A gamma-aminobutyric acid-enriched steamed glutinous rice and a preparation method thereof

Abstract

The application provides a gamma-aminobutyric acid-rich steamed glutinous rice and relates to the field of food processing. The application comprises the following steps: S1. pretreatment; S2. magnetic field induction: rice is treated in a 10-20 mT pulsed magnetic field at 25-35 DEG C for 30-120 min; S3. soaking: the rice treated in the magnetic field is soaked in a soaking liquid at 5-15 DEG C for 2-6 h, and then is soaked in a soaking liquid at 55-60 DEG C for 1-2 h; S4. ultrasonic-assisted germination: the soaked rice is placed in an ultrasonic environment with a frequency of 35-45 kHz and a power density of 0.3-0.8 W / cm 2 , and is subjected to ultrasonic induction germination at 28-32 DEG C for 24-48 h; when the length of the sprout reaches 1-3 mm, the germination is terminated, and vacuum freeze drying is carried out; S5. steaming; S6. shelling. Through the pretreatment of the magnetic field, low-temperature induction and ultrasonic-assisted germination, the germination rate of the rice is improved, and the generation and enrichment of gamma-aminobutyric acid are promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food processing, in particular, to a kind of rich γ-aminobutyric acid steamed rice and its preparation method. BACKGROUND

[0002] Rice is one of the staple foods in southern China. Rice is a typical seed of Gramineae, which is rich in nutrients, and different parts have different functions and nutrients:

[0003] Rice hull: Rice hull is the outermost protective structure of rice, accounting for about 18%-20% of the weight of rice. It is hard in texture and mainly composed of cellulose, lignin and silicon dioxide. The role of rice hull is to protect the embryo and endosperm inside from physical, chemical and biological factors, such as preventing insect and microbial erosion, and resisting mechanical damage during harvesting, transportation and storage.

[0004] Pericarp and seed coat: Pericarp is located inside the hull and developed from the ovary wall; seed coat is developed from the integument and wrapped inside the seed of rice. The two structures are closely connected and generally thin, containing some pigments, proteins and fats. They play a protective role and affect the appearance quality of rice such as color to some extent.

[0005] Aleuron layer: Aleuron layer is located between seed coat and endosperm and is composed of one or several layers of cells. It is rich in nutrients such as protein, fat, mineral and vitamin, and has high nutritional value. During the process of processing rice into rice, rice hull, pericarp, seed coat and aleuron layer will be removed through processing procedures such as hulling and milling.

[0006] Endosperm: Endosperm is the most important part of rice, accounting for about 70%-80% of the weight of rice. It is a place to store nutrients and mainly composed of starch, containing a small amount of protein and fat. Daily edible rice is mainly composed of endosperm. Nutrients in endosperm provide nutrients required for embryo development during rice germination.

[0007] Embryo: Embryo is located on one side of rice, accounting for only 2%-3% of the weight of rice, and is the core part of rice life activities. Embryo contains structures such as plumule, hypocotyl and radicle, and is rich in protein, fat, vitamin and enzymes. In the process of rice germination, enzymes in embryo play a key role and can decompose nutrients in endosperm to provide energy and material basis for the growth of seedling.

[0008] During the germination process of rice, a series of biochemical changes occur inside the grain. The internal starch begins to convert into sugars such as glucose. This conversion makes the germinated rice taste softer and sweeter compared to ungerminated rice. The proteins in the endosperm are broken down into amino acids and soluble proteins by enzymes. These substances provide more nitrogen sources and nutritional support for embryo development. During the germination process of rice, the activity of various enzymes such as amylase and protease increases. These enzymes play a key role in the germination process of rice, catalyzing various biochemical reactions and promoting the growth and development of rice. During the germination process of rice, the content of vitamins also changes. Some water-soluble vitamins such as vitamin B may increase, while some fat-soluble vitamins such as vitamin E may decrease due to oxidation.

[0009] Gamma-aminobutyric acid is an amino acid produced during the germination of rice. As an inhibitory neurotransmitter, it can improve brain function, nerve function, and long-term memory. In the prior art, brown rice is usually used as raw material to promote the production of gamma-aminobutyric acid through germination. However, the content of gamma-aminobutyric acid in the obtained rice product is still limited, which cannot meet the market demand. SUMMARY

[0010] The purpose of the present application is to provide a preparation method of gamma-aminobutyric acid-rich steamed rice, which improves the germination rate of rice and promotes the production and enrichment of gamma-aminobutyric acid through magnetic field pretreatment, low-temperature induction, and ultrasonic-assisted germination.

