Rapid evaluation method for stability of protein-based Pickering emulsion

Abstract

The invention discloses a method for rapidly evaluating the stability of a protein-based Pickering emulsion. According to the method, the stability of the emulsion is rapidly pre-judged by preparing the protein-based Pickering emulsion and measuring the electrochemical impedance spectrum of the protein-based Pickering emulsion in an environment with the pH value of 2-8 by utilizing an electrochemical workstation. The specific operation comprises the steps of designing an emulsion equivalent circuit, adjusting the frequency and voltage range of an electrochemical workstation for measurement, and comparing the two measurement results to judge the stability. The method for rapidly evaluating the stability of the protein-based Pickering emulsion has the advantages of simplicity and convenience in operation, low cost and real-time measurement, and can rapidly judge the stability of the protein-based Pickering emulsion in different pH environments within 60 minutes.

Description

Technical Field

[0001] The invention belongs to the field of medical technology, and particularly relates to a method for quickly evaluating the stability of a protein-based Pickering emulsion. Background Art

[0002] Pickering emulsions are mainly concentrated in the food, medicine, cosmetics, materials, chemical and other industries. Protein-based stabilized Pickering emulsions have the advantage of being green and environmentally friendly, and the nutritional value and functional properties of the protein itself can enrich the product effect when combined with the product. However, some food-grade protein-based Pickering particles vary greatly under different pH conditions, affecting the stability of Pickering emulsions in industrial applications. In actual applications, some protein particles only show their functional properties at a specific pH to achieve the stability of the Pickering emulsion. Commonly used detection methods for emulsion stability detection technology include microscope testing, conductivity method, emulsification index method, centrifugation method, etc. These test methods have requirements for instruments, sites and measurement time.

[0003] The Chinese patent with the authorization announcement number CN111887424B discloses a highly stable Pickering emulsion and a preparation method thereof. The patent mainly focuses on improving the physical and oxidative stability of the Pickering emulsion by using whey protein isolate for Maillard reaction and acid-heat treatment in an ethanol-water solution to allow the complex to undergo molecular self-assembly. Although this method has achieved certain results in improving the stability of the emulsion, it mainly focuses on enhancing the stability of the emulsion by physical means, and does not involve predicting the stability of the emulsion under different pH environments by electrochemical behavior.

[0004] Therefore, a method for rapidly evaluating the stability of protein-based Pickering emulsions was developed. This method predicts the stability of samples by analyzing the electrochemical behavior of emulsions under different pH environments. This method can not only rapidly evaluate the stability of emulsions, but also provide more accurate predictions for the stability of emulsions under different pH conditions, which is of great significance for emulsion stability control in industrial applications. Summary of the invention

[0005] The present invention aims to provide a method for rapidly evaluating the stability of a protein-based Pickering emulsion, which predicts the stability of a sample in different pH environments by analyzing the electrochemical behavior of the emulsion in different pH environments.

[0006] The technical solution adopted by the present invention is: a rapid evaluation method for the stability of a protein-based Pickering emulsion, comprising the following steps:

[0007] a. Preparing a protein-based Pickering emulsion;

[0008] b. Design the equivalent circuit of the emulsion;

[0009] c. Based on the electrochemical behavior of the emulsion in different pH environments, predict the stability of the sample in different pH environments.

[0010] Furthermore, the protein-based Pickering emulsion is prepared by mixing protein and oil phase.

[0011] Furthermore, the electrochemical behavior of the emulsion under different pH environments is achieved by measuring the electrochemical impedance spectrum of the Pickering emulsion under pH 2 to 8 environments.

[0012] Furthermore, the electrochemical impedance spectrum is measured and recorded by an electrochemical workstation, which includes a glassy carbon working electrode, a calomel reference electrode, a platinum sheet auxiliary electrode and an electrolytic cell.

