Automatic and continuous rice cooking system

Abstract: An automatic and continuous rice cooking system comprises a horizontally arranged steam vessel (1) with an elongated steam jacket (2) having a semi-circular bottom housing a screw conveyer (3), and a steam tunnel passage (10) provided with a mesh conveyer (11) connected to the outlet port of the vessel at its terminal end via a duct (9).

Description: The present invention relates to an automatic and continuous rice cooking system. At caterers, hotels, and restaurants providing a large quantity of cooked rice at a time, or in businesses preparing secondary preservable products from cooked rice, a need for a system for cooking the rice continuously but without damaging the taste and the flavor is keenly felt. A prior art system for continuously cooking the rice is disclosed, for example, in JP-C-845 458. The system is structured to have a vertically inclined and elongated vessel in which a screw conveyer is provided. Water is retained at the bottom of said vessel, and by externally heating the water and by charging rinsed rice continuously inside the vessel at the bottom, the rice is cooked in the vessel at its bottom and then conveyed upward by means of the screw conveyer to be discharged from the vessel at the outlet provided at the upper end thereof. Such elongated vessel with a screw conveyer is advantageous in that the material rice is steamed and cooked in a continuous process when it is conveyed from one end to the other end of the vessel. However, because of the vessel being in an inclined position, it is a disadvantage of said device that during the so-called steaming process when the rice cooked at the bottom of the vessel is conveyed upward by means of the screw conveyer to the upper portion of the vessel where there is no cooking juice, the cooked rice is inevitably subjected to kneading by the screw conveyer and collects into a doughy lump like a rice cake. This makes it impossible to obtain cooked rice retaining discreate grain forms when discharged from the outlet at the upper end of the vessel. WO-A-83/00802 describes an automatic and continuous rice cooking system including an elongated steam vessel which is arranged horizontally. A conveyer belt transports the rice which is subjected to water and steam. The possibility of using only steam is also proposed. In this device, the rice is placed on the conveyer belt inside the steam tunnel and transferred by subjecting it to water and steam for steaming the rice on the conveyer belt. The rice is heated with steam as it sits stationary on the conveyer belt without being stirred. It is not possible to reach a uniform heating of the grains. The starch released from the rice grains remains adhered on the grain surface and does not become fully gelatinized, making it difficult for the gelatinized starch to be absorbed again by the rice grains. It is an object of the invention to provide for an automatic and continuous rice cooking system which solves the problems discussed above. The present invention was contrived to obviate such defects of the prior art system and is indicated in claim 1. The cooking vessel provided with a screw conveyer according to the present invention is arranged in a horizontal position, and the "steaming process" in which the starch is released from each grain by steaming the material rice, the "gelatinization process" in which the released starch is gelatinized, and a portion of the "adsorption process" in which gelatinized starch is once again adsorbed into the grains are all carried out in the vessel. The remaining portion of said "adsorption" process and the "fixing process" in which the gelatinized starch adsorbed in the grains is fixed to coat the surface of each grain are conducted after the rice is discharged from the vessel and transported into a net conveyer where hot water vapor is sprayed on the rice grains. As an additional means to carry out each of said processes, the present invention system may include a spiral rotary steam vessel comprising an elongated steam jacket with a semi-circular bottom which houses a screw conveyer with stirring vanes arranged in the axial direction and mounted on the shaft of the vessel, a passage forming a steam tunnel which is connected to the outlet of the vessel at its terminal end via a duct and which houses a net conveyer provided with plural nozzles for spraying water vapor both on the top and the bottom of the conveyer surfaces, a sump for cooking juice which is provided below said duct, and supply paths for supplying a portion of the cooking juice into the steam vessel at its mid portion and into the starting end of the conveyer in the steam tunnel. In the present invention system of the above construction, a predetermined amount of rice is sequentially charged into the steam vessel wherein a predetermined amount of water is pooled. While the charged rice is gradually steamed and conveyed toward the terminal end of the vessel by the screw conveyer, the steaming process in which the starch is released from the rice and the gelatination process in which the released starch is gelatinized are conducted. The adsorption process in which the gelatinized starch is adsorbed in the rice once again is conducted in the vessel near the outlet. The rice thus cooked is discharged onto the duct from the steam vessel outlet together with the cooking juice, dropped onto the starting end of the net conveyer housed in the conveyer passage in the form of a tunnel, and gradually conveyed toward the terminal end while being sprayed with hot water vapor both from the top and the bottom, during which time the remaining portion of said adsorption process and the fixing process in which the surface of the cooked rice gain is coated with the gelatinized starch are conducted. The cooking juice discharged from the vessel outlet together with the cooked rice is retained in the sump provided below the duct. A portion of the cooking juice in the sump is sprayed onto the rice being conveyed from the end of the conveyer inside the tunnel passage, supplying gelatinized starch contained in the cooking juice onto the grain surface. The remaining portion of the cooking juice in the sump is returned to the vessel at its mid portion where the gelatination process shifts into the adsorption process, supplementing the cooking juice containing the gelatinized starch to ensure a sufficient supply of gelatinized starch during the adsorption process. Other objects and advantages of this invention will become apparent when taken in conjunction