JPH07147917A - Production of cooked rice having increased water content - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the palatability of cooked rice left for a long period at a relatively low temperature after cooking by treating rice grains with a transglutaminase before or after cooking. CONSTITUTION:Grains of polished or unpolished rice are treated with a transglutaminase before or after cooking. The deterioration of the palatability of the cooked rice can be prevented even by leaving the cooked rice at a relatively low temperature (e.g.; at <=20 deg.C) for about 24-36hr before eating. The transglutaminase is effective for suppressing the flow-out of starch paste from cooked rice having high water-content and keeping the palatability of the cooked rice.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyhydrated rice. More specifically, the present invention relates to a method for suppressing deterioration in the taste of cooked rice that has been manufactured and stored at a relatively low temperature by cooking rice with polyhydric water.

[0002]

2. Description of the Related Art In recent years, convenience stores (CV
S) and bento boxes and side dishes sold in supermarkets are increasing year by year. Also, with regard to rice, various types of rice such as white rice, brown rice, and cooked rice are intensively cooked at one place and delivered to each user, which has been industrialized. And a part of such rice is
It is processed into bento, rice balls, and sushi and eaten by consumers.

For example, in the case of bentos sold at CVS or the like, the rice cooked at the rice cooking center in advance is transferred to a bento factory, processed into bento or onigiri, and then delivered to each store. There is. As a result, the rice cooked at the rice cooking center will be eaten by consumers only after about 12 to 36 hours have passed.

Generally, these processed cooked rice products (including bento and white rice) are delivered at about 20 ° C. in order to prevent deterioration of the rice and further suppress microbial growth as much as possible. However, although this temperature is not within a temperature range that causes extreme deterioration of starch, the deterioration of starch is definitely progressing, and it has been required to suppress the deterioration of rice.

Also, for bento (including rice balls and sushi) to be taken home, cooked rice is often eaten after a lapse of time without immediately eating it, thus suppressing deterioration of the taste of cold rice. Was required.

[0006] Conventionally, as an additive for improving the taste of rice, an enzyme preparation mainly containing an enzyme such as amylase system, protease, papain, diastase, lipase, etc.,
Formulations of food grade emulsifiers such as glycerin fatty acid esters, edible oils, salt, sugars, chlorella extracts, and various seasonings are commercially available.

However, although the effects of these preparations can be recognized immediately after cooking rice or in a short time after keeping warm, when they are stored at a low temperature, for example, 20 ° C. or lower, the sustainability of the effects is insufficient and satisfactory. No effect was obtained.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made earnest studies to suppress the deterioration of the texture of cooked rice after cooking for a long time at a relatively low temperature, for example, a temperature of 20 ° C. or lower. As a result, transglutaminase, which is an enzyme widely distributed in the natural world, is allowed to act on rice grains before or during rice cooking, and the amount of water added during rice cooking is higher than that of general rice, that is, after the rice is washed. It has been found that cooking with 1.5 times or more the amount of rice water, preferably 1.5 to 2.0 times the amount of rice water suppresses the deterioration of the taste of rice over time, and the present invention is based on this finding. Completed

Therefore, according to the present invention, from rice cooking to eating, the temperature is relatively low in the temperature range of, for example, 20 ° C. or lower, and is 24 to 24 ° C.
It shows a method for producing cooked rice in which deterioration of texture caused by starch derived from cooked rice is suppressed even after being held for about 36 hours.

[0010]

The inventor of the present invention has made earnest studies for a solution to the above problems. As a result, when cooking rice, add transglutaminase to the immersion water to make the rice absorb water, or the cooking water, or the rice itself,
Furthermore, the amount of water is 1.5 times the amount of raw rice after washing,
The present invention was completed by cooking rice with preferably 1.5 to 2.0 times the amount of water.

The present invention is advantageously applied to cooked rice, so-called glutinous rice, but the application of the present invention is not limited to this glutinous rice. Hereinafter, the present invention will be described in detail.

[0012] Normally, the rice cooked for various business uses a continuous rice cooker having a strong heating power. These rice cookers
Although the heat source is gas or steam, the gas type continuous rice cooking equipment is generally widespread.

