Cooked-rice improver and method of producing cooked rice

Abstract

A cooked rice improver, which allows fat and oil to be easily emulsified immediately after being added, is excellent in the effect of releasing cooked rice, reduces the breakage of rice grains and makes the graininess of rice excellent, suppresses aging of cooked rice, and allows cooked rice with improved richness and an excellent flavor to be obtained, is provided. The present invention provides a cooked rice improver containing fat and oil, an ionic surfactant, and a polyhydric alcohol, wherein a content of the fat and oil is 8% by mass or more and 65% by mass or less with respect to a total amount of the cooked rice improver, and a difference of L2 value - Ll value calculated at 20°C according to the following definition is positive: Ll value: lightness value of cooked rice improver; L2 value: lightness value of emulsion obtained by adding 100 times by mass of fresh water to the cooked rice improver.

Description

Cooked rice improver and method for producing cooked rice

[0001] The present invention relates to a cooked rice improving agent and a method for producing cooked rice. In particular, the present invention relates to a cooked rice improving agent containing an oil or fat, an ionic surfactant, and a polyhydric alcohol, and a method for producing cooked rice.

[0002] Supermarkets, convenience stores, and other retailers sell cooked rice in a variety of forms. For example, cooked rice is sold in containers as a staple food in boxed lunches, or in clear plastic containers packed with just the cooked rice for same-day consumption. Most of this cooked rice is eaten as is, or heated in a microwave oven as needed, but because it can easily be used to make other rice dishes such as fried rice, omelet rice, and rice porridge, its sales have been increasing in recent years for both home and commercial use.

[0003] Commercially available cooked rice is cooked in large quantities using machinery, resulting in a decrease in production yield if starch paste or rice grains adhere to the machinery. Therefore, it is common to add rice cooking oil containing an emulsifier as a release agent to raw rice and water before preparing the rice. However, in large rice cookers, the oil does not spread evenly throughout the rice, resulting in unevenness. To address this issue, thorough stirring after adding the rice cooking oil as a release agent has been used to eliminate this unevenness. However, stirring tends to increase the amount of broken rice, leading to a deterioration in the quality of the cooked rice. Another technique involves adding water to the rice cooking oil immediately before preparation and emulsifying it through mechanical stirring to improve dispersibility, but this requires specialized machinery and is not widely applicable. Furthermore, to address the above issue, it has been proposed to prepare a pre-emulsified rice additive emulsion as a release agent and use it during the preparation process (see Patent Documents 1 and 2).

[0004] JP-A-6-197711 JP-A-7-163306

[0005] The oil-in-water emulsions for adding cooked rice as described in Patent Documents 1 and 2 are prone to oxidative deterioration of the oils and fats. Therefore, even if the emulsions are filled in hermetically sealed containers during distribution, it takes several hours to several days from opening the container until they are used to cook rice, which still poses a problem of causing unpleasant odors in cooked rice due to oxidative deterioration of the oils and fats.

[0006] Therefore, an object of the present invention is to provide a cooked rice improving agent which is not a pre-emulsified oil-in-water type but can easily emulsify oils and fats immediately after addition, has an excellent releasing effect on cooked rice, reduces crumbling of rice grains and improves grain standing, inhibits aging, and further improves body and flavor to obtain cooked rice with good flavor.

[0007] As a result of thorough investigation into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by blending a cooked rice improving agent with a fat or oil, an ionic surfactant, and a polyhydric alcohol, and further adjusting the fat or oil content and adjusting the difference in brightness between the cooked rice improving agent and its emulsion. Based on these findings, the present inventors have completed the present invention.

[0008] That is, according to one aspect of the present invention, there is provided a cooked rice improving agent containing an oil or fat, an ionic surfactant, and a polyhydric alcohol, wherein the content of the oil or fat is 8% by mass or more and 65% by mass or less relative to the total amount of the cooked rice improving agent, and wherein the L2 value - L1 value calculated by the following method at 20°C is positive: L1 value: brightness value of the cooked rice improving agent; L2 value: brightness value of an emulsion obtained by adding 100 times by mass of fresh water to the cooked rice improving agent.

