Classifications

• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES, NOT OTHERWISE PROVIDED FOR; PREPARATION OR TREATMENT THEREOF
  • A23L7/00—Cereal-derived products; Malt products; Preparation or treatment thereof
  • A23L7/10—Cereal-derived products
  • A23L7/196—Products in which the original granular shape is maintained, e.g. parboiled rice
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES, NOT OTHERWISE PROVIDED FOR; PREPARATION OR TREATMENT THEREOF
  • A23L7/00—Cereal-derived products; Malt products; Preparation or treatment thereof
  • A23L7/10—Cereal-derived products
  • A23L7/197—Treatment of whole grains not provided for in groups A23L7/117 - A23L7/196
  • A23L7/1975—Cooking or roasting

Definitions

• the present invention relates to methods and installations for parboiling and preparing rice and parboiled rice.
• Parboiled rice is rice that has been soaked, heat treated, dried and often processed. This treatment makes it possible in particular to have a non-sticky rice and the grains of which are intact, but with the drawback that the cooking time is longer.
• the invention overcomes this drawback by a method of steaming rice, both paddy and cargo, which makes it possible to obtain parboiled rice whose cooking time is very shortened.
• the process according to the invention consists in soaking the rice in water at a temperature below 70 ° C. under conditions and for a duration such that, after removal of the surface water by draining or draining, soaked rice with a moisture content by weight of more than 31%.
• the soaked rice is then gelatinized by bringing it to a temperature above 130 ° C., while maintaining the humidity at a weight content greater than 20% for a sufficient time to obtain gelatinized rice at heart.
• gelatinization is carried out by passing the rice soaked continuously in an enclosure, so as to limit, by the balance which is established in the enclosure between the moisture content of the rice which undergoes gelatinization and the moisture content of the gaseous atmosphere of the enclosure, the quantity of vapor which is released from the rice during gelatinization to maintain the weight humidity of the rice during gelatinization at a value greater than 20% and by heating the rice soaked in the enclosure essentially by conduction, so as not to increase substantially the moisture content by weight of gelatinized rice, and in particular not to exceed a content of 28%.
• the soaking is generally carried out for at least three hours at a temperature of 40 to 70 ° C., the duration being able to be all the shorter the higher the temperature.
• the ratio of the volume of rice to that of water is at least 2.5.
• the soaking can be carried out in a tank or a hopper.
• the draining device can be a vibrating filter which ensures the separation of the water on the surface of the rice grains, representing in particular from 2 to 3% by weight.
• the gelatinized rice is dried to a moisture content of 11 to 13% by weight in order to obtain marketable rice and, if necessary, the dried rice is also milled.
• the passage time or residence time of the rice soaked in the enclosure is between four and ten minutes. Beyond ten minutes, it may happen that the moisture content of the rice decreases too much.
• the invention also relates to a process for the preparation of rice which consists in steaming it by the process according to the invention, in cooling it to room temperature (15 to 30 ° C), while maintaining its humidity at more than 19% , machine the cooled rice, reheat it at least to 75-80 ° C, then flatten the reheated rice, and dry it to a humidity of 11 to 13%.
• the grains are transferred to a drying column to be cooled there.
• this column the rice is traversed by a stream of air at room temperature. This rice is thus brought back to room temperature, losing 3 to 5% of humidity.
• the machining is carried out by successive passage in 3 machining cones conventionally used to whiten the rice.
• these devices consist of a metal truncated cone, coated with an abrasive layer and rotating inside an enclosure made of a perforated sheet exactly the same shape, but slightly larger .
• the rice is introduced between the truncated cone and the metal cage, it is arranged in a ring by turning with the truncated cone.
• the grain whitening results from the friction of the grains against the abrasive surface and also of the grains against each other. To achieve a complete bleaching, that is to say the exposure of the grain endosperm.
• the milled rice grains are immediately subjected to heating and flattening.
