A high internal phase pickering emulsion gel, and a preparation method and application thereof

Abstract

The application provides a high internal phase Pickering emulsion gel and a preparation method and application thereof. The preparation method of the high internal phase Pickering emulsion gel comprises the following steps: S1, respectively preparing a zein solution and a microcrystalline chitin solution; S2, preparing a Zein-CNCs compound from the zein solution and the microcrystalline chitin solution at pH 5.5-7.5; and S3, mixing MCT oil with the Zein-CNCs compound at a mass ratio of (10-15):3, and then homogenizing to obtain the high internal phase Pickering emulsion gel. The high internal phase Pickering emulsion gel can form a relatively thick interface layer, and has the advantages of strong plasticity, good emulsification and stability, high oil loading rate, low oil oxidation rate, good loading and controlled release effect on flavor substances and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high internal phase emulsion, in particular to a high internal phase Pickering emulsion gel and a preparation method and application thereof. BACKGROUND

[0002] With the improvement of living standards, consumers are more eager to obtain "pure natural" products and "clean label" food, and the development of natural substitutes to replace traditional chemical surfactant emulsion food has become a new trend in the food industry. At present, the safety hazard of trans fats in some partially hydrogenated oils (PHOs) has become the focus of attention; studies have shown that excessive intake of trans fats will cause serious health problems to the human body, such as cardiovascular and cerebrovascular diseases, diabetes and atherosclerosis, etc. Therefore, the food industry urgently needs to find special oil products that can replace PHOs.

[0003] High internal phase emulsion gel (HIPPE gel) is a highly concentrated emulsion system, and the volume fraction of the internal oil phase is greater than 74%, and it has the characteristics of strong plasticity of solid gel. When the volume fraction of the internal oil phase exceeds 74%, the dispersed droplets will reach the maximum packing density, so the selection of emulsifiers for high internal phase emulsion is particularly important, and if the emulsifying ability of bio-based polymers is poor, the emulsion system will collapse. However, the existing high internal phase emulsion gel (HIPPE gel) or high internal phase Pickering emulsion gel (co-HIPPE gel) generally has the obvious defects of high oil oxidation rate, poor plasticity, emulsification and stability of the emulsion system, low oil loading rate, low loading capacity of functional substances and poor controlled release effect, thereby being not conducive to the practical application of high internal phase emulsion gel.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a high internal phase Pickering emulsion gel and a preparation method and application thereof, which has the obvious advantages of strong plasticity, good emulsification and stability, high oil loading rate, low oil oxidation rate, good loading and controlled release effect of flavor substances, etc.

[0006] The present application provides a preparation method of a high internal phase Pickering emulsion gel, comprising the following steps:

[0007] S1: preparing a zein solution and a microcrystalline chitin (CNCs) solution, respectively;

[0008] S2: preparing a Zein-CNCs complex by mixing the zein solution and the microcrystalline chitin solution at pH 5.5-7.5;

[0009] S3: homogenize the MCT oil and the Zein-CNCs compound with a mass ratio (10-15):3 to obtain a high internal phase Pickering emulsion gel.

[0010] The high internal phase Pickering emulsion gel of the present application has pH responsiveness, the Zein-CNCs compound prepared in step S2 at pH 5.5-6.0 is a Zein-CNCs soluble compound, at this time, step S3 corresponds to the preparation of a high internal phase Pickering emulsion gel (HIPPE gel); the Zein-CNCs compound prepared in step S2 at pH 6.5-7.5 is a Zein-CNCs compound coagulum, at this time, step S3 corresponds to the preparation of a coagulation type high internal phase Pickering emulsion gel (co-HIPPE gel); preferably, the Zein-CNCs compound coagulum and the coagulation type high internal phase Pickering emulsion gel (co-HIPPE gel) are prepared at pH 6.5-7.5.

[0011] In step S1, the mass content of the zein solution is 1-1.5wt%; the mass concentration of the microcrystalline chitin solution is 18-22g / mL.

[0012] Specifically, the preparation method of the zein solution comprises:

[0013] A) dissolving zein in a mixed solvent of ethanol and water, stirring until completely transparent to obtain a primary solution;

[0014] B) adding deionized water to the primary solution quickly, stirring, and then evaporating ethanol and part of water to obtain a zein solution with a mass content of 1-1.5wt%;

[0015] Wherein, the volume content of ethanol in the mixed solvent is 80-90%; the amount ratio between zein, mixed solvent and deionized water is 1g:40-45mL:80-85mL; the stirring speed is 250-350rpm, and the stirring time is 25-35min.

