Pickering emulsion

Abstract

The invention discloses Pickering emulsion, and belongs to the technical field of food processing. The Pickering emulsion comprises an emulsifier, wherein the emulsifier is composed of hemicellulose and pectin; the hemicellulose and the pectin are extracted from shaddock peel; a Fourier transform infrared spectrometer is used for collecting the spectrum of the emulsifier, recording and scanning are carried out at the resolution ratio of 2 cm <-1 > in the range of 4000-400 cm <-1 >, and the Fourier infrared spectrum absorption peak of the emulsifier is widened at the position of 1100 cm <-1 >. The Pickering emulsifier is applied to food processing, solves the problem that the existing emulsifier has poor stability to Pickering emulsion, and has the characteristics of good stability, environmental protection and no harm.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to a Pickering emulsion. Background Art

[0002] Pickering emulsions are a special class of multiphase systems characterized by the irreversible adsorption of solid particles at the oil-water interface, which firmly fixes them and forms a mechanical barrier that effectively prevents droplet coalescence. Recent studies have demonstrated the potential of Pickering emulsions in various applications, including edible coatings, fat substitutes, pharmaceuticals, and 3D food printing. The stability of these emulsions is a key factor in product quality and safety. Traditionally, the preparation of Pickering emulsions mainly uses inorganic particles such as silica, titanium dioxide, barium sulfate, and latex particles. Although these particulate surfactants have certain stability, they may also have harmful effects on the environment and human health. For example, although silica particles have been approved as an additive for the food industry, their contact with intestinal epithelial cells may cause adverse effects on the gastrointestinal tract and other organs. Therefore, it is of great practical significance to develop innovative, environmentally friendly, and efficient stabilizers for Pickering emulsions.

[0003] As one of the most widely grown and consumed fruits in the world, grapefruit peel is rich in polysaccharides such as hemicellulose and pectin. Hemicellulose is mainly composed of neutral sugars such as xylan, glucan, and arabinoxylan. It is a biodegradable natural polysaccharide, and its content in plant cell walls is second only to cellulose. Its long-chain structure helps to form a protective layer at the oil-water interface to stabilize Pickering emulsions. However, the abundant hydroxyl groups lead to high hydrophilicity, which limits the application of hemicellulose as an emulsifier. Pectin is mainly composed of homogalacturonic acid (HG), rhamnogalacturonic acid I (RG-I), and rhamnogalacturonic acid II (RG-II). Due to the large number of hydroxyl and carboxyl groups, pectin is highly hydrophilic and has poor stability in Pickering emulsions as an emulsifier. Summary of the invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is the poor stability of the existing emulsifiers on Pickering emulsions, and a Pickering emulsion with good stability, environmental protection and no harm is proposed.

[0005] In order to solve the technical problem, the technical solution adopted by the present invention is:

[0006] The invention provides a Pickering emulsion, comprising an emulsifier, wherein the emulsifier is composed of hemicellulose and pectin; the hemicellulose and the pectin are both extracted from grapefruit peel; a spectrum of the emulsifier is collected by using a Fourier transform infrared spectrometer, and the spectrum is obtained at 4000-400 cm -1 Within 2cm -1The Fourier transform infrared spectrum absorption peak of the emulsifier is at 1100 cm -1 Become wider.

[0007] Preferably, the mass ratio of the hemicellulose to the pectin in the emulsifier is 1:1.

[0008] Preferably, the mass concentration of the emulsifier in the Pickering emulsion is 0.5-2%.

[0009] Preferably, the Pickering emulsion is prepared by the following method: preparing an emulsifier water suspension with a concentration of 1%, rotating and stirring, and then heating at 100°C; taking the emulsifier water suspension, adding corn oil, and shearing with a high-speed dispersing homogenizer to obtain the Pickering emulsion.

[0010] Preferably, the mass ratio of the hemicellulose and the pectin in the emulsifier is 1:1, and the volume ratio of the emulsifier water suspension to the corn oil is 9:1.

[0011] Preferably, the mixture is stirred with rotation for 12 h and then heated at 100° C. for 30 min.

