Method for extracting rice starch

Abstract

The invention provides a method for extracting rice starch. The method comprises the following steps: adding alkaline electrolyzed water into rice flour, soaking to obtain rice flour slurry, and centrifuging to obtain supernate and precipitate; and scraping yellow substances on the upper layer of the precipitate, adding clear water into the remaining precipitate, and centrifuging to obtain the precipitate, namely the rice starch. According to the method, alkaline electrolyzed water is used as a solvent, and compared with traditional NaOH dilute alkali liquor extraction, the alkaline electrolyzed water has the high negative potential, the high reducing capacity, the high permeability, the certain dissolution characteristic and the certain extraction function, the alkaline electrolyzed water can enter cell gaps to dissolve rice glutelin, then starch is released, and starch extraction is promoted. Compared with a traditional dilute alkali method, a NaOH chemical reagent with high corrosivity is not used in extraction, the consumption of hydrochloric acid is reduced by 30-40%, and the effects of emission reduction, consumption reduction and environmental friendliness are achieved; the rice protein powder can be extracted at the same time by adjusting the pH value of the supernatant obtained by centrifugation with the method and performing centrifugal treatment.

Description

Technical Field

[0001] The invention relates to the technical field of rice starch extraction, in particular to a method for extracting rice starch. Background Art

[0002] Rice is one of the most important food crops in the world, and my country's total rice output ranks first in the world, with abundant rice resources. Therefore, the research on the comprehensive utilization of rice is of great significance, and rice starch is an important part of rice deep processing. Rice starch has low sensitivity, and compared with other starches, its particle size is smaller and the particle size distribution is narrow. It is widely used in the cosmetics and food industries. Rice starch can be used as a fat substitute for the production of ice cream, yogurt, salad dressing, etc. Therefore, extracting high-purity and high-quality rice starch has a positive effect on the development of the rice industry.

[0003] Rice is mainly composed of starch and a small amount of protein, lipid, fiber, minerals, vitamins and phenolic compounds, of which about 80% is starch, about 8% is protein, and 80% is alkali-soluble gluten. As the main component of rice, starch plays a decisive role in the quality of rice and rice products, and is the focus of rice product research. Rice starch extraction is the basis of rice starch research and application. Its extraction methods currently include dilute alkali solution extraction, enzyme extraction, surfactant extraction, ultrasonic-assisted extraction, etc. At present, dilute alkali solution extraction is the most widely used method in the industrial production of rice starch, but a large amount of wastewater will be generated during its production process, causing environmental pollution. At the same time, dilute alkali extraction will also introduce impurities such as sodium salt, which is not conducive to the quality of rice starch. Although the enzyme method and surfactant extraction have high extraction efficiency, their high cost limits their further application, and the surfactant extraction method will also bring about the problem of environmental pollution of rice starch. Ultrasonic-assisted extraction has high equipment requirements and large investment.

[0004] Electrolyzed water (EW), also known as electrolyzed ionized water or oxidized potential water, is produced by electrolyzing an electrolyte solution in an electrolysis chamber with a separation membrane (or diaphragm) between the anode and cathode electrodes. + and OH - , changing the pH value of the solution, so by changing the electrolysis time and electrolyte solution, electrolyzed water with different pH values ​​can be obtained. Alkaline electrolyzed water has low surface tension and strong permeability, and can be used as a good solvent. Its alkaline pH value is easy to restore to ordinary water with a pH value close to neutral, and it does not pollute the environment when discharged. However, there are no reports on the extraction of starch using alkaline electrolyzed water. Based on the above, a basic application is proposed. Summary of the invention

[0005] The purpose of the present invention is to use alkaline electrolyzed water to extract rice starch and recover protein in waste water at the same time, relying on the properties of alkaline electrolyzed water being cleaner and more environmentally friendly, inexpensive and easy to recover to ordinary water, so as to make the rice starch extraction technology cleaner and more environmentally friendly.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for extracting rice starch, comprising the following steps:

[0008] The rice is crushed by a crusher to obtain rice flour;

[0009] Adding alkaline electrolyzed water to rice flour, soaking the rice flour, and obtaining rice flour slurry;

[0010] The rice flour slurry is centrifuged and separated to obtain a supernatant and a precipitate;

[0011] Scrape off the yellow substance on the precipitate, add the remaining precipitate into clean water, adjust the pH to neutral, centrifuge, obtain the precipitate, and dry it to obtain starch.