[0016] The preparation method of the microcrystalline chitin solution comprises:

[0017] A) dissolving chitin in a hydrochloric acid solution, performing a boiling water bath under stirring, and then centrifuging, washing, and collecting the solid;

[0018] B) adding deionized water to the solid for high-pressure homogenization to obtain a microcrystalline chitin solution with a mass concentration of 18-22g / mL;

[0019] The concentration of the hydrochloric acid solution is 2.5-3.5M; the boiling water bath time is 1-2h; the ratio of the use amount of chitin, hydrochloric acid solution and deionized water is 1g:45-55mL:45-55mL; the high-pressure homogenization is carried out at 25-35MPa, and the high-pressure homogenization time is 4-6min.

[0020] In step S2, the mass content of microcrystalline chitin in the Zein-CNCs compound is controlled to be 0.7-0.8wt%, and the mass ratio of microcrystalline chitin to zein is 1:(1-3).

[0021] In step S3, the homogenization includes: homogenization at 8000-15000rpm for 60-120s; in particular, before mixing, the functional substance is first mixed with MCT oil, and then mixed with the Zein-CNCs compound at a mass ratio of (10-12):3 before homogenization; the functional substance is not strictly limited, for example, it can be a flavoring substance.

[0022] In the present application, the flavoring substance can be selected from at least one of diacetyl, 2-pentanone, 2-heptanone, ethyl hexanoate and D-limonene; specifically, the mass concentration of diacetyl in MCT oil is 500-600mg / L; the mass concentration of 2-pentanone in MCT oil is 200-250mg / L; the mass concentration of 2-heptanone in MCT oil is 1000-1200mg / L; the mass concentration of ethyl hexanoate in MCT oil is 2800-3000mg / L; and the mass concentration of D-limonene in MCT oil is 2800-3000mg / L.

[0023] The present application also provides a high internal phase Pickering emulsion gel prepared according to the above preparation method.

[0024] The present application also provides the use of the above high internal phase Pickering emulsion gel in the controlled release of flavoring substances.

[0025] The implementation of the present application has at least the following advantages:

[0026] 1. The high internal phase Pickering emulsion gel of the present application has a polysaccharide substance with viscoelasticity in the continuous phase, which can make the high internal phase Pickering emulsion have higher viscoelasticity and stronger plasticity, thereby having a higher oil loading rate;

[0027] 2. The present application improves the stability of the high internal phase Pickering emulsion gel by constructing an interface enhancement means of zein-microcrystalline chitin coagulum, which covers the CNCs with a "finger structure" on the surface of the Zein small ball, thereby forming a thick interface layer barrier and a space barrier to hinder the aggregation and collapse of the droplets, greatly improving the stability of the emulsion gel;

[0028] 3、The coacervate layer in the high internal phase Pickering emulsion gel of the present application can form a three-dimensional network structure, which hinders the entry of free radicals in the chain reaction, thereby inhibiting the lipid oxidation of the emulsion; at the same time, the presence of the coacervate layer also prevents the interaction between oxygen and lipids in the emulsion, interrupts the peroxidation, and inhibits the lipid oxidation of the emulsion, so that the oil oxidation rate is greatly reduced;

[0029] 4、The high internal phase Pickering emulsion gel of the present application has a high load of flavor substances, and a dense coacervate layer is formed at the oil-water interface, which can delay the flavor release caused by the structure damage brought by mechanical stirring, and the flavor substances take a longer time to pass through the oil-water interface during the release from the oil phase to the air, thus effectively hindering the rapid release of the flavor to a certain extent, and achieving the long-term controlled release effect of the flavor. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0031] Figure 1 Morphology analysis results of CNCs and Zein-CNCs composite prepared in Example 1; wherein: A is the SEM image of CNCs at pH 5.5, 6.5, 8.5, B is the corresponding principle diagram of "Yingzhi structure" shown by CNCs; C is the TEM image of Zein-CNCs at pH 5.5-8.5;

[0032] Figure 2 CLSM images of HIPPE gel and co-HIPPE gel prepared in Example 2;

[0033] Figure 3 Particle size measurement results of HIPPE gel and co-HIPPE gel prepared in Example 2; wherein: A is the particle size distribution graph, B is the optical microstructure graph;

[0034] Figure 4 Primary oxidation determination results of HIPPE gel and co-HIPPE gel prepared in Example 2;

[0035] Figure 5Harrison mathematical model non-linear fit plot for the flavor HIPPE gel and flavor co-HIPPE gel prepared in Example 3; where: A is diacetyl, B is 2-pentanone, C is 2-heptanone, D is ethyl hexanoate, E is D-limonene;

[0036] Figure 6 Optical microstructure of HIPPE prepared for Control Example 1. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0038] It is also important to note that the terms "including", "comprising", and variations thereof, as used in this description, are intended to be broad and encompass the terms "consisting of" and "consisting essentially of" unless otherwise indicated. Use of the term "or" in the context of "A or B" is intended to mean "A or B or both" unless otherwise indicated.

