High-purity zein as well as industrial preparation method and application thereof

Abstract

The invention discloses high-purity zein as well as an industrial preparation method and application thereof. The invention belongs to the technical field of corn deep processing. The method comprises the following steps: firstly, removing starch in the corn protein powder by using a high-temperature amylase technology, then removing fat and pigments in the corn protein powder by using a sodium carbonate aqueous solution with the pH value of 8-9, then obtaining a zein extracting solution by using a pipeline type continuous ultrasonic countercurrent extraction technology, and decolorizing by using activated carbon, concentrating and drying to obtain the zein. The zein prepared through the method is white solid powder, the purity reaches 98% or above, the zein can be applied to the food and medicine industry, starch enzymatic hydrolysate, fat and pigment obtained in the preparation process can be fully utilized, and the utilization efficiency of the corn protein powder is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep processing of corn, and particularly relates to a high-purity zein and an industrial preparation method and application thereof. Background Art

[0002] Zein is the main storage protein in corn, with unique solubility. It is insoluble in water or anhydrous alcohols, but can be dissolved in an aqueous alcohol solution with a volume fraction of 60% - 95%. Zein is composed of special amino acids, and there are a large number of hydrophobic amino acids in its molecule. It lacks amino acids with charged acidic, basic, and polar groups, and lacks essential amino acids such as lysine and tryptophan, so its nutritional value is low. The special amino acid composition and sequence endow zein with properties such as film-forming property, antioxidant property, adhesiveness, biodegradability, biocompatibility, and gelation, and it has wide application value in the fields of packaging, biomedicine, fiber materials, functional foods, etc., and is a promising biological macromolecule material.

[0003] Regarding the unique solubility of zein, at present, aqueous organic solvents are mainly used for extraction. However, the starch, fat, pigments (such as β-carotene, lutein, and zeaxanthin), and odor substances remaining in the zein raw materials are also dissolved out, resulting in difficulties in the zein extraction process. Moreover, the final product shows yellow color, and the chromaticity cannot meet the application requirements of the international market, which limits the application of zein in the food and pharmaceutical fields. Patent CN201610358358.0 discloses a method for separating and extracting corn yellow pigment and zein from corn protein powder by using membrane separation technology. However, the oil in the extract and the starch dissolved in the extract are very easy to adhere to the separation membrane, making it difficult to separate. Patent CN201610930420.9 uses subcritical extraction technology to remove pigments and fats from corn protein powder, and then uses a kettle-type ultrasonic dynamic countercurrent extraction to prepare corn protein powder. However, the subcritical extraction technology used cannot remove the starch in the corn protein powder, and the starch is likely to react with water to form viscous substances during the subsequent extraction process, hindering the extraction of zein. In addition, for the kettle-type ultrasonic dynamic extraction process used, the viscous corn protein material agglomerates in the kettle and cannot be stirred, resulting in low extraction efficiency and difficult operation.

[0004] Impurities such as starch, fat, and pigments in corn protein powder cause great difficulties in the zein extraction process and seriously affect the product purity. In addition, the intermittent zein extraction process is difficult to industrialize. Based on the rich resource advantages of corn protein powder and the wide application value of high-quality zein, it is urgent to invent a preparation method for high-purity zein. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a high-purity zein and an industrial preparation method and application thereof.

[0006] The technical solution of the present invention:

[0007] One of the purposes of the present invention is to provide an industrial preparation method of high-purity zein, and the method is carried out according to the following steps:

[0008] S1: Disperse corn gluten meal in water, then add high-temperature amylase for enzymatic hydrolysis, and after centrifugation, obtain a starch-removed product;

[0009] S2: Disperse the starch-removed product in an aqueous sodium carbonate solution with pH = 8 - 9 for degreasing and decolorization treatment, and after centrifugation, obtain a degreased and decolorized product;

[0010] S3: Use a high-concentration alcohol solution as the extraction solution, and under the continuous ultrasonic assistance, carry out countercurrent extraction on the degreased and decolorized product in a pipeline equipment to obtain a crude zein product;

[0011] S4: Subject the crude zein product to secondary decolorization with activated carbon, concentration, and drying to obtain zein.

