Wheat bran alkyl resorcinol enriched product, starch compound of wheat bran alkyl resorcinol enriched product, preparation method and application of starch compound

Abstract

The invention provides a wheat bran alkyl resorcinol enriched product, a starch compound of the wheat bran alkyl resorcinol enriched product, a preparation method of the wheat bran alkyl resorcinol enriched product and application of the wheat bran alkyl resorcinol enriched product. Comprising the following steps: dry mechanical dissociation of a wheat bran structural layer, dry physical enrichment, electrostatic field separation and purification of a wheat bran intermediate layer, subcritical propane extraction, multi-temperature-section crystallization and purification, and preparation of the alkylresorcinol-starch compound. The method for separating and enriching the intermediate layer and the ARs from the wheat bran is green, simple and efficient, and the purity and the extraction rate of the ARs can be considered; meanwhile, the ARs-starch compound prepared on the basis of the extracted wheat bran ARs has the slow digestion characteristic, the anti-inflammatory function and the like, and efficient extraction and food utilization of the alkyl resorcinol-starch compound in the wheat bran can be achieved.

Description

Technical Field

[0001] The invention belongs to the field of deep processing of agricultural products and relates to a wheat bran alkylresorcinol enrichment and a starch complex thereof as well as a preparation method and application thereof. Background Art

[0002] Alkylresorcinols (ARs) are natural polyketone non-isoprene-derived phenols in which the 5-position of the benzene ring in 1,3-resorcinol is substituted by an odd-numbered alkyl or alkenyl group. In nature, ARs are mainly derived from higher plants, especially grains such as rye and wheat, and only exist in small amounts in lower plants (algae, mosses, fungi) and some bacteria. In grain grains, ARs are almost entirely concentrated in the bran, and grain structures such as the endosperm and germ contain almost no ARs. Therefore, ARs can generally be used as a marker for whole grain foods. A large number of nutritional and physiological studies have shown that ARs have a variety of beneficial physiological functions, such as antibacterial, antimutagenic, anticancer, and regulation of glucose and lipid metabolism. Therefore, the extraction and food utilization of ARs have received much attention.

[0003] Wheat is one of the three major staple foods in my country. As the main by-product of wheat flour production, wheat bran has a complex structure and rich nutrition. It is composed of pericarp, seed coat, transparent layer, endosperm and other structural layers. Among them, the endocarp, seed coat and transparent layer are also called the middle layer, accounting for about 20% to 30% of the weight of the bran, and are the enriched parts of alkylresorcinols (ARs).

[0004] At present, most of the ARs are extracted from wheat bran as raw material. Wheat bran is rich in oil, especially the aleurone layer cell contents contain a large amount of free fat, which makes the separation and purification of ARs in wheat bran difficult. Therefore, the different structural layers of wheat bran are dissociated and the middle layer is enriched, which is an efficient and preferred method for extracting ARs. At present, the technical method of dry separation of the middle layer of wheat bran is still blank. In the public patents (CN113000091AA, CN115428892A, CN115428892A), a peeling machine is used to perform layered peeling to obtain the wheat bran structural layer, but it is difficult to obtain a high-purity middle layer. Jiangsu University discloses a method for separating wheat bran structural cell clusters (CN115428892A), first using electrostatic separation of the aleurone layer and the non-aleurone layer, and then using dielectrophoresis or centrifugal sedimentation to separate the middle layer and the outer peel of the non-aleurone layer. The separation medium used is an organic solvent, which is difficult to use for edible purposes. In the public patents on separation and purification of ARs (CN110638798A, CN110002962A, CN110343032A), silica gel column chromatography and high performance liquid chromatography are mainly used, which are time-consuming and have a small processing volume. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a method for preparing a wheat bran alkylresorcinol enriched product and a starch complex thereof. The method uses wheat bran as a raw material, extracts the alkylresorcinol enriched product through physical methods such as impact crushing, dry classification, electrostatic field separation, subcritical fluid extraction and freezing crystallization, and prepares the alkylresorcinol-starch complex, thereby improving the extraction efficiency of the wheat bran alkylresorcinol. The method is simple and efficient to operate, is green and environmentally friendly, and is suitable for large-scale separation and extraction.