[0013] Further, the measuring comprises the following steps:

[0014] a. Insert the platinum auxiliary electrode, glassy carbon working electrode and saturated calomel reference electrode into the emulsion layer;

[0015] b. Adjust the frequency range from 100 Hz to 100 kHz and the disturbance voltage range from 1.0 V to -1.0 V, measure and record the electrochemical impedance spectrum of the emulsion.

[0016] Furthermore, the rapid evaluation method determines the stability of the emulsion by the following steps:

[0017] a. Conduct impedance spectrum measurement twice;

[0018] b. Compare the difference between the two spectra. If the two spectra match, the emulsion is considered stable; if they do not match, the emulsion is considered unstable.

[0019] Furthermore, the method can complete the evaluation of the stability of Pickering emulsion in different pH environments within 60 minutes.

[0020] The beneficial effects of the present invention are as follows: the present invention provides a method for rapidly evaluating the stability of a protein-based Pickering emulsion, wherein a small-amplitude sinusoidal potential and current disturbance signal is applied to the emulsion system through an electrochemical workstation, and data on the ratio of the AC potential to the current signal as a function of the sinusoidal frequency and data on the phase angle of the impedance as a function of the sinusoidal frequency are obtained, and a spectrum of dielectric changes of the protein in the emulsion is predicted. The method provided by the present invention can rapidly determine the stability of the emulsion at different pH values ​​within 60 minutes, and is low in cost, easy to operate, and has the characteristics of real-time measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0022] Figure 1 This is a schematic diagram of the impedance of an emulsion changing with time at pH 2 in a method for rapidly evaluating the stability of a protein-based Pickering emulsion according to the present invention, wherein Z' is the capacitance value of the emulsion, and Z" is the resistance value of the emulsion;

[0023] Figure 2 This is a schematic diagram of the impedance of an emulsion changing with time at pH 8 according to a method for rapidly evaluating the stability of a protein-based Pickering emulsion according to the present invention, wherein Z' is the capacitance value of the emulsion and Z" is the resistance value of the emulsion. DETAILED DESCRIPTION

[0024] In the following detailed description of the embodiments, some specific details are proposed to allow those skilled in the art to have a more thorough understanding of the present invention. However, it should be clear to those skilled in the art that the implementation of the present invention may not be limited to only these specific details. In other cases, well-known technical solutions are not described in detail to avoid ambiguity in the relevant details of the following embodiments.

[0025] Example 1: Evaluation of emulsion stability at pH 2

[0026] 1. Prepare soy protein isolate and use deionized water to prepare a suspension with a concentration of 20 mg / mL.

[0027] 2. Gently stir the suspension at 4°C for 12 hours to fully hydrate the protein.

[0028] 3. The pH of part of the suspension was adjusted to 2 using 0.5 M HCl to form the raw material for the acidic protein-based Pickering emulsion.

[0029] 4. Take equal volumes of corn germ oil and acidic protein suspension and mix them. Use a high-pressure shearing machine to homogenize at a speed of 10,000 r / min for 1 minute to prepare an emulsion under pH 2 conditions.

[0030] 5. Insert the platinum auxiliary electrode, glassy carbon working electrode, and saturated calomel reference electrode into the prepared emulsion layer.

[0031] 6. Adjust the frequency range of the electrochemical workstation to 100 Hz to 100 kHz, the disturbance voltage range to 1.0 V to -1.0 V, and start measuring and recording the electrochemical impedance spectrum of the emulsion.

[0032] 7. Repeat steps 5 and 6 to measure the impedance spectrum for the second time and compare it with the first spectrum to evaluate the stability of the emulsion.

[0033] Example 2: Evaluation of emulsion stability at pH 8

[0034] 1. Prepare soy protein isolate and use deionized water to prepare a suspension with a concentration of 20 mg / mL.

[0035] 2. Gently stir the suspension at 4°C for 12 hours to fully hydrate the protein.