[0039] The technical solutions of the present application will be described clearly and completely in combination with the embodiments. Obviously, the described embodiments are part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0040] Example 1

[0041] The preparation method of the Zein-CNCs composite of the present embodiment is as follows:

[0042] 1. Preparation of Zein solution

[0043] 4.8 g of Zein powder was dissolved in 200 mL of a mixed solvent of 85% ethanol-15% water (v / v) and stirred until completely transparent to prepare a primary solution.

[0044] 400 mL of deionized water was quickly poured into the above primary solution, and stirring was continued at 300 rpm for 30 min; then, a rotary evaporator was used to evaporate ethanol and part of water at 50°C and a speed of 85 rpm to prepare a 1.2 wt% Zein solution.

[0045] 2. Preparation of microcrystalline chitin solution

[0046] Add 100 mL of concentrated hydrochloric acid to 300 mL of water to prepare a 3M hydrochloric acid solution.

[0047] Dissolve 8g of chitin in the above hydrochloric acid solution and boil in a water bath for 1.5h with stirring. After boiling, centrifuge at 6000r / min for 20min, filter to obtain solid, wash the solid twice with water, filter and centrifuge again, add 400mL of deionized water to the solid, and finally homogenize under high pressure at 30MPa for 5min to obtain a 20g / mL microcrystalline chitin solution, which is then stored in a refrigerator for later use.

[0048] 3. Preparation of Zein-CNCs complex

[0049] The zein solution and microcrystalline chitin solution prepared above were mixed and then mixed to prepare soluble complexes, complex aggregates and precipitates of Zein-CNCs under pH conditions of 5.5, 6.0, 6.5, 7.5 and 8.5, respectively. The final concentration of CNCs in each complex was controlled to be 0.75 wt%, and the mass ratio of CNCs to Zein was 1:1.

[0050] Morphological analysis of Zein-CNCs composites prepared at different pH conditions was performed using field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For SEM, observations were obtained using a TESCAN MIRA SEM. For TEM, a 200-fold diluted suspension of the composite was dropped onto a copper microgrid with a carbon-coated film and detected using a JEOL 2100 TEM at 200 kV. The JEOL 2100 TEM was equipped with a video rate camera for real-time imaging and a slow-scan CCD camera for the final image. Results are shown in [Figure number missing]. Figure 1 .

[0051] Depend on Figure 1 As can be seen from A, unlike traditional chitin nanofibers, the microcrystalline chitin CNCs prepared in this embodiment are produced by removing the disordered structure of chitin through surface exfoliation and strong chemical treatment with acid. Therefore, at the microscale, they exhibit a "short and fine needle-like" crystalline structure. Furthermore, as the pH increases, the crystals merge at the boundaries, forming microcrystalline chitin with a "conjoined structure" (see [reference]). Figure 1 A); Correspondingly, Figure 1 B illustrates the principle of the "conjoined structure." Under alkaline conditions, the crystals of CNCs interact with each other, and at their intersection points, they merge to form a "conjoined structure," i.e., intertwined crystal layers with stronger rigidity. Figure 1C It can be seen that the globular shape represents Zein, and the needle and film shape represents CNCs; it is first observed that CNCs are combined in the form of covering the surface of Zein; for the soluble complex (pH 5.5 and 6.0), the needle structure of CNCs is obvious, and there are large gaps between individual complex particles; for the complex coacervate (pH 6.5 and 7.5), CNCs appear in the form of film due to the merging of needle-like "palmate connection", and cover the surface of Zein small balls, while particle aggregation connection occurs. For the precipitate (i.e. insoluble complex, pH 8.5), the film formation is intensified and even Zein cannot be seen. Thus, it is proved that the "palmate structure" of the microcrystalline chitin (CNCs) prepared in this embodiment is generated, and Zein and CNCs are combined in the form of CNCs covering Zein, and the difference between the soluble complex, the complex coacervate and the precipitate.

