APPARATUS AND PROCESS FOR THE PRODUCTION OF SOYBEANMILK

Field of the invention The present invention refers to the production of the soybean derivative commonly designated as "soybean milk", and refers more specifically to an apparatus and a method for that purpose using soybean flour as raw material.

Description of the prior art

Soybean, which has been known in Asia for centuries and was introduced in Brazil after the middle of the 20 ^th century, is currently an important agricultural product, and is widely used as a source of oil, bran for animal nutrition, flour for human nutrition, as well as of other products of therapeutic value such as isoflavones. One of the most benefical among these byproducts is the soybean milk, initially used in the composition of school meals, but nowadays increasingly commercialized in supermarkets and related establishments due to its nutritional qualities.

A number of techniques are already known for the production of soybean milk, the majority thereof based on grinding the beans in an aqueous medium. Patent No. US 4971825 describes a process wherein the soybeans are ground in heated water, resulting in fragments of a size not exceeding 0.1 mm. This material in aqueous suspension is subjected to temperatures in the order of 95° C to deactivate the lipoxygenase and the trypsin inhibitor, followed by a second step of fine grinding and separation in

a 200-mesh sieve, yielding 10 kg of soybean milk for a consumption of raw material - soybeans - of 2.5 kg. As may be noted, the yield of the process is quite small, rendering the product expensive and not quite appropriate for programs of social interest such as school lunch applications.

Although the above cited document does not provide details regarding the possible alterations of the soybean milk during storage, it has been noticed in a great number of cases that the soybean milk available in commercial establishments should be shaken prior to consumption, due to the occurrence of a noticeable settling of the solids after a period of a few hours or days. Obviously, the need of such skaking annoys the consumer, especially when the package has been already opened and remains partially full.

Objects of the invention In view of the above, the main object of the present invention consists in the provision of a technique for the production of soybean milk that may afford high yield, rendering the product accessible to all segments of society.

A further object consists in producing soybean milk that is not liable to the settling of solids, even when stored for long periods of time.

One additional object is to deactivate the substances which give rise to the characteristic odor such as lipoxygenase, when the same is present in the raw material used.

One further object is to deactivate the trypsin inhibitor should the same be present in the raw material used.

Yet another object consists in producing soybean milk of high quality and low cost using soybean flour as raw material.

Summary of the invention

The above and other objects are achieved by the invention by means of an apparatus comprising three processing tanks, the first one provided with means for heating and mixing the soybean powder with water, the second provided with means for the separation of the soybean milk from the solid residue, and the third provided with means for cooling the soybean milk and blending flavoring agents therewith.

According to another feature of the invention, said cooling means are provided by a bain-marie type arrangement comprising a first external tank, within which is arranged said first internal tank containing the water and the soybean flour, the space between said external and internal tanks being filled with a liquid that is kept heated by means of a coiled heating pipe.

According to another feature of the invention, said liquid is oil.

According to a further feature of the invention, the mixing means in said first tank are provided by a recirculation pump.

According to another feature of the invention, the separation means comprise a high-pressure spouting device and a fine-mesh retention screen.

According to yet another feature of the invention, the third tank cooling means are provided in the form of an arrangement comprising an external tank containing cold water, within which is arranged said third tank.

According to another feature of the invention, said blending means comprise a second recirculation pump to recirculate the content of said third tank.

According to another aspect of the invention, the process for the preparation of the soybean milk comprises the steps of: - provision of a first thermal shock by the addition of the soybean powder at room temperature to the heated water; mixing of the soybean powder with the water forming a "pap" or slurry, and keeping the latter heated for a period of time sufficient to deactivate the lipoxygenase and the trypsin inhibitor; - separation of the soybean milk from the solid residue; pasteurization of the soybean milk; addition of aromatizing or flavoring substances to the soybean milk.

According to another aspect of the process of the invention, in said first thermal shock the heated water is kept at a temperature between 80°

C and 95° C, preferably between 88° C and 92° C.

