Process for producing instant rice and instant rice

Abstract

Aspects in accordance with the present invention pertain to a process for producing instant rice reconstitutable with room-temperature water comprising the following steps: (a) steaming raw rice in the presence of water to obtain steamed rice; (b) freezing the steamed rice to decrease a steamed rice temperature to a frozen rice temperature to obtain frozen rice, and maintaining the frozen rice at a holding temperature for a predetermined holding period of time; (c) thawing the frozen rice to obtain thawed rice; and (d) drying the thawed rice in a vibrating fluidized bed dryer to obtain instant rice, in which the final moisture content of the instant rice is in the range of 4% to 12%, and the bulk density of the instant rice is 0.55 g / cm3 or lower.

Description

[0001] TITLE OF THE INVENTION

[0002] PROCESS FOR PRODUCING INSTANT RICE AND INSTANT RICE

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a process for producing instant rice and instant rice obtained by the production process.

[0005] BACKGROUND OF THE INVENTION

[0006] Nowadays, the demand for instant foods has been increasing because of the fast-paced lifestyle. The research and development of instant food productions has been developed consistently, particularly for rice which is one of the main staple foods for the world’s population. Most conventional processes for producing instant rice are unlikely to solve the problems of workability, drying efficiency, and properties of instant rice after rehydration.

[0007] Japan Patent Publication No.52-31944 discloses instant rice obtained by a method including freezing drying after immersion in hot water to improve the water absorption of the product. After rehydration, nevertheless, the instant rice is not satisfactory as the authentic cooked rice in terms of texture, flavor, and outer appearance.

[0008] Japan Patent Publication No. 62-181746 describes a process for producing rehydrated rice which is excellent in rehydration when heating with microwave oven. However, the method comprises the hot water immersion step consuming long processing time. Thus, this method is not workable for production.

[0009] Japan Patent Publication No. 56-151472 presents a method for preparing instant rice having a quick hot water reconstitution property by controlling the water content of alpharized rice. The publication also reflects the problems of rice deformation and agglomeration, and adverse drying efficiency in case of inappropriate water content control.

[0010] US Patent Publication No. 2019 / 0254319 describes an efficient production method of instant rice, which provides excellent rice’s properties after rehydration in a short time. According to this publication, the rehydration of instant rice is merely applicable by heating or adding hot water. Consequently, this product is not suitable for emergency situations having no heat, electricity or gas.

[0011] Although some prior arts disclose the processes for producing instant rice which is needless to be rehydrated by hot water, said instant rice requires a long rehydration time. One example is a

[0012] SUBSTITUTE SHEET (RULE 26) Japanese Patent Application No. 34-5730 which shows that instant rice obtained by the disclosed method can be rehydrated in 50 minutes by water, or in 25 minutes by hot water.

[0013] As a result, it is still a challenge for instant food manufacturers to develop the workable process for producing instant rice which enables to eat in a short time without the heat added for rehydration and obtain the rehydrated rice exhibiting the similar properties as the authentic cooked rice.

[0014] SUMMARY OF THE INVENTION

[0015] It is an objective of the present invention to provide instant rice that can quickly rehydrate in various circumstances, such as using room-temperature water, hot water, or a microwave, while ensuring that the flavor and sensory characteristic of the reconstituted instant rice closely resemble those of freshly cooked rice.

[0016] In order to achieve the above objective, an embodiment of the present invention provides a process for producing instant rice reconstitutable with room-temperature water comprising the following steps: (a) steaming raw rice in the presence of water to obtain steamed rice; (b) freezing the steamed rice to decrease a steamed rice temperature to a frozen rice temperature to obtain frozen rice, and maintaining the frozen rice at a holding temperature for a predetermined holding period of time; (c) thawing the frozen rice to obtain thawed rice; and (d) drying the thawed rice in a vibrating fluidized bed dryer to obtain instant rice, in which the final moisture content of the instant rice is in the range of 4% to 12%, and the bulk density of the instant rice is 0.55 g / cm3or lower.

[0017] According to the embodiment of the present invention, since the porosity of the rice microstructure can be increased and the vibrating fluidized bed drying can expedite the moisture transfer rate, a porous structure and short rehydration time of the instant rice can be obtained.

[0018] The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for the purpose of illustration only, a preferred embodiment in accordance with the present invention.

[0019] BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 A is the instant rice obtained from the process of one embodiment of the present invention.

[0021] Fig. IB is the instant rice that is commercially available.

[0022] Fig. 2A is the bulk instant rice obtained from the process of one embodiment of the present invention.