[0012] Preferably, the pH of the alkaline electrolyzed water is 12.0 to 13.0;

[0013] And / or, the soaking temperature is 25-30° C. and the soaking time is 3-6 hours.

[0014] Preferably, in the step of adding alkaline electrolyzed water to the rice flour, 4 to 6 mL of alkaline electrolyzed water is added per gram of rice flour.

[0015] Preferably, the rice flour slurry is centrifuged and separated to obtain a supernatant and a precipitate; wherein the centrifugation temperature is 4 to 32° C., the centrifugation speed is 3000 to 5000 r / min, and the centrifugation time is 10 to 20 min.

[0016] Preferably, the rice flour slurry is centrifuged and separated to obtain a supernatant and a precipitate;

[0017] The pH value of the supernatant is adjusted to 5.0-6.0, and the mixture is centrifuged again. The supernatant is discarded, and the precipitate is taken and dried to obtain rice protein powder.

[0018] Preferably, the pH of the supernatant is adjusted to 5.0-6.0, and in the step of centrifugation again, the centrifugation temperature is 4-32°C, the centrifugation speed is 3000-5000 r / min, the centrifugation time is 10-20 min, and the pH of the supernatant is adjusted to 5.0-6.0 with hydrochloric acid, and the concentration of hydrochloric acid is 0.1-1 mol / L.

[0019] Preferably, the pH of the supernatant is adjusted to 5.0-6.0, centrifuged again, the supernatant is discarded, and in the step of taking the precipitate and drying, the drying temperature is 40-50° C. and the drying time is 18-24 h.

[0020] Preferably, the yellow substance on the upper layer of the precipitate is scraped off, and the remaining precipitate is added to clean water, and the pH is adjusted to neutral, centrifuged, and the precipitate is obtained. In the step of drying, the mass ratio of the added water to the rice flour is (6-10):1, hydrochloric acid is used to adjust the pH to neutral, the concentration of hydrochloric acid is 0.1-1 mol / L, the centrifugal temperature is 4-32° C., the centrifugal speed is 3000-5000 r / min, and the centrifugal time is 10-20 min.

[0021] Preferably, the yellow substance on the upper layer of the precipitate is scraped off, and the remaining precipitate is added to clean water, and the pH is adjusted to neutral, centrifuged, and the precipitate is obtained. In the drying step, the drying temperature is 35-45° C. and the drying time is 20-30 hours.

[0022] Preferably, the rice is ground and then sieved to obtain rice flour;

[0023] The mesh size of the sieve used for screening is 80 to 100 meshes.

[0024] A method for extracting rice starch of the present invention has the following beneficial effects compared with the prior art:

[0025] The method for extracting rice starch of the present invention uses alkaline electrolyzed water as a solvent. Compared with the traditional NaOH solution extraction, alkaline electrolyzed water contains a higher negative potential, so it has a stronger reducing ability, which is conducive to its entry into the intercellular space, and has strong permeability and certain dissolution characteristics and extraction functions. In addition, alkaline electrolyzed water can be restored to ordinary water, so it has less pollution to the environment. The preparation method of alkaline electrolyzed water is simple and low in price, which is more economical in production. Compared with the prior art, the method for extracting rice starch of the present invention can extract rice starch with a purity of 97.44%, and the molecular structure and particle morphology characteristics are not significantly different from the starch obtained by dilute alkali extraction; compared with the dilute alkali extraction, the present invention does not use the highly corrosive NaOH chemical reagent in the extraction process, and the amount of hydrochloric acid consumed in the extraction process is reduced by about 30-40%, which reduces the consumption of hydrochloric acid and can achieve the effects of energy saving, emission reduction and consumption reduction. At the same time, the method uses the supernatant obtained by centrifugation, and after adjusting the pH value and centrifugation, it can also extract and obtain rice protein powder at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is the appearance of starch and protein extracted in Examples 1 to 3 and Comparative Examples 1 to 2;

[0028] Figure 2 The XRD patterns of the rice starch obtained by extraction in Example 2 and Comparative Example 2;

[0029] Figure 3 The following are SEM images of rice starch extracted in Example 2 and Comparative Example 2. DETAILED DESCRIPTION

[0030] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values ​​within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any quoted numbers (fractions or integers) within the indicated range.

