A method for regulating water-in-oil emulsion foam based on crystalline non-crystalline emulsifier

Abstract

The present invention discloses a method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier, comprising heating, melting, mixing, and stirring an emulsifier, lacquer wax, and edible vegetable oil to obtain an oil phase mixture; heating deionized water to the same temperature and adding it to the oil phase mixture for homogenization; rapidly cooling the homogenized mixture in an ice-water bath to obtain an emulsion gel; and whipping the emulsion gel until an emulsion foam is formed. The present invention utilizes a crystalline emulsifier and uses water as an active ingredient to regulate the macroscopic physical properties of the emulsion foam, thereby forming a stable multiphase system while reducing the oil content. Application to food not only provides a more novel taste but also reduces fat and saturated fatty acid content, thus finding application in the development of healthy foods.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and fat application, and particularly relates to a method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier. Background Art

[0002] Emulsion foam is a novel multiphase system containing water, oil, and gas. It can be categorized by the difference in the continuous phase, such as aqueous continuous phase, bicontinuous phase, and oil continuous phase. Emulsion foam is already widely used in the food industry, such as in ice cream and whipped cream. During whipping, fat globules penetrate the film and interact with each other, forming a crystalline network that stabilizes the bubbles. Proteins can also stabilize bubbles using the Pickering mechanism alone or as co-emulsifiers in combination with fat crystals.

[0003] As a multiphase system, the challenge in preparing and stabilizing emulsion foams lies in selecting an emulsifier that can simultaneously stabilize different interfaces. Different emulsifiers or Pickering particles are used to stabilize the oil-water interface and the oil-gas interface in emulsion foams. Surfactants used to stabilize the water-gas interface are more likely to also stabilize the water-oil interface. However, a single emulsifier is unlikely to simultaneously stabilize both the oil-gas and oil-water interfaces. Therefore, composite emulsifiers are often used to prepare emulsion foams with an oily continuous phase. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] One of the objectives of the present invention is to provide a method for regulating oil-in-water emulsion foam based on a crystalline non-crystalline emulsifier, wherein the emulsifier is used to stabilize the oil-water interface and to regulate the crystallization position of the wax in the bulk phase through the use of the emulsifier, thereby regulating the microstructure and macroscopic physical properties of the oil-in-water emulsion foam.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for regulating the foam of water-in-oil emulsion based on a crystalline non-crystalline emulsifier, comprising:

[0008] Heat, melt, mix and stir the emulsifier, lacquer wax and edible vegetable oil to obtain an oil phase mixture;

[0009] Heat the water phase to the same temperature and add it dropwise to the oil phase mixture until homogenous;

[0010] The homogenized mixture is rapidly cooled in an ice-water bath to obtain an emulsion gel;

[0011] Whip the emulsion gel until it forms emulsion foam.

[0012] As a preferred embodiment of the method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier of the present invention, the emulsifier is a compound of polyglycerol polyricinoleate and a crystalline emulsifier or a non-crystalline emulsifier.

[0013] As a preferred embodiment of the method for regulating the foam of an oil-in-water emulsion based on a crystalline non-crystalline emulsifier of the present invention, the crystalline emulsifier includes one or more of polyglycerol polyricinoleate and glyceryl monostearate, polyglycerol fatty acid esters, mono- and diglycerol fatty acid esters, sodium stearoyl lactylate, and citric acid fatty acid glyceride.

[0014] As a preferred embodiment of the method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier of the present invention, the non-crystalline emulsifier comprises one or more of modified starch particles and fumed silica.

[0015] As a preferred embodiment of the method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier of the present invention, the content of the emulsifier is 1 to 3 wt % of the oil phase.

[0016] As a preferred embodiment of the method for regulating oil-in-water emulsion foam based on a crystalline non-crystalline emulsifier of the present invention, the edible vegetable oil includes one or more of soybean oil, rapeseed oil, peanut oil, sunflower oil, rice bran oil, corn oil, linseed oil, olive oil, wheat germ oil, cottonseed oil, almond oil, tea seed oil, sesame oil, and palm oil.

[0017] As a preferred embodiment of the method for regulating the foam of a water-in-oil emulsion based on a crystalline non-crystalline emulsifier of the present invention, the content of the lacquer wax is 10 to 20 wt%.

[0018] As a preferred embodiment of the method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier of the present invention, the heating time for melting is 2 to 10 minutes and the heating temperature is 75 to 90°C.

