阅读说明：本技术 一种高乳化性脱镉米渣蛋白及其酸沉淀方法 (High-emulsibility cadmium-removed rice residue protein and acid precipitation method thereof ) 是由 赵强 游洋 熊华 刘欢 谢明勇 饶世平 刘胜国 于 2021-08-04 设计创作，主要内容包括：本发明公开了一种高乳化性脱镉米渣蛋白及其酸沉淀方法,属于大米产品加工技术领域,本发明以米渣为原料,经原料预处理、脱脂、酶解、灭酶、碱提、酸沉、干燥等步骤制备。本发明所得产品米渣蛋白的乳化性得到改善,镉含量远低于国家标准中食品中镉的限量,能够大幅提升米渣副产物的附加值,且操作简单,绿色环保,成本低,适合在食品工业生产中使用。(The invention discloses a high-emulsibility cadmium-removed rice residue protein and an acid precipitation method thereof, belonging to the technical field of rice product processing. The emulsibility of the rice residue protein obtained by the invention is improved, the cadmium content is far lower than the limit of cadmium in food in national standard, the added value of the rice residue by-product can be greatly improved, the operation is simple, the method is green and environment-friendly, the cost is low, and the method is suitable for being used in food industrial production.)

1. An acid precipitation method for high-emulsibility cadmium-removed rice residue protein is characterized by comprising the following steps:

(1) pretreatment of raw materials: removing impurities from rice residue, pulverizing, and sieving to obtain sieved rice residue;

(2) degreasing: adding n-hexane into the sieved rice residue obtained in the step (1), degreasing, and volatilizing to obtain degreased rice residue;

(3) enzymolysis: adding water into the degreased rice dregs obtained in the step (2), adjusting the temperature and the pH, adding high-temperature alpha-amylase, and performing enzymolysis to obtain an enzymolysis dispersion liquid;

(4) enzyme deactivation: adjusting the pH value of the enzymolysis dispersion liquid obtained in the step (3), and performing enzyme deactivation treatment to obtain enzyme deactivation mixed liquid;

(5) alkali extraction: cooling the enzyme-deactivated mixed solution obtained in the step (4), stirring, adding a sodium hydroxide solution, adjusting the pH, carrying out alkali extraction, centrifuging, and taking supernatant;

(6) acid precipitation: adding a citric acid solution into the supernatant obtained in the step (5), adjusting the pH, standing, centrifuging, and taking a precipitate;

(7) and (3) drying: dialyzing the precipitate obtained in the step (6), and carrying out vacuum freeze drying to obtain the high-emulsibility cadmium-removed rice residue protein.

2. The acid precipitation method according to claim 1,

in the step (1), the crushing and sieving is to crush rice residues and then sieve the crushed rice residues with a sieve of 60-120 meshes.

3. The acid precipitation method according to claim 1,

in the step (2), 5-10 ml of n-hexane is added into every 1g of sieved rice residues; preferably, 8-10 ml of n-hexane is added into every 1g of sieved rice residues;

in the step (2), the degreasing time is 2 h.

4. The acid precipitation method according to claim 1,

in the step (3), 10-20 ml of water is added into every 1g of degreased rice residues;

in the step (3), the temperature is adjusted to 90-95 ℃, and the pH is adjusted to 6.0-7.0;

in the step (3), the addition amount of the high-temperature alpha-amylase is 0.05-0.1% of the mass of the degreased rice residues;

in the step (3), the enzymolysis time is 1-2 h.

5. The acid precipitation method according to claim 1,

in the step (4), the pH is adjusted to 9.0-10.0.

6. The acid precipitation method according to claim 1,

in the step (5), the concentration of the sodium hydroxide solution is 0.5-1 mol/L;

in the step (5), the pH is adjusted to 11.0-12.0, stirring is carried out for 3 hours, and alkali extraction is carried out.

7. The acid precipitation method according to claim 1,

in the step (6), the concentration of the citric acid solution is 0.5-1 mol/L;

in the step (6), adjusting the pH value to 4.5-5.0;

in the step (6), the standing time is 0.5-1 h.

