Quinoa concentrated protein powder rich in arginine and preparation method thereof

Abstract

The invention discloses chenopodium quinoa concentrated protein powder rich in arginine and a preparation method of the chenopodium quinoa concentrated protein powder. The content of protein (dry basis) in the chenopodium quinoa concentrated protein powder is larger than or equal to 75%, and the content of the arginine is larger than or equal to 7.0 g per 100 g protein. Chenopodium quinoa willd is subjected to milling processing and flotation separation to obtain chenopodium quinoa willd germs, then water is added for homogenization to obtain chenopodium quinoa willd germ homogenate, cell wall degrading enzyme is added for ultrasonic-assisted enzymolysis and sieving to obtain enzymolysis slurry, and the enzymolysis slurry is subjected to alcohol extraction impurity removal and drying to obtain chenopodium quinoa willd concentrated protein powder; the separation efficiency is improved while the separation process is simplified, the protein is prevented from being degraded and damaged, the protein yield is higher than 95%, and the maximum utilization of quinoa germ protein resources is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of plant protein processing, and particularly relates to arginine-rich quinoa concentrated protein powder and a preparation method thereof. Background Art

[0002] Plant protein is an important source of dietary protein for residents. It not only has unique advantages such as abundant resources and low cost, but can also be used as a substitute protein to alleviate the health and environmental pollution problems caused by over-exploitation of animal protein, showing great development potential. Plant-based protein beverages can be used as milk substitutes to provide a variety of nutritional choices for people with lactose intolerance, milk protein allergies and vegetarian consumers, and have shown significant growth momentum in recent years.

[0003] Quinoa has been identified by the Food and Agriculture Organization of the United Nations as an important alternative crop to promote global food security. It has a protein content of about 12% to 23% and is rich in essential amino acids needed by the human body. It is a high-quality source of plant protein. Quinoa grains are mainly composed of the endosperm in the center and the germ surrounding it. The protein content of quinoa germ is about 40%, which is a food resource with great development potential.

[0004] Arginine is one of the basic amino acids that make up proteins. When the body's own synthesis is insufficient to meet demand under certain physiological conditions (such as disease or growth and development), it must be supplemented through diet. It is a conditionally essential amino acid. Arginine is not only a precursor for protein synthesis, but also a precursor for the synthesis of biological molecules such as nitric oxide, polyamines, proline, and glutamate. It participates in a variety of physiological and biochemical reactions in the body and plays an important role in regulating immune function, improving cardiovascular disease, promoting reproductive system function, and promoting wound healing.

[0005] Chinese patent CN 108244329 B discloses a method for preparing quinoa germ protein powder, which uses quinoa germ as raw material to separate and extract protein powder, specifically separating starch by sieving quinoa after crushing, and extracting water-soluble protein and water-insoluble protein in steps. The operation process is cumbersome, which is not conducive to its wide application in the food industry. The production of traditional plant protein mainly undergoes processes such as defatting, extraction, separation, and drying. In order to increase the protein content or protein extraction rate of the product, multiple solvent extraction and centrifugal concentration operation processes are usually required. The process is cumbersome, the production cost is high, and there is a large room for improvement in energy conservation and emission reduction. Summary of the invention

[0006] The purpose of the present invention is to provide a quinoa concentrated protein powder rich in arginine and a preparation method thereof, so as to solve the problems of complicated operation process and harsh reaction conditions in the prior art of extracting quinoa protein powder, and at the same time improve the separation efficiency, avoid protein degradation and destruction, and achieve a protein yield higher than 95%, thereby realizing the maximum utilization of quinoa germ protein resources.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows:

[0008] The invention discloses quinoa concentrated protein powder rich in arginine. The protein content (dry basis) of the obtained quinoa concentrated protein powder is ≥75%, and the arginine content is ≥7.0g / 100g protein.