When rice is cooked in a continuous rice cooker regardless of the type of heat source, the washed rice is soaked in water, then an appropriate amount of cooking water is added, and then the rice is cooked. Cooled and used for various bento, rice balls and sushi.

At this time, the rice soaking, the amount of cooking water, and the steaming conditions are important factors that greatly affect the taste of rice. Among them, many researchers have reported that the amount of cooking water is closely related to the degree of gelatinization that influences the texture of rice, and the amount of cooking water during cooking greatly affects the quality of rice. This is a known fact. Cooking water here means
It refers to the water used when rice is cooked. For example, there is a case in which a part of this cooking water is used in advance as immersion water for raw rice. Further, in some cases, fresh rice may be soaked in advance, then drained, and then new cooking water is added again. In the latter case, in the present invention, the amount of cooking water obtained by subtracting the amount of water absorbed by the rice when the raw rice is soaked in water is added.
That is, when cooking rice, adjust the amount of water added to the weight of raw rice by 1.5 to 2.0 times. In addition, when washing rice, about 10% of the weight of raw rice is absorbed, but the present invention is premised on water absorption by washing raw rice.

[0015] Normally, the cooking conditions of the glutinous rice, which is the staple food of the Japanese people, cannot be decided unconditionally because each individual has his or her own preference. For example, New Food Industry Vol.31, No.
In 6, 65-79 (1989), the amount of water added to rice after washing was
It is generally said that the weight of rice is 1.5 times the weight of rice, and the Journal of the Food Industry Society of Japan, Vol. 32, No. 6, 386-390.
(1985) describes that in Koshihikari produced in Niigata prefecture, the amount of water added is 1.2 times the weight of raw rice after washing, which is the optimum amount of water for the taste.

However, the Journal of the Japanese Association for Home Economics Vol.38 No.7 567
~ 575 (1987), Home Economics Magazine, Vol.31 No.8 568 ~ 573
In literature such as (1980), the rice cooking method is direct cooking with gas rice,
Electric rice cookers Regardless of the difference in cooked rice, when rice is cooked with approximately 1.3 to 1.4 times the amount of raw rice,
It is reported that rice, which is relatively popular, tends to be cooked.

It is also understood from those documents that although the taste of rice has a great difference among individuals, more water, that is, about 1.4 times more water than the weight of raw rice, tends to deteriorate the texture. Is also possible.

Further, even in the patent for the quality improving agent for cooked rice, the rice cooking conditions of cooked rice described in the examples are often 1.3 to 1.4 times as much as water.

For example, in Japanese Patent Laid-Open No. 5-153242, No. 3
All of the examples described are 1.4 times water-added, and most of the examples described in Japanese Patent Laid-Open No. 4-66065 are rice cooked by 1.3 times water-added. .

From this, it can be judged that the amount of water added during rice cooking is 1.3 to 1.4 times the weight of rice, which is suitable for rice cooking conditions of non-glutinous rice, which is the staple food of Japanese.

Usually, the water content of cooked rice prepared by adding 1.3 to 1.4 times the amount of fresh rice is the water content previously contained in the rice.
And when considering the moisture that evaporates during cooking and cooling,
It will be around 56-61%.

For example, the water content of bento rice sold at convenience stores and the like, or the rice sold separately, is about 58 to 61% even after the vacuum cooling process after production, which is a Japanese preference. It can be seen that the rice is cooked according to the watering conditions.

Further, cooked rice containing more water than this has a markedly deteriorated taste, and it is natural that it is not manufactured especially as commercial cooked rice due to softening of rice grains and poor separation from the kettle. At present, various types of cooked rice are cooked under these circumstances, but the present invention is obviously characterized by cooking with more water than the conventional cooking method.

That is, currently, cooked rice for business and /
Alternatively, in other rice cooking facilities, rice is cooked under the above-described watering conditions, that is, 1.3 to 1.5 times the amount of water added to the weight of fresh rice after washing, whereas in the present invention, 1.5 times or more water, preferably water. It is characterized by cooking with 1.5 to 2.0 times the amount of water.

