A kind of potless steamed rice and its preparation method

Abstract

The present invention discloses a method for steaming rice without a cooking pot and its preparation method, belonging to the technical field of food processing. The present invention uses japonica rice as raw material, and is prepared through processes such as washing, soaking, enzymatic hydrolysis, draining, steaming, spraying, and infrared baking. The present invention develops a new method for preparing steamed rice, and based on this method, the enzymatic hydrolysis of protease is used to improve the taste, flavor, and anti-aging ability of the steamed rice. Compared with the traditional rice steaming process, the production process of the present invention saves the step of secondary soaking and water absorption during steaming, and has important application value for the process of producing steamed japonica rice on an integrated assembly line. The rice of the present invention has bright and uniform color, refreshing taste, and strong fragrance. Compared with the rice steamed by the traditional method, it has richer taste and texture, better eating quality, and is less likely to age and return to its original state.

Description

Technical Field

[0001] The present invention relates to a method for steaming rice without a cooking pot and its preparation method, belonging to the technical field of food processing. Background Art

[0002] As a major food crop in the world, rice is the staple food for more than half of the world's population. At present, the industrial production of rice in China faces problems such as low degree of continuity, low production efficiency, high energy consumption, and large differences in taste and nutritional quality requirements. In view of these problems, it is of great significance to optimize and improve the production process and taste quality.

[0003] At present, the process of steaming rice is divided into steaming with a cooking pot and steaming without a cooking pot. Steaming rice with a cooking pot is a traditional cooking method. Although it has the advantages of retaining nutrients and good texture, it has problems such as long cooking time, uneven rice taste, high energy consumption and high cost when used in industrial production. Steaming rice without a cooking pot can greatly improve production efficiency. Industrial equipment usually has a large capacity and can process a large amount of rice at the same time, thus meeting market demand faster. At present, some production lines for steaming rice without a cooking pot have been developed. For example, CN114041695A discloses a design of a steam rice production line, which solves problems such as low yield and complex structure of the rice production line. However, the rice produced by this production line often has problems such as excessive water content in the rice, no rice fragrance, and poor taste quality, resulting in serious deficiencies in economic benefits. Summary of the Invention

[0004] Technical Problem:

[0005] In view of the above-mentioned defects or deficiencies in the prior art, a preparation method for steaming rice without a cooking pot is provided. Compared with the steamed rice prepared by the traditional method, the rice prepared by this method has characteristics such as smoother taste and less prone to aging and regaining hardness. At the same time, the taste, fragrance and color of the rice are also good.

[0006] Technical Solution:

[0007] The first object of the present invention is to provide a preparation method for steaming rice without a cooking pot, comprising the following steps:

[0008] (1) Washing, soaking, and enzymatic hydrolysis: After washing and soaking japonica rice, protease is added for constant-temperature enzymatic hydrolysis;

[0009] (2) Steaming: After draining the water from the enzymatically hydrolyzed rice, it is spread out for steaming;

[0010] (3) Spraying: In the latter stage of steaming, hot water is simultaneously sprayed on the rice;

[0011] (4) Infrared baking: The sprayed rice is baked under infrared heating to finally obtain the finished rice product.

[0012] In one embodiment, the protease in step (1) is neutral protease, and the enzyme activity of the protease is 0.8 AU / g. The addition amount of neutral protease is 24 - 96 u / g compared to the addition amount of japonica rice.

[0013] In one embodiment, the implementation method of potless steaming is to add the method of high-temperature hot water spraying on the basis of steam heating, similar to the rice steaming production line disclosed in CN114041695A.

[0014] In one embodiment, the neutral protease in step (1) needs to be dissolved in hot water at 40 - 50 °C in advance and stirred evenly, and stored in a hot water environment at 40 - 50 °C.

[0015] In one embodiment, the enzymolysis temperature in step (1) is 30 - 50 °C, and the enzymolysis time is 60 - 120 min.

[0016] In one embodiment, the mass ratio of the soaking water to the rice in step (1) is 1:(1.3 - 1.7).

