Method for preparing food-grade particle emulsifier from rape seed cakes

Abstract

The invention relates to a method for preparing a food-grade particle emulsifier from rape seed cakes. The method comprises the following steps: (a) treating rapeseeds into rape seed cake powder; (b) dispersing the rape seed cake powder in a NaOH solution, centrifuging, taking precipitate, washing with water, dispersing in an HCl solution, carrying out high-temperature treatment, washing with water, and drying to obtain rape seed cake full-fiber particles; (c) carrying out micro-nano modification on the rape seed cake full-fiber particles by adopting a pure physical technology, and drying to obtain rape seed cake nano-particles; and (d) preparing the rape seed cake nano-particles into a rape seed cake nano-particle suspension with deionized water, mixing the rape seed cake nano-particle suspension with medium-chain fatty acid, and applying shear force to prepare the Pickering emulsion. According to the method, the compact structure of the rape seed cake can be destroyed, more hydrophilic parts in the rape seed cake can be exposed, and meanwhile, the size of the rape seed cake can be reduced to the micro-nano scale, so that the prepared rape seed cake all-fiber nanoparticle emulsion conforms to the characteristics of a Pickering emulsifier, and the problem that the utilization rate of the rape seed cake is low at present is solved.

Description

Technical Field

[0001] The invention relates to a method for preparing a food-grade particle emulsifier by utilizing rapeseed cake, and belongs to the field of food science. Background Art

[0002] Rapeseed cake is a byproduct of rapeseed oil extraction. It is rich in protein (35-40%) and dietary fiber (16-18%), and contains trace elements such as manganese, zinc, and copper. These characteristics make rapeseed cake extremely valuable in research and application. As one of the countries with the largest rapeseed planting area in the world, my country has rich rapeseed cake resources. In recent years, the annual output has averaged 5.0×10 9 However, rapeseed cake is currently mainly used as feed and fertilizer, and its rich protein and dietary fiber have not been fully utilized, resulting in a waste of resources. At the same time, my country's rapeseed oil industry is developing rapidly, and the industry urgently needs to find a new way to utilize rapeseed cake in a high-value manner.

[0003] Emulsion is a system formed by two or more incompatible liquids into a uniform system under the action of surfactants, i.e. emulsifiers. At present, emulsification technology is widely used in the fields of chemical industry, food, medicine, etc. In the food industry, emulsification technology is often used to prepare products such as cream, mayonnaise, and beverages. Usually, the emulsifiers that make up the emulsion are small molecule surfactants, proteins, glycerides, polysaccharides, etc. Although these emulsifiers can be adsorbed on the oil-water interface, due to the thin interfacial film, the oil droplets are prone to aggregation and Ostwald ripening, which belongs to the thermodynamic metastable state.

[0004] Solid particles with amphiphilicity can be adsorbed by oil and water at the same time, so they can also be stably anchored at the oil-water interface. Compared with traditional emulsifiers, this type of emulsifier has stronger stability because the particles need higher activation energy to desorb from the oil-water interface. At the same time, when the particle-type emulsifier (Pickering emulsifier) ​​is adsorbed at the oil-water interface, it will form a rigid interface film at the interface. The active substances embedded inside have longer storage stability due to the protection of the physical barrier. At the same time, because of the natural, green and non-toxic characteristics of Pickering emulsifiers, it has received more and more attention from the academic community and has been widely used in the food field. Therefore, if rapeseed cake can be converted into Pickering emulsifiers, it will provide a new way for the comprehensive utilization of rapeseed oil processing by-products.

[0005] As mentioned earlier, rapeseed cake is rich in protein and dietary fiber, but due to its compact structure, general physical and chemical methods are difficult to act on the inside of rapeseed cake, making it difficult to achieve micro-nano transformation of rapeseed cake. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a food-grade particle emulsifier using rapeseed cake, which can destroy the dense structure of rapeseed cake and expose more hydrophilic parts inside it, and can also reduce the size of rapeseed cake to micro-nano scale. The rapeseed cake full-fiber nanoparticle emulsion prepared by the method meets the characteristics that a Pickering emulsifier should have, and solves the problem of low utilization rate of rapeseed cake at present.