[0006] The present invention also provides a wheat bran alkylresorcinol enriched material and a starch composite thereof. The wheat bran alkylresorcinol enriched material and the starch composite thereof are prepared according to the preparation method of the wheat bran alkylresorcinol enriched material and the starch composite thereof.

[0007] The present invention also provides an application of a wheat bran alkylresorcinol enriched material and a starch composite thereof, and the wheat bran alkylresorcinol enriched material and the starch composite thereof prepared according to the preparation method of the wheat bran alkylresorcinol enriched material and the starch composite thereof are applied in food processing.

[0008] The present invention achieves the above technical objectives through the following technical means.

[0009] The preparation method of the wheat bran alkylresorcinol enriched material and the starch composite thereof mainly comprises key technologies such as dry mechanical dissociation of wheat bran structural layer, dry physical enrichment of wheat bran middle layer, electrostatic field separation and purification of wheat bran middle layer, subcritical extraction of wheat bran ARs, multi-temperature section freezing crystallization purification of ARs, and preparation of ARs-starch composite.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] A method for preparing a wheat bran alkylresorcinol enriched product and a starch composite thereof comprises the following steps:

[0012] Step (1) dry mechanical dissociation: dry centrifugal impact pulverization of wheat bran is performed to achieve interlayer dissociation of the wheat bran aleurone layer, the outer pericarp and the middle layer to obtain a wheat bran structure layer powder;

[0013] Step (2) dry physical enrichment: dry-enriching the wheat bran structure layer powder separated in step (1) by screening, airflow classification and a powder purifier to obtain classified wheat bran powder;

[0014] Step (3) electrostatic field separation and purification: using the wheat bran powder after screening and airflow classification in step (2) as raw material, using dielectrophoresis to separate the aleurone layer and the non-aleurone layer, the non-aleurone layer being the middle layer and the outer pericarp, and then using triboelectric separation to separate the middle layer and the outer pericarp to obtain a high-purity middle layer powder;

[0015] Step (4) subcritical propane extraction: the high-purity intermediate layer powder obtained in step (3) is subjected to low-temperature extraction using subcritical propane as an extraction solvent and ethanol as an entrainer, and finally desolventizing and evaporating to obtain a crude extract of alkylresorcinol;

[0016] Step (5) multi-temperature crystallization purification: the crude alkylresorcinol extract obtained in step (4) is dissolved in a methanol solution, the methanol solution of the crude alkylresorcinol extract is subjected to multi-temperature freeze crystallization and then centrifuged to obtain a frozen supernatant and a crystalline precipitate, respectively, and after drying and desolventizing, a crystalline precipitate and a supernatant solute containing alkylresorcinol are obtained;

[0017] Step (6) Preparation of alkylresorcinol-starch complex: Add wheat starch and heat it moderately to swell it, and mix it with the ethanol solution containing the crystalline precipitate of step (5), and then wash, centrifuge and freeze-dry to obtain the alkylresorcinol-starch complex.

[0018] In the above scheme, the particle size of the wheat bran in step (1) is greater than 500 μm, the water content is not higher than 10%, the linear speed of the dry centrifugal impact crushing is greater than 70 m / s, and the impact end radius is ≤0.5 mm.

[0019] In the above scheme, the sieving aperture in step (2) is 100-200 μm; the suspension speed of the airflow classifier or powder purifier is 0.5-0.8 m / s.

[0020] In the above scheme, step (3) uses dielectrophoresis to separate the non-paleurone layer from the pasteurone layer, and the electric field strength is not less than 2kv / cm. Preferably, the electric field strength is 2-5kv / cm, and the movement rate of the powder under the electric field is 1-5m / s.

[0021] In the above scheme, after step (3), the intermediate layer and the outer peel powder are separated by friction electrostatic separation, the air flow velocity is 1-3 m / s, the friction pipe material is silica gel or polytetrafluoroethylene, the voltage of the electrostatic field used is 30-40 kV; the temperature of the electrostatic field separation is 20-30° C., and the humidity is 30-40%; the moisture content of the wheat bran powder is not higher than 10%.

[0022] In the above scheme, the step (4) uses subcritical propane combined with ethanol entrainer to extract alkylresorcinol in the middle layer of wheat bran, the added amount of the entrainer is 0.5% to 1%, and the mass ratio of the extraction solvent volume to the wheat bran is in the range of 4:1 to 20:1; the extraction temperature is lower than 45°C, at 25 to 40°C, the extraction time is 30 to 60 minutes, and the number of extraction cycles is 3 to 5 times; preferably, the extraction temperature is 30 to 40°C, the extraction cycle is 3 times, and the single extraction time is 30 minutes.