8. The acid precipitation method according to claim 1,

in the steps (5) to (6), the rotation speed of the centrifugation is 4000 to 5000rpm, and the time of the centrifugation is 15 to 20 min.

9. The acid precipitation method according to claim 1,

in the step (7), the dialysis temperature is 4 ℃, and the dialysis time is 72 hours;

in the step (7), the temperature of the vacuum freeze drying is-40 ℃ to-50 ℃.

10. The high-emulsifiability cadmium-removed rice residue protein produced by the method of any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of rice product processing, in particular to high-emulsibility cadmium-removed rice residue protein and an acid precipitation method thereof.

Background

The quality of the rice protein is known to be the best in the cereal protein, the rice protein has high nutritive value, can be comparable with eggs, cow milk and beef, and is an important protein source of daily diet of people. The rice protein mainly comprises albumin, globulin, alcohol-soluble protein and glutelin, is low-antigen protein, does not produce anaphylactic reaction and is very favorable for producing infant food. The rice protein not only has unique nutrition function, but also has other health care functions, and recent research shows that the rice protein can reduce the content of serum cholesterol. The rice protein is rich in essential amino acids, the content of the first limiting amino acid lysine is higher than that of other cereals, and the amino acid composition mode is close to the recommended mode of WHO/FAO, so that the rice protein is easy to digest and absorb by human bodies. Compared with other cereal proteins, the rice protein has higher Biological Value (BV) and protein utilization rate (PER), the biological value can reach 77, the rice protein provides a high-quality protein resource for the food industry, and the nutritional value of the rice protein is irreplaceable.

Rice residue protein resources in China are rich, and 1 ton of rice residue is generated when 7 tons of rice are consumed in starch sugar production. The research on the rice residue protein and the product development thereof not only can fully utilize the rice protein resource, but also are beneficial to improving the economic benefit of starch sugar production enterprises. The rice residue protein is a byproduct of rice flour liquefaction or saccharification when early glaze rice or broken rice is used as a raw material to produce starch sugar or fermentation to produce glutamic acid, citric acid, lactic acid and biochemical drugs. The rice residue is the residue obtained by liquefying rice flour by high-temperature amylase and filtering by a plate frame to remove partial carbohydrate, the protein content is about 50 percent, and the rice residue protein has all the advantages of the rice protein, such as: reasonable amino acid composition, mild taste, low allergy, low cholesterol, etc. However, the heavy metal cadmium content in the rice residue protein is high, so that the processing and the reutilization of the rice residue protein are greatly restricted.

Disclosure of Invention

In order to solve the technical problems, the invention provides the high-emulsibility cadmium-removed rice residue protein and the acid precipitation method thereof, solves the problem of overhigh cadmium content of the rice residue protein, and is a preparation method of the high-emulsibility rice residue protein, which has high application value, simple operation, environmental protection and lower cost.

The invention provides an acid precipitation method of cadmium-removed rice residue protein with high emulsibility, which comprises the following steps:

(1) pretreatment of raw materials: removing impurities from rice residue, pulverizing, and sieving to obtain sieved rice residue;

(2) degreasing: adding n-hexane into the sieved rice residue obtained in the step (1), degreasing, and volatilizing to obtain degreased rice residue;

(3) enzymolysis: adding water into the degreased rice dregs obtained in the step (2), adjusting the temperature and the pH, adding high-temperature alpha-amylase, and performing enzymolysis to obtain an enzymolysis dispersion liquid;

(4) enzyme deactivation: adjusting the pH value of the enzymolysis dispersion liquid obtained in the step (3), and performing enzyme deactivation treatment to obtain enzyme deactivation mixed liquid;

(5) alkali extraction: cooling the enzyme-deactivated mixed solution obtained in the step (4), stirring, adding a sodium hydroxide solution, adjusting the pH, carrying out alkali extraction, centrifuging, and taking supernatant;

(6) acid precipitation: adding a citric acid solution into the supernatant obtained in the step (5), adjusting the pH, standing, centrifuging, and taking a precipitate;

(7) and (3) drying: dialyzing the precipitate obtained in the step (6), and carrying out vacuum freeze drying to obtain the high-emulsibility cadmium-removed rice residue protein.