[0007] The technical solution to the above technical problem is: a method for preparing a food-grade granular emulsifier using rapeseed cake, comprising the following steps: (a) grinding rapeseed cake into powder, soaking it in deionized water and washing it for 3 to 5 times, drying it, further crushing it, and passing it through a 100-300 mesh sieve to obtain rapeseed cake powder; (b) dispersing rapeseed cake powder in a NaOH solution with a pH value of 10 to 15, stirring at 50 to 80° C. for 60 to 120 min to dissolve the protein, then centrifuging at a speed of 5000 to 8000 rpm for 8 to 20 min, washing the precipitate with deionized water, dispersing it in a HCl solution with a pH value of 0.5 to 1.5, stirring at 75 to 85° C. for 3.5 to 4.5 h to soften the rapeseed cake fiber structure, then treating at 100 to 120° C. for 2 to 4 h, repeatedly rinsing with deionized water, and drying to obtain rapeseed cake full fiber particles; (c) using pure physical technology to perform micro-nano transformation on rapeseed cake full fiber particles, and freeze-drying to obtain rapeseed cake nanoparticles; (d) The rapeseed cake nanoparticles are prepared into a rapeseed cake nanoparticle suspension with deionized water, the rapeseed cake nanoparticle suspension is mixed with medium-chain fatty acids, and a rapeseed cake full-fiber nanoparticle Pickering emulsion is prepared by applying shear force.

[0008] Furthermore, the specific operation of step (c) using pure physical technology to perform micro-nano transformation on the rapeseed cake full fiber particles is: (1) Disperse the rapeseed cake fiber particles in 5 mM pH = 7.0 phosphate buffer, prepare a phosphate suspension of rapeseed cake fiber particles with a mass fraction of 2-4%, stir at room temperature for 2-6 hours, and hydrate at 3-5°C overnight; (2) The hydrated particles were sheared at 10,000 to 20,000 rpm using a high-speed shearing machine, and then the particles were placed in a cell disruptor and processed at a power of 400 to 1,000 W for 15 to 60 min, and dried overnight to obtain rapeseed cake full-fiber nanoparticles.

[0009] Furthermore, the specific operation of step (c) using pure physical technology to perform micro-nano transformation on the rapeseed cake full fiber particles is: (1) Disperse the rapeseed cake fiber particles in 5 mM pH = 7.0 phosphate buffer, prepare a phosphate suspension of rapeseed cake fiber particles with a mass fraction of 2-4%, stir at room temperature for 2-6 hours, and hydrate at 3-5°C overnight; (2) The rapeseed cake was treated with a microfluidizer at 10,000 to 30,000 psi for 3 to 5 cycles and then dried overnight to obtain rapeseed cake full-fiber nanoparticles.

[0010] Furthermore, the specific operation of step (d) is: preparing a rapeseed cake nanoparticle suspension with a mass fraction of 1 to 4% with deionized water, mixing the rapeseed cake nanoparticle suspension with medium-chain fatty acids at an oil-water ratio of 0.25 to 4, and then homogenizing the mixed system to obtain a rapeseed cake full-fiber nanoparticle Pickering emulsion.

[0011] Furthermore, the homogenizing equipment used in step (d) is a handheld homogenizer, and the homogenizing condition is 5000-10000 rpm.

[0012] Furthermore, the homogenizing equipment used in step (d) is a high-pressure microfluidizer, the homogenizing condition is 5000-20000 psi, and the number of treatments is 2-5 times.

[0013] Furthermore, the homogenizing equipment used in step (d) is an ultrasonic cell disruptor, and the homogenizing conditions are ultrasonic power of 300-600 W, processing time of 2-10 min, and step frequency of on 3s / off 3s.

[0014] The characteristics of the preparation method of the present invention are as follows: (1) Pre-treatment of rapeseed cake with alkali solution can precipitate alkali-soluble substances such as lignin and protein in rapeseed cake, and create pores on the surface of rapeseed cake, which is convenient for chemical reagents to contact with the internal structure. Then, acid treatment is used to make the interior of rapeseed cake swell and become looser, which is convenient for subsequent physical treatment.