[0012] Further defined, the high-temperature amylase in S1 is α-amylase, and the dosage of the amylase is 8 - 16 activity units / gram of starch.

[0013] Further defined, the enzymatic hydrolysis temperature in S1 is 60 - 80 °C, the time is 30 - 60 min, and pH = 6 - 7.

[0014] Further defined, the mass ratio of the starch-removed product to the aqueous sodium carbonate solution in S2 is 1:(3 - 6).

[0015] Further defined, the treatment temperature in S2 is 60 - 80 °C, and the time is 30 - 90 min.

[0016] Further defined, the high-concentration alcohol solution in S3 is an ethanol aqueous solution, an isopropanol aqueous solution, or a dipropylene glycol dimethyl ether / ethanol / aqueous solution, and the concentration is 85 - 95 wt.%.

[0017] Even further defined, the mass ratio of dipropylene glycol dimethyl ether to ethanol in the dipropylene glycol dimethyl ether / ethanol / aqueous solution is (2.8 - 18):1.

[0018] Further defined, the mass ratio of the degreased and decolorized product to the high-concentration alcohol solution in S3 is 1:(5 - 10).

[0019] Further defined, the extraction temperature in S3 is 60 - 80 °C, the residence time of the degreased and decolorized product in the pipeline is 30 - 90 min, and the ultrasonic frequency is 10 - 50 KHz.

[0020] Further limitation: in S4, the dosage of activated carbon is 2-10% of the mass of zein in the extraction solution.

[0021] Further limitation: in S4, the decolorization temperature is 40-60 °C and the time is 30-60 min.

[0022] The second object of the present invention is to provide an application of the enzymatically hydrolyzed sugar solution obtained by the above method in the field of microbial fermentation.

[0023] The third object of the present invention is to provide a highly pure zein prepared by the above method, and the zein is a white solid powder with a purity of ≥98%.

[0024] The fourth object of the present invention is to provide an application of the highly pure zein prepared by the above method in the fields of food and medicine.

[0025] The fifth object of the present invention is to provide an application of the above method in improving the utilization rate of corn protein powder.

[0026] The beneficial effects of the present invention compared with the prior art:

[0027] (1) The present invention designs a preparation method of highly pure zein. First, the corn protein powder is pretreated with high-temperature amylase to enzymatically hydrolyze the residual starch in the corn protein powder, avoiding the formation of agglomerates that are viscous and cannot be stirred and dispersed when the starch reacts with the extractant during the subsequent extraction process. Moreover, the sugar solution obtained by enzymatically hydrolyzing the starch can be used as a raw material for microbial fermentation.

[0028] (2) The present invention designs a preparation method of highly pure zein. After de-starching, the corn protein powder is treated by dissolving it in hot alkaline water to remove the residual fat and most of the pigments in the corn protein powder under alkaline conditions. On the one hand, using hot alkaline water treatment is environmentally friendly and economical. On the other hand, removing fat and pigments avoids the influence of such impurities on the subsequent extraction process and products.

[0029] (3) The present invention adopts a continuous ultrasonic-assisted dispersion in a pipeline for countercurrent extraction. The corn protein powder is fed into the extraction tank from the feeding port at one end of the pipeline-type continuous countercurrent ultrasonic extractor, and at the same time, the extraction solvent is fed from the solvent feeding port at the other end. Under the action of the propeller, the corn protein powder slowly advances towards the slag discharge port, while the extraction solvent flows in the opposite direction to the movement of the material. When the material and the extraction solvent are fed, the ultrasonic vibrator is turned on for assisted extraction. On the one hand, the dispersion of corn protein powder in the extractant and the dissolution of zein are enhanced through the ultrasonic cavitation effect; on the other hand, by increasing the concentration of the extractant, the extraction efficiency is improved; in addition, by heating and insulating the extraction tank at 60-80 °C, the extraction efficiency is further enhanced. At the same time, compared with the ax-type ultrasonic countercurrent extraction, the residence time of the material in the pipeline-type continuous ultrasonic countercurrent extractor can be conveniently controlled by controlling the speed of the material propeller, and the problem that the material agglomerates and cannot fully contact with the extraction agent is avoided.