with description herein below of an embodiment shown in the accompanying drawings. Fig. 1 is a plan view to show the construction of an automatic and continuous rice cooking system according to the present invention; Fig. 2 is a side view of the system shown in Fig. 1; Fig. 3 is a sectional view of the vessel shown in Fig. 1 along the line III-III; and, Fig. 4 is a sectional view of the tunnel passage shown in Fig. 1 along the line IV-IV to show the structure at its starting end. An embodiment of the present invention system will now be explained referring to the accompanying drawings. Fig. 1 is a plan view and Fig. 2 a side view. The system as a whole includes an elongated vessel 1 which is a horizontally positioned steam jacket and houses a screw conveyer 3, a steam tunnel passage 10 which is connected to the vessel 1 at its one end at the normal angle, and houses a horizontally positioned net conveyer 11. The vessel 1 comprises an elongated steam jacket 2 with a double wall which has a semi-circular bottom (Fig. 3), and a cover 24 provided at the top of the jacket 2 which can be opened/closed. Said jacket 2 is supplied via a pipe 23 with hot water vapor as the heat source. As shown in Figs. 1 and 2, an inlet port 4 for the material rice is provided above the starting end 1a of the vessel 1. A predetermined amount each of washed rice and water is continuously supplied into the vessel 1 from said inlet port 4. As the screw conveyer 3 transports the rice toward the terminal end 1b, the rice is sequentially heated and steamed by the hot water vapor supplied into the jacket 2. A pair of stirring vanes 7 parallel to a shaft 6 of said screw conveyer 3 is provided at the outer periphery of a spiral vane 5, whereby the rice grains and water are conveyed toward the terminal end 1b of the vessel while being mixed. The cooking process is conducted in the portion A1 which takes up one third of the length of the vessel from the starting end 1a to release the starch from the rice. Gelatilation of the starch released from the rice is conducted in the portion A2 which takes up one third of the length at the middle, and adsorption of the gelatinized starch by the rice takes place in the portion A3 in the final one third of the vessel length toward the terminal end 1b. Water charged into the steam vessel together with the rice at the inlet port 4 changes into the cooking juice containing the starch in the mid portion of the vessel 1 and a part of which is discharged out of the vessel into a duct 9 together with steamed rice gains which have not yet completely adsorbed the gelatinized starch. The rice discharged onto the duct 9 is further conveyed to the starting end 11a of a net conveyer 11 projecting from the steam tunnel passage 10 at the starting end 10a thereof. A laterally swinging comb 12 is provided at the bottom of the duct 9 so that the comb 12 reciprocating in lateral directions spreads uniformly onto the starting end 11a of the conveyer the steamed rice grains discharged from the outlet 8 of the vessel 1 into the duct 9. The conveyer 11 inside the steam tunnel passage 10 is a very fine mesh of stainless steel and conveys the steamed rice from the duct 9 toward the terminal end 10b of the passage 10. A pipe 13 each which is connected to a vapor source (not shown) and which supplies hot water vapor is provided above and below said conveyer 11 with respect to the conveyer surface of the cooked rice grains in the longitudinal direction. Each vapor supply pipe 13 is provided with spray nozzles 14 facing the conveyer 11 to spray the rice grains with hot vapor and to maintain high temperature and humidity inside the tunnel passage 10. In the meantime, a sump 15 for retaining the cooking juice discharged from the outlet 8 of the vessel together with the cooked rice gains is provided below said duct 9 and the conveyer's starting end 11a. The sump 15 is provided with a supply pipe 17 for supplying the cooking juice to a spray nozzle 18 provided above said conveyer's starting end 11a via a pump 16, and a supply pipe 19 for feeding the juice back into the vessel 1 at its mid portion. The cooked rice grains transferred from the duct 9 onto the conveyer 11. in the passage 10 are separated from the cooking juice when dropped onto the conveyer's starting end 11a. Thus, the starch adhered on the surface of the rice grains alone is adsorbed in the rice grains in the subsequent steps. However, as the cooking juice from the sump 15 is sprayed on the grain surface, extra supply of the gelatinized starch adheres on the grain surface. The cooked rice grains in this state are conveyed inside the tunnel passage 10, and a suitable amount of the gelatinized starch is adsorbed in the rice in the first half of the passage B1. In the latter half of the passage B2, an adequate fixing process is conducted to coat the rice grain surface with gelatinized starch. On the other hand, a portion of said cooking juice is returned from the sump 15 to the vessel 1 at its mid poriton via a supply pipe 19, thereby making up the lack of the cooking juice which had been discharged together with the cooked rice from the outlet 8 and ensuring adequate adsorption of gelatinized starch in the final section of the vessel. A second laterally swinging comb 20 similar to the first one is provided at the terminal end 11b of the conveyer in the tunnel passage 10. The rice grains cooked on the conveyer are tossed and loosened by the comb 20 and transferred into a receptacle 22 on a conveyer 21. The vessel 1 with a screw conveyer according to the present invention is positioned horizontally, and releasing of gelatinized starch from the rice by steaming and initial adsorption of the gelatinized starch is conducted in the vessel. The remaining portion of the adsorption and fixing process of the gelatinized starch are conducted while the cooked rice is being carried on the conveyer in the steam tunnel passage. Since the cooked rice which comes out of the outlet port of the vessel consists of discrete grains that have not yet completely adsorbed the cooking juice, the cooked rice in grains can be continuously transported out of the vessel by the screw conveyer with ease. The cooked rice discharged from the vessel is separated once from its cooking juice, and the cooking juice is pooled in the sump before being injected on the rice grains from the upper starting end of the conveyer in the passage to supplement the gelatinized starch. This enables adequate fixing of the gelatinized starch and enables continuous and efficient cooking of the rice.