[0011] Another purpose of the present application is to provide a gamma-aminobutyric acid-rich steamed rice with a gamma-aminobutyric acid content of ≥50mg / 100g and a sprout length of ≤3mm, which is rich in nutrients.

[0012] The technical problem of the present application is solved by adopting the following technical solutions.

[0013] In one aspect, the present application provides a preparation method of gamma-aminobutyric acid-rich steamed rice, comprising the following steps:

[0014] S1. Pretreatment: The rice is sequentially subjected to impurity removal, disinfection, and cleaning treatment;

[0015] S2. Magnetic field induction: The rice is treated in a 10-20mT pulsed magnetic field at 25-35℃ for 30-120min;

[0016] S3. Soaking: The rice treated by the magnetic field is soaked in a soaking solution at 5-15℃ for 2-6h; and then soaked in a soaking solution at 55-60℃ for 1-2h;

[0017] S4. Ultrasonic assisted germination: the soaked rice is placed in an ultrasonic environment with a frequency of 35-45 kHz and a power density of 0.3-0.8 W / cm 2 , and ultrasonic induction germination is performed at 28-32℃ for 24-48h; when the length of the sprouts reaches 1-3mm, the germination is terminated, and vacuum freeze-drying is performed;

[0018] S5. Steaming: the rice treated in step S4 is steamed at 110-120℃ for 5-15min, and then air-dried;

[0019] S6. Hulling: the rice treated in step S5 is subjected to hulling and rice milling to obtain steamed rice.

[0020] In some embodiments of the present application, the soaking solution comprises the following raw materials by mass fraction: 0.01-0.1wt% glutamic acid decarboxylase, 0.05-0.2wt% calcium lactate or calcium gluconate, 0.1-0.5wt% calcium chloride, 0.05-0.2wt% vitamin B6, and the balance is water.

[0021] In some embodiments of the present application, in the step S4, the water content of the rice after vacuum freeze-drying is ≤12%.

[0022] In some embodiments of the present application, in the step S4, during the ultrasonic induction germination, dynamic gas regulation is further included: a mixed gas containing CO2, O2 and inert gas is introduced into the rice, wherein the volume fraction of CO2 is 5-10%, the volume fraction of O2 is 10-15%, and the balance is inert gas.

[0023] In some embodiments of the present application, the volume fraction of CO2 is maintained at 8-10% 24h before the germination of the rice, and the volume fraction of CO2 is reduced to 5-7% within 24h after the end of the germination. By controlling the content of CO2 in the environment, excessive respiration consumption is inhibited, and the accumulation rate of GABA is increased by more than 2 times.

[0024] In some embodiments of the present application, in the step S4, during the ultrasonic induction germination, a water solution with a concentration of 0.5-5mmol / L γ-aminobutyric acid, 0.1-1mmol / L trehalose and 0.5-2mmol / L proline is sprayed into the rice every 1-3h, and the spraying flow rate is 50-300mL / min. By spraying the water solution of γ-aminobutyric acid, the content of γ-aminobutyric acid in the rice is increased, and the trehalose and proline added in the spraying liquid form a molecular protective layer, which synergistically prevents the degradation of GABA during the spraying process, improves the enrichment efficiency of γ-aminobutyric acid, and the absorption rate of γ-aminobutyric acid is increased to 85% after spraying.

[0025] In some embodiments of the present application, the pulse magnetic field in step S2 is an alternating magnetic field with a frequency of 1-5 Hz and an angle of 30-60° between the magnetic field direction and the plane of the rice layer. The alternating magnetic field (10-20 mT) makes the cell membrane produce micropores, promotes the influx of Ca 2+

[0026] In some embodiments of the present application, the ultrasonic treatment in step S4 adopts an intermittent mode with an operation cycle of 5-10 min of ultrasonic treatment and 2-5 min of stopping. The intermittent ultrasonic treatment (35-45 kHz) enhances the substance transfer, and CO2 (5-10%) inhibits the mitochondrial respiratory chain and reduces the consumption of glutamic acid.

