阅读说明：本技术 脱镉大米蛋白及其制备方法 (Cadmium-removed rice protein and preparation method thereof ) 是由 赵强 游洋 熊华 谢明勇 刘欢 饶世平 刘胜国 于 2021-08-04 设计创作，主要内容包括：本发明提出脱镉大米蛋白及其制备方法,涉及大米精深加工技术领域。所述制备方法,包括如下步骤：(1)将大米去除杂质后粉碎过筛,得大米粉；(2)将上述大米粉用正己烷进行脱脂,得脱脂大米粉；(3)将上述脱脂大米粉分散于水中,碱提,离心,得上清液；(4)调节上述上清液pH至4.5～5.0后,静置,离心,得沉淀；(5)将上述沉淀透析,一次干燥,得大米蛋白；(6)将上述大米蛋白分散于酸溶液中,调节温度至80～90℃,脱酰胺处理；(7)将脱酰胺处理后的大米蛋白透析,二次干燥,得脱镉大米蛋白。该方法操作简单,绿色环保,成本较低,应用价值高,适宜大规模的推广和应用。(The invention provides cadmium-free rice protein and a preparation method thereof, and relates to the technical field of rice deep processing. The preparation method comprises the following steps: (1) removing impurities from rice, pulverizing, and sieving to obtain rice flour; (2) defatting the rice flour with n-hexane to obtain defatted rice flour; (3) dispersing the defatted rice flour in water, alkali extracting, and centrifuging to obtain supernatant; (4) adjusting the pH value of the supernatant to 4.5-5.0, standing, and centrifuging to obtain a precipitate; (5) dialyzing the precipitate, and drying for the first time to obtain rice protein; (6) dispersing the rice protein in an acid solution, adjusting the temperature to 80-90 ℃, and performing deamidation treatment; (7) dialyzing the rice protein after deamidation treatment, and drying for the second time to obtain the cadmium-removed rice protein. The method is simple to operate, environment-friendly, low in cost, high in application value and suitable for large-scale popularization and application.)

1. The preparation method of the cadmium-removed rice protein is characterized by comprising the following steps:

(1) removing impurities from rice, pulverizing, and sieving to obtain rice flour;

(2) defatting the rice flour with n-hexane to obtain defatted rice flour;

(3) dispersing the defatted rice flour in water, alkali extracting, and centrifuging to obtain supernatant;

(4) adjusting the pH value of the supernatant to 4.5-5.0, standing, and centrifuging to obtain a precipitate;

(5) dialyzing the precipitate, and drying for the first time to obtain rice protein;

(6) dispersing the rice protein in an acid solution, adjusting the temperature to 80-90 ℃, and performing deamidation treatment;

(7) dialyzing the rice protein after deamidation treatment, and drying for the second time to obtain the cadmium-removed rice protein.

2. The method of claim 1, wherein:

in the step (1), the crushing and sieving is to pass through a 60-120-mesh sieve.

3. The method of claim 1, wherein:

in the step (2), the mass-to-volume ratio of the rice flour to the n-hexane is 1g: 5-10 mL.

4. The method of claim 1, wherein:

in the step (3), the mass-to-volume ratio of the defatted rice flour to water is 1g: 10-20 mL.

5. The method of claim 1, wherein:

in the step (3), the pH value of alkali extraction is 11.0-12.0;

in the step (3), the alkali extraction time is 3 h.

6. The method of claim 1, wherein:

in the step (4), adding a hydrochloric acid solution to adjust the pH, wherein the concentration of the hydrochloric acid solution is 0.5-1 mol/L;

in the step (4), the standing time is 0.5-1 h.

7. The method of claim 1, wherein:

in the step (6), the obtained rice protein is dispersed in the citric acid solution, and the mass-volume ratio of the rice protein to the citric acid solution is 1g: 10-15 mL.

8. The method of claim 1, wherein:

in the step (6), the acid solution comprises at least one of a citric acid solution, a hydrochloric acid solution and a malic acid solution; the concentration of the acid solution is 0.06-0.10 mol/L.

9. The method of claim 1, wherein:

in the step (6), the time of the deamidation treatment is 120-180 min.

10. The cadmium-removed rice protein prepared by the preparation method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of rice deep processing, in particular to cadmium-free rice protein and a preparation method thereof.

Background

The quality of rice protein (rice protein) is generally recognized as the best among cereal proteins, and the rice protein has high nutritional value and can be comparable with eggs, cow milk and beef. 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), and the biological value can reach 77.