[0009] In one embodiment of the present invention, the viscosity of the cooked rice improving agent at 20°C is preferably 50,000 mPa·s or less.

[0010] In one embodiment of the present invention, the water content is preferably 5% by mass or more and 30% by mass or less based on the total amount of the cooked rice improving agent.

[0011] In this aspect of the present invention, the polyhydric alcohol preferably contains glycerin and / or a sugar alcohol.

[0012] In one aspect of the present invention, the content of the polyhydric alcohol is preferably 20% by mass or more in terms of solid content based on the total amount of the cooked rice improving agent.

[0013] In this aspect of the present invention, the ionic surfactant preferably comprises a lysophospholipid.

[0014] In one aspect of the present invention, the content of the ionic surfactant is preferably 0.1% by mass or more and 10% by mass or less relative to the total amount of the cooked rice improving agent.

[0015] In one embodiment of the present invention, the L2 value - L1 value is preferably 10.0 or more.

[0016] According to another aspect of the present invention, there is provided a method for producing cooked rice, comprising the step of adding a mixture containing a fat or oil, an ionic surfactant, and a polyhydric alcohol, wherein the fat or oil content is 8% by mass or more and 65% by mass or less relative to the total amount of the mixture, and wherein the L2 value - L1 value calculated by the following method at 20°C is positive: L1 value: brightness value of the mixture L2 value: brightness value of the emulsion obtained by adding 100 times the mass of fresh water to the mixture

[0017] According to the present invention, it is possible to provide a cooked rice improving agent which can easily emulsify oils and fats immediately after addition, has an excellent releasing effect on cooked rice, reduces crumbling of rice grains and improves grain standing, inhibits aging, and further improves body and flavor to obtain cooked rice with good flavor.

[0018] Generally, adding oil as a release agent is undesirable in terms of the flavor of cooked rice, and in particular, emulsified rice cooking oils, due to their oil-in-water (O / W) nature, have a high water content, which means that the amount of water added to the cooked rice must be adjusted according to the amount added, which tends to make on-site work complicated. The cooked rice improving agent of the present invention can adjust the water content lower than conventional cooked rice improving agents, and can be effective even with small amounts used. Therefore, there is almost no water carried into the pot during cooking, and there is no need to adjust the amount of water added during cooking, which improves workability.

[0019] <Rice improving agent> The cooked rice improving agent of the present invention contains at least an oil or fat, an ionic surfactant, and a polyhydric alcohol, and can improve the quality of cooked rice and workability during production. In the present invention, the quality of cooked rice refers to the graininess, prevention of aging, and flavor of the cooked rice, and the workability during cooked rice production refers to the ease of emulsification of oil or fat, the release properties of the cooked rice, etc.

[0020] (Cooked rice) In the present invention, cooked rice includes not only cooked rice obtained by cooking white rice or brown rice, but also barley rice obtained by cooking white rice together with barley, and steamed sticky rice obtained by cooking or steaming polished glutinous rice. Cooked rice also includes various types of seasoned rice, fried rice, porridge, brown rice, vinegared rice, red rice, cooked rice with ingredients such as chestnuts or beans, retort rice, and aseptically packaged cooked rice. Cooked rice also includes rice distributed and sold at room temperature, refrigerated, or frozen.

[0021] (L value) The cooked rice improving agent has the property that, when the L value, which represents the color brightness, is measured using a colorimetric color difference meter at 20°C, the difference between the brightness L1 value of the cooked rice improving agent and the brightness L2 value obtained by adding 100 times the mass of fresh water to the cooked rice improving agent (L2 value - L1 value) is positive.

[0022] The L value is a numerical value that represents the brightness of a color, with a larger value indicating a brighter color. In the case of an emulsion, the finer the emulsion particles, the greater the amount of scattered light, making the emulsion whitish, and therefore the larger the L value. The change in the L value in the present invention occurs because a phase transition occurs when the cooked rice improving agent is added to water, and the oil and fat become finely particled emulsion, which becomes cloudy and loses transparency. In the present invention, the L value can be measured using a colorimetric color difference meter (trade name "Color Meter ZE-2000": manufactured by Nippon Denshoku Industries Co., Ltd.).