[0012] Preferably, the mixture is sheared at 1200 rpm for 3 min using a high-speed dispersing homogenizer.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The invention provides a Pickering emulsion, which uses a combination of hemicellulose and pectin as an emulsifier and has the characteristics of good stability, being green, environmentally friendly and harmless, and having a simple preparation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the contact angle diagram;

[0016] Figure 2 is the Fourier infrared transform image;

[0017] Figure 3 This is the appearance diagram of Pickering emulsion stability;

[0018] Figure 4 This is an electron micrograph of a Pickering emulsion;

[0019] Figure 5 This is the laser confocal image of the Pickering emulsion. DETAILED DESCRIPTION

[0020] The technical scheme in the specific embodiment of the present invention is described in detail and completely below. Obviously, the described embodiment is only a part of the specific implementation of the overall technical scheme of the present invention, rather than all implementations. Based on the overall concept of the present invention, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the present invention.

[0021] The invention provides a Pickering emulsion, comprising an emulsifier, wherein the emulsifier is composed of hemicellulose and pectin; the hemicellulose and the pectin are both extracted from grapefruit peel; a spectrum of the emulsifier is collected by using a Fourier transform infrared spectrometer, and the spectrum is obtained at 4000-400 cm -1 Within 2cm -1 The Fourier transform infrared spectrum absorption peak of the emulsifier is at 1100 cm -1 It becomes wider. The Pickering emulsion uses a combination of hemicellulose and pectin as an emulsifier, and has the characteristics of good stability, green environmental protection, no harm, and a simple preparation method. It should be noted that the technical solution defines that the emulsifier is composed of hemicellulose and pectin, and the hemicellulose and pectin are both extracted from grapefruit peel. The emulsifier composed of hemicellulose and pectin extracted from grapefruit peel has better compatibility, and the contact angle of the emulsifier composed of hemicellulose and pectin is 89.2° (when the oil-water interface contact angle is close to 90°, it is an ideal stabilizer for Pickering emulsion, when it is greater than 90°, it is hydrophobic, and when it is less than 90°, it is hydrophilic). The technical solution further defines the Fourier infrared spectral characteristics of the emulsifier composed of hemicellulose and pectin under certain test conditions. Only emulsifiers that meet the Fourier infrared spectral characteristics can overcome the defect that hemicellulose and pectin cannot be used as Pickering emulsion emulsifiers due to their high hydrophilicity.

[0022] Literature reports that the combination of hemicellulose and pectin with protein can improve the stabilizing effect on Pickering emulsions. The emulsifying effect is improved by covalently bonding hemicellulose to soy protein isolate through amino and carbonyl groups. Alternatively, an electrostatic complex is formed by the interaction between ovalbumin and pectin to improve the functional properties of pectin for high internal phase Pickering emulsions under extreme conditions. There are also many studies that combine pectin and hemicellulose with protein to improve the film-forming and gelling properties of polysaccharides. The performance of polysaccharides is improved by forming a polysaccharide-protein complex, and this combination draws on the natural phenomenon of the interaction between the two in plant cell walls. However, the synergistic stabilizing effect and stabilizing mechanism of the complex between hemicellulose and pectin on Pickering emulsions have not been systematically studied. The above technical scheme of the present invention limits the sources and characteristics of hemicellulose and pectin, thereby ensuring their stabilizing effect on Pickering emulsions without the need for protein. The present invention prepares Pickering emulsion by compounding hemicellulose and pectin, evaluates the stabilizing effect of the emulsion by measuring storage stability, laser confocal microscopy, electron microscopy, water-in-oil characteristics, diffusion time in water phase, and environmental stability, and finds that compounding hemicellulose and pectin can synergistically improve the stability of Pickering emulsion. The present invention is applied to stabilizing emulsions, solves the problem of poor emulsification effect when hemicellulose and pectin are used alone as emulsifiers, and can significantly improve the synergistic stabilizing effect on Pickering emulsions.

[0023] The present invention uses grapefruit hemicellulose and pectin as raw materials to prepare Pickering emulsion, has a simple process, low production cost of grapefruit hemicellulose and pectin, protects the environment, and realizes high-value utilization of grapefruit resources. The preparation of Pickering emulsion after compounding can significantly alleviate the shortcomings of hemicellulose and pectin when used alone as emulsifiers, and has a synergistic stabilizing effect on Pickering emulsion.

