Preparation method of high-solubility macadamia nut protein

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a preparation method of high-solubility macadamia nut protein. The method comprises the following steps: uniformly mixing Australian hardness degreased powder with water, and adding composite alkali powder to enable the pH value to be 10.5-11 so as to obtain a mixed material liquid; then, carrying out high-energy medium grinding treatment on the obtained mixed material liquid, and adding citric acid to enable the pH to be 6.8-7.0, so as to obtain a protein solution; and finally, carrying out spray drying on the protein solution to obtain the macadamia nut protein. According to the method disclosed by the invention, large insoluble protein aggregates are dissociated into relatively small water-dispersed protein aggregates by combining acid-base activation with a high-energy medium grinding system, so that the macadamia nut protein is better dissolved, and the problems of poor dispersibility and functional properties of the macadamia nut protein are solved. In addition, the method is green and simple in treatment process, high in treatment efficiency, capable of meeting industrial production standards and capable of achieving continuous production.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and particularly relates to a method for preparing highly soluble macadamia nut protein. Background Art

[0002] In recent years, people's consumption trend for functional foods that maintain human health has increased year by year. Compared with scarce and expensive animal proteins, low-priced, low-allergenic and nutritious plant proteins have been regarded as a major food protein resource. With the development and prosperity of macadamia nut planting industry in my country, macadamia oil is about to become an important product type. The macadamia nut meal after oil extraction contains about 30% protein. Amino acid analysis shows that macadamia nut meal is rich in essential amino acids and nutritionally balanced, making it an excellent plant resource for protein extraction. The amino acid composition of macadamia protein is balanced and nutritious. It can meet the adult standards recommended by FAO / WHO / UNO. The valine and isoleucine content is close to the recommended standards for children, and can be added to infant food as a nutritional supplement. Macadamia nut protein is nutritious and has the potential to be used in the food industry.

[0003] In actual production, the performance of macadamia protein is generally difficult to meet the actual needs of the production process of enterprises. Low solubility is the key technical difficulty of the industrialization and productization of macadamia protein. Since it cannot be evenly dispersed in water, macadamia protein cannot be further applied to food product systems such as emulsions, colloids, foams, etc., which seriously limits its scope of application and constrains the marketization process of macadamia protein. At present, the main methods of macadamia protein modification are enzymatic modification, chemical modification and physical modification. Enzymatic modification has a good effect, but the protein will be hydrolyzed into peptides and small molecule amino acids, which cannot fully retain the original nutritional properties of the protein and will produce bitter peptides; chemical modification such as glycosylation modification, acylation modification and phosphorylation modification can effectively improve the solubility of protein, but the reaction of the modification process is difficult to control, which may cause food safety problems; physical modification can completely retain the primary structure of the protein without the need for additional chemical reagents, but the modification effect is limited and the processing capacity cannot match the requirements of industrial production. Therefore, developing a simple, efficient, green, safe and industrializable macadamia protein modification technology is of great significance for expanding the macadamia protein market and breaking through the bottleneck of macadamia protein development. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art. The present invention provides a method for preparing high-concentration and high-solubility macadamia nut protein. The method dissociates large insoluble protein aggregates into smaller water-dispersible protein aggregates through acid-base activation combined with a high-energy medium mill system, thereby achieving the extraction of macadamia nut protein and solving the problem of poor dispersibility and functional properties of macadamia nut protein. Specifically,

[0005] The present invention provides a method for preparing highly soluble macadamia nut protein, which adopts the following technical scheme:

[0006] A method for preparing highly soluble macadamia nut protein comprises the following steps:

[0007] S1: The shelled macadamia kernels were crushed by a colloid mill for 30 seconds to obtain defatted macadamia powder;

[0008] S2: the defatted macadamia powder obtained in step S1 is mixed evenly with water and subjected to high-energy medium grinding, and then compound alkali powder is added and stirred to adjust the pH to 10.5-11, and then citric acid is added to adjust the pH to 6.8-7.0 to obtain a protein solution;

[0009] S3: spray-drying the protein solution obtained in step S2 to finally obtain macadamia nut protein.

[0010] The composite alkali powder is sodium hydroxide and calcium hydroxide.

[0011] Among them, in the above preparation process, the pH of the solution is adjusted to 10.5-11 by using composite alkali powder. This is because when the pH is too low, the protein cannot be fully unfolded and the modification effect will be greatly weakened. If the pH is too high, the protein will be easily hydrolyzed into peptides, thereby destroying the nutritional integrity of the protein and causing unpleasant flavors. In addition, too much alkali will also increase the final salt content of the product. Then citric acid is added to adjust the pH to 6.8-7.0. This is because maintaining the pH of the protein solution at a neutral level is beneficial to maintaining the stability of the properties of the composite macadamia protein. Acidic conditions will cause the protein to precipitate again, and alkaline conditions will limit the application scenarios of the protein.