[0052] Example 2

[0053] The preparation method of the high internal phase Pickering emulsion gel of this embodiment is as follows:

[0054] 1. Preparation of Zein solution

[0055] 4.8 g of Zein powder was dissolved in 200 mL of a mixed solvent of 85% ethanol-15% water (v / v), and stirred until completely transparent to prepare a primary solution.

[0056] 400 mL of deionized water was quickly poured into the above-mentioned primary solution, and stirred at 300 rpm for 30 min; then, an ethanol and part of water were evaporated at 50°C using a rotary evaporator at a speed of 85 rpm to prepare a 1.2 wt% Zein solution.

[0057] 2. Preparation of microcrystalline chitin solution

[0058] 100 mL of concentrated hydrochloric acid was added to 300 mL of water to prepare a 3M hydrochloric acid solution.

[0059] 8 g of chitin was dissolved in the above-mentioned hydrochloric acid solution, and boiled in a water bath for 1.5 h with stirring; after the boiling water bath was completed, centrifugation was performed at 6000 r / min for 20 min, and the solid was obtained by suction filtration, and the solid was washed with water twice, and after re-centrifugation by suction filtration, 400 mL of deionized water was added to the solid, and finally high-pressure homogenization was performed at 30 MPa for 5 min to prepare a 20 g / mL microcrystalline chitin solution, which was stored in a refrigerator for standby.

[0060] 3. Preparation of Zein-CNCs complex (soluble complex / complex coacervate)

[0061] The above prepared Zein solution and microcrystalline chitin solution were mixed to prepare soluble complex and coacervate of Zein-CNCs at pH 5.5, 6.0 and 6.5, 7.5, respectively, and the final concentration of CNCs in the above complexes was controlled at 0.75wt%, and the mass ratio of CNCs to Zein was 1:1.

[0062] 4. Preparation of high internal phase Pickering emulsion gel and coacervate high internal phase Pickering emulsion gel

[0063] 12g of MCT oil and 3g of Zein-CNCs soluble complex, and 12g of MCT oil and 3g of Zein-CNCs coacervate were added to 50mL centrifuge tubes, respectively, and sheared at a speed of 8000rpm for 120s using an Ultra-Turrax T10 homogenizer to prepare high internal phase Pickering emulsion gel (HIPPE gel) and coacervate high internal phase Pickering emulsion gel (co-HIPPE gel), respectively.

[0064] The microstructure of HIPPE gel and co-HIPPE gel was studied by LSM 800 laser confocal (CLSM). First, the fluorescent dyes Nile Red (0.2mg / mL, labeled as oil), Nile Blue (1mg / mL, labeled as Zein) and FITC (1mg / mL, labeled as CNCs) were mixed, 30μL of the mixed dye was mixed with 1mL of fresh emulsion for staining, and further 30μL of the stained emulsion was taken and added to a confocal culture dish; then, the Ar / K and He / Ne dual-channel lasers were excited at 488nm and 633nm, respectively, to obtain the overlapped CLSM images, and finally the images were smoothed and scale marked using ZEN software; the results are shown in Figure 2 .

[0065] The microstructure of the emulsion was observed by laser confocal 10X, 63X and 126X. From Figure 2It can be seen that the droplet size of co-HIPPE gel is obviously smaller than that of HIPPE gel under 10X, and especially, there is thick barrier between the co-HIPPE gel droplets, and the droplets are tightly packed to form a honeycomb-like structure; further, the difference between the two can be observed under 63X and 126X, for the HIPPE gel stabilized by soluble complex, part of the protein and polysaccharide complex exists in the form of free in the continuous phase, and the other part is adsorbed on the oil-water interface; for the co-HIPPE gel stabilized by complex coacervate, there is a thick and sticky protein polysaccharide complex coacervate between the droplets, and no complex is found in the continuous phase. The above phenomena show that, unlike the traditional and conventional HIPPE gel, the new coacervate HIPPE gel of the embodiment not only has more protein-polysaccharide adsorbed on the oil-water interface, but also the complex coacervate can form a thick spatial barrier to hinder the aggregation and collapse of the droplets, and at the same time, a three-dimensional network can be formed, so that the emulsion has a gel-like structure, which will greatly improve the emulsion stability of the high internal phase Pickering emulsion gel.

[0066] The particle size distribution and size of the HIPPE gel and co-HIPPE gel prepared in the embodiment were measured by using Malvern MasterSizer 3000 to evaluate the stability of the emulsion. The refractive indexes of the water phase and MCT oil are 1.33 and 1.44 respectively, and all the measurements were carried out at 25°C for 3 times. Further, the micro-morphology of the emulsion sample was observed by using optical microscope (OP); the results are shown in Figure 3 .