[0019] As a preferred embodiment of the method for regulating the foam of a water-in-oil emulsion based on a crystalline non-crystalline emulsifier of the present invention, wherein: the homogenization is performed by pre-homogenization at 8000 rpm for 30 seconds and then homogenization at 10000 rpm for 2 minutes.

[0020] As a preferred embodiment of the method for adjusting the foam of a water-in-oil emulsion based on a crystalline non-crystalline emulsifier of the present invention, the whipping time is 8 to 14 minutes.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention structures the bulk phase through lacquer wax and uses an emulsifier to regulate the crystallization position of the wax in the bulk phase. The water phase is then used as a functional component to regulate the macroscopic physical properties of the emulsion foam. As the water content increases, its foaming rate, rheological properties and printing height all change accordingly. The prepared emulsion foam has solid-like properties and can be applied to 3D printing to increase its personalized customization. While forming a stable multiphase system, the oil content is reduced. When applied to food, it can not only bring more novel tastes but also reduce the fat content and improve the healthiness of the food. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0024] Figure 1 It is a physical picture of Example 1 and Comparative Example 1.

[0025] Figure 2 These are microscopic images of Example 2 and Comparative Example 2 (taking W:O=50:50 w / w as an example); wherein A is an emulsion foam prepared from lacquer wax (5 g), PGPR (0.25 g), GMS (0.25 g), soybean oil (50 g) and deionized water (50 g); and B is an emulsion foam prepared from lacquer wax (5 g), PGPR (0.5 g), soybean oil (50 g) and deionized water (50 g).

[0026] Figure 3 The microstructure and droplet distribution diagrams of Examples 2 and 3; A is an optical micrograph; B is a polarized light micrograph; and C is a droplet size distribution diagram.

[0027] Figure 4 These are confocal laser scanning microscopy (CLSM) images of Examples 2 and 3; A is an emulsion foam with different oil-water ratios (×40); B is an emulsion foam with W:O=50:50 w / w (×120) (the oil, water and crystal phases are dyed red, green and blue, respectively).

[0028] Figure 5is the foaming property of Example 2 and Example 3; wherein A is the foaming rate of the oil-water ratio emulsion foam; B is the foaming rate of the re-prepared emulsion foam; and C is the thermal reversibility of the emulsion foam (taking the crystalline emulsion foam with W:O=50:50w / w as an example).

[0029] Figure 6 The rheological properties of Example 2 and Example 3; wherein A is the strain scan of the emulsion gel; B is the strain scan of the emulsion foam; C is the frequency scan of the emulsion foam; and D is the time scan of the emulsion foam.

[0030] Figure 7 These are the 3D printed physical images of Examples 2 and 3.

[0031] Figure 8 The foaming performance comparison chart of Example 2 and Comparative Example 3 is shown.

[0032] Figure 9 The microstructure diagrams of Example 1 and Comparative Example 4 are shown. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0036] Unless otherwise specified, the raw materials used in the examples were purchased commercially.

[0037] The embodiment of the present invention adopts the following test method:

[0038] Microstructural Observation: The microstructures of different latex foams were imaged using an optical and polarized light microscope equipped with a digital camera. A small amount of sample was applied to a glass slide using a capillary pipette and then gently covered with a thin coverslip to ensure structural integrity. Images were taken of selected representative areas, and the optical and polarized light micrographs were aligned.

[0039] Particle size determination: To accurately determine droplet size, droplet size was manually determined using ImageJ software. For each sample, 600–800 droplets were measured from a representative image. Droplet size histograms were plotted using Origin, and a Gaussian distribution was used to fit the curve.

[0040] Confocal Laser Scanning Microscopy: Confocal laser scanning microscopy (CLSM) was used to further investigate the microstructure of the different latex foams. The aqueous phase, oil phase, and crystals were stained with FITC, Nile Red, and Nile Blue, respectively. The microstructure of the samples was observed at selective excitation wavelengths of 488 nm (fluorescein isothiocyanate, FITC), 520 nm (Nile Red), and 610 nm (Nile Blue). Sample preparation, storage, and observation were all performed at 4°C in the dark.

[0041] Foaming rate determination: The foaming rate is calculated using the following formula:

[0042]

[0043] Among them, m oleo : Oil gel / mixed fat mass before whipping; m foam : The quality of oil foam after whipping.

