METHOD FOR THE PREPARATION OF A ROASTED NUT-LIKE PRODUCT

Abstract: There is provided a method for preparing a roasted nut-­ like product from soy beans. Raw soy beans are deskinned and split in bean halves which are soaked at temperatures of 20-100°C for swelling. After being dewatered, the bean halves are subjected to fast drying and mildly roasting in hot air at temperatures of 160-350°C. During the fast drying the bean halves are first subjected to a high temperature for fixing their outer skin to a high temperature, whereafter post-drying is performed at lower temperatures for removing the interior moisture.

Description: The invention relates to a method of preparing soy beans for consumption in which raw soy beans are deskinned and split, the deskinned bean halves are soaked in water at temperatures of 20-100°C and the soaked bean halves are dried at elevated temperatures. As is known, soy beans are rich in precious proteins and fats, suitable as nutrients. Therefore there is a continuous search for possibilities to make soy beans suitable for consumption. Methods for preparing soy beans for consumption as defined in the preamble, are already known. As disclosed in GB-A-460,811 for obtaining a consumption product the bean halves are soaked in water at a temperature of about 100°F (38°C) to moisture content of 20 %. Thereafter the soaked beans are exposed to a particular drying treatment in which the beans are first subjected to a temperature of approximately 325°F (163°C) during a short period of time, whereafter the beans are further dried at temperatures below 100°C. The short treatment at a temperature of 325°F is meant to remove disagreeable flavours and odors, said treatment should be so short that no discoloring will appear and the beans will still be wet before further drying at lower temperatures. By such method there is obtained an eatable product, however, not a crisp nut-like product. To obtain a nut-like product the beans or bean halves should be soaked thus, that they will swell considerably so that an expanded structure is obtained, whereafter the moisture in the expanded structure should be removed. Methods for preparing nut-like products of soy beans are already disclosed, see for instance US patents 1,774,110 (Sloat); 3,594,185 and 3,594,184 (Hawley). A nut-like product that may be used as substitute for nuts such as peanuts, should comply with specific requirements with respect to taste, appearance and brittleness (crispness). This has not fully been achieved hitherto; the unpleasant soy taste has not completely disappeared and the "soy nut" is too small and too hard. It is therefore the object of the present invention to provide a method with which "soy nuts" can be produced from raw soy beans, which do not possess the defects mentioned above, and comply with a high standard for both taste, appearance as well as crispness. To that purpose the invention provides a method as described in the preamble, characterized in that for obtaining a crisp, nutlike product the bean halves are soaked at temperatures of 60-100°C, and that the soaked swollen bean halves, after having been drained, are dried fast and are mildly roasted in hot air at temperatures in the region of 160-350°C, during which process the bean halves are first exposed to a high temperature of at least 250°C for fixing of their outer layer and subsequently post-dried at lower temperatures for removal of interior moisture. The invention is based on the insight acquired, that for obtaining a desired brittleness for the final product, care should be taken, that the soy bean halves will swell sufficiently during soaking, and that this expansion is not undone during drying and roasting. According to the inventionthe bean halves are preferably blanched at a temperature of 60-85°C and subsequently soaked and/or boiled at a temperature of 60-100°C. Thereby the bean halves will swell up to the two-threefold of their volume, while the beans retain a proper light yellow colour, while moreover the characteristic soy taste is removed, and enzymes such as lipoxygenase, unrease and the trypsine inhibitor are deactivated, which improves taste, keeping qualities and nutrition value of the final product significantly. It is usually to be expected, that the expanded bean halves will shrink again on drying and roasting, which would imply a final product with little brittleness. By after dewatering fast drying the soaked bean halves at a high temperature of at least 250°C in hot air, a fixation of the surface layer of the bean half is achieved by the fast drying thereof. After this fixation drying is continued at a lower temperature in order to remove the interior moisture. Thus no substantial shrinking of the bean will occur on account of the stiffness of the surface layer. Because during soaking it is seen to that the water is homogeneously distributed in the bean halves, the latter acquire a balanced porous structure, after removal of the interior moisture during drying, providing the desired crispness to the final product. In the invention drying and roasting can be accomplished effectively by subsequently passing the dewatered bean halves through a first drying area with an inlet temperature of about 250°C and an outlet temperture of about 90°C, a second drying area with an inlet temperature of about 220°C and an outlet temperature of about 115°C, and a third drying area with an inlet temperature of about 160°C and an outlet temperature of about 100°C. The residence time in any of these drying areas may be effectively about 8-12 minutes. The method according to the invention is excellently suitable for a completely automated total process, wherein the inlet product is raw soy beans, and the final product crisp soy nuts, whole or more or less comminuted. Such an automated process may be obtained by making use for blanching of a blancher, provided with a conveyor screw, whereon an elongated boiling tube is connected, while for drying and roasting use is made of one or more drying areas, each consisting of a fluid conveyor bed, wherein hot air is blown from down upwards, and a pressure gradient sees to further conveyance. Such a process is very economical and provides an excellent final product. This final product, the soy nut, has a pleasant light yellow appearance, has a brittle crispness, and does not have a disturbing taste. The nuts thus obtained may be flavoured with flavouring agents known as such, so that a product is obtained comparable in use with the various existing types of nuts. It is also possible to process the product as a whole or in comminuted condition in many foodstuffs, for example in muesli, as fancy cake framing, and many other applications, which will be obvious after the above. The invention will be further elucidated in the following by an example. EXAMPLE Deskinned soy bean halves with a moisture content of 10-13 %, a bulk density of 750-800 kg/m³, a specific mass of 1200 kg/km³, and a weight of 1000 granules of 75 g are added to water of 70-85°C, and soaked for 10-15 minutes until an average moisture content of 40-50 % was obtained. Subsequently the mass was soaked for 15-20 minutes at 85-100°C, whereby a moisture content of 50-65 % was achieved. During this treatment the soy beans swelled to over twice their size, and it appeared from investigations that the bitter-making taste had disappeared. Subsequently the moist soy bean halves were dewatered on a sieve, whereupon they had a bulk density of 650-700 kg/m³. The dewatered bean halves were subsequently dried fast and intensively with dry air with a dew point between 30-90°C by passing them over three drying beds, wherein hot air was blown. The inlet temperatures of the three drying beds were 250°C, 220°C and 160°C respectively. The passing speed was adjusted in such a way, that the average residence time per drying bed was 10-12 minutes. At the outlet of the last drying bed a nut-like final product is obtained, taht had retained the greater part of its expansion, and that had a moisture content of between 1-4 %, a bulk density of 350-450 kg/m³ and an apparent specific mass of 600-800 kg/m³. This product had an attractive light yellow appearance, was crisp, and had a neutral taste, which makes it eminently suitable for application as semi-manufactured article of many foodstuffs.