[0033] The present invention provides a method for extracting rice starch, comprising the following steps:

[0034] S1, after rice is crushed with a pulverizer, rice flour is obtained;

[0035] S2, add alkaline electrolyzed water into rice flour, soak, and obtain rice flour slurry;

[0036] S3, after the rice flour slurry is centrifuged, it is separated to obtain a supernatant and a precipitate;

[0037] S4. Scrape off the yellow substance on the upper layer of the precipitate, add the remaining precipitate into clean water, adjust the pH to neutral, centrifuge, obtain the precipitate, and dry it to obtain starch.

[0038] The method for extracting rice starch of the present invention uses alkaline electrolyzed water as a solvent. Compared with the traditional NaOH solution extraction, the alkaline electrolyzed water contains a higher negative potential, so it has a stronger reducing ability, which is conducive to its entry into the intercellular space, and has a strong permeability and certain dissolution characteristics and extraction function. In addition, the alkaline electrolyzed water can be restored to ordinary water, so the pollution to the environment is small. The preparation method of alkaline electrolyzed water is simple and low in price, and it is more economical in production. Compared with the prior art, the method for extracting rice starch of the present invention can extract rice starch with a purity of 97.44%, and the molecular structure and particle morphology characteristics are not significantly different from the starch obtained by alkaline extraction; compared with alkaline extraction, the present invention does not use the highly corrosive NaOH chemical reagent in the extraction process, and the amount of hydrochloric acid consumed in the extraction process is reduced by about 30-40%, which reduces the consumption of hydrochloric acid and can achieve the effects of energy saving, emission reduction and consumption reduction.

[0039] In some embodiments, the pH of the alkaline electrolyzed water is 12.0-13.0.

[0040] In some embodiments, alkaline electrolyzed water is prepared by an electrolytic cell. Specifically, a diaphragm is provided in the electrolytic cell, which divides the electrolytic cell into an anode cell and a cathode cell. An anode is provided in the anode cell, and a cathode is provided in the cathode cell. Both the anode and the cathode are inert electrodes, such as carbon rods. Pure water is added to the cathode cell, and a saturated KCl solution is added to the anode cell. The anode and the cathode are connected to a power source, and electrolysis is performed for a certain period of time to obtain alkaline electrolyzed water with a pH of 12.0 to 13.0.

[0041] In some embodiments, the soaking temperature is 25-30° C. and the soaking time is 3-6 hours.

[0042] In some embodiments, in the step of adding alkaline electrolyzed water to rice flour, 4-6 mL of alkaline electrolyzed water is added per g of rice flour.

[0043] In some embodiments, the rice flour slurry is centrifuged and separated to obtain a supernatant and a precipitate; wherein the centrifugation temperature is 4 to 32° C., the centrifugation speed is 3000 to 5000 r / min, and the centrifugation time is 10 to 20 min.

[0044] In some embodiments, the rice flour slurry is centrifuged and separated to obtain a supernatant and a precipitate;

[0045] The pH value of the supernatant is adjusted to 5.0-6.0, and the mixture is centrifuged again. The supernatant is discarded, and the precipitate is taken and dried to obtain rice protein powder.

[0046] In some embodiments, the pH of the supernatant is adjusted to 5.0-6.0. In the centrifugation step again, the centrifugation temperature is 4-32°C, the centrifugation speed is 3000-5000 r / min, the centrifugation time is 10-20 min, and the pH of the supernatant is adjusted to 5.0-6.0 with hydrochloric acid, and the concentration of hydrochloric acid is 0.1-1 mol / L.

[0047] In some embodiments, the pH of the supernatant is adjusted to 5.0-6.0, centrifuged again, the supernatant is discarded, and in the step of taking the precipitate and drying it, the drying temperature is 40-50° C. and the drying time is 18-24 hours.

[0048] In some embodiments, the yellow substance on the upper layer of the precipitate (specifically impurities such as rice protein) is scraped off, and the remaining precipitate is added to clean water, and the pH is adjusted to neutral, centrifuged, and the precipitate is obtained. In the step of drying, the mass ratio of the added water to the rice flour is (6-10):1, hydrochloric acid is used to adjust the pH to neutral, the concentration of hydrochloric acid is 0.1-1 mol / L, the centrifugation temperature is 4-32°C, the centrifugation speed is 3000-5000 r / min, and the centrifugation time is 10-20 min.

