Quinoa protein compound and preparation method thereof

Abstract

The invention relates to the technical field of plant protein, in particular to a quinoa protein compound and a preparation method thereof. The invention provides a preparation method of a chenopodium quinoa protein compound, which comprises the following steps: breaking the aggregation state of chenopodium quinoa protein by using a dilute alkali solution, carrying out structural assembly by introducing foreign protein and chenopodium quinoa protein, and then inhibiting folding and aggregation of a protein structure in a solution neutralization process by virtue of protein synergistic interaction, so that the chenopodium quinoa protein compound keeps relatively good solubility. According to the invention, the solubility and stability are improved through protein modification, and the dosage of traditional emulsifiers and stabilizers in a food system can be reduced.

Description

Technical Field

[0001] This invention relates to the field of plant protein technology, and in particular to a quinoa protein complex and its preparation method. Background Technology

[0002] Plant proteins are increasingly favored in the food industry due to their sustainability, health benefits, and compliance with vegetarian requirements. Quinoa protein, as a high-quality plant protein, is rich in essential amino acids, has high nutritional value, and possesses broad market prospects. However, quinoa protein exhibits poor solubility in food systems under neutral pH conditions, and is prone to aggregation and sedimentation in solutions, limiting its application in liquid beverages, emulsification systems, and other fields. Solubility is fundamental to the functional properties of proteins; poor solubility directly leads to the deterioration of its emulsifying, foaming, and gelling properties, preventing it from fully realizing its nutritional and processing advantages.

[0003] Currently, methods for improving the solubility of plant proteins mainly include physical modification (such as ultrasonication and high-pressure homogenization), chemical modification (such as acylation and phosphorylation), and enzymatic modification. These methods either suffer from high equipment costs and energy consumption, or may introduce chemical reagents raising safety concerns, or are complex and difficult to scale up. Therefore, developing a green, efficient, and safe physical co-processing method to significantly improve the solubility of quinoa protein is a pressing technical problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing quinoa protein complex, which can not only maintain the integrity of the primary structure of quinoa protein, but also achieve high solubility of quinoa protein.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a quinoa protein complex, comprising the following steps: (1) Prepare a quinoa protein solution with a mass concentration of 0.5-5% using water as a solvent; adjust the pH of the quinoa protein solution to 7.5-9.0 and then hydrate and stir to obtain a hydrated quinoa protein solution; (2) Prepare a whey protein solution with a mass concentration of 0.5-5% using water as a solvent; adjust the pH of the whey protein solution to 6.5-8.0, then hydrate and centrifuge, and take the supernatant to obtain whey protein supernatant; (3) Mix the hydrated quinoa protein solution and whey protein supernatant to obtain a mixed solution; (4) After adjusting the pH of the mixed solution to 11.0~12.0, heat treatment is performed to obtain the treated solution; (5) After adjusting the pH of the treated solution to 6.5-7.5, centrifuge and take the supernatant to obtain the quinoa protein complex.

[0006] Preferably, in step (1), the hydration temperature is 4~10℃; and the hydration time is 8~12h. The stirring time is 20-40 minutes.

[0007] Preferably, in step (2), the hydration temperature is 4~10℃ and the hydration time is 8~12h.

[0008] Preferably, in step (2), the centrifugation speed is 3000~5000g; the centrifugation time is 5~15min.

[0009] Preferably, in step (3), the final concentration ratio of quinoa protein to whey protein in the mixed solution is 1:0.025~0.5.

[0010] Preferably, in step (4), the temperature of the heat treatment is 60~90℃ and the time of the heat treatment is 10~30min.

[0011] Preferably, in step (5), the centrifugation speed is 3000~5000g; the centrifugation time is 5~15min.

[0012] The present invention also provides the preparation method described above to prepare a quinoa protein complex with high solubility.