[0012] The present invention adopts a method combining chemical modification and physical modification, takes shelled macadamia kernels as raw materials, and prepares a high-concentration, high-performance macadamia protein through a process of pre-crushing, mixing, alkali activation, high-energy medium milling, spray drying and the like. The present invention mainly adopts a colloid mill to pre-crush the shelled macadamia kernels, and then uses a high-energy medium mill to grind the mixed macadamia defatted powder, and adds a compound alkali powder to adjust the solution environment to unfold the protein structure. Among them, the conformational changes of macadamia protein are regulated by acid-base activation combined with a high-energy medium mill system, and large insoluble protein aggregates are dissociated into smaller water-dispersible protein aggregates, and then the pH is adjusted to restore to neutral to induce protein reorganization, and finally spray drying is performed to obtain macadamia protein.

[0013] As a further preferred embodiment, the above-mentioned step S1 further includes the following pretreatment step: using a colloid mill to grind the macadamia nut kernels to 400 meshes, the pre-crushing can effectively improve the working efficiency of the high-energy medium mill, and make the protein dissolve faster in the alkali solution; the frequency of the high-energy medium mill is 50Hz-60Hz, the rotation speed is 1000-1200rpm, the diameter of the grinding beads (zirconia) is 0.6-1.2mm, and the milling cavity bead filling degree is 70-80%.

[0014] As a further preferred embodiment, in the present invention, the mass ratio of sodium hydroxide to calcium hydroxide is 1: 1. The present invention adopts compound alkali powder sodium hydroxide and calcium hydroxide to effectively reduce the sodium ion content of the protein powder product in the prior art, and the effect is better when the mass ratio of sodium hydroxide to calcium hydroxide is 1: 1.

[0015] As a further preferred embodiment, the temperature of water in step S1 is 50°C-55°C; the ratio of macadamia defatted powder to water is 0.6-1:19-19.8. Higher water temperature is conducive to the rapid dispersion of macadamia defatted powder in water and improves the activity of protein molecules in the solution, but when the temperature is higher than 60°C, the protein is prone to denaturation. At the same time, since the treatment of the high-energy medium mill will cause a certain temperature rise in the protein solution, the optimal temperature of the water is 50°C-55°C. In addition, a low ratio of water to defatted powder will result in too low production efficiency, and a high ratio will affect the treatment effect.

[0016] As a further preferred embodiment, in step S2, the frequency of the high energy medium mill is 50 Hz-60 Hz, the rotation speed is 1000-1200 rpm, the diameter of the grinding beads (zirconia) is 0.6-1.2 mm, and the filling degree of the milling cavity beads is 70-80%.

[0017] As a further preferred embodiment, the particle size of the macadamia nut protein in the protein solution obtained in step S2 is controlled to be 10 μm-25 μm. Under this particle size, the binding efficiency of the protein in the solution system can be significantly improved, and the solubility of the protein can be significantly improved.

[0018] As a further preferred embodiment, the spray drying in step S3 adopts a spray drying tower atomizer, and the specific process parameters are as follows: frequency is 45Hz-50Hz, inlet air temperature is 160℃-180℃, and outlet air temperature is 75℃-85℃. Spray drying has high processing efficiency and large processing capacity, and is suitable for industrialization. The effect is better when the inlet air temperature and outlet air temperature are within the above range. If the temperature is too high, the protein is easy to denature and aggregate during the drying process, and if the temperature is too low, the production efficiency cannot be guaranteed.

[0019] The present invention also provides a highly soluble macadamia nut protein prepared by the above-mentioned preparation method. The macadamia nut protein prepared by the present invention has a solubility of ≥93%, an emulsification property improved by about 220%, a foaming property improved by 420%, and greatly improved functional properties, which greatly expands its application scenarios.

[0020] The invention also discloses the application of the nut protein prepared by the method of the invention in the preparation of medicines, foods and health foods.

[0021] The wet physical modification equipment used in this method, the high-energy medium mill, has the characteristics of large processing capacity, good physical modification effect and continuous production. It consists of three parts: a cooling system; a milling system (milling chamber); and a circulation system. Milling using this technology occurs in a milling chamber, which contains a stirring shaft and is filled with more than 70% of milling medium. The high-speed rotation of the shaft causes the milling medium to move at high speed, which produces many stress events per unit time and unit volume, thereby reducing the particle size and improving the solubility of macadamia protein. The particle size of the material after crushing is ≤25μm, and the processing capacity is ≥1t / h, which is conducive to the industrial application of macadamia protein modification. The emulsification and foaming properties of the processed macadamia protein are improved.

