A method for preparing stable emulsion foam based on Pickering effect of lipid droplet particles in cooperation with glycyrrhizic acid

Abstract

This invention discloses a method for preparing stable emulsion foam based on the Pickering effect of lipid droplets in synergy with glycyrrhizic acid, belonging to the field of food technology. This invention stabilizes lipid droplets using soybean protein isolate gel particles and utilizes the Pickering effect of the lipid droplets and the synergy of glycyrrhizic acid to construct a dense gas-liquid interface film and a three-dimensional network of bulk phase, forming a plant-based emulsion foam system with good plasticity, excellent storage stability, and reduced oil precipitation, along with its preparation process.

Description

Technical Field

[0001] This invention relates to a method for preparing stable emulsion foam based on the Pickering effect of lipid droplets in synergy with glycyrrhizic acid, belonging to the field of food technology. Background Technology

[0002] As an oil / water emulsion system, the whipping ability, fluffiness, and smoothness of butter directly determine the sensory quality of products such as ice cream, cake decorating, desserts, and mousses. Currently, commercially available animal butter is relatively expensive and contains high levels of cholesterol; excessive intake can increase cardiovascular and other health risks. Vegetable butter, on the other hand, mainly uses hydrogenated vegetable oil as its primary fat source and contains more trans fatty acids; long-term consumption may induce various chronic diseases and accelerate aging.

[0003] During the whipping of butter, a large amount of air is incorporated to form emulsion foam. The stability of this foam system directly depends on the oil phase dispersion state, interfacial film composition, bubble size distribution, and interactions between components. Traditional butter emulsion foam uses anhydrous butter as the fat source. After adding emulsifiers, it undergoes re-emulsification, whipping, and aeration to form a plastic foam system. Essentially, it is a thermodynamically unstable system. The high specific surface area and high free energy of the gas-liquid interface easily induce Ostwald ripening and gravity drainage, leading to problems such as bubble coalescence, structural collapse, phase separation, and poor stability in butter foam. Pickering emulsion foam, which is stable due to its dense interfacial film and strong resistance to deformation, has attracted much attention. Unlike emulsion foam constructed with surfactants, particle-formed emulsion foam exhibits better interfacial stability and lower environmental sensitivity.

[0004] Lipid particles or lipid crystals are currently widely used in maintaining emulsion and foam systems, serving a dual purpose of structural support and lipid simulation. Although the stabilizing effect of lipid particles (pickering) shows great potential in emulsion foaming, most isolated lipid particles lack suitable wettability and are insufficient to maintain long-term foam stability. Furthermore, lipid droplets can experience interfacial desorption, lipid precipitation, and lipid oxidation at the gas-liquid interface, further degrading the foam structure and quality.

[0005] Currently, plant-based emulsion foams, as an important alternative to animal-derived foams, have been applied in food and other fields. However, they suffer from significant instability and poor foam overflow rate, hindering their industrialization. Insufficient stability is mainly due to the low interfacial activity of plant proteins, making it difficult to form a dense, elastic interfacial film and resulting in poor synergy with lipid particles. This leads to bubble aggregation, foam collapse and stratification, further exacerbating oil-related problems and structural damage. Poor foam overflow rate manifests as unstable bubbles easily overflowing during foaming, causing raw material waste, affecting product uniformity, and being more significantly affected by environmental fluctuations, ultimately failing to meet the quality requirements of practical applications.

[0006] How to solve the problems of poor foaming properties, easy collapse, high oil separation rate, and insufficient storage stability of existing plant-based emulsions, and improve their overall quality and industrial adaptability, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the aforementioned problems, the inventors attempted to directly replace the soybean protein isolate gel particle dispersion with glycyrrhizic acid in the experiment to prepare Pickering emulsions. Emulsion foam was prepared by homogenization and stirring. The results showed that the final emulsion produced low foam generation, with large and unevenly distributed bubbles. The system was prone to separation, oil-water separation, and rapid foam collapse. They also tried adding glycyrrhizic acid solution to the soybean protein isolate gel particle dispersion before preparing Pickering emulsions. While homogenization and stirring resulted in a foam structure, the bubble uniformity was poor, and particle aggregation and droplet flocculation occurred. The foam interface film lacked density, leading to separation, volume shrinkage, and decreased stability during storage. Neither method effectively solved the aforementioned problems.