Further, in the above-mentioned case,

in the step (1), the crushing and sieving is to crush rice residues and then sieve the crushed rice residues with a sieve of 60-120 meshes.

Further, in the above-mentioned case,

in the step (2), 5-10 ml of n-hexane is added into every 1g of sieved rice residues; preferably, 8-10 ml of n-hexane is added into every 1g of sieved rice residues;

in the step (2), the degreasing time is 2 h.

Further, in the above-mentioned case,

in the step (3), 10-20 ml of water is added into every 1g of degreased rice residues;

in the step (3), the temperature is adjusted to 90-95 ℃, and the pH is adjusted to 6.0-7.0;

in the step (3), the addition amount of the high-temperature alpha-amylase is 0.05-0.1% of the mass of the degreased rice residues;

in the step (3), the enzymolysis time is 1-2 h.

Further, in the above-mentioned case,

in the step (4), the pH is adjusted to 9.0-10.0.

Further, in the above-mentioned case,

in the step (5), the concentration of the sodium hydroxide solution is 0.5-1 mol/L;

in the step (5), the pH is adjusted to 11.0-12.0, stirring is carried out for 3 hours, and alkali extraction is carried out.

Further, in the above-mentioned case,

in the step (6), the concentration of the citric acid solution is 0.5-1 mol/L;

in the step (6), adjusting the pH value to 4.5-5.0;

in the step (6), the standing time is 0.5-1 h.

Further, in the above-mentioned case,

in the steps (5) to (6), the rotation speed of the centrifugation is 4000 to 5000rpm, and the time of the centrifugation is 15 to 20 min.

Further, in the above-mentioned case,

in the step (7), the dialysis temperature is 4 ℃, and the dialysis time is 72 hours;

in the step (7), the temperature of the vacuum freeze drying is-40 ℃ to-50 ℃.

The invention also provides the high-emulsibility cadmium-removed rice residue protein prepared by any one of the preparation methods.

The invention has the following advantages:

the preparation method provided by the invention has the advantages of high application value, simple operation, environmental protection and low cost, can improve the emulsibility of the rice residue protein, and solves the problem of overhigh cadmium content of the rice residue protein. The method can remove more than 90 percent of cadmium, the cadmium content of the rice residue protein is lower than 0.1mg/kg and far lower than the limit of cadmium in food specified in national standard, the problem that the rice residue protein is too high in cadmium content and is not suitable for eating can be effectively solved, and the yield, the purity and the protein emulsibility of the rice residue protein are improved, so that the method is suitable for large-scale popularization and application.

Detailed Description

In the following, the technical solutions in the embodiments of the present invention will be clearly and completely described, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The starting materials, reagents or apparatuses used in the following examples are conventionally commercially available or can be obtained by conventionally known methods, unless otherwise specified. The method is a conventional method, and all the methods are conventional methods unless otherwise specified.

An embodiment of the invention provides an acid precipitation method for high-emulsibility cadmium-removed rice residue protein, which comprises the following steps:

(1) pretreatment of raw materials: removing impurities from rice residue, pulverizing, and sieving to obtain sieved rice residue;

(2) degreasing: adding n-hexane into the sieved rice residue obtained in the step (1), degreasing, and volatilizing to obtain degreased rice residue;

(3) enzymolysis: adding water into the degreased rice dregs obtained in the step (2), adjusting the temperature and the pH, adding high-temperature alpha-amylase, and performing enzymolysis to obtain an enzymolysis dispersion liquid;

(4) enzyme deactivation: adjusting the pH value of the enzymolysis dispersion liquid obtained in the step (3), and performing enzyme deactivation treatment to obtain enzyme deactivation mixed liquid;

(5) alkali extraction: cooling the enzyme-deactivated mixed solution obtained in the step (4), stirring, adding a sodium hydroxide solution, adjusting the pH, carrying out alkali extraction, centrifuging, and taking supernatant;

(6) acid precipitation: adding a citric acid solution into the supernatant obtained in the step (5), adjusting the pH, standing, centrifuging, and taking a precipitate;

(7) and (3) drying: dialyzing the precipitate obtained in the step (6), and carrying out vacuum freeze drying to obtain the high-emulsibility cadmium-removed rice residue protein.