[0023] SUBSTITUTE SHEET (RULE 26) Fig. 2B is the bulk instant rice that is commercially available.

[0024] Fig. 3A is the bulk instant rice obtained from the process of one embodiment of the present invention.

[0025] Fig. 3B is the bulk instant rice that is commercially available.

[0026] Fig. 4A is the instant rice obtained from the process of one embodiment of the present invention that was rehydrated in room-temperature water.

[0027] Fig. 4B is the instant rice obtained from the process of one embodiment of the present invention that was rehydrated in hot water of 80°C.

[0028] Fig. 4C is the instant rice obtained from the process of one embodiment of the present invention that was rehydrated by microwave.

[0029] DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0030] It is to be understood that the following detailed description will be directed to embodiments, provided as examples for illustrating the concept of the present invention only. The present invention is in fact not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of this invention will be limited only by the appended claims.

[0031] The detailed description of the invention is divided into various sections only for the reader’s convenience and disclosure found in any section may be combined with that in another section.

[0032] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0033] It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0034] The term “about” when used before a numerical designation, e.g., dimensions, time, amount, and such other, including a range, indicates approximations which may vary by ( + ) or ( - ) 10 %, 5 % or 1 %, or any sub-range or sub-value there between.

[0035] “Comprising” or “comprises” is intended to mean that the articles and methods include the recited elements, but not excluding others. “Consisting essentially of’ when used to define

[0036] SUBSTITUTE SHEET (RULE 26) articles and methods, shall mean excluding other elements of any essential significance to the combination for the stated purpose. Thus, a device or method consisting essentially of the elements as defined herein would not exclude other materials or steps that do not materially affect the basic and novel characteristic(s) of the claimed invention. “Consisting of’ shall mean excluding more than trace elements of other ingredients and substantial method steps. Embodiments defined by each of these transition terms are within the scope of this invention.

[0037] In one aspect, a process for producing instant rice reconstitutable with room-temperature water of the present invention includes: step (a) steaming raw rice in the presence of water to obtain steamed rice; step (b) freezing the steamed rice to decrease a steamed rice temperature to a frozen rice temperature to obtain frozen rice, and maintaining the frozen rice at a holding temperature for a predetermined holding time; step (c) thawing the frozen rice to obtain thawed rice; and step (d) drying the thawed rice in a vibrating fluidized bed dryer to obtain instant rice. Hereinafter, each step will be described in detail.

[0038] Step of Steaming Raw Rice (Step a)

[0039] The raw rice, as a raw material, used for the production of instant rice of the present invention is not particularly limited, and may be of a long grain rice variety (scientific name: Oryza sativa L. indica). Generally, the length of long grain type is more than 4.50 mm and the width is more than 1.50 mm. Examples thereof include Fragrant Rice, Jasmine rice, Thai Hom Mali rice, Kao Dok Mali rice, Thai SangYod rice, or Thai Phathumthani 1 rice.

[0040] The “instant rice” means dehydrated rice that can be rehydrated in a relatively short period of time by the addition of water with or without heat and is then ready for consumption.

[0041] In the process for producing instant rice according to the present embodiment, first, the raw rice may be sorted and / or washed, if needed.

[0042] For step (a), the raw rice is steamed in the presence of water to obtain the steamed rice. A method for steaming the raw rice is not particularly limited, but a method involving using steam chamber, such as using a batch-type or continuous-type steamer at an atmospheric pressure, is preferable.

[0043] Steaming conditions (a steaming temperature and a steaming time) and the like are not particular limited and can be adjusted in accordance with variety of the raw rice used, production year, the amount processed, and the like to achieve full gelatinization of the rice grain. Ordinarily, a steam chamber temperature of 80° C or higher (preferably 90 °C to 100 °C) and the steaming

[0044] SUBSTITUTE SHEET (RULE 26) time of 90 minutes or shorter (preferably 30 to 90 minutes, more preferably 60 minutes) can be exemplified.

[0045] In the step of steaming the raw rice in the present invention, the raw rice is subjected to be heated until it is fully gelatinized to obtain the steamed rice. In more detail, the raw rice is soaked in the water before steaming. The weight ratio of the raw rice and the water ranges from 1:1 to 1:2, preferably ranges from 1:1.25 to 1:1.5. It is preferable to adjust the thickness of the raw rice to a maximum of 4 inches to ensure uniform gelatinization of every rice grain.

[0046] The main function of the water, in which the raw rice is soaked during the steaming, is to increase the level of moisture within the rice grain to promote gelatinization of the starch within the rice grain during the steaming process.

