Freeze-dried rice

Abstract

To provide freeze-dried rice which has an improved flavor and texture without damaging an advantage of restoring the freeze-dried rice in a short time and a production method thereof.SOLUTION: There is provided freeze-dried rice which includes a lactic acid or a salt thereof of an amount of 0.5 or more and less than 3 g in terms of a lactic acid value per 100 g of the freeze-dried rice. There is also provided a production method thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to freeze-dried cooked rice, specifically to dried frozen cooked rice containing lactic acid or a salt thereof, which has excellent reconstitution properties, flavor, and texture, and a method for producing the same. [Background technology]

[0002] In recent years, demand for dried cooked rice, known as alpha rice or freeze-dried rice, has been increasing as emergency food for disaster preparedness (stockpiling) or as a convenient, portable meal. Various research and development efforts have been conducted on their production methods. For example, alpha rice (non-freeze-dried cooked rice, typically hot-air-dried cooked rice) has superior flavor and texture compared to freeze-dried rice (freeze-dried cooked rice), but has the disadvantage of requiring time for reconstitution in water or hot water. To overcome this drawback, a method for producing instant rice has been reported, which involves steaming highly water-absorbent rice obtained by soaking raw rice in hot water and then drying it with hot air (see, for example, Patent Document 1). On the other hand, freeze-dried rice has the advantage of being reconstituted in water or hot water in a shorter time than alpha rice, but has the disadvantage of being inferior in flavor and texture. In particular, freeze-dried rice typically contains salt (sodium chloride) to ensure reconstitution, but this adds a salty taste, which has the disadvantage of impairing the flavor of the white rice itself. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-140962 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide freeze-dried cooked rice having improved flavor and texture without impairing the advantage of freeze-dried cooked rice that can be reconstituted in a short time, and a method for producing the same. [Means for solving the problem]

[0005] The present inventors have discovered that by replacing sodium chloride, which has conventionally been added during the production of freeze-dried cooked rice, with lactic acid or a salt thereof and adding this at a predetermined stage of two-stage heating, the flavor and texture of the resulting freeze-dried cooked rice are improved without impairing the advantage of rapid reconstitution, and have completed the present invention. The present invention is as follows:

[0006] [1] Freeze-dried cooked rice containing lactic acid or its salts in an amount of 0.5 g or more but less than 3 g of lactic acid per 100 g of freeze-dried cooked rice. [2] The freeze-dried cooked rice according to [1], wherein the lactic acid or a salt thereof is potassium lactate. [3] The freeze-dried cooked rice according to [1] or [2], further comprising at least one food additive selected from the group consisting of antioxidants and preservatives. [4] The freeze-dried cooked rice according to any one of [1] to [3], wherein the cooked rice is white rice and does not contain sodium chloride. [5] The freeze-dried cooked rice according to any one of [1] to [3], further containing a seasoning. [6] A method for producing freeze-dried cooked rice containing lactic acid or a salt thereof, (a) a step of soaking raw rice in water and then heating it to obtain primary heated rice; (b) adding lactic acid or a salt thereof in an amount of 0.5 g or more and 4 g or less in terms of lactic acid per 100 g of raw material rice to the first heated rice, and then heating the rice to obtain second heated rice; and (c) A step of freeze-drying the second-heated rice to obtain freeze-dried cooked rice. A manufacturing method comprising: [7] The method according to [6], wherein the lactic acid or a salt thereof is potassium lactate. [8] The manufacturing method according to [6] or [7], wherein step (c) is a step of slowly freezing the second-heated rice, then rapidly freezing it and freeze-drying it. [Effects of the Invention]