[0013] Technical effects: This invention provides a method for preparing quinoa protein complex. The method utilizes a dilute alkaline solution to break up the aggregated state of quinoa protein, introduces exogenous proteins to assemble with quinoa protein, and then uses protein synergistic interactions to inhibit protein folding and aggregation during neutralization, thus maintaining good solubility. Due to the high solubility of the quinoa protein complex itself, the product system is homogeneous and does not easily precipitate or separate when stored at neutral pH. This invention improves its solubility and stability through protein modification, which helps reduce the amount of traditional emulsifiers and stabilizers used in food systems. The quinoa protein complex prepared by this invention has a significantly higher protein solubility than the single quinoa protein extract under neutral pH conditions; specifically, the nitrogen solubility index is not less than 90% at pH 7.0 and room temperature (20~28℃), and no obvious precipitation is observed after standing for 14 days under refrigeration conditions (2~6℃). Attached Figure Description

[0014] Figure 1The dissolution results of quinoa protein in each group are shown from left to right: quinoa protein solution before centrifugation in Comparative Example 1, quinoa protein solution after centrifugation in Comparative Example 1, quinoa protein solution after centrifugation in Comparative Example 2, quinoa protein complex in Example 1, and quinoa protein complex in Example 2. Detailed Implementation

[0015] This invention provides a method for preparing a quinoa protein complex, comprising the following steps: (1) Prepare a quinoa protein solution with a mass concentration of 0.5-5% using water as a solvent; adjust the pH of the quinoa protein solution to 7.5-9.0 and then hydrate and stir to obtain a hydrated quinoa protein solution; (2) Prepare a whey protein solution with a mass concentration of 0.5-5% using water as a solvent; adjust the pH of the whey protein solution to 6.5-8.0, then hydrate and centrifuge, and take the supernatant to obtain whey protein supernatant; (3) Mix the hydrated quinoa protein solution and whey protein supernatant to obtain a mixed solution; (4) After adjusting the pH of the mixed solution to 11.0~12.0, heat treatment is performed to obtain the treated solution; (5) After adjusting the pH of the treated solution to 6.5-7.5, centrifuge and take the supernatant to obtain the quinoa protein complex.

[0016] In this invention, in step (1), the mass concentration of the quinoa protein solution is preferably 1.5-4%, more preferably 2.75%; The pH is preferably 8.0 to 8.5, and more preferably 8.25; The hydration temperature is 4~10℃, preferably 6~8℃, and more preferably 7℃; the hydration time is 8~12h, preferably 9~11h, and more preferably 10h. The stirring time is 20-40 minutes, preferably 25-35 minutes, and more preferably 30 minutes.

[0017] In this invention, in step (2), the mass concentration of the whey protein solution is preferably 1.5-4%, more preferably 2.75%; The pH is preferably 7.0 to 7.5, and more preferably 7.25; The hydration temperature is 4~10℃, preferably 6~8℃, and more preferably 7℃; the hydration time is 8~12h, preferably 9~11h, and more preferably 10h.

[0018] The centrifugation speed is 3000~5000g, preferably 3500~4500g, and more preferably 4000g; the centrifugation time is 5~15min, preferably 8~12min, and more preferably 10min.

[0019] In this invention, in step (3), the final concentration ratio of quinoa protein to whey protein in the mixed solution is 1:0.025~0.5, preferably 1:0.15~0.375, and more preferably 1:0.2625.

[0020] In this invention, in step (4), the pH is preferably 11.3 to 11.7, and more preferably 11.5; The heat treatment temperature is 60~90℃, preferably 70~80℃, and more preferably 75℃; the heat treatment time is 10~30min, preferably 15~25min, and more preferably 20min.

[0021] In this invention, in step (5), the treated solution needs to be rapidly cooled to 20~28°C before adjusting the pH, preferably 22~26°C, and more preferably 24°C; The pH is preferably 6.8 to 7.2, and more preferably 7.0; The centrifugation speed is 3000~5000g, preferably 3500~4500g, and more preferably 4000g; the centrifugation time is 5~15min, preferably 8~12min, and more preferably 10min.