According to another aspect of the process of the invention, the mixture of soybean powder with the heated water to form the slurry is provided by the recirculation of the liquid provided by pumping.

According to another aspect of the process of the invention, said recirculation operation lasts from 10 to 40 minutes, preferably from 20 to 30 minutes.

According to another aspect of the process of the invention, said separation is provided by straining the slurry by high-speed impact against a filtration screen.

According to another aspect of the process of the invention, said screen has a mesh size comprised between 50-mesh and 250-mesh per inch.

According to another aspect of the process of the invention, said impact is provided by forcibly spouting of the slurry under high pressure through a plurality of holes of a spraying device.

According to yet another aspect of the process of the invention, said pasteurization is provided by a thermal shock resulting from an abrupt reduction of the temperature of the soybean milk.

Description of the figures

The additional features, advantages and characteristics of the invention will be more easily understood from the subsequent description of a preferred exemplary embodiment, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic illustration of the proposed apparatus.

Figure 2 illustrates the process of the invention by means of a flow diagram.

Detailed description of the invention

Referring now to Fig. 1, the proposed apparatus comprises three processing tanks 10, 20 and 30 provided in sequence and interconnected by piping and pumps. Tank 10 comprises a bain-marie arrangement, consisting of a first internal container 13 surrounded by a first jacket 11 concentric therewith, with the space between said container and said jacket being filled with a liquid 14 that is heated by means of the serpentine heating pipe coil 12. In a preferred embodiment, such liquid is oil, which is kept at a temperature between 80° C and 95° C, preferably between 88° C and 92° C, and most preferably at 90° C. To avoid the ingress of dust and microorganisms that might contaminate the product, said tank is provided with a cover 16, which may be opened when needed. According to the present exemplary embodiment, this cover is provided with a loading port 42 that is also provided with a cover, through which the soybean powder 43 is added to the heated water 15 contained in said first internal container. Since the

soybean powder is at room temperature and the water is at about 90° C ₃ the former will undergo a thermal shock. After addition of the soybean powder (i.e. the soybean flour) the first pump 19 is operated, providing the recirculation of the contents of said container through the piping 18 and the open valve 17. This recirculation step, which may last between 10 and 40 minutes - preferably between 20 and 30 minutes - results in the complete mixing of the soybean powder in the water, forming a "pap" or slurry heated at about 90° C. Such temperature during the duration of the recirculation period causes the deactivation of the trypsin inhibitor, as well as of the lipoxygenase that may be present in the raw material.

At the end of said period, the first valve 17 is closed, and a second valve 21 is opened, so that the heated slurry flows through the piping 21' into the second tank 20, which is provided with a spouting device 23 located approximately at the center of its shell 22. This spouting device is surrounded by a peripheral substantially cylindrical "strainer" - which follows the contour of the wall of said second tank — comprising an inner screen 25 of extremely fine mesh size whose outer surface lies against a screen 24 of a mechanically strong material acting as a support means of said inner screen. Both screens are formed of chemically inert materials, the inner screen - having a mesh size comprised between 50-mesh and 250-mesh - being made of a synthetic resin such as nylon or an equivalent material and the outer screen being made of stainless steel. According to the invention, the slurry is pumped at high pressure and upon being spouted from the plurality holes of the device 23, is impelled at high speed against said inner screen. The resulting impact provides the homogenization of the soybean milk consisting

in the thorough dispersion of the soybean powder into the water, forming a suspension that may be stored for long periods without occurrence of settling. Concurrently with said homogenization, the soybean milk passes through said strainer due to the impact force and is collected on the inner walls of said second tank, flowing towards the bottom thereof, wherefrom it passes through the third valve 29 into the third tank 30 under the pumping action of the pump 36, while the fourth valve 35 is open and the fifth valve 37 is closed. The solid portion of said slurry, i.e. that which was not dispersed into the soybean milk, is retained by the screen 25 and forms a "cake" with low moisture content, that is periodically withdrawn and dried, being used for the preparation of TSP (Textured Soybean Protein), kinako, and bakery or confectionery products, pasta/spaghetti or dietary supplements.