[0007] The freeze-dried cooked rice of the present invention has excellent reconstitution properties, flavor, and texture. The freeze-dried rice of the present invention is obtained by a simple method in which sodium chloride, which has conventionally been added during production, is replaced with lactic acid or a salt thereof, which is added at a predetermined stage of two-stage heating. The obtained freeze-dried cooked rice can be reconstituted in a short time, within 5 minutes, preferably within 3 minutes, and has excellent taste after reconstitution. Furthermore, since the obtained freeze-dried cooked rice contains lactic acid or a salt thereof but is substantially free of sodium chloride, the flavor can be enjoyed without being disturbed by saltiness, even when served as plain rice. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Freeze-dried rice) The present invention relates to freeze-dried cooked rice containing lactic acid or a salt thereof. In the present invention, "freeze-dried cooked rice" refers to cooked rice from which water has been removed by freeze-drying. The amount of lactic acid or a salt thereof contained in the freeze-dried cooked rice of the present invention is, in terms of lactic acid value per 100 g of freeze-dried cooked rice, 0.5 g or more, preferably 0.6 g or more, more preferably 0.8 g or more, even more preferably 1 g or more, particularly preferably 1.2 g or more, and also preferably less than 3 g, more preferably 2.8 g or less, even more preferably 2.5 g or less, and particularly preferably 2.3 g or less. The amount of lactic acid or a salt thereof contained in the freeze-dried cooked rice can be measured by known methods, such as high-performance liquid chromatography (HPLC) as described in the Examples below. The total amount is detected as lactic acid or converted to lactic acid, and the lactic acid value per 100 g of freeze-dried cooked rice is calculated based on these values.

[0009] The lactic acid or a salt thereof contained in the freeze-dried cooked rice of the present invention is preferably a salt of lactic acid, more preferably an alkali metal salt of lactic acid, even more preferably sodium or potassium lactate, and particularly preferably potassium lactate. These are commercially available as food additives and are available from suppliers as solids or aqueous solutions.

[0010] In one embodiment of the present invention, the freeze-dried cooked rice of the present invention preferably contains sodium or potassium derived from sodium or potassium lactate. According to the Standard Tables of Food Composition in Japan (8th Edition), the potassium content per 100 g of edible portion of "paddy rice" is less than 100 mg, and the sodium content is 1 mg or less. Specifically, the potassium content per 100 g of edible portion of paddy rice (polished rice / non-glutinous rice) is 29 mg, and the sodium content is 1 mg. Furthermore, since the water content per 100 g of edible portion is 60.0 g, the potassium content per 100 g of dry rice is 72.5 mg, and the sodium content per 100 g of dry rice is 2.5 mg. Therefore, the freeze-dried cooked rice of the present invention contains sodium (together with the sodium derived from the raw materials) in an amount of preferably 100 mg or more, more preferably 200 mg or more, even more preferably 300 mg or more, and preferably 1000 mg or less, more preferably 800 mg or less, and even more preferably 600 mg or less, or potassium (together with the potassium derived from the raw materials) in an amount of preferably 200 mg or more, more preferably 250 mg or more, even more preferably 300 mg or more, and preferably 1300 mg or less, more preferably 1200 mg or less, and even more preferably 1100 mg or less. The amount of sodium or potassium contained in the freeze-dried cooked rice can be measured by known methods, for example, atomic absorption spectrometry as described in the Examples below, and the content per 100 g of freeze-dried cooked rice can be calculated based on the results.

[0011] The freeze-dried cooked rice of the present invention may also contain food additives depending on the purpose, as long as the effects of the present invention are not impaired. Such food additives are typically antioxidants and / or preservatives. The antioxidant is not particularly limited as long as it is usable as a food additive, and examples thereof include vitamin E, vitamin C, erythorbic acid, tea extract, etc., with vitamin E being preferred. The preservative is not particularly limited as long as it is usable as a food additive, and examples thereof include polylysine, sorbic acid or a salt thereof, and trehalose, with trehalose being preferred. These may be used alone or in combination of two or more. The amount added may be appropriately determined depending on the purpose.

[0012] In one embodiment of the present invention, freeze-dried cooked rice that is substantially free of sodium chloride can be provided. Such an embodiment is suitable when the cooked rice does not need to have a salty taste, particularly when the cooked rice is white rice.

[0013] In another embodiment of the present invention, the freeze-dried cooked rice may contain ingredients and / or seasonings depending on the purpose. The seasonings are not particularly limited as long as they can be used as foods and food additives, and examples thereof include amino acids, nucleic acids, organic acids, inorganic salts, etc., which may be used alone or in combination of two or more. The amount of addition may be appropriately determined depending on the purpose.