[0067] From Figure 3 A it can be seen that first, the complex prepared at pH 5.5-7.5 can all form HIPPE gel (except pH 8.5, inverted flow); second, the particle size at pH 5.5 is 81.90±0.65 μm, at pH 6.0 is 54.34±1.72 μm, at pH 7.5 is 49.58±0.78 μm and at pH 6.5 is 47.58±1.04 μm, which shows that the particle size of the co-HIPPE gel stabilized by complex coacervate is smaller than that of the HIPPE gel stabilized by soluble complex. In addition, the HIPPE gel at pH 5.5 shows a double peak, and the others are uniform single peak. The above results show that the co-HIPPE gel stabilized by complex coacervate has better stability. Further, from Figure 3 B, the macro-morphology of the emulsion under the fixed model can be observed (see Figure 3Microstructure under optical microscope; first, the particle size of HIPPE gel at pH 5.5 was obviously the largest, and the shape collapsed with oil exuding around, and it was slightly improved at pH 6.0; but for co-HIPPE gel, not only the shape was stable, but also the particle size was smaller, which was consistent with the trend of particle size distribution. The above results confirmed that the co-HIPPE gel prepared in this example had stronger plasticity, which embodied its superior gel properties.

[0068] The freshly prepared emulsion samples were divided into 50 mL centrifuge tubes, and the oil oxidation was accelerated in a 50°C oven and cultured in the dark. At different time intervals, 0.3 mL of sample was added to 1.5 mL of a mixture of isooctane-isopropyl alcohol (3:1, v / v) and vortexed, then centrifuged at 1000g for 2 min, repeated three times. Then 0.2 mL of supernatant organic phase was taken and added to 2.8 mL of a mixture of methanol-n-butanol (2:1, v / v), and 15 μL of 3.94 M potassium thiocyanate, 7.5 μL of 0.132 M barium chloride and 7.5 μL of 0.144 M ferrous sulfate were quickly added. After 20 min of reaction in the dark, the absorbance at 510 nm was measured by ultraviolet spectrophotometry. The content of primary metabolite hydrogen peroxide was calculated according to the standard curve of hydrogen peroxide y=0.0015x+0.0151 (R2=0.99). All reagents were prepared fresh and used, and three parallel determinations were made; the results are shown in Table 2. Figure 4 .

[0069] The lipid oxidation stability of the emulsion is an important indicator to measure the quality of food, and the lipid oxidation stability of the emulsion is evaluated by the formation of primary oxidation products (POV) in the accelerated oxidation process. From Figure 4 It can be seen that first, the POV values of the HIPPE gel and the co-HIPPE gel of this example are lower than those of the naked pure oil, indicating that the HIPPE gel and the co-HIPPE gel prepared in this example are a good encapsulation system. Further, the co-HIPPE gel stabilized by complex coacervate is less than the HIPPE gel stabilized by soluble complex in 15 days, because compared with the soluble complex, the complex coacervate is basically adsorbed on the oil-water interface and forms a three-dimensional network structure of the coacervate barrier layer between the emulsion droplets, which hinders the entry of free radicals in the chain reaction, thereby inhibiting the lipid oxidation of the emulsion. In addition, the presence of the coacervate barrier also prevents the interaction between oxygen and lipids in the emulsion, thereby interrupting the peroxidation process. Among them, the primary oxidation product of the co-HIPPE gel is less than 20 mmol / kg after 15 days of storage, and the rate of oil oxidation is significantly lower than that of the prior art (for example, the primary oxidation product of the ZCPs-ChNFs complex stabilized high internal phase emulsion gel of CN111808301A is as high as 200 mmol / kg after 15 days of storage).

[0070] Example 3

[0071] The preparation method of the flavor HIPPE gel of the present embodiment is as follows:

[0072] 1. Preparation of Zein solution

[0073] 4.8 g of Zein powder was dissolved in 200 mL of a mixed solvent of 85% ethanol-15% water (v / v) and stirred until completely transparent to prepare a primary solution.

[0074] 400 mL of deionized water was quickly poured into the above primary solution and stirred at 300 rpm for 30 min; then, the ethanol and part of the water were evaporated at 50°C using a rotary evaporator at a speed of 85 rpm to prepare a 1.2 wt% Zein solution.

[0075] 2. Preparation of microcrystalline chitin solution

[0076] 100 mL of concentrated hydrochloric acid was added to 300 mL of water to prepare a 3M hydrochloric acid solution.