Claims: A method of preparing soy beans for consumption in which raw soy beans are deskinned and split, the deskinned bean halves are soaked in water at temperatures of 20-100°C and the soaked bean halves are dried at elevated temperatures, characterized in that for obtaining a crisp, nutlike product the bean halves are soaked at temperatures of 60-100°C, and that the soaked swollen bean halves, after having been drained, are dried fast and are mildly roasted in hot air at temperatures in the region of 160-350°C, during which process the bean halves are first exposed to a high temperature of at least 250°C for fixing of their outer layer and subsequently post-dried at lower temperatures for removal of interior moisture. A method according to claim 1, characterized in that the bean halves are first blanched at a temperature of 60-85°C and subsequently soaked and/or boiled at a temperature of 85-100°C. A method according to claim 1 of 2, characterized in that the bean halves are soaked to a moisture content of 50-65 %. A method according to one of the preceding claims, characterized in that drying and roasting is performed by subsequently passing the dewatered bean halves through a first drying area with an inlet temperature of about 250°C and an outlet temperature of about 90°C, a second drying area with an inlet temperature of about 220°C and an outlet temperature of about 115°C and a third drying area with an inlet temperature of about 160°C and an outlet temperature of about 100°C. A method according to claim 4, characterized in that the residence time in any of these drying areas is about 10-12 minutes. Nutriment product in which the soy beans product prepared according to the method of one of the preceding claims, has been worked up in whole or comminuted condition.

Inventors: VAN DER MAREL, FRANS
Applicants: SOLNUTS B.V.
Application year: 1988
Main classification: A23L1
IPC codes: A23L1