A high-phenolic acid germinated brown rice and its preparation method

Abstract

This invention discloses a high-phenolic acid germinated brown rice and its preparation method, comprising the following steps: S1. Collecting whole-germ rice grains as raw material for germination; S2. Acidifying and washing the raw material to obtain acidified brown rice; S3. Soaking the acidified brown rice in Na2SeO3 solution and treating it under a high-voltage electrostatic field, then rinsing and draining to obtain pre-germinated brown rice; S4. Adding Na2SeO3 solution to the pre-germinated brown rice, first subjecting it to high-temperature ultrasonic germination treatment, then to low-temperature ultrasonic germination treatment, then rinsing and draining to obtain germinated brown rice; S5. Drying the germinated brown rice to obtain the high-phenolic acid germinated brown rice product. This method combines the accumulation of phenolic acids and the enrichment of organic selenium in germinated brown rice through a combination of multiple stress conditions, achieving not only the complete preservation of the nutritional components in brown rice, but also richness in selenium peptides, selenoproteins, and polyphenols, endowing germinated brown rice with antioxidant and immune-enhancing effects, and with a low glycemic index.

Description

Technical Field

[0001] This invention relates to the field of grain processing technology, and in particular to a high-phenolic acid germinated brown rice and its preparation method. Background Technology

[0002] Brown rice is rice grain with the husk removed, retaining the inner bran layer intact. Compared to refined white rice, brown rice retains the nutrients found in the bran, such as essential fatty acids, dietary fiber, vitamins, minerals, and plant bioactive substances. Epidemiological studies have shown that regular consumption of brown rice and related products can reduce the risk of chronic diseases such as cardiovascular disease, type II diabetes, obesity, and cancer. The germination of brown rice involves a series of physiological and biochemical changes, such as reduced seed coat coverage, activated metabolic activity, gene transcription activation, relaxation of embryonic cell walls, and reassembly of organelles, leading to significant biochemical, nutritional, and sensory changes in its edible parts. Germinated brown rice is considered to have higher nutritional and physiological value than ungerminated brown rice. To obtain high-quality brown rice with high levels of beneficial nutrients, abiotic stress methods can be used to regulate plant growth and development during germination.

[0003] For example, Chinese patent CN 109221945 B describes a method for preparing germinated brown rice rich in oryzanol and vitamin E using oxidative stress. The oryzanol and vitamin E content in this method is 2.0-3.6 times and 4.4-6.5 times higher, respectively, than that in germinated brown rice prepared without oxidative stress. Chinese patent CN111887386 A describes a method for preparing germinated brown rice using dual stress of low oxygen and calcium and zinc composite metal ions, resulting in a significant increase in γ-aminobutyric acid (GABA) content.

[0004] However, the nutritional value and sensory qualities of germinated brown rice obtained using the above techniques still need improvement. The brown rice has low levels of important secondary metabolites such as phenolic acids and organic selenium, a high glycemic index (GI), and poor taste, which is not conducive to the full realization of the physiological benefits of germinated brown rice. Summary of the Invention

[0005] In view of this, this application provides high-phenolic acid germinated brown rice and its preparation method to solve the problems of low nutritional value and poor taste of brown rice.

[0006] To achieve the above technical objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a method for preparing high-phenolic acid germinated brown rice, comprising the following steps:

[0008] S1. Collect rice grains with intact germs as raw material for germination brown rice;

[0009] S2. Acidify and wash the brown rice raw material to obtain acidified brown rice;

[0010] S3. Soak the acidified brown rice in Na2SeO3 solution and treat it under a high voltage electrostatic field, then rinse and drain to obtain pre-germinated brown rice;

[0011] S4. Add Na2SeO3 solution to pre-germinated brown rice, first perform high-temperature ultrasonic germination treatment, then perform low-temperature ultrasonic germination treatment, and then rinse and drain to obtain germinated brown rice.

[0012] S5. Dry the germinated brown rice to obtain the high-phenolic acid germinated brown rice product.

[0013] Preferably, in step S3, the process conditions for the high-voltage electrostatic field are as follows: temperature is 18-25℃, the distance between the arc-shaped plates is 6-10cm, and the voltage is 30-60KV.

[0014] Preferably, in step S4, the temperature of the high-temperature ultrasonic germination treatment is 28-35℃, the relative humidity of the high-temperature ultrasonic germination treatment is 85-95%, and the ultrasonic power of the high-temperature ultrasonic germination treatment is 200-400W; the temperature of the low-temperature ultrasonic germination treatment is 18-25℃, the relative humidity of the low-temperature ultrasonic germination treatment is 90-98%, and the ultrasonic power of the low-temperature ultrasonic germination treatment is 50-200W.

[0015] Preferably, in step S2, the acidifying solution used for acidification treatment is acidic electrolyzed water with a pH of 5.5-6.0, an effective chlorine concentration of 220-380 mg / L, and a treatment time of 10-20 min.

[0016] Preferably, in step S4, the ratio of the concentration of Na2SeO3 solution used for high-temperature ultrasonic germination to the concentration of Na2SeO3 solution used for low-temperature ultrasonic germination is 2-3:1.

[0017] Preferably, the ratio of the concentration of the Na2SeO3 solution used in step S3 to the concentration of the Na2SeO3 solution used in the high-temperature ultrasonic germination in step S4 is 1:4-5.