[0077] 8 g of chitin was dissolved in the above hydrochloric acid solution and boiled in a water bath for 1.5 h with stirring; after the boiling water bath was completed, centrifugation was performed at 6000 r / min for 20 min, and the solid was obtained by suction filtration, washed with water twice, and then re-centrifuged after suction filtration. Finally, 400 mL of deionized water was added to the solid, and high-pressure homogenization was performed at 30 MPa for 5 min to prepare a 20 g / mL microcrystalline chitin solution, which was stored in a refrigerator for standby use.

[0078] 3. Preparation of Zein-CNCs soluble complex and Zein-CNCs complex coacervate

[0079] The above prepared Zein solution and microcrystalline chitin solution were mixed to prepare Zein-CNCs soluble complex and Zein-CNCs complex coacervate at pH values of 5.5, 6.0, and 6.5, 7.5, respectively. The final concentration of CNCs in the above complexes was controlled to be 0.75 wt%, and the mass ratio of CNCs to Zein was 1:1.

[0080] 4. Preparation of flavor HIPPE gel and flavor co-HIPPE gel

[0081] Diacetyl, 2-pentanone, 2-heptanone, ethyl hexanoate, and D-limonene were mixed with 500 g of MCT oil to prepare flavor oil, and the final concentrations of each flavor substance in the oil phase were controlled as follows: diacetyl 600 mg / L, 2-pentanone 250 mg / L, 2-heptanone 1200 mg / L, ethyl hexanoate 3000 mg / L, and D-limonene 3000 mg / L.

[0082] The above 12 g flavor oil and 3 g of Zein-CNCs soluble complex, and 12 g flavor oil and 3 g of Zein-CNCs co-aggomeration were added into 50 mL centrifuge tubes, respectively, and sheared by an Ultra-Turrax T10 homogenizer at a speed of 8000 rpm for 120 s to prepare flavor HIPPE gel and flavor co-HIPPE gel, respectively.

[0083] The flavor HIPPE gel and flavor co-HIPPE gel were detected by static headspace method, as follows:

[0084] 2 g of emulsion sample was sucked into a 20 mL headspace vial and immediately sealed with a cap, and stored at 4℃ for 24 h to ensure flavor equilibrium. In the formal experiment, the headspace vial was placed in an Agilent 7690A headspace sample box, and after equilibration at 75℃ for 10 min, 1 μL of the headspace gas in the vial was automatically sucked by the instrument and injected into an Agilent 7898B gas chromatograph for measurement. The gas chromatograph used a HP-5 capillary column (30 m, 0.32 mm inner diameter, 0.25 mm film thickness) and was equipped with a flame ionization detector (FID). The nitrogen carrier gas flow was 1.8 mL / min under split mode (15:1). The injector and FID temperatures were both 250℃. The nitrogen carrier gas flow was 1.1 mL / min. The temperature program was as follows: 75℃ (0.2 min), 80℃ (20℃ / min, 0.2 min), 85℃ (20℃ / min, 1 min), 90℃ (40℃ / min, 0.2 min), and 180℃ (40℃ / min). The partition coefficient (K A / E ) of the gas phase and the emulsion was calculated according to the following formula:

[0085]

[0086] Wherein: C A is the headspace flavor concentration, and C E is the emulsion flavor concentration. The results are shown in Table 1.

[0087] Table 1

[0088]

[0089] The above experiment uses five volatile compounds, namely diacetyl (C4, Log P = -1.43), pentanone (C5, Log P = 0.91), heptanone (C7, Log P = 1.97), ethyl hexanoate (C8, Log P = 2.83), d-limonene (C8, Log P = 4.43); wherein, the hydrophobicity can be represented by the hydrophobic constant LogP value, and the experience is taken as 1.8 as the boundary, and greater than 1.8 represents strong hydrophobicity, and the greater represents the stronger hydrophobicity of the flavor, it can be seen that diacetyl and pentanone are hydrophilic, and heptanone, ethyl hexanoate and d-limonene are hydrophobic.