[0023] The property of oils and fats easily becoming finely divided into an emulsified state (O / W emulsion) by adding water is called "self-emulsifying property." The cooked rice improving agent of the present invention maintains the state before self-emulsifying to form an O / W emulsion by adding it to water. Self-emulsifying property is a characteristic observed in systems in which infinite associations of molecules are formed, such as liquid crystals and bicontinuous microemulsions (BCMEs) in which surfactants are infinitely associated, and the stability of the system is proportional to the level of self-emulsifying property. Although the details of the structure of the cooked rice improving agent of the present invention are not clear, since it exhibits self-emulsifying property upon addition of water, it is presumed to be a system in which infinite associations are formed or a system in a similar state. The cooked rice improving agent of the present invention can easily emulsify oils and fats immediately after addition, thereby improving workability in the manufacturing process. Furthermore, since the cooked rice improving agent of the present invention does not require prior emulsification, it can also prevent oxidative deterioration of oils and fats.

[0024] If the self-emulsifying ability of the cooked rice improving agent of the present invention is high, the size of the fat particles in the O / W emulsion obtained when a large amount of water is added also becomes smaller, resulting in a larger L2 value. Since the level of self-emulsifying ability is proportional to the stability of the cooked rice improving agent as described above, the L2 value represents the stability of the cooked rice improving agent. Therefore, the greater the difference (L2 value - L1 value) between the L1 value of the cooked rice improving agent (before water is added) and the L2 value of the emulsion obtained by adding 100 times the mass of water to the cooked rice improving agent, the more stably the cooked rice improving agent maintains its structure and can easily emulsify fats and oils immediately after addition. Furthermore, in the present invention, although the detailed principle is unknown, it is presumed that the fat particles in the resulting O / W emulsion are small and easily penetrate into cooked rice, which reduces the crumbling of rice grains and improves graininess, inhibits aging, and furthermore, improves the body and flavor of cooked rice without a noticeable oily smell.

[0025] In the present invention, the L2 value - L1 value of the cooked rice improving agent is positive, preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. If the L2 value - L1 value of the cooked rice improving agent is positive, oils and fats can be easily emulsified immediately after adding the cooked rice improving agent, and cooked rice with improved body and good flavor can be obtained without imparting an oily smell due to oxidation to the cooked rice. On the other hand, if the L2 value - L1 value is negative, the anti-aging effect cannot be obtained and the oily smell will be strongly perceived.

[0026] (Viscosity of cooked rice improving agent) The viscosity of the cooked rice improving agent at 20°C is 50,000 mPa·s or less, preferably 30,000 mPa·s or less, more preferably 10,000 mPa·s or less, even more preferably 5,000 mPa·s or less, and preferably 100 mPa·s or more, more preferably 500 mPa·s or more, and even more preferably 1,000 mPa·s or more. If the viscosity of the cooked rice improving agent is within the above range, oils and fats can be easily emulsified immediately after adding the cooked rice improving agent, further improving workability. The viscosity of the cooked rice improving agent was measured using a BL-type viscometer at a product temperature of 20°C and a rotation speed of 6 rpm, when the viscosity was less than 3,000 mPa·s: rotor No. 2, and when the viscosity was 3,000 mPa·s or more but less than 5,000 mPa·s: rotor No. 3. When the viscosity is 5,5000 mPa·s or more: Rotor No. 4 is used, and the value is calculated from the reading 3 minutes after the start of measurement.