[0018] Preferably, in step S5, the drying temperature is 32-40℃ and the drying wind speed is 2-8m / s.

[0019] Preferably, the ultrasonic frequency for high-temperature ultrasonic germination treatment is 5 minutes every 4-5 hours, and the ultrasonic frequency for low-temperature ultrasonic germination treatment is 10 minutes every 6-8 hours.

[0020] Preferably, the total duration of high-temperature ultrasonic germination treatment is 24-36 hours, and the total duration of low-temperature ultrasonic germination treatment is 60-96 hours.

[0021] Secondly, this application provides a high-phenolic acid germinated brown rice.

[0022] The beneficial effects of this application are as follows:

[0023] This scheme uses brown rice as raw material, fully explores and utilizes the functional factors in brown rice, and combines Na2SeO3 solution, high voltage electrostatic field and ultrasonic conditions to carry out multi-stress temperature-segmented germination treatment, thereby increasing the content of phenolic acid in germinated brown rice.

[0024] This scheme further enhances the enrichment of phenolic acids and organic selenium by adjusting germination conditions during the multi-stress germination process and implementing a treatment process of high-temperature germination followed by low-temperature germination.

[0025] This method combines the accumulation of phenolic acids and the enrichment of organic selenium in germinated brown rice through a combination of multiple stress conditions, so that the increase in phenolic acid and organic selenium content is synergistic. In addition to fully retaining the dietary fiber, unsaturated fatty acids, vitamins, oryzanol and other nutritious components in brown rice, it is also rich in selenopeptides, selenoproteins, polyphenols and other functional components.

[0026] The multiple stress treatments in this program improve the taste and quality of germinated brown rice, endowing it with the physiological effects of anti-oxidation, enhanced immunity, and delayed starch digestion. Furthermore, its low glycemic index meets the needs of people with abnormal glucose metabolism or those who need to control their blood sugar and weight for rice-based staple food products. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Phenolic acids are important secondary metabolites in brown rice, mainly including ferulic acid, caffeic acid, coumaric acid, and protocatechuic acid. They possess various physiological functions, such as antioxidation, improving nervous system function, protecting the cardiovascular system, lowering blood sugar, and inhibiting the formation of advanced glycation end products (AGEs), playing a crucial role in the functional activity of brown rice. During brown rice germination, stress exacerbates the production of reactive oxygen species (ROS), thereby damaging the structure of macromolecules such as DNA, proteins, and lipids in the seeds. At this time, the body's defense system synthesizes antioxidants (such as phenolic substances) to scavenge ROS and protect the body from stress damage.

[0029] Selenium is an essential trace element for the human body, participating in many important metabolic pathways, including the synthesis of thyroid hormones, the antioxidant defense system, and immune function. The Chinese Nutrition Society recommends a daily selenium intake of 50-250 μg for adults. Selenium deficiency can lead to many health problems, such as Keshan disease, cancer, heart disease, and hyperthyroidism. Selenium can affect the active sites of proteins and enhance their antioxidant capacity; organic selenium can even directly participate in the scavenging of free radicals. Studies have shown that over 80% of the selenium in selenium-enriched rice exists as organic selenium in the form of selenoproteins, making it a good food source for daily selenium-fortified diets. Organically selenium-fortified rice and other agricultural products can be produced through natural selenium enrichment during the production process or by using selenium bio-fortification technology (application of selenium fertilizer), resulting in a significant increase in selenoprotein content. In addition, GB 14880-2012, the National Food Safety Standard for Food Fortifiers, stipulates that selenium can be added to food as a food fortifier, with a usage of 140-280 μg / kg in rice and its products. Permitted sources of compounds include sodium selenite, sodium selenate, and selenoproteins.

[0030] As the background above indicates, phenolic acids and selenium have a significant impact on the nutritional value of germinated brown rice. This application, through multiple stress treatments, prepared germinated brown rice with high phenolic acid content, good organic selenium enrichment, low GI value, and excellent taste, greatly improving the nutritional value of the germinated brown rice and enabling it to better exert its physiological and health-promoting effects. The specific scheme is as follows:

[0031] This application provides a method for preparing high-phenolic acid germinated brown rice, comprising the following steps:

[0032] S1. Collect rice grains with intact germs as raw material for germination brown rice;

[0033] S2. Acidify and wash the brown rice raw material to obtain acidified brown rice;

[0034] S3. Soak the acidified brown rice in Na2SeO3 solution and treat it under a high voltage electrostatic field, then rinse and drain to obtain pre-germinated brown rice;

[0035] S4. Add Na2SeO3 solution to pre-germinated brown rice, first perform high-temperature ultrasonic germination treatment, then perform low-temperature ultrasonic germination treatment, and then rinse and drain to obtain germinated brown rice.

[0036] S5. Dry the germinated brown rice to obtain the high-phenolic acid germinated brown rice product.

[0037] Overall, the above preparation method results in a high germination rate for brown rice. In addition to fully preserving the dietary fiber, unsaturated fatty acids, vitamins, oryzanol, and other nutritious components in brown rice, it is also rich in phenolic acids, selenoproteins, and other functional components. The stress treatment in steps S3-S4 not only improves the taste and quality of the germinated brown rice, but the high content of phenolic acids and organic selenium also endows the germinated brown rice with various physiological effects such as anti-oxidation and enhanced immunity. Furthermore, its low glycemic index meets the needs of people with abnormal glucose metabolism or those who need to control their blood sugar and weight for rice-based staple food products.