[0022] The beneficial effects of the present invention are:

[0023] The macadamia protein prepared by the present invention has a solubility of ≥93%, an emulsification property improved by about 220%, a foaming property improved by about 420%, and excellent physical and chemical properties. The processing concentration of the method is ≥5%, and the processing capacity is >1t / h. The process framework of alkali activation combined with high-energy medium grinding to process macadamia protein solves the problem of poor solubility and functional properties of macadamia protein, effectively broadens the development scope and ideas of macadamia protein products, and meets the requirements of industrial production.

[0024] The method proposed by the invention has a green and simple treatment process, high treatment efficiency, meets industrial production standards, and can be produced continuously. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 , comparison of solubility of macadamia nut protein.

[0026] Figure 2 , comparison of the foaming properties of macadamia nut protein, where the left picture shows macadamia nuts that have not been treated with high-energy media milling, and the right picture shows macadamia nuts that have been treated with high-energy media milling. DETAILED DESCRIPTION

[0027] The following will be combined with various embodiments to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0028] Example 1

[0029] A method for preparing highly soluble macadamia nut protein, comprising the following steps:

[0030] (1) Pre-crushing: The shelled macadamia kernels were crushed with a colloid mill for 30 seconds to obtain defatted macadamia powder, which was pre-crushed to 400 mesh;

[0031] (2) Mixing: 0.5 t of defatted macadamia nut powder from step (1) and 9.5 t of hot water at 55° C. are added into a heat-insulating stirring tank and uniformly mixed to obtain a mixed liquid with a concentration of 5% (w / w);

[0032] (3) alkali activation: adding compound alkali powder to the mixed solution of step (2), wherein the compound alkali powder is prepared by mixing food-grade sodium hydroxide and calcium hydroxide in a ratio of 1:1 (w / w), so that the pH of the protein solution is maintained at 11;

[0033] (4) High-energy media milling: The macadamia protein obtained in step (3) was subjected to physical modification using a high-energy media mill with a frequency of 58 Hz, a rotation speed of 1200 rpm, a bead (zirconia) diameter of 0.6 mm, and a milling cavity bead filling degree of 80%;

[0034] (5) Protein reconstitution: Select the macadamia protein solution modified in step (4), add food-grade citric acid to adjust the pH to 7.0, and induce protein reconstitution. The resulting material has a particle size of 10 μm.

[0035] (6) The macadamia protein neutralized in step (5) was spray-dried, the spray tower atomizer motor frequency was 45 Hz, the air inlet temperature was 180° C., and the air outlet temperature was 85° C., to obtain 0.14 t of macadamia protein with a solubility of 96%

[0036] Example 2

[0037] A method for preparing highly soluble macadamia nut protein, comprising the following steps:

[0038] (1) Pre-crushing: The shelled macadamia kernels were crushed using a colloid mill for 29 ± 1 s to obtain defatted macadamia powder, which was pre-crushed to 400 mesh;

[0039] (2) Mixing: 0.7 t of defatted macadamia nut powder from step (1) and 9.3 t of hot water at 55° C. are added into a heat-insulating stirring tank and uniformly mixed to obtain a mixed liquid with a concentration of 7% (w / w);

[0040] (3) alkali activation: adding compound alkali powder to the mixed solution of step (2), wherein the compound alkali powder is prepared by mixing food-grade sodium hydroxide and calcium hydroxide in a ratio of 1:1 (w / w), so that the pH of the protein solution is maintained at 11;

[0041] (4) High-energy media milling: The macadamia protein obtained in step (3) was subjected to physical modification using a high-energy media mill with a frequency of 55 Hz, a rotation speed of 1100 rpm, a bead (zirconia) diameter of 1.0 mm, and a milling cavity bead filling degree of 75%;

[0042] (5) Protein reconstitution: Select the macadamia protein solution modified in step (4), add food-grade citric acid to adjust the pH to 7.0, and induce protein reconstitution to obtain a material particle size of 16 μm;

[0043] (6) The macadamia nut protein neutralized in step (5) was spray-dried, the spray tower atomizer motor frequency was 47 Hz, the air inlet temperature was 175° C., and the air outlet temperature was 80° C., to obtain 0.18 t of macadamia nut protein with a solubility of 94%.