[0017] In one embodiment, after the rice is drained in step (2), it should be transferred to the steaming area within 5 minutes. The steaming area is a stainless steel filter screen with holes of 2 mm in diameter. The steaming device is in a closed environment, with a steam generation part at the bottom, and steam is introduced through a steam pipe or water is heated to boil to generate steam. The top of the device is a high-pressure spray head device, and high-temperature and high-pressure hot water is introduced.

[0018] In one embodiment, the steaming time in step (2) is 20 - 30 min.

[0019] In one embodiment, the temperature of the hot water sprayed in step (3) is 85 - 100 °C, the total spraying amount of the sprayed water is not less than the mass of the raw rice, the spraying time is 8 - 10 minutes before the end of steaming, and the end time is 1 - 2 minutes before the end of steaming. The unabsorbed water will flow through the holes of the filter screen into the recycling device for secondary use.

[0020] In one embodiment, the infrared heating temperature in step (4) is 150 - 170 °C, and the baking time is 2 - 3 min.

[0021] The second object of the present invention is to provide the rice prepared by the foregoing method.

[0022] The third object of the present invention is to provide the application of the foregoing rice in the food field.

[0023] Advantages and effects of the present invention:

[0024] (1) The present invention provides a method for preparing steamed rice without a cooking pot. By spraying hot water to promote the absorption and gelatinization of water by the rice, it replaces the secondary soaking process of the rice in the traditional method of steaming rice with a cooking pot. The simultaneous spraying and steaming effectively reduce the intermediate links in the production process of steamed rice, making the processing process more integrated. It is of great significance for the assembly-line production of steamed rice, reducing the production cost, and improving the automated production capacity of the production line.

[0025] (2) The present invention uses protease to enzymatically hydrolyze rice. Protease can partially decompose the peptide chains of protein molecules in rice into small-molecule polypeptides or amino acids, relieve the protein gel structure, break the natural film barrier formed by protein, reduce the protective effect of protein on starch, and promote the gelatinization of rice starch. At the same time, amino acids and short peptides produced by protein hydrolysis participate in the Maillard reaction during cooking to generate flavor compounds such as aldehydes, ketones, furans, and pyrazines, improving the aroma of the rice; the hydrolysis of protein also reduces the binding between protein and flavor substances formed by van der Waals forces, hydrogen bonds, and hydrophobic interactions, promoting the release of the aroma of the rice.

[0026] (3) During the infrared baking process, it can not only reduce the problem of excessive water content in the rice caused by the spraying process, but also promote the Maillard reaction of the rice, generating an aroma similar to that of rice cooked over firewood and enhancing the taste quality of the rice.

[0027] (4) By organically combining protease hydrolysis, spraying and steaming, and infrared baking, the prepared steamed rice has a hardness range of 11 - 11.5 kgf and a viscosity of 5.33 kgf. At the same time, the comprehensive sensory evaluation performance of the rice, such as taste, color, aroma, and flavor, is relatively excellent. The appearance and taste scores obtained by using a taste meter are also good. Compared with traditional steamed rice, the comprehensive quality is significantly improved and it is more popular. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a graph of the sensory analysis results of the steamed rice prepared in Examples 1 - 4 and Comparative Examples 1 - 4;

[0029] Figure 2 It is a graph of the taste meter score results of the steamed rice prepared in Examples 1 - 4 and Comparative Examples 1 - 4;

[0030] Figure 3 It is a graph of the analysis results of the anti-aging ability of the steamed rice prepared in Examples 1 - 4 and Comparative Example 1 by DSC (Differential Scanning Calorimetry); among them, the enzyme addition amounts in Examples 1 - 4 and Comparative Example 1 are 24 u / g, 48 u / g, 72 u / g, 96 u / g, and 0 u / g respectively. DETAILED DESCRIPTION OF THE INVENTION

[0031] The following further explains the present invention in conjunction with examples.

[0032] Direct sources of the enzymes involved in the examples and comparative examples:

[0033] Neutral protease: Neutrase 0.8L (0.8 AU / g), purchased from Novozymes;

[0034] Performance test methods:

[0035] 1. Texture measurement

[0036] The whole texture (hardness, viscosity, chewiness) characteristics of rice were analyzed using a texture analyzer (TPA): After the steamed rice was prepared, it was cooled at room temperature for 1 h for TPA measurement. Randomly select 3 grains of rice and arrange them in a radial pattern. Select a cylindrical P35 probe. The pre-test speed is 1.0 mm / s, the test speed is 0.5 mm / s, the post-test speed is 1.0 mm / s, the compression ratio is 70%, the sensing force is 0.049 N, and the interval time between two compressions is 5 s. Each sample was parallel 8 times, and the maximum and minimum values were removed before averaging the data.

