A method for preserving an emulsified meat product

Abstract

The application belongs to the technical field of emulsified meat product preservation, and particularly relates to a Zein-beta-CD composite particle and preparation of a high internal phase Pickering emulsion loaded with clove essential oil. The high internal phase Pickering emulsion loaded with clove essential oil is added to meat products for preservation. The high internal phase Pickering emulsion loaded with clove essential oil is obtained by homogenizing an oil phase of modified Zein-beta-CD particles, clove essential oil and corn oil. The emulsion is added in an amount of 16% of the total amount. The emulsion is safe, can better inhibit the total number of colonies of emulsified meat products during the storage period, slow down the degree of fat oxidation, and improve the quality and shelf life of the emulsified meat products.

Description

Technical Field

[0001] This invention belongs to the field of emulsified meat product preservation technology, specifically relating to the preparation of zein and β-cyclodextrin composite particles and their high internal phase Pickering emulsion loaded with clove oil. Background Technology

[0002] Emulsified meat products are widely available processed meat products on the market. During storage, these products are susceptible to bacterial contamination and protein and fat oxidation, leading to spoilage. Therefore, effectively storing emulsified meat products to extend their shelf life has become a crucial issue that needs to be addressed.

[0003] Preservation methods for emulsified meat products include low temperature, high pressure, active packaging, and synthetic antibacterial or antioxidant agents. These methods inhibit bacterial growth in meat products, achieving the purpose of preservation. However, these preservation methods also have drawbacks, such as short shelf life, limited antibacterial and preservative effects, and the need to be used in conjunction with other methods (e.g., the combined use of high pressure and low temperature can affect the color of meat products). While synthetic antioxidants can inhibit product spoilage, they are harmful to humans and cannot be consumed. Clove essential oil is a natural plant essential oil extracted from the stems, leaves, and buds of the clove tree. It is a pale yellow, transparent liquid with a pungent aroma. The main component of clove essential oil is eugenol, which has antibacterial, antioxidant, and analgesic properties. It has an antibacterial effect on bacteria in some plants and foods, making it a natural preservative that is safe for consumption. Therefore, some scholars at home and abroad have applied clove essential oil to the preservation of various foods, such as fruits, vegetables, and soy products. However, the strong odor, volatility, easy oxidation, and instability of essential oils limit their application in food.

[0004] Currently, plant essential oils can be protected using methods such as particles, microemulsions, liposomes, and microencapsulation. One study used chitosan as the wall material and sodium tripolyphosphate as the cross-linking agent to prepare chitosan-clove essential oil nanocapsules via ionogel for meat product preservation. Results showed that nanoencapsulation of clove essential oil improved its antibacterial and antioxidant properties, allowing meat products to be refrigerated for up to 8 days. Another study used high-internal-phase Pickering emulsions as delivery carriers to encapsulate active substances such as curcumin and carotenoids; however, using high-internal-phase Pickering emulsions as delivery carriers requires selecting suitable emulsifiers to improve carrier stability and the bioavailability of active substances.

[0005] Compared to traditional emulsions stabilized by small-molecule surfactants and natural macromolecules, Pickering emulsions are a novel type of emulsion stabilized by solid particles as emulsifiers. These solid particles can irreversibly adsorb onto the oil-water interface, endowing Pickering emulsions with superior physical and chemical stability, such as resistance to Austronesian ripening, anti-agglomeration, freeze-thaw stability, and resistance to oil oxidation. Furthermore, the amount of solid particles used as emulsifiers can be significantly reduced. Therefore, Pickering emulsions have experienced rapid development in recent years and show strong application prospects in the food, pharmaceutical, and cosmetic industries.

[0006] Food-grade emulsifiers used to prepare Pickering emulsions include proteins (such as prolamins and soy proteins), polysaccharides (such as starch and cellulose), and fats. Single-component raw materials are difficult to form long-term stable emulsions due to their own structure and environmental influences. Utilizing proteins and polysaccharides to prepare emulsifiers through covalent or non-covalent (electrostatic, hydrogen bonding, and hydrophobic interactions) interactions yields composite solid particles with good wetting properties, possessing the beneficial characteristics of