[0027] In some embodiments of the present application, the vacuum freeze-drying in step S4 includes two stages: a first stage of pre-freezing for 2-4 h at-30℃ to-40℃ and a second stage of drying for 12-24 h at a vacuum degree of 10-30 Pa and a temperature of-50℃ to-60℃. Through the two-stage freeze-drying, the pre-freezing at-40℃ can preserve the cell structure, and the vacuum sublimation can avoid the degradation of heat-sensitive components in the rice.

[0028] In another aspect, the embodiments of the present application provide a γ-aminobutyric acid-rich steamed rice made by the above method.

[0029] Compared with the prior art, the embodiments of the present application have at least the following advantages or beneficial effects:

[0030] The preparation method of the γ-aminobutyric acid-rich steamed rice provided by the present application combines pulse magnetic field, low-temperature soaking, and ultrasonic treatment to promote the germination of rice, improve the germination efficiency, promote the production of γ-aminobutyric acid in rice, and thus improve the content of γ-aminobutyric acid. Among them, the pulse magnetic field (10-20 mT) makes the cell membrane produce micropores, the low temperature (5-15℃) induces the expression of GAD enzyme, and the combination of the two makes the activity of GABA synthetase increase by more than 40%; the ultrasonic treatment (35-45 kHz) can promote the diffusion of metabolites. DETAILED DESCRIPTION

[0031] ​In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, the conventional products that can be purchased in the market are adopted.

[0032] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to specific embodiments.

[0033] The features and performances of the present application will be further described in detail below in combination with the embodiments.

[0034] Embodiment 1

[0035] The steamed glutinous rice in the present example is prepared in the following method.

[0036] S1. Pretreatment: the rice is sequentially subjected to impurity removal, disinfection and cleaning treatment;

[0037] S2. Magnetic field induction: the rice is treated in an alternating pulse magnetic field with a magnetic field strength of 10 mT and a frequency of 5 Hz for 100 min at 30℃, wherein the magnetic field direction forms an angle of 60° with the layer plane of the rice.

[0038] S3. Soaking: the rice treated by the magnetic field is soaked in a soaking liquid at 5℃ for 6 h, and then soaked in a soaking liquid at 58℃ for 2 h; the soaking liquid comprises the following raw materials in a mass fraction: 0.1wt% of glutamic acid decarboxylase, 0.2wt% of calcium lactate or calcium gluconate, 0.5wt% of calcium chloride, 0.2wt% of vitamin B6, and the balance is water.

[0039] S4. Ultrasonic-assisted germination: the soaked rice is placed in a container, the volume fraction of CO2 in the container is maintained at 10% for 24 h before the rice germination, and then placed in an ultrasonic environment with a frequency of 35 kHz and a power density of 0.3 W / cm 2 (the intermittent mode, the working cycle is: ultrasonic for 10 min, stop for 5 min), and a mixed gas containing CO2, O2 and inert gas is dynamically introduced into the container, wherein the volume fraction of CO2 is 10%, the volume fraction of O2 is 15%, and the balance is inert gas; the temperature of the rice in the container is maintained at 28-32℃, and the ultrasonic induction germination is performed for 30 h, while spraying: a water solution of γ-aminobutyric acid with a concentration of 2 mmol / L, trehalose with a concentration of 1 mmol / L and proline with a concentration of 1 mmol / L is sprayed on the rice every 3 h, the spraying flow rate is 100 mL / min, and the spraying time is 1 h.

[0040] When the length of the sprout reaches 1-3 mm, the germination is terminated, and the volume fraction of CO2 in the container is reduced to 7% within 24 h after the termination of the germination.

[0041] Subsequently, the germinated rice is subjected to two-stage vacuum freeze drying: the first stage is pre-freezing for 4 h at -30 to -40 °C, and the second stage is drying for 24 h at a vacuum degree of 20 Pa and a temperature of -50 to -60 °C; the water content of the rice after the vacuum freeze drying is ≤12%.

[0042] S5. Steaming: the rice treated in step S4 is steamed for 15 min at 110-120 °C, and then air-dried;

[0043] S6. Hulling: the rice treated in step S5 is subjected to hulling and rice milling to obtain steamed rice.

