Preparation method of pea protein isolate-tea saponin nano-emulsion

Abstract

The invention discloses a pea protein isolate-tea saponin nano-emulsion and a preparation technology thereof. The preparation method comprises the following steps: mixing a pea protein isolate solution and tea saponin to form composite nanoparticles, mixing the composite nanoparticles as a water-phase emulsifier with medium-chain triglyceride, and carrying out shearing homogenization and ultrasonic treatment to prepare the nano-emulsion. The nano-emulsion prepared by the invention has the advantages of green and natural raw materials, good rheological property, uniform liquid drop distribution, simple preparation process, low cost, safety, environmental protection and the like. The nano-emulsion has remarkable application advantages in the fields of food functional factor delivery, drug controlled release carrier or cosmetic active ingredient wrapping and the like.

Description

Technical Field

[0001] The invention relates to a preparation method of pea protein isolate-tea saponin nanoemulsion, belonging to the technical field of food processing. Background Art

[0002] In the food processing sector, nanoemulsions offer significant advantages over traditional emulsions due to their unique physicochemical properties. Their nanoparticle size imparts high dispersibility and kinetic stability, effectively delaying or inhibiting common food separation and sedimentation phenomena, significantly extending shelf life. For example, in plant-based beverages, nanoemulsification technology prevents oil from floating or protein from settling, resulting in both excellent stability and a transparent appearance. In sauces, it enhances homogeneity and improves the delicate texture. Many functional food ingredients suffer from poor water solubility or susceptibility to degradation, leading to low absorption efficiency. Nanoemulsions can encapsulate fat-soluble ingredients within an oil core, shielding them from the adverse gastrointestinal environment. Their nanoparticle size also facilitates intestinal absorption, significantly increasing bioavailability. The preparation of nanoemulsions aligns with clean label and green processing trends, meeting modern consumers' demand for healthy, natural foods. It is important to note that the preparation of nanoemulsions often requires the use of nanoparticles as stabilizers. Nanoparticles adsorb at the oil-water interface to form an interfacial film, enhancing system stability and regulating particle size distribution. This characteristic allows for more controllable delivery of functional ingredients. Therefore, with the development of technology, nanoemulsions are expected to develop more innovative applications in the fields of personalized nutrition, smart responsive food, etc., and promote the food industry to move towards high efficiency and functionalization.

[0003] Nanoparticles, as key stabilizers in nanoemulsions, form a dense interfacial film through targeted adsorption at the oil-water interface, effectively reducing interfacial tension and inhibiting droplet coalescence, thereby maintaining the long-term stability of the emulsion system. Although single-component emulsifiers (such as proteins, saponins, and Tween 80) have been widely used in emulsion stabilization, these single ingredients often suffer from limitations such as poor stability and limited functionality. In contrast, composite emulsifier systems integrate the advantages of multiple components, achieving complementary performance and enhanced functionality through synergistic effects.

[0004] As a key plant-based protein, pea protein isolate (PPI) has become a highly promising raw material in the food industry due to its high nutritional value, low allergenicity, cost-effectiveness, and potential health benefits. However, due to its low water solubility, pea protein isolate has a slow adsorption rate at the oil-water interface, resulting in insufficient mechanical strength in the interfacial film. This makes it difficult to meet the stringent requirements of high-performance food-grade emulsions, necessitating technological advancements to enhance its emulsifying properties.

[0005] Tea saponin, a natural glycoside surfactant, can form a dense adsorption layer on the surface of emulsion droplets, effectively inhibiting droplet aggregation and flocculation. It also reduces the frequency of droplet collisions by increasing the viscosity of the system, thereby improving emulsion stability. Furthermore, tea saponin exhibits multiple biological activities, such as antibacterial and anti-inflammatory properties, further expanding its application value. However, the use of tea saponin alone cannot completely solve problems such as insufficient long-term emulsion stability and uneven oil droplet distribution. Studies have shown that protein-saponin complexes can significantly improve emulsification performance and stability. Therefore, exploring methods for preparing nanoemulsions that can be stabilized by the synergistic action of pea protein isolate and tea saponin has important theoretical and practical significance for the development of high-performance, naturally safe, food-grade nanoemulsion products. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing a nanoemulsion, wherein pea protein isolate is modified by tea saponin to form composite nanoparticles with strong emulsification properties, thereby preparing a nanoemulsion with good stability and strong rheological properties, which is of certain significance in encapsulating active substances and achieving antibacterial effects.

[0007] The present invention comprises the following steps: (1) Prepare a pea protein isolate (20 mg / mL) aqueous solution, stir on a magnetic stirrer for 2 h, ensure full dissolution, and then place at 4 °C for 12 h; (2) The pH value was adjusted to 12 using 2 M NaOH under continuous stirring and continued to be stirred for 10 min. The mixture was then ultrasonicated (power 500 W, pulse mode: ultrasonication 5 s, rest 2 s) for 10 min. The pH value was then readjusted to 7.0 using 2 M HCl to obtain the modified pea protein isolate solution. (3) mixing the tea saponin powder with the modified pea protein isolate solution and stirring at room temperature for 2 h to obtain a pea protein isolate-tea saponin composite nanoparticle dispersion; (4) Medium-chain triglycerides were added to the pea protein isolate-tea saponin composite nanoparticle dispersion, homogenized at 11,000 rpm for 2 min, and then ultrasonically treated at 500 W power (pulse mode: ultrasonic 2 s, pause 2 s) for 10 min to obtain pea protein isolate-tea saponin nanoemulsion.

[0008] The present invention also includes the following features: The added amounts of tea saponin in (3) are 1, 5, 10, 15, and 20 mg / ml, respectively; the volume fraction of medium-chain triglycerides added in (4) is 5%; the performance of the pea protein isolate-tea saponin nanoemulsion of the present invention is characterized by particle size, emulsification performance, microstructure, and rheological properties.

[0009] The present invention has the following advantages: (1) The present invention uses pea protein isolate-tea saponin composite nanoparticles to prepare nanoemulsions. The raw materials are all of natural origin, which is consistent with the development trend of clean labels and green foods and meets the demand of modern consumers for healthy and natural foods. (2) The present invention selects medium-chain triglycerides as the oil phase, which have the characteristics of short carbon chain, good water solubility, and strong oxidative stability, which can effectively prevent the oxidative rancidity of oils and fats, ensure that the nanoemulsion can maintain good physical and chemical properties under different storage conditions, further extend the shelf life of the product and improve nutritional stability; (3) The preparation process of the present invention adopts magnetic stirring, ultrasonic treatment, homogenization and isothermal process, which is simple and controllable to operate, has low energy consumption, and is easy to realize industrial large-scale production; (4) The nanoemulsion prepared by the present invention can be used as a delivery system for bioactive substances, providing new ideas for the design of functional foods and having broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Appearance of nanoemulsions prepared from pea protein isolate and tea saponin at different concentrations; Figure 2 The effect of nanoemulsions prepared from pea protein isolate and tea saponin at different concentrations on particle size; Figure 3 Ultra-high resolution microscopy images of nanoemulsions prepared from pea protein isolate and tea saponin at different concentrations; Figure 4 The effect of nanoemulsions prepared from pea protein isolate and tea saponin at different concentrations on emulsion stability; Figure 5 Effect of nanoemulsions prepared from pea protein isolate and tea saponin at different concentrations on viscosity. DETAILED DESCRIPTION

[0011] Example 1 A method for preparing a pea protein isolate-tea saponin nanoemulsion comprises the following steps:

[0012] Step 1: Prepare a pea protein isolate (20 mg / mL) aqueous solution, stir on a magnetic stirrer for 2 h, ensure full dissolution, and then place at 4 °C for 12 h; Step 2: Adjust the pH value to 12 with 2 M NaOH under continuous stirring, continue stirring for 10 min, then perform ultrasonic treatment (power 500 W, pulse mode: ultrasonic 5 s, rest 2 s) for 10 min, and then readjust the pH value to 7.0 with 2 M HCl to obtain the modified pea protein isolate solution; Step 3: Mix the tea saponin powder with the modified pea protein isolate solution to obtain a mixed solution with a tea saponin concentration of 1 mg / ml, and stir at room temperature for 2 h to obtain a pea protein isolate-tea saponin composite nanoparticle dispersion; Step 4: Add 5% by volume of medium-chain triglycerides to the pea protein isolate-tea saponin composite nanoparticle dispersion, homogenize at 11,000 rpm for 2 minutes, and then ultrasonicate at 500 W power (pulse mode: ultrasonicate for 2 seconds, rest for 2 seconds) for 10 minutes to obtain a pea protein isolate-tea saponin nanoemulsion; The average particle size of the emulsion was measured by a laser particle size analyzer and was found to be 367.2 nm. The absorbance of the emulsion was measured by a spectrophotometer, and according to the formula: emulsion stability (%) = (absorbance of the emulsion 30 min after preparation / absorbance of the emulsion just after preparation) × 100, the calculated emulsion stability was 75%. Example 2

[0013] The method described in this example is basically the same as that in Example 1, except that the concentration of tea saponin in the mixed solution in step 3 is 5 mg / mL; The average particle size of the emulsion was measured by a laser particle size analyzer and was found to be 355.6 nm. The absorbance of the emulsion was measured by a spectrophotometer and the calculated emulsion stability was 84.5% according to the formula: emulsion stability (%) = (absorbance of the emulsion 30 min after preparation / absorbance of the emulsion just after preparation) × 100. Example 3

[0014] The method described in this example is basically the same as that in Example 1, except that the concentration of tea saponin in the mixed solution in step 3 is 10 mg / mL; The average particle size of the emulsion was measured by a laser particle size analyzer and was found to be 282.9 nm. The absorbance of the emulsion was measured by a spectrophotometer and the calculated emulsion stability was 86.2% according to the formula: emulsion stability (%) = (absorbance of the emulsion 30 min after preparation / absorbance of the emulsion just after preparation) × 100. Example 4

[0015] The method described in this example is basically the same as that in Example 1, except that the concentration of tea saponin in the mixed solution in step 3 is 15 mg / mL; The average particle size of the emulsion was measured by a laser particle size analyzer and was found to be 305.8 nm. The absorbance of the emulsion was measured by a spectrophotometer and the calculated emulsion stability was 77.3% according to the formula: emulsion stability (%) = (absorbance of the emulsion 30 min after preparation / absorbance of the emulsion just after preparation) × 100. Example 5

[0016] The method described in this example is basically the same as that in Example 1, except that the concentration of tea saponin in the mixed solution in step 3 is 20 mg / mL; The average particle size of the emulsion was measured by a laser particle size analyzer and was found to be 304.5 nm. The absorbance of the emulsion was measured by a spectrophotometer and the calculated emulsion stability was 73.1% according to the formula: emulsion stability (%) = (absorbance of the emulsion 30 min after preparation / absorbance of the emulsion just after preparation) × 100.

[0017] from Figure 1 It can be seen that the nanoemulsions prepared in each example are evenly distributed without stratification or oil precipitation. from Figure 2 It can be seen that with the increase of tea saponin concentration, the particle size of the nanoemulsion showed a trend of first significantly decreasing and then increasing ( P <0.05), when the tea saponin concentration was 10 mg / ml, the emulsion particle size was the smallest; from Figure 3 It can be seen that the nanoemulsion exhibits significantly smaller and well-dispersed spherical droplets. With the increase of tea saponin concentration, the droplet size shows a trend of first decreasing and then increasing. When the tea saponin concentration is 10 mg / ml, the emulsion droplets are the smallest and most evenly distributed. from Figure 4 It can be seen that with the increase of tea saponin concentration, the emulsion stability of the nanoemulsion showed a trend of first significantly increasing and then decreasing. When the tea saponin concentration was 10 mg / ml, the emulsion stability of the nanoemulsion was the highest. The particle fluidity induced by tea saponin modification was reduced, thereby enhancing the stability of the nanoemulsion. from Figure 5 The viscosity of all nanoemulsions gradually decreased with increasing shear rate. Under low shear conditions (0.1-10 s⁻¹), the apparent viscosity dropped rapidly. When 10 mg / ml of tea saponin was added, the pea protein isolate-tea saponin complex formed a dense adsorption layer at the oil-water interface, promoting interaction between droplets and reaching its highest viscosity. Higher viscosity can significantly reduce the frequency of droplet collisions by increasing frictional resistance and steric hindrance between droplets, inhibiting droplet coalescence, flocculation, or demixing, thereby improving the long-term physical stability of the nanoemulsion.

Claims

1. The present invention uses pea protein isolate and tea saponin as raw materials, obtains pea protein isolate-tea saponin composite nanoparticles by mixing tea saponin and modified pea protein isolate solution, uses medium-chain triglycerides as oil phase, and forms nanoemulsion by means of homogenization and ultrasonication.

2. According to claim 1, a method for preparing a pea protein isolate-tea saponin nanoemulsion, characterized by the following steps: (1) Prepare a pea protein isolate (20 mg / mL) aqueous solution, place it on a magnetic stirrer and stir for 2 h. After ensuring it is fully dissolved, place it at 4 °C for 12 h. (2) The pH value was adjusted to 12 using 2 M NaOH under continuous stirring and continued to be stirred for 10 min. The mixture was then ultrasonicated (power 500 W, pulse mode: ultrasonication 5 s, intermittent 2 s) for 10 min. The pH value was then readjusted to 7.0 using 2 M HCl to obtain the modified pea protein isolate solution. (3) Mixing the tea saponin powder with the modified pea protein isolate solution and stirring at room temperature for 2 h to obtain a pea protein isolate-tea saponin composite nanoparticle dispersion; (4) Medium-chain triglycerides were added to the pea protein isolate-tea saponin composite nanoparticle dispersion, homogenized at 11,000 rpm for 2 min, and then ultrasonically treated at 500 W power (pulse mode: ultrasonic 2 s, intermittent 2 s) for 10 min to obtain pea protein isolate-tea saponin nanoemulsion.

3. The method for preparing a pea protein isolate-tea saponin nanoemulsion according to claim 2, wherein: The added amounts of tea saponin in the S3 are 1, 5, 10, 15, and 20 mg / ml, respectively.

4. The method for preparing a pea protein isolate-tea saponin nanoemulsion according to claim 2, wherein: The volume fraction of medium-chain triglycerides added to S4 is 5%.

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