[0009] The method for preparing the quinoa concentrated protein powder of the present invention comprises the following steps:

[0010] 1) Grinding the quinoa to peel off the seed coat, then placing it in low-temperature water with a volume of 2 to 4 times the mass of the quinoa and stirring it for 5 to 20 minutes, and flotation separation to obtain quinoa germ, wherein the water temperature is 5 to 15° C.;

[0011] 2) adding water to the obtained quinoa germ to obtain a quinoa germ homogenate, adding a cell wall degrading enzyme, ultrasonicating at 30 to 50° C. for 0.5 to 4 h, then inactivating the enzyme at 85 to 95° C., and passing through a 100 to 200 mesh sieve to obtain an enzymatic slurry; the amount of the cell wall degrading enzyme added is 1.0 to 3.0% of the mass of the quinoa germ;

[0012] 3) adding ethanol to the enzymatic slurry to a final ethanol concentration of 30-60%, removing the upper liquid after low-temperature centrifugation at 10-15° C., and drying the solid to obtain quinoa concentrated protein powder.

[0013] Preferably, in step 1), the reduction rate of quinoa during grinding is 13-20%.

[0014] Preferably, in step 2), the pH of the quinoa germ homogenate is adjusted to 4.0-6.0 before adding the cell wall degrading enzyme.

[0015] Preferably, in step 2), the cell wall degrading enzyme is one or more of cellulase, hemicellulase, xylanase and pectinase.

[0016] After the quinoa seeds are ground to remove the seed coat, the annular germ on the periphery of the seeds is directly exposed, and the germ is very easy to fall off naturally after swelling after absorbing water. Therefore, the present invention adopts grinding and flotation separation of quinoa germ, and the protein content in the quinoa germ is measured to be 42.52±0.71%, and the fat content is 16.40±0.23%.

[0017] Proteins and liposomes in plant cells are surrounded by cell walls containing cellulose, hemicellulose, pectin and other substances, which become barriers that prevent proteins and oils from being released from cells. The present invention uses cell wall degrading enzymes to effectively destroy the cell wall structure of quinoa germ on the basis of mechanical crushing, further destroys the cell wall and complex structures such as lipopolysaccharides and lipoproteins by means of ultrasonic cavitation, and enhances the activity of the enzyme within a certain intensity range, accelerates the degradation of the cell wall structure and the release of proteins and oils, and finally adds a certain concentration of ethanol to greatly increase the dissolution of small molecular impurities such as polyphenols.

[0018] Preferably, the pH of the quinoa germ homogenate is adjusted to 4.0-6.0 before adding the cell wall degrading enzyme, because studies have shown that the pH has a great influence on the protein yield and arginine content in the final product, and only by controlling the pH of the quinoa germ homogenate within this range can the protein and arginine be retained in the protein powder to the greatest extent.

[0019] In the present invention, the enzymatic hydrolysis slurry is centrifuged under low temperature conditions and then separated into layers. The main components of the upper layer liquid are oil, soluble sugar and small molecular substances, and the main component of the lower layer precipitation is protein.

[0020] The present invention has the following beneficial effects:

[0021] The present invention simultaneously removes most of the non-protein components such as carbohydrates, oils, small molecule impurities, etc. in quinoa germ through one solvent extraction and centrifugation, simplifies the separation process and improves the separation efficiency, realizes the efficient concentration and enrichment of quinoa protein, reduces the cost and improves the efficiency for industrial production.

[0022] The present invention firstly realizes the enrichment of high-protein components in quinoa grains by grinding and flotation, thereby reducing water consumption and workload for subsequent wet protein separation; ultrasonic-assisted bioenzymatic hydrolysis is used to effectively increase the degradation of cell walls and the release of small molecule compounds such as proteins, oils, polyphenols, etc., and alcohol solution is used as a medium to separate soluble non-protein components, which is green, safe, and has mild conditions; the product obtained by the present invention has bright color, the protein is not degraded and destroyed, the protein yield is higher than 95%, and the maximum utilization of quinoa germ protein resources is achieved.

[0023] The arginine content of the quinoa concentrated protein powder obtained by the present invention is greater than 7.0g / 100g protein, which is higher than the arginine content in plant protein powders such as wheat protein, corn protein, and soybean protein, and can be used as a dietary supplement for specific groups of people. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a schematic diagram of the preparation process of quinoa concentrated protein powder. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the embodiments and drawings.

