of said hot fluid and the temperature of said cold fluid is at least 30°C. Process, according to claim 1, characterized in that said hot fluid has a temperature substantially higher than 80°C. Process, according to claim 1, characterized in that said cold fluid has a temperature substantially lower than 60°C. Process, according to one or more of the preceding claims, characterized in that said hot fluid has a temperature of substantially 95°C. Process, according to one or more of the preceding claims, characterized in that said hot fluid is constituted by hot water at atmospheric pressure with a temperature comprised between 90°C and 100°C. Process, according to one or more of the preceding claims, characterized in that said hot fluid is constituted by steam at atmospheric pressure with a temperature of 100°C. Process, according to one or more of the preceding claims, characterized in that said hot fluid is constituted by pressurized water or steam at a temperature above 100°C. Process, according to one or more of the preceding claims, characterized in that said cold fluid is constituted by water at tap temperature or by cold or tepid recovery water. Process, according to one or more of the preceding claims, characterized in that it further comprises a step of dripping of said hot fluid from said product to be subjected to the treatment with said cold fluid, with recovery of said hot fluid. Process, according to one or more of the preceding claims, characterized in that it comprises the recovery of said cold fluid introduced in countercurrent onto the hot product to be rehydrated with subsequent introduction of the recovered heated fluid to execute the preheating of said product after the treatment with the cold fluid before the subsequent treatment with said hot fluid. Process for the rapid rehydration of legumes and the like, comprising the steps of spraying a mass of loose product to be rehydrated with a water flow rate for a preset time, and successively hitting the mass of moisted product with saturated vapour at atmospheric pressure or slightly overpressured, characterized in that it further comprises the step of repeating alternatively and in succession the cycle constituted by the steps of water spraying and vapour hitting until the desired rate of rehydration is achieved. Process, according to the preceding claim, characterized in that said sprayed water has a variable temperature depending on each of said cycle. Apparatus for the rapid and continuous rehydration of legumes and the like, comprising an assembly (1) for the introduction of the product to be rehydrated into a tank (2) containing hot water, in said tank (2) there being provided advancement means (3) for the advancement of the product towards a discharge collector (4), in said discharge collector (4) there acting transfer means (5) for the conveyance of the product to a cooling assembly (10), characterized in that it further comprises arranged downstream of said cooling assembly (10) at least one further tank (2) containing hot water and at least one further cooling assembly (10) arranged downstream of said further tank (2) in order to subject the product to at least another successive heating and cooling step to thereby significantly decrease the time of rehydration. Apparatus according to claim 14, characterized in that said cooling assembly (10) is provided with a first region (11) for the dripping of the hot fluid from the product, with a second region (21) for the spraying of the product with cold water, and with a third region (31) for the preheating of the product. Apparatus according to one or more of the preceding claims, characterized in that it comprises an auxiliary pump (25) which draws the cold fluid heated by said hot product and has its delivery leading into said product preheating region (31). Apparatus according to one or more of the preceding claims, characterized in that it comprises an assembly (50) for the steam treatment of the product to be rehydrated, followed by said cooling assembly (10). Apparatus according to one or more of the preceding claims, characterized in that it comprises a plurality of hot water tanks (2) and a plurality of cooling assemblies (10) arranged alternately to one another.

Inventors: ZANICHELLI, GIUSEPPE
Applicants: ZANICHELLI MECCANICA S.P.A.
Application year: 1987
Main classification: A23P1
IPC codes: A23B7, A23L1