The invention adopts the synergistic effect of the restrictive hydrolysis and the citric acid precipitation, the citric acid is complexed with the cadmium in the rice residue, the cadmium in the rice residue can be removed to a greater extent in the acid precipitation process to prepare the rice residue protein with lower cadmium content, the residual starch in the raw material rice residue is removed by the restrictive enzymolysis of the high-temperature alpha-amylase, the protein in the rice residue is enriched, the yield and the purity of the rice residue protein are improved, and the emulsibility of the prepared rice residue protein is improved.

In one embodiment of the present invention, in the step (1), the pulverizing and sieving process includes: and (3) crushing the rice residues, and sieving the crushed rice residues with a 60-120-mesh sieve.

In one embodiment of the invention, in the step (1), the impurity removal is to mechanically remove impurities from the rice residue.

In one embodiment of the invention, in the step (2), 5-10 ml of n-hexane is added to each 1g of sieved rice residues.

Preferably, in the step (2), 8-10 ml of n-hexane is added to every 1g of sieved rice residues.

More preferably, in the step (2), 10ml of n-hexane is added per 1g of the sieved rice residue.

In one embodiment of the invention, in the step (2), after the screened rice residue obtained in the step (1) is added with n-hexane, stirring is carried out, and degreasing is carried out until no n-hexane remains; stirring for 3-4 h; preferably, the stirring time is 4 h.

In an embodiment of the present invention, in the step (2), the degreasing time is 2 hours.

In one embodiment of the invention, in the step (2), the n-hexane remained in the rice residue is volatilized after degreasing.

In one embodiment of the invention, in the step (3), 10-20 ml of water is added to every 1g of the degreased rice residue.

Preferably, in the step (3), 20ml of water is added to every 1g of the defatted rice residue.

In one embodiment of the present invention, in the step (3), the temperature is adjusted to 90-95 ℃ and the pH is adjusted to 6.0-7.0.

In one embodiment of the present invention, in step (3), the manufacturer of the high temperature alpha-amylase is Novoxil (Beijing) Co., Ltd., and the model of the high temperature alpha-amylase is Termamyl 120L. The high temperature alpha-amylase is an active catalyst, the temperature and the pH value of the invention can improve the activity of the enzyme, and the starch in the rice residue is subjected to enzymolysis, so that the protein extraction yield and the protein purity are improved.

In one embodiment of the invention, in the step (3), the addition amount of the high-temperature alpha-amylase is 0.05-0.1% of the mass of the degreased rice residues; in the step (3), the enzymolysis time is 1-2 h.

In one embodiment of the present invention, in the step (3), the enzymolysis is restriction. Residual starch in the raw material rice residue is removed by limited enzymolysis through high-temperature alpha-amylase, so that protein in the rice residue is enriched, and the yield and the purity of the rice residue protein are improved.

In one embodiment of the present invention, in the step (4), the pH is adjusted to 9.0-10.0.

In one embodiment of the invention, in the step (5), a sodium hydroxide solution is added under the condition of stirring, wherein the concentration of the sodium hydroxide solution is 0.5-1 mol/L; in the step (5), the pH value is adjusted to 11.0-12.0, and the mixture is continuously stirred for 3 hours for alkali extraction. The pH value of the alkali extraction does not dissolve non-protein substances, does not react with amino acid, and does not influence the nutritive value, edibility and protein product quality.

In one embodiment of the invention, in the step (6), a citric acid solution is added under the condition of stirring, wherein the concentration of the citric acid solution is 0.5-1 mol/L. Compared with the traditional method of performing acid precipitation by using hydrochloric acid for preparing rice residue protein through alkali dissolution and acid precipitation, the method adopts citric acid for the acid precipitation step, and the citric acid is complexed with cadmium in the rice residue, so that the cadmium in the rice residue can be removed to a greater extent in the acid precipitation process, the rice residue protein with lower cadmium content is obtained, and the emulsibility of the prepared rice residue protein is greatly improved. In addition, compared with hydrochloric acid, the citric acid has lower pollution and is green and environment-friendly.