[0024] In a preferred embodiment, the mass ratio of the hemicellulose to the pectin in the emulsifier is 1: 1. The technical solution specifically defines the mass ratio of hemicellulose to pectin in the emulsifier as 1: 1, because when the mass of hemicellulose and pectin are equal, this specific ratio can optimize the performance of the emulsifier.

[0025] In a preferred embodiment, the mass concentration of the emulsifier in the Pickering emulsion is 0.5-2%. The technical solution specifically limits the mass concentration of the emulsifier in the Pickering emulsion because the mass concentration of the emulsifier has a significant effect on the stability and performance of the Pickering emulsion. When the mass concentration of the emulsifier is in the range of 0.5-2%, it can ensure that there are enough emulsifier particles between the emulsion droplets adsorbed on the oil-water interface to form a stable protective layer, thereby effectively preventing the merging and aggregation of the droplets and improving the stability of the emulsion. In addition, this concentration range also helps to control the size and distribution of the emulsion droplets, making them uniform and small, which is crucial for the sensory properties and functionality of the emulsion in applications such as cosmetics, food, and medicine. .

[0026] In a preferred embodiment, the Pickering emulsion is prepared by the following method: preparing an emulsifier water suspension with a concentration of 1%, heating it at 100°C after rotary stirring; taking the emulsifier water suspension, adding corn oil, and shearing it with a high-speed dispersing homogenizer to obtain the Pickering emulsion. This technical solution limits the heating of the emulsifier water suspension at 100°C after rotary stirring, because heating can promote the dissolution and dispersion of the emulsifier and improve its stability in the water phase. Specifically, rotary stirring can ensure that the emulsifier is evenly distributed in the water phase, while high temperature helps to reduce the viscosity of the emulsifier, making it easier to mix with the oil phase, thereby forming a stable emulsion.

[0027] In a preferred embodiment, the mass ratio of the hemicellulose to the pectin in the emulsifier is 1:1, and the volume ratio of the emulsifier water suspension to the corn oil is 9:1.

[0028] In a preferred embodiment, the mixture is heated at 100° C. for 30 min after being stirred for 12 h.

[0029] In a preferred embodiment, a high-speed dispersing homogenizer is used for shearing at 1200 rpm for 3 minutes.

[0030] In order to more clearly and in detail introduce the Pickering emulsion provided by the embodiments of the present invention, it will be described below in conjunction with specific embodiments.

[0031] Example 1

[0032] (1) Preparation of hemicellulose + pectin: First, a mixture of hemicellulose and pectin with a mass ratio of 1:1 was prepared into an aqueous suspension at a concentration of 1%, and then the suspension was heated at 100°C for 30 minutes after being rotated and stirred for 12 hours;

[0033] (2) Preparation of Pickering emulsion: 90 mL of the above aqueous suspension was added with 10 mL of corn oil, and sheared with a digital high-speed dispersing homogenizer at 1200 rpm for 3 min to obtain a hemicellulose + pectin Pickering emulsion.

[0034] Comparative Example 1

[0035] The preparation method of the Pickering emulsion is as follows:

[0036] Preparation of Pickering emulsion: First prepare a 1% aqueous suspension of cellulose, stir it for 12 hours, and then heat it at 100°C for 30 minutes. Then characterize the sample. Take 90mL of the aqueous suspension, add 10mL of corn oil, and use a high-speed dispersing homogenizer at 1200rpm for 3 minutes to obtain different groups of Pickering emulsions.

[0037] Comparative Example 2

[0038] The preparation method of the Pickering emulsion is as follows:

[0039] Preparation of Pickering emulsion: First prepare a 1% water suspension of hemicellulose, stir it for 12 hours and then heat it at 100°C for 30 minutes. Then characterize the sample. Take 90mL of the water suspension, add 10mL of corn oil, and use a high-speed dispersing homogenizer at 1200rpm for 3 minutes to obtain different groups of Pickering emulsions.

[0040] Comparative Example 3

[0041] The preparation method of the Pickering emulsion is as follows:

[0042] Preparation of Pickering emulsion: First prepare a 1% aqueous suspension of pectin, stir it for 12 hours, and then heat it at 100°C for 30 minutes. Then characterize the sample. Take 90mL of the aqueous suspension, add 10mL of corn oil, and use a high-speed dispersing homogenizer at 1200rpm for 3 minutes to obtain different groups of Pickering emulsions.