As a patent for the action of transglutaminase on rice, there is JP-A-5-15324. However, the invention is a method of improving the flavor of cereals, mainly rice, that is, the use of transglutaminase in rice only for the purpose of reducing foreign flavors such as old rice odor, bran odor, and barley odor. Have fundamentally different purposes.

[0026] If further added, Japanese Patent Laid-Open No. 5-15324
In the gazette, most of the examples are in accordance with the method for producing retort cooked cooked rice and aseptic filled cooked rice, and also in the cooked rice method of cooked rice used for those retort cooked rice and sterile cooked rice, the amount of water is the rice weight. This is about 1.4 times that of the present invention.

In the present invention, by increasing the amount of water added during rice cooking, the gelatinization of starch can proceed sufficiently and smoothly under all rice cooking conditions, and as a result, during low temperature storage, for example, at a temperature of 20 ° C. or lower. The purpose of the present invention is to provide a method for suppressing the deterioration of starch for about 24 to 48 hours, and it is not expected to reduce the off-flavor of rice.

That is, the role of transglutaminase in the present invention is to suppress the outflow of starch paste that occurs when rice is cooked in a condition where the amount of water added is large, and to maintain the texture of cooked rice.

For example, under general rice cooking conditions, soaking is carried out at a temperature of about 15 to 30 ° C. for about 30 to 90 minutes, and the effect of the present invention is sufficient under these conditions.

Further, when the liquid temperature at the time of soaking in water was raised to about 40 ° C., the effect of the method of the present invention was further enhanced.

When transglutaminase was allowed to act during immersion in water, the effect of the method of the present invention was recognized when the water temperature was in the range of 5 to 50 ° C.

A sufficient effect was observed even if transglutaminase was added to the rice cooking liquid used for rice cooking after the rice was soaked in water. At that time, it was confirmed that the cooking water was heated to about 30 to 45 ° C., preferably about 40 ° C. in advance, and transglutaminase was added before use, and a better effect was recognized.

The effect is exhibited by contacting the transglutaminase with rice during or before cooking rice. Therefore, for example, transglutaminase, which is attached to the surface of rice grains using a solvent such as water,
The same effect can be observed even if rice is cooked according to the above-mentioned rice cooking method. Currently, most commercial cooked rice is produced by a continuous rice cooker using a gas heat source. However, according to the method of the present invention, basically, when rice is cooked or before it is contacted with and absorbed by transglutaminase, and
It suffices to cook rice with a water amount of 1.5 times or more, and the effect of the method of the present invention can be recognized if the rice cooker is capable of performing the process.

For example, as the type of rice cooker, an electric rice cooker (round type for general household, three-dimensional rice cooker for business use), a gas rice cooker (round type for general household use, three-dimensional rice cooker for business use, etc.), continuous rice cooker Examples include a cooker (gas type cooker, round type, steam type continuous rice cooking line), pressure cooker cooked rice, etc. Although the amount of water evaporated during cooking may vary depending on the type of rice cooker, the method of the present invention Is not significantly affected.

Although the heating power of these rice cookers varies depending on the type of each device, generally, if the heating power is such that rice can be cooked, the effect of the method of the present invention can be sufficiently exerted.

It is known that a continuous rice cooker for cooked cooked rice has a higher heat power than an electric rice cooker in a general household and can cook delicious rice. However, the method of the present invention is used in such a rice cooker. It can exert a sufficient effect even when it is not used.

When transglutaminase is used, depending on the type of dipping water for soaking and the water for cooking rice and PH,
It is not particularly limited.

For example, in commercial cooked rice, the water used for dipping rice or cooking rice is generally clean water. However, recently, in order to improve the taste of rice, alkaline electrolyzed water,
There are cases in which so-called food water such as magnetized water (magnetic water), ionized water, degassed water, highly purified water, high-frequency low-voltage treated water, and low mineral water is used.

Since the effect of transglutaminase in the method of the present invention is an enzymatic action on rice protein, it is basically not affected by the difference in the types of water. However, due to the characteristics of the enzyme, the pH of water used for dipping or cooking water is preferably about 5-8.

The transglutaminase used in the method of the present invention may be either extracted from the liver of animals or the like or produced by culturing using a microorganism without any problem.