In one embodiment of the present invention, in the step (6), the pH is adjusted to 4.5-5.0; in the step (6), the standing time is 0.5-1 h. By adjusting the pH of the dispersion, the protein is separated from the starch and cellulose.

Preferably, in the step (6), the pH is adjusted to 4.8-5.0; in the step (6), the standing time is 0.5-1 h.

More preferably, in step (6), the pH is adjusted to 4.8; in the step (6), the standing time is 0.5-1 h.

In one embodiment of the present invention, in the steps (5) to (6), the rotation speed of the centrifugation is 4000 to 5000rpm, and the time of the centrifugation is 15 to 20 min.

In one embodiment of the invention, in the step (7), the dialysis temperature is 4 ℃, and the dialysis time is 72 hours; in the step (7), the temperature of vacuum freeze drying is-40 ℃ to-50 ℃.

The embodiment of the invention also provides the high-emulsibility cadmium-removed rice residue protein prepared by the preparation method.

The present invention will be described in further detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 citric acid precipitation method of high-emulsibility cadmium-removed rice residue protein

The raw materials of the embodiment are as follows: cadmium exceeding rice residue (sampled by Hengding food Co., Ltd. in Jiangxi province) and the detection result of cadmium content is 0.43 mg/kg.

The embodiment comprises the following steps:

(1) pretreatment of raw materials: removing impurities from 100g of rice residues, crushing and sieving by a 80-mesh sieve;

(2) degreasing: and (2) mixing the sieved rice residue obtained in the step (1) according to a material-liquid ratio of 1: 5 dispersing in n-hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the n-hexane remained in the rice residue to obtain degreased rice residue;

(3) and (3) restriction enzyme hydrolysis: mixing the degreased rice residue obtained in the step (2) according to the proportion of 1: dispersing 10 materials in water to obtain rice residue dispersion, adjusting the temperature of the dispersion to 90 ℃, adjusting the pH to 6.5, adding 0.1g (0.1% of the mass of the rice residue) of high-temperature alpha-amylase to carry out enzymolysis for 1.0h to obtain enzymolysis dispersion;

(4) enzyme deactivation: adjusting the pH value of the enzymolysis dispersion liquid obtained in the step (3) to 9.5, and carrying out enzyme deactivation treatment to obtain enzyme deactivation mixed liquid;

(5) alkali extraction: cooling the enzyme-deactivated mixed liquor obtained in the step (4), adding 1mol/L sodium hydroxide solution into the enzyme-deactivated mixed liquor under stirring of a stirrer to adjust the pH of the mixed liquor to 11.0, continuously stirring for 3 hours, carrying out alkali extraction, centrifuging at 4000rpm for 15min, and keeping a supernatant;

(6) acid precipitation preparation: adding 0.5mol/L citric acid solution into the supernatant obtained in the step (5) under stirring of a stirrer to adjust the pH to 4.5, standing for 0.5h, centrifuging at 4200rpm for 20min, and retaining the precipitate;

(7) and (3) drying: and (4) dialyzing the precipitate obtained in the step (6) at the temperature of 4 ℃ for 72 hours, and carrying out vacuum freeze drying at the temperature of-40 ℃ to obtain the high-emulsibility cadmium-removed rice residue protein.

Example 2 citric acid precipitation method of high-emulsibility cadmium-removed rice residue protein

The raw materials of the embodiment are as follows: cadmium exceeding rice residue (sampled by Hengding food Co., Ltd. in Jiangxi province) and the detection result of cadmium content is 0.38 mg/kg.

The embodiment comprises the following steps:

(1) pretreatment of raw materials: removing impurities from 100g of rice residues, crushing and sieving by a 100-mesh sieve;

(2) degreasing: and (2) mixing the sieved rice residue obtained in the step (1) according to a material-liquid ratio of 1: 10 dispersing in normal hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the normal hexane remained in the rice residue to obtain degreased rice residue;

(3) and (3) restriction enzyme hydrolysis: mixing the degreased rice residue obtained in the step (2) according to the proportion of 1: dispersing 20 materials in water to obtain rice residue dispersion, adjusting the temperature of the dispersion to 95 deg.C, pH7.0, adding 0.1g (0.1% of rice residue) of high temperature alpha-amylase, and performing enzymolysis for 1.5 hr to obtain enzymolysis dispersion;