[0037] 2. Sensory quality measurement

[0038] The sensory evaluation method was used to evaluate the rice: A sensory evaluation panel consisting of 6 trained people was formed. The prepared rice samples were placed in bowls with random numbers and presented to the members of the evaluation group randomly. Before tasting the samples, the assessors rinsed their mouths thoroughly with pure water. The nine-point hedonic method was used to analyze and evaluate the rice's aroma, taste, texture, color, shape and other indicators. The lowest score is 1 point (least liked), and the highest score is 9 points (most liked). The average value was taken as the experimental result.

[0039] 3. Measuring the quality of rice with a taste meter

[0040] The taste quality of rice was evaluated using a rice taste meter: The prepared steamed rice was cooled at room temperature for 100 min, 8.0 ± 0.1 g of rice was weighed, and a rice cake was made using a special steel ring of the taste meter as a mold. The taste quality indicators of the rice were measured using a rice taste meter, and each sample was measured three times.

[0041] 4. Measuring the anti-aging ability of rice with a differential scanning calorimeter

[0042] The aging degree of rice was evaluated using a differential scanning calorimeter: The prepared steamed rice was refrigerated at 4 °C for 14 days, freeze-dried and ground into powder. The thermal properties of the rice were measured using a differential scanning calorimeter. The scanning temperature range was 30 - 90 °C, and the heating rate was 10 °C / min. The scanning gas was nitrogen, and the protective gas was helium.

[0043] 5. Gas chromatography - mass spectrometry (Shimadzu GC-2030) analysis of flavor substances in rice

[0044] First, age the solid-phase microextraction head in the injection port of the gas chromatograph for 2 h at an aging temperature of 250 °C. Take 2 g of the cake samples of the comparative example and the examples and place them in a 20 mL sample vial. Cover the vial with a rubber cap, place the sample vial in a 60 °C water bath, gently insert the extraction head into the sample vial, push out the fiber head, and ensure that the extraction head does not touch the cake. Adsorb for 50 min, then withdraw the fiber head, remove the extraction head from the sample vial, insert the extraction head into the injection port of the gas chromatograph again, push out the fiber head, and desorb at 250 °C for 10 min.

[0045] Chromatographic conditions: The carrier gas is high-purity He, splitless injection, constant pressure of 35 kPa, injection port temperature of 250 °C. Temperature program: Hold at 35 °C for 2 min, increase to 60 °C at a rate of 5 °C / min, hold for 3 min, increase to 140 °C at a rate of 8 °C / min, and then increase to 180 °C at a rate of 3 °C / min. Mass spectrometry conditions: MS quadrupole temperature of 150 °C, ionization mode EI, electron energy of 70 eV, ion source temperature of 230 °C, mass scanning range m / z of 35 - 450. Each sample is measured three times.

[0046] Example 1:

[0047] A preparation method of potless steamed rice, comprising the following steps:

[0048] (1) Material selection: Select fresh and plump japonica rice, remove impurities and sift out broken rice, and then wash it three times.

[0049] (2) Soaking and enzymatic hydrolysis: Soak the selected japonica rice in water at 50 °C with a rice-to-water mass ratio of 1:1.5 (kg / kg) to allow the rice to fully absorb water; add neutral protease to the soaking water, where the enzyme activity of the protease is 0.8 AU / g, and the addition amount of neutral protease relative to japonica rice is 24 u / g, denoted as 24 u / g. The japonica rice is soaked in the enzyme-containing soaking water for 90 min.

[0050] (3) Steaming: After soaking, drain the japonica rice and spread it flat on a net with holes of 2 cm diameter and steam for 25 min.

[0051] (4) Spraying: Start spraying hot water at 90 °C evenly on the steaming japonica rice 8 min before the end of steaming, with the total spraying water amount not less than the mass of the raw rice, to allow it to fully absorb water and gelatinize, and stop spraying 2 min before the end of steaming.