[0027] (Oils and Fats) The oils and fats to be incorporated into the cooked rice improving agent are not particularly limited, and conventionally known edible oils and fats can be used. Specific examples of edible oils and fats that can be used include vegetable oils such as rapeseed oil, soybean oil, corn oil, palm oil, cottonseed oil, sunflower oil, safflower oil, sesame oil, olive oil, linseed oil, rice bran oil, camellia oil, perilla oil, grapeseed oil, peanut oil, almond oil, and avocado oil; fish oil, DHA-containing algae oil, beef tallow, lard, chicken fat; and oils and fats obtained by chemical or enzymatic treatment, such as MCT (medium-chain triglyceride), diglyceride, hardened oil, and interesterified oil. Furthermore, from a health perspective, it is more preferable for these natural oils and fats to contain phytochemicals (vitamin K, vitamin D, tocopherol, tocotrienol, γ-oryzanol, polyphenols, etc.). Among these, vegetable oils are preferably used, and rice oil, rapeseed oil, soybean oil, corn oil, or a mixture thereof is more preferably used. The cooked rice improving agent of the present invention is also effective in that these oils can be easily added to cooked rice, and fat-soluble functional ingredients can be added to cooked rice, or oils that are susceptible to oxidative deterioration can be added to cooked rice without oxidative deterioration until just before addition.

[0028] The content of fats and oils is 8% by mass or more and 65% by mass or less, preferably 10% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less, based on the total amount of the cooked rice improving agent. If the content of fats and oils is within the above numerical range, the fats and oils can be easily emulsified immediately after adding the cooked rice improving agent, the cooked rice has an excellent release effect, the rice grains are less likely to crumble and have good graininess, aging is suppressed, and cooked rice with an improved body and good flavor can be obtained. On the other hand, if the content is below the lower limit, the release effect is not sufficiently excellent. Furthermore, if the content is above the upper limit, a stable emulsion cannot be obtained or the fats and oils cannot be easily emulsified immediately after addition.

[0029] (Ionic surfactants) The ionic surfactants incorporated into the cooked rice improving agent are those which, when dissolved in water, ionize to generate ions, and there are three types: anionic surfactants, cationic surfactants, and zwitterionic surfactants. In the present invention, at least one ionic surfactant selected from the above-mentioned three types of ionic surfactants is contained. In addition, the ionic surfactant may be of any origin, whether natural, synthetic, or semi-synthetic.

[0030] Examples of anionic surfactants include organic acid monoglycerides in which an organic acid (such as acetic acid, lactic acid, citric acid, succinic acid, or diacetyltartaric acid) is further bonded to the hydroxyl group of a monoglyceride; perfluorocarboxylic acids or their salts; alkyl sulfates such as sodium dodecyl sulfate and ammonium lauryl sulfate; phosphatidylinositol; and phosphatidylglycerol. Examples of cationic surfactants include quaternary ammonium salts such as benzalkonium chloride and benzethonium chloride. Examples of amphoteric surfactants include alkyl betaines such as stearyl betaine and lauryl betaine; alkyl amine oxides such as lauryl dimethylamine oxide; phospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine; and lysophospholipids obtained by lysozylation of these. Emulsifying materials having a similar effect to surfactants are also included in the category of surfactants.

[0031] In the present invention, when a zwitterionic surfactant is used among the three types of surfactants, the cooked rice improving agent is easily emulsified, and staling of cooked rice can be more effectively suppressed. A zwitterionic surfactant is a surfactant whose ionicity changes depending on the pH; when the hydrophilic group is negatively charged, it exhibits the properties of an anionic surfactant, and when the hydrophilic group is positively charged, it exhibits the properties of a cationic surfactant. In other words, when preparing the cooked rice improving agent of the present invention, it always acts as an ionic surfactant regardless of the ionicity of its blended components, and is likely to form the cooked rice improving agent of the present invention with self-emulsifying properties. Furthermore, when water is added to this to obtain a self-emulsified product, it is not affected by the coexistence of ionic components other than water (salts, etc.), and a fine and stable O / W emulsion can be obtained.

[0032] The fatty acids constituting the zwitterionic surfactant used in the present invention are preferably saturated, from the viewpoint of more effectively suppressing oxidation of fats and oils. When the fatty acids constituting the zwitterionic surfactant are saturated, the surfactant itself is less susceptible to oxidation. Furthermore, it is presumed that the unsaturated fatty acid portions of the blended fats and oils are mixed at the molecular level in a system in which infinite aggregates are formed or in a similar state, thereby achieving an effect of suppressing the chain reaction of autoxidation.