For example, Japanese Patent Application Laid-Open No. 58-149645 is known as an animal-derived transglutaminase, and Japanese Patent Application No. 62-125067 is known as a microbial-derived transglutaminase. However, since the extract enzyme derived from animal is very expensive, it is desirable to use the transglutaminase derived from microorganism for application to foods. When these transglutaminases are used, calcium or the like may be required to be used in combination depending on the characteristics. In addition, since the activity of transglutaminase is alienated by metal ions such as Cu ²⁺ and Zn ²⁺ (Japanese Patent Laid-Open No. 2-186961), caution is required in using the product of the present invention.

The role of transglutaminase in the method of the present invention is to catalyze the transfer of an α-amino group in a peptide to another amino acid in a protein contained in about 10% of rice to form a peptide bridge. Is to suppress the elution of starch paste. Therefore, in proteins in rice, it is possible to suppress deterioration of rice due to starch origin by the same principle as when an enzyme that catalyzes these phenomena is present other than transglutaminase.

In the method of the present invention, the method of adding transglutaminase during the rice soaking or immediately before cooking is relatively easy to work, and the addition amount is 0.1 u relative to the weight of raw rice.
The effect was confirmed when (unit) / g or more was added.

These effects in the present invention are also found in foreign rice such as sticky rice and other indica rice, and are not particularly affected by the type and shape of rice, the content ratio of amylose and amylopectin.

Further, in the present invention, for the purpose of further enhancing the effect of the present invention, a component which has been conventionally used in expectation of an improving effect on rice, for example, an enzyme such as cellulase or diastase is used as a main component. Enzyme preparations, glycerin fatty acid esters, sucrose fatty acid esters and other food emulsifiers, edible oils, salt, sugars, inorganic salts, chlorella extract and the like, in combination within the range of enhancing the effect of the present invention, particularly There is no problem.

The rice cooked with transglutaminase as described above is heated at 90 ° C. for 15 minutes or more by cooking rice, and the activity of the cooked rice is deactivated. .

The cooked rice produced according to the present invention is
The water content of cooked rice is higher than that of cooked rice produced by normal addition, that is, so-called 1.2 to 1.5 times addition of water, and its confirmation can be confirmed by measuring the water content of cooked rice.

[0048]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

(Example 1) 400 g of commercially available Koshihikari was washed with water, drained and then immersed in a predetermined amount of a transglutaminase solution (liquid temperature 40 ° C.) of 50 u / g based on the weight of raw rice. After dipping treatment for 60 minutes in a 40 ° C. incubator, rice was cooked together with dipping rice and dipping water in a rice cooker ECJ-U3R manufactured by Sanyo Electric Co., Ltd. Then, after 30 minutes of unevenness, it was rapidly cooled to 20 ° C. and stored at 10 ° C. for 24 hours, and a sensory test was conducted. For comparison, an example of cooked rice cooked by the conventional method is also shown. Furthermore, in order to more specifically express the effect of the present invention, the cutting force of cooked cooked rice grains was measured with a rheometer J type manufactured by Fudo Kogyo Co., Ltd. These results are shown in Table 1.
It was shown to.

Sensory test evaluation "deterioration degree of starch" ○: Not deteriorated No deterioration of starch is felt △: Slightly deteriorated Allowable deterioration of starch compared to immediately after cooked rice x: Degraded "Delicious texture of rice" where a clear deterioration of starch is felt A: Favorable texture Favorable texture of rice grains B: Slightly favorable texture Graininess of rice is a little weak, but acceptable. Bad texture There is no graininess in rice and it is weak and sticky

[0051]

[Table 1]

From Table 1, by increasing the amount of water added during rice cooking, the deterioration of starch during storage at 10 ° C. for 24 hours can be suppressed. In other words, cooked rice cooked with a water content of 1.3 times has a starch degrading phenomenon due to increased cutting power of cooked rice grains after being stored at 10 ° C for 24 hours. Also, increase the amount of water when cooking rice,
That is, when the rice was cooked at 1.5 times the weight of the washed raw rice, no significant change was observed in the cutting force after 24 hours at 10 ° C, and the deterioration of starch was suppressed. However, sensoryly, the texture of rice was weak and the stickiness due to the outflow of starch paste was observed, and the commercial value was low.
On the other hand, the cooked rice cooked with the method of the present invention at a water content of 1.5 times or more has a firm rice grain even when the water content is 1.5 times or more, and the starch paste does not flow out much It was a thing. Furthermore, since the amount of water added was large, almost no deterioration of starch was observed.