[0052] (5) Infrared baking: Bake the rice after spraying at 150 °C under infrared heating for 3 min to finally obtain the finished rice product.

[0053] Example 2:

[0054] Except for changing the addition amount of neutral protease in step (2) to 48 u / g, other steps and parameters are the same as those in Example 1, and finally the finished rice product is obtained.

[0055] Example 3:

[0056] Except for changing the addition amount of neutral protease in step (2) to 72 u / g, other steps and parameters are the same as those in Example 1, and finally the finished rice product is obtained.

[0057] Example 4:

[0058] Except for changing the addition amount of neutral protease in step (2) to 96 u / g, other steps and parameters are the same as those in Example 1, and finally the finished rice product is obtained.

[0059] Comparative Example 1:

[0060] Except for omitting the enzymatic hydrolysis treatment in step (2) and recording the enzyme addition amount as 0 u / g, other steps and parameters are the same as those in Example 1, and finally the finished rice product is obtained.

[0061] Comparative Example 2:

[0062] Except for omitting the spraying treatment process in step (4), other steps and parameters are the same as those in Example 1, and finally the finished rice product is obtained.

[0063] Comparative Example 3:

[0064] Except for continuously spraying during the whole process of steaming rice, other steps and parameters are the same as those in Example 1, and finally the finished rice product is obtained.

[0065] Comparative Example 4:

[0066] Except for omitting the infrared baking treatment in step (5), other steps and parameters are the same as those in Example 1, and finally the finished rice product is obtained.

[0067] Test Example 1:

[0068] The sensory evaluation was carried out on the finished rice products prepared in Examples 1-4 and Comparative Examples 1-4, and the results are as Figure 1 shown in Table 1.

[0069] Table 1: Sensory evaluation results of Examples 1-4 and Comparative Examples 1-4

[0070] Aroma Taste Mouthfeel Color and luster Shape Total score Example 1 7 7 7 7 6 34 Example 2 7 7 8 6 7 35 Example 3 8 9 9 7 8 41 Example 4 9 8 8 8 8 41 Comparative example 1 5 6 6 6 5 28 Comparative example 2 3 2 2 3 3 13 Comparative example 3 3 3 3 5 5 19 Comparative example 4 4 5 5 6 5 25

[0071] From Figure 1, it can be seen from Table 1 that the total sensory scores obtained by comprehensively considering indicators such as aroma, taste, texture, color, and shape are, from high to low, 96 u / g (total sensory evaluation score is 41) = 72 u / g (total sensory evaluation score is 41) > 24 u / g (total sensory evaluation score is 35) > 48 u / g (total sensory evaluation score is 34) > 0 u / g (total sensory evaluation score is 28). The comprehensive scores of the cooked rice prepared in Comparative Example 2, Comparative Example 3, and Comparative Example 4 are 13, 19, and 25 points respectively, and their eating quality is relatively poor. Among them, compared with Comparative Example 1 without enzyme soaking, the cooked rice prepared in Examples 1 - 4 with different addition amounts of protease showed certain improvements in aroma, taste, texture, color, and shape.

[0072] When the addition amount of neutral protease relative to rice reaches 72 u / g - 96 u / g, the comprehensive score of the cooked rice reaches the highest. The specific evaluation is as follows: compared with Comparative Example 1 with an enzyme addition amount of 0 u / g, when the enzyme addition amount is 96 u / g, the aroma score is 9 points, and the addition of the enzyme improves the aroma release of the cooked rice; the color score is 8 points, and the surface of the cooked rice is brighter and smoother, which is more attractive; the texture score is 8 points, slightly lower than the texture score of 9 points of the cooked rice prepared when the enzyme addition amount is 72 u / g, indicating that too high an enzyme addition amount leads to too low a hardness of the cooked rice, which is not conducive to the improvement of texture; the shape score is 8 points, and sufficient water absorption and gelatinization make the shape of the cooked rice more plump and appetizing; the taste score is 8 points, and the amino acids and short peptides produced by protein hydrolysis effectively improve the taste quality of the cooked rice. In Comparative Example 2, the cooked rice prepared without spraying has insufficient moisture and fails to be fully gelatinized, so the rice is undercooked; in Comparative Example 3, the cooked rice prepared with continuous spraying has too high a moisture content, and there is still a problem of overly soft texture after infrared baking; in Comparative Example 4, the cooked rice prepared without baking has too high a moisture content and insufficient aroma of the rice, indicating the necessity of a complete process.