[0030] (4) The present invention decolorizes the extract by adding activated carbon, and obtains high-purity zein through concentration and drying.

[0031] (5) In the preparation method of high-purity zein of the present invention, the entire process uses water and environmentally friendly alcohol solvents, which are green and healthy, and the solvents can be recycled without polluting the environment. The zein obtained by this preparation method has a purity of over 98%, and has no variegated color and peculiar smell. Detailed implementation mode

[0032] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation mode of the present invention is made in combination with the embodiments of the specification.

[0033] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0034] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that can be included in at least one implementation mode of the present invention. The "in one embodiment" that appears in different places in this specification does not all refer to the same embodiment, nor is it a separate or selectively exclusive embodiment from other embodiments.

[0035] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used, unless otherwise specified, are all conventional materials, reagents, methods and instruments in the art, and those skilled in the art can obtain them through commercial channels.

[0036] The pipeline continuous countercurrent ultrasonic extractor used in the following examples is a commercially available product, with specific parameters: the inner diameter of the extraction tube is 400 mm, there are 12 extraction tubes, including 3 soaking extraction tubes and 9 ultrasonic extraction tubes, the ultrasonic power is 48 kw, and the total effective volume is about 3000 liters.

[0037] The corn gluten meal used in the following examples is a commercially available product, with specific parameters: 80 mesh, with a protein content of 67%, starch of 12%, fat and pigment of 6%, cellulose of 1%, ash of 2%, and moisture of 12%.

[0038] Example 1. The industrial preparation method of high-purity zein in this example is carried out according to the following steps:

[0039] (1) Disperse 500 kg of corn gluten meal into 5 times the volume of water, heat to 70 °C, adjust the pH to 6.5, add high-temperature α-amylase according to the ratio of 12 enzyme activity units / g of starch, keep warm and stir for 50 min, then filter under pressure and wash with water to obtain 800 kg of wet zein with de-starch (water content 55%).

[0040] (2) Disperse the de-starch zein into an aqueous sodium carbonate solution with pH = 9 (mass ratio 1:3), heat to 80 °C, keep warm and stir for 80 min, then cool to 40 °C, centrifuge and wash until neutral, and dry to obtain 420 kg of degreased and decolorized product (60 mesh, water content 12%).

[0041] (3) Put the obtained 420 kg of degreased and decolorized product into the extraction chamber from the feeding port of the pipeline continuous countercurrent ultrasonic extractor, adjust the rotation speed of the rotating motor so that the residence time of the degreased and decolorized product in the pipeline is 50 min. At the same time, put 2200 kg of ethanol aqueous solution with a concentration of 93% into the solvent feeding port at the other end. The degreased and decolorized product is pushed towards the slag outlet under the action of the propeller, while the extractant flows in the opposite direction to the movement of the degreased and decolorized product. Start the ultrasonic vibrator for auxiliary extraction while putting in the degreased and decolorized product and the extractant; the extraction temperature is 70 °C, and the ultrasonic frequency is 25 KHz.

[0042] (4) Add 20 kg of food-grade decolorizing activated carbon to 3000 liters of the extractant treated in step (3), stir and decolorize at 50 °C for 40 min, remove the activated carbon by centrifugal filtration, and after concentration and drying of the obtained decolorized extract filtrate, obtain 125 kg of zein with a purity of 98.5%.

[0043] Example 2. The industrial preparation method of high-purity zein in this example is carried out according to the following steps:

[0044] (1) Disperse 500 kg of corn protein powder into 5 times its volume of water, heat to 70 °C, adjust the pH to 6.5, add high-temperature α-amylase at a ratio of 12 enzyme activity units per gram of starch, keep warm and stir for reaction for 50 min, then filter press and wash with water to obtain 800 kg of starch-free wet zein (water content 55%).

[0045] (2) Disperse the starch-free zein into a sodium carbonate aqueous solution with pH = 9 (mass ratio 1:6), heat to 80 °C, keep warm and stir for 80 min, then cool to 40 °C, centrifuge and wash until neutral, and dry to obtain 420 kg of defatted and decolorized product (60 mesh, water content 12%).