[0026] See also Figure 1 , Example 1

[0027] Take quinoa raw materials with uniform size, full grains and no impurities, add water to moisten the wheat to adjust its moisture content to 16.3%, use a sand roller rice mill to grind the quinoa with a grinding rate of 14.9%, then mix the quinoa with ice water at a mass ratio of 1:4, and separate the quinoa germ by flotation; put the separated quinoa germ in a wall breaking machine, add water to pulp at a material-liquid ratio of 1:4, adjust the slurry pH to 4.5, add 0.8% of the quinoa germ mass of cell wall degrading enzyme, perform ultrasonic assisted enzymolysis at 40°C for 1h, inactivate the enzyme in a constant temperature water bath at 90°C for 10min, cool to room temperature and pass through a 100-mesh sieve; add ethanol to the enzymatic hydrolysis slurry with a final ethanol concentration of 30%, stir and mix, centrifuge at low temperature, remove the upper liquid, and obtain quinoa concentrated protein powder after solid phase freeze-drying.

[0028] Example 2

[0029] Take quinoa raw materials with uniform size, full grains and no impurities, add water to moisten the wheat to adjust its moisture content to 16.6%, use a sand roller rice mill to grind the quinoa with a grinding rate of 17.1%, then mix the quinoa with ice water at a mass ratio of 1:3, and separate the quinoa germ by flotation; put the separated quinoa germ in a wall breaking machine, add water to pulp at a material-liquid ratio of 1:4, adjust the slurry pH to 4.0, add cell wall degrading enzyme of 1.5% of the mass of quinoa germ, and after ultrasonic-assisted enzymolysis at 40°C for 0.5h, inactivate the enzyme in a constant temperature water bath at 90°C for 10min, cool to room temperature and pass through a 140-mesh sieve; add ethanol to the enzymatic hydrolysis slurry with a final ethanol concentration of 40%, stir and mix, centrifuge at low temperature, remove the upper liquid, and obtain quinoa concentrated protein powder after solid phase freeze-drying.

[0030] Example 3

[0031] Take quinoa raw materials with uniform size, full grains and no impurities, add water to moisten the wheat and adjust its moisture content to 15.9%, use a sand roller rice mill to grind the quinoa with a grinding rate of 16.1%, then mix the quinoa with ice water at a mass ratio of 1:4, and separate the quinoa germ by flotation; put the separated quinoa germ in a wall breaking machine, add water to pulp at a material-liquid ratio of 1:4, adjust the slurry pH to 5.0, add 2.0% of the mass of quinoa germ cell wall degrading enzyme, after 30℃ ultrasonic assisted enzymolysis for 0.5h, inactivate the enzyme in a 90℃ constant temperature water bath for 10min, cool to room temperature and pass through a 140-mesh sieve; add ethanol to the enzymatic hydrolysis slurry with a final ethanol concentration of 50%, stir and mix, centrifuge at low temperature, remove the upper liquid, and freeze-dry the solid phase to obtain quinoa concentrated protein powder.

[0032] Example 4

[0033] Take quinoa raw materials with uniform size, full grains and no impurities, add water to moisten the wheat to adjust its moisture content to 16.6%, use a sand roller rice mill to grind the quinoa with a grinding rate of 18.5%, then mix the quinoa with ice water at a mass ratio of 1:3, and separate the quinoa germ by flotation; put the separated quinoa germ in a wall breaking machine, add water to pulp at a material-liquid ratio of 1:4, adjust the slurry pH to 6.0, add cell wall degrading enzyme of 2.0% of the mass of quinoa germ, perform ultrasonic assisted enzymolysis at 30°C for 2.0h, inactivate the enzyme in a constant temperature water bath at 90°C for 10min, cool to room temperature and pass through a 100-mesh sieve; add ethanol to the enzymatic hydrolysis slurry with a final ethanol concentration of 50%, stir and mix, centrifuge at low temperature, remove the upper liquid, and obtain quinoa concentrated protein powder after solid phase freeze-drying.

[0034] Comparative Example 1

[0035] The difference between this comparative example and Example 2 is that no cell wall degrading enzyme is added in this comparative example, and other conditions are consistent with Example 2.

[0036] Comparative Example 2

[0037] The difference between this comparative example and Example 2 is that ethanol is not added in this comparative example, but is replaced by an equal volume of water, and other conditions are consistent with Example 2.

[0038] Comparative Example 3

[0039] The difference between this comparative example and Example 2 is that in this comparative example, the pH of the slurry is adjusted to 6.5, and the other conditions are consistent with those in Example 2.