[0049] In some embodiments, the yellow substance on the upper layer of the precipitate (specifically impurities such as rice protein) is scraped off, and the remaining precipitate is added to clean water, and the pH is adjusted to neutral, centrifuged, and the precipitate is obtained. In the drying step, the drying temperature is 35-45° C. and the drying time is 20-30 hours.

[0050] In some embodiments, the rice is crushed by a crusher and then sieved, and the sieved material is taken to obtain rice flour;

[0051] The mesh size of the sieve used for screening is 80 to 100 meshes.

[0052] The method for extracting rice starch of the present application is further described below with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. If not specifically stated, the technical means adopted in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0053] Example 1

[0054] The present invention provides a method for extracting rice starch, comprising the following steps:

[0055] S1, after rice is crushed with a pulverizer, the sieve is taken to obtain rice flour; the mesh number of the sieve used for sieving is 100 mesh;

[0056] S2, in 10g rice flour, add 40mL pH to the alkaline electrolyzed water of 13.0, soak 4h at 30 ℃, obtain rice flour slurry; Alkaline electrolyzed water is prepared by electrolyzer, and diaphragm is provided in electrolyzer, and diaphragm divides electrolyzer into anode pool and cathode pool by diaphragm, anode is provided in anode pool, cathode is provided in cathode pool, anode and cathode are inert electrode carbon rods, pure water is added in cathode pool, saturated KCl solution is added in anode pool, anode and cathode are connected to power supply, and electrolysis obtains the alkaline electrolyzed water that pH is 13.0;

[0057] S3, the rice flour slurry is placed in a centrifuge tube, centrifuged using a high-speed centrifuge, separated to obtain a supernatant and a precipitate; wherein the centrifugation temperature is 4 ° C, the speed is 4000r / min, and the time is 10min;

[0058] S4, the supernatant obtained in S3, using 1mol / L HCl solution to adjust pH to 5.5, centrifuged again, discarded the supernatant, precipitated and dried to obtain rice protein powder; wherein, the centrifugation temperature was 4 ° C, the rotating speed was 4000r / min, and the time was 10min; the drying temperature was 40 ° C, and the time was 24h;

[0059] S5, scrape off the yellow substance on the upper precipitate obtained in S3, the remaining precipitate is added in clear water (based on the initial rice flour mass, the addition of water is 8 times the initial rice flour mass), stir, use 1mol / L HCl solution to adjust pH to neutrality, discard the supernatant after centrifugation, obtain precipitation, place in a forced air drying oven, dry at 40 ℃ for 24h, and obtain starch; wherein, the centrifugation temperature is 4 ℃, the rotating speed is 4000r / min, and the time is 10min.

[0060] It was determined that the purity of the rice starch extracted according to the method in Example 1 was 97.44%, and the purity of the rice protein powder was 70.06%.

[0061] Example 2

[0062] The present invention provides a method for extracting rice starch, comprising the following steps:

[0063] S1, after rice is crushed with a pulverizer, the sieve is taken to obtain rice flour; the mesh number of the sieve used for sieving is 100 mesh;

[0064] S2, in 10g rice flour, add 40mL pH to the alkaline electrolyzed water of 12.8, soak 4h at 30 ℃, obtain rice flour slurry; Alkaline electrolyzed water is prepared by electrolyzer, and diaphragm is provided in electrolyzer, and diaphragm divides electrolyzer into anode pool and cathode pool by diaphragm, anode is provided in anode pool, cathode is provided in cathode pool, anode and cathode are inert electrode carbon rods, pure water is added in cathode pool, saturated KCl solution is added in anode pool, anode and cathode are connected to power supply, and electrolysis obtains the alkaline electrolyzed water that pH is 12.8;

[0065] S3, the rice flour slurry is placed in a centrifuge tube, centrifuged using a high-speed centrifuge, separated to obtain a supernatant and a precipitate; wherein the centrifugation temperature is 4 ° C, the speed is 4000r / min, and the time is 10min;