[0043] Comparative Example 4

[0044] The preparation method of the Pickering emulsion is as follows:

[0045] Preparation of Pickering emulsion: Cellulose and hemicellulose were mixed in a ratio of 1:1 to prepare a 1% aqueous suspension, which was heated at 100°C for 30 min after rotary stirring for 12 h. The sample was then characterized. 90 mL of the aqueous suspension was taken, 10 mL of corn oil was added, and the mixture was sheared at 1200 rpm for 3 min using a high-speed dispersing homogenizer to obtain different groups of Pickering emulsions.

[0046] Comparative Example 5

[0047] The preparation method of the Pickering emulsion is as follows:

[0048] Preparation of Pickering emulsion: Mix cellulose and pectin in a ratio of 1:1 to prepare a 1% aqueous suspension, stir for 12 hours, and heat at 100°C for 30 minutes. Then characterize the sample. Take 90mL of the aqueous suspension, add 10mL of corn oil, and use a high-speed dispersing homogenizer at 1200rpm for 3 minutes to obtain different groups of Pickering emulsions.

[0049] Comparative Example 6

[0050] The preparation method of the Pickering emulsion is as follows:

[0051] Preparation of Pickering emulsion: Cellulose, hemicellulose and pectin were mixed in a ratio of 1:1:1 to prepare a 1% aqueous suspension, and heated at 100°C for 30 minutes after rotary stirring for 12 hours. The samples were then characterized. 90 mL of the aqueous suspension was taken, 10 mL of corn oil was added, and sheared at 1200 rpm for 3 minutes using a high-speed dispersing homogenizer to obtain different groups of Pickering emulsions.

[0052] Performance Testing

[0053] The emulsifier characterization method is as follows:

[0054] Contact angle characterization: The sample was pressed into a thin sheet, placed in corn oil, and 4 μL of deionized water was added to the surface. After standing for 1 second, the contact angle of the oil-water interface of the sample was measured using a contact angle meter;

[0055] Fourier transform infrared characterization: Hemicellulose, pectin, and hemicellulose + pectin were mixed with 1000 mg of KBr and pressed into thin sheets. Spectra were collected using a Fourier transform infrared spectrometer and the wavelength was 4000-400 cm -1 Within 2cm -1 Resolution records 64 scans.

[0056] The characterization method of Pickering emulsion is as follows:

[0057] (1) Storage stability characterization: The fresh emulsion was placed at 4°C for 24 h and the changes in the emulsion appearance were recorded.

[0058] (2) Laser confocal characterization: Add 20 μL of Nile red (0.01 g / 100 mL isopropanol) staining solution to 1 mL of the emulsion, mix thoroughly, and stain for 5 min in the dark. Then drop the stained sample on a clean glass slide for microscopic observation. The excitation wavelength of Nile red is 488 nm.

[0059] (3) Electron microscopy characterization: A 10 μL droplet of the emulsion was placed on the surface of a glass slide, then covered with a coverslip and observed using a 100x objective lens.

[0060] (3) Characterization of environmental stability: The centrifugal stability of the emulsion was evaluated by centrifuging at 1000 rpm for 3 min in a refrigerated high-speed centrifuge and observing the emulsification of the Pickering emulsion. After adjusting the pH to 2 and pH to 10 using 0.5 M HCl and 0.5 M NaOH solutions, respectively, the emulsion was placed at room temperature for 6 h and the emulsification state was observed to evaluate the pH stability of the Pickering emulsion. The temperature stability of the Pickering emulsion was studied by placing the emulsion at 40°C and 60°C for 3 h and observing the emulsification. The freeze-thaw stability of the Pickering emulsion was evaluated by freezing the emulsion at -20°C for 6 h and thawing it at room temperature for 6 h.

[0061] like Figure 1-5 As shown:

[0062] The contact angle and Fourier transform infrared spectroscopy were characterized as follows:

[0063] When the contact angle of the oil-water interface is close to 90°, it is an ideal stabilizer for Pickering emulsions. When it is greater than 90°, it is hydrophobic, and when it is less than 90°, it is hydrophilic. Cellulose, cellulose + hemicellulose, cellulose + pectin, and cellulose + hemicellulose + pectin with contact angles greater than 100° are all hydrophobic. The contact angles show that hemicellulose (83.2°) is more hydrophilic than pectin (86.6°). The contact angle of cellulose + pectin with a contact angle of 89.2° is closest to 90°, and can better stabilize Pickering emulsions than other samples.