[0036] 3. The pH of part of the suspension was adjusted to 8 using 0.5 M NaOH to form the raw material of the basic protein-based Pickering emulsion.

[0037] 4. Take equal volumes of corn germ oil and alkaline protein suspension and mix them. Use a high-pressure shearing machine to homogenize at a speed of 10,000 r / min for 1 minute to prepare an emulsion at pH 8.

[0038] 5. Insert the platinum auxiliary electrode, glassy carbon working electrode, and saturated calomel reference electrode into the prepared emulsion layer.

[0039] 6. Adjust the frequency range of the electrochemical workstation to 100 Hz to 100 kHz, the disturbance voltage range to 1.0 V to -1.0 V, and start measuring and recording the electrochemical impedance spectrum of the emulsion.

[0040] 7. Repeat steps 5 and 6 to measure the impedance spectrum for the second time, and compare it with the first spectrum to evaluate the stability of the emulsion. The present invention evaluates the storage stability of the two emulsions with different pH values. Figure 1 As shown in the figure, under the condition of pH 2, the electrochemical impedance spectrum of the emulsion shows a high consistency in the test time of 30 to 330 minutes, which indicates that the emulsion exhibits good stability in an acidic environment. The consistency of the impedance spectrum is a key indicator for evaluating the stability of the emulsion. Good consistency means that the physical properties of the emulsion remain unchanged for a long time, thus confirming its stability under pH 2 conditions. In contrast, Figure 2 As shown in the figure, the electrochemical impedance spectrum of the emulsion at pH 8 has a poor agreement with the impedance spectrum during the same test time, which indicates that the stability of the emulsion is poor in an alkaline environment. Figure 1 and Figure 2 The comparative analysis shows that the rapid evaluation method for the stability of a protein-based Pickering emulsion described in the present invention can quickly determine the stability of the emulsion at different pH values ​​within 60 minutes.

[0041] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A rapid evaluation method for the stability of a protein-based Pickering emulsion, characterized in that: The following steps are involved: a. Preparing a protein-based Pickering emulsion; b. Design the equivalent circuit of the emulsion; c. Based on the electrochemical behavior of the emulsion in different pH environments, predict the stability of the sample in different pH environments.

2. A rapid evaluation method for the stability of a protein-based Pickering emulsion according to claim 1, characterized in that: The protein-based Pickering emulsion is prepared by mixing protein and oil phase.

3. A rapid evaluation method for the stability of a protein-based Pickering emulsion according to claim 1, characterized in that: The electrochemical behavior of the emulsion under different pH environments is achieved by measuring the electrochemical impedance spectrum of the Pickering emulsion under pH 2 to 8 environments.

4. A rapid evaluation method for the stability of a protein-based Pickering emulsion according to claim 3, characterized in that: The electrochemical impedance spectrum is measured and recorded by an electrochemical workstation, which includes a glassy carbon working electrode, a calomel reference electrode, a platinum sheet auxiliary electrode and an electrolytic cell.

5. A rapid evaluation method for the stability of a protein-based Pickering emulsion according to claim 4, wherein the measurement comprises the following steps: a. Insert the platinum auxiliary electrode, glassy carbon working electrode and saturated calomel reference electrode into the emulsion layer; b. Adjust the frequency range from 100 Hz to 100 kHz and the disturbance voltage range from 1.0 V to -1.0 V, measure and record the electrochemical impedance spectrum of the emulsion.

6. A method for rapid evaluation of the stability of a protein-based Pickering emulsion according to claim 1, characterized in that: The rapid evaluation method determines the stability of the emulsion by the following steps: a. Conduct impedance spectrum measurement twice; b. Compare the difference between the two spectra. If the two spectra match, the emulsion is considered stable; if they do not match, the emulsion is considered unstable.

7. A method for rapid evaluation of the stability of a protein-based Pickering emulsion according to claim 1, characterized in that: This method can complete the evaluation of the stability of Pickering emulsion in different pH environments within 60 minutes.

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