[0038] In step S2, the brown rice raw material undergoes acidification treatment, which not only prevents the growth of microorganisms during the germination process, but also significantly improves the water absorption and water retention capacity of the dietary fiber in the outer layer of the brown rice raw material through oxidation modification, resulting in increased water content in the brown rice and promoting the germination and growth of the brown rice embryo. In some embodiments, the acidification solution used in step S2 is acidic electrolyzed water. The use of acidic electrolyzed water treatment can lead to increased permeability of the epidermal cells, which is conducive to the passive absorption of salt ions by the cells and enhances the selenium enrichment capacity.

[0039] In step S3, soaking brown rice in a low-concentration Na2SeO3 solution under a high-voltage electrostatic field accelerates the germination process of the brown rice embryo, rapidly initiating and awakening the growth and differentiation of the germinal root cells, allowing the brown rice embryo to quickly enter the germination stage. Furthermore, the treatment increases the organic selenium content in the brown rice, opening the active absorption pathway of selenite. The reasons for these effects are twofold: firstly, the high-voltage electrostatic field treatment accelerates the water absorption of the brown rice, significantly increasing the free water content and water activity, which is beneficial for the germination and growth of the brown rice embryo; secondly, under the action of the high-voltage electrostatic field, SeO3... 2- Selenium is abundantly accumulated on the surface of brown rice grains, significantly enhancing its absorption efficiency through passive transport and forming selenopeptides or selenoproteins. Furthermore, the high-voltage electrostatic field activates the brown rice's bio-enzyme system, accelerating the metabolism of stored starch, protein, lipids, and other major nutrients, as well as the synthesis of enzymes, transport proteins, and amino acids. The rapid synthesis and accumulation of transport proteins opens the active absorption pathway of selenite, accelerating the absorption of SeO3 by brown rice. 2- Absorption and transport.

[0040] In step S4, the pre-germinated brown rice is soaked in a high-concentration Na2SeO3 solution, combined with ultrasonic stress, and germinated in two steps at high and low temperatures to obtain a germinated brown rice product with high germination rate and high content of organic selenium and polyphenols. After the pre-germination treatment in step S3, the brown rice has a higher content of SeO3. 2- It includes both passive and active absorption, and its absorption of SeO3 2-The process significantly enhances the polyphenol synthesis process, increasing the content of selenopeptides and selenoproteins in brown rice. During germination in step S4, the activity of endogenous enzymes related to polyphenol synthesis in brown rice is activated. Selenopeptides and selenoproteins can interact with enzymes related to the phenolic acid synthesis pathway in brown rice, enhancing their activity and further accelerating the accumulation of polyphenols in germinated brown rice. Furthermore, ultrasonic treatment not only generates a large number of free radicals, stimulating the production of secondary metabolites such as polyphenols, but also improves cell sap homogeneity, enhancing the interaction efficiency between selenopeptides and selenoproteins and enzymes related to phenolic acid synthesis, further strengthening the activity of these enzymes, promoting the accumulation of polyphenols in brown rice, and increasing the polyphenol content in brown rice.

[0041] It is worth noting that in step S4, the brown rice germination process is divided into two stages: high-temperature ultrasonic germination followed by low-temperature ultrasonic germination. These two steps correspond to the organ development and functional component accumulation stages of the germinated brown rice. Under high-temperature conditions (28-35℃), the activity of biological enzymes and transport proteins in brown rice is high, which is conducive to the rapid germination and growth of the embryo, leading to the growth of the germinal root and the development of the germ. The roots, shoots, and other organs of the brown rice form rapidly. However, high temperatures also lead to the rapid consumption of nutrients in the brown rice and the accelerated metabolism of functional components such as polyphenols, which is not conducive to the accumulation of functional components such as polyphenols. Furthermore, if the roots and shoots of the germinated brown rice are too long, they are not easy to package and are not easily accepted by consumers. Under low temperature (18-25℃) conditions, although the activity of biological enzymes and transport proteins in brown rice is low, which slows down the metabolic decomposition of nutrients and inhibits the growth of brown rice roots and sprouts, thus improving the appearance quality of germinated brown rice, the cell permeability increases under low temperature stress, the passive absorption of selenite is aggravated, the conversion efficiency of inorganic selenium to organic selenium is improved, and the content of organic selenium in germinated brown rice continues to increase. At the same time, low temperature stress also leads to the production of a large number of free radicals in cells, which stimulates the generation of secondary metabolites such as polyphenols, and the polyphenol content continues to rise. In this method, germination first undergoes a high-temperature phase followed by a low-temperature phase. During the high-temperature germination stage, the high ultrasonic power allows starch, protein, and fat synthesis enzymes in the cell sap to fully contact the substrate, enhancing the efficiency of nutrient decomposition and synthesis of functional components. Free radicals are continuously generated and accumulated in the cells, activating the cells' own antioxidant response mechanism and producing polyphenols and other secondary metabolites with antioxidant activity. After the high-temperature germination stage, the free radical content in the cells reaches its maximum value. If it continues to increase, it can cause irreversible damage to the cells. At this point, the process transitions to the low-temperature germination stage, using lower ultrasonic power to reduce the rate of free radical generation in the cells and maintain them at a reasonable and stable level. The cells can respond quickly and continuously and efficiently stimulate the synthesis of polyphenols and other secondary metabolites.