[0014] (Method of producing freeze-dried cooked rice) The method for producing freeze-dried cooked rice containing lactic acid or a salt thereof of the present invention comprises the steps of: (a) a step of soaking raw rice in water and then heating it to obtain primary heated rice; (b) adding lactic acid or a salt thereof in an amount of 0.5 g or more and 4 g or less in terms of lactic acid per 100 g of raw material rice to the first heated rice, and then heating the rice to obtain second heated rice; and (c) A step of freeze-drying the second-heated rice to obtain freeze-dried cooked rice. Includes.

[0015] In step (a), the starting material rice is first soaked in water to prepare water-absorbed rice. The soaking process is typically carried out by soaking the starting material rice in water at 30°C or below, followed by draining. There are no particular limitations on the type or brand of rice used as the starting material. It may be not only wash-free rice or polished rice, but also brown rice or germ rice. The type of rice is also not limited to Japonica rice (short grain rice). Preferably, polished rice or wash-free rice is used as the starting material rice.

[0016] When the starting rice is polished rice or no-wash rice (polished rice is used after being washed in advance), it is soaked in water at 30°C or below, preferably 10°C to 30°C, and more preferably at room temperature (about 20±5°C), to allow the starting rice to uniformly absorb water. The soaking time is usually about 0.5 to about 16 hours, but preferably about 1 to about 4 hours. After soaking, the water is drained to obtain absorbed rice. The weight of the absorbed rice is preferably in the range of about 120% to about 140% of the weight of the starting rice (or the weight after washing, if washed). The absorbed rice obtained in this manner can be used in step (a).

[0017] In step (a), the water-absorbed rice is primarily heated. This results in primarily heated rice in which at least a portion of the rice surface has been gelatinized. While the specific heating method is not particularly limited, atmospheric pressure steam heating is preferred. For example, the primarily heated rice can be obtained by atmospheric pressure steam heating at a temperature of about 90°C to about 100°C for a heating and holding time of about 0 to about 60 minutes, preferably about 0 to about 20 minutes, after the rice temperature has reached that temperature.

[0018] In step (b), the first-heated rice obtained in step (a) is second-heated in the presence of lactic acid or a salt thereof. The second-heating process results in second-heated rice that is gelatinized to the center of the rice. Preferred embodiments of lactic acid or a salt thereof are as described above. This two-stage heating process allows for the production of dried cooked rice with excellent rehydration properties and flavor.

[0019] Lactic acid or a salt thereof is added to the first-heated rice by adding a mixture of lactic acid or a salt thereof and water. The amount of lactic acid or a salt thereof added is preferably 0.5 g or more, more preferably 1 g or more, and preferably 4 g or less, more preferably 3.5 g or less, in terms of lactic acid equivalent per 100 g of raw material rice. Lactic acid or a salt thereof is mixed with about 140 g to about 380 g of water per 100 g of first-heated rice, and the resulting mixture is added to the first-heated rice by any method, mixed by any method, and then subjected to second heating. Note that food additives may be added to the mixture of lactic acid or a salt thereof and water depending on the purpose, as long as they do not impair the effects of the present invention. Such food additives are typically antioxidants and / or preservatives, and specific examples and preferred embodiments of food additives are as described above. Furthermore, when the freeze-dried cooked rice of the present invention contains ingredients and / or seasonings, the ingredients and / or seasonings may be added to the first-heated rice together with the mixture of lactic acid or a salt thereof and water, followed by second heating.

[0020] The specific method of secondary heating in step (b) is not particularly limited, but atmospheric steam heating is preferred, and for example, secondary heated rice is obtained by atmospheric steam heating at a temperature of about 90°C to about 100°C for a heating and holding time of about 0 to about 60 minutes, preferably about 10 to about 40 minutes, after the product temperature reaches that temperature. The obtained secondary heated rice is preferably washed with water at 40°C or below to remove slime from the surface of the cooked rice.