[0066] S4, the supernatant obtained in S3, using 1mol / L HCl solution to adjust pH to 5.5, centrifuged again, discarded the supernatant, precipitated and dried to obtain rice protein powder; wherein, the centrifugation temperature was 4 ° C, the rotating speed was 4000r / min, and the time was 10min; the drying temperature was 40 ° C, and the time was 24h;

[0067] S5, scrape off the yellow substance on the upper precipitate obtained in S3, the remaining precipitate is added in clear water (based on the initial rice flour mass, the addition of water is 8 times the initial rice flour mass), stir, use 1mol / L HCl solution to adjust pH to neutrality, discard the supernatant after centrifugation, obtain precipitation, place in a forced air drying oven, dry at 40 ℃ for 24h, and obtain starch; wherein, the centrifugation temperature is 4 ℃, the rotating speed is 4000r / min, and the time is 10min.

[0068] It was determined that the purity of the rice starch extracted according to the method in Example 2 was 95.83%, and the purity of the rice protein powder was 69.08%.

[0069] Example 3

[0070] The present invention provides a method for extracting rice starch, comprising the following steps:

[0071] S1, after rice is crushed with a pulverizer, the sieve is taken to obtain rice flour; the mesh number of the sieve used for sieving is 100 mesh;

[0072] S2, in 10g rice flour, add 40mLpH to the alkaline electrolyzed water of 12.8, soak 3h at 30 ℃, obtain rice flour slurry; Alkaline electrolyzed water is prepared by electrolyzer, and diaphragm is provided in electrolyzer, and diaphragm divides electrolyzer into anode pool and cathode pool by diaphragm, anode is provided in anode pool, cathode is provided in cathode pool, anode and cathode are inert electrode carbon rods, pure water is added in cathode pool, saturated KCl solution is added in anode pool, anode and cathode are connected to power supply, and electrolysis obtains the alkaline electrolyzed water that pH is 12.8;

[0073] S3, the rice flour slurry is placed in a centrifuge tube, centrifuged using a high-speed centrifuge, separated to obtain a supernatant and a precipitate; wherein the centrifugation temperature is 4 ° C, the speed is 4000r / min, and the time is 10min;

[0074] S4, the supernatant obtained in S3, using 1mol / L HCl solution to adjust pH to 5.5, centrifuged again, discarded the supernatant, precipitated and dried to obtain rice protein powder; wherein, the centrifugation temperature was 4 ° C, the rotating speed was 4000r / min, and the time was 10min; the drying temperature was 40 ° C, and the time was 24h;

[0075] S5, scrape off the yellow substance on the upper precipitate obtained in S3, the remaining precipitate is added in clear water (based on the initial rice flour mass, the addition of water is 8 times the initial rice flour mass), stir, use 1mol / L HCl solution to adjust pH to neutrality, discard the supernatant after centrifugation, obtain precipitation, place in a forced air drying oven, dry at 40 ℃ for 24h, and obtain starch; wherein, the centrifugation temperature is 4 ℃, the rotating speed is 4000r / min, and the time is 10min.

[0076] It was determined that the purity of the rice starch extracted according to the method in Example 3 was 94.49%, and the purity of the rice protein powder was 60.45%.

[0077] Comparative Example 1

[0078] This comparative example provides a method for extracting rice starch, which is the same as Example 2, except that a 0.3% NaOH aqueous solution is used to extract starch and protein, and specifically comprises the following steps:

[0079] S1, after rice is crushed with a pulverizer, the sieve is taken to obtain rice flour; the mesh number of the sieve used for sieving is 100 mesh;

[0080] S2, to 10g rice flour, add 40mL mass concentration is 0.3% NaOH aqueous solution, soak at 30 ℃ for 4h, obtain rice flour slurry;

[0081] S3, the rice flour slurry is placed in a centrifuge tube, centrifuged using a high-speed centrifuge, separated to obtain a supernatant and a precipitate; wherein the centrifugation temperature is 4 ° C, the speed is 4000r / min, and the time is 10min;

[0082] S4, the supernatant obtained in S3, using 1mol / L HCl solution to adjust pH to 5.5, centrifuged again, discarded the supernatant, precipitated and dried to obtain rice protein powder; wherein, the centrifugation temperature was 4 ° C, the rotating speed was 4000r / min, and the time was 10min; the drying temperature was 40 ° C, and the time was 24h;

[0083] S5, scrape off the yellow substance on the upper precipitate obtained in S3, the remaining precipitate is added in clear water (based on the initial rice flour mass, the addition of water is 8 times the initial rice flour mass), stir, use 1mol / L HCl solution to adjust pH to neutrality, discard the supernatant after centrifugation, obtain precipitation, place in a forced air drying oven, dry at 40 ℃ for 24h, and obtain starch; wherein, the centrifugation temperature is 4 ℃, the rotating speed is 4000r / min, and the time is 10min.