[0042] In step S5, the drying temperature is 32-40℃ and the drying wind speed is 2-8m / s. The low-temperature hot air drying treatment not only greatly preserves the content and efficacy characteristics of polyphenols and other functional components in the germinated brown rice, but also reduces the production cost of germinated brown rice, making it suitable for large-scale promotion and application.

[0043] In some embodiments, the process conditions for the high-voltage electrostatic field in step S3 are as follows: temperature is 18-25℃, arc-shaped electrode spacing is 6-10cm, and voltage is 30-60KV.

[0044] In some embodiments, the ratio of the concentration of the Na2SeO3 solution used in step S3 to the concentration of the Na2SeO3 solution used in the high-temperature ultrasonic germination in step S4 is 1:4-5.

[0045] In some embodiments, in step S4, the temperature for high-temperature ultrasonic germination is 28-35°C, the relative humidity is 85-95%, and the ultrasonic power is 200-400W; the temperature for low-temperature ultrasonic germination is 18-25°C, the relative humidity is 90-98%, and the ultrasonic power is 50-200W. In step S4, the ratio of the Na₂SeO₃ solution concentration used for high-temperature ultrasonic germination to that used for low-temperature ultrasonic germination is 2-3:1. The ultrasonic frequency for high-temperature ultrasonic germination is 5 minutes every 4-5 hours, and the ultrasonic frequency for low-temperature ultrasonic germination is 10 minutes every 6-8 hours. The total duration of high-temperature ultrasonic germination is 24-36 hours, and the total duration of low-temperature ultrasonic germination is 60-96 hours.

[0046] This application provides a high-phenolic acid germinated brown rice with a total phenolic acid content of 1555.84-2020.11 μg / g DW, an organic selenium content of 120.34-175.50 μg / kg DW, and a glycemic index (GI) of 50.67-53.90. The high total phenolic acid content, high organic selenium content, and low GI value of this high-phenolic acid germinated brown rice endow it with excellent physiological effects.

[0047] This treatment method results in high levels of phenolic acids and organic selenium, giving the germinated brown rice significant antioxidant and free radical scavenging effects. The selenium-enriched germinated brown rice is rich in organic selenium, including selenopeptides and selenoproteins, which offer antioxidant and immune-boosting benefits. It is also rich in polyphenols, composed of phenolic acids such as ferulic acid, p-coumaric acid, and protocatechuic acid, which provide antioxidant, blood sugar-lowering, and nervous system-improving effects. The synergistic effect of organic selenium and polyphenols significantly enhances the antioxidant properties of the germinated brown rice.

[0048] This method significantly improves the taste and quality of sprouted brown rice during cooking. In traditional rice cooker cooking modes, it can be cooked at the same rate as regular white rice, with a taste value close to that of white rice, making it more acceptable to consumers. During the sprouting process, the water absorption and retention of brown rice are significantly enhanced. The presence of organic selenium, such as selenopeptides and selenoproteins, as well as polyphenols, improves the gel properties of starch, and the texture characteristics of cooked rice, such as consistency and elasticity, making it comparable to white rice.

[0049] This recipe produces sprouted brown rice, which is a low-GI food suitable for people with disordered glucose metabolism. On one hand, organic selenium, such as selenopeptides and selenoproteins, as well as polyphenols, significantly inhibit the activity of α-amylase and β-amylase, reducing starch hydrolysis. On the other hand, organic selenium, such as selenopeptides and selenoproteins, and polyphenols interact with starch, altering its configuration and gelatinization properties, and increasing the content of resistant starch.

[0050] The following specific embodiments further illustrate this solution.

[0051] Example 1

[0052] A method for preparing high-phenolic acid germinated brown rice includes the following steps:

[0053] S1. Brown rice preparation: Select plump rice grains with a germination rate of over 95%, and after hulling, remove rice grains with damaged embryos and collect rice grains with intact embryos as raw materials for germination brown rice.

[0054] S2. Brown rice acidification treatment: Soak the brown rice raw material in acidic electrolyzed water with pH 5.5 and effective chlorine concentration of 380 mg / L for 10 minutes, then rinse it repeatedly with tap water 3 times, drain the water, and obtain acidified brown rice.

[0055] S3. Pre-germination treatment of brown rice: Acidified brown rice was soaked in a 1 mmol / L Na2SeO3 solution at a material-to-liquid ratio of 1:50 g / mL and then placed in a high-voltage electrostatic field at 18℃ for 15 min. After rinsing three times with tap water and draining, pre-germinated brown rice was obtained. The high-voltage electrostatic field treatment parameters were: arc plate spacing of 6 cm and voltage of 30 kV.

[0056] S4. Stressed germination of brown rice: Spread the pre-germinated brown rice evenly on a tray with a thickness of about 0.8cm. Then add Na2SeO3 solution to the tray to a height of 0.5cm. First, perform high-temperature ultrasonic germination treatment, and then perform low-temperature ultrasonic germination treatment. After germination, rinse the brown rice repeatedly with tap water 5 times and drain the water to obtain germinated brown rice.