(4) enzyme deactivation: adjusting the pH value of the enzymolysis dispersion liquid obtained in the step (3) to 9.5, and carrying out enzyme deactivation treatment to obtain enzyme deactivation mixed liquid;

(5) alkali extraction: cooling the enzyme-deactivated mixed liquor obtained in the step (4), adding 1mol/L sodium hydroxide solution into the enzyme-deactivated mixed liquor under stirring of a stirrer to adjust the pH of the mixed liquor to 12.0, continuously stirring for 3h, carrying out alkali extraction, centrifuging at 4000rpm for 15min, and retaining supernatant;

(6) acid precipitation preparation: adding 1.0mol/L citric acid solution into the supernatant obtained in the step (5) under stirring of a stirrer to adjust the pH to 4.8, standing for 1.0h, centrifuging at 4800rpm for 20min, and keeping precipitate;

(7) and (3) drying: and (4) dialyzing the precipitate obtained in the step (6) at the temperature of 4 ℃ for 72 hours, and carrying out vacuum freeze drying at the temperature of-45 ℃ to obtain the high-emulsibility cadmium-removed rice residue protein.

Example 3 citric acid precipitation method of high-emulsibility cadmium-removed rice residue protein

The raw materials of the embodiment are as follows: cadmium exceeding rice residue (sampled by Hengding food Co., Ltd. in Jiangxi province) and the detection result of cadmium content is 0.40 mg/kg.

The embodiment comprises the following steps:

(1) pretreatment of raw materials: removing impurities from 100g of rice residues, crushing and sieving by a 120-mesh sieve;

(2) degreasing: and (2) mixing the sieved rice residue obtained in the step (1) according to a material-liquid ratio of 1: 8, dispersing in n-hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the n-hexane remained in the rice residue to obtain degreased rice residue;

(3) and (3) restriction enzyme hydrolysis: mixing the degreased rice residue obtained in the step (2) according to the proportion of 1: dispersing 15 material liquid ratios in water to obtain rice residue dispersion, adjusting the temperature of the dispersion to 90 ℃, adjusting the pH to 7.0, adding 0.1g (0.1% of the mass of the rice residue) of high-temperature alpha-amylase to carry out enzymolysis treatment for 1.5h to obtain enzymolysis dispersion;

(4) enzyme deactivation: adjusting the pH value of the enzymolysis dispersion liquid obtained in the step (3) to 9.0, and carrying out enzyme deactivation treatment to obtain enzyme deactivation mixed liquid;

(5) alkali extraction: cooling the enzyme-deactivated mixed liquor obtained in the step (4), adding 1mol/L sodium hydroxide solution into the enzyme-deactivated mixed liquor under stirring of a stirrer to adjust the pH of the mixed liquor to 11.5, continuously stirring for 3 hours, carrying out alkali extraction, centrifuging at 4000rpm for 15min, and keeping a supernatant;

(6) acid precipitation preparation: under the condition of stirring by a stirrer, adding 0.8mol/L citric acid solution into the supernatant obtained in the step (5) to adjust the pH value to 5.0, standing for 0.5h, centrifuging at 4500rpm for 15min, and retaining the precipitate;

(7) and (3) drying: and (4) dialyzing the precipitate obtained in the step (6) at the temperature of 4 ℃ for 72 hours, and carrying out vacuum freeze drying at the temperature of-48 ℃ to obtain the high-emulsibility cadmium-removed rice residue protein.

Example 4 citric acid precipitation method of high-emulsibility cadmium-removed rice residue protein

The raw materials of the embodiment are as follows: cadmium exceeding rice residue (sampled by Hengding food Co., Ltd. in Jiangxi province) and the detection result of cadmium content is 0.46 mg/kg.