[0022] In this invention, the solution used for adjusting pH in steps (1) to (5) is a 1 mol / L sodium hydroxide solution, a 1 mol / L potassium hydroxide solution, a 1 mol / L hydrochloric acid solution, or a 1 mol / L citric acid solution.

[0023] The present invention also provides the preparation method described above to prepare a quinoa protein complex with high solubility.

[0024] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0025] Example 1: A quinoa protein complex

[0026] (1) Using water as a solvent, prepare a quinoa protein solution with a mass concentration of 2%; adjust the pH of the quinoa protein solution to 7.5 using 1 mol / L sodium hydroxide solution, place it at 4℃ for 10 h to fully hydrate, and then stir for 30 min to obtain the hydrated quinoa protein solution. (2) Prepare a whey protein solution with a mass concentration of 2% using water as a solvent; adjust the pH of the whey protein solution to 7.5 using 1 mol / L sodium hydroxide solution, place it at 4℃ for 10 h to fully hydrate, then centrifuge at 3000g for 10 min, and take the supernatant to obtain whey protein supernatant. (3) Mix the hydrated quinoa protein solution and whey protein supernatant (the final concentration ratio of quinoa protein to whey protein is 1:0.15) to obtain a mixed solution; (4) After adjusting the pH of the mixed solution to 11.0 with 1 mol / L sodium hydroxide solution, heat-treat it in an 85℃ water bath for 30 min to obtain the treated solution; (5) After cooling the treated solution to 25°C, adjust the pH to 7.5 with 1 mol / L citric acid solution, then centrifuge at 3000g for 10 min, and take the supernatant to obtain the quinoa protein complex.

[0027] Example 2: A quinoa protein complex

[0028] (1) Using water as a solvent, prepare a quinoa protein solution with a mass concentration of 3%; adjust the pH of the quinoa protein solution to 7.5 using 1 mol / L sodium hydroxide solution, place it at 4℃ for 10 h to fully hydrate, and then stir for 30 min to obtain the hydrated quinoa protein solution. (2) Prepare a whey protein solution with a mass concentration of 3% using water as a solvent; adjust the pH of the whey protein solution to 7.5 using 1 mol / L sodium hydroxide solution, place it at 4℃ for 10 h to fully hydrate, then centrifuge at 3000g for 10 min, and take the supernatant to obtain whey protein supernatant. (3) Mix the hydrated quinoa protein solution and whey protein supernatant (the final concentration ratio of quinoa protein to whey protein is 1:0.15) to obtain a mixed solution; (4) After adjusting the pH of the mixed solution to 11.0 with 1 mol / L sodium hydroxide solution, heat-treat it in an 85℃ water bath for 30 min to obtain the treated solution; (5) After cooling the treated solution to 25°C, adjust the pH to 7.5 with 1 mol / L citric acid solution, then centrifuge at 3000g for 10 min, and take the supernatant to obtain the quinoa protein complex.

[0029] Comparative Example 1

[0030] A quinoa protein solution with a mass concentration of 2% was prepared using water as a solvent. The pH of the quinoa protein solution was adjusted to 7.5 using 1 mol / L sodium hydroxide solution, and then it was placed at 4℃ for 10 h to fully hydrate. After that, it was centrifuged at 3000g for 10 min, and the supernatant was collected.

[0031] Comparative Example 2

[0032] A 2% (w / w) quinoa protein solution was prepared using water as a solvent. The pH of the quinoa protein solution was adjusted to 7.5 using 1 mol / L sodium hydroxide solution, and then allowed to fully hydrate at 4°C for 10 hours. The solution was stirred for 30 minutes to obtain a hydrated quinoa protein solution. The pH of the hydrated quinoa protein solution was adjusted to 11.0 using 1 mol / L sodium hydroxide solution, and then heat-treated in an 85°C water bath for 30 minutes to obtain a treated solution. The pH of the treated solution was adjusted to 7.5 using 1 mol / L citric acid solution, and then centrifuged at 3000g for 10 minutes. The supernatant was collected.