[0044] Example 2

[0045] The steamed rice of the present example is prepared in the following manner.

[0046] S1. Pretreatment: the rice is subjected to impurity removal, disinfection and washing in sequence;

[0047] S2. Magnetic field induction: the rice is treated in an alternating pulse magnetic field with a magnetic field strength of 10 mT and a frequency of 5 Hz for 50 min at 25 °C, wherein the magnetic field direction forms an angle of 30° with the plane of the rice layer.

[0048] S3. Soaking: the rice treated in the magnetic field is soaked in a soaking solution at 10 °C for 4 h, and then soaked in a soaking solution at 55 °C for 1 h; the soaking solution comprises the following raw materials in a mass fraction: 0.05 wt% of glutamate decarboxylase, 0.1 wt% of calcium lactate or calcium gluconate, 0.4 wt% of calcium chloride, 0.1 wt% of vitamin B6, and the balance being water.

[0049] S4. Ultrasonic-assisted germination: the soaked rice is placed in a container, the volume fraction of CO2 in the container is maintained at 8% for 24 h before the germination of the rice, and then the rice is placed in an ultrasonic environment with a frequency of 45 kHz and a power density of 0.8 W / cm 2 ; the container is dynamically supplied with a mixed gas containing CO2, O2 and inert gas, wherein the volume fraction of CO2 is 5%, the volume fraction of O2 is 10%, and the balance is inert gas; the temperature of the rice in the container is maintained at 30 °C, the ultrasonic induction germination is performed for 48 h, and the rice is sprayed with an aqueous solution containing 2 mmol / L of γ-aminobutyric acid, 0.05 mmol / L of trehalose and 0.5 mmol / L of proline every 2 h; the spraying flow rate is 200 mL / min, and the spraying time is 1 h.

[0050] When the length of the sprout reaches 1-3 mm, the germination is terminated, and the volume fraction of CO2 in the container is reduced to 5% within 24 h after the termination of the germination.

[0051] The germinated rice is subjected to two-stage vacuum freeze-drying: the first stage is pre-freezing for 2-4 h at -30 to -40 °C, and the second stage is drying for 12-24 h at a vacuum degree of 10-30 Pa and a temperature of -50 to -60 °C; the water content of the rice after the vacuum freeze-drying is ≤12%.

[0052] S5. Steaming: the rice treated in step S4 is steamed for 10 min at 110-120 °C, followed by air drying;

[0053] S6. Hulling: the rice treated in step S5 is subjected to hulling and rice milling to obtain steamed rice.

[0054] Example 3

[0055] The steamed rice of the present example is prepared as follows.

[0056] S1. Pretreatment: the rice is subjected to impurity removal, disinfection and washing in sequence;

[0057] S2. Magnetic field induction: the rice is treated in an alternating pulse magnetic field with a magnetic field strength of 20 mT and a frequency of 1 Hz at 35 °C for 120 min, wherein the magnetic field direction forms an angle of 40° with the plane of the rice layer.

[0058] S3. Soaking: the rice treated in the magnetic field is soaked in a soaking solution at 15 °C for 2 h, and then soaked in a soaking solution at 60 °C for 1 h; the soaking solution comprises the following raw materials in a mass fraction: 0.01 wt% of glutamate decarboxylase, 0.05 wt% of calcium lactate or calcium gluconate, 0.1 wt% of calcium chloride, 0.05 wt% of vitamin B6, and the balance being water.

[0059] S4. Ultrasonic-assisted germination: the soaked rice is placed in a container, the volume fraction of CO2 in the container is maintained at 9% for 24 h before the germination of the rice, and then the rice is placed in an ultrasonic environment with a frequency of 35 kHz and a power density of 0.8 W / cm 2 ; a mixed gas containing CO2, O2 and inert gas is dynamically introduced into the container, wherein the volume fraction of CO2 is 8%, the volume fraction of O2 is 13%, and the balance is inert gas; the temperature of the rice in the container is maintained at 30 °C, the ultrasonic induction germination is performed for 24 h, and the rice is sprayed with an aqueous solution of γ-aminobutyric acid with a concentration of 5 mmol / L, trehalose with a concentration of 1 mmol / L and proline with a concentration of 2 mmol / L every 1 h, the spraying flow rate is 50 mL / min, and the spraying time is 1 h.