The third tank 30 comprises a third container 32 located within a large-sized tank 31, that is filled with a liquid refrigerant 33, preferably water. This tank 31 is provided with a first serpentine pipe coil 41 for cooling and freezing the water, forming an "ice bank", with temperature control such that the inner walls of said container 32 are kept at a temperature comprised between 1° C and 5° C. According to the invention, there is provided a spouting device 46 within said third container, fed by the second pump 36 through the valve 35. A second serpentine pipe coil 34 encircles the outer wall of said third container, and its purpose is to insure that the temperature thereof remains within the specified limits during the step of pasteurization of the soybean milk as described below.

Said pasteurization results from the fact that the soybean milk

from the tank 20 is at a temperature above 70° C ₅ since the passage of the product by said tank is brief and this tank is not provided with any cooling means. Thus, the heated soybean milk is projected by the spouting device 46 against the cold walls of the container 32, and is thereby subjected to a second thermal shock — i.e. an almost instantaneous cooling - which results in the pasteurization of the product.

After the tank 30 has been filled to its full capacity, the third valve 29 is closed, and various ingredient are added to the soybean milk, such as flavorizers — substances that impart a specific taste - dyes (if applicable) and/or sweeteners (sugar, synthetic sweeteners, etc.). In a preferred embodiment, this addition is performed by means of the loading port 45 provided for this purpose, located on the cover 44 of said container. This port is provided with a cover, which is opened for admission of the cited ingredients, and upon the closing thereof, a guillotine at its bottom (not shown in the drawing) is opened, allowing these substances to fall onto the soybean milk, the blending of the mixture resulting from the recirculation provided by the pump 36, with the fourth valve 35 and the fifth valve 37 open, and the valves 29 and 39 closed. Once the mixing is completed, the fourth valve 35 is closed, the sixth valve 39 is opened, and the finished product leaves through the piping 40 towards the packaging equipment which uses known processes.

According to a preferred embodiment of the invention, the tank 31 is large enough to accommodate two reservoirs 32 when an increase in the processing capacity of the apparatus is desired.

A compact depiction of the soybean milk production process is

depicted in the form of a succession of steps in the flow diagram of Fig. 2, corresponding to the sequence already described.

From the preceding description, it may be understood that the production of the soybean milk is performed by batches. However, the apparatus allows a semi-continuous operation, since that, upon completing the high-pressure pumping from tank 10 to tank 20, the second valve 21 may be closed and the container 13 may be filled with water that will be heated to initiate a new cycle of formation of the slurry, simultaneously with the processing in tank 30 of said mixture of the ingredients with the soybean milk.

The yield of the illustrated process is greater than that of known processes, exceeding 10 liters of soybean milk per kilogram of raw material, and may even reach 15 liters per kilogram of soybean flour, depending on the fineness thereof. Furthermore, the process allows the use of soybean flour containing lipoxygenase, since the heating intended to deactivate the trypsin inhibitor also deactivates the lipoxygenase that may be present in the raw material.

While the present invention has been described with respect to what is believed to be the most practical embodiment thereof, it is particularly noted that this is by way of example only, and appropriate modifications and variations thereof are possible within the spirit and scope of the invention. Thus, for example, an additional pasteurization step performed by specific equipment may be added, without overstepping the present inventive concept.

Furthermore, the slurry originating from tank 10 may be projected against the screens that form the sieve in tank 20 by means other than the spouting device 23, such as, for example, a set of blades rotating at high speed, with a resulting impact effect that would be similar to the one described hereinabove.

Therefore, the invention is to be described and limited only by the scope of the appended claims.