(Example 2) 400 g of a commercial sasanishiki was washed with water and drained, and then a predetermined amount of immersion water (adjusted to be 1.35 or 1.6 times the weight of fresh rice. Water temperature 25
Soak for 90 minutes. After that, the rice was cooked with a rice cooker GK-15L-A (P) manufactured by Matsushita Sumitomo Kikai Co., Ltd. together with immersion water, and after 30 minutes of unevenness, it was rapidly cooled to 20 ° C and stored at 10 ° C for 24 hours. . For comparison, an example of cooked rice cooked by the conventional method is also shown. The sensory test was performed by the method according to Example 1. Furthermore, for concrete expression, the stress relaxation of cooked cooked rice grains was measured with a rheometer J type manufactured by Fudo Kogyo Co., Ltd. The results are shown in Table 2.

[0054]

[Table 2]

The cooked rice cooked at a water content of 1.35 times, which is a general condition for cooking rice, had a good texture immediately after cooking and cooling, and had a grainy rice grain and no sticky feeling. But,
After storage at 10 ° C for 24 hours, deterioration of starch was observed both in texture and stress relaxation value. On the other hand, cooked rice cooked with 1.6 times water using the method of the present invention,
Even after storage at 10 ° C for 24 hours, there was no change in the stress relaxation value and no deterioration of starch was observed. Furthermore, the cooked rice produced by the method of the present invention has a large amount of water,
The texture was good with no deterioration in texture due to the starch paste flowing out.

(Example 3) 200 g of domestic glutinous rice was washed with water, drained and then immersed in a predetermined amount of a transglutaminase solution (liquid temperature 30 ° C.) of 75 u / g based on the weight of raw rice. After dipping for 1 hour in a 30 ° C incubator, drain water and steam for 45 minutes. Then 90 ℃
Dip into 193 g of syrup (160 parts of water, 30 parts of sugar, 3 parts of salt) that has been heated up to, mix and steam for 1 hour. By this method, a rice cooked for Ohagi was made on a trial basis, and its texture was evaluated.
The sensory test was carried out according to. In addition, as a comparison target,
An example of cooked rice prepared by the conventional method is also described. Further, in order to more specifically express the effect of the present invention, the cutting force and the stress relaxation of cooked cooked rice grains were measured with a rheometer J type manufactured by Fudo Kogyo Co., Ltd. The results are shown in Table 3.

[0057]

[Table 3]

The cooked rice for rice cooked by the method of the present invention is
There was little damage to the rice grains when the syrup absorbed water, and the texture was good with the grains themselves being solid. In the physical property change by the rheometer, the rice cooked for the ohagi prepared by the method of the present invention has a large change in stress relaxation as compared with that normally prepared, but the cutting force tends to increase,
A correlation with texture was confirmed.

Example 4 200 g of domestic glutinous rice was washed with water, drained, and then immersed in a predetermined amount of 100 u / g transglutaminase solution (liquid temperature 30 ° C.) based on the weight of raw rice. After soaking in a 10 ° C incubator for 24 hours, drain the water and boil for 45 minutes. After that, a sensory test was performed according to Example 3 and a cutting force and stress relaxation of the prepared cooked rice grains were measured by a rheometer. The results are shown in Table 4.

[0060]

[Table 4]

Similar to Example 3, the rice cake for rice cake made by using the method of the present invention is more stable than the rice rice for rice cake made by the ordinary method in texture and rheometer. The results were found to be possible.

(Example 5) 400 g of commercially available Indica rice was washed with water and drained, and then immersed in a predetermined amount of a transglutaminase solution (liquid temperature 40 ° C) of 40 u / g based on the weight of raw rice. After dipping for 90 minutes in a 40 ° C. incubator, rice was cooked with dipping water in a rice cooker ECJ-U3R manufactured by Sanyo Electric Co., Ltd. Then, after unevenly shaving for 30 minutes, it was rapidly cooled to 20 ° C. and stored at 5 ° C. and 10 ° C. for 24 hours, and then a sensory test was conducted. For comparison, an example of cooked rice cooked by a method not using the method of the present invention is also shown. The sensory test was performed by the method according to Example 1. Furthermore, in order to more specifically express the effect of the present invention, the cutting force of cooked cooked rice grains was measured with a rheometer J type manufactured by Fudo Kogyo Co., Ltd. The results are shown in Table 5.