[0021] In step (c), the second-heated rice obtained in step (b) is freeze-dried. Freeze-drying can be performed by known methods. Preferably, the second-heated rice is slowly frozen, then rapidly frozen, and freeze-dried. Slow freezing typically refers to freezing at about -5±5°C for 30 minutes or more. The slow freezing time in the production method of the present invention is preferably 1 hour or more, more preferably 3 hours or more, even more preferably 8 hours or more, and preferably 48 hours or less, more preferably 36 hours or less, and even more preferably 24 hours or less. The second-heated rice is then rapidly frozen at about -20°C or less, preferably about -30°C or less, and then freeze-dried under reduced pressure, preferably at about 0.8 Torr or less, more preferably 0.3 Torr or less.

[0022] When the freeze-dried cooked rice of the present invention contains ingredients and / or seasonings, the ingredients and / or seasonings may be added to the second heated rice before freeze-drying and then freeze-dried, or the dried ingredients and / or dried seasonings may be added after freeze-drying.

[0023] The freeze-dried cooked rice obtained in this manner can be subjected to coarse crushing (disintegration), single graining, or granularity regulation as necessary, and then appropriately packaged to be provided as emergency food for disaster prevention (stockpiling) or as a convenient, portable meal. [Example]

[0024] The present invention will be described in more detail below using examples, but these examples are not intended to limit the scope of the present invention in any way.

[0025] (Comparative Example 1) 25.8 g of polished rice was washed with room-temperature water (approximately 20°C), soaked in the same water for 1.5 hours, and then drained to obtain 33.9 g of absorbed rice. The 33.9 g of absorbed rice was placed in a plastic bag on a tray and heated with normal pressure steam until the product temperature reached 95°C, after which it was heated for 15 minutes to obtain 33.9 g of primarily heated rice. A mixture of 3.27 g of potassium lactate (50% solution; Musashino Chemical Laboratory, Slack® K), 0.56 g of trehalose (Hayashibara, Treha), 0.08 g of vitamin E emulsion (30% solution; Ogawa Fragrance, Emix E-30), and 63.7 g of water was added to the resulting primarily heated rice, mixed, and heated with normal pressure steam until the product temperature reached 95°C, after which it was heated for 30 minutes. The resulting second-cooked rice was washed with room-temperature water at approximately 20°C to remove any slime, then placed on a tray and slowly frozen at -7°C for 12 hours, then rapidly frozen at -40°C and freeze-dried. The dried product was coarsely crushed and granulated to obtain freeze-dried cooked rice. The amount of lactic acid contained in the freeze-dried cooked rice was measured by HPLC analysis, and the amount of potassium was measured by atomic absorption spectrometry. The reconstitution of the freeze-dried cooked rice and the flavor of the reconstituted cooked rice were also evaluated. The results are shown in Table 1.

[0026] (Examples 1 to 5, Comparative Example 2) Freeze-dried rice was obtained in the same manner as in Comparative Example 1, except that the amount of potassium lactate (50% solution) added was changed to the amount described in Table 1. The results of the analysis and evaluation are shown in Table 1.

[0027] (Comparative Example 3) Freeze-dried rice was obtained in the same manner as in Comparative Example 1, except that potassium lactate (50% solution) was not added. The results of the analysis and evaluation are shown in Table 1.

[0028] (Examples 6-8) Freeze-dried rice was obtained in the same manner as in Comparative Example 1, except that potassium lactate was replaced with sodium lactate (50% solution; manufactured by Musashino Chemical Laboratory Co., Ltd., Slack (registered trademark)), and the amount added was the amount described in Table 2. The results of the analysis and evaluation are shown in Table 2.

[0029] (Example 9) Freeze-dried rice was obtained in the same manner as in Example 3, except that trehalose and vitamin E emulsion (30% solution) were not used. The results of the evaluation of the rehydration of the freeze-dried rice and the flavor of the rehydrated rice were the same as in Example 3 (rehydration: ◎, flavor: 〇).

[0030] <HPLC Conditions> An appropriate amount was collected from 1.2 g to 2.0 g of freeze-dried rice, 20 mL of 0.5% perchloric acid was added, and extraction was performed by shaking for 10 minutes. The solution after extraction was filtered, diluted, and a part was subjected to HPLC. All the instruments used for HPLC were manufactured by Shimadzu Corporation, the model was LC-20AD, the detector was an electrical conductivity meter CDD-10A VP , and a column of Shim-pack SCR-102H×2, φ8.0 mm×300 mm was used. The column temperature was 45°C, the mobile phase was 5 mmol / L p-toluenesulfonic acid, the reaction solution was 5 mmol / L p-toluenesulfonic acid containing 0.1 mmol / L EDTA and 20 mmol / L Bis-Tris, and the flow rate was 0.8 mL / min for both the mobile phase and the reaction solution.