• the humidity of the rice at the end of the milling is between 17 and 20% humidity. If the flattening of the grains takes place without prior reheating, by passing between cold metal rollers, we observe the appearance of numerous broken grains which are partially torn off during the flattening. There is a 20% increase in weight in the product. Only 25% of the grains remain intact, undistorted and without missing parts.
• Reheating the grains above their gelatinization temperature from 60 ° to 75 ° C depending on the variety, makes it possible to significantly increase their plasticity by passing the glass transition temperature of the starch. This heating must be carried out without modifying the grain moisture. Heating with hot air, for example, would cause rapid moisture loss and stiffening of the grain with significant cracking and breaking.
• infrared to heat the grains is perfectly suitable, treated in a single layer, the grains pass from 25 ° to 80 ° C in 20 seconds without changing their humidity.
• the grains thus reheated can be flattened without the formation of broken grains and with a rate of cracked grains (cracks visible to the naked eye) of less than 10% (number of cracked grains / number of total grains).
• the flattening is carried out by passing between two metal rollers, for example the rollers used for flaking cereals.
• the spacing of the rollers is adjusted between 0.2 and 0.5 mm, preferably between 0.3 and 0.4 mm to obtain the desired effect on the grains.
• the identical speed for the two rollers is adjusted between 20 and 60 rpm, preferably between 30 and 50 rpm.
• Grains of flattened rice are then immediately transferred to a drying column where they are traversed by a stream of air at a temperature below 50 ° C. They are thus gradually brought back to a humidity of 11 to 13% to be then conditioned.
• the thickness of the grains is measured in the following manner.
• the cross section of the grain in the middle reveals an ovoid surface.
• the thickness E taken into account by the measurement is the smallest section taken in the middle of the grain.
• the measurement of the thickness E is carried out with the caliper on the middle of the grain seen in profile.
• the average thickness E of 100 grains taken at random is at least 15% less than the thickness E of the dry grain which has not been flattened.
• the flattening will reduce the thickness of the grain by 20 to 25%, it being understood that E must not be less than 0.9 mm, nor more than 1, 3 mm.
• the grains are too flat, resemble discs, and cannot reasonably be described as rice grains. For the uninformed consumer, they fall into the category of flakes. It is preferred that E is between 1.1 and 1.2 mm. After flattening and drying, the rice obtained has more than 90% of the uncracked grains.
• the cracked grains are qualified as cleaved rice, they present one or more fractures clearly visible to the naked eye, always transverse and going from one side to the other of the grain. They result from too high tensions inside the grain generated by too great differences in temperature and / or humidity between the interior and the periphery of the grains.
• the invention also relates to an installation for steaming rice, which successively comprises a soaking tank, a draining device and an enclosure having an inlet and an outlet, means for heating the enclosure and means intended for making vibrate the enclosure to pass the rice from the inlet to the outlet.
• the continuous installation according to the invention makes it possible to treat all the grains individually and uniformly and behaves both as a heat exchanger and a divided gas-solid chemical reactor.
• the rice grains upon entering the enclosure, will be individually heated by contact with the hot wall of the enclosure.
• the moisture contained uniformly in the grain will gradually turn into vapor as the grain heats up.
• the sky of the enclosure will at the same time be charged with water vapor and maintain a humidity around the grain which limits its dehydration and thus allows the complete gelatinization of the starch.
• the passage time In order for the treatment to operate satisfactorily and for the grains to be completely processed, the passage time must allow the temperature of the grain to rise to 130 ° C.
• the residence time of the grains in the enclosure is governed by its length and by the frequency of vibration applied.
• the residence time is adjusted as indicated above to obtain good confinement of the grains of rice in the enclosure, which limits the loss of water and maintains the vapor atmosphere around the grain.
• the invention relates to an installation in which there is provided at the outlet of the enclosure successively a cooling device, a machining device, a heating device, a flattening device and a drying.
• the invention also relates to a batch of grains of parboiled and uncracked rice which is characterized in that at least 90% of the grains are gelatinized at heart following the alkali test and have a firmness of less than 62 with the Chopin viscoelastograph after having been immersed in boiling water for eight minutes.