[0063]

[Table 5]

Indica rice cooked by the method of the present invention is
Compared to cooked rice with a normal amount of water (about 1.1 to 1.3 times the raw weight of Indica rice), the texture is not inferior,
Furthermore, the deterioration phenomenon of starch during low temperature storage was also suppressed.

(Example 6) 400 g of commercially available Koshihikari was washed with water and drained, and then immersed in a predetermined amount of a transglutaminase solution (liquid temperature 40 ° C) of 30 u / g based on the weight of raw rice. After dipping for 90 minutes in a 40 ° C. incubator, rice was cooked together with dipping rice and dipping water in a rice cooker ECJ-U3R manufactured by Sanyo Electric Co., Ltd. Then, the mixture was spotted for 30 minutes, then rapidly cooled to 20 ° C and stored at 5 ° C for 24 hours. Then, the prototype sample was ranged up with a microwave oven RE-S750 manufactured by Sharp Corporation and a sensory test was performed. For comparison, an example of cooked rice cooked by the conventional method is also shown. further,
In order to more specifically express the effect of the method of the present invention, the stress relaxation of cooked cooked rice grains was measured with a rheometer J type manufactured by Fudo Kogyo Co., Ltd. The results are shown in Table 6.

[0066]

[Table 6]

The cooked rice produced by the method of the present invention was found to have an effect of suppressing deterioration of cooked rice at 5 ° C. storage as compared with cooked rice produced by normal addition (1.35 times). Furthermore, 5
When the cooked rice stored at ℃ is ranged up, the cooked rice according to the method of the present invention immediately returns to an edible state, and compared to cooked rice usually cooked with water, the cooked-up texture is shorter and the texture immediately after cooking is improved. I was able to recover.

Example 7 400 g of commercially available brown rice was washed with water and drained, and then immersed in a predetermined amount of a transglutaminase solution (liquid temperature 40 ° C.) of 10 u / g based on the weight of raw rice. In a 40 ° C incubator
After dipping for 45 minutes, rice was cooked with dipping water in a commercial pressure cooker. After that, stir for 30 minutes and then rapidly cool to 20 ℃ and
After storing at 10 ° C. for 24 hours, a sensory test was performed. For comparison, an example of cooked rice cooked by the conventional method is also described. The sensory test was performed by the method according to Example 1. Further, in order to more specifically express the effect of the method of the present invention, the cutting force of cooked cooked rice grains was measured with a rheometer J type manufactured by Fudo Kogyo Co., Ltd. The results are shown in Table 7.

[0069]

[Table 7]

Brown rice cooked by the method of the present invention did not deteriorate in texture as compared with cooked rice cooked with a normal amount of water, and the deterioration phenomenon of starch during storage at low temperature was suppressed. In addition to this example, studies were conducted on various types of glutinous rice, sticky rice, brown rice, etc. In all cases, the same results as these examples were obtained.

[0071]

EFFECTS OF THE INVENTION The cooked rice cooked by the method of the present invention can prevent the deterioration of starch that occurs during low temperature storage or low temperature distribution, and can lower the distribution temperature of processed foods using cooked rice.

Claims (3)

[Claims] 1. An additive such as a transglutaminase is added to a rice dipping solution or a rice cooking solution when the rice or brown rice is cooked.
Alternatively, a method for producing multi-hydrated cooked rice, which comprises adding rice to rice grains to cook the rice. 2. A method for improving the taste of cooked rice, which comprises cooking or steaming rice or brown rice in the presence of an additive comprising transglutaminase. 3. A method for suppressing the deterioration of the taste of cooked rice stored at a relatively low temperature after cooking, which comprises cooking rice or brown rice in polyhydrated rice in the presence of an additive comprising transglutaminase.