Cadmium has become a common contaminant in human food due to the high conversion factor from soil to plants. According to research, cadmium in rice mainly exists in an inorganic form. The rice protein as a deep processing product of rice can not reduce the cadmium content in the traditional processing process. On the contrary, in the traditional rice protein extraction process, along with the separation of starch in rice, most of cadmium is combined and enriched in the rice protein by inorganic cadmium and the rice protein, and further heavy metal pollution in the rice protein product is caused, and the content of the cadmium is even far higher than that of the cadmium in the original rice. Therefore, how to remove cadmium in rice protein becomes a problem which needs to be solved urgently in the industry of rice and deep-processed products thereof at present.

Disclosure of Invention

The invention provides cadmium-removed rice protein, which solves the problem of overhigh cadmium content of the existing rice protein, and the cadmium content of the obtained rice protein is lower than 0.1mg/kg and far lower than the limit of cadmium in food specified in national standards, so that the rice protein is safe and reliable.

The invention provides a preparation method of cadmium-removed rice protein, which comprises the following steps:

(1) removing impurities from rice, pulverizing, and sieving to obtain rice flour;

(2) defatting the rice flour with n-hexane to obtain defatted rice flour;

(3) dispersing the defatted rice flour in water, alkali extracting, and centrifuging to obtain supernatant;

(4) adjusting the pH value of the supernatant to 4.5-5.0, standing, and centrifuging to obtain a precipitate;

(5) dialyzing the precipitate, and drying for the first time to obtain rice protein;

(6) dispersing the rice protein in an acid solution, adjusting the temperature to 80-90 ℃, and performing deamidation treatment;

(7) dialyzing the rice protein after deamidation treatment, and drying for the second time to obtain the cadmium-removed rice protein.

Further, in the step (1), the crushing and sieving is to pass through a 60-120-mesh sieve.

Further, in the step (2), the mass-to-volume ratio of the rice flour to the n-hexane is 1g: 5-10 mL.

Further, in the step (3), the mass-to-volume ratio of the defatted rice flour to water is 1g: 10-20 mL.

Further, in the step (3), the pH value of the alkali extraction is 11.0-12.0; in the step (3), the alkali extraction time is 3 h.

Further, in the step (4), adding a hydrochloric acid solution to adjust the pH value, wherein the concentration of the hydrochloric acid solution is 0.5-1 mol/L;

in the step (4), the standing time is 0.5-1 h.

Further, in the step (6), the obtained rice protein is dispersed in the citric acid solution at a mass-to-volume ratio of 1g: 10-15 mL.

Further, in the step (6), the acid solution comprises at least one of a citric acid solution, a hydrochloric acid solution and a malic acid solution; the concentration of the acid solution is 0.06-0.10 mol/L.

Further, in the step (6), the time of the deamidation treatment is 120-180 min.

Further, in the steps (5) and (7), the primary drying and the secondary drying are vacuum freeze drying;

the temperature of the vacuum freeze drying is-40 to-50 ℃.

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

The invention has the following advantages:

according to the preparation method of the cadmium-removed rice protein, disclosed by the invention, the rice is subjected to citric acid deamidation treatment, so that cadmium in the rice protein can be complexed with acid radical ions to form soluble substances, more than ninety percent of cadmium can be removed, and the problem that the rice protein is not suitable for eating due to the excessive cadmium content can be effectively solved. Meanwhile, under the condition that the temperature of the acid-soaking protein is higher, the rice protein can be subjected to deamidation treatment, so that the solubility of the rice protein, the emulsifying activity of the rice protein, the emulsifying stability of the rice protein, the foaming activity of the rice protein, the foaming stability of the rice protein and other functional characteristics are improved. The method is simple to operate, environment-friendly, low in cost, high in application value and suitable for large-scale popularization and application.

Detailed Description

For the convenience of understanding, the present invention will be further described with reference to the following examples, which are not intended to limit the present invention.

Rice protein is a plant protein with low allergy and high nutritional value, more than 80% of the rice protein is insoluble gluten, and the functional characteristics of the rice protein are affected due to poor solubility, including emulsifying property, emulsifying stability, foaming property, foaming stability, water and oil retention and other processing performances, so that the wide application of the rice protein in food is limited, the rice protein is difficult to further apply in food, and the rice protein can be widely applied in the field of food industry, so that the functions of the rice protein such as solubility and the like need to be modified.