[0044] Rheological properties were tested: The linear viscoelastic region (LVR) was determined by strain sweeps performed over a strain amplitude range of 0.01-100%. Frequency sweep tests were performed over a frequency range of 0.1-10 Hz. Temperature sweep tests were performed over a frequency range of 0°C to 60°C at a strain of 0.1%. Time sweep tests were performed with strain varying between 0.1% and 100%, with a strain of 0.1% between 0-100 s and 200-300 s, and 100% between 100-200 s. All tests were conducted using aluminum plates (40 mm diameter) at 4°C with a gap of 1000 μm.

[0045] 3D Printing: A cone model (30 mm diameter, 30 mm height; 30% infill) was used to evaluate the printability of different latex foams. A 0.84 mm diameter print nozzle was used at a printing speed of 25 mm / s. Images of the 3D prints of the different latex foams were captured, and the actual height of the printed samples was measured three times for each sample.

[0046] Example 1

[0047] (1) A mixture of lacquer wax (5 g), PGPR (0.25 g), GMS (0.25 g), and soybean oil (50 g) was heated to 85° C. using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0048] (2) Add 50 g of deionized water (preheated to 85°C) dropwise to the oil phase mixture and mix thoroughly using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 2 min);

[0049] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0050] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0051] Comparative Example 1

[0052] In Comparative Example 1, crystalline emulsion foam was prepared without adding PGPR on the basis of Example 1. The specific steps were:

[0053] (1) A mixture of lacquer wax (5 g), GMS (0.5 g) and soybean oil (50 g) was heated to 85° C. using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0054] (2) The aqueous phase (50 g) preheated to 85°C was added dropwise to the oil phase mixture and thoroughly mixed using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 2 min);

[0055] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0056] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0057] The effects of different emulsifiers on emulsion foam in Example 1 and Comparative Example 1 are as follows: Figure 1 It can be seen that GMS alone cannot stabilize the emulsion foam with an oil-water ratio of 50:50 w / w.

[0058] Comparative Example 2

[0059] In Comparative Example 2, a crystalline emulsifier was prepared without adding GMS on the basis of Example 1. The specific steps were:

[0060] (1) As shown in Table 1, a mixture of lacquer wax (5-9 g), PGPR (0.5-0.9 g) and soybean oil (50-90 g) was heated to 85°C using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0061] (2) The aqueous phase (10-50 g) preheated to 85°C was added dropwise to the oil phase mixture and thoroughly mixed using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 2 min);

[0062] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0063] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0064] The microstructures of the emulsion foams with different emulsifiers in Example 2 and Comparative Example 2 are as follows: Figure 2 As shown in the figure, it can be seen that PGPR, as a small molecule emulsifier, is difficult to resist the mechanical force during whipping, and the droplets are severely condensed.

[0065] Example 2

[0066] In Example 2, crystalline emulsion foam was prepared by changing the water phase content on the basis of Example 1. The specific steps are:

[0067] (1) As shown in Table 1, a mixture of lacquer wax (5-9 g), PGPR (0.25-0.45 g), GMS (0.05-0.25 g), and soybean oil (50-90 g) was heated to 85°C using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0068] (2) Deionized water (10-50 g) preheated to 85°C was added dropwise to the oil phase mixture and thoroughly mixed using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 2 min);

[0069] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0070] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0071] Example 3

[0072] In this example, the emulsion foam is prepared by changing the emulsifier of Example 2, and the steps are as follows:

[0073] (1) As shown in Table 1, a mixture of lacquer wax (5-9 g), PGPR (0.25-0.45 g), fumed silica (0.05-0.25 g), and soybean oil (50-90 g) was heated to 85° C. using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0074] (2) The aqueous phase (10-50 g) preheated to 85°C was added dropwise to the oil phase mixture and thoroughly mixed using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 2 min);

[0075] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0076] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0077] Table 1

[0078]

[0079] Figure 3 The following are microstructure images of Examples 2 and 3, including optical and polarizing microscopy images. The microstructures of emulsion foams prepared with a blend of crystalline and amorphous emulsifiers were observed using corresponding illumination and polarization micrographs, revealing significant differences in their microstructures. For emulsion foams based on crystalline emulsifiers, droplets primarily concentrated and aggregated on the surface of bubbles. The number of droplets in the field of view increased with increasing water content, with droplets clustering more tightly around bubbles. For amorphous emulsifiers, water droplets were simply dispersed in the oil phase, with the number of droplets increasing with increasing water content. No droplet aggregation was observed at the oil-air interface. Furthermore, the droplet sizes in emulsion foams with different water contents were calculated. The results showed that water content had little effect on droplet size, but different emulsifier types had a significant effect on droplet size. The average droplet size in emulsion foams based on crystalline emulsifiers was smaller than that in amorphous emulsifiers, likely due to different stabilization mechanisms of the emulsifiers. GMS, as a crystalline emulsifier, rapidly adsorbs at interfaces to reduce surface tension. Fumed silica as Pickering particles requires more time to adsorb on the interface and its stable droplet size is usually larger.