[0015] (2) The core of ultrasonic cavitation technology is to induce cavitation effect through the energy of ultrasonic waves. Its frequency is 20 kHz to 100 kHz. This feature makes it have wide application potential in many fields. When ultrasonic waves propagate into liquids, high-intensity pressure waves will be generated in the liquid. When the wave pressure reaches a certain level, local areas in the liquid will produce instantaneous high temperature and high pressure, causing the liquid to vaporize instantly to form bubbles. Cavitation bubbles will expand and contract rapidly under the action of ultrasonic waves, generating strong liquid shear force and impact force, which can effectively destroy the structure of the material and achieve a variety of processing effects such as mixing, dispersion, emulsification, dissolution, and cleaning.

[0016] (3) The working principle of high-pressure homogenization is to use high pressure to make the material be subjected to high-intensity shear, high-energy collision, cavitation effect and other comprehensive forces when passing through narrow gaps, so as to process the material from larger granular objects into stable emulsions or suspensions with fine particles. Usually, the homogenization pressure can reach up to 200 MPa, which is suitable for the crushing of microbial cells. Micro-jet high-pressure homogenization is essentially a special form of ultra-high-pressure homogenization. Its working principle is similar to that of high-pressure homogenization. The material is subjected to strong shear, high-speed impact, cavitation explosion, instantaneous pressure release and other dynamic effects in a very small space, which reduces the particle size of the material and can obtain micron-level or even nano-level material particles.

[0017] The beneficial effects of the present invention are: using ultrasonic cavitation (UCA) and high pressure microjet (HPM) technology to micro-nano-transform rapeseed cake, soft particles with a size of 300-400 nm are prepared, the particles have extremely strong suspension stability, and can be made into a food-grade Pickering emulsifier with good prospects. The present invention provides a new way to high-value utilization of rapeseed cake, and solves the problem of waste caused by the protein and dietary fiber of rapeseed cake not being deeply utilized.

[0018] The technical features of a method for preparing a food-grade granular emulsifier using rapeseed cake according to the present invention will be further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Figure 2 is a schematic diagram of the ζ-potential of the rapeseed cake particle dispersion before and after alkali solution pretreatment. Figure 1 As shown in the figure, the surface charge of the particles changed dramatically after alkali treatment, decreasing from 0 to -40 mv. At this time, the particles have higher stability due to the stronger electrostatic repulsion.

[0020] Figure 2 Schematic diagram of the average three-phase contact angle (θ / °) of rapeseed cake fiber particles before and after alkali solution pretreatment; (a) is the average three-phase contact angle of rapeseed cake particles before any treatment, and (b) is the average three-phase contact angle of rapeseed cake fiber particles before and after alkali solution pretreatment. Figure 2 As shown, after alkali treatment, the contact angle of the particles approaches 90°. At this time, the particles can be wetted by both oil and water phases at the same time and can be stably distributed at the oil-water interface.

[0021] Figure 3Schematic diagram of the microstructure of rapeseed cake dispersion (pH=7.0, 1.0wt%); (a) is the rapeseed cake particles after mechanical crushing; (b) is the rapeseed cake particles after alkali treatment; (c, d, e) are the rapeseed cake particles treated with different ultrasonic times (15min, 30min, 60min); (f, g, h) are the rapeseed cake particles treated with different microjet pressures (10000 psi, 20000psi, 30000psi).

[0022] Figure 4 Schematic diagram of the suspension stability of rapeseed cake dispersion (pH=7.0, 1.0 wt%) after alkali solution pretreatment and ultrasonic treatment for different time (0, 15 min, 30 min, 60 min); (a, b, c, d, e, f) are the initial appearance of the rapeseed cake dispersion after ultrasonic treatment for different time (0, 15, 30, 60 min from left to right), the appearance after 5 minutes, the appearance after 15 minutes, the appearance after 2 days, the appearance after 4 days, and the appearance after 7 days, respectively; (g) is the suspension stability curve of the rapeseed cake dispersion after ultrasonic treatment for different time.

[0023] Figure 5 Schematic diagram of the suspension stability of rapeseed cake dispersion (pH=7.0, 1.0 wt%) after alkali solution pretreatment and treatment with different microjet pressures (0, 10000 psi, 20000 psi, 30000 psi); (a, b, c, d, e, f) are the initial appearance, appearance after 5 minutes, appearance after 15 minutes, appearance after 2 days, appearance after 4 days, and appearance after 7 days of treatment of the rapeseed cake dispersion after treatment with different microjet pressures (from left to right: 0, 10000 psi, 20000 psi, 30000 psi), respectively; (g) is the suspension stability curve of the rapeseed cake dispersion after treatment with different microjet pressures (in the figure, the curve of the microjet pressure of 20000 psi coincides with the curve of the microjet pressure of 30000 psi).