[0023] In the above scheme, the multi-stage freezing crystallization temperature in step (5) is -80°C to 4°C, the freezing crystallization time is 6 to 12 hours, and methanol solution is used as the freezing medium; preferably, the freezing crystallization time is 6 to 8 hours at 4°C, and the centrifugal supernatant is further frozen in a -80°C low-temperature refrigerator for 12 hours, and then taken out and quickly frozen and centrifuged at 7000g and -10°C for 10 minutes.

[0024] In the above scheme, in step (6), the starch water bath heating temperature is 60-70° C., and the heating time is 40-60 min; the amount of alkylresorcinol ethanol extract is 3% of the starch dry basis, and the water bath stirring time is 30-60 min; preferably, the starch and water are heated in a water bath at about 65° C. for 10 min, and then the alkylresorcinol ethanol extract accounting for 3% of the starch dry basis is added, and the water bath stirring is continued for 60 min, and then the mixture is rapidly cooled to room temperature and centrifuged at 4000 rpm, and finally washed with 50% ethanol solution to obtain the alkylresorcinol-starch complex.

[0025] A wheat bran alkylresorcinol enriched material and a starch composite thereof are prepared according to the preparation method of the wheat bran alkylresorcinol enriched material and a starch composite thereof.

[0026] The invention discloses an application of a wheat bran alkylresorcinol enriched material and a starch composite thereof, and the application of the wheat bran alkylresorcinol enriched material and the starch composite thereof prepared according to the preparation method of the wheat bran alkylresorcinol enriched material and the starch composite thereof in food processing.

[0027] Compared with the prior art, the beneficial effects of the present invention include:

[0028] 1. The present invention realizes the dissociation of the middle layer from other wheat bran structural layers based on a dry centrifugal impact method, adopts a dry separation technology to obtain a complete middle layer, avoids the loss of nutrients in the wheat bran caused by processing methods such as wet methods and enzyme methods, ensures the maximum retention of ARs in the middle layer, and has the advantages of being green, energy-saving and efficient.

[0029] 2. The present invention adopts triboelectric separation to separate the endosperm from the non-endosperm, the middle layer from the exocarp, removes the exocarp rich in pollutants and the endosperm rich in oil, and retains the middle layer rich in ARs. The purity of the obtained middle layer is 75%-80%, which helps to improve the extraction efficiency of wheat bran ARs.

[0030] 3. The present invention uses subcritical propane-ethanol as solvent to extract ARs from wheat bran. Compared with traditional solvent extraction, it has the advantages of low temperature, less solvent residue, strong selectivity, high efficiency, etc., and has low equipment cost, which is suitable for large-scale extraction and preparation.

[0031] 4. The present invention uses a multi-temperature freezing crystallization method to purify ARs, which is simple and efficient to operate, green and environmentally friendly, can selectively separate saturated ARs and unsaturated ARs, and is suitable for large-scale separation and extraction.

[0032] 5. The present invention uses ARs to prepare alkylresorcinol-starch complexes, thereby improving their nutritional and health functions and the food application of ARs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : Schematic diagram of the extraction process of wheat bran ARs and the preparation process of their starch complexes.

[0034] Figure 2 : The middle layer enrichment of wheat bran after separation and enrichment in electrostatic field.

[0035] Figure 3 : Comparison of ARs content in the supernatant and crystals after freezing crystallization

[0036] Figure 4 : Comparative liquid chromatogram of ARs content in supernatant and crystals after multi-temperature freezing crystallization.

[0037] Figure 5 : Infrared spectrum of starch-ARs complex. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto. The reagents, materials, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0039] Combination Figure 1 As shown, a method for preparing a wheat bran alkylresorcinol enriched material and a starch composite thereof comprises the following steps:

[0040] Step (1) dry mechanical dissociation: dry centrifugal impact pulverizing the wheat bran to achieve interlayer dissociation of the wheat bran aleurone layer, the outer pericarp and the middle layer to obtain a wheat bran structure layer powder; the particle size of the wheat bran is greater than 500 μm, the water content is not higher than 10%, the linear speed of the dry centrifugal impact pulverization is greater than 70 m / s, and the impact end radius is ≤0.5 mm.