[0080] Figure 3It can be seen that in crystalline emulsifier-based emulsion foams, the droplet surface is covered with crystals. This is manifested as a bright circular halo surrounding the droplet in the polarization image. This is likely due to the template effect of the crystalline emulsifier, causing the wax in the bulk phase to crystallize on the droplet surface. Emulsifiers can be used to adjust the distribution of crystals in the bulk phase, further affecting the macroscopic properties of the emulsion foam.

[0081] Figure 4 : The laser confocal scanning micrographs of Examples 2 and 3. Figure 4 The oil phase appears red, while the water phase appears as dispersed green spheres. Furthermore, the red oil phase contains large black voids, representing air bubbles that cannot be stained. Comparing the CLSM images of foams based on crystalline and amorphous emulsifiers, green droplets can be seen clustering at the edges of the bubbles in the crystalline emulsifier-based foam. As the water content increases, the droplets clustered on the bubble surface become more compact, gradually forming a ring of green droplets around the bubble. In contrast, the green droplets in the amorphous emulsifier-based foam are evenly distributed throughout the red oil phase. Although the number of green droplets increases with increasing water content, no significant aggregation is observed on the bubble surface. Figure 4 B. Further microstructure observations of the crystalline and non-crystalline emulsifier-based emulsion foams at ×120 magnification revealed that in the crystalline emulsion foams, a blue spherical crystalline phase overlapped with the green aqueous phase, indicating the presence of crystals on the water droplets. These crystals, in addition to the crystalline emulsifier GMS, may also be composed of wax crystals induced by the GMS template effect. Liquid droplets aggregated around black bubbles and connected to the blue crystals surrounding them. In contrast, in the non-crystalline emulsifier-based emulsion foams, only black pores were observed, and the blue crystalline phase did not overlap with the green droplets. The bubbles were primarily surrounded by blue crystals, indicating that the crystals primarily stabilized the bubbles in the emulsion foams. Furthermore, the red oil phase of all emulsion foams overlapped with the light blue crystalline phase, indicating that crystals in the oil phase remained unadsorbed at the oil-air and oil-water interfaces. The remaining crystalline network in the oil phase could further entrap bubbles and droplets, providing enhanced stability to the entire emulsion foam system.

[0082] Figure 4 It can be seen that in the crystalline emulsifier-based emulsion foam, the droplet surface is covered with crystals. This is reflected as a blue spherical crystalline phase in the laser confocal image, further demonstrating that the crystal distribution in the emulsion foam can be regulated by the type of emulsifier. Furthermore, all emulsion foams also contain blue crystalline phases within the red oil phase, demonstrating that wax crystals are also distributed in the bulk phase, their structure primarily provided by the crystalline network within the bulk phase.

[0083] Figure 5The foaming properties of Examples 2 and 3 are shown. Comparing the foaming rates of emulsions with different water contents reveals that the foaming rate of both crystalline and non-crystalline emulsifier-based foams decreases with increasing water content. This is likely due to the decrease in wax content (wax content calculated based on the mass of the oil phase) as water content increases. Furthermore, comparing emulsions prepared with crystalline and non-crystalline emulsifiers at the same water content reveals that the foams prepared with different emulsifier types have similar foaming rates at low water content (W:O = 10:90 w / w). However, at medium and high water contents (W:O = 30:70 and 50:50 w / w), the foaming rate of emulsions prepared with non-crystalline emulsifiers is higher than that of crystalline emulsifiers. This may be attributed to the fact that some wax crystals crystallize on the droplet surface due to the template effect of the GMS, rather than forming a crystalline network in the bulk phase. During the subsequent whipping process, these wax crystals are less able to act as Pickering particles to stabilize bubbles, resulting in a reduced foaming rate. In contrast, in the emulsion foam prepared with non-crystallizing emulsifiers, almost all wax crystals form a crystal network in the bulk phase, which breaks during the whipping step, and the wax crystals adsorb on the bubble surface, thereby stabilizing the bubbles.