An embodiment of the invention provides a preparation method of cadmium-removed rice protein, which comprises the following steps:

(1) removing impurities from rice, pulverizing, and sieving to obtain rice flour;

(2) defatting the rice flour with n-hexane to obtain defatted rice flour;

(3) dispersing the defatted rice flour in water, alkali extracting, and centrifuging to obtain supernatant;

(4) adjusting the pH value of the supernatant to 4.5-5.0, standing, and centrifuging to obtain a precipitate;

(5) dialyzing the precipitate, and drying for the first time to obtain rice protein;

(6) dispersing the rice protein in a citric acid solution, adjusting the temperature to 80-90 ℃, and performing deamidation treatment;

(7) dialyzing the rice protein after deamidation treatment, and drying for the second time to obtain the cadmium-removed rice protein.

According to the embodiment of the invention, the rice is subjected to citric acid deamidation treatment, so that cadmium in rice protein can be complexed with acid radical ions to form soluble substances, and the cadmium removal effect is achieved. Meanwhile, under the condition that the temperature of the acid-soaking protein is higher, the rice protein can be subjected to deamidation treatment, so that the solubility of the rice protein, the emulsifying activity of the rice protein, the emulsifying stability of the rice protein, the foaming activity of the rice protein, the foaming stability of the rice protein and other functional characteristics are improved, and the limitation of the application of the rice protein in the food industry is solved.

In one embodiment of the invention, in the step (1), the crushing and sieving is to pass through a 60-120-mesh sieve.

In an embodiment of the present invention, in the step (2), a mass-to-volume ratio (g/mL) of the rice flour to the n-hexane is 1: 5 to 10. That is, the mass-to-volume ratio of the rice flour to the n-hexane is 1g: 5-10 mL.

In one embodiment of the invention, residual n-hexane in the rice flour is volatilized after degreasing, so that subsequent treatment is facilitated.

In one embodiment of the invention, in the step (3), the mass-to-volume ratio (g/mL) of the defatted rice flour to water is 1: 10-20. Namely, the mass-volume ratio of the defatted rice flour to water is 1g: 10-20 mL.

In one embodiment of the invention, in the step (3), the pH value of the alkali extraction is 11.0-12.0; adding NaOH solution to adjust the pH value; the concentration of the NaOH solution is 0.5-1 mol/L; in the step (3), the alkali extraction time is 3 h.

In the embodiment of the invention, more than 80% of the rice protein can be dissolved in the alkaline solution, the solubility of the rice protein is higher under the strong alkaline condition, but the high alkaline can dissolve non-protein substances, and the quality of protein products is influenced. In addition, in the alkaline environment, some amino acids of the protein, such as lysine and alanine or skin ammonia acid, are subjected to condensation reaction to generate toxic substances, the nutritive value of the lysine is greatly reduced, and the finished product is dark in color, bitter in taste and poor in edibility. Therefore, it is important to select a suitable pH value in the alkali extraction.

In one embodiment of the invention, in the step (4), a hydrochloric acid solution is added to adjust the pH, wherein the concentration of the hydrochloric acid solution is 0.5-1 mol/L. In the step (4), the standing time is 0.5-1 h.

In the embodiment of the invention, the rice protein has the characteristic of low solubility under the condition of isoelectric point, and the protein can be separated from starch and cellulose by adjusting the pH of a dispersion system.

In one embodiment of the invention, in the step (6), the mass-to-volume ratio (g/mL) of the obtained rice protein dispersed in the citric acid solution is 1: 10-15. Namely, the obtained rice protein is dispersed in the citric acid solution, and the mass-volume ratio of the rice protein to the citric acid solution is 1g: 10-15 mL.

In an embodiment of the present invention, in the step (6), the acid solution includes at least one of a citric acid solution, a hydrochloric acid solution, and a malic acid solution; the concentration of the acid solution is 0.06-0.10 mol/L. Preferably, in the step (6), the acid solution is citric acid solution. The concentration of the citric acid solution is 0.06-0.10 mol/L.

In an embodiment of the present invention, in the step (6), the time of the deamidation treatment is 120-180 min.

In one embodiment of the present invention, in steps (5) and (7), the primary drying and the secondary drying are vacuum freeze drying. The temperature of the vacuum freeze drying is-40 to-50 ℃.

The present invention will be described in detail with reference to examples.

In the following examples, the unit of the mass-to-volume ratio is g/mL.

Example 1A preparation method of cadmium-removed rice protein comprises the following steps:

raw materials: the cadmium content of the rice exceeding the standard (sampled by Hengding food Co., Ltd. in Jiangxi province) is 0.38 mg/kg.