[0041] The present invention realizes the dissociation of the middle layer from other wheat bran structural layers based on a dry centrifugal impact method, adopts a dry separation technology to obtain a complete middle layer, avoids the loss of nutrients in the wheat bran caused by processing methods such as wet methods and enzyme methods, ensures the maximum retention of ARs in the middle layer, and has the advantages of being green, energy-saving and efficient.

[0042] Step (2) dry physical enrichment: dry-enriching the wheat bran structure layer powder separated in step (1) by screening, airflow classification and a powder purifier to obtain classified wheat bran powder; the screening aperture is 100-200 μm; the suspension speed of the airflow classification or the powder purifier is 0.5-0.8 m / s.

[0043] Step (3) electrostatic field separation and purification: the wheat bran powder after screening and airflow classification in step (2) is used as raw material, and the dielectrophoresis method is used to separate the aleurone layer and the non-aleurone layer, the non-aleurone layer is the middle layer and the outer peel, and then the middle layer and the outer peel are separated by friction electrophoresis to obtain high-purity middle layer powder; the dielectrophoresis method is used to separate the non-aleurone layer from the aleurone layer, the electric field strength is not less than 2kv / cm, preferably, the electric field strength is 2-5kv / cm, and the movement speed of the powder under the electric field is 1-5m / s; the friction electrophoresis method is then used to separate the middle layer and the outer peel powder, the air flow velocity is 1-3m / s, the friction pipeline material is silica gel or polytetrafluoroethylene, and the voltage of the electrostatic field used is 30-40kV; the temperature of the electrostatic field separation is 20-30°C, and the humidity is 30-40%; the water content of the wheat bran powder is not higher than 10%.

[0044] The present invention adopts triboelectric separation to separate the endosperm from the non-endosperm layer, the middle layer from the exocarp, removes the exocarp rich in pollutants and the endosperm rich in oil, retains the middle layer rich in ARs, and the obtained middle layer has high purity, which helps to improve the extraction efficiency of wheat bran ARs.

[0045] Step (4) subcritical propane extraction: the high-purity middle layer powder obtained in step (3) is subjected to low-temperature extraction at 45° C. using subcritical propane as an extraction solvent and ethanol as an entrainer, and finally desolventizing and evaporating to obtain a crude extract of alkylresorcinol; subcritical propane is used in combination with ethanol as an entrainer to extract the alkylresorcinol in the wheat bran middle layer, the amount of the entrainer added is 0.5% to 1%, and the mass ratio of the extraction solvent volume to the wheat bran is in the range of 4:1 to 20:1; the extraction temperature is 25 to 40° C., the extraction time is 30 to 60 minutes, and the extraction cycle number is 3 to 5 times; preferably, the extraction temperature is 30 to 40° C., the extraction cycle is 3 times, and the single extraction time is 30 minutes.

[0046] The present invention adopts subcritical propane-ethanol as solvent to extract ARs in wheat bran. Compared with traditional solvent extraction, the present invention has the advantages of low temperature, less solvent residue, strong selectivity, high efficiency, etc., and has low equipment cost, and is suitable for large-scale extraction and preparation.

[0047] Step (5) multi-temperature crystallization purification: the crude alkylresorcinol extract obtained in step (4) is dissolved in a methanol solution, the methanol solution of the crude alkylresorcinol extract is subjected to multi-temperature freeze crystallization and then centrifuged to obtain a frozen supernatant and a crystalline precipitate, respectively, and after drying and desolventizing, a crystalline precipitate and a supernatant solute containing alkylresorcinol are obtained; the multi-temperature freeze crystallization temperature is -80°C to 4°C, the freeze crystallization time is 6 to 12 hours, and the methanol solution is used as a freezing medium; preferably, the freeze crystallization time is 6 to 8 hours at 4°C, the centrifuged supernatant is further frozen in a -80°C low-temperature refrigerator for 12 hours, and after being taken out, it is quickly freeze-centrifuged at 7000g and -10°C for 10 minutes.

[0048] The present invention uses a multi-temperature stage freezing crystallization method to purify ARs, which is simple and efficient to operate, green and environmentally friendly, can selectively separate saturated ARs and unsaturated ARs, and is suitable for large-scale separation and extraction.