[0033] Experimental Example

[0034] The turbidity of the quinoa protein solution before centrifugation in Comparative Example 1, the quinoa protein solution after centrifugation in Comparative Example 1, the quinoa protein complex in Comparative Example 2, the quinoa protein complex in Example 1, and the quinoa protein complex in Example 2 were observed. The results are as follows: Figure 1 As shown; The nitrogen content in the quinoa protein solution of Comparative Example 1, the quinoa protein solution of Comparative Example 2, the quinoa protein complex of Example 1, and the quinoa protein complex of Example 2 before and after centrifugation (denoted as N1 and N2, respectively), as well as the nitrogen content in the whey protein supernatant (denoted as N3), was determined by the Kjeldahl method. The nitrogen solubility index (NSI) was calculated, and the results are shown in Table 1. NSI = (N1-N3) / (N2-N3)×100%, where N1 is the nitrogen content in the supernatant of the sample after centrifugation, N3 is the nitrogen content of the sample with added whey protein (only for Examples 1 and 2, the content is zero in the comparative example), and N2 is the nitrogen content of the sample before centrifugation. Table 1. Nitrogen solubility index of each group of samples

[0035] The results showed that the turbidity decreased significantly before and after centrifugation in the comparative example. The solution before centrifugation contained a large amount of undissolved protein, which was very easy to aggregate and precipitate. pH adjustment treatment could significantly increase protein solubility, especially after co-treatment with whey protein, the nitrogen solubility index of quinoa protein increased to over 90%.

[0036] As can be seen from the above embodiments, the present invention provides a quinoa protein complex and its preparation method. The method improves its solubility and stability through protein modification, which helps to reduce the amount of traditional emulsifiers and stabilizers used. The quinoa protein complex prepared by the present invention has significantly higher protein solubility than single quinoa protein extract under neutral pH conditions.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a quinoa protein complex, characterized in that, Includes the following steps: (1) Prepare a quinoa protein solution with a mass concentration of 0.5-5% using water as a solvent; adjust the pH of the quinoa protein solution to 7.5-9.0 and then hydrate and stir to obtain a hydrated quinoa protein solution; (2) Prepare a whey protein solution with a mass concentration of 0.5-5% using water as a solvent; After adjusting the pH of the whey protein solution to 6.5-8.0, hydrate and centrifuge, and collect the supernatant to obtain whey protein supernatant; (3) Mix the hydrated quinoa protein solution and whey protein supernatant to obtain a mixed solution; (4) After adjusting the pH of the mixed solution to 11.0~12.0, heat treatment is performed to obtain the treated solution; (5) After adjusting the pH of the treated solution to 6.5-7.5, centrifuge and take the supernatant to obtain the quinoa protein complex.

2. The preparation method according to claim 1, characterized in that, In step (1), the hydration temperature is 4~10℃; the hydration time is 8~12h; The stirring time is 20-40 minutes.

3. The preparation method according to claim 1, characterized in that, In step (2), the hydration temperature is 4~10℃; the hydration time is 8~12h.

4. The preparation method according to claim 1, characterized in that, In step (2), the centrifugation speed is 3000~5000g; the centrifugation time is 5~15min.

5. The preparation method according to claim 1, characterized in that, In step (3), the final concentration ratio of quinoa protein to whey protein in the mixed solution is 1:0.025~0.

5.

6. The preparation method according to claim 1, characterized in that, In step (4), the temperature of the heat treatment is 60~90℃; the time of the heat treatment is 10~30min.

7. The preparation method according to claim 1, characterized in that, In step (5), the centrifugation speed is 3000~5000g; the centrifugation time is 5~15min.

8. The preparation method according to any one of claims 1 to 7 yields a quinoa protein complex with high solubility.

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