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

(2) degreasing: sieving the rice flour obtained in the step (1) according to a mass-volume ratio of 1: 5 dispersing in n-hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the n-hexane remained in the rice flour to obtain degreased rice flour;

(3) alkali extraction: dispersing the degreased rice flour obtained in the step (2) in water according to the mass-to-volume ratio of 1:10 to obtain a rice flour dispersion liquid, stirring, adding 0.5mol/LNaOH solution into the rice flour dispersion liquid to adjust the pH value to 11.0, carrying out alkali extraction for 3 hours under continuous stirring, centrifuging at 4000rpm for 15min, and keeping a supernatant;

(4) acid precipitation preparation: adding 0.5mol/L hydrochloric acid solution into the supernatant obtained in the step (3) to adjust the pH to 4.5, standing for 0.5h, centrifuging at 4000rpm for 15min, and retaining the precipitate;

(5) primary drying: dialyzing the precipitate obtained in the step (4), and carrying out vacuum freeze drying at-40 ℃ to obtain the rice protein.

(6) Deamidation treatment: dispersing the rice protein obtained in the step (5) in a citric acid solution with the concentration of 0.08mol/L according to the mass-volume ratio of 1:12.5, adjusting the temperature to 85 ℃, and performing deamidation treatment for 150 min.

(7) Secondary drying: dialyzing the rice protein after deamidation of the citric acid obtained in the step (6), and carrying out vacuum freeze drying at-40 ℃ to obtain the high-functional cadmium-removed rice protein.

The cadmium content of the rice protein powder dried in the embodiment is 0.03mg/kg through atomic absorption spectrometry.

Example 2A preparation method of cadmium-removed rice protein comprises the following steps:

raw materials: the cadmium content of the rice exceeding the standard (sampled by Hengding food Co., Ltd. in Jiangxi province) is 0.35 mg/kg.

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

(2) degreasing: sieving the rice flour obtained in the step (1) according to a mass-volume ratio of 1: dispersing 10 in n-hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the n-hexane remained in the rice flour to obtain degreased rice flour;

(3) alkali extraction: dispersing the degreased rice flour obtained in the step (2) in water according to the mass-to-volume ratio of 1:15 to obtain a rice flour dispersion liquid, stirring, adding 1.0mol/LNaOH solution into the rice flour dispersion liquid to adjust the pH value to 11.5, carrying out alkali extraction for 3 hours under continuous stirring, centrifuging at 4000rpm for 15min, and keeping a supernatant;

(4) acid precipitation preparation: adding 0.8mol/L hydrochloric acid solution into the supernatant obtained in the step (3) to adjust the pH value to 5.0, standing for 0.5h, centrifuging at 4000rpm for 15min, and retaining the precipitate;

(5) primary drying: dialyzing the precipitate obtained in the step (4), and carrying out vacuum freeze drying at-45 ℃ to obtain the rice protein.

(6) Deamidation treatment: dispersing the rice protein obtained in the step (5) in a citric acid solution with the concentration of 0.06mol/L according to the mass-volume ratio of 1:15, adjusting the temperature to 90 ℃, and performing deamidation treatment for 150 min.

(7) Secondary drying: dialyzing the rice protein after deamidation of the citric acid obtained in the step (6), and carrying out vacuum freeze drying at-45 ℃ to obtain the high-functional cadmium-removed rice protein.

The cadmium content of the rice protein powder dried in the embodiment is 0.03mg/kg through atomic absorption spectrometry.

Example 3A preparation method of cadmium-removed rice protein comprises the following steps:

raw materials: the cadmium content of the rice exceeding the standard (sampled by Hengding food Co., Ltd. in Jiangxi province) is 0.40 mg/kg.

(1) Rice pretreatment: removing impurities from 100g of rice, crushing and sieving with a 120-mesh sieve;

(2) degreasing: sieving the rice flour obtained in the step (1) according to a mass-volume ratio of 1: dispersing 10 in n-hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the n-hexane remained in the rice flour to obtain degreased rice flour;

(3) alkali extraction: dispersing the degreased rice flour obtained in the step (2) in water according to the mass-to-volume ratio of 1:15 to obtain a rice flour dispersion liquid, stirring, adding 1.0mol/LNaOH solution into the rice flour dispersion liquid to adjust the pH value to 12.0, carrying out alkali extraction for 3 hours under continuous stirring, centrifuging at 4000rpm for 15min, and keeping a supernatant;

(4) acid precipitation preparation: adding 0.5mol/L hydrochloric acid solution into the supernatant obtained in the step (3) to adjust the pH to 4.8, standing for 0.5h, centrifuging at 4000rpm for 15min, and retaining the precipitate;

(5) primary drying: dialyzing the precipitate obtained in the step (4), and carrying out vacuum freeze drying at-45 ℃ to obtain the rice protein.