[0049] Step (6) Preparation of alkylresorcinol-starch complex: wheat starch is added to be heated moderately to swell, and mixed with an ethanol solution containing the crystal precipitate of step (5), and then washed, centrifuged, and freeze-dried to obtain an alkylresorcinol-starch complex; the starch water bath heating temperature is 60-70° C., and the heating time is 40-60 min; the amount of alkylresorcinol ethanol extract is 3% of the starch dry basis, and the water bath stirring time is 30-60 min; preferably, the starch and water are heated in a water bath at about 65° C. for 10 min, and then 3% of the alkylresorcinol ethanol extract of the starch dry basis is added, and the water bath stirring is continued for 60 min, and the mixture is rapidly cooled to room temperature and centrifuged at 4000 rpm, and finally washed with a 50% ethanol solution to obtain the alkylresorcinol-starch complex.

[0050] Example 1

[0051] A method for preparing a wheat bran alkylresorcinol enriched product and a starch composite thereof comprises the following steps:

[0052] Mechanical dissociation and electrostatic field enrichment of wheat bran interlayer:

[0053] Weigh 10kg of coarse bran with a particle size greater than 500μm as raw material, and dry it to 7% moisture content; then, put the bran into a vertical centrifugal impact mill for crushing, the feed rate is 500g / min, the crushing disk diameter is 0.30m, and the number of revolutions is 6000r / min (~75m / s); at the same time, air flow classification is performed, the impeller diameter is 0.1m, and the classification wheel revolution is 1500r / min. Until more than 80% of the bran is crushed and classified. Then, the bran powder is classified using 100 mesh and 200 mesh sieves, and three types of bran powder are taken, namely, the upper 100 mesh sieve, the between 100 mesh and 200 mesh sieves, and the lower 200 mesh sieve. Then, the bran powder of F (100-200) is used as raw material for electrostatic field separation and enrichment. First, using dielectrophoresis with an electric field strength of 3kv / cm, the powder is transported at a rate of 1m / s under the electric field. Finally, the middle layer and the outer peel were separated by triboelectric separation. The pipe used for triboelectric charging was a PTFE pipe with a diameter of 25 mm, a feed rate of 50 g / min, and an air flow rate of 3 m / s. After triboelectric charging, the wheat flour entered a high-voltage electrostatic field composed of parallel electrode plates. The voltage of the electrostatic field was 40 kV, the distance between the electrodes was 20 cm, and the height of the electrode plates was 0.8 m. From Table 1 and Figure 2 It can be seen that after electrostatic field enrichment, the negative electrode plate can be collected and used as the intermediate layer enrichment. After three electrostatic field enrichments, the intermediate layer with a purity of 75% is obtained.

[0054] Table 1 Composition of wheat bran aleurone layer and middle layer after electrostatic field separation

[0055]

[0056] Subcritical propane extraction and cryo-crystallization enrichment of wheat bran alkylresorcinol ARs:

[0057] Subcritical propane extraction of wheat bran alkylresorcinol ARs: 500g of the middle layer enrichment was weighed and crushed to less than 100μm by an impact mill, and 3% (v / w) anhydrous ethanol was evenly sprayed as an entrainer. The wheat bran powder was wrapped with filter cloth and placed in an extraction tank, and 2.0L propane was added each time for extraction. The extraction temperature was 40°C, maintained for 30min, extracted 3 times, and the oil-soluble components obtained by extraction were collected. Finally, the extraction tank was rinsed with n-hexane, and the extracts were combined and evaporated to dryness to obtain a crude extract of alkylresorcinol ARs.

[0058] Freeze crystallization purification of ARs: 10g of subcritical propane crude extract of alkylresorcinol ARs was added to 300mL of methanol solution, and then refrigerated at 4°C for 12h, the centrifuged supernatant was frozen in a -80°C low-temperature refrigerator for another 12h, and then quickly centrifuged at 7000g and -10°C for 10min to obtain the frozen supernatant and crystalline precipitate, respectively. The crystalline precipitate and supernatant were dried separately to obtain different ARs enrichments. Figure 3 As shown in Figure 2, after freezing and crystallizing at multiple temperature ranges (4°C, -80°C), the concentration of ARs in the crystal precipitate was 10 times that in the supernatant. Figure 4 ) It can be seen that compared with the liquid chromatography of the supernatant, after freezing and crystallization, the peaks of fatty acids and phenolic acids decreased (peaks before 6 min), and the peak height and area ratio of alkylresorcinol increased. This result shows that after freezing and crystallization, the content of fatty acids and phenolic acids in ARs enrichment decreased, and the proportion of ARs in the extract was reduced, achieving the purification of ARs.