[0084] Figure 5 The foaming properties of emulsion foams with different emulsifiers show that crystalline emulsifiers can regulate the crystallization of wax in the bulk phase on the surface of the droplets through the template effect. These wax crystals are difficult to act as Pickering particles to stabilize bubbles. Therefore, the foaming properties of emulsion foams can be adjusted by using different types of emulsifiers.

[0085] Figure 6 As shown in the rheological behavior of Examples 2 and 3, the initial modulus of the emulsion foam based on crystalline emulsifiers increases with increasing water content. Interestingly, however, the water content has almost no effect on the initial modulus of the emulsion foam based on non-crystalline emulsifiers. This may be because the droplets cannot provide more modulus to the emulsion foam by simply filling the bulk phase as active fillers. In this case, the modulus is mainly provided by the crystal network in the bulk phase. In contrast, the emulsion foam based on crystalline emulsifiers contains droplets with a crystalline shell, which can provide more modulus to the entire system. Figure 6 As shown in Figure C, G' and G" of all latex foams increase with frequency, showing a certain frequency dependence. The increase in G' represents higher viscoelasticity. G'>G" of all latex foams in the entire frequency range indicates that the latex foam exhibits solid-like properties dominated by elastic behavior, which is conducive to shape retention after 3D printing. The thixotropy of latex foams has also been studied, such as Figure 6Figure D shows the strain varying between 0.1% and 100%, with each stage lasting 100 seconds. It can be seen that the emulsion foam exhibits liquid-like properties at higher strains (G">G'), indicating that its structure is completely destroyed. However, when the strain is reduced to 0.1%, the emulsion foam exhibits solid-like properties (G'>G"), demonstrating that all emulsion foams have a certain modulus recovery. This is the basis for the application of emulsion foam in 3D printing, as it can ensure shape retention after passing through the printing nozzle.

[0086] Figure 6 The rheological properties of emulsion foams prepared with different emulsifiers can be determined. Crystalline emulsifiers can, through a template effect, induce the crystallization of wax in the bulk phase on the surface of droplets. These droplets containing crystals on the surface can act as active filler particles and connect with the matrix, providing a certain modulus for the entire system. In contrast, amorphous emulsifiers cannot achieve this. Therefore, the rheological properties of emulsion foams can be adjusted by using different types of emulsifiers.

[0087] Figure 7 For the 3D printing samples of Examples 2 and 3, all emulsion foams exhibited the properties of soft solid materials and possessed a certain degree of self-support. Therefore, their application in 3D printing is feasible. The modulus of different emulsion foams varies depending on their water content and the type of emulsifier. The print height of crystalline emulsion foams increased with increasing water content, while the height of non-crystalline emulsion foams showed little change with water content.

[0088] Figure 7 3D printed samples of emulsion foams using different emulsifiers show that crystalline emulsifiers can induce wax crystallization on the surface of the droplets, allowing the droplets to act as active filler particles and provide a certain modulus to the system. Therefore, the height of 3D printed samples of emulsion foams based on crystalline emulsifiers increases with increasing water content. In contrast, this is not the case with non-crystalline emulsifiers. Therefore, using different types of emulsifiers can adjust the 3D printing performance of emulsion foams.

[0089] Comparative Example 3

[0090] In Comparative Example 3, a crystalline emulsifier was prepared by changing the type of wax on the basis of Example 1. The specific steps are:

[0091] (1) As shown in Table 1, a mixture of natural waxes (sunflower wax, rice bran wax, carnauba wax, beeswax, candelilla wax, and sugarcane wax) (5 g), PGPR (0.25 g), GMS / fumed silica (0.25 g), and soybean oil (50 g) was heated to 85° C. using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0092] (2) Add 50 g of deionized water (preheated to 85°C) dropwise to the oil phase mixture and mix thoroughly using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 2 min);

[0093] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0094] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0095] The foaming properties of Example 2 and Comparative Example 3 are as follows: Figure 8 As shown in the figure, it can be seen that other natural waxes are difficult to whip.

[0096] Comparative Example 4

[0097] In Comparative Example 4, a crystalline emulsifier was prepared by changing the total amount of the composite emulsifier on the basis of Example 1. The specific steps are:

[0098] (1) As shown in Table 1, a mixture of lacquer wax (5 g), PGPR (3 g), GMS (3 g) and soybean oil (50 g) was heated to 85°C using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0099] (2) The aqueous phase (50 g) preheated to 85°C was added dropwise to the oil phase mixture and thoroughly mixed using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 2 min);

[0100] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0101] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0102] The microstructures of Example 1 and Comparative Example 4 are as follows: Figure 9 As shown in Figure 2, it can be seen that excessive emulsifier will lead to irregular droplets and even cause the droplets to break.