(6) Deamidation treatment: dispersing the rice protein obtained in the step (5) in a citric acid solution with the concentration of 0.08mol/L according to the mass-volume ratio of 1:10, adjusting the temperature to 85 ℃, and performing deamidation treatment for 150 min.

(7) Secondary drying: dialyzing the rice protein after deamidation of the citric acid obtained in the step (6), and carrying out vacuum freeze drying at-45 ℃ to obtain the high-functional cadmium-removed rice protein.

The cadmium content of the rice protein powder dried in the embodiment is 0.03mg/kg through atomic absorption spectrometry.

Example 4A preparation method of cadmium-removed rice protein comprises the following steps:

raw materials: the cadmium content of the rice exceeding the standard (sampled by Hengding food Co., Ltd. in Jiangxi province) is 0.38 mg/kg.

(1) Rice pretreatment: removing impurities from 100g of rice, crushing and sieving with a 120-mesh sieve;

(2) degreasing: sieving the rice flour obtained in the step (1) according to a mass-volume ratio of 1: dispersing 10 in n-hexane, stirring for 4h by a stirrer, degreasing, and volatilizing the n-hexane remained in the rice flour to obtain degreased rice flour;

(3) alkali extraction: dispersing the degreased rice flour obtained in the step (2) in water according to the mass-to-volume ratio of 1:20 to obtain a rice flour dispersion liquid, stirring, adding 0.5mol/LNaOH solution into the rice flour dispersion liquid to adjust the pH value to 12.0, continuously stirring for alkali extraction for 3 hours, centrifuging at 4000rpm for 15min, and keeping a supernatant;

(4) acid precipitation preparation: adding 0.5mol/L hydrochloric acid solution into the supernatant obtained in the step (3) to adjust the pH to 4.8, standing for 1.0h, centrifuging at 4000rpm for 15min, and retaining the precipitate;

(5) primary drying: dialyzing the precipitate obtained in the step (4), and carrying out vacuum freeze drying at-50 ℃ to obtain the rice protein.

(6) Deamidation treatment: dispersing the rice protein obtained in the step (5) in a citric acid solution with the concentration of 0.08mol/L according to the mass-volume ratio of 1:12.5, adjusting the temperature to 90 ℃, and performing deamidation treatment for 180 min.

(7) Secondary drying: dialyzing the rice protein after deamidation of the citric acid obtained in the step (6), and carrying out vacuum freeze drying at-50 ℃ to obtain the high-functional cadmium-removed rice protein.

The cadmium content of the rice protein powder dried in the embodiment is 0.02mg/kg through atomic absorption spectrometry.

Example 5Hydrochloric acid deamidation method for rice protein

The difference from the example 1 is that the detection result of the cadmium content of the cadmium exceeding rice residue raw material is 0.36 mg/kg; in the step (6), the rice protein obtained in the step (5) is dispersed in a hydrochloric acid solution with the concentration of 0.08mol/L according to the mass-to-volume ratio of 1: 12.5.

The cadmium content of the rice protein powder dried in the comparative example is 0.12mg/kg through atomic absorption detection.

Example 6Malic acid deamidation method of rice protein

The difference from the example 1 is that the detection result of the cadmium content of the cadmium exceeding rice residue raw material is 0.37 mg/kg; in the step (6), the rice protein obtained in the step (5) is dispersed in malic acid solution with the concentration of 0.08mol/L according to the mass-to-volume ratio of 1: 12.5.

The cadmium content of the rice protein powder dried in the comparative example is 0.08mg/kg through atomic absorption detection.

Test example 1Rice protein performance testing

Cadmium content is measured by adopting an atomic absorption method, solubility is measured by adopting a Fulin phenol colorimetric method, emulsifying property is measured by adopting a turbidity method, and foaming property is measured by adopting methods such as Miedzianka and the like. The results of comparing the rice protein without deamidation treatment with the rice protein with deamidation treatment in the above examples are shown in Table 1.

TABLE 1

The above-described embodiments are preferred implementations of the present invention, and the present invention may be implemented in other ways without departing from the spirit of the present invention.