[0040] Comparative Example 4

[0041] The difference between this comparative example and Example 2 is that in this comparative example, after quinoa germ is pulped, the pH of the pulp is adjusted to 8.0, and after ultrasonic-assisted extraction at 40° C. for 1 hour, the supernatant is collected by centrifugation; the pH of the supernatant is adjusted to 5.0, the upper liquid is removed by centrifugation, and quinoa protein isolate is obtained after solid phase freeze-drying.

[0042] The determination of protein content in the present invention refers to GB 5009.2-2016 "National Food Safety Standard Determination of Protein in Food", protein yield = protein content in product / protein content in quinoa germ raw material × 100%, and the determination of arginine content refers to GB 5009.124-2016 "National Food Safety Standard Determination of Amino Acids in Food".

[0043] The protein content and protein yield of the protein powder obtained in the examples of the present invention and the comparative examples are shown in Table 1.

[0044] Table 1

[0045]

[0046] From the above results, it can be seen that the protein (dry basis) content in the products obtained in Examples 1 to 4 is higher than 75%, and the protein yield is above 95%, achieving the green concentrated preparation and efficient utilization of quinoa protein, and the arginine content is ≥7.0g / 100g protein. Comparative Examples 1 to 3 have a low protein content in the process flow without enzymatic hydrolysis or alcohol extraction or changing the system pH, and the concentrated preparation effect of quinoa protein is poor, especially pH has a greater impact on the product protein yield and arginine content; Comparative Example 4 uses traditional alkali extraction and acid precipitation to separate quinoa protein, although the obtained product protein purity is higher, but the strong alkali extraction conditions are not mild enough, the obtained product color is darker, and the protein yield and arginine content are lower than the method used in the present invention.

[0047] The arginine content in the quinoa concentrated protein powder obtained by the present invention is ≥7.0g / 100g protein, which is higher than that of plant protein powders such as wheat protein, corn protein, and soybean protein, and can be used as a dietary supplement for specific groups of people.

[0048] The invention uses protein-rich quinoa germ as a raw material, removes non-protein components of quinoa through processes such as enzymatic hydrolysis, ultrasound, and alcohol extraction, and finally obtains arginine-rich quinoa protein concentrate powder with no organic solvent residue and protein not denatured by enzymatic hydrolysis. The process is simple, energy-saving and emission-reducing, and the powder can be widely used in industrial production.

Claims

1. A quinoa concentrated protein powder rich in arginine, characterized in that: The quinoa concentrated protein powder has a protein content (dry basis) of ≥75%, and an arginine content of ≥7.0 g / 100 g protein.

2. The method for preparing the arginine-rich quinoa protein concentrate powder according to claim 1, characterized in that: The steps include: 1) Grinding the quinoa to peel off the seed coat, then placing it in low-temperature water with a volume of 2 to 4 times the mass of the quinoa and stirring it for 5 to 20 minutes, and flotation separation to obtain quinoa germ, wherein the water temperature is 5 to 15° C.; 2) adding water to the obtained quinoa germ to obtain a quinoa germ homogenate, adding a cell wall degrading enzyme, ultrasonicating at 30 to 50° C. for 0.5 to 4 h, then inactivating the enzyme at 85 to 95° C., and passing through a 100 to 200 mesh sieve to obtain an enzymatic slurry; the amount of the cell wall degrading enzyme added is 1.0 to 3.0% of the mass of the quinoa germ; 3) adding ethanol to the enzymatic slurry to a final ethanol concentration of 30-60%, removing the upper liquid after low-temperature centrifugation at 10-15° C., and drying the solid to obtain quinoa concentrated protein powder.

3. The method for preparing quinoa protein concentrate powder as claimed in claim 2, characterized in that: In step 1), the reduction rate of quinoa during grinding is 13-20%.

4. The method for preparing quinoa concentrated protein powder as claimed in claim 2, characterized in that: In step 2), the pH of the quinoa germ homogenate is adjusted to 4.0-6.0 before adding the cell wall degrading enzyme.

5. The method for preparing quinoa concentrated protein powder as claimed in claim 2, characterized in that: In step 2), the cell wall degrading enzyme is one or more of cellulase, hemicellulase, xylanase and pectinase.

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