[0033] The saturated fatty acids constituting the zwitterionic surfactant are preferably 40% or more, more preferably 65% ​​or more, in mass ratio relative to the total fatty acids constituting the fatty acids, from the viewpoint of easily forming an emulsified state of the cooked rice improving agent and more effectively suppressing aging of cooked rice.

[0034] In the present invention, from the viewpoint of easily forming an emulsified state of the cooked rice improving agent and more effectively inhibiting cooked rice aging, it is preferable to use phospholipids among the zwitterionic surfactants. Phospholipids are lipids containing phosphate esters and phosphonate esters, and are amphipathic substances having both hydrophilic and hydrophobic groups. Phospholipids include glycerophospholipids with a glycerol skeleton, such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol, and sphingophospholipids with a sphingosine skeleton, such as sphingoemyl. Among phospholipids, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol are preferred, and mixtures containing these phospholipids, such as various lecithins, are preferred. Examples of lecithins include plant lecithins such as soybean lecithin, rapeseed lecithin, and sunflower lecithin, as well as egg yolk lecithin. Plant lecithins are preferred because they are derived from plants. When a mixture containing phospholipids is used, the phospholipid portion contained therein corresponds to the ionic surfactant of the present invention. For example, when egg yolk lecithin (PL-30, LPL-20S: manufactured by Kewpie Corporation, etc.) is used, the phospholipid contained in the mixture corresponds to the ionic surfactant of the present invention, and the egg yolk oil portion corresponds to the oil or fat of the present invention.

[0035] (Lysophospholipid) In the present invention, aging can be more effectively suppressed by using a lysophospholipid obtained by lyso-modifying the above-mentioned phospholipid. As the lysophospholipid, for example, lysophosphatidylcholine, lysophosphatidylethanolamine, or lysophosphatidylinositol is preferably used.

[0036] The content of the ionic surfactant is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.3% by mass or more and 8% by mass or less, and even more preferably 0.5% by mass or more and 5% by mass or less, relative to the total amount of the cooked rice improving agent. If the content of the ionic surfactant is within the above range, oils and fats can be easily emulsified immediately after adding the cooked rice improving agent, and the anti-aging effect of cooked rice can be improved.

[0037] (Polyhydric Alcohol) The polyhydric alcohol incorporated into the cooked rice improving agent is a general term for alcohols having two or more hydroxy groups in the molecule, and examples thereof include glycerin, ethylene glycol, propylene glycol, or polymers thereof; alkanediols such as 1,3-butanediol, 1,4-butanediol, and 1,2-propanediol; and sugar alcohols such as maltitol, lactitol, sorbitol, xylitol, erythritol, reduced palatinose, and reduced starch syrup. Among these, glycerin and sugar alcohols are preferred, and sugar alcohols are more preferred. Furthermore, the average molecular weight of the sugar alcohol is preferably 100 to 2,000, more preferably 150 to 1,000. In the present invention, the use of a polyhydric alcohol makes it possible to easily emulsify oils and fats immediately after adding the cooked rice improving agent, provides excellent release effects for cooked rice, reduces crumbling of rice grains and improves grain structure, inhibits aging, and further improves body and flavor to produce cooked rice.

[0038] The polyhydric alcohol may be used in powder form or in liquid form. When a liquid form is used, the content of the polyhydric alcohol is calculated as solid content. The content of the polyhydric alcohol is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, still more preferably 35% by mass or more, and also preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or more, calculated as solid content, relative to the total amount of the cooked rice improving agent. If the content of the polyhydric alcohol is within the above numerical range, the oil and fat can be emulsified more easily immediately after adding the cooked rice improving agent, the cooked rice can have an excellent release effect, the rice grains can be less crumbled and have good grain structure, aging can be further suppressed, and cooked rice with an improved body and good flavor can be obtained.