[0059] Preparation of alkylresorcinol-starch complex:

[0060] This example provides a method for preparing an ARs-starch composite using the wheat bran middle layer as a raw material through subcritical fluid extraction of ARs, freezing crystallization sedimentation, and wet heat treatment. The implementation steps of the method are as follows:

[0061] Preparation of crude extract of ARs: Weigh about 100g of wheat bran middle layer and add it to 2L propane, spray 1% ethanol by volume of propane as entrainer, extract for 30 minutes at a temperature of 40°C and a pressure of 0.5Mpa, cycle the extraction 3 times, and then perform crude extraction of wheat bran ARs.

[0062] Preparation of frozen crystallization purification of wheat bran ARs: 10 g of subcritical propane crude extract of ARs was dissolved in 300 mL of methanol. Then, it was refrigerated at 4°C and -80°C for 8 h. After being taken out, it was quickly centrifuged at 7000g and -10°C for 10 min to obtain a frozen supernatant and a crystal precipitate, which was finally freeze-dried and refrigerated for later use.

[0063] Preparation of ARs-starch complex: Starch was heated in a water bath at 65°C for 60 min, then 2 mL of ARs ethanol solution (3%, starch dry basis) was added, and stirring in the water bath was continued for 60 min. After rapid cooling to room temperature, centrifugation was performed at 4000 rpm for 10 min, and the precipitate was washed with 50% ethanol aqueous solution, and finally freeze-dried to obtain a starch and ARs complex. Figure 5 is the infrared spectrum of ARs and its starch complex, such as Figure 5 As shown, the ARs-starch complex has a wavelength of 1400 and 1600 cm -1The absorption peaks of aromatic benzene ring are between them, and the peaks of phenol COH vibration and CH3 bending vibration of the tail of aliphatic chain are at 1150 and 720 cm -1 The two wave number peaks are characteristic peaks of the phenol ring and long chain alkyl of alkylresorcinol, which indicates that the alkylresorcinol and starch in the alkylresorcinol-starch composite prepared by the method are tightly combined.

[0064] The invention extracts alkylresorcinol (ARs) from wheat bran and prepares an ARs-starch complex. The method for separating and enriching an intermediate layer and ARs from wheat bran is green, simple and efficient, and can take into account both the purity and extraction rate of ARs. Meanwhile, the alkylresorcinol-starch complex prepared based on the extracted wheat bran ARs has slow digestion characteristics, anti-inflammatory functions and the like, and can realize the efficient extraction and food utilization of ARs in wheat bran.

[0065] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0066] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a wheat bran alkylresorcinol enrichment and a starch composite thereof, characterized in that: The following steps are involved: Step (1) dry mechanical dissociation: dry centrifugal impact pulverization of wheat bran is performed to achieve interlayer dissociation of the wheat bran aleurone layer, the outer pericarp and the middle layer to obtain a wheat bran structure layer powder; Step (2) dry physical enrichment: dry-enriching the wheat bran structure layer powder separated in step (1) by screening, airflow classification and a powder purifier to obtain classified wheat bran powder; Step (3) electrostatic field separation and purification: using the wheat bran powder after screening and airflow classification in step (2) as raw material, using dielectrophoresis to separate the aleurone layer and the non-aleurone layer, the non-aleurone layer being the middle layer and the outer pericarp, and then using triboelectric separation to separate the middle layer and the outer pericarp to obtain a high-purity middle layer powder; Step (4) subcritical propane extraction: the high-purity intermediate layer powder obtained in step (3) is subjected to low-temperature extraction using subcritical propane as an extraction solvent and ethanol as an entrainer, and finally desolventizing and evaporating to obtain a crude extract of alkylresorcinol; Step (5) multi-temperature crystallization purification: the crude alkylresorcinol extract obtained in step (4) is dissolved in a methanol solution, the methanol solution of the crude alkylresorcinol extract is subjected to multi-temperature freeze crystallization and then centrifuged to obtain a frozen supernatant and a crystalline precipitate, respectively, and after drying and desolventizing, a crystalline precipitate and a supernatant solute containing alkylresorcinol are obtained; Step (6) Preparation of alkylresorcinol-starch complex: Add wheat starch and heat it moderately to swell it, and mix it with the ethanol solution containing the crystalline precipitate of step (5), and then wash, centrifuge and freeze-dry to obtain the alkylresorcinol-starch complex.