• the grains of parboiled rice according to the invention are gelatinized in a very homogeneous manner and that in particular 99% of the grains and even 100% of them are gelatinized and, however, in an entirely unexpected manner, the rice thus parboiled cooks very quickly.
• This short cooking time is also obtained with rice which does not have this amylose content, if it is subjected to the process described above using a flattening operation.
• the alkali test is carried out as follows.
• the Chopin viscoelastograph makes it possible to evaluate the viso-elastic characteristics of cooked rice by assessing its deformation under the application of a constant force of 700g for 20 seconds then relaxation of the force for 40 seconds.
• 100g of rice is cooked in one liter of boiling water.
• the grains are drained for one minute on a 1.25 mm opening sieve and then allowed to cool for 15 minutes in a 60 mm petri dish placed on a damp sponge plate and covered by a box. 80 mm Petri dish so that the latter creates a watertight seal with the water which soaks the sponge plate. Three grains thus cooled are then placed on the viscoelastograph.
• these rice grains parboiled according to the invention with an amylose content by weight relative to the dry matter of less than 15% have the following property: the cooked grains, placed in a hermetically sealed container and placed in the refrigerator at 4 ° C. for 6 days have a firmness, measured with a viscoelastograph, at most equal to 120% of that which they have 15 minutes after cooking. This property is in great demand, especially when you have to prepare a dish in advance.
• FIG. 1 of the accompanying drawing illustrates a part of the installation according to the invention
• Figures 2 and 3 illustrate two installations according to the invention.
• the input 9 is supplied from a vibrating filter serving as a draining device, itself supplied with wet rice by a conveyor belt coming from a soaking tank.
• the installation according to the invention shown in FIG. 2 successively comprises a soaking tank 2, an oven 8 enclosure, a device 22 for drying and a device 23 for machining.
• That of FIG. 3 successively comprises a soaking tank 24, a steaming chamber 8, a cooling device 25, a machining device 26, a heating device 27, a flattening device 28 and a device 29 for drying.
• the following examples illustrate the invention. In these examples, the parts and percentages are expressed by weight, unless expressly stated otherwise.
• Example 1 1 to 600 kg of Khao Dawk Mali cargo rice are placed in a tank and covered with 1500 liters of water at 65 ° C. The rice is left in contact with water for 3 hours. The soaking water is then discharged and the rice is extracted by gravity from the tank and drained on a vibrating filter which includes a vibration generator, a stainless steel mesh screen welded to a stainless steel frame and an anti-clogging system with nylon rings. Its humidity is then equal to
• the rice thus treated subjected to the alkali test has 98% of completely translucent grains, that is to say completely gelatinized.
• Example 2600 kg of Thai-Bonnet cargo are treated according to the method described in Example 1.
• the residence time in the enclosure is here 9 minutes. Its temperature reached at the exit of the enclosure is 140 ° C. Its humidity is 21.8%.
• the rice thus treated subjected to the alkali test has 95% of completely translucent grains, that is to say completely gelatinized. Its density is equal to 96% of the density of the same grain which has been machined but not treated. No cracks are visible to the eye or a binocular lens.
• This rice cooked for 8 minutes in boiling water and, cooled for 15 minutes according to the protocol described above, has the following texture characteristics measured with a viscoelastograph:
• Example 1 600 kg of Thai-Bonnet paddy are treated according to the process described in Example 1.
• the soaking time is here 7 hours and the temperature 68 ° C.
• the temperature set point for the enclosure is 230 ° C.
• the residence time in the enclosure is 8 minutes.
• the temperature of the rice reached at the exit of the enclosure is 155 ° C. Its humidity is 22.1%.
• the rice thus treated subjected to the alkali test has 95% of completely translucent grains, that is to say completely gelatinized. Its density is equal to 96% of the density of the same grain that has been machined but not treated. No cracks are visible to the eye or a binocular lens.
• Example 1 kg of Thai-Bonnet cargo is soaked according to the process described in Example 1, then after draining is subjected to a current of hot air at 200 ° C for 20 seconds. The humidity of the treated rice is then 23%. The rice is then dried and then machined according to the method of Example 1.