[0057] The high-temperature ultrasonic germination process involves: a temperature of 28℃, a relative humidity of 85%, a Na₂SeO₃ solution concentration of 10 mmol / L, a germination time of 24 hours, and ultrasonic treatment of brown rice for 5 minutes every 4 hours during germination at a power of 200W, while maintaining a constant Na₂SeO₃ solution level and concentration in the tray throughout the germination process. The low-temperature ultrasonic germination process involves: a temperature of 18℃, a relative humidity of 90%, a Na₂SeO₃ solution concentration of 5 mmol / L, a germination time of 60 hours, and ultrasonic treatment of brown rice for 10 minutes every 6 hours during germination at a power of 50W, while maintaining a constant Na₂SeO₃ solution level and concentration in the tray throughout the germination process.

[0058] S5. Drying of germinated brown rice: After germination, the brown rice is placed in an environment with a temperature of 32℃ and a wind speed of 2m / s and dried until the moisture content is below 10%, thus obtaining the high-phenolic acid germinated brown rice product.

[0059] Example 2

[0060] A method for preparing high-phenolic acid germinated brown rice includes the following steps:

[0061] S1. Brown rice preparation: Select plump rice grains with a germination rate of over 95%, and after hulling, remove rice grains with damaged embryos and collect rice grains with intact embryos as raw materials for germination brown rice.

[0062] S2. Brown rice acidification treatment: Soak the brown rice raw material in acidic electrolyzed water with pH 5.8 and effective chlorine concentration of 300 mg / L for 16 minutes, then rinse it repeatedly with tap water 5 times, drain the water, and obtain acidified brown rice.

[0063] S3. Pre-germination treatment of brown rice: Acidified brown rice was soaked in a 3 mmol / L Na2SeO3 solution at a material-to-liquid ratio of 2:50 g / mL and then placed in a high-voltage electrostatic field at 22℃ for 35 min. After rinsing with tap water 8 times, the rice was drained and set aside to obtain pre-germinated brown rice. The high-voltage electrostatic field treatment parameters were: 8 cm spacing between the arc-shaped plates and 60 kV voltage.

[0064] S4. Stressed germination of brown rice: Spread the pre-germinated brown rice on a tray with a thickness of about 1.5cm. Then add Na2SeO3 solution to the tray to a height of 1cm. First, perform high-temperature ultrasonic germination treatment, and then perform low-temperature ultrasonic germination treatment. After germination, rinse the brown rice repeatedly with tap water 10 times and drain the water to obtain germinated brown rice.

[0065] The high-temperature ultrasonic germination process involves: a temperature of 33℃, a relative humidity of 90%, a Na₂SeO₃ solution concentration of 15 mmol / L, a germination time of 30 hours, and ultrasonic treatment of brown rice for 8 minutes every 5 hours during germination at a power of 300W, while maintaining a constant Na₂SeO₃ solution level and concentration in the tray throughout the germination process. The low-temperature ultrasonic germination process involves: a temperature of 22℃, a relative humidity of 95%, a Na₂SeO₃ solution concentration of 8 mmol / L, a germination time of 72 hours, and ultrasonic treatment of brown rice for 12 minutes every 7 hours during germination at a power of 150W, while maintaining a constant Na₂SeO₃ solution level and concentration in the tray throughout the germination process.

[0066] S5. Drying of germinated brown rice: After germination, the brown rice is placed in an environment with a temperature of 36℃ and a wind speed of 6m / s and dried until the moisture content is below 10%, thus obtaining the high-phenolic acid germinated brown rice product.

[0067] Example 3

[0068] A method for preparing high-phenolic acid germinated brown rice includes the following steps:

[0069] S1. Brown rice preparation: Select plump rice grains with a germination rate of over 95%, and after hulling, remove rice grains with damaged embryos and collect rice grains with intact embryos as raw materials for germination brown rice.

[0070] S2. Brown rice acidification treatment: Soak the brown rice raw material in acidic electrolyzed water with pH 6 and effective chlorine concentration of 220 mg / L for 20 minutes, then rinse it repeatedly with tap water 4 times, drain the water, and obtain acidified brown rice.

[0071] S3. Pre-germination treatment of brown rice: Acidified brown rice was soaked in a 5 mmol / L Na2SeO3 solution at a material-to-liquid ratio of 5:50 g / mL and then placed in a high-voltage electrostatic field at 25℃ for 60 min. After that, it was rinsed repeatedly with tap water 5 times, drained and set aside to obtain pre-germinated brown rice. The high-voltage electrostatic field treatment parameters were: arc plate spacing of 10 cm and voltage of 45 KV.

[0072] S4. Stressed germination of brown rice: Spread the pre-germinated brown rice on a tray with a thickness of about 2cm. Then add Na2SeO3 solution to the tray to a height of 1.5cm. First, perform high-temperature ultrasonic germination treatment, and then perform low-temperature ultrasonic germination treatment. After germination, rinse the brown rice repeatedly with tap water 8 times and drain the water to obtain germinated brown rice.

[0073] The high-temperature ultrasonic germination process involves: a temperature of 35℃, a relative humidity of 95%, a Na₂SeO₃ solution concentration of 20 mmol / L, a germination time of 36 hours, and ultrasonic treatment of brown rice for 10 minutes every 6 hours during germination at a power of 400W. The Na₂SeO₃ solution level and concentration are maintained constant throughout the germination process. The low-temperature ultrasonic germination process involves: a temperature of 25℃, a relative humidity of 98%, a Na₂SeO₃ solution concentration of 10 mmol / L, a germination time of 96 hours, and ultrasonic treatment of brown rice for 15 minutes every 8 hours during germination at a power of 200W. The Na₂SeO₃ solution level and concentration are maintained constant throughout the germination process.

