A method for preparing a low-fat Pickering emulsion gel and its application

Abstract

This invention discloses a method for preparing a low-fat Pickering-type emulsion gel, comprising the following steps: 1) mixing egg yolk particles and chitosan with water at a mass ratio of 1:0.5-1 and adjusting the pH of the solution to 3-6, then adding 0.2-0.5 M NaCl; 2) adding edible oil, making the edible oil account for 20-40% of the total mass of the mixture, and then subjecting the mixture to high-speed shearing to achieve a homogeneous and stable emulsion gel state. The low-fat Pickering-type emulsion gel prepared by this invention has excellent emulsifying properties, gelling characteristics, and stability, and has great application prospects in the production of emulsion foods, especially mayonnaise.

Description

Technical Field

[0001] This invention relates to the field of egg product technology, specifically to a method for preparing low-fat Pickering emulsion gel using egg yolk particles and its application in mayonnaise. Background Technology

[0002] Egg yolk pellets are the precipitate after extracting immunoglobulins from egg yolks. Each ton of egg yolk produces approximately 250 kg of egg yolk pellets, making them a major byproduct of the egg yolk processing industry. Compared to whole egg yolks, egg yolk pellets have a higher protein content (63.8%) and lower lipid (30.7%) and cholesterol (1.3%) content. Furthermore, egg yolk pellets form a dense, spherical structure with a diameter between 0.3 and 2.0 μm, connected by calcium phosphate bridges. When used in emulsification systems, they can effectively act as a Pickering-type emulsifier to stabilize the oil-water interface. Due to their poor solubility and emulsification properties, egg yolk pellets are currently mainly used as animal feed. However, their abundant amphiphilic proteins possess emulsifying properties, suggesting potential applications in the production of emulsion foods.

[0003] Emulsion gels are emulsions with a gel network structure and solid mechanical properties, and have wide applications in the food industry, such as mayonnaise and cheese. Emulsion gels are generally prepared based on high internal phase emulsions (oil phase ratio > 74%). However, excessive fat addition increases the risk of obesity and coronary heart disease. Current strategies for preparing low-fat emulsion gels focus on two aspects: one is to enhance the interaction between oil droplets and the continuous phase through cross-linking, thereby increasing the viscosity and stability of the emulsion gel; the other is to regulate the viscosity of the emulsion through the thickening effect of polysaccharides to simulate the rheology of high internal phase emulsion gels. CN 116369499 A uses a solvent removal method combined with thermal crosslinking aggregation to prepare low-oil-phase Pickering emulsion gels, which easily leads to organic reagent residues; CN 112890165 A uses thermal crosslinking and enzymatic crosslinking to prepare plant protein-based Pickering emulsion gels. Due to the excessive degree of protein crosslinking, high-speed shearing and high-pressure homogenization steps are added, resulting in high production costs and making it unsuitable for industrial production; CN 112826069 A prepares low-fat emulsion gels through the simple thickening effect of tea polysaccharides and xanthan gum. Although it achieves the texture of high internal phase emulsion gels, the amount of polysaccharides added is too large and the stability is poor.

[0004] Therefore, this invention regulates the aggregation behavior of egg yolk particles by adjusting pH and ionic strength, and enhances their interaction with oil droplets. It employs a non-thermal, one-step method to prepare a low-fat Pickering-type emulsion gel stabilized by egg yolk particle / chitosan composite particles. This invention also solves the problem of high-value utilization of waste egg yolk particles. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a low-fat Pickering emulsion gel and its application in mayonnaise, aiming to solve the problems of poor rheological properties, texture, and stability of low-fat emulsion gels, and poor emulsification properties of natural egg yolk particles. This invention uses egg yolk particles as raw material, adjusts pH and ionic strength, and utilizes the synergistic effect of chitosan to prepare a type of low-fat Pickering emulsion gel with high gelation properties and stability.

[0006] To achieve the above objectives, the applicant first investigated the effects of different pH and ionic strength on the aggregation behavior of egg yolk particles. It was found that when the pH was between 4 and 6 and the ionic strength (i.e., NaCl content) was between 0.2 and 0.4 M, the egg yolk particles aggregated well. During the protein aggregation process, lipids were precipitated, which was beneficial for the formation of Pickering emulsions and improved the texture properties of the emulsions.

[0007] Next, the applicant further investigated the effects of different pH and ionic strength on the emulsification performance of egg yolk particles. It was found that when the oil phase ratio was 30%, the egg yolk particles treated with different pH and ionic strengths all had a certain emulsification ability. Among them, the emulsion prepared from egg yolk particles with pH 4-6 and ionic strength 0.2-0.4M had certain gel properties but low emulsification performance.

[0008] In order to reduce the oil content and obtain a Pickering emulsion gel with good gel state and emulsification, the applicant further investigated the types of polysaccharides and found that the egg yolk particle-chitosan complex system formed by adding chitosan can improve emulsification. The resulting low-fat (30% oil) Pickering emulsion not only has a self-supporting structure of gel, but also has a good emulsification effect.

[0009] Finally, the applicant further screened and optimized the ratio of egg yolk particles to chitosan composite system and the oil ratio, and finally completed the invention.

[0010] Verification has shown that the low-fat Pickering emulsion gel prepared by this invention has excellent emulsifying properties, gelling characteristics, and stability, and has great application prospects in the production of emulsion foods, especially mayonnaise.

[0011] A more detailed technical solution is as follows:

[0012] A method for preparing a low-fat Pickering emulsion gel includes the following steps:

[0013] 1) Mix egg yolk granules and chitosan with water at a mass ratio of 1:0.5-1 and adjust the pH of the solution to 3-6. Add NaCl to a final concentration of 0.2-0.5 M.

[0014] 2) Add edible oil to the solution in step 1) so that the edible oil accounts for 20-40% of the total mass of the mixture. Then perform high-speed shearing at a speed of 10,000-20,000 rpm for 1-2 minutes to make the mixture form a uniform and stable emulsion gel state, thus obtaining a low-fat Pickering type emulsion gel.

[0015] Preferably, the egg yolk particles are obtained by removing the membrane from the egg yolk, collecting the yolk liquid, diluting it with 0.1-0.2M NaCl solution, stirring, centrifuging, collecting the precipitate, and freeze-drying. The resulting product is the egg yolk particles.

[0016] Preferably, the edible oil is one or a combination of soybean oil, peanut oil, and sunflower seed oil.

[0017] Preferably, the mass ratio of egg yolk particles to chitosan is 2:1, the pH of the solution is 4.0, and the final concentration of NaCl is 0.3 M.

[0018] Preferably, the edible oil accounts for 30% of the total mass of the mixture.

[0019] According to a specific embodiment of the present invention, an optimal method for preparing a low-fat Pickering emulsion gel is as follows: freeze-dried egg yolk particles and chitosan are mixed with water at a mass ratio of 2:1 to prepare a mixed solution with an egg yolk particle content of 10 wt%. The pH of the solution is then adjusted to 4.0, and salt with a final concentration of 0.3 M is added. Edible oil is then added to the solution, making the edible oil account for 30% of the total mass of the mixed system. High-speed shearing is then performed at a shearing speed of 10,000-20,000 rpm for 1-2 min, so that the mixed system presents a uniform and stable emulsion gel state, thus obtaining a low-fat Pickering emulsion gel.

[0020] The present invention further provides a mayonnaise containing a low-fat Pickering emulsion gel prepared according to the above method.

[0021] Furthermore, the mayonnaise also contains curcumin, sugar, and spices.

[0022] The present invention further provides a method for making the mayonnaise, comprising the following steps:

[0023] 1) Mix egg yolk granules and chitosan with water at a mass ratio of 1:0.5-1 and adjust the pH of the solution to 3-6. Add NaCl to a final concentration of 0.2-0.5 M.

[0024] 2) Add edible oil containing curcumin to the solution in step 1), so that the edible oil accounts for 20-40% of the total mass of the mixture. Then add sugar and spices and perform high-speed shearing at a speed of 10,000-20,000 rpm for 1-2 minutes to make the mixture form a uniform and stable emulsion gel state, thus obtaining mayonnaise.

[0025] Preferably, the curcumin accounts for 0.05-0.1% of the mass of the edible oil.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The low-fat Pickering emulsion gel prepared by the present invention achieves the technical effect of reducing the oil content in the emulsion gel to 20-40%; and relies on Pickering emulsifier to stabilize the emulsion, this low-fat Pickering emulsion gel has good thermal stability, centrifugal stability and freeze-thaw stability.

[0028] (2) The present invention regulates the aggregation behavior of egg yolk particles by pH and ionic strength to form aggregated particles with rigid structure, making it easier for oil droplets to be captured during the homogenization process, thereby forming a three-dimensional gel network structure; in addition, the electrostatic repulsion of chitosan and the steric hindrance of chitosan sugar side chains form a composite system with a relaxed structure, which improves the emulsification of low-fat Pickering emulsion gel.

[0029] (3) The egg yolk particles used in this invention can realize the high-value utilization of by-products and open up new applications for egg yolk particles in the food field. In addition, the cholesterol content in egg yolk particles is reduced by 50% compared with whole egg yolks, and the egg yolk particle preparation process provided is simple and suitable for large-scale production.

[0030] (4) Curcumin is used instead of preservatives and pigments. The low-fat mayonnaise prepared has strong antioxidant properties, is more green and healthy, and conforms to the modern food health concept of reducing additives.

[0031] (5) The present invention uses a non-thermal processing, one-step homogenization method to prepare low-fat Pickering emulsion gel, which is convenient to operate, low in cost, and suitable for industrial production. Attached Figure Description

[0032] Figure 1 CLSM images of egg yolk particle solutions (10 wt.%) at different pH and ionic strengths. Green areas represent proteins stained with FITC, and red areas represent lipids stained with Nile Red.

[0033] Figure 2Appearance and microscopic images of emulsions stabilized by egg yolk particles at different pH and ionic strengths, with an oil phase ratio of 30%.

[0034] Figure 3 Self-supporting structure, microscopic images, and oil droplet size distribution of emulsions stabilized by egg yolk particles under different oil phase ratios.

[0035] Figure 4 Appearance, micrograph, and oil droplet size distribution of emulsions containing different polysaccharides and egg yolk particles, with an oil phase ratio of 30%.

[0036] Figure 5 Appearance (A) and CLSM diagram (B) of low-fat Pickering emulsion gels with different oil phase ratios.

[0037] Figure 6 Storage modulus G' (A) and loss modulus G'' (B) of low-fat Pickering emulsion gels with different oil content ratios and Comparative Example 1 in frequency scanning tests. Apparent viscosity as a function of shear rate for low-fat Pickering emulsion gels with the same oil content ratio and Comparative Example 1 (C). Power-law parameters of low-fat Pickering emulsion gels with the same oil content ratio and Comparative Example 1 (D).

[0038] Figure 7 Hardness and penetrability of low-fat Pickering emulsion gels with different oil content ratios and Comparative Example 1.

[0039] Figure 8 Textural properties of low-fat Pickering emulsion gels and high internal phase emulsion gels before and after heating under different oil ratios; where Figure a represents hardness and Figure b represents penetration power.

[0040] Figure 9 Average droplet size of low-fat Pickering emulsion gel and high internal phase emulsion gel before and after heating under different oil ratios.

[0041] Figure 10 Appearance and average droplet size of low-fat Pickering emulsion gel and high internal phase emulsion gel before and after freeze-thaw at different oil ratios.

[0042] Figure 11 Low-fat Pickering emulsion gels with 30% oil content, with and without curcumin, were tested for malondialdehyde content every 5 days over 30 days of storage.

[0043] Figure 12 Comparison of the state of 30% oil-based mayonnaise and commercially available mayonnaise. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Example 1: Egg yolk particle aggregation behavior and emulsification regulation strategies

[0046] 1. Regulation of yolk particle aggregation behavior

[0047] Low-fat Pickering emulsion gels are stabilized by the aggregation of egg yolk particles. Therefore, the aggregation behavior of egg yolk particles under different pH and ionic strengths was first observed to determine the appropriate range.

[0048] After separating the egg white and yolk, the separated yolk was placed on filter paper and gently rolled to absorb the egg white adhering to the yolk membrane. The yolk membrane was punctured with tweezers to collect the yolk liquid in a beaker, diluted with 0.15 M NaCl (1:1 v / v), magnetically stirred for 30 min, and then centrifuged (10000g, 4℃, 45 min). The supernatant after centrifugation was used to extract egg yolk immunoglobulins. The precipitate was collected and freeze-dried to obtain egg yolk particles. The egg yolk particles were dissolved in water at a ratio of 10 wt%, and the pH of the solution was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, respectively. A batch of unadjusted egg yolk particle solutions was taken, and NaCl was added to final concentrations of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 M, respectively. Analysis was performed using zeta potential, particle size, and laser confocal microscopy.

[0049] The particle size and zeta potential of egg yolk particles were analyzed using a Nano-ZS zeta potential analyzer. Average particle size effectively reflects the degree of aggregation and dissociation of egg yolk particles. As shown in Table 1, the particle size was largest at pH 4.0 and 0.2 M. From the zeta potential data, at pH 4.0, close to the isoelectric point of the egg yolk particles, the electrostatic interaction between particles is weakest, leading to particle aggregation. The zeta potential of natural egg yolk particles is -14.87 mV. The addition of salt ions causes electrostatic neutralization, shifting the zeta potential towards 0, resulting in particle aggregation. With further increases in salt ions, more Ca from the calcium phosphate bridge is displaced. 2+ Ions cause particle disintegration and a reduction in particle size. Therefore, when the pH is between 3.0 and 8.0 and the ionic strength is between 0.2 and 0.4 M, the egg yolk particles aggregate better, thereby improving the textural properties of the emulsion.

[0050] Table 1. Average particle size and zeta potential of egg yolk particle solutions under different pH and ionic strengths.

[0051]

[0052] To further observe the aggregation behavior of egg yolk particles, proteins and lipids in the particles were stained with fluorescein isothiocyanate (FITC) and Nile red, respectively, and then observed using a laser confocal microscope. FITC and Nile red were dissolved in ethanol (1 mg / mL), and the prepared dyes were stored in the dark. Egg yolk particle emulsions with different pH and ionic strengths were stained with 10 μL of FITC and 100 μL of Nile red. 10 μL of the stained sample was placed in the center of a glass slide, covered with a coverslip, taking care to prevent air bubbles. Observation was performed under a 100x microscope. The incident light emission wavelength was 633 nm.

[0053] like Figure 1 As shown, significant aggregation of egg yolk particles was observed in samples at pH 4, pH 6, and 0.2 M, consistent with the changes in particle size. Furthermore, the aggregates of egg yolk particles were surrounded by red oil droplets, indicating that lipid precipitation occurred alongside protein aggregation. Due to their similar polarity, the lipids precipitated from the egg yolk particles more readily bind to edible oils, which is beneficial for the formation of Pickering emulsions.

[0054] 2. Emulsifying properties of egg yolk particles

[0055] The emulsification behavior of egg yolk particles under different aggregation states was further investigated, and it was also examined whether egg yolk particle emulsions could form a gel self-supporting structure under different oil phase ratios.

[0056] Egg yolk particle solutions at different pH and ionic strengths were taken, and edible oil was added to make the oil phase ratio in the final emulsion 30%. Separately, natural egg yolk particle solutions were taken, and the pH was adjusted to 4.0. 0.3M NaCl was added, and different amounts of vegetable oil (30%, 50%, 70%) were added to prepare emulsions with different oil contents. These emulsions with different pH, ionic strengths, and oil phase ratios were prepared using a high-speed shear disperser at a shear rate of 10000 rpm for 2 minutes. The prepared egg yolk particle emulsions were analyzed by observing their appearance and microscopic observation.

[0057] like Figure 2 As shown, at pH 4-6, the emulsion formed by the good aggregation of egg yolk particles has a larger particle size and a certain degree of gelation. However, obvious stratification occurs at the bottom of the egg yolk particle emulsion, and its emulsifying properties are not as good as those at pH 8-12. To obtain an emulsion gel with better gelation and emulsifying properties, the emulsifying performance of egg yolk particles at pH 4-6 needs to be further improved. With increasing ionic strength, the emulsifying performance of the emulsion gradually increases. Egg yolk particle emulsions at ionic strengths of 0.2-0.4M also require further improvement in their emulsifying properties.

[0058] like Figure 3 As shown, when the bottle is inverted, the emulsion with 70% oil content can adhere to the bottom of the glass bottle, exhibiting a self-supporting emulsion gel structure, indicating that the viscosity of the emulsion increases with increasing oil content. Microscopic observation of the emulsion's microstructure reveals that the droplet size gradually decreases with increasing oil content. When the oil content is 70%, the average droplet diameter is 4.53 μm, indicating that the self-supporting structure in the emulsion benefits from the thickening effect of oil droplet accumulation. However, in the emulsion with a 30% oil content, the oil droplet accumulation effect is lost, and the average droplet diameter is 10.02 μm. This suggests that egg yolk particles have the potential to prepare emulsion gels at pH 4-6 and an ionic strength of 0.2-0.4 M, but due to insufficient emulsifying ability, further improvements in the emulsifying properties and viscosity of the 30% oil content emulsion are needed.

[0059] 3. The effect of polysaccharide type on emulsion gel formation

[0060] Protein-polysaccharide complexes often exhibit better emulsifying properties and a thickening effect than proteins or polysaccharides alone, which is beneficial for the construction of low-fat Pickering emulsion gels. This study investigated the effects of different polysaccharide types (carboxymethyl cellulose, konjac puganan, alginate, gum arabic, pectin, carrageenan, and chitosan) on emulsion gel formation in order to screen out suitable polysaccharide types for low-fat Pickering emulsion gels.

[0061] Freeze-dried egg yolk particles were mixed with different polysaccharides (carboxymethyl cellulose, konjac pumaranth, alginate, gum arabic, pectin, carrageenan, and chitosan) in water at a ratio of 2:1 (w:w), so that the egg yolk particle content in the water was 10 wt%. The pH of the mixture was adjusted to 4.0, and salt was added to make the ionic strength of the system 0.3 M. Then, the egg yolk particle-chitosan composite solution was mixed evenly with 30% vegetable oil to prepare a low-fat emulsion. A high-speed shear disperser was used at a shear rate of 10,000 rpm for 2 min to prepare a low-fat emulsion. The prepared low-fat emulsion was analyzed by observing its self-supporting structure by inversion, microscopic observation, and oil droplet size. The results are shown in the figure. Figure 4 .

[0062] Comparing the stability of emulsions formed by different polysaccharides with egg yolk particles, it was found that carboxymethyl cellulose, konjac pulglucan, alginate, and chitosan could form a self-supporting gel structure, while gum arabic, pectin, and carrageenan remained in an emulsion state at a 30% oil content. However, the gels formed by carboxymethyl cellulose, konjac pulglucan, and alginate, as observed, exhibited significant oil-water separation due to the gelation effect of the polysaccharides, resulting in uneven emulsification after the addition of oil. Particle size distribution analysis revealed that the emulsion droplets in the gel structures formed by these three polysaccharides were relatively large, while the emulsion gel formed by chitosan not only emulsified uniformly but also had a particle size of 4.12 μm, exhibiting a strong emulsifying structure. Therefore, as the only cationic polysaccharide found in nature, chitosan is an excellent material for forming a stable system with egg yolk particles and preparing low-fat Pickering-type emulsion gels.

[0063] 4. Construction of the egg yolk particle-chitosan complex system

[0064] The ratio of egg yolk particles to chitosan and pH are key factors affecting the emulsification of the system and are prerequisites for the strong stability of low-fat Pickering emulsion gels. Therefore, based on the changing behavior of egg yolk particle aggregation, this study investigated the effects of different egg yolk particle / chitosan ratios (1:2, 1:1, 2:1, 4:1) and different pH values ​​(3.0-8.0) on the emulsification of the composite system.

[0065] Freeze-dried egg yolk particles were taken and dissolved in water with chitosan at different ratios (1:2, 1:1, 2:1, 4:1) to achieve a 10% concentration of egg yolk particles in the solution. Separately, an egg yolk particle / chitosan composite solution with a 10% concentration (ratio 2:1) was prepared, and the pH of the solution was adjusted to prepare composite solutions with different pH values ​​(3.0, 4.0, 5.0, 6.0, 7.0, 8.0). 30% vegetable oil was added to the composite solutions, and the mixture was sheared at 10000 rpm for 2 min. Then, at 0 min and 30 min, 20 μL of the emulsion was aspirated from the bottom and added to 8 mL of 0.1% (w / v) SDS solution. After vortexing for 10 s, the absorbance was measured at 500 nm. An SDS solution of the same concentration was used as a blank control group. The emulsifying activity EA was expressed as the absorbance A0 at 0 min, calculated using the following formula:

[0066]

[0067] In the formula: EA represents emulsifying activity; ES represents emulsifying stability; ∆T represents the time interval, which is 30 min; A0 represents the absorbance at 0 min; and A30 represents the absorbance at 30 min.

[0068] Emulsifying activity refers to the area of ​​the oil-water interface that a unit mass of emulsifier can stabilize when forming an emulsion in a homogeneous oil-water mixture. Emulsifying stability refers to the ability of an emulsifier to stabilize the oil-water interface against external changes. As shown in Table 2, with the continuous decrease of the chitosan content, the emulsifying activity of the egg yolk particle-chitosan composite system showed a trend of first increasing and then decreasing, reaching its maximum value at an egg yolk particle / chitosan ratio of 2:1. The trend of emulsifying stability was the same as that of emulsifying activity. The table shows that the emulsifying activity and emulsifying stability of the composite system at pH 3.0, pH 4.0, and pH 5.0 were significantly higher than those at pH 6.0, pH 7.0, and pH 8.0. This may be because different pH values ​​alter the structure, surface charge, and interactions of the composite system, thereby affecting its adsorption behavior at the oil-water interface. The results showed that when the ratio of egg yolk particles to chitosan was 1:1-2:1 (i.e. 1:0.5-1), the composite system had strong emulsifying activity and emulsifying stability at pH 3.0-5.0.

[0069] Table 2. Emulsifying activity and emulsifying stability of egg yolk particles-chitosan at different ratios and pH levels.

[0070]

[0071] Example 2: Construction of an egg yolk particle-chitosan emulsion gel structure with low fat content

[0072] Freeze-dried egg yolk particles and chitosan were mixed in water at a ratio of 2:1 (w:w) to achieve an egg yolk particle content of 10 wt%. The pH of the mixture was adjusted to 4.0, and salt was added to achieve an ionic strength of 0.3 M. The egg yolk particle-chitosan composite solution was then mixed with different amounts (0%, 10%, 20%, 30%, 40%, 50%) of vegetable oil to prepare emulsions with varying oil contents. Low-fat Pickering emulsion gels with different oil contents were prepared by using a high-speed shear disperser at a shear rate of 10,000 rpm for 2 min.

[0073] Comparative Example 1

[0074] A high internal phase emulsion gel with a 75% oil phase ratio was constructed as a comparison. The specific preparation method was as follows: freeze-dried egg yolk particles were dissolved in water to make the content of egg yolk particles in the water 10 wt%. Then, 75% vegetable oil was added to the egg yolk particle solution, and a high-speed shear disperser was used to shear at a shear rate of 10000 rpm for 2 min to prepare a high internal phase emulsion gel with a 75% oil content.

[0075] 1. Apparent and microstructure

[0076] To more intuitively describe the morphology of egg yolk particles and oil droplets in the mixture, a laser confocal microscope was used to observe the samples. The method was the same as above.

[0077] like Figure 5 As shown, the self-supporting structure of the emulsion significantly improves with increasing oil content. However, when the oil content reaches 50%, water-oil phase separation occurs. CLSM was used to study the emulsion morphology, with proteins and oil represented in green and red, respectively. With the addition of oil, in addition to the oil from the egg yolk particles themselves, oil droplet distribution is clearly visible. At an oil content of 10%-30%, the oil droplets are small and uniform, while with further increases in oil content, some large oil droplets appear, and the droplets gradually aggregate, resulting in poorer emulsification. Therefore, at an oil content of 10-30%, the egg yolk particle-chitosan emulsifies the oil droplets effectively.

[0078] 2. Rheology

[0079] The storage modulus (G') and loss modulus (G") of the emulsion gel were tested using an AR2000ex rheometer. The plates used for measurement were 40 mm parallel plates with a gap of 1.0 mm. The oscillatory strain ranged from 0.01% to 100% at a frequency of 1 Hz. The frequency range was from 0.1 Hz to 10 Hz.

[0080] like Figure 6 As shown in A and B, the G' and G" values ​​of all samples increased with frequency from 0.1 Hz to 10 Hz, and the G' value for the same oil phase was greater than the G" value, indicating that all samples were weak gel structures with predominantly elastic characteristics, exhibiting solid-like behavior in the linear viscoelastic region. With increasing oil content, the G' and G" values ​​of the low-fat Pickering emulsion gel gradually increased, indicating a gradually strengthening internal gel structure. When the oil content was 50%, it exceeded the emulsified oil content of the egg yolk particles-chitosan, resulting in oil-water separation and the absence of a gel structure, thus exhibiting the lowest G' and G" values. Furthermore, when the oil content was 30% and 40%, the frequency scanning results of the low-fat Pickering emulsion gel were closest to those of the high internal phase emulsion.

[0081] To compare the changes in shear viscosity of low-fat Pickering emulsion gels with different oil contents, at 1 s... -1 -100 s -1 The apparent viscosity of the sample after 10 min of equilibrium was recorded as a function of the shear rate.

[0082] like Figure 6As shown in Figure C, similar to high internal phase emulsion gels, low-fat Pickering emulsion gels also exhibit shear thinning. This is likely due to the interaction of small particles within the emulsion gel and the disruption of tightly packed oil droplets by shear stress at high shear rates. Furthermore, the viscosity of the emulsion gel gradually increases with increasing oil phase ratio. In summary, when the oil phase ratio is 30% or 40%, low-fat Pickering emulsion gels and high internal phase emulsion gels have similar shear viscosities.

[0083] Figure 6 Figure D shows the emulsion flow curves with consistency coefficient (K) and flow index (n) obtained by fitting a power-law model. As the oil content increases from 0% to 40%, the K value of the emulsion increases from 38.11 Pa·s. to 121.76 Pa·s., while the n value decreases from 0.32 to 0.18. However, when the oil content reaches 50%, the K and n values ​​become 16.75 Pa·s. and 0.26, respectively. A higher K value indicates greater flow resistance in the sample, possibly due to the shortened distance between oil droplets, allowing them to interact and form a network. However, with the accumulation of oil droplets, the emulsion breaks down, causing a sharp decrease in the K value (at 50%). The flow index n represents the shear-thinning property, indicating the degree to which the emulsion resists breakdown as the shear rate increases. At all oil contents, the n value is less than 0.34, indicating that the emulsion exhibits shear-thinning properties. In summary, the results indicate that the K and n values ​​exhibited by oil fractions of 30%-40% are similar to those of high internal phase emulsion gels.

[0084] 3. Texture properties

[0085] The sample was placed in a 10 mL beaker and allowed to stand for 20 min. Then, a texture analyzer (TPA) was used for measurement. A cylindrical flat-head probe (model P / 0.5) was selected. The test speed was 1 mm / s, the penetration distance was 10 mm, and the sensing force was automatically set to 10 g. Hardness and penetration force were used as the measurement indicators. Hardness represents the maximum force during the initial compression process, while penetration force measures the force required for the first significant penetration.

[0086] When the oil phase content is 50%, the texture has deviated from a semi-solid state, making it impossible to measure. For example... Figure 7As shown, when the oil phase ratio increases from 0% to 40%, the hardness and penetrability of the low-fat Pickering emulsion gel significantly improve. This is likely because with the increased oil phase ratio, more oil droplets combine with proteins, resulting in a more robust network structure and a more stable oil-water interface. When the oil phase ratio is 30%, the low-fat Pickering emulsion gel exhibits similar textural parameters to high-internal-phase emulsion gels, indicating that the egg yolk particle-chitosan system can compensate for the textural loss caused by the reduction in oil content and can be used in low-fat emulsion gel foods.

[0087] Example 3: Stability test of low-fat Pickering emulsion gel

[0088] The low-fat Pickering emulsion gel prepared above and Comparative Example 1 were tested for thermal stability, centrifugal stability, storage stability and freeze-thaw stability, and the results are shown below.

[0089] 1. Thermal stability

[0090] The thermal stability of the prepared low-fat Pickering emulsion gel was compared with that of Comparative Example 1. The sample was heated in water at 70 °C for 30 min, followed by an ice bath at room temperature. Heating causes protein denaturation and alters the texture of the emulsion gel; therefore, changes in the texture properties of the emulsion gel before and after heat treatment were measured. The methods for determining the texture before and after heating were the same as described above.

[0091] like Figure 8 As shown, except for the 0%-10% group, the hardness and penetration of the other groups after heating are consistent with those of the high internal phase emulsion gel. This may be because the emulsion gel has a strong gel structure inside, which can resist the textural changes caused by heating. Compared with the high internal phase emulsion gel, the low-fat Pickering type emulsion gel of this product has better thermal stability.

[0092] 2. Centrifugal stability test

[0093] Emulsion foods may experience separation and stratification during transportation due to excessively high transport speeds. Therefore, to assess the stability of this product during transportation, the changes in particle size and particle size distribution were measured after centrifugation at 4000 g for 30 min.

[0094] like Figure 9As shown, there was no significant difference in the average particle size of the emulsion gel before and after centrifugation, indicating that the low-fat Pickering emulsion gel has good centrifugal stability. The emulsion gel remained stable even under high-speed centrifugation, which may be related to the internal structure of the egg yolk particles-chitosan. Studies have shown that the interaction between proteins and polysaccharides can confer better stability to the emulsion system. Furthermore, the groups with an oil content of 30% and 40% showed the smallest particle size change, exhibiting a stable state. Compared to the other groups, the 30% and 40% groups showed better stability, indicating that the emulsion in this system can remain stable during transportation.

[0095] 3. Freeze-thaw stability test

[0096] The stability of low-fat Pickering emulsion gels and high internal phase emulsion gels was evaluated after three freeze-thaw cycles at -20 °C, and the product appearance and stratification were observed.

[0097] like Figure 10 As shown in Figure A, the emulsion gels with an oil phase ratio of 0%-30% did not exhibit stratification after three freeze-thaw cycles, demonstrating good stability. The emulsion gels with an oil phase ratio of 40-50% and Comparative Example 1 showed oil separation after three freeze-thaw cycles, losing their original gel structure. During freezing, ice and oil crystallization occur. Large ice crystals can damage the internal structure of the emulsion gel, reducing its emulsifying ability. If the oil content is high, the structure after freeze-thaw cycles cannot emulsify more oil, resulting in some oil leaching out and stratification, causing the emulsion gel to lose its original semi-solid state. Therefore, the low-fat Pickering emulsion gel with a 30% oil content can resist the mechanical damage caused by freeze-thaw treatment. Figure 10 B measured the particle size change after three freeze-thaw cycles. The average particle size of the low-fat Pickering emulsion gel remained below 10 μm at oil ratios of 10-40%. The average particle size change was minimal at 30%-40% oil content, indicating that it can resist mechanical damage caused by ice crystals under low-temperature conditions. The results show that the low-fat Pickering emulsion gel of this product can be cryopreserved to extend its shelf life without altering its structure.

[0098] 4. Storage stability test

[0099] Comparative Example 2: To investigate the effect of curcumin addition on the antioxidant properties of low-fat Pickering emulsion gel, low-fat Pickering emulsion gels with a 30% oil phase ratio were prepared with and without curcumin. Specifically, curcumin was dissolved in soybean oil and magnetically stirred at 500 rpm for 12 hours at room temperature to ensure complete dissolution. Then, an egg yolk particle-chitosan composite solution (pH 4.0, ionic strength 0.3M) was mixed evenly with 30% of the added vegetable oil. The mixture was then sheared at 10,000 rpm for 1 minute using a high-speed shear disperser to prepare a low-fat Pickering emulsion gel containing curcumin. Both the 30% low-fat Pickering emulsion gel and Comparative Example 2 were stored at 4°C. The malondialdehyde (MDA) content in the products was measured every 5 days to observe the storage stability over 30 days.

[0100] like Figure 11 As shown, throughout the experiment, the malondialdehyde (MDA) content of the low-fat Pickering emulsion gel without curcumin increased at a relatively high rate; the growth rate of the low-fat Pickering emulsion gel with curcumin was slower from 0-10 days, but increased from 10-30 days. Figure 11 It can be clearly observed that the rate of fat oxidation is significantly reduced after curcumin is added to the system. This indicates that adding curcumin to the emulsion gel system can increase the shelf life of the food system while introducing nutritional factors.

[0101] Example 4: Making mayonnaise using low-fat Pickering emulsion gel

[0102] Freeze-dried egg yolk particles and chitosan were mixed in water at a ratio of 2:1 (w:w) to achieve an egg yolk particle content of 10 wt.%. The pH of the mixture was adjusted to 4.0, and salt was added to achieve an ionic strength of 0.3 M. Curcumin was dissolved in vegetable oil at a dosage of 0.07 wt.% and magnetically stirred at 500 rpm for 12 h at room temperature to ensure complete dissolution. The egg yolk particle-chitosan composite solution was then mixed evenly with 30% of the added oil phase, and sugar and spices were added for flavoring. The mixture was then sheared at 10,000 rpm for 1 min using a high-speed shear disperser to prepare mayonnaise.

[0103] Example 1: The state of the mayonnaise prepared in Example 4 of this invention and commercially available Kewpie mayonnaise were compared. The results are shown in the figure. Figure 12 .

[0104] from Figure 12It can be seen that the mayonnaise prepared based on the low-fat Pickering type emulsion gel of the present invention has the same extrudability and plasticity as commercially available mayonnaise, and has the potential to be used as a low-fat mayonnaise.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a low-fat Pickering emulsion gel, characterized in that... Includes the following steps: Freeze-dried egg yolk particles and chitosan were mixed with water at a 2:1 mass ratio to prepare a mixed solution with an egg yolk particle content of 10 wt%. The pH of the solution was then adjusted to 4.0, and 0.3 M sodium chloride was added. Edible oil was then added to the solution, making it 30% of the total mass of the mixture. The mixture was then subjected to high-speed shearing at 10,000-20,000 rpm for 1-2 minutes to produce a homogeneous and stable emulsion gel state, thus obtaining a low-fat Pickering emulsion gel. The egg yolk particles are obtained by removing the membrane from egg yolks, collecting the yolk liquid, diluting it with 0.1-0.2 M NaCl solution, stirring, centrifuging, collecting the precipitate, and freeze-drying.

2. The method for preparing the low-fat Pickering emulsion gel according to claim 1, characterized in that: The edible oil is one or a combination of soybean oil, peanut oil, and sunflower seed oil.

3. The application of the low-fat Pickering emulsion gel prepared according to claim 1 or 2 in the production of mayonnaise.

4. A mayonnaise, characterized in that: The mayonnaise contains a low-fat Pickering emulsion gel prepared according to claim 1 or 2.

5. The mayonnaise according to claim 4, characterized in that: The mayonnaise also contains curcumin, sugar, and spices.

6. A method for producing the mayonnaise of claim 5, characterized in that... Includes the following steps: Freeze-dried egg yolk particles and chitosan were mixed with water at a mass ratio of 2:1 to prepare a mixed solution with an egg yolk particle content of 10 wt%. The pH of the solution was then adjusted to 4.0, and salt with a final concentration of 0.3 M was added. Edible oil containing curcumin was then added to the solution, making the edible oil account for 30% of the total mass of the mixed system. Sugar and spices were then added, and the mixture was subjected to high-speed shearing at a speed of 10,000-20,000 rpm for 1-2 minutes to make the mixed system form a homogeneous and stable emulsion gel state, thus obtaining mayonnaise.

7. The method for preparing mayonnaise according to claim 6, characterized in that: The curcumin accounts for 0.05-0.1% of the mass of the edible oil.

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