[0084] It was determined that the purity of rice starch extracted by the method in Comparative Example 1 was 97.94%, and the purity of rice protein powder was 70.01%. Compared with Example 2, the extraction rate of rice starch and rice protein powder in Comparative Example 1 was slightly higher, and the purity of the sample extracted was also slightly higher, but there was no obvious difference.

[0085] Comparative Example 2

[0086] This comparative example provides a method for extracting rice starch, which is the same as Example 3, except that a 0.3% NaOH aqueous solution is used to extract starch and protein, and specifically comprises the following steps:

[0087] S1, after rice is crushed with a pulverizer, the sieve is taken to obtain rice flour; the mesh number of the sieve used for sieving is 100 mesh;

[0088] S2, to 10g rice flour, add 40mL mass concentration is 0.3% NaOH aqueous solution, soak at 30 ℃ for 3h, obtain rice flour slurry;

[0089] S3, the rice flour slurry is placed in a centrifuge tube, centrifuged using a high-speed centrifuge, separated to obtain a supernatant and a precipitate; wherein the centrifugation temperature is 4 ° C, the speed is 4000r / min, and the time is 10min;

[0090] S4, the supernatant obtained in S3, using 1mol / L HCl solution to adjust pH to 5.5, centrifuged again, discarded the supernatant, precipitated and dried to obtain rice protein powder; wherein, the centrifugation temperature was 4 ° C, the rotating speed was 4000r / min, and the time was 10min; the drying temperature was 40 ° C, and the time was 24h;

[0091] S5, scrape off the yellow substance on the precipitate obtained in S3, the remaining precipitate is added in clear water (based on the initial rice flour mass, the addition of water is 8 times of the initial rice flour mass), stir, use 1mol / L HCl solution to adjust pH to neutrality, discard the supernatant after centrifugation, obtain precipitation, place in a forced air drying oven, dry at 40 ℃ for 24h, and obtain starch; wherein, the centrifugation temperature is 4 ℃, the rotating speed is 4000r / min, and the time is 10min.

[0092] It was determined that the purity of rice starch extracted according to the method in Comparative Example 2 was 96.92%, and the purity of rice protein powder was 68.97%. Compared with Example 3, the extraction rates of rice starch and rice protein powder in Comparative Example 2 were slightly higher, but there was no significant difference.

[0093] Performance Testing

[0094] Rice starch color

[0095] The rice starch color test method is as follows: after starch is extracted according to the method in Examples 1 to 3 and Comparative Examples 1 to 2, the extracted starch is ground and passed through a 100-mesh sieve, and then placed in a clean, transparent plastic bag. After the colorimeter (CM-5 colorimeter) is calibrated, the chromaticity of 5 kinds of rice starch extracted by different treatments is determined, and the L*, a*, and b* values ​​are recorded. The results are shown in Table 1.

[0096] Table 1-Color of starch extracted from different examples

[0097] Example L* a* b* Example 1 97.50±0.20 0.33±0.06 2.60±0.01 Example 2 97.87±0.15 0.17±0.06 2.77±0.06 Example 3 97.63±0.12 0.20±0.01 2.50±0.26 Comparative Example 1 98.00±0.26 0.10±0.02 3.50±0.17 Comparative Example 2 97.43±0.21 0.13±0.06 3.53±0.15

[0098] Note: In Table 1, L* indicates the brightness of the sample. The larger the L* value, the whiter the sample color, and vice versa. a* indicates the red-green value of the sample. When a* is a negative value, the smaller the value, the greener the sample color. When a* is a positive value, the larger the value, the redder the sample color. b* indicates the yellow-blue value of the sample. When b* is a negative value, the smaller the value, the bluer the sample color. When b* is a positive value, the larger the value, the yellower the sample color.