[0046] (3) Feed the obtained 420 kg of defatted and decolorized product into the extraction chamber from the feeding port of the pipeline continuous countercurrent ultrasonic extractor, adjust the rotation speed of the rotating motor so that the residence time of the defatted and decolorized product in the pipeline is 50 min. At the same time, feed 2300 kg of isopropyl alcohol aqueous solution with a concentration of 90% from the solvent feeding port at the other end. Under the action of the propeller, the defatted and decolorized product is pushed towards the slag discharge port, while the extract flows in the opposite direction to the movement of the defatted and decolorized product. When the defatted and decolorized product and the extract are fed, turn on the ultrasonic vibrator for auxiliary extraction; the extraction temperature is 70 °C and the ultrasonic frequency is 25 KHz.

[0047] (4) Add 20 kg of food-grade decolorizing activated carbon to 3000 L of the extract treated in step (3), stir and decolorize at 50 °C for 40 min, remove the activated carbon by centrifugal filtration, and after concentrating and drying the obtained decolorized extract filtrate, obtain 120 kg of zein with a purity of 98.8%.

[0048] Example 3. The industrial preparation method of high-purity zein in this example is carried out according to the following steps:

[0049] (1) Disperse 500 kg of corn protein powder into 5 times its volume of water, heat to 70 °C, adjust the pH to 6.5, add high-temperature α-amylase at a ratio of 12 enzyme activity units per gram of starch, keep warm and stir for reaction for 50 min, then filter press and wash to obtain 800 kg of starch-free wet zein (water content 55%).

[0050] (2) Disperse the starch-free zein into a sodium carbonate aqueous solution with pH = 9 (mass ratio 1:4), heat to 80 °C, keep warm and stir for 80 min, then cool to 40 °C, centrifuge and wash until neutral, and dry to obtain 420 kg of defatted and decolorized product (60 mesh, water content 12%).

[0051] (3) Feed the obtained 420 kg of defatted and decolorized product into the extraction chamber from the feeding port of the pipeline continuous countercurrent ultrasonic extractor. Adjust the rotation speed of the rotating motor so that the residence time of the defatted and decolorized product in the pipeline is 50 min. At the same time, feed 2400 kg of a 95% dipropylene glycol dimethyl ether / ethanol / aqueous solution (dipropylene glycol dimethyl ether / ethanol, w / w = 70 / 25) from the solvent feeding port at the other end. Under the action of the propeller, the defatted and decolorized product is propelled towards the slag discharge port, while the extractant flows in the opposite direction to the movement of the defatted and decolorized product. When the defatted and decolorized product and the extractant are fed, turn on the ultrasonic vibrator for auxiliary extraction; the extraction temperature is 60 °C and the ultrasonic frequency is 25 KHz.

[0052] (4) Add 20 kg of food-grade decolorizing activated carbon to 3000 L of the extractant treated in step (3), stir and decolorize at 50 °C for 40 min, remove the activated carbon by centrifugal filtration, and after concentration and drying of the obtained decolorized extract filtrate, obtain 115 kg of zein with a purity of 99.0%.

[0053] Example 4. The industrial preparation method of high-purity zein in this example is carried out according to the following steps:

[0054] (1) Disperse 500 kg of corn gluten meal into 5 times the volume of water, heat to 70 °C, adjust the pH to 6.5, add high-temperature α-amylase according to the ratio of 12 activity units / g of starch, keep warm and stir for 50 min, then filter press and wash with water to obtain 800 kg of starch-free wet zein (water content 55%).

[0055] (2) Disperse the starch-free zein into an aqueous sodium carbonate solution with pH = 9 (mass ratio 1:4), heat to 80 °C, keep warm and stir for 80 min, then cool to 40 °C, centrifuge and wash until neutral, and dry to obtain 420 kg of defatted and decolorized product (60 mesh, water content 12%).