[0074] S5. Drying of germinated brown rice: After germination, the brown rice is placed in an environment with a temperature of 40℃ and a wind speed of 8m / s and dried until the moisture content is below 10%, thus obtaining the high-phenolic acid germinated brown rice product.

[0075] Comparative Example 1

[0076] A method for preparing germinated brown rice, which is otherwise the same as in Example 2, except that:

[0077] S3. Pre-germination treatment of brown rice: Soak acidified brown rice in ultrapure water at a ratio of 2:50g / mL, then rinse repeatedly with tap water 8 times, drain the water and set aside to obtain pre-germinated brown rice.

[0078] S4. Germination of brown rice: Spread the pre-germinated brown rice evenly on a tray with a thickness of about 1.5cm. Then add ultrapure water to the tray to a height of 1cm. Germinate the rice at a constant temperature of 33℃ without ultrasound. After germination, rinse the brown rice repeatedly with tap water 10 times and drain the water to obtain germinated brown rice.

[0079] Comparative Example 2

[0080] A method for preparing germinated brown rice is the same as in Example 2, except that the Na2SeO3 solution in steps S3 and S4 is replaced with ultrapure water.

[0081] Comparative Example 3

[0082] A method for preparing germinated brown rice is the same as in Example 2, except that step S3 does not include high-voltage electrostatic field treatment.

[0083] Comparative Example 4

[0084] A method for preparing germinated brown rice, which is the same as in Example 2 except that in step S4, neither the high-temperature germination stage nor the low-temperature germination stage includes ultrasonic stress treatment.

[0085] Comparative Example 5

[0086] A method for preparing germinated brown rice, the other contents are the same as in Example 2, except that step S4. Stress germination of brown rice: spread the pre-germinated brown rice on a tray with a thickness of about 1.5 cm, then add ultrapure water to the tray to a solution height of 1 cm, and perform constant temperature germination treatment at 33°C under ultrasonic conditions. After germination, rinse the brown rice repeatedly with tap water 10 times, drain the water, and obtain germinated brown rice.

[0087] Comparative Example 6

[0088] A method for preparing brown rice, which is otherwise the same as in Example 2, except that step S4 is not included.

[0089] Comparative Example 7

[0090] A method for preparing refined white rice: The brown rice raw material in Example 2 is milled and polished to obtain refined white rice.

[0091] Evaluation Test

[0092] The phenolic acid content in the germinated brown rice prepared in Examples 1-3 and Comparative Examples 1-5, as well as the brown rice prepared in Comparative Example 6 and the polished white rice prepared in Comparative Example 7, was determined to evaluate the phenolic acid enrichment effect of germinated brown rice under different conditions. The phenolic acid content was determined using the national standard high-performance liquid chromatography method, and the content of the main phenolic acids was calculated using different phenolic acid standards as references. The results are shown in Table 1.

[0093] Table 1. Phenolic acid content of germinated brown rice (μg / g DW)

[0094]

[0095]

[0096] Note: Different letters in each column indicate significant differences (p<0.05); "-" indicates not detected.

[0097] As shown in Table 1, the polished white rice in Comparative Example 7 contained very little phenolic acid, while the brown rice in Comparative Example 6 mainly consisted of monomers such as ferulic acid, p-coumaric acid, protocatechuic acid, mesocoumaric acid, and caffeic acid, with a content of 585.39 μg / g DW. Compared with Comparative Examples 1-7, the content of major phenolic acid monomers and total phenolic acid in the germinated brown rice prepared under stress treatment in Examples 1-3 was significantly increased (p<0.05), and the germinated brown rice prepared in Example 2 had the highest total phenolic acid content, reaching 2020.11 μg / g DW. This is because the brown rice was treated with a high-voltage electrostatic field combined with a low-concentration Na2SeO3 solution during the pre-germination stage, which accelerated the absorption of water by the brown rice, significantly increasing the free water content and water activity in the brown rice, which is beneficial to the germination and growth of the brown rice embryo. In the brown rice germination stage, brown rice pre-germinated by soaking in a high-concentration Na2SeO3 solution, combined with ultrasonic stress, and germinated in two steps at high and low temperatures, activated the endogenous enzymes related to polyphenol synthesis in brown rice. The content of selenopeptides and selenoproteins in brown rice increased. These selenopeptides and selenoproteins can interact with enzymes related to the phenolic acid synthesis pathway in brown rice, further enhancing their activity, promoting the synthesis and accumulation of polyphenols in brown rice, and increasing the polyphenol content. Compared to the unstressed germination of Comparative Example 1, the high-voltage electrostatic field combined with ultrasonic treatment of Comparative Example 2, the Na2SeO3 solution soaking combined with ultrasonic treatment of Comparative Example 3, the Na2SeO3 solution soaking combined with high-voltage electrostatic field treatment of Comparative Example 4, and the conventional one-step germination method of Comparative Example 5, Example 2 used a two-step germination method combined with Na2SeO3 solution soaking, high-voltage electrostatic field, and ultrasonic stress treatments to exert a synergistic effect, highly activating the phenylpropane pathway and tyrosine pathway, inducing the efficient synthesis and accumulation of phenolic acid compounds. As can be seen from the comparison between Comparative Example 2 and Example 2, the selenium enrichment treatment of Na2SeO3 solution also has a synergistic effect on the accumulation of phenolic acid.