[0060] When the length of the sprout reaches 1-3 mm, the germination is terminated, and the volume fraction of CO2 in the container is reduced to 5% within 24 h after the termination of the germination.

[0061] The germinated rice is subjected to two-stage vacuum freeze-drying: the first stage is pre-freezing for 4 h at -30 to -40 °C, and the second stage is drying for 12 h at a vacuum degree of 30 Pa and a temperature of -50 to -60 °C; the water content of the rice after the vacuum freeze-drying is ≤12%.

[0062] S5. Steaming: the rice treated in step S4 is steamed for 5 min at 110-120 °C, followed by air drying;

[0063] S6. Hulling: the rice treated in step S5 is subjected to hulling and rice milling to obtain steamed rice.

[0064] Example 4

[0065] The steamed rice of the present example is prepared as follows.

[0066] S1. Pretreatment: the rice is subjected to impurity removal, disinfection and washing in sequence.

[0067] S2. Magnetic field induction: the rice is treated in an alternating pulse magnetic field with a magnetic field strength of 20 mT and a frequency of 3 Hz for 80 min at 35 °C, wherein the magnetic field direction forms an angle of 30° with the plane of the rice layer.

[0068] S3. Soaking: the rice treated in the magnetic field is soaked in a soaking solution at 5 °C for 2 h, and then soaked in a soaking solution at 58 °C for 1.5 h; the soaking solution comprises the following raw materials in a mass fraction: 0.08 wt% of glutamate decarboxylase, 0.15 wt% of calcium lactate or calcium gluconate, 0.35 wt% of calcium chloride, 0.15 wt% of vitamin B6, and the balance is water.

[0069] S4. Ultrasonic-assisted germination: the soaked rice is placed in a container, the volume fraction of CO2 in the container is maintained at 10% for 24 h before the germination of the rice, and then the rice is placed in an ultrasonic environment with a frequency of 45 kHz and a power density of 0.5 W / cm 2 ; a mixed gas containing CO2, O2 and inert gas is dynamically introduced into the container, wherein the volume fraction of CO2 is 8%, the volume fraction of O2 is 15%, and the balance is inert gas; the temperature of the rice in the container is maintained at 28 °C, the ultrasonic induction germination is performed for 48 h, and the rice is sprayed with an aqueous solution of γ-aminobutyric acid with a concentration of 5 mmol / L, trehalose with a concentration of 1 mmol / L and proline with a concentration of 2 mmol / L every 3 h, the spraying flow rate is 300 mL / min, and the spraying time is 1 h.

[0070] When the length of the sprout reaches 1-3 mm, the germination is terminated, and the volume fraction of CO2 in the container is reduced to 5-7% within 24 h after the termination of the germination.

[0071] The germinated rice is subjected to two-stage vacuum freeze-drying: the first stage is pre-freezing for 2-4 h at -30 to -40 °C, and the second stage is drying for 12-24 h at a vacuum degree of 10-30 Pa and a temperature of -50 to -60 °C; the water content of the rice after the vacuum freeze-drying is ≤12%.

[0072] S5. Steaming: the rice treated in step S4 is steamed for 5-15 min at 110-120 °C, followed by air drying;

[0073] S6. Hulling: the rice treated in step S5 is subjected to hulling and rice milling to obtain steamed rice.

[0074] Example 5

[0075] The steamed rice of the present example is prepared as follows.

[0076] S1. Pretreatment: the rice is subjected to impurity removal, disinfection and washing in sequence;

[0077] S2. Magnetic field induction: the rice is treated in an alternating pulse magnetic field with a magnetic field strength of 20 mT and a frequency of 3 Hz for 30 min at 30 °C, wherein the magnetic field direction forms an angle of 60° with the plane of the rice layer.

[0078] S3. Soaking: the rice treated in the magnetic field is soaked in a soaking solution at 15 °C for 6 h, and then soaked in a soaking solution at 60 °C for 2 h; the soaking solution comprises the following raw materials in a mass fraction: 0.05 wt% of glutamate decarboxylase, 0.05 wt% of calcium lactate or calcium gluconate, 0.5 wt% of calcium chloride, 0.2 wt% of vitamin B6, and the balance being water.