[0073] Test Example 2:

[0074] Performance tests were carried out on the cooked rice products prepared in Examples 1 - 4 and Comparative Example 1, and the results are as Figure 2 shown in Table 2.

[0075] Table 2: Taste scores, appearance, and texture evaluation results of Examples 1 - 4 and Comparative Example 1

[0076] Taste score Appearance Mouthfeel Example 1 77 6.8 6.8 Example 2 76 7.0 7.0 Example 3 80 7.1 7.4 Example 4 80 7.0 7.2 Comparative example 1 56.5 4.8 5.0

[0077] Judging from the values of the taste meter, the taste scores of the edible rice prepared in Examples 1-4 and Comparative Example 1 were evaluated. The appearance, texture and taste values of the rice prepared in Examples 1-4 with neutral protease added during the soaking process all increased. The specific evaluation is as follows: the appearance score of the rice prepared in Comparative Example 1 was 4.8 points, the texture score was 5.0 points, and the taste score was 56.5 points; compared with Comparative Example 1, the appearance and texture scores of the rice prepared in Examples 1-4 were both around 7, and the taste scores were between 70 and 80 points. The taste score of the steamed rice prepared with a higher enzyme addition amount exceeded 80 points, reaching a quite high level. The texture score of the rice prepared with an enzyme addition amount of 96 u / g was slightly lower than that of the rice prepared with an enzyme addition amount of 72 u / g, which was also consistent with the results of sensory evaluation, indicating that the enzymatic hydrolysis of proteins allowed more water to enter the rice, making the rice softer. However, when the protein content in the rice was too low, the rice became mushy, lost its elasticity, and the texture deteriorated.

[0078] Test Example 3:

[0079] The texture of the cooked rice products prepared in Examples 1-4 and Comparative Examples 1-4 was measured, and the results are shown in Table 3.

[0080] Table 3: Texture measurement results of the steamed rice prepared in Examples 1-4 and Comparative Examples 1-4

[0081]

[0082]

[0083] As can be seen from Table 3, for the steamed rice prepared by enzymatic hydrolysis with neutral protease added during the soaking process, compared with Comparative Example 1, the hardness and chewiness of the rice decreased significantly. Combining the sensory evaluation results and the taste meter score results, for steamed rice, the optimal rice hardness range is 11-13 kgf, the chewiness range is 1080-1120, and the optimal viscosity range is 4.8-5.3 kgf. From the analysis of and Table 3, it is preferably obtained that the addition amount of neutral protease relative to rice is 72 u / g to 96 u / g. At this time, the comprehensive sensory evaluations such as aroma, taste, texture, color, and shape of the steamed rice are relatively good. Compared with the steamed rice prepared without protease enzymatic hydrolysis treatment, the comprehensive quality is significantly improved and it is more popular. Figure 1 the sensory evaluation results Figure 1 and Table 3 analysis, it is preferably obtained that the addition amount of neutral protease relative to rice is 72 u / g to 96 u / g. At this time, the comprehensive sensory evaluations such as aroma, taste, texture, color, and shape of the steamed rice are relatively good. Compared with the steamed rice prepared without protease enzymatic hydrolysis treatment, the comprehensive quality is significantly improved and it is more popular.

[0084] Test Example 4:

[0085] The anti-aging ability of the cooked rice products prepared in Examples 1-4 and Comparative Example 1 was measured by a scanning calorimeter, and the results are as Figure 3 shown.

[0086] FromFigure 3 It can be seen that, compared with Comparative Example 1, the aging situation of the rice prepared by adding neutral protease enzymolysis has been significantly improved. The starch in the rice gelatinizes during the cooking process and undergoes rearrangement of starch molecules, i.e., aging, at room temperature. The melting enthalpy of the crystals formed by aging can be obtained through DSC (Differential Scanning Calorimeter) analysis, and thus the aging degree of starch can be judged. Compared with the rice prepared in Comparative Example 1, the melting enthalpy of the crystals formed by aging of the rice prepared in Examples 1-4 decreases significantly under the same storage environment. When the enzyme addition amount is 96 u / g, the aging situation is the least obvious. It can be seen that adding neutral protease during the soaking process has a good technical effect on improving the anti-aging ability of rice.