[0024] Figure 6 Microstructure and appearance images of high internal phase Pickering emulsions with an oil-water ratio of 3 constructed from rapeseed cake particles of different concentrations prepared by ultrasonic cavitation for 30 minutes; (a, b, c, d) are microstructure images of high internal phase Pickering emulsions with a mass fraction of rapeseed cake nanoparticle suspension of 1%, 2%, 3%, and 4%, respectively; (e) is the appearance image of high internal phase Pickering emulsions with a mass fraction of rapeseed cake nanoparticle suspension of 1%, 2%, 3%, and 4%, respectively.

[0025] Figure 7Particle size distribution curves of high internal phase Pickering emulsions with an oil-water ratio of 3 constructed from rapeseed cake particles of different concentrations prepared by ultrasonic cavitation for 60 minutes.

[0026] Figure 8 Microstructure and appearance of high internal phase Pickering emulsions with an oil-water ratio of 3 constructed from rapeseed cake particles of different concentrations prepared by 20,000 psi high-pressure microjetting; (a, b, c, d) are microstructures of high internal phase Pickering emulsions with a mass fraction of rapeseed cake nanoparticle suspension of 1%, 2%, 3%, and 4%, respectively; (e) is the appearance of high internal phase Pickering emulsions with a mass fraction of rapeseed cake nanoparticle suspension of 1%, 2%, 3%, and 4%, respectively.

[0027] Fig. 9 Particle size distribution curves of high internal phase Pickering emulsions with an oil-water ratio of 3 constructed from rapeseed cake particles of different concentrations prepared by 20,000 psi high-pressure microfluidization. DETAILED DESCRIPTION Example 1

[0028] A method for preparing a food-grade granular emulsifier using rapeseed cake comprises the following steps: (a) The rapeseed cake was ground into powder and then soaked in deionized water for five times to remove metal ions and free organic acids in the rapeseed cake raw material. After drying, the rapeseed cake was further crushed by a crusher and passed through a 100-mesh sieve to obtain rapeseed cake powder. The sieved powder was collected and stored at -18°C for later use.

[0029] (b) A certain amount of rapeseed cake powder was dispersed in a NaOH solution with a pH value of 12, stirred at 80 °C for 120 min to dissolve its protein, and then centrifuged at 8000 rpm for 10 min. The precipitate was washed with deionized water, dispersed in a HCl solution with a pH value of 1, stirred at 80 °C for 4 h to soften the rapeseed cake fiber structure, and then treated in an autoclave at 120 °C for 4 h, repeatedly rinsed with deionized water, and dried to obtain rapeseed cake full-fiber particles.

[0030] (c) The rapeseed cake fiber particles were dispersed in phosphate buffer (5 mM, pH = 7.0), and a phosphate suspension of rapeseed cake fiber particles with a mass fraction of 4% was accurately prepared, stirred at room temperature for 4 hours, and hydrated overnight at 4 ° C. The dispersion was sheared at high speed (15000 rpm) using a handheld high-speed shearing machine to further hydrate the particles. The fully hydrated particles were placed in a cell disruptor at a power of 600 W for 30 min, and then dried overnight in a freeze dryer to obtain rapeseed cake fiber nanoparticles.

[0031] (d) A 4% rapeseed cake nanoparticle suspension was prepared with deionized water. The rapeseed cake nanoparticle suspension was mixed with medium-chain fatty acids (MCT) at an oil-water ratio of 3 and homogenized using a handheld homogenizer shear (6000 rpm). Finally, a Pickering high internal phase emulsion constructed with rapeseed cake nanoparticles was obtained.