[0099] As can be seen from Table 1, there is no obvious difference in the L* value between the rice starch prepared in Examples 1 to 3 and the rice starch prepared in Comparative Examples 1 to 2, indicating that there is no significant difference in whiteness; the b* value of the rice starch prepared in Examples 1 to 3 is slightly lower than that of the rice starch prepared in 1 to 2, indicating that the yellowness of the rice starch prepared by alkaline electrolyzed water will be reduced and the color will be better.

[0100] Appearance of rice starch and rice protein powder

[0101] In Examples 1 to 3 and Comparative Examples 1 to 2, starch and rice protein powder were extracted as follows: Figure 1 shown.

[0102] Figure 1 A is the rice starch extracted in Example 1, and A′ is the rice protein powder extracted in Example 1; B is the rice starch extracted in Example 2, and B′ is the rice protein powder extracted in Example 2; C is the rice starch extracted in Example 3, and C′ is the rice protein powder extracted in Example 3; E is the rice starch extracted in Comparative Example 1, and E′ is the rice protein powder extracted in Comparative Example 1; F is the rice starch extracted in Comparative Example 2, and F′ is the rice protein powder extracted in Comparative Example 2.

[0103] from Figure 2 It can be seen that the rice starch and rice protein powder prepared in Examples 1 to 3 and the rice starch and rice protein powder prepared in Comparative Examples 1 to 2 have no significant difference in appearance.

[0104] Rice starch structure and morphology

[0105] Taking the rice starch extracted in Example 2 and Comparative Example 2 as an example, the microstructure was observed by SEM and XRD detection was performed. The XRD detection conditions were: copper target, tube voltage 40 kV, current 10 mA, step size 0.01°, and diffraction angle (2θ) scanning range 4-40°.

[0106] Figure 2 The XRD patterns of the rice starch extracted in Example 2 and Comparative Example 2 are as follows: Figure 3 The following are SEM images of rice starch extracted in Example 2 and Comparative Example 2.

[0107] Figures 2-3 AEW represents the rice starch extracted in Example 2 (immersion in alkaline electrolyzed water), and EW represents the rice starch extracted in Comparative Example 1 (immersion in dilute NaOH solution).

[0108] X-ray diffraction (XRD) can detect the crystal structure of starch through the scattering properties of X-rays. When X-rays are irradiated onto starch granules, these crystal structures will scatter the X-rays at specific angles due to the different crystal structures inside the starch granules, such as the different arrangements of amylose and amylopectin. By measuring the angles and intensities of these scatterings, information about the crystal structure of starch can be obtained. Different types of starch (such as type A, type B, and type C) appear differently in the XRD spectrum, which can help distinguish different types of starch. In addition, the processing method of starch will also affect its crystal structure, which in turn affects the characteristics of its XRD spectrum. In short, XRD is a tool used to study the crystal structure and properties of starch. By analyzing the XRD spectrum, detailed information about the crystal structure of starch can be obtained, which is crucial for understanding the functional properties of starch and improving its processing applications.

[0109] from Figures 2-3 It can be seen that there is no significant difference in microscopic morphology between the rice starch obtained by alkaline electrolyzed water extraction and the rice starch obtained by extraction with a mass concentration of 0.3% NaOH aqueous solution. From the XRD diagram, it can be seen that the starch obtained by extraction in Comparative Example 1 and the starch obtained by extraction in Example 2 have strong crystallization peaks at 15.19°, 17.00°, 18.30°, 22.71° and 15.22°, 17.00°, 18.30°, 22.71°, respectively, which are typical A-type starches, and the crystallinity of the two is 20.03±0.83 and 21.73±0.73, respectively, and there is no significant difference between the two. The above results show that there is no significant difference in microscopic morphology and structure between the rice starch obtained by extraction with alkaline electrolyzed water and the rice starch obtained by extraction with 0.3% NaOH.

[0110] HCl dosage during extraction

[0111] The volume (mL) of HCl (1 mol / L) consumed during starch extraction and protein recovery in the methods of Examples 1 to 3 and Comparative Examples 1 to 2 (i.e., the total volume of HCl consumed in steps S4 and S5) is shown in Table 2 below.