[0087] Test Example 5:

[0088] The flavor substances in the finished rice products prepared in Examples 1-4, Comparative Example 1, and Comparative Example 4 were analyzed by gas chromatography-mass spectrometry (Shimadzu GC-2030), and the results are shown in Table 4.

[0089] Table 4

[0090]

[0091]

[0092] From the results of gas chromatography - mass spectrometry analysis, Table 4 reflects the content of flavor substances in the cooked rice of Examples 1 - 4, Comparative Example 1, and Comparative Example 4. It can be seen that compared with Comparative Example 1 and Comparative Example 4, after infrared baking and enzyme treatment, the types and contents of flavor substances in the rice significantly increase, and the rice emits a more abundant fragrance overall. Among them, 2 - acetylpyrroline has a strong popcorn flavor and can produce a relatively strong aroma at a low concentration. It is considered the most critical flavor substance in rice and can endow rice with sweetness. It can be seen that after treatment with protease at a certain concentration, the detected content of 2 - acetylpyrroline significantly increases. This may be attributed to the reduction of protein, which enhances the release of 2 - acetylpyrroline, thus making the rice emit a more attractive aroma. For aldehydes, which are the volatile flavor substances with the highest content, their flavor characteristics are mainly fruity and sweet at a low concentration, but excessive amounts will produce the smell of lipid oxidation and rancidity. As can be seen from the table, as the protease concentration increases, the degree of Maillard reaction increases. The content of some aldehydes with higher concentrations decreases as reaction substrates, reducing the generation of unpleasant odors. At the same time, the nutty and licorice - like aromas presented by octanal, benzaldehyde, etc. have the function of enhancing the fragrance and adjusting the color of the rice. The increase in the content of other heterocyclic substances such as 2 - pentylfuran also brings better flavor to the rice. Generally speaking, infrared baking has a very obvious effect on increasing the Maillard reaction, and the action of protease makes the aroma released by the rice more intense. At the same time, it has an obvious synergistic effect with the Maillard reaction, significantly improving the flavor of the rice and enhancing the quality of the rice. For those skilled in the art, unexpected technical effects have been achieved.

[0093] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various modifications and alterations without departing from the technology and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A preparation method for cooking rice without a cooking pot, characterized in that, It includes the following steps: (1) Washing, soaking, and enzymatic hydrolysis: After washing and soaking japonica rice, add protease for constant-temperature enzymatic hydrolysis; in step (1), the protease is neutral protease, the addition amount of neutral protease compared to the addition amount of japonica rice is 72 U / g, the enzymatic hydrolysis temperature is 50 °C, and the enzymatic hydrolysis time is 90 min; (2) Steaming: Drain the water from the enzymatically hydrolyzed rice and spread it out for steaming; (3) Spraying: Simultaneously spray hot water on the cooked rice in the later stage of steaming; in step (3), spraying is carried out during the steaming process, the total amount of sprayed water is not less than the mass of raw rice, the temperature of the sprayed hot water is 90 °C, the spraying start time is 8 min before the end of steaming, the spraying end time is 2 min before the end of steaming, and the unabsorbed water will flow into the recycling device through the holes of the filter screen for secondary utilization; (4) Infrared baking: Bake the steamed rice at 150 °C for 3 min by infrared heating to finally obtain the finished rice product.

2. The preparation method according to claim 1, wherein In step (2), the drained rice should be transferred to the steaming area within 5 min. The steaming area is a stainless-steel filter screen with holes of 2 mm in diameter. The steaming device is in a closed environment, with a steam generation part at the bottom, and steam is introduced through a steam pipe or water is heated to boiling to generate steam. The top of the device is a nozzle device through which high-temperature hot water is introduced.

3. The preparation method according to claim 1, characterized in that, In step (2), the steaming time is 20 - 30 min.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the soaking water to the rice is 1:(1.3 - 1.7).

5. The rice prepared by the method according to claims 1 - 4.

6. The application of the rice according to claim 5 in the food field.

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