[0056] (3) Feed the obtained 420 kg of defatted and decolorized product into the extraction chamber from the feeding port of the pipeline continuous countercurrent ultrasonic extractor. Adjust the rotation speed of the rotating motor so that the residence time of the defatted and decolorized product in the pipeline is 50 min. At the same time, feed 2400 kg of an 85% dipropylene glycol dimethyl ether / ethanol / aqueous solution (dipropylene glycol dimethyl ether / ethanol, w / w = 75 / 10) from the solvent feeding port at the other end. Under the action of the propeller, the defatted and decolorized product is propelled towards the slag discharge port, while the extractant flows in the opposite direction to the movement of the defatted and decolorized product. When the defatted and decolorized product and the extractant are fed, turn on the ultrasonic vibrator for auxiliary extraction; the extraction temperature is 60 °C and the ultrasonic frequency is 25 KHz.

[0057] (4) Add 20 kg of food-grade decolorizing activated carbon to 3,000 liters of the extract after the treatment in step (3), stir and decolorize at 50 °C for 40 min, remove the activated carbon by centrifugal filtration. After the obtained decolorized extract filtrate is concentrated and dried, 110 kg of zein is obtained with a purity of 99.2%.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that steps (1) and (2) are omitted, and step (3) is directly carried out. Extraction is carried out in a pipeline continuous countercurrent ultrasonic extractor according to the same ratio of corn protein powder and extract, and the extraction conditions are the same as those in Example 1. It is found that it is difficult to push the material in the pipeline, forming a viscous agglomerate, and it is difficult to extract zein.

[0060] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. An industrial preparation method of high-purity zein, characterized in that, it is carried out according to the following steps: S1: Disperse corn gluten meal in water, then add high-temperature amylase for enzymatic hydrolysis. After centrifugation, an enzymatically hydrolyzed sugar solution and a starch-removed product are obtained; S2: Disperse the starch-removed product in a sodium carbonate aqueous solution with pH = 8 - 9 for degreasing and decolorization treatment. After centrifugation, a degreased and decolorized product is obtained; S3: Using a high-concentration alcohol solution as the extraction solution, under the continuous ultrasonic assistance, carry out countercurrent extraction on the degreased and decolorized product in a pipeline-type device to obtain a zein extraction solution; S4: Subject the zein extraction solution to secondary decolorization with activated carbon, concentrate and dry it to obtain zein.

2. The method according to claim 1, characterized in that, in S1, the high-temperature amylase is α-amylase, the dosage of the amylase is 8 - 16 activity units per gram of starch, the enzymatic hydrolysis temperature is 60 - 80 °C, the time is 30 - 60 min, and pH = 6 - 7.

3. The method according to claim 1, characterized in that, in S2, the mass ratio of the starch-removed product to the sodium carbonate aqueous solution is 1:(3 - 6), the treatment temperature is 60 - 80 °C, and the time is 30 - 90 min.

4. The method according to claim 1, characterized in that, in S3, the high-concentration alcohol solution is an ethanol aqueous solution, an isopropyl alcohol aqueous solution or a dipropylene glycol dimethyl ether / ethanol / aqueous solution, with a concentration of 85 - 95 wt.%, the mass ratio of the degreased and decolorized product to the high-concentration alcohol solution is 1:(5 - 10), the extraction temperature is 60 - 80 °C, the residence time of the degreased and decolorized product in the pipeline is 30 - 90 min, and the ultrasonic frequency is 10 - 50 KHz.

5. The method according to claim 4, characterized in that, in the dipropylene glycol dimethyl ether / ethanol / aqueous solution, the mass ratio of dipropylene glycol dimethyl ether to ethanol is (2.8 - 18):

1.

6. The method according to claim 1, characterized in that, in S4, the dosage of the activated carbon is 2 - 10% of the mass of zein in the extraction solution, the decolorization temperature is 40 - 60 °C, and the time is 30 - 60 min.

7. Application of the enzymatically hydrolyzed sugar solution obtained in the method according to any one of claims 1 - 6 in the field of microbial fermentation.

8. The high-purity zein prepared by the method according to any one of claims 1 - 6, characterized in that, the purity ≥ 98%.

9. Application of the high-purity zein prepared by the method according to any one of claims 1 - 6 in the fields of food and medicine.

10. Application of the method according to any one of claims 1 - 6 in improving the utilization rate of corn gluten meal.