[0090] Table 1 gives the K A / E values of the five volatile compounds in the flavor HIPPE gel and the flavor co-HIPPE gel. The flavor release is a process of passing through the dispersed phase to the interface, the interface to the continuous phase, and then to the air. First, for each volatile substance, the K A / E value of the hydrophilic compound is generally significantly higher than that of the hydrophobic compound, especially at heptanone, which sharply decreases, because the hydrophobic flavor tends to exist in the inner layer of the dispersed phase, so the release amount is low. Secondly, the K A / E value of the co-HIPPE gel stabilized by the coacervate is significantly lower than that of the flavor HIPPE gel stabilized by the soluble complex; on the one hand, the co-HIPPE gel has a thick coacervate layer, which will prolong the release of the flavor to the air, so the release amount is low. Secondly, the flavor, especially the hydrophobic flavor, is easy to interact with the hydrophobic Zein at the oil-water interface, and the protein-polysaccharide coacervate in the co-HIPPE gel is more adsorbed on the oil-water interface, so this will intercept a part of the flavor release, thereby making the K A / E value of the co-HIPPE gel lower, which also indicates that the flavor has the strongest affinity with it. Finally, the flavor co-HIPPE gel of the present embodiment has a flavor substance loading amount as high as 3000 mg / L, which is much higher than the loading amount of 500 mg / L of the flavor substance by the whey protein isolate-pectin complex in the prior art.

[0091] In addition, the flavor HIPPE gel and the flavor co-HIPPE gel are detected by a dynamic headspace method, and the method is as follows:

[0092] Prior to the assay, artificial simulated saliva was prepared with the following formulation: KCI 0.9 g / L, NaSCN 0.17 g / L, KH2PO4 1.0 g / L, Na2SO4 1.3 g / L, NaHCO3 1.7 g / L, NaCI 0.3 g / L, CaCI2 0.11 g / L, urea 0.2 g / L and mucin 0.025 g / L, which were added to a pH 7.2 PBS solution and stirred until homogeneous. For the actual measurement, 10 g of the flavour emulsion sample and 10 mL of the artificial saliva were added to the oronasal cavity model apparatus, which was pre-equilibrated in a water bath circulating at 37 °C, and the rotor was added, covered with a sealing film and quickly sealed. The model was kept at 37 °C by water bath circulation throughout the entire test time. Stirring was performed with a magnetic stirrer at 250 r / min. At each test time, 1.0 mL of headspace gas was withdrawn from the model using a 2.5 mL constant temperature SGE GC syringe (Trajan Science Australia Pty Ltd, Australia) and injected quickly into the inlet of an Agilent 7890B gas chromatograph.

[0093] Release theoretical mathematical model: The mathematical model describing the release of aroma can be explained using the mathematical model proposed by Harrison et al. to describe the release of flavour from an aqueous solution containing flavour-binding polymers. The transport of volatile substances through the gas-liquid interface can be described using the penetration theory of interfacial mass transfer, assuming the following equation.

[0094]

[0095] where c g(t) represents the release concentration (mg.cm -3 ) at time t, c e(0) represents the initial flavour concentration (mg.cm -3 ), K ge is the partition coefficient, v g and v e represent the volume of flavour and solution (cm 3 ), respectively, h D is the interfacial mass transfer coefficient (m.s -1 ), and A ge represents the gas-liquid contact area (cm 2 ).

[0096] The results are shown in Figure 5 and Table 2.

[0097] Table 2

[0098]

[0099] Flavor release rate is defined as the migration of flavor molecules from one environment / state to another environment / state within a certain time. Monitoring the release rate of flavor and aroma compounds is very necessary for food production, because consumers can perceive the taste and quality of food before direct consumption. Among them, controllable release and stability are the basic characteristics of embedding system, and controllable release can ensure that flavor compounds are released at a specific rate for a long time, reducing the loss of core compounds during processing operations. In the above experiment, the headspace air of the sample was extracted at a fixed time to monitor the release of flavor in real time through the oral-nasal device and continuous mechanical stirring, and further use the mathematical model proposed by Harrison et al. to compare the flavor release. According to the Harrison mathematical model, the results of nonlinear fitting are shown in Figure 5 Further combining the above formula, the specific data of initial release rate, mass transfer coefficient and correlation are shown in Table 2.

[0100] Firstly, the fitting correlation coefficients of flavor HIPPE gel and flavor co-HIPPE gel at different flavors and different pH values are all greater than 0.97, which shows that the data is reliable. Secondly, for the initial release rate, the hydrophilic flavor is one order of magnitude larger than the hydrophobic flavor, because the hydrophilic flavor is more inclined to the interface layer and is most easily released after mechanical stirring, while the hydrophobic flavor is located in the innermost layer of the structure and is less affected by mechanical stirring. In addition, the v (t) values of flavor co-HIPPE gel stabilized by coacervate are significantly lower than those of flavor HIPPE gel stabilized by soluble complex, which is due to the dense coacervate layer adsorbed at the oil-water interface in co-HIPPE gel. The coacervate layer can delay the release of flavor caused by the destruction of the structure by mechanical stirring, and the time of flavor from oil phase to air will be longer, so it effectively hinders the release of flavor substances and realizes the long-term controlled release of flavor substances. Finally, the corresponding mass transfer coefficient h D has the same trend as v (t) , which proves the correctness of the above conclusion.