[0032] The microscopic morphology and appearance of the Pickering high internal phase emulsion constructed by the rapeseed cake nanoparticles prepared in Example 1 are shown in FIG. Figure 6 (d) and Figure 6 As shown in (e), it can be seen from the figure that the emulsion prepared in Example 1 meets the characteristics that a Pickering emulsifier should have. Example 2

[0033] A method for preparing a food-grade granular emulsifier using rapeseed cake comprises the following steps: (a) The rapeseed cake was ground into powder and then soaked in deionized water for four times to remove metal ions and free organic acids in the rapeseed cake raw material. After drying, the rapeseed cake was further crushed by a crusher and passed through a 200-mesh sieve to obtain rapeseed cake powder. The sieved powder was collected and stored at -18°C for later use.

[0034] (b) A certain amount of rapeseed cake powder was dispersed in a NaOH solution with a pH value of 11, stirred at 70 °C for 70 min to dissolve the protein, and then centrifuged at 6000 rpm for 15 min. The precipitate was washed with deionized water, dispersed in a HCl solution with a pH value of 1, stirred at 80 °C for 4 h to soften the rapeseed cake fiber structure, and then treated in an autoclave at 120 °C for 4 h, repeatedly rinsed with deionized water, and dried to obtain rapeseed cake full-fiber particles.

[0035] (c) The rapeseed cake fiber particles were dispersed in phosphate buffer (5 mM, pH=7.0), and a phosphate suspension of rapeseed cake fiber particles with a mass fraction of 4% was accurately prepared, stirred at room temperature for 3 hours, and hydrated overnight at 4°C. The mixture was processed four times using a microfluidizer with a homogenization pressure of 20,000 psi, and dried overnight using a freeze dryer to obtain rapeseed cake fiber nanoparticles.

[0036] (d) A 4% rapeseed cake nanoparticle suspension was prepared with deionized water. The rapeseed cake nanoparticle suspension was mixed with medium-chain fatty acids (MCT) at an oil-water ratio of 3, and homogenized three times using a high-pressure microfluidizer at 5000 psi to finally obtain a Pickering high internal phase emulsion constructed with rapeseed cake nanoparticles.

[0037] The microscopic morphology and appearance of the Pickering high internal phase emulsion constructed by the rapeseed cake nanoparticles prepared in Example 2 are shown in FIG. Figure 8 (d) and Figure 8 As shown in (e), it can be seen from the figure that the emulsion prepared in Example 2 meets the characteristics that a Pickering emulsifier should have. Example 3

[0038] A method for preparing a food-grade granular emulsifier using rapeseed cake comprises the following steps: (a) The rapeseed cake was ground into powder and then soaked in deionized water for washing three times to remove metal ions and free organic acids in the rapeseed cake raw material. After drying, the rapeseed cake was further crushed by a crusher and passed through a 300-mesh sieve to obtain rapeseed cake powder. The sieved powder was collected and stored at -18°C for later use.

[0039] (b) A certain amount of rapeseed cake powder was dispersed in a NaOH solution with a pH value of 14, stirred at 60 °C for 100 min to dissolve the protein, and then centrifuged at 7000 rpm for 10 min. The precipitate was washed with deionized water, dispersed in a HCl solution with a pH value of 1, stirred at 80 °C for 4 h to soften the rapeseed cake fiber structure, and then treated in an autoclave at 110 °C for 4 h, repeatedly rinsed with deionized water, and dried to obtain rapeseed cake full-fiber particles.

[0040] (c) The rapeseed cake fiber particles were dispersed in phosphate buffer (5 mM, pH=7.0), and a phosphate suspension of rapeseed cake fiber particles with a mass fraction of 3% was accurately prepared, stirred at room temperature for 5 hours, and hydrated overnight at 4°C. The dispersion was sheared at high speed (18,000 rpm) using a handheld high-speed shearing machine to further hydrate the particles. The fully hydrated particles were placed in a cell disruptor at a power of 800 w for 40 min, and then dried overnight in a freeze dryer to obtain rapeseed cake fiber nanoparticles.

[0041] (d) A 3% rapeseed cake nanoparticle suspension was prepared with deionized water. The rapeseed cake nanoparticle suspension was mixed with medium-chain fatty acids (MCT) at an oil-water ratio of 4 and homogenized using an ultrasonic cell disruptor. The homogenization conditions were as follows: ultrasonic power 300 W, processing time 2 min, and step frequency on 3 s / off 3 s. Finally, a Pickering high internal phase emulsion constructed with rapeseed cake nanoparticles was obtained. Experiments have shown that the emulsion meets the characteristics that a Pickering emulsifier should have.