[0047] Trials conducted on processing rice solely by steaming alone show that without the presence of the water with the raw rice, gelatinization of starch within the rice grain will be less likely to fully occur.

[0048] In addition, steam is used to prevent the fully gelatinized grains from sticking together, ensuring that the final product is more appealing to consumers.

[0049] Step of Freezing Steamed Rice (Step b)

[0050] The process for producing instant rice includes step (b), which is to freeze the steamed rice to obtain the frozen rice. At this step, the steamed rice is frozen so that the steamed rice temperature is decreased to the frozen rice temperature.

[0051] In this embodiment, the device to be used is not particularly limited as long as the steamed rice temperature can be decreased to the frozen rice temperature within a predetermined period of time. Preferably, the freezing step is performed by putting the steamed rice into a freezer.

[0052] Freezing conditions and the like are not particularly limited. The freezing temperature and the freezing time are adjusted in accordance with variety of the raw rice to be used, production year, or the amount processed. In one embodiment, the frozen rice temperature is -25° C to 0° C, preferably -20° C to -15° C.

[0053] In another embodiment, the temperature of the frozen rice is decreased from the steamed rice temperature to 0° C within 2 to 4 hours and from 0° C to the frozen rice temperature within 3 to 4 hours. The frozen rice temperature preferably ranges from -18° C to -5° C.

[0054] The freezing after steaming can stop the cooking that progress by residual heat. This results in a non-clumping condition in which the stickiness of the rice grain surfaces is suppressed.

[0055] SUBSTITUTE SHEET (RULE 26) Moreover, this step increases the porosity of the rice microstructure due to the volume expansion of ice crystals during freezing.

[0056] After the temperature of the frozen rice reaches the frozen rice temperature, step (b) further includes maintaining the frozen rice at the holding temperature for the predetermined holding time.

[0057] In more detail, the holding temperature is set to be lower than the melting point of the water in the frozen rice. It is preferably left the frozen rice for at least 5 hours at -25° C to 0° C, more preferably 10 to 24 hours at -20° C to -15° C. Maintaining the frozen rice at the holding temperature can be performed by, for example, leaving the frozen rice in the freezer.

[0058] Step of Thawing Frozen Rice (Step C)

[0059] The frozen rice is then subjected to step (c), which is thawing to obtain the thawed rice. Thawing methods are not particularly limited, but it is preferably carried out at such the thawing time and the thawing temperature to prevent spoilage. It may be performed by placing the frozen rice in a chiller or a microwave chamber.

[0060] In the present embodiment, the frozen rice is thawed in the chiller, the thawing temperature is at 5° C or more, preferably 5° C to 15° C, and the thawing time is at least 1 hour, preferably 1 to 4 hours.

[0061] Step of Drying Thawed Rice (Step D)

[0062] Subsequent step (d) is to dry the thawed rice in the vibrating fluidized bed dryer, thereby efficiently obtaining the instant rice that is rehydrated in a room-temperature water at a short time and exhibits excellent flavor, texture, and outer appearance after reconstitution.

[0063] In this embodiment, the thawed rice is dried in the vibrating fluidized bed dryer to achieve the final moisture content of the instant rice of between 4 to 12 %, preferably 5 to 6%, and the bulk density of 0.55 g / cm3or lower, preferably 0.35 to 0.55 g / cm3. The vibrating fluidized bed dryer provides hot air as a fluidizing medium. At this step, a hot air temperature is at 80° C or higher, a drying time is at 180 minutes or less, preferably 30 to 60 minutes, a hot air velocity is at 1 m / s or higher, preferably 1 to 5 m / s. For a hot air flow rate, it is preferably 5,000 m3 / hr or higher.

[0064] Changes in rice structure during drying are usually caused by collapse due to water loss or are the result of expansion due to vapor generation. For the vibrating fluidized bed drying, it can expedite the moisture transfer rate. Subsequently, a porous structure and short rehydration time of the instant rice can be obtained.

[0065] SUBSTITUTE SHEET (RULE 26) Moreover, trials conducted on processing rice solely by drying after steaming without the freezing step and the thawing step show that the bulk density of the instant rice is higher than the instant rice with the freezing and thawing step. This indicates that the freezing and thawing help enhance the porosity of the rice structure. Consequently, the moisture transfer in either the drying or rehydration process would be facilitated. Moreover, porous structure created allows easy and faster rehydration of the product in use.

[0066] The present invention is also directed to the instant rice obtained by the above-described production process.