[0064] It can be seen from the Fourier infrared spectrum that after adding pectin, the -OH absorption peaks of cellulose and -1 Move to 3342 and 3329cm - 1, indicating that there may be hydrogen bonding interactions between the samples, which can better improve the stability of the emulsion. The Fourier infrared spectrum absorption peak of hemicellulose and pectin mixed is at 1100 cm -1 This is attributed to the asymmetric stretching vibration of the glycosidic bond COC, which suggests that glycosidic bonds may be formed between hemicellulose and pectin, thereby stabilizing the emulsion.

[0065] The stabilizing effect on Pickering emulsion is as follows:

[0066] For fresh cellulose Pickering emulsions, phase separation occurs very quickly, and fresh hemicellulose Pickering emulsions can form a uniform emulsion system. However, hemicellulose Pickering emulsions showed stratification after 24 hours. Compared with cellulose Pickering emulsions and hemicellulose Pickering emulsions, pectin Pickering emulsions are more stable before and after 24 hours. Interestingly, the stability of cellulose + hemicellulose + pectin Pickering emulsions is weaker than that of hemicellulose + pectin Pickering emulsions. Fresh Pickering emulsions were centrifuged and the temperature was changed to evaluate the stability of Pickering emulsions, and their stability was also observed by adjusting the pH value after standing for 6 hours. After centrifugation, changing the temperature and pH value, cellulose Pickering emulsions showed obvious oil phase precipitation or stratification. Hemicellulose Pickering emulsions will stratify after centrifugation or standing at a temperature exceeding 40°C. Pectin Pickering emulsions are still stable after centrifugation or standing at 40°C for 6 hours, stable under acidic conditions, and stratified under alkaline conditions. Cellulose + hemicellulose Pickering emulsion and cellulose + pectin Pickering emulsion showed obvious stratification when centrifuged, pH value and temperature changed. It is worth mentioning that hemicellulose and pectin Pickering emulsions remained stable after centrifugation, temperature and pH value changes. However, cellulose + hemicellulose + pectin showed obvious stratification under temperature changes and alkaline conditions. In summary, among all the prepared Pickering emulsions, hemicellulose + pectin Pickering emulsion had the best stability.

[0067] From the dispersion of droplets, it can be seen that the droplets of pectin Pickering emulsion are smaller and more uniform than those of cellulose Pickering emulsion and hemicellulose Pickering emulsion, while the droplets of cellulose + hemicellulose Pickering emulsion and cellulose + hemicellulose + pectin Pickering emulsion are larger and more uneven.

Claims

1. A Pickering emulsion comprising an emulsifier, characterized in that The emulsifier is composed of hemicellulose and pectin; the hemicellulose and pectin are both extracted from grapefruit peel; The spectra of the emulsifiers were collected using a Fourier transform infrared spectrometer and the wavelength was 4000-400 cm -1 Within 2cm -1 The Fourier transform infrared spectrum absorption peak of the emulsifier is at 1100 cm -1 Become wider.

2. The Pickering emulsion according to claim 1, characterized in that The mass ratio of the hemicellulose to the pectin in the emulsifier is 1:

1.

3. The Pickering emulsion according to claim 1, characterized in that The mass concentration of the emulsifier in the Pickering emulsion is 0.5-2%.

4. The Pickering emulsion according to claim 1, characterized in that The Pickering emulsion is prepared by the following method: An emulsifier water suspension with a concentration of 1% is prepared, and the suspension is heated at 100° C. after being rotated and stirred; corn oil is added to the emulsifier water suspension, and the suspension is sheared by a high-speed dispersing homogenizer to obtain the Pickering emulsion.

5. The Pickering emulsion according to claim 4, characterized in that The mass ratio of the hemicellulose to the pectin in the emulsifier is 1:1, and the volume ratio of the emulsifier water suspension to the corn oil is 9:

1.

6. The Pickering emulsion according to claim 4, characterized in that The mixture was stirred for 12 h and then heated at 100 °C for 30 min.

7. The Pickering emulsion according to claim 4, characterized in that Use a high-speed dispersing homogenizer to shear for 3 minutes at 1200 rpm.

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