Claims: An automatic and continuous rice cooking system including an elongated cooking vessel (1) housing a screw conveyer (3), characterized in that said vessel (1) is arranged horizontally, and that there is provided a horizontally arranged steam tunnel passage (10) housing a mesh conveyer (11) which is connected to an outlet port (8) of the vessel (1) at its terminal end. The rice cooking system according to claim 1, wherein said vessel (1) further comprises a double walled jacket (2) having a semi-circular bottom and a cover (24) that can be opened/closed at the top of the jacket, an inlet (4) for charging the material rice provided above the starting end of the vessel (1), and an outlet (8) for discharging the rice provided on the terminal end of the vessel (1); said screw conveyer is housed inside the vessel (1) along the semi-circular bottom substantially over the entire length of the vessel, and a pair of mixing vanes (7) are provided on the outer periphery of a spiral vane (5) in parallel with the shaft of the conveyer. The rice cooking system according to claim 1 or 2, wherein said steam tunnel passage (10) is connected to the outlet (8) of the vessel (1) at its terminal end via a duct (9) and houses a mesh conveyer (11), and wherein a sump (15) for receiving the cooking juice separated from the cooked rice is provided beneath the starting end of said mesh conveyer (11) which extends beneath said duct. The rice cooking system according to claim 1, wherein said steam tunnel passage (10) comprises: a conveyer (11) made of a very fine stainless steel mesh, and a tunnel (10) which envelopes the essential part of the conveyer; a steam supply pipe (13) with nozzles for injecting steam on the cooked rice both from the top and the bottom of the conveyer surface is arranged inside the tunnel passage (10) along the length of the conveyer; a nozzle (18), provided above the starting end of said conveyer (11) for spraying the cooking juice on the surface of the cooked rice being conveyed by said conveyer (11), the cooking juice being pooled in the sump (15) and containing gelatinized starch; said sump (15) for the cooking juice being provided with a supply pipe (19) for returning and supplementing the juice to the steam vessel (1) at its mid portion. The rice cooking system as claimed in one of claims 1 to 4, wherein a laterally swinging comb (12) is provided outside the duct (9) at the outlet of the steam vessel (1) at its terminal end for distributing and spreading the rice grains discharged from said duct onto the starting end of the conveyer (11) housed inside said steam tunnel passage (10). The rice cooking system as claimed in one of claims 1 to 5, wherein a conveyer (21) with a receptacle (22) is provided at the terminal end of said conveyer (11) of the steam tunnel passage (10) for receiving the cooked rice. The rice cooking system as claimed in claim 1 or 3, wherein a laterally swinging comb (20) is provided at the terminal end of said conveyer (11) in the steam tunnel passage for spreading and discharging the rice into the receptacle (22) on the conveyer (21). The rice cooking system as claimed in one of claims 1 to 7, wherein said steam vessel (1) has a sufficient length so that the vessel includes a section (A1) within which the steaming process for releasing the starch from the rice is carried out while the material rice charged from the inlet at the starting end is transported toward the terminal end of the vessel by the screw conveyer (3) and a section (A2) within which the gelatination of the starch released from the steamed rice takes place, and a section (A3) where adsorption of the gelatinized starch by the rice grains takes place. The rice cooking system as claimed in one of claims 1 to 8, wherein said steam tunnel passage (10) has a sufficient length so that the passage includes a system where said gelatinized starch is adsorbed by the rice grains as the cooking juice containing the gelatinized starch is sprayed on the rice grain surface at the starting end of said conveyer while the cooked rice is being conveyed by the conveyer, and a section where fixing process takes place in which the surface of the cooked rice grains is coated with said gelatinized starch under high temperature and high humidity as hot water vapor is sprayed. The rice cooking system as claimed in one of claims 1 to 9, wherein said steam tunnel passage (10) is connected at a right angle to the outlet of the steam vessel (1) at its terminal end.

Inventors: WATANABE KENJI, WATANABE, KENJI
Applicants: WATANABE KENJI, WATANABE, KENJI
Application year: 1989
Main classification: A23L1
IPC codes: A23L1, A47J27