[0079] S4. Ultrasonic-assisted germination: the soaked rice is placed in a container, the volume fraction of CO2 in the container is maintained at 10% for 24 h before the germination of the rice, and then the rice is placed in an ultrasonic environment with a frequency of 45 kHz and a power density of 0.5 W / cm 2 ; meanwhile, a mixed gas containing CO2, O2 and inert gas is dynamically introduced into the container, wherein the volume fraction of CO2 is 5%, the volume fraction of O2 is 15%, and the balance is inert gas; the temperature of the rice in the container is maintained at 32 °C, the ultrasonic induction germination is performed for 24 h, and the rice is sprayed with an aqueous solution containing 3 mmol / L of γ-aminobutyric acid, 1 mmol / L of trehalose and 0.5 mmol / L of proline every 2 h, the spraying flow rate is 100 mL / min, and the spraying time is 1 h.

[0080] When the sprout length reaches 1-3 mm, the germination is terminated, and the volume fraction of CO2 in the container is reduced to 7% within 24 h after the termination of the germination.

[0081] The germinated rice is subjected to two-stage vacuum freeze-drying: the first stage is pre-freezing at -30℃ to -40℃ for 2-4 h, and the second stage is drying at a vacuum degree of 10 Pa and a temperature of -50℃ to -60℃ for 24 h; the water content of the rice after the vacuum freeze-drying is ≤12%.

[0082] S5. Steaming: the rice treated in step S4 is steamed at 110-120℃ for 15 min, followed by air drying;

[0083] S6. Hulling: the rice treated in step S5 is subjected to hulling and milling to obtain steamed rice.

[0084] Comparative Example 1

[0085] The difference from Example 1 is that the magnetic field induction treatment in step S2 is not performed, and the remaining steps are the same as those in Example 1.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that the low-temperature (5℃) soaking treatment in step S3 is not performed, and the soaking is directly performed at 58℃, and the remaining steps are the same as those in Example 1.

[0088] Comparative Example 3

[0089] The difference from Example 1 is that the ultrasonic treatment in step S4 is not performed, and the remaining steps are the same as those in Example 1.

[0090] Comparative Example 4

[0091] The difference from Example 1 is that the magnetic field induction treatment in step S2 is not performed, and the ultrasonic treatment in step S4 is not performed, and the remaining steps are the same as those in Example 1.

[0092] Comparative Example 5

[0093] The difference from Example 1 is that the spraying treatment in step S4 is not performed, and the remaining steps are the same as those in Example 1.

[0094] Experimental Example

[0095] The rice treated by the magnetic field induction in Examples 1-5 and the rice without the magnetic field induction (control group) are used as objects, and the Fluo-4 AM fluorescent probe is used to detect the content of intracellular Ca 2+ , and the results are shown in Table 1.

[0096] Table 1 Intracellular Ca2+ Concentration (nmol / L)

[0097] Example 1 Example 2 Example 3 Example 4 Example 5 Control Ca 2+ content 220 210 231 224 215 85

[0098] Table 1 shows that after magnetic field induction treatment, the Lorentz force of the alternating magnetic field causes transient micropores (2-5 nm in diameter) to form in the phospholipid bilayer of the cell membrane in rice, promoting the formation of Ca2+. 2+ internal flow. Ca 2+ Upon binding to calmodulin (CaM), it activates the downstream MAPK signaling pathway, upregulates GAD gene expression, and increases intracellular Ca2+ levels. 2+ The concentration of [something] increased significantly.

[0099] Using the rice samples from Examples 1-5 and Comparative Examples 1-5 as subjects, the contents of γ-aminobutyric acid (GABA) and reducing sugars in the rice were detected, and the results are shown in Table 2. In Table 2, the data for each group are the average values ​​of three measurements taken from three samples.

[0100] Table 2. Content of γ-aminobutyric acid and reducing sugars in various grains

[0101]

[0102]

[0103] Table 2 shows that the rice in Examples 1-5 had lower reducing sugar content and higher γ-aminobutyric acid (GABA) content. The reducing sugar in the rice can be fully converted into GABA. This indicates that the combined treatment of pulsed magnetic field, ultrasonic treatment, and low-temperature induction can promote the enrichment of GABA in the rice and increase its content. In Comparative Example 5, no spraying treatment was performed, i.e., no exogenous GABA was added. The GABA content in its rice was lower than that in Example 1. This shows that by adding an aqueous solution of GABA, external GABA can enter the rice, further increasing its content.