[0098] The organic selenium content in the germinated brown rice prepared in Examples 1-3 and Comparative Examples 1-5, as well as the brown rice prepared in Comparative Example 6 and the polished white rice prepared in Comparative Example 7, was determined, and the results are shown in Table 2. The organic and total selenium contents were determined according to the inductively coupled plasma mass spectrometry method in GB5009.93-2017 "National Food Safety Standard - Determination of Selenium in Food," using Agilent standard internal standard solution as a reference, to calculate the organic and total selenium contents in the germinated brown rice.

[0099] Table 2 Organic and total selenium content of germinated brown rice (μg / kg DW)

[0100] project Organic selenium Total selenium Example 1 120.34±9.53c 131.58±12.15c Example 2 175.50±7.23a 192.05±10.61a Example 3 151.24±10.59b 169.70±6.57b Comparative Example 1 42.23±5.67f 47.15±2.54f Comparative Example 2 41.54±2.35f 45.92±3.02f Comparative Example 3 94.18±10.24d 105.24±7.50d Comparative Example 4 65.34±4.71e 72.38±9.08e Comparative Example 5 93.26±3.58d 103.26±8.94d Comparative Example 6 39.23±3.29f 43.68±4.24f Comparative Example 7 10.27±0.84g 11.24±2.13g

[0101] Note: Different letters in each column indicate significant differences (p<0.05).

[0102] As shown in Table 2, the organic and total selenium contents were lowest in the polished white rice of Comparative Example 7, and also lower than 45 μg / kg DW in the brown rice of Comparative Example 6. Compared with Comparative Examples 1-7, the organic and total selenium contents of the germinated brown rice prepared under stress treatment in Examples 1-3 were significantly increased (p<0.05), with the organic selenium content reaching 89%-92%, indicating that most of the inorganic selenium was converted into organic selenium during the brown rice germination process. The germinated brown rice prepared in Example 2 had the highest organic selenium content, reaching 175.50 μg / kg DW. This was because the brown rice was treated with a high-voltage electrostatic field combined with a low-concentration Na2SeO3 solution during the pre-germination stage, which accelerated the absorption of water by the brown rice, significantly increasing the free water content and water activity, which was beneficial to the germination and growth of the brown rice embryo. 2- SeO3 is abundantly accumulated on the surface of brown rice grains, and its absorption efficiency is significantly enhanced through passive transport, forming selenopeptides or selenoproteins. During the brown rice germination stage, pre-germinated brown rice is soaked in a high-concentration Na2SeO3 solution, combined with ultrasonic stress, and germinated in two steps at high and low temperatures. The brown rice absorbs SeO3 through both active and passive absorption. 2- The content of selenopeptides and selenoproteins in brown rice further increased. Compared with the unstressed germination of Comparative Example 1, the high-voltage electrostatic field combined with ultrasonic treatment of Comparative Example 2, the Na2SeO3 solution soaking combined with ultrasonic treatment of Comparative Example 3, the Na2SeO3 solution soaking combined with high-voltage electrostatic field treatment of Comparative Example 4, and the conventional one-step germination method of Comparative Example 5, Example 2 adopted a two-step germination method combined with Na2SeO3 solution soaking, high-voltage electrostatic field, and ultrasonic stress treatments to exert a synergistic effect, which not only induced phenolic acid synthesis, but also significantly increased the organic selenium content in brown rice, thereby improving the efficiency of converting inorganic selenium to organic selenium in germinated brown rice.

[0103] To verify the effect of stress treatment on delaying starch digestion in germinated brown rice, the glycemic index (GI) of germinated brown rice prepared in Examples 1-3 and Comparative Examples 1-5, as well as brown rice prepared in Comparative Example 6 and refined white rice prepared in Comparative Example 7, was determined. The results are shown in Table 3. The glycemic index was determined using the Englyst method, with white bread as a reference, and the GI value of germinated brown rice was calculated.

[0104] Table 3. GI values ​​of germinated brown rice

[0105] project GI value Example 1 53.90±0.41e Example 2 50.67±0.60g Example 3 52.74±0.12f Comparative Example 1 67.33±0.34c Comparative Example 2 64.09±2.58d Comparative Example 3 62.84±0.63d Comparative Example 4 62.73±0.45d Comparative Example 5 63.47±1.28d Comparative Example 6 78.36±2.99b Comparative Example 7 89.00±1.56a

[0106] Note: Different letters in each column indicate significant differences (p<0.05).