Claims

1. A method for preparing a food-grade granular emulsifier using rapeseed cake, Features: The following steps are involved: (a) grinding rapeseed cake into powder, soaking it in deionized water and washing it for 3 to 5 times, drying it, further crushing it, and passing it through a 100-300 mesh sieve to obtain rapeseed cake powder; (b) dispersing rapeseed cake powder in a NaOH solution with a pH value of 10 to 15, stirring at 50 to 80° C. for 60 to 120 min to dissolve the protein, then centrifuging at a speed of 5000 to 8000 rpm for 8 to 20 min, washing the precipitate with deionized water, dispersing it in a HCl solution with a pH value of 0.5 to 1.5, stirring at 75 to 85° C. for 3.5 to 4.5 h to soften the rapeseed cake fiber structure, then treating at 100 to 120° C. for 2 to 4 h, repeatedly rinsing with deionized water, and drying to obtain rapeseed cake full fiber particles; (c) using pure physical technology to perform micro-nano transformation on rapeseed cake full fiber particles, and freeze-drying to obtain rapeseed cake nanoparticles; (d) The rapeseed cake nanoparticles are prepared into a rapeseed cake nanoparticle suspension with deionized water, the rapeseed cake nanoparticle suspension is mixed with medium-chain fatty acids, and a rapeseed cake full-fiber nanoparticle Pickering emulsion is prepared by applying shear force.

2. A method for preparing a food-grade granular emulsifier using rapeseed cake according to claim 1, Features: The specific operation of step (c) using pure physical technology to carry out micro-nano transformation of rapeseed cake full fiber particles is: (1) Disperse the rapeseed cake fiber particles in 5 mM pH = 7.0 phosphate buffer, prepare a phosphate suspension of rapeseed cake fiber particles with a mass fraction of 2-4%, stir at room temperature for 2-6 hours, and hydrate at 3-5°C overnight; (2) The hydrated particles were sheared at 10,000 to 20,000 rpm using a high-speed shearing machine, and then the particles were placed in a cell disruptor and processed at a power of 400 to 1,000 W for 15 to 60 min, and dried overnight to obtain rapeseed cake full-fiber nanoparticles.

3. The method for preparing a food-grade granular emulsifier using rapeseed cake according to claim 1, Features: The specific operation of step (c) using pure physical technology to carry out micro-nano transformation of rapeseed cake full fiber particles is: (1) Disperse the rapeseed cake fiber particles in 5 mM pH = 7.0 phosphate buffer, prepare a phosphate suspension of rapeseed cake fiber particles with a mass fraction of 2-4%, stir at room temperature for 2-6 hours, and hydrate at 3-5°C overnight; (2) The rapeseed cake was treated with a microfluidizer at 10,000 to 30,000 psi for 3 to 5 cycles and then dried overnight to obtain rapeseed cake full-fiber nanoparticles.

4. A method for preparing a food-grade granular emulsifier using rapeseed cake according to any one of claims 1 to 3, Features: The specific operation of step (d) is: preparing a rapeseed cake nanoparticle suspension with a mass fraction of 1 to 4% with deionized water, mixing the rapeseed cake nanoparticle suspension with medium-chain fatty acids at an oil-water ratio of 0.25 to 4, and then homogenizing the mixed system to obtain a rapeseed cake full-fiber nanoparticle Pickering emulsion.

5. A method for preparing a food-grade granular emulsifier using rapeseed cake according to claim 4, Features: The homogenizing equipment used in step (d) is a handheld homogenizer, and the homogenizing condition is 5000-10000 rpm.

6. A method for preparing a food-grade granular emulsifier using rapeseed cake according to claim 4, Features: The homogenizing equipment used in step (d) is a high-pressure microfluidizer, the homogenizing condition is 5000-20000 psi, and the number of treatments is 2-5 times.

7. The method for preparing a food-grade granular emulsifier using rapeseed cake according to claim 4, Features: The homogenizing equipment used in step (d) is an ultrasonic cell disruptor, and the homogenizing conditions are as follows: ultrasonic power of 300-600 W, processing time of 2-10 min, and step frequency of 3 s on / 3 s off.

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