[0104] In summary, the method for preparing parboiled rice rich in γ-aminobutyric acid (GABA) provided by this invention combines pulsed magnetic field, low-temperature soaking, and ultrasonic treatment to promote rice germination, improve germination efficiency, and promote the production of GABA in rice, thereby increasing the GABA content. Specifically, the pulsed magnetic field (10-20 mT) induces micropores in the cell membrane, and the low temperature (5-15℃) induces GABA enzyme expression; the combination of these two factors increases GABA synthase activity by more than 40%. Ultrasonic treatment (35-45 kHz) promotes metabolite diffusion.

[0105] The embodiments described above are only part of the embodiments of the present application, rather than all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only to represent selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

Claims

1. A method for preparing a γ-aminobutyric acid-enriched GABA rice, characterized by, The method comprises the following steps: S1. Pretreatment: sequentially removing impurities, disinfecting and cleaning the rice; S2. Magnetic field induction: treating the rice in a 10-20 mT pulsed magnetic field at 25-35℃ for 30-120 min; S3. Soaking: soaking the rice treated by the magnetic field in a soaking liquid at 5-15℃ for 2-6 h; and then soaking the rice in a soaking liquid at 55-60℃ for 1-2 h; the soaking liquid comprises the following raw materials by mass fraction: 0.01-0.1wt% glutamate decarboxylase, 0.05-0.2wt% calcium lactate or calcium gluconate, 0.1-0.5wt% calcium chloride, 0.05-0.2wt% vitamin B6, and the balance being water; S4. Ultrasonic-assisted germination: the soaked rice is placed in an ultrasonic environment with a frequency of 35-45 kHz and a power density of 0.3-0.8 W / cm 2 for 24-48 h at 28-32℃; when the length of the sprout reaches 1-3 mm, the germination is terminated, and vacuum freeze-drying is performed; during the ultrasonic-induced germination, dynamic gas regulation is also included: a mixed gas containing CO2, O2 and inert gas is introduced into the rice, wherein the volume fraction of CO2 is 5-10%, the volume fraction of O2 is 10-15%, and the balance is inert gas; the volume fraction of CO2 is maintained at 8-10% 24 h before the germination of the rice, and the volume fraction of CO2 is reduced to 5-7% within 24 h after the end of the germination; in addition, every 1-3 hours, the rice is sprayed with an aqueous solution of γ-aminobutyric acid with a concentration of 0.5-5 mmol / L, trehalose with a concentration of 0.1-1 mmol / L, and proline with a concentration of 0.5-2 mmol / L, and the spraying flow rate is 50-300 mL / min; S5. Steaming: steaming the rice treated in step S4 at 110-120℃ for 5-15 min, and then air-drying; S6. Hulling: hulling and polishing the rice treated in step S5 to obtain steamed rice.

2. The method of preparing γ-aminobutyric acid-enriched steamed rice according to claim 1, wherein In the step S4, the water content of the rice after vacuum freeze-drying is ≤12%.

3. The method of preparing γ-aminobutyric acid-enriched steamed rice according to claim 1, wherein The pulsed magnetic field in the step S2 is an alternating magnetic field with a frequency of 1-5 Hz and a magnetic field direction that forms an angle of 30-60° with the plane of the rice layer.

4. The method of preparing γ-aminobutyric acid-enriched steamed rice according to claim 1, wherein The ultrasonic treatment in the step S4 adopts an intermittent mode with an operation cycle of 5-10 min of ultrasonic treatment and 2-5 min of stopping.

5. The method of preparing γ-aminobutyric acid-enriched steamed rice according to claim 1, wherein The vacuum freeze-drying in the step S4 comprises two stages: a first stage of pre-freezing at -30℃ to -40℃ for 2-4 h, and a second stage of drying at a vacuum degree of 10-30 Pa and a temperature of -50℃ to -60℃ for 12-24 h.

6. A γ-aminobutyric acid-enriched popped rice, characterized by, The steamed rice is prepared by the method of any one of claims 1-5.

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