2. The method for preparing the wheat bran alkylresorcinol enriched product and the starch composite thereof according to claim 1, characterized in that: In the step (1), the particle size of the wheat bran is greater than 500 μm, the water content is not higher than 10%, the linear speed of the dry centrifugal impact crushing is greater than 70 m / s, and the impact end radius is ≤0.5 mm.

3. The method for preparing the wheat bran alkylresorcinol enriched product and the starch composite thereof according to claim 1, characterized in that: In the step (2), the sieving aperture is 100-200 μm; and the suspension speed of the airflow classifier or the powder purifier is 0.5-0.8 m / s.

4. The method for preparing the wheat bran alkylresorcinol enriched product and the starch composite thereof according to claim 1, characterized in that: The step (3) uses dielectrophoresis to separate the non-paleurone layer from the aleurone layer, and the electric field strength is not less than 2 kv / cm. Preferably, the electric field strength is 2 to 5 kv / cm, and the movement speed of the powder under the electric field is 1 to 5 m / s.

5. The method for preparing the wheat bran alkylresorcinol enriched product and the starch composite thereof according to claim 1, characterized in that: After step (3), the intermediate layer and the outer peel powder are separated by friction electrostatic separation, the air flow velocity is 1-3 m / s, the friction pipe material is silica gel or polytetrafluoroethylene, the voltage of the electrostatic field used is 30-40 kV; the temperature of the electrostatic field separation is 20-30° C., the humidity is 30-40%; the moisture content of the wheat bran powder is not higher than 10%.

6. The method for preparing the wheat bran alkylresorcinol enriched product and the starch composite thereof according to claim 1, characterized in that: In the step (4), subcritical propane is combined with an ethanol entrainer to extract the alkylresorcinol in the wheat bran middle layer, the entrainer is added in an amount of 0.5% to 1%, the mass ratio of the extraction solvent volume to the wheat bran is in the range of 4:1 to 20:1; the extraction temperature is 25 to 40°C, the extraction time is 30 to 60 minutes, and the extraction cycle number is 3 to 5 times; preferably, the extraction temperature is 30 to 40°C, the extraction cycle is 3 times, and the single extraction time is 30 minutes.

7. The method for preparing the wheat bran alkylresorcinol enriched product and the starch composite thereof according to claim 1, characterized in that: In the step (5), the crystallization temperature is -80°C to 4°C, the crystallization time is 6 to 12 hours, and methanol solution is used as the freezing medium; preferably, the crystallization time is 6 to 8 hours at 4°C, and the centrifugal supernatant is further frozen in a -80°C low-temperature refrigerator for 12 hours, and then taken out and quickly centrifuged at 7000g and -10°C for 10 minutes.

8. The method for preparing the wheat bran alkylresorcinol enriched product and the starch composite thereof according to claim 1, characterized in that: In the step (6), the starch is heated in a water bath at a temperature of 60 to 70° C. for a heating time of 40 to 60 min; the amount of the ethanol extract of alkylresorcinol is 3% of the dry basis of the starch, and the water bath stirring time is 30 to 60 min; preferably, the starch and water are heated in a water bath at about 65° C. for 10 min, then the ethanol extract of alkylresorcinol accounting for 3% of the dry basis of the starch is added, the water bath stirring is continued for 60 min, the mixture is rapidly cooled to room temperature, centrifuged at 4000 rpm, and finally washed with a 50% ethanol solution to obtain the alkylresorcinol-starch complex.

9. A wheat bran alkylresorcinol enriched product and starch composite thereof, characterized in that: The product is prepared according to the method for preparing the wheat bran alkylresorcinol enriched product and its starch complex according to any one of claims 1 to 8.

10. An application of a wheat bran alkylresorcinol enrichment and a starch composite thereof, characterized in that: Application of the wheat bran alkylresorcinol enriched material and its starch complex prepared by the preparation method of the wheat bran alkylresorcinol enriched material and its starch complex according to any one of claims 1 to 8 in food processing.

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