[0039] (Moisture content) The cooked rice improving agent may contain moisture for emulsification and viscosity adjustment. When the cooked rice improving agent contains moisture, it may contain fresh water or may be derived from a water-containing raw material such as liquid sugar containing water as a polyhydric alcohol.

[0040] The moisture content is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 22% by mass or less, relative to the total amount of the cooked rice improving agent. It may be 0% by mass or more, but may also be 5% by mass or more, or 10% by mass or more. By adjusting the moisture content to the upper limit or less, almost no moisture is carried into the rice cooker during cooking, eliminating the need to adjust the amount of water added during cooking, thereby improving workability. Furthermore, by adjusting the moisture content to the lower limit or more, the viscosity can be adjusted low, and as a result, the oil or fat can be easily emulsified immediately after addition, further improving workability.

[0041] (Other Ingredients) In addition to the ingredients described above, the cooked rice improving agent can be blended with various ingredients that are commonly used in cooked rice improving agents, as long as the effects of the present invention are not impaired. Examples of other ingredients include organic acids such as acetic acid and citric acid, amino acids, salt, sweeteners, thickeners, coloring agents, flavoring agents, preservatives, etc.

[0042] (Method for preparing cooked rice improving agent) The method for preparing the cooked rice improving agent is not particularly limited, and can be carried out by a conventionally known method. For example, the cooked rice improving agent can be prepared by charging an ionic surfactant, a polyhydric alcohol, fresh water, and, if necessary, other ingredients such as salt or a sweetener into a stirring tank, stirring and mixing using a mixer to make the mixture homogeneous, and then gradually adding edible oils and fats while stirring.

[0043] (Production Equipment) Equipment commonly used in food production can be used to prepare the cooked rice improving agent of the present invention. Examples of such equipment include general mixers, stick mixers, stand mixers, homomixers, homodispersers, etc. Examples of the shape of the mixing blades of the mixer include propeller blades, turbine blades, paddle blades, anchor blades, etc.

[0044] <Method for Producing Cooked Rice> The method for producing cooked rice of the present invention includes a step of adding a mixture containing at least an oil or fat, an ionic surfactant, and a polyhydric alcohol. The mixture can have the same composition as the cooked rice improving agent of the present invention described in detail above. The method for adding the mixture to rice and the method for cooking the rice are not particularly limited, and can be any of the conventionally known methods. Furthermore, the timing for adding the mixture to rice is not particularly limited, and the mixture may be added before, simultaneously with, or after cooking the rice.

[0045] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention should not be construed as being limited to the contents of the following examples.

[0046] [Examples 1 to 7, Comparative Examples 1 to 4] <Preparation of cooked rice improving agents> Cooked rice improving agents were prepared according to the blending ratios shown in Table 1. Specifically, a polyhydric alcohol (sugar alcohol (average molecular weight of 150 to 1000) or glycerin), an ionic surfactant (lysophospholipid), and water were added to a glass beaker, and the mixture was stirred and mixed with a propeller stirrer equipped with an anchor to achieve a uniform mixture. Thereafter, edible oil (rapeseed oil, etc.) was gradually added while continuing to stir, to prepare the cooked rice improving agent.

[0047] Comparative Example 5 A commercially available cooked rice improving agent (oil-in-water emulsion containing vegetable oil, polyhydric alcohol, emulsifier (soybean-derived) and the like as main ingredients) was used.

[0048] <Evaluation of Cooked Rice Improving Agents> (Measurement of L Value) Using the above cooked rice improving agent, the L value of each sample was measured three times at 20°C using the method described below, before and after dilution with water, and the average value was used to calculate the L2 value - L1 value. The results are shown in Tables 1 and 2. Note that for Comparative Examples 2 and 3, where the cooked rice improving agent separated immediately after production and could not be measured, it is indicated as "not measured" ("-") in Table 1. [Measurement Device] Colorimetric Color Difference System (Color Meter ZE-2000, manufactured by Nippon Denshoku Industries Co., Ltd.) [Measurement Conditions] L1 value: Lightness value of cooked rice improving agent 1.5 g of cooked rice improving agent before dilution with water was placed in a circular cell and subjected to measurement. L2 value: Lightness value of emulsion obtained by adding 100 times the mass of fresh water to the cooked rice improving agent 0.2 g of the cooked rice improving agent before dilution was placed in a beaker, and 20.0 g of fresh water was added and stirred. 1.5 g of the obtained water-diluted sample was placed in a circular cell and subjected to measurement.