• This rice thus treated and subjected to the alkali test has 30% of grains which are still opaque, that is to say only partially gelatinized. Many grains are also cracked.
• Comparative Example 2 1 kg of Thai-Bonnet cargo is soaked according to the process described in Example 1, then after draining is subjected to a steam treatment under pressure of 2 bars for 20 seconds. The rice is then dried and then machined according to the process described in Example 1. This rice cooked for 8 minutes in boiling water and, cooled for 15 minutes according to the protocol described above, has the following texture characteristics measured with a viscoelastograph:
• Example 2 600 kg of Thai-Bonnet cargo are treated according to the process described in Example 2 until they leave the steaming chamber.
• the grains are then transported to a drying column where they are cooled to 25 ° C by a flow of ambient air.
• the residence time in the column is 15 min, the humidity of the rice drops to 18%.
• the rice is then milled by successive passage through 3 machining cones, which generate between 8 and 9.5% low flour and 4% broken rice.
• the rice thus treated subjected to the alkali test has 98% of completely translucent grains, that is to say completely gelatinized.
• Its density is equal to 94% of the density of the same milled but untreated rice. 4% of the grains have cracks visible to the naked eye.
• the average thickness of the grains is 1, 2 mm, that is to say a reduction of 23% compared to the thickness of the grains treated according to example 2.
• the rate of broken remains remains identical to that determined after machining is 4%.
• This rice cooked for 5 mm in boiling water and cooled for 15 min according to the protocol described above has the following texture characteristics measured with a viscoelastograph:
• the rice is then milled by successive passage through 3 machining cones, which generate between 8 and 9.5% low flour and 6% broken rice. It is then conveyed to a vibrating mat heated by infrared lamps. The grain temperature reaches 80 ° C in 20 seconds.
• the grain moisture is 18.5%.
• This mat also serves as a feed for the passage between the two metal rollers which will flatten the grains.
• the spacing of the rollers is adjusted to 0.30 mm, their speed at 45 rpm.
• the flattened grains are quickly conveyed to the drying columns where their humidity is brought down to
• the rice thus treated subjected to the alkali test has 99% of completely translucent grains, that is to say completely gelatinized. Its density is equal to 93% of the density of the same milled but untreated rice. 6% of the grains have cracks visible to the naked eye. The breaking rate is 6%, identical to that determined after machining. The average grain thickness is 1.1 mm, a reduction of 25% compared to the thickness of the grains treated according to Example 2.
• This rice cooks for 3 minutes in boiling water and, cooled for 15 minutes according to the protocol described above has the following texture characteristics measured with a viscoelastograph:

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• Health & Medical Sciences (AREA)
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• Chemical & Material Sciences (AREA)
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• Food Science & Technology (AREA)
• Polymers & Plastics (AREA)
• Cereal-Derived Products (AREA)
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• Commercial Cooking Devices (AREA)
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• 1998
  • 1998-06-17 FR FR9807627A patent/FR2779914B1/fr not_active Expired - Fee Related
• 1999
  • 1999-06-15 US US09/719,489 patent/US6562396B1/en not_active Expired - Fee Related
  • 1999-06-15 WO PCT/FR1999/001419 patent/WO1999065332A1/fr not_active Ceased
  • 1999-06-15 KR KR1020007014350A patent/KR100653749B1/ko not_active Expired - Fee Related
  • 1999-06-15 PT PT99925090T patent/PT1085823E/pt unknown
  • 1999-06-15 JP JP2000554222A patent/JP2002517989A/ja active Pending
  • 1999-06-15 ES ES99925090T patent/ES2275342T3/es not_active Expired - Lifetime
  • 1999-06-15 AU AU41493/99A patent/AU751587B2/en not_active Ceased
  • 1999-06-15 DE DE69933765T patent/DE69933765T2/de not_active Expired - Fee Related
  • 1999-06-15 EP EP99925090A patent/EP1085823B1/fr not_active Expired - Lifetime
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