[0101] Comparative Example 1

[0102] Except that the corn alcohol-soluble protein hydrolysate-microcrystalline chitin (ZH-CNW) complex prepared by CN 113527712 A embodiment 1 is used to replace the Zein-CNCs complex of embodiment 2, the rest is basically the same as embodiment 2.

[0103] From Figure 6It can be seen that the ZH-CNW composite cannot form stable high internal phase emulsion gel under the condition of embedding 80wt% oil (MCT oil 12g, ZH-CNW composite 3g), which shows strong fluidity, cannot be shaped into semi-solid state, and the particle size is uneven and large; while the co-HIPPE gel stabilized by the Zein-CNCs complex coacervate prepared in Example 2 does not flow when inverted, and has stronger plasticity, indicating that the co-HIPPE gel prepared in Example 2 has significantly improved viscoelasticity, and the emulsion particle size is significantly reduced, indicating that the co-HIPPE gel prepared in Example 2 has better stability.

[0104] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for the preparation of a high internal phase Pickering emulsion gel, characterized in that, The method comprises the following steps: S1: respectively preparing a zein solution and a microcrystalline chitin solution; S2: preparing a Zein-CNCs complex from the zein solution and the microcrystalline chitin solution at pH 6.5-7.5; S3: mixing the MCT oil with the Zein-CNCs complex at a mass ratio of (10-15):3, homogenizing, and preparing a high internal phase Pickering emulsion gel; In step S1, the preparation method of the zein solution comprises: A) dissolving the zein in a mixed solvent of ethanol and water, stirring until completely transparent, and preparing a primary solution; B) quickly adding deionized water to the primary solution, stirring, and then evaporating ethanol and part of the water to obtain a zein solution with a mass content of 1-1.5 wt%; wherein the volume content of ethanol in the mixed solvent is 80-90%; the ratio of the amount of zein, mixed solvent and deionized water is 1g:40-45 mL:80-85 mL; and the stirring speed is 250-350 rpm and the stirring time is 25-35 min; The preparation method of the microcrystalline chitin solution comprises: A) dissolving chitin in a hydrochloric acid solution, performing a boiling water bath under stirring, and then centrifuging, washing, and collecting the solid; B) adding deionized water to the solid for high-pressure homogenization to prepare a microcrystalline chitin solution with a mass concentration of 18-22 mg / mL; wherein the concentration of the hydrochloric acid solution is 2.5-3.5 M; the boiling water bath time is 1-2 h; the ratio of the amount of chitin, hydrochloric acid solution and deionized water is 1g:45-55 mL:45-55 mL; the high-pressure homogenization is performed at 25-35 MPa, and the high-pressure homogenization time is 4-6 min; In step S2, the mass content of microcrystalline chitin in the Zein-CNCs complex is controlled to be 0.7-0.8 wt%, and the mass ratio of microcrystalline chitin to zein is 1:(1-3); In step S3, the homogenization comprises: homogenizing at 8000-15000 rpm for 60-120 s.

2. The production method according to claim 1, characterized by, In step S3, before mixing, the functional substance is first mixed with the MCT oil, and then mixed with the Zein-CNCs complex at a mass ratio of (10-12):3 and homogenized.

3. The production method according to claim 2, characterized by, The functional substance is a flavoring substance.

4. The production method according to claim 3, characterized by, The flavoring substance is selected from at least one of diacetyl, 2-pentanone, 2-heptanone, ethyl hexanoate and D-limonene.

5. The production method according to claim 4, characterized by, The mass concentration of diacetyl in the MCT oil is 500-600 mg / L; the mass concentration of 2-pentanone in the MCT oil is 200-250 mg / L; the mass concentration of 2-heptanone in the MCT oil is 1000-1200 mg / L; the mass concentration of ethyl hexanoate in the MCT oil is 2800-3000 mg / L; and the mass concentration of D-limonene in the MCT oil is 2800-3000 mg / L.

6. A high internal phase Pickering emulsion gel, characterized in that, The high internal phase Pickering emulsion gel is prepared according to any one of the preparation methods of claims 1-5.

7. Use of the high internal phase Pickering emulsion gel of claim 6 in controlled release of flavoring substances.

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