[0067] The present invention further provides an instant food containing the above-described instant rice. The instant food can contain other components. Examples of other components include, but not limited to, seasoning, dried vegetables, and dried meat. The instant food can be filled in a container. Examples of the container include, but not limited to, a can (made of steel, aluminum, or the like), a pack (such as plastic, paper, or the like).

[0068] It can be understood that the instant rice of the present invention can achieve an improvement in flavor, texture, and outer appearance than the commercial instant rice. The instant rice by the production process according to the present embodiment is not only rehydrated to the original cooked rice by pouring hot water, but it can be rehydrated to the original cooked rice by pouring room-temperature water and holding it in a short period of time (for example: less than 30 minutes).

[0069] EXAMPLE

[0070] In the example described below, dried milled Thai jasmine rice was used as the raw rice.

[0071] The raw rice having the bulk density of 0.84 g / cm3and the moisture content of 15% was used as a raw material in accordance with one embodiment of the present invention.

[0072] The raw rice was soaked in the water with the weight ratio of the raw rice and the water of 1:1.25 and the thickness of the raw rice was adjusted to 4 inches. Then, the raw rice with the presence of the water was placed in the steam chamber having the steam chamber temperature of 100 °C for 60 minutes. The steamed rice was then discharged to the freezer to decrease the steamed rice temperature to the frozen rice temperature to obtain the frozen rice of -20°C. After the temperature of the frozen rice reaches -20 °C, the frozen rice was maintained in the freezer at -20 °C for 24 hours.

[0073] The frozen rice was then removed from the freezer and placed in the thawing chamber at 10 °C for 4 hours. Then, the thawed rice was placed in the vibrating hot air fluidized bed dryer. The

[0074] SUBSTITUTE SHEET (RULE 26) drying process continued at the hot air temperature of 80 °C, the hot air flow rate of 5,000 m3 / hr, and the hot air velocity of 1 m / s, for 30 minutes to obtain the instant rice. The final moisture content of the instant rice was decreased to 5% and the bulk density was 0.35 g / cm3.

[0075] According to the results, Fig. 1 shows the instant rice in the form of individual grain before the reconstitution process. Fig. 1A represents the instant rice obtained from the process of one embodiment of the present invention while Fig. IB represents the instant rice that is commercially available.

[0076] The instant rice obtained from the process of one embodiment of the present invention showed an excellent appearance, i.e. the color is whiter, and the cracked and fissured grains were significantly fewer when compared to the commercial instant rice. Moreover, the bulk density was also lower, showing that the instant rice structure was more porous. As a result, it can be rehydrated and ready to consume within a shorter period of time.

[0077] Fig. 2 shows the bulk instant rice before the reconstitution process. Fig. 2A represents the bulk instant rice obtained from the process of one embodiment of the present invention while Fig. 2B represents the bulk instant rice that is commercially available.

[0078] According to the results, the instant rice obtained from the process of one embodiment of the present invention had less agglomeration compared with the commercial instant rice.

[0079] Fig. 3 shows the bulk instant rice after the reconstitution process. Fig. 3A represents the bulk instant rice obtained from the process of one embodiment of the present invention while Fig. 3B represents the bulk instant rice that is commercially available.

[0080] According to the results, the comparison shows that the instant rice obtained from the process of one embodiment of the present invention had better color and texture than the commercial instant rice. In addition, the flavor and reconstituted sensory characteristic of the instant rice obtained from the process of one embodiment of the present invention were more similar to those of freshly cooked rice.

[0081] Fig. 4 shows the instant rice obtained from the process of one embodiment of the present invention after the reconstitution process at the different temperatures and different methods. Fig. 4A shows the instant rice that was rehydrated in less than 30 minutes in room-temperature water, Fig. 4B shows the instant rice that was rehydrated in less than 7 minutes in hot water of 80° C, and Fig. 4C shows the instant rice that was rehydrated in less than 3 minutes by microwave.

[0082] SUBSTITUTE SHEET (RULE 26) Moreover, further study relating to the shelf life of rehydrated or reconstituted instant rice produces by the process in accordance with this embodiment shown that it remained spoilage- free when stored at room-temperature for more than 12 hours. This durability is attributed to the thermal sterilization conditions employed during the production process. Consequently, instant rice produced using this method can prove advantageous in emergency situations like natural disasters, pandemics, or wartime scenarios.