[0112] Table 2- Total volume of HCl (1 mol / L) consumed during extraction in different embodiments

[0113] Example Consumed HCl (1 mol / L) volume (mL) Example 1 2.10 Example 2 1.98 Example 3 1.66 Comparative Example 1 2.54 Comparative Example 2 3.34

[0114] It can be seen from Table 2 above that the amount of HCl used in the extraction process of Examples 1 to 3 is significantly reduced compared with the amount of HCl used in the extraction process of Comparative Examples 1 to 2, and the average amount of HCl used is relatively reduced by 35.03% compared with Comparative Examples 1 to 2. The pH value of the aqueous solution with a mass concentration of 0.3% NaOH is about 12.88, which is close to the pH value of the alkaline electrolyzed water used in Examples 1 to 3. It can be seen that when the pH value is similar, the HCl consumed by the alkaline electrolyzed water in the extraction process is greatly reduced, reducing the amount of solvent used, making the extraction process cleaner and environmentally friendly.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting rice starch, characterized in that, The following steps are involved: The rice is crushed by a crusher to obtain rice flour; Adding alkaline electrolyzed water to rice flour, soaking the rice flour at a certain temperature for a certain time, and obtaining rice flour slurry; The rice flour slurry is centrifuged and separated to obtain a supernatant and a precipitate; Scrape off the yellow substance on the top of the precipitate, add the remaining precipitate into clean water, adjust the pH to neutral, centrifuge, obtain the precipitate, dry, crush and sieve to obtain starch.

2. The method for extracting rice starch as claimed in claim 1, wherein The pH of the alkaline electrolyzed water is 12.0 to 13.0; And / or, the soaking temperature is 25-30° C. and the soaking time is 3-6 hours.

3. The method for extracting rice starch as claimed in claim 1, wherein In the step of adding alkaline electrolyzed water to the rice flour, 4 to 6 mL of alkaline electrolyzed water is added per gram of rice flour.

4. The method for extracting rice starch as claimed in claim 1, wherein The rice flour slurry soaked in alkaline electrolyzed water is centrifuged and separated to obtain a supernatant and a precipitate; wherein the centrifugal temperature is 4-32° C., the centrifugal speed is 3000-5000 r / min, and the centrifugal time is 10-20 min.

5. The method for extracting rice starch as claimed in claim 1, wherein The rice flour slurry is centrifuged and separated to obtain a supernatant and a precipitate; The pH value of the supernatant is adjusted to 5.0-6.0, and the mixture is centrifuged again. The supernatant is discarded, and the precipitate is taken and dried to obtain rice protein powder.

6. The method for extracting rice starch as claimed in claim 5, characterized in that, The pH value of the supernatant is adjusted to 5.0-6.

0. In the step of centrifugation again, the centrifugation temperature is 4-32°C, the centrifugation speed is 3000-5000 r / min, the centrifugation time is 10-20 min, and the pH value of the supernatant is adjusted to 5.0-6.0 with hydrochloric acid, and the concentration of the hydrochloric acid is 0.1-1 mol / L.

7. The method for extracting rice starch as claimed in claim 5, characterized in that, The pH value of the supernatant is adjusted to 5.0-6.0, and the mixture is centrifuged again. The supernatant is discarded, and in the step of taking the precipitate and drying it, the drying temperature is 40-50° C. and the drying time is 18-24 hours.

8. The method for extracting rice starch as claimed in claim 1, wherein The yellow substance on the precipitate is scraped off, and the remaining precipitate is added into clean water, and the pH is adjusted to neutral, centrifuged, and the precipitate is obtained. In the step of drying, the mass ratio of the added water to the rice flour is (6-10):1, hydrochloric acid is used to adjust the pH to neutral, the concentration of hydrochloric acid is 1-2 mol / L, the centrifugal temperature is 4-32° C., the centrifugal speed is 3000-5000 r / min, and the centrifugal time is 10-20 min.

9. The method for extracting rice starch as claimed in claim 1, wherein Scrape off the yellow substance on the upper layer of the precipitate, add clean water to the remaining precipitate, adjust the pH to neutral, centrifuge, obtain the precipitate, and in the drying step, the drying temperature is 35-45° C. and the drying time is 20-30 h.

10. The method for extracting rice starch as claimed in claim 1, characterized in that, Grind the rice and sieve it, and take the sieved material to obtain rice flour; The mesh size of the sieve used for screening is 80 to 100 meshes.

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