[0107] As shown in Table 3, the GI value of polished white rice in Comparative Example 7 was as high as 89.00, significantly higher than that of brown rice, sprouted brown rice, and stress-treated sprouted brown rice (p<0.05), classifying it as a high-GI food. The GI value of unsprouted brown rice in Comparative Example 6 was 78.36, also significantly higher than that of sprouted brown rice. The GI values ​​of sprouted brown rice from Comparative Example 1 (unstressed sprouting), Comparative Example 2 (high voltage electrostatic field combined with ultrasonic treatment), Comparative Example 3 (Na2SeO3 solution soaking combined with ultrasonic treatment), Comparative Example 4 (Na2SeO3 solution soaking combined with high voltage electrostatic field treatment), and Comparative Example 5 (conventional one-step sprouting method) were significantly lower, reaching between 62.73 and 67.33. The two-step germination method, combined with stress treatments such as soaking in Na2SeO3 solution, high-voltage electrostatic field, and ultrasound, exerted a synergistic effect, further reducing the GI value of germinated brown rice. The GI values ​​of the germinated brown rice prepared in Examples 1-3 were all less than 55, classifying them as low-GI foods. The germinated brown rice prepared in Example 2 had the lowest GI value, at only 50.67. This is because the GI value of brown rice is significantly negatively correlated with the phenolic acid content. The polyhydroxyl groups in the phenolic acid structure can bind to digestive enzyme molecules, inhibiting the activity of α-amylase and amylase, thus slowing down the rate of starch hydrolysis. Stress treatment induced the accumulation of phenolic acids, thereby inhibiting starch digestion and reducing the GI value of germinated brown rice. Furthermore, the organic selenium in germinated brown rice mainly exists in the form of selenoproteins. Selenoproteins can form complexes with starch, leading to changes in starch conformation and properties, a reduction in amylase binding sites, and a decrease in starch digestibility and utilization.

[0108] The taste value and reactive oxygen species scavenging capacity (ORAC value) of the germinated brown rice prepared in Examples 1-3 and Comparative Examples 1-5, as well as the brown rice prepared in Comparative Example 6 and the polished white rice prepared in Comparative Example 7, were determined, and the results are shown in Table 4. The taste value was determined using a taste meter; the antioxidant activity was determined by fluorescence spectrophotometry, and the ORAC value of the germinated brown rice was calculated with water-soluble vitamin E (Trolox) as a reference.

[0109] Table 4. Taste and ORAC values ​​of germinated brown rice (μmol TE / g DW)

[0110]

[0111]

[0112] Note: Different letters in each column indicate significant differences (p<0.05).

[0113] As shown in Table 4, the palatability value of the polished white rice in Comparative Example 7 was the highest, while that of the brown rice in Comparative Example 6 was the lowest. Germination improved the palatability value of brown rice to some extent. The palatability value of the germinated brown rice prepared under stress treatment was further improved. The germinated brown rice prepared in Example 2 had the highest palatability value, comparable to that of the polished white rice in Comparative Example 7. Compared with Comparative Examples 1-5, the ORAC value of the germinated brown rice prepared under stress treatment in Examples 1-3 was significantly increased (p<0.05), and the ORAC value of the germinated brown rice prepared in Example 2 was the highest, reaching 28.79 μmol TE / g DW. The ORAC value of brown rice was significantly positively correlated with the content of phenolic acid and organic selenium.

[0114] The experimental results show that multiple stress treatment significantly increased the content of phenolic acids and organic selenium in germinated brown rice, enhanced the antioxidant activity of germinated brown rice, reduced the GI value of germinated brown rice, and improved the eating quality of germinated brown rice.

[0115] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing high-phenolic acid germinated brown rice, characterized in that, Includes the following steps: S1. Collect rice grains with intact germs as raw material for germination brown rice; S2. The brown rice raw material is acidified and washed to obtain acidified brown rice; S3. The acidified brown rice is soaked in Na2SeO3 solution and treated under a high voltage electrostatic field, then rinsed and drained to obtain pre-germinated brown rice; S4. Add Na2SeO3 solution to the pre-germinated brown rice, first perform high-temperature ultrasonic germination treatment, then perform low-temperature ultrasonic germination treatment, and then rinse and drain to obtain germinated brown rice. S5. The germinated brown rice is dried to obtain the high-phenolic acid germinated brown rice product; In step S3, the high-voltage electrostatic field process conditions are as follows: temperature is 18-25℃, arc-shaped electrode spacing is 6-10cm, and voltage is 30-60KV; In step S4, the temperature of the high-temperature ultrasonic germination treatment is 28-35℃, the relative humidity of the high-temperature ultrasonic germination treatment is 85-95%, and the ultrasonic power of the high-temperature ultrasonic germination treatment is 200-400W; The temperature of the low-temperature ultrasonic germination treatment is 18-25℃, the relative humidity of the low-temperature ultrasonic germination treatment is 90-98%, and the ultrasonic power of the low-temperature ultrasonic germination treatment is 50-200W. In step S4, the concentration of Na2SeO3 solution for high-temperature ultrasonic germination treatment is 15 mmol / L, and brown rice is ultrasonically treated for 8 min every 5 h during germination; the concentration of Na2SeO3 solution for low-temperature ultrasonic germination treatment is 8 mmol / L, and brown rice is ultrasonically treated for 12 min every 7 h during germination. The ratio of the concentration of the Na2SeO3 solution used in step S3 to the concentration of the Na2SeO3 solution used in the high-temperature ultrasonic germination in step S4 is 1:

5. The total duration of the high-temperature ultrasonic germination treatment is 30 hours, and the total duration of the low-temperature ultrasonic germination treatment is 72 hours.

2. The method for preparing high-phenolic acid germinated brown rice according to claim 1, characterized in that, In step S2, the acidification solution used for acidification treatment is acidic electrolyzed water with a pH of 5.5-6.0 and an effective chlorine concentration of 220-380 mg / L, and the treatment time is 10-20 min.

3. The method for preparing high-phenolic acid germinated brown rice according to claim 1, characterized in that, In step S5, the drying temperature is 32-40℃ and the drying wind speed is 2-8m / s.

4. A high-phenolic acid germinated brown rice obtained by the preparation method according to any one of claims 1-3.

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