The embodiment comprises the following steps:

(1) pretreatment of raw materials: removing impurities from 100g of rice residues, crushing and sieving by a 120-mesh sieve;

(2) degreasing: and (2) mixing the sieved rice residue obtained in the step (1) according to a material-liquid ratio of 1: 10 dispersing in normal hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the normal hexane remained in the rice residue to obtain degreased rice residue;

(3) and (3) restriction enzyme hydrolysis: mixing the degreased rice residue obtained in the step (2) according to the proportion of 1: dispersing 20 materials in water to obtain rice residue dispersion, adjusting the temperature of the dispersion to 95 deg.C and pH to 7.0, adding 0.1g (0.1% of rice residue) of high temperature alpha-amylase, and performing enzymolysis for 2 hr to obtain enzymolysis dispersion;

(4) enzyme deactivation: adjusting the pH value of the enzymolysis dispersion liquid obtained in the step (3) to 10.0, and carrying out enzyme deactivation treatment to obtain enzyme deactivation mixed liquid;

(5) alkali extraction: cooling the enzyme-deactivated mixed liquor obtained in the step (4), adding 1.0mol/L sodium hydroxide solution into the enzyme-deactivated mixed liquor under stirring of a stirrer to adjust the pH of the mixed liquor to 12.0, continuously stirring for 3 hours, carrying out alkali extraction, centrifuging at 4000rpm for 15min, and retaining supernatant;

(6) acid precipitation preparation: under the condition of stirring by a stirrer, adding 0.5mol/L citric acid solution into the supernatant obtained in the step (5) to adjust the pH value to 4.8, standing for 1.0h, centrifuging at 4000rpm for 15min, and keeping the precipitate;

(7) and (3) drying: and (4) dialyzing the precipitate obtained in the step (6) at the temperature of 4 ℃ for 72 hours, and carrying out vacuum freeze drying at the temperature of-50 ℃ to obtain the high-emulsibility cadmium-removed rice residue protein.

Comparative example 1 hydrochloric acid precipitation method of rice residue protein

The difference from the example 3 is that the detection result of the cadmium content of the cadmium exceeding rice residue raw material is 0.42 mg/kg; in the step (6), in the preparation of acid precipitation, 1.0mol/L hydrochloric acid solution is added into the supernatant obtained in the step (5).

Comparative example 2 tartaric acid precipitation method of rice residue protein

The difference from the example 4 is that the detection result of the cadmium content of the cadmium exceeding rice residue raw material is 0.44 mg/kg; in the step (6), in the acid precipitation preparation, 0.8mol/L tartaric acid solution is added into the supernatant obtained in the step (5).

Comparative example 3 malic acid precipitation method of rice residue protein

The difference from the example 2 is that the detection result of the cadmium content of the cadmium exceeding rice residue raw material is 0.41 mg/kg; in the step (6), during the preparation of acid precipitation, 1.0mol/L malic acid solution is added into the supernatant obtained in the step (5).

Test example 1 influence of acid precipitation with different acids on cadmium content and emulsification Properties of Rice residue protein

In order to compare the influence of acid precipitation on the cadmium content and the emulsification property of the rice residue protein by different acids, the dried rice residue protein powder products of examples 1-4 and comparative examples 1-3 were respectively detected by an atomic absorption method, and the statistics of the results are shown in table 1.

TABLE 1 Effect of different acids on cadmium content and emulsification Properties of Rice dreg proteins

As can be seen from Table 1, the cadmium content of the rice residue protein obtained by acid precipitation with citric acid in examples 1-4 was less than 0.1mg/kg, which is far below the limit of cadmium in the food specified in the national standard. In addition, the embodiment 1-4 can remove more than 90% of cadmium, and can effectively solve the problem that the rice residue protein is not suitable for eating due to the excessive cadmium content. Examples 1-4 the emulsifying activity of the rice mill residue protein obtained by acid precipitation with citric acid was higher than 9.0m²Are higher than those of comparative examples 1 to 3. Examples 1-4 the emulsion stability of the rice mill residue protein obtained by acid precipitation with citric acid was higher than 85% and higher than that of comparative examples 1-3. Examples 1-4 the protein content of the rice residue obtained by acid precipitation with citric acid was higher than that of comparative examples 1-3. The results show that the yield and purity of the rice residue protein prepared by using citric acid for acid precipitation are higher than those of the rice residue protein prepared by using hydrochloric acid and tartaric acid for acid precipitation, and the emulsifying property is good.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.