[0049] (Viscosity Measurement) For the above cooked rice improving agents, a BL-type viscometer was used at a product temperature of 20°C and a rotation speed of 6 rpm. When the viscosity was less than 3000 mPa·s, rotor No. 2 was used; when it was 3000 mPa·s or more but less than 5000 mPa·s, rotor No. 3 was used; and when it was 5000 mPa·s or more, rotor No. 4 was used. The viscosity (mPa·s) was calculated from the reading 3 minutes after the start of measurement. For each cooked rice improving agent, viscosity measurements were performed three times and the average value was used. The measurement results are shown in Tables 1 and 2. Note that Comparative Examples 2 and 3, in which the cooked rice improving agent separated immediately after production and could not be measured, are indicated in Table 1 as not measured ("-").

[0050] <Production of Cooked Rice> 450 g of raw rice was thoroughly washed and soaked in water for 60 minutes to allow sufficient water absorption. Next, the soaked rice was drained and placed in a commercially available rice cooker, and water was added so that the total weight of the soaked rice and water was 1150 g. Next, 14 g of the above-mentioned cooked rice improving agent was added, and after light stirring, the rice was cooked. After cooking, the cooked rice was removed from the cooker and cooled to 25°C in a vacuum cooler.

[0051] (Ease of emulsification) The ease of emulsification (workability) when added during rice cooking as described above was evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2. The following evaluations can be considered to be good results if the evaluation is "◎", "◯", or "△". Note that for Comparative Examples 2 and 3, where the cooked rice improving agent separated immediately after production and could not be measured, it is shown as "-" (not measured) in Table 1. [Evaluation criteria for the ease of emulsification of cooked rice improving agents] ◎: Simply stirring with a rice scoop immediately after addition resulted in a uniform milky white color after a few seconds. ○: Simply stirring with a rice scoop immediately after addition resulted in a uniform milky white color after about 10 seconds. △: Although it was briefly stirred with a rice scoop immediately after addition, it took some time to achieve uniformity, but this did not pose any practical problems. ×: Although it was vigorously stirred with a rice scoop immediately after addition, it was not completely uniform even after a while, and lumps remained.

[0052] (Releaseability) Regarding the release ability of the cooked rice as described above, after cooking, the rice cooker was turned over and the cooked rice was removed, and then the rice grains and rice starch paste remaining on the bottom of the rice cooker were visually inspected and evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2. The following evaluations can be considered to have been good results if the evaluation was "◎" or "◯". Note that for Comparative Examples 2 and 3, where the cooked rice improving agent separated immediately after production and could not be measured, it is shown as "-" (not measured) in Table 1. [Evaluation criteria for cooked rice release ability] ◎: The rice released easily from the rice cooker, with no rice grains or starch paste remaining. ○: The rice released easily from the rice cooker, with a small amount of starch paste remaining but no rice grains remaining. ×: The rice did not release from the rice cooker, with rice grains remaining.