[0044] Example 3

[0045] A method for preparing highly soluble macadamia nut protein, comprising the following steps:

[0046] (1) Pre-crushing: The shelled macadamia kernels were crushed using a colloid mill for 31 ± 1 s to obtain defatted macadamia powder, which was pre-crushed to 400 mesh;

[0047] ((2) Mixing: 1.0 t of defatted macadamia nut powder from step (1) and 9.0 t of hot water at 55° C. are added into a heat-insulating stirring tank and uniformly mixed to obtain a mixed liquid with a concentration of 10% (w / w);

[0048] (3) alkali activation: adding compound alkali powder to the mixed solution of step (2), wherein the compound alkali powder is prepared by mixing food-grade sodium hydroxide and calcium hydroxide in a ratio of 1:1 (w / w), so that the pH of the protein solution is maintained at 10.5;

[0049] (4) High-energy media milling: The macadamia protein obtained in step (3) was subjected to physical modification using a high-energy media mill with a frequency of 53 Hz, a rotation speed of 1000 rpm, a bead (zirconia) diameter of 1.2 mm, and a milling cavity bead filling degree of 70%;

[0050] (5) Protein reconstitution: Select the macadamia protein solution modified in step (4), add food-grade citric acid to adjust the pH to 7.0, and induce protein reconstitution to obtain a material particle size of 25 μm;

[0051] (6) The macadamia nut protein neutralized in step (5) was spray-dried, with the spray tower atomizer motor frequency of 49 Hz, the air inlet temperature of 170° C., and the air outlet temperature of 75° C. to obtain 0.26 t of macadamia nut protein with a solubility of 93%.

[0052] Comparative Example 1:

[0053] A method for preparing highly soluble macadamia nut protein, comprising the following steps:

[0054] (1) Pre-crushing: The shelled macadamia kernels were crushed using a colloid mill for 33 ± 1 s to obtain defatted macadamia powder, which was pre-crushed to 400 mesh;

[0055] (2) Mixing: 0.3 t of defatted macadamia nut powder from step (1) and 2.7 t of hot water at 50° C. are added into a heat-insulating stirring tank and uniformly mixed to obtain a mixed liquid with a concentration of 10% (w / w);

[0056] (3) alkali activation: adding compound alkali powder to the mixed solution of step (2), wherein the compound alkali powder is prepared by mixing food-grade sodium hydroxide and calcium hydroxide in a ratio of 1:1 (w / w), so that the pH of the protein solution is maintained at 10.5;

[0057] (4) Protein reconstitution: select the macadamia protein solution from step (3), add food-grade citric acid to adjust the pH to 7, and induce protein reconstitution to obtain a material particle size of 65 μm;

[0058] (5) The macadamia nut protein neutralized in step (4) was spray-dried, the spray tower atomizer motor frequency was 48 Hz, the air inlet temperature was 180° C., and the air outlet temperature was 80° C., to obtain 0.04 t of macadamia nut protein with a solubility of 43%.

[0059] Comparative Example 2:

[0060] (1) Pre-crushing: The shelled macadamia kernels were crushed using a colloid mill for 33 ± 1 s to obtain defatted macadamia powder, which was pre-crushed to 400 mesh;

[0061] (2) Mixing: 0.1 t of defatted macadamia nut powder from step (1) and 0.9 t of hot water at 50° C. are added into a heat-insulating stirring tank and uniformly mixed to obtain a mixed liquid with a concentration of 10% (w / w);

[0062] (4) High-energy medium milling: The mixed liquid obtained in step (2) was subjected to physical modification using a high-energy medium mill, the frequency of the high-energy medium mill was 53 Hz, the rotation speed was 1000 rpm, the diameter of the grinding beads (zirconia) was 1.2 mm, and the filling degree of the milling cavity beads was 70%;

[0063] (4) The macadamia nut protein neutralized in step (3) was spray-dried, the spray tower atomizer motor frequency was 46 Hz, the air inlet temperature was 180° C., and the air outlet temperature was 80° C., to obtain 0.01 t of macadamia nut protein with a solubility of 32%.

[0064] Embodiment 4:

[0065] In this example, the solubility, emulsification and foaming properties of the macadamia nut proteins prepared in the above examples 1-3 and comparative examples 1-2 were measured and analyzed, and the specific process was as follows:

[0066] (1) Determination of macadamia protein solubility: Kjeldahl method, experimental process refer to GB 5009.5-2016.