[0103] Comparative Example 5

[0104] In Comparative Example 4, a crystalline emulsifier was prepared by changing the homogenization time on the basis of Example 3. The specific steps are:

[0105] (1) As shown in Table 1, a mixture of lacquer wax (5-9 g), PGPR (0.25-0.45 g), fumed silica (0.05-0.25 g), and soybean oil (50-90 g) was heated to 85° C. using a multi-point magnetic stirrer to obtain an oil phase mixture;

[0106] (2) The aqueous phase (10-50 g) preheated to 85°C was added dropwise to the oil phase mixture and thoroughly mixed using a high-speed homogenizer (8000 rpm, pre-homogenization for 30 s; then homogenization at 10000 rpm for 30 s);

[0107] (3) The homogenized sample was rapidly cooled in an ice-water bath and stored at 4°C for 12 h to ensure complete crystallization, obtaining an emulsion gel;

[0108] (4) The emulsion gel was whipped in an ice water bath using a hand-held whisk at a speed of approximately 1000 rpm for 4 cycles (one cycle consisted of beating for 2 minutes followed by a 30-second rest period) to prepare emulsion foam.

[0109] Comparative Example 5 shows that if the homogenization time is too short, it is difficult for the fumed silica particles to be adsorbed on the oil-water interface, and the emulsion gel is unstable under the conditions in Table 1.

[0110] In summary, the present invention utilizes different emulsifiers to alter the location of wax crystals in the bulk phase, thereby modifying the interaction between the droplets and the matrix. By using crystalline emulsifiers, water is used as a functional component to modulate the macroscopic properties of the emulsion foam. Furthermore, the introduction of a gas phase can reduce lipid content, making its application in food products more compatible with healthy dietary trends.

[0111] The present invention utilizes the template effect of crystalline emulsifiers to regulate the distribution of crystals in the bulk phase, allowing surface-covered droplets to participate as functional components in the construction of the emulsion foam. In contrast, non-crystalline emulsifiers prevent droplets from providing structure to the emulsion foam. However, crystalline emulsion foams reduce the amount of crystals in the bulk phase, decreasing the amount of crystals that serve as Pickering particles to stabilize bubbles, thereby reducing the foaming rate. Therefore, the use of different composite emulsifiers can achieve the goal of using emulsifiers to regulate the macroscopic physical properties of emulsion foams.

[0112] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for regulating the foam of a water-in-oil emulsion based on a crystalline non-crystalline emulsifier, characterized in that: include, The emulsifier, lacquer wax and edible vegetable oil are heated, melted and mixed to obtain an oil phase mixture; the content of the emulsifier is 1-3 wt% of the oil phase mixture; the content of the lacquer wax is 10-20 wt%; the heating time for melting is 2-10 minutes and the heating temperature is 75-90°C; Heat water to the above temperature and add it dropwise into the oil phase mixture until homogenous; The homogenized mixture is rapidly cooled in an ice-water bath to obtain an emulsion gel; Whip the emulsion gel until emulsion foam is formed; Wherein, the emulsifier is a compound of polyglycerol polyricinoleate and a crystalline emulsifier or a non-crystalline emulsifier; The crystalline emulsifier includes one or more of glyceryl monostearate, polyglyceryl fatty acid ester, mono- and diglyceryl fatty acid ester, sodium stearoyl lactylate, and citric acid fatty acid glyceride; The non-crystalline emulsifier is fumed silica.

2. The method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier according to claim 1, characterized in that: The edible vegetable oil includes one or more of soybean oil, rapeseed oil, peanut oil, sunflower oil, rice bran oil, corn oil, linseed oil, olive oil, wheat germ oil, cottonseed oil, almond oil, tea seed oil, sesame oil, and palm oil.

3. The method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier according to claim 1 or 2, characterized in that: The homogenization was performed by pre-homogenization at 8000 rpm for 30 seconds and then homogenization at 10000 rpm for 2 minutes.

4. The method for regulating water-in-oil emulsion foam based on a crystalline non-crystalline emulsifier according to claim 3, characterized in that: The whipping time is 8 to 14 minutes.

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