[0031] <Atomic Absorption Spectrophotometry Analysis Conditions> For potassium measurements, an appropriate amount of freeze-dried cooked rice was extracted from between 0.5 and 1.5 g, 200 mL of 1% hydrochloric acid was added, and the rice was shaken for 30 minutes and then left overnight. The extracted solution was filtered and diluted 1 to 10 times with 1% hydrochloric acid. A portion was then used for measurement. The atomic absorption spectrophotometric analysis was performed using an Agilent Technologies AA240FS instrument with a hollow cathode lamp as the light source. The flame was acetylene at 1.60 L / min, air at 14.00 L / min, and the measurement wavelength was 766.5 nm. For sodium measurements, the procedure was the same as for potassium measurements, except that an appropriate amount of freeze-dried cooked rice was extracted from between 1.0 and 2.5 g, and the measurement wavelength was 589.0 nm.

[0032] <Resilience> 50g of freeze-dried cooked rice was mixed with 100mL of hot water at 90-100℃, stirred thoroughly, then covered and left for 3 or 5 minutes before evaluating the reconstitution. The symbols in the table have the following meanings: ◎: Restored in 3 minutes, 〇: Restored in 5 minutes, △: Slight core remains, ×: Not restored

[0033] <flavor> 50g of freeze-dried cooked rice was mixed with 100mL of hot water at 90-100℃, stirred thoroughly, then covered and left for 5 minutes before evaluating the flavor of the cooked rice. The symbols in the table have the following meanings: ◯: No problem, △: Slight discomfort, ×: Serious discomfort (The strange flavor is due to the metallic taste that comes from potassium lactate.)

[0034] [Table 1]

[0035] [Table 2] [Industrial Applicability]

[0036] The freeze-dried cooked rice of the present invention can be reconstituted in a short time of within 5 minutes, preferably within 3 minutes, and has an excellent taste after reconstitution. Furthermore, the obtained freeze-dried cooked rice contains lactic acid or a salt thereof but is substantially free of sodium chloride, so that even when served as plain rice, the flavor can be enjoyed without being disturbed by a salty taste. The freeze-dried cooked rice of the present invention can be provided as an emergency food for disaster prevention (stockpiling) or as a convenient, portable meal.

Claims

1. Freeze-dried cooked rice containing lactic acid or a salt thereof in an amount of 0.5 g or more and less than 3 g in terms of lactic acid value per 100 g of freeze-dried cooked rice.

2. The freeze-dried cooked rice according to claim 1, wherein the lactic acid or a salt thereof is potassium lactate.

3. The freeze-dried cooked rice according to claim 1 or 2, further comprising at least one food additive selected from the group consisting of antioxidants and preservatives.

4. The freeze-dried cooked rice according to any one of claims 1 to 3, wherein the cooked rice is white rice and does not contain sodium chloride.

5. The freeze-dried cooked rice according to any one of claims 1 to 3, further comprising a seasoning.

6. A method for producing freeze-dried cooked rice containing lactic acid or a salt thereof, (a) a step of soaking raw material rice in water and then heating it to obtain primarily heated rice; (b) adding 0.5 g to 4 g of lactic acid or a salt thereof in terms of lactic acid per 100 g of raw material rice to the first-heated rice, then heating the rice to obtain second-heated rice, and washing the second-heated rice with water at 40°C or lower to remove slime from the surface of the cooked rice; (c) A step of freeze-drying the second-heated rice to obtain freeze-dried cooked rice A manufacturing method comprising:

7. The method according to claim 6, wherein the lactic acid or a salt thereof is potassium lactate.

8. The method according to claim 6 or 7, wherein step (c) is a step of slowly freezing the secondarily heated rice, further rapidly freezing it, and freeze-drying it.

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