[0008] Therefore, this invention provides a method for preparing stable emulsion foam based on the Pickering effect of lipid droplets and the synergistic effect of glycyrrhizic acid. This invention stabilizes lipid droplets with soybean protein isolate gel particles and utilizes the Pickering effect of lipid droplets and the synergistic effect of glycyrrhizic acid to construct a dense gas-liquid interface film and a three-dimensional network of bulk phase, forming a plant-based emulsion foam system with good plasticity, excellent storage stability, and reduced oil precipitation, as well as its preparation process.

[0009] The first objective of this invention is to provide a method for simultaneously improving the foam stability and overflow rate of plant-based emulsions, comprising the steps of: After adding glycyrrhizic acid solution to Pickering emulsion, dispersion, refrigeration, and stirring were performed to obtain plant-based emulsion foam with improved stability and overflow rate. The final concentration of glycyrrhizic acid solution in the plant-based emulsion foam is 1-2% w / w.

[0010] In one embodiment, the Pickering emulsion is prepared by mixing a soybean protein isolate gel particle dispersion with an oil phase and then homogenizing the mixture to obtain the Pickering emulsion. The preparation method of the soy protein isolate gel particle dispersion is as follows: the soy protein isolate solution is stirred, heated, cooled, dispersed, and homogenized under high pressure to obtain a 5~10%w / w soy protein isolate gel particle dispersion. The oil phase is one or more of soybean oil, coconut oil, and flaxseed oil.

[0011] In one embodiment, the oil phase is obtained by mixing soybean oil and coconut oil in a volume ratio of 1~2:2~1.

[0012] In one embodiment, the dispersion is carried out at 7000~8000 rpm for 120~140 s; the refrigeration is carried out at 2~4℃ for 10~14 h; and the beating is carried out at 1100~1300 rpm for 5~10 min.

[0013] In one embodiment, the mass ratio of the soy protein isolate gel particle dispersion to the oil phase is 1~2:3~4.

[0014] In one embodiment, the heating process during the preparation of the soy protein isolate gel particle dispersion is as follows: heating at 90-95°C for 18-22 min; dispersion at 10000-12000 rpm for 4-6 min; and high-pressure homogenization at 500-700 Bar for 3-4 times.

[0015] In one embodiment, the homogenization during the Pickering emulsion preparation process consists of pre-homogenization at 3000-4000 rpm for 20-30 s, followed by high-shear homogenization at 13000-14000 rpm for 90-100 s.

[0016] A second objective of this invention is to provide a method for preparing a stable plant-based emulsion foam, comprising the steps of: Soy protein isolate gel particle dispersion was mixed with oil phase and homogenized to obtain oil / water Pickering emulsion; glycyrrhizic acid solution was added to oil / water Pickering emulsion, and after homogenization, refrigeration and stirring, plant-based emulsion foam was obtained; The final concentration of glycyrrhizic acid solution in the plant-based emulsion foam is 1-2% w / w; The preparation method of soy protein isolate gel particle dispersion is as follows: the soy protein isolate solution is stirred, heated, cooled, dispersed, and homogenized under high pressure to obtain a soy protein isolate gel particle dispersion of 5~10% w / w. The oil phase is one or more of soybean oil, coconut oil, and flaxseed oil.

[0017] In one embodiment, the oil phase is obtained by mixing soybean oil and coconut oil in a volume ratio of 1~2:2~1.