[0083] SUBSTITUTE SHEET (RULE 26)

Claims

CLAIMS1. A process for producing instant rice reconstitutable with room-temperature water comprising the following steps:(a) steaming raw rice in the presence of water to obtain steamed rice;(b) freezing the steamed rice to decrease a steamed rice temperature to a frozen rice temperature to obtain frozen rice, and maintaining the frozen rice at a holding temperature for a predetermined holding time;(c) thawing the frozen rice to obtain thawed rice; and(d) drying the thawed rice in a vibrating fluidized bed dryer to obtain instant rice, wherein the final moisture content of the instant rice is in the range of 4% to 12%, and the bulk density of the instant rice is 0.55 g / cm3or lower.

2. The process of claim 1, wherein the weight ratio of the raw rice and the water ranges from 1 : 1 to 1 :2.

3. The process of claim 1 or 2, wherein the raw rice is steamed at a steam chamber temperature of 80 °C or higher for less than or equal to 90 minutes.

4. The process of claim 3, wherein the raw rice is steamed at the steam chamber temperature ranging from 90° C to 100°C for 30 to 90 minutes.

5. The process of claim 4, wherein the raw rice is steamed at the steam chamber temperature ranging from 90 °C to 100 °C for 60 minutes.

6. The process of any one of claims 1 to 5, wherein the thickness of the raw rice being steamed is 4 inches or lower.

7. The process of any one of claims 1 to 6, wherein the frozen rice temperature ranges from -25 °C to 0°C.

8. The process of claim 7, wherein the frozen rice temperature ranges from -20 °C to -15°C.SUBSTITUTE SHEET (RULE 26)9. The process of any one of claims 1 to 8, wherein the steamed rice is frozen by a freezer.

10. The process of any one of claims 1 to 9, wherein the temperature of the frozen rice is decreased from the steamed rice temperature to 0° C within 2 to 4 hours and from 0° C to the frozen rice temperature within 3 to 4 hours.

11. The process of claim 10, wherein the frozen rice temperature ranges from -18° C to -5° C.

12. The process of any one of claims 1 to 11, wherein the holding temperature ranges from -25 to 0°C and the holding time is at least 5 hours.

13. The process of claim 12, wherein the holding temperature ranges from -20 °C to -15°C and the holding time ranges from 10 to 24 hours.

14. The process of any one of claims 1 to 13, wherein a thawing temperature is at least 5°C and a thawing time is at least 1 hour.

15. The process of claim 14, wherein the thawing temperature ranges from 5 °C to 15°C and the thawing time ranges from 1 to 4 hours.

16. The process of any one of claims 1 to 15, wherein the vibrating fluidized bed dryer provides hot air as a fluidizing medium.

17. The process of any one of claims 1 to 16, wherein a drying time to dry the thawed rice in the vibrating fluidized bed dryer is less than or equal to 180 minutes.

18. The process of claim 17, wherein the drying time to dry the thawed rice in the vibrating fluidized bed dryer ranges from 30 to 60 minutes.

19. The process of any one of claims 16 to 18, wherein a hot air temperature to dry the thawed rice is 80 °C or higher.

20. The process of any one of claims 16 to 19, wherein a hot air flow rate is 5,000 m3 / hr or higher.SUBSTITUTE SHEET (RULE 26)21. The process of any one of claims 16 to 20, wherein a hot air velocity is 1 m / s or higher.

22. The process of claim 21, wherein the hot air velocity ranges from 1 to 5 m / s.

23. A process for producing instant rice reconstitutable with room-temperature water comprising the following steps:(a) steaming raw rice in the presence of water to obtain steamed rice, at a steam chamber temperature ranging from 90 °C to 100 °C for 60 minutes, the weight ratio of the raw rice and the water ranges from 1 : 1 to 1 : 2, and the thickness of the raw rice being steamed is 4 inches or lower;(b) freezing the steamed rice to decrease a steamed rice temperature to a frozen rice temperature ranging from -20 °C to -15°C for 2 to 4 hours to obtain frozen rice, and maintaining the frozen rice at a holding temperature ranging from -20 °C to -15°C for a holding period of time ranging from 10 to 24 hours;(c) thawing the frozen rice at 5 °C to 15 °C for 2 to 4 hours to obtain thawed rice; and(d) drying the thawed rice in a vibrating hot air fluidized bed dryer with a hot air velocity of 1 m / s or higher, at 80 °C or higher for 30 to 60 minutes to obtain instant rice, wherein the raw rice is long grain rice (Oryza sativa L. indica) and the final moisture content of the instant rice is in the range of 4% to 12%, and the bulk density of the instant rice ranges from 0.35 to 0.55 g / cm3.

24. Instant rice obtained from the process of any one of claims 1 to 23.

25. Instant food comprising instant rice according to claim 24.SUBSTITUTE SHEET (RULE 26)

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