[0053] (Sensory Evaluation) The cooked rice was subjected to a sensory evaluation of the graininess, anti-aging effect, and flavor of the cooked rice according to the following criteria by several trained panelists. The control group refers to cooked rice cooked in the same manner as above, but without adding the cooked rice improving agent. The evaluation results are shown in Tables 1 and 2. The following evaluations, when rated as "◎", "◯", or "△", are considered to be good results. Note that for Comparative Examples 2 and 3, where the cooked rice improving agent separated immediately after production and could not be measured, it is shown as "-" (not measured) in Table 1. [Evaluation criteria for cooked rice graininess] ◎: The rice grains were well-defined, and had a very satisfactory texture for cooked rice. ○: The rice grains were well-defined, and had a satisfactory texture for cooked rice. ×: The rice grains were poorly defined, and the rice grains were brittle, resulting in an unsatisfactory texture for cooked rice. [Evaluation criteria for anti-aging effect of cooked rice] ○: Staling was prevented, and the rice was moderately sticky and elastic. ×: Staling occurred, and the texture was lacking in stickiness and crumbly. [Evaluation criteria for cooked rice flavor] ◎: Compared to the control group, the richness was significantly increased. ○: Compared to the control group, the richness was increased. △: Compared to the control group, the richness was slightly increased, or a slight oily smell was felt. ×: Compared to the control group, the richness was not increased at all, or a strong oily smell was felt.

[0054]

[0055]

[0056] All of the cooked rice improving agents of Examples 1 to 7 were easily emulsified immediately after addition, had an excellent cooked rice release effect, reduced rice grain crumbling and good graininess, inhibited aging, and furthermore, produced cooked rice with improved full-bodied taste and good flavor. Furthermore, among the Examples rated as "Excellent" for ease of emulsification, Example 3 was particularly easy to emulsify. In addition, Examples 1 to 4 had smooth physical properties and were excellent in ease of incorporation, and Examples 1 to 3 in particular were extremely excellent in ease of incorporation. The cooked rice improving agent of Comparative Example 1 had a poor release effect because the oil content was too low. The cooked rice improving agents of Comparative Examples 2 and 3 had too high an oil content, so they separated immediately after production. Therefore, subsequent evaluation could not be carried out. The cooked rice improving agent of Comparative Example 4 had an excessively high oil content, making it difficult to emulsify, and the cooked rice did not grain well, failing to inhibit aging. The cooked rice improving agent of Comparative Example 5 had a negative L2 value - L1 value, and therefore could not inhibit aging, and had a strong oily smell.

Claims

1. A cooked rice improving agent containing fats and oils, an ionic surfactant, and a polyhydric alcohol, characterized in that the fats and oils content is 8% by mass or more and 65% by mass or less relative to the total amount of the cooked rice improving agent, and the L2 value minus L1 value calculated by the following method at 20°C is positive: L1 value: brightness value of the cooked rice improving agent; L2 value: brightness value of the emulsion obtained by adding 100 times the mass of fresh water to the cooked rice improving agent.

2. The cooked rice improving agent according to claim 1, characterized in that the viscosity at 20°C is 50,000 mPa·s or less.

3. A cooked rice improving agent according to claim 1 or 2, characterized in that the moisture content is 5% by mass or more and 30% by mass or less based on the total amount of the cooked rice improving agent.

4. The cooked rice improving agent according to any one of claims 1 to 3, characterized in that the polyhydric alcohol contains glycerin and / or a sugar alcohol.

5. A cooked rice improving agent according to any one of claims 1 to 4, characterized in that the content of the polyhydric alcohol is 20 mass% or more, calculated as solid content, based on the total amount of the cooked rice improving agent.

6. The cooked rice improving agent according to any one of claims 1 to 5, characterized in that the ionic surfactant contains a lysophospholipid.

7. A cooked rice improving agent according to any one of claims 1 to 6, characterized in that the content of the ionic surfactant is 0.1 mass % or more and 10 mass % or less relative to the total amount of the cooked rice improving agent.

8. The cooked rice improving agent according to any one of claims 1 to 7, characterized in that the L2 value - L1 value is 10.0 or more.

9. A method for producing cooked rice, comprising the step of adding a mixture containing an oil or fat, an ionic surfactant, and a polyhydric alcohol, wherein the content of the oil or fat is 8% by mass or more and 65% by mass or less relative to the total amount of the mixture, and the L2 value - L1 value calculated by the following method at 20°C is positive. L1 value: brightness value of the mixture L2 value: brightness value of the emulsion obtained by adding 100 times the mass of pure water to the mixture