[0067] (2) Determination of emulsification and emulsion stability of macadamia nut protein:

[0068] The emulsification and emulsion stability were determined by turbidimetry. 16 mL of macadamia protein solution was taken. 4 mL of macadamia oil was added to the complex and the emulsion was immediately dispersed using a disperser. Then, 50 μL of the emulsion was accurately measured at 0.5 cm from the bottom of the container and dispersed in 10 mL of 0.1% SDS (w / v). The emulsion was vortexed and mixed. The absorbance values ​​A0 and A1 of the emulsion after 0 min and 10 min were measured at a wavelength of 500 nm. 10 . The emulsifying activity index (EAI, m 2 / g) and emulsion stability index (ESI, min) to express the emulsification; the calculation formula is as follows:

[0069]

[0070] Where: DF represents the dilution factor, C represents the protein concentration (g / mL), represents the optical path (1cm), θ represents the volume fraction of oil (v / v)

[0071]

[0072] In the formula: A0 represents the absorbance value at 0 min; A10 represents the absorbance value after 10 min; Δt represents the time difference

[0073] (3) Determination of foaming property and foaming stability of macadamia nut protein:

[0074] Foaming performance and foaming stability: Precisely prepare macadamia protein mixed solutions with different concentration ratios at room temperature, use a disperser to disperse at 10000rpm for 1min, and then quickly transfer to a 100mL measuring cylinder. Record the foaming volume V0 and V2 at 0min and 20min respectively. 20 , the calculation formula of protein foaming ability and foaming stability is as follows:

[0075]

[0076] The above measurement results are shown in Table 1:

[0077] Table 1 Macadamia nut protein performance test results

[0078]

[0079] As shown in Table 1, the combination of chemical modification and high-energy media grinding can significantly increase the solubility of macadamia protein by up to about 4.67 times (see Figure 1 ), the emulsification is increased to a maximum of about 2.23 times, and the foaming is increased to a maximum of about 4.26 times (see Figure 2 ), which significantly improves the functional properties of macadamia protein overall.

[0080] In summary, under the conditions of the present invention, the extraction and modification of macadamia nut protein can be achieved by combining chemical modification with high-energy medium grinding. The process can meet industrial-grade production standards, and the product has excellent physical and chemical properties and broad application prospects.

[0081] Although the description of the present invention has been quite detailed and specifically describes several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as providing a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively covering the intended scope of the present invention. In addition, the above description of the present invention is based on the embodiments foreseeable by the inventor, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that have not yet been foreseen may still represent equivalent changes to the present invention.

Claims

1. A method for preparing highly soluble macadamia nut protein, characterized in that: The preparation method comprises the following steps: S1: crushing the shelled macadamia kernels with a colloid mill to obtain defatted macadamia powder; S2: the defatted macadamia nut powder obtained in step S1 is mixed evenly with water and subjected to high-energy medium grinding, and then compound alkali powder is added and stirred to adjust the pH to 10.5-11, and then citric acid is added to adjust the pH to 6.8-7.0 to obtain a protein solution; S3: spray drying the protein solution obtained in step S2 to finally obtain macadamia nut protein; Wherein, the composite alkali powder is sodium hydroxide and calcium hydroxide.

2. The preparation method according to claim 1, characterized in that: After crushing the macadamia kernels to 400 mesh using a colloid mill, it is necessary to add petroleum ether with a solid-liquid ratio of 0.7-1: 8-10 g / ml for degreasing.

3. The preparation method according to claim 1, characterized in that: The temperature of water in step S2 is 50° C.-55° C.; the ratio of defatted macadamia nut powder to water is 0.6-1:19-19.

8.

4. The preparation method according to claim 1, characterized in that: The mass ratio of sodium hydroxide to calcium hydroxide in the alkali powder is 1:

1.

5. The preparation method according to claim 1, characterized in that: After the pH is adjusted to the target value in step S2, the high energy medium mill needs to be processed for 1-3 hours.

6. The preparation method according to claim 1, characterized in that: In step S2, the frequency of the high energy medium mill is 50 Hz-60 Hz, the rotation speed is 1000-1200 rpm, the diameter of the zirconia grinding beads is 0.6-1.2 mm, and the milling cavity bead filling degree is 70-80%.

7. The preparation method according to claim 1, characterized in that: The particle size of the macadamia nut protein in the protein solution obtained in step S2 is 10 μm-25 μm.

8. The preparation method according to claim 1, characterized in that: In step S3, spray drying adopts a mist drying tower atomizer, and the specific process parameters are as follows: frequency is 45 Hz-50 Hz, inlet air temperature is 160 ℃-180 ℃, and outlet air temperature is 75 ℃-85 ℃.

9. A macadamia nut protein, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 10.

10. Use of the nut protein according to claim 9 in the preparation of medicines, foods and health foods.

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