Method for preparing Pickering emulsifier from peanut protein

Abstract

The invention belongs to the field of preparation of Pickering emulsions, and particularly relates to a method for preparing a Pickering emulsifier from peanut protein. The preparation method of the emulsifier comprises the following steps: 1, preparing a peanut protein solution from peanut protein, and adjusting the pH value of the peanut protein solution to be neutral; step 2, heating the neutral peanut protein solution obtained in the step 1 at 90-100 DEG C; in order to further improve the stability of the Pickering emulsion in which the emulsifier participates in preparation, the preparation method of the emulsifier further comprises the following steps: step 3, heating, cooling to room temperature, and freeze-drying; carrying out superfine grinding on the freeze-dried peanut protein, redissolving and centrifuging to obtain soluble aggregate and insoluble aggregate; and 4, mixing the soluble aggregate and the insoluble aggregate according to a weight ratio of (0-1): 2. Wherein when the insoluble aggregate is completely used as the emulsifier to prepare the Pickering emulsion, the stability of the Pickering emulsion is optimal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of preparation of Pickering emulsions, and particularly relates to a method for preparing Pickering emulsifiers using peanut protein. BACKGROUND

[0002] Pickering emulsion refers to an emulsion obtained by using superfine solid particles as emulsifiers, also known as Pickering emulsion. The emulsifiers used to prepare Pickering emulsion can also be called Pickering emulsifiers. Current technologies ([1] China Agricultural University. Xanthan gum-corn protein-based Pickering emulsion and its preparation method: 202410975 707.8[P]. 2024-09-27. [2] China Ocean University. Restrictive enzyme hydrolysis of pea protein isolate-chitosan Pickering emulsion and its preparation method and application: 202510389328.5[P]. 2025.6.24 [3] Ma Q, Bu X, Nie C, et al. Impact of interactions between peanut protein isolate and cellulose nanocrystals on the properties of Pickering emulsions: Rheological properties and physical stabilities[J]. International Journal of Biological Macromolecules, 2023, 233: 123527. [4] Xu X, Wang M, Zhang K, et al. Study on the stability of Pickering emulsion stabilized by wheat protein nanoparticles[J]. Journal of Food Safety and Quality Inspection, 2023, 14(08): 148-154. DOI: 10.19812 / j.cnki.jfsq 11-5956 / ts.2023.08.048. [5] Ge Y, Shi A, Ren G, et al. Effect of ultrasonic pretreatment on the structure of peanut protein microgel particles and the properties of Pickering emulsion[J]. Food Science, 2022, 43(20): 95-101. [6] HEI X, LIU Z, LI S, et al. Freeze-thaw stability of Pickering emulsion stabilized by modified soy protein particles and its application in plant-based ice cream[J]. International Journal of Biological Macromolecules, 2024, 257: 128183.) mostly use protein-polymer complex or protein microgel particles as emulsifiers to prepare Pickering emulsion, and the preparation process of Pickering emulsifier is relatively complex. SUMMARY

[0003] In order to improve the utilization value of peanut protein, the insoluble aggregates generated by heat treatment of peanut protein are used as emulsifiers to prepare Pickering emulsion, and the Pickering emulsion obtained has high stability.

[0004] The Pickering emulsion prepared from peanut protein includes the following steps: Step 1: peanut protein solution is prepared from peanut protein, and the pH value of the peanut protein solution is adjusted to neutral; preferably, the mass fraction of the peanut protein solution is 10%, and the pH value is 7; in addition, after the pH value is adjusted to neutral, the solution is stirred to hydrate.

[0005] Step 2: the neutral peanut protein solution obtained in step 1 is heated at 90-100°C. Specifically, the heating is performed by water bath at 90-100°C, and the heating time is 30-90 min.

[0006] In order to further improve the stability of the Pickering emulsion prepared by the above emulsifier, the preparation method of the emulsifier further includes: Step 3: after heating treatment, cooling to room temperature and freeze-drying; the freeze-dried peanut protein is ultra-finely pulverized, and after re-dissolution, centrifugation is performed to obtain supernatant and precipitate, the supernatant is soluble aggregate, and the precipitate is insoluble aggregate. The mass fraction of the re-dissolved peanut protein solution is 1%.

[0007] Step 4: the soluble aggregate and the insoluble aggregate are mixed according to a weight ratio of (0-1):2. When the amount of the soluble aggregate is 0, i.e., the insoluble aggregate is used as the emulsifier to prepare the Pickering emulsion, the stability of the Pickering emulsion is best.

[0008] The application also provides a Pickering emulsion prepared by using the above Pickering emulsifier. Specifically, the emulsifier and soybean oil are mixed according to a volume ratio of 1:1, and then sheared to prepare the Pickering emulsion. The shearing is high-speed shearing at 15000 r / min for 2 min 20 s.

[0009] The application has the following beneficial effects: Compared with the existing preparation of Pickering emulsion which mostly uses composite emulsifiers, the insoluble aggregates of peanut protein prepared by the application can independently stabilize the Pickering emulsion, which provides more possibilities for single protein as the emulsifier of Pickering emulsion, and also provides a theoretical basis for the high-value application of peanut protein. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1: Pictures of the appearance of Pickering emulsions prepared with different peanut protein preparations. Note: 1: untreated PP; 2: PP-90; 3: mixed PP-90; 4: insoluble PP-90.

[0011] Figure 2 : Stability curves of Pickering emulsions prepared with different peanut protein preparations.

[0012] Figure 3 : Unstability coefficients of Pickering emulsions prepared with different peanut protein preparations.

[0013] Figure 4 : Comparison chart of freeze-thaw stability of Pickering emulsions prepared with insoluble peanut protein aggregates and peanut protein microgel particles. Note: 1: insoluble PP-90; 2: peanut protein microgel particles. DETAILED DESCRIPTION

[0014] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0015] Example 1: Preparation of Pickering emulsions using peanut protein Peanut protein was extracted from peanut kernels using the method of alkali dissolution and acid precipitation. Specifically, untreated peanut kernels (300 g) were ground in a universal blender for 3 min, and an appropriate amount of peanut slurry was dispersed in 6 times distilled water, and the pH was adjusted to 10.0 (2 mol / L NaOH). The peanut slurry was placed in a 50 ℃ room temperature water bath shaker (150 r / min) for 30 min, and then centrifuged (3300 x g, 15 min) to remove the upper oil layer, cream layer and lower precipitate. The supernatant was adjusted to pH 4.5 (2 mol / L HCl) to precipitate the peanut protein, and the precipitate was washed twice with water and centrifuged (3300 x g, 10 min) to obtain peanut protein, which was freeze-dried. Then it was dissolved in distilled water to prepare a peanut protein solution with a mass fraction of 10%, and the pH value was adjusted to 7.0. The solution was stirred overnight at room temperature to allow it to hydrate fully. 35 mL of the above peanut protein solution was heated at room temperature (PP) and in a 90 ℃ water bath (PP-90) for 30 min, respectively. After cooling to room temperature in an ice water bath immediately after the end of heating, the freeze-dried product was reserved for later use. Finally, the freeze-dried peanut protein was ultra-finely ground and reconstituted to a mass fraction of 1%. After centrifugation at 6000 r / min, the supernatant was freeze-dried to obtain the soluble aggregates, and the lower precipitate was freeze-dried to obtain the insoluble aggregates.

[0016] The peanut protein of different treatments (PP, PP-90, mixed PP-90, and insoluble PP-90) was formulated into a peanut protein solution with a mass fraction of 3% to obtain a Pickering emulsifier, and then the Pickering emulsifier was mixed with soybean oil at a volume ratio of 1:1, and then high-speed sheared at 15000 r / min for 2 min 20 s to prepare a Pickering emulsion.

[0017] Table 1, source of peanut protein in different Pickering emulsifiers Example 2: Stability study of the Pickering emulsion prepared in Example 1 This example studies the storage stability, salt tolerance, and freeze-thaw stability of different Pickering emulsions.

[0018] Storage stability: freshly prepared Pickering emulsion (15 mL) was placed in a sealed vial, and sodium azide (0.2 mg / mL) was added to inhibit microbial growth. The Pickering emulsion was observed for changes during storage (14 d) at room temperature.

[0019] Salt tolerance: CaCl2 powder was added to freshly prepared Pickering emulsion to achieve a CaCl2 concentration of 150 mmol / L, and the mixture was stirred uniformly and then placed in a 4 ℃ refrigerator. The Pickering emulsion was observed for delamination within 14 d.

[0020] Freeze-thaw stability: 20 mL of freshly prepared Pickering emulsion was placed in a -20 ℃ refrigerator for 20 h, then taken out and placed in an oven for 2 h at 30 ℃ for thawing. The Pickering emulsion was observed for changes.

[0021] Centrifugal stability: LUMiFuge instrument was used for stability analysis, with a speed of 6000 rpm and a time of 20 min.

[0022] It was found that, compared with the protein without heating treatment, the Pickering emulsion prepared from heat-treated peanut protein (PP-90, mixed PP-90, and insoluble PP-90) had no obvious phase separation after storage for 14 d, introduction of salt ions, and freezing at -20 ℃, which indicated that heat treatment could significantly improve the stability of the Pickering emulsion of peanut protein; as the proportion of insoluble protein aggregates increased, the storage stability, salt tolerance, and freeze-thaw stability of the Pickering emulsion did not change significantly, as shown in Table 2. Figure 1 This indicates that the Pickering emulsion prepared from heat-treated peanut protein of the present application as a Pickering emulsifier has better storage stability, salt tolerance, and freeze-thaw stability.

[0023] To further distinguish the different sample emulsions, the freshly prepared Pickering emulsion was subjected to centrifugal stability test.Figure 2 The results show that the transmittance of the untreated sample increases earliest and has the highest final value, indicating that phase separation occurs earliest and has the worst stability, and as the proportion of insoluble aggregates increases, the prepared Pickering emulsion is more stable. Figure 3 The experimental results show that the Pickering emulsion prepared from the heat-treated peanut protein has a lower instability coefficient value, and gradually decreases with the increase of the proportion of insoluble aggregates. This shows that the Pickering emulsion prepared by using the insoluble aggregates produced by heat-treated peanut protein as the Pickering emulsifier has higher stability.

[0024] Example 3: Comparative test Transglutaminase (35 U / g peanut protein) was added to a 10% peanut protein solution without heat treatment and heated in a 45℃ water bath for 4h. Then 2 times the volume of deionized water was added, followed by shearing with a high-speed shearing machine at 12 000 r / min for 2 min, and then a high-pressure homogenizer was used to cycle 3 times at a pressure of 500 bar to obtain a peanut protein microgel particle dispersion, which was then diluted to 3%, and then mixed with soybean oil at a volume ratio of 1:1, and then sheared at a high speed of 15000 r / min for 2 min 20 s to prepare a Pickering emulsion.

[0025] 20 mL of the fresh Pickering emulsion prepared from the peanut protein microgel particles (at the same time, the Pickering emulsion prepared from insoluble PP-90 in Example 1 was used as a control) was placed in a -20℃ refrigerator for 20h, then taken out and placed in an oven, and observed for changes in the Pickering emulsion after thawing at 30℃ for 2h.

[0026] Figure 4 As can be seen from the above, the Pickering emulsion prepared from the insoluble aggregates (insoluble PP-90) did not show obvious oil phase separation, while the Pickering emulsion prepared from the peanut protein microgel particles showed obvious water-oil separation, which indicates that the insoluble aggregates produced by heat-treated peanut protein have stronger emulsifying performance than the microgel particles.

[0027] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A Pickering emulsifier prepared using peanut protein, characterized in that, The method for preparing the emulsifier includes: Step 1: Prepare a peanut protein solution using peanut protein and adjust the pH of the peanut protein solution to neutral. Step 2: Heat the neutral peanut protein solution obtained in Step 1 at 90℃~100℃.

2. The Pickering emulsifier prepared using peanut protein according to claim 1, characterized in that, In step 1, the peanut protein solution has a mass fraction of 10%.

3. The Pickering emulsifier prepared using peanut protein according to claim 1, characterized in that, In step 1, the pH value is 7.

4. The Pickering emulsifier prepared using peanut protein according to claim 1, characterized in that, In step 1, after adjusting the pH to neutral, the solution is stirred to hydrate it.

5. The Pickering emulsifier prepared using peanut protein according to claim 1, characterized in that, In step 2, the water is heated at 90℃~100℃ for 30min~90min.

6. The Pickering emulsifier prepared using peanut protein according to claim 1, characterized in that, The method for preparing the emulsifier further includes: Step 3: After heat treatment, cool to room temperature and freeze dry; pulverize the freeze-dried peanut protein into ultrafine particles, reconstitute, and centrifuge to obtain supernatant and precipitate. The supernatant is a soluble aggregate, and the precipitate is an insoluble aggregate. Step 4: Mix the soluble aggregates and the insoluble aggregates at a weight ratio of (0-1):

2.

7. The Pickering emulsifier prepared using peanut protein according to claim 6, characterized in that, In step 3, the mass fraction of the reconstituted peanut protein solution is 1%.

8. A Pickering emulsion prepared using the Pickering emulsifier according to any one of claims 1-7.

9. The Pickering emulsion according to claim 8, characterized in that, The emulsifier was mixed with soybean oil at a volume ratio of 1:1, and then sheared to obtain Pickering emulsion.

10. The Pickering emulsion according to claim 9, characterized in that, The shearing was performed at a high speed of 15000 r / min for 2 min 20 s.

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