[0018] In one embodiment, the mass ratio of the soy protein isolate gel particle dispersion to the oil phase is 1~2:3~4; In the preparation of the soy protein isolate gel particle dispersion, the heating is carried out at 90~95℃ for 18~22 min; the dispersion is carried out at 10000~12000 rpm for 4~6 min; and the high-pressure homogenization is carried out at 500~700 Bar for 3~4 times.

[0019] In one embodiment, the dispersion during the preparation of the plant-based emulsion foam is carried out at 7000-8000 rpm for 120-140 s; the refrigeration is carried out at 2-4℃ for 10-14 h; and the stirring is carried out at 1100-1300 rpm for 5-10 min.

[0020] In one embodiment, the homogenization during the Pickering emulsion preparation process consists of pre-homogenization at 3000-4000 rpm for 20-30 s, followed by high-shear homogenization at 13000-14000 rpm for 90-100 s.

[0021] A third objective of this invention is to provide a plant-based emulsion foam prepared by any of the methods described above.

[0022] A fourth object of the present invention is to provide the application of any of the methods described above or the plant-based emulsion foams described above in plant-based creams, mousses, ice creams or desserts.

[0023] Beneficial effects This invention stabilizes lipid droplet particles using soy protein isolate gel particles and leverages its Pickering effect in synergy with natural glycyrrhizic acid. Combined with specific oil phase composition regulation, it maximizes the stability and foaming properties of the emulsion foam while avoiding the use of chemically synthesized emulsifiers, meeting the development needs of clean-label foods. This technology not only effectively solves the problems of interfacial desorption and oil precipitation that easily occur in traditional lipid particle Pickering foams under high shear or long-term storage, but also forms a dense gas-liquid interface film stabilized by both lipid droplet particles and glycyrrhizic acid through the solidification effect of the compounded oil phase and the interfacial regulation effect of glycyrrhizic acid. This film forms a network structure within the continuous phase, significantly enhancing the foam's resistance to deformation, gas and oil retention capacity, and long-term storage stability.

[0024] Specifically, this method improves the foam's plasticity by using a 1:1 blend of soybean oil and coconut oil, and achieves a balance between foaming properties and interfacial stability by adding an optimal amount of 1.5% glycyrrhizic acid. This results in emulsion foams with excellent formability and storage stability. After 72 hours of decorating and storage, the foam remains intact with no oil precipitation, regular bubble shape, and more compact interfacial enclosure. The foam overflow rate can reach 97.92%.

[0025] This invention provides a theoretical basis and technical approach for the development of natural, efficient, and stable food emulsion foams, and in particular, it provides a new solution for the formulation design and quality optimization of plant-based butter substitutes, effectively improving the sensory quality and market competitiveness of products. Attached Figure Description

[0026] Figure 1 Changes in the appearance of emulsion foam molding; Figure 2 Emulsion foam stability; Figure 3 Rheological properties of emulsion foam; Figure 4 : Emulsion foam overflow rate. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, where specific conditions are not specified, are generally performed under conventional conditions in the art. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar with the art.

[0028] The sources of raw materials involved in the examples are as follows: Soy protein isolate was purchased from Shandong Yuwang Ecological Food Industry Co., Ltd. Soybean oil was purchased from Yihai (Taizhou) Grain and Oil Industry Co., Ltd. The coconut oil was purchased from the Wenchang East Suburb Yezhengdao Coconut Processing Professional Cooperative. Glycyrrhizic acid was purchased from Shaanxi Linzhou Biotechnology Co., Ltd.

[0029] The measurement methods involved in the examples are as follows: 1. Macroscopic stability observation and measurement: To evaluate the macroscopic stability of emulsion foam samples, two aspects were measured: shape retention during refrigeration and resistance to collapse under room temperature conditions. First, the emulsion foam samples were whipped, extruded using a uniform piping bag, and stored at 4℃. Samples were observed and photographed at 0 h, 12 h, 24 h, 36 h, 48 h, and 72 h to record changes in appearance and oil precipitation. Next, freshly prepared emulsion foam samples were immediately and gently transferred into 10 mL transparent beakers, ensuring a uniform initial height for all groups. The samples were then allowed to stand at room temperature, and the foam collapse height was measured at 12 h, 24 h, 36 h, 48 h, and 72 h. Three replicates were set up for each group of samples, and results are expressed as mean ± standard deviation.

[0030] 2. Rheological measurements: Measurements were performed at room temperature using a rotational rheometer (MCR302, Anton Paar). An aluminum parallel plate fixture (PP25) was used with a fixed plate spacing of 1 mm. After loading the sample onto the measurement platform, it was allowed to stand for 5 minutes to equilibrate, minimizing the influence of temperature gradients on the test results. Dynamic shear tests were then conducted at shear rates ranging from 0.1 to 500 s⁻¹. - ¹ The apparent viscosity of the sample was recorded as a function of shear rate within a certain range. First, a strain scan was performed to determine the linear viscoelastic region of the sample. Then, small-amplitude oscillatory shearing was performed on the sample. Frequency scanning was performed under constant low strain of 0.1%, with the frequency set from 0.1% to 100 rad / s. At a fixed frequency of 1 Hz, the strain was increased from 0.1% to 100%. Large-amplitude oscillatory shearing was performed with a strain range of 1-1000% and a fixed frequency of 1 Hz. The dynamic changes of G′ and G″ were monitored.

[0031] 3. Determination of emulsion foam overflow rate: A certain amount of unwhipped sample is added to a beaker and its mass is recorded as m1 (g). Then, under specified conditions, the sample is whisked until a identifiable soft peak appears. Immediately after whisking, the excess foam above the rim is removed with a spatula, and the surface of the foam inside the beaker is smoothed to be flush with the rim to ensure a consistent foam volume. The mass of the remaining foam in the beaker is then weighed and recorded as m2 (g). The foam overflow rate is calculated using the following formula:

[0032] Where m1 and m2 represent the mass (g) of the unwhipped sample and the mass of foam remaining in the cup after whipping, respectively. Three parallel tests were set up for each sample.

[0033] Example 1: A method for preparing stable emulsion foam based on the Pickering effect of lipid droplets and glycyrrhizic acid A method for preparing stable emulsion foam based on the Pickering effect of lipid droplets in synergy with glycyrrhizic acid includes the following steps: 1. Preparation of soybean protein isolate gel particle dispersion: Accurately weigh soy protein isolate and add it to deionized water to prepare a 10% soy protein isolate solution. Stir at 400 rpm for 6 hours at room temperature to fully hydrate. Heat in a 95℃ water bath for 20 minutes and cool in an ice bath to 25℃. Then disperse at 10000 rpm for 5 minutes and homogenize under high pressure at 700 bar 3 times to obtain a 10% soy protein isolate gel particle dispersion. Refrigerate at 4℃ for later use.

[0034] 2. Preparation of Pickering emulsion: Using soybean oil as the oil phase, a 10% w / w soybean protein isolate gel particle dispersion was mixed with soybean oil at a ratio of 10 g: 30 g. The mixture was pre-homogenized at 3000 rpm for 30 s and then homogenized at 14000 rpm for 90 s to obtain a soybean oil-based Pickering emulsion.

[0035] 3. Preparation of emulsion foam: Add a 1.5% w / w glycyrrhizic acid solution to the Pickering emulsion, disperse at 7000 rpm for 120 s, refrigerate at 4℃ for 12 h, and then stir at 1300 rpm for 6 min to obtain the SO-1.5%GA emulsion foam sample.

[0036] Example 2: Replacing soybean oil with a mixture of soybean oil and coconut oil The specific implementation method is the same as in Example 1, except that soybean oil and coconut oil are combined as the oil phase to prepare SO / CO-1.5%GA emulsion foam sample.

[0037] The oil phase is obtained by melting coconut oil in a 35°C water bath and mixing it with soybean oil at a volume ratio of 1:1 for 5 minutes.

[0038] Example 3: Changing the amount of glycyrrhizic acid added Example 1 of the specific implementation method differs in that the amount of glycyrrhizic acid added is changed to 2%, and SO-2%GA emulsion foam sample is prepared.

[0039] Example 4: Changing the amount of glycyrrhizic acid added Example 2 of the specific implementation method differs in that the amount of glycyrrhizic acid added is changed to 2%, and SO / CO-2%GA emulsion foam sample is prepared.

[0040] Comparative Example 1: Changing the amount of glycyrrhizic acid added Example 1 of the specific implementation method differs in that the amount of glycyrrhizic acid added is changed to 0%, and SO-0%GA emulsion foam sample is prepared.

[0041] Comparative Example 2: Changing the amount of glycyrrhizic acid added Example 1 of the specific implementation method differs in that the amount of glycyrrhizic acid added is changed to 1%, and SO-1%GA emulsion foam sample is prepared.

[0042] Comparative Example 3: Changing the amount of glycyrrhizic acid added Example 2 of the specific implementation method differs in that the amount of glycyrrhizic acid added is changed to 1%, and SO / CO-1%GA emulsion foam sample is prepared.

[0043] Comparative Example 4: Changing the amount of glycyrrhizic acid added Example 2 of the specific implementation method differs in that the amount of glycyrrhizic acid added is changed to 0%, and SO / CO-0%GA emulsion foam sample is prepared.

[0044] Example 5: Performance determination of emulsion foam samples 1. Determination of emulsion foam stability The emulsion foam samples prepared in Examples 1-4 and Comparative Examples 1-4 were used to determine their shape retention during cold storage and their resistance to collapse at room temperature. The results are as follows: Figure 1 as well as Figure 2 As shown.

[0045] The results showed that the synergistic preparation of emulsion foam using the Pickering effect of lipid droplets and glycyrrhizic acid significantly improved the stability of the samples for decorating. The 1:1 blend of soybean oil and coconut oil exhibited better overall performance than the single soybean oil system, maintaining the integrity of the decorated bubbles after 72 hours of storage without oil precipitation, and showing regular bubble morphology and more compact interface enclosure.

[0046] In a single soybean oil phase system, when the amount of glycyrrhizic acid added is 0% or 1%, the foam emulsion has strong fluidity and cannot be decorated or shaped. In a 1:1 blended oil phase system of soybean oil and coconut oil, the samples with 0% and 1% glycyrrhizic acid added have less foam and are not easy to shape, with a low overflow rate, irregular bubble shape, and loose interface enclosure. However, when the amount of glycyrrhizic acid added is 1.5% or 2%, the emulsion foam prepared in both the single soybean oil phase system and the 1:1 blended oil phase system of soybean oil and coconut oil shows good stability.

[0047] 2. Determination of the rheological properties of emulsion foam The rheological properties of the emulsion foam samples prepared in Examples 1-4 and Comparative Examples 1-4 were measured, and the results are as follows: Figure 3 As shown.

[0048] The results showed that the emulsion foam prepared by utilizing the Pickering effect of lipid droplets and glycyrrhizic acid could enhance the stability of the elastic network structure of the system; the emulsion foam prepared when the amount of glycyrrhizic acid added was 1.5% or 2% exhibited better rheological properties.

[0049] 3. Determination of emulsion foam overflow rate The emulsion foam samples prepared in Examples 1-4 and Comparative Examples 1-4 were used to determine their foam overflow rate. The results are as follows: Figure 4 As shown.

[0050] The results showed that in a single soybean oil phase system, when the amount of glycyrrhizic acid added was 0% or 1%, the emulsion foam overflow rate was low, and the oil droplet size was large and loose. When the amount of glycyrrhizic acid added increased to 1.5%, the overflow rate reached 94.29%. When the amount of glycyrrhizic acid added continued to increase to 2%, the viscosity of the system increased dramatically, which hindered the introduction and dispersion of air, resulting in a decrease in the overflow rate.

[0051] In a 1:1 blend of soybean oil and coconut oil, the emulsions with 0% and 1% glycyrrhizic acid showed low foam overflow rates. When the glycyrrhizic acid content was 1.5%, the overflow rate reached 97.92%, and laser confocal microscopy revealed more regular bubbles and a denser interface. When the glycyrrhizic acid content increased to 2%, the system became excessively thickened. Although the structure became more upright, limited air intake led to a decrease in the overflow rate. Simultaneously, the blended oil system exhibited more regular bubbles and a more compact interface, demonstrating the advantage of interface stability.

[0052] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method of simultaneously improving plant-based emulsion foam stability, spill rate, characterized in that, Including the following steps: After adding glycyrrhizic acid solution to Pickering emulsion, dispersion, refrigeration, and stirring were performed to obtain plant-based emulsion foam with improved stability and overflow rate. The final concentration of glycyrrhizic acid solution in the plant-based emulsion foam is 1-2% w / w.

2. The method of claim 1, wherein, The Pickering emulsion is prepared by mixing a soybean protein isolate gel particle dispersion with an oil phase and then homogenizing the mixture to obtain the Pickering emulsion. The preparation method of the soy protein isolate gel particle dispersion is as follows: the soy protein isolate solution is stirred, heated, cooled, dispersed, and homogenized under high pressure to obtain a 5~10%w / w soy protein isolate gel particle dispersion. The oil phase is one or more of soybean oil, coconut oil, and flaxseed oil.

3. The method of claim 1, wherein, The dispersion is carried out at 7000~8000 rpm for 120~140s; the refrigeration is carried out at 2~4℃ for 10~14 h; the beating is carried out at 1100~1300 rpm for 5~10 min.

4. The method of claim 2, wherein, The mass ratio of the soybean protein isolate gel particle dispersion to the oil phase is 1~2:3~4.

5. The method of claim 2, wherein, In the preparation of the soy protein isolate gel particle dispersion, the heating is carried out at 90~95℃ for 18~22 min; the dispersion is carried out at 10000~12000 rpm for 4~6 min; and the high-pressure homogenization is carried out at 500~700 Bar for 3~4 times.

6. A method of making a stable plant-based emulsion foam, characterized in that, Including the following steps: Soy protein isolate gel particle dispersion was mixed with oil phase and homogenized to obtain oil / water Pickering emulsion; glycyrrhizic acid solution was added to oil / water Pickering emulsion, and then dispersed, refrigerated and stirred to obtain plant-based emulsion foam; The final concentration of glycyrrhizic acid solution in the plant-based emulsion foam is 1-2% w / w; The preparation method of soy protein isolate gel particle dispersion is as follows: the soy protein isolate solution is stirred, heated, cooled, dispersed, and homogenized under high pressure to obtain a soy protein isolate gel particle dispersion of 5~10% w / w. The oil phase is one or more of soybean oil, coconut oil, and flaxseed oil.

7. The method according to claim 6, characterized in that, The mass ratio of the soybean protein isolate gel particle dispersion to the oil phase is 1~2:3~4; In the preparation of the soy protein isolate gel particle dispersion, the heating is carried out at 90~95℃ for 18~22 min; the dispersion is carried out at 10000~12000 rpm for 4~6 min; and the high-pressure homogenization is carried out at 500~700 Bar for 3~4 times.

8. The method according to claim 6, characterized in that, In the preparation of plant-based emulsion foam, the dispersion is carried out at 7000~8000 rpm for 120~140 s; the refrigeration is carried out at 2~4℃ for 10~14 h; and the stirring is carried out at 1100~1300 rpm for 5~10 min.

9. The plant-based emulsion foam prepared by any one of claims 1 to 8.

10. The method of any one of claims 1 to 8 or the plant-based emulsion foam of claim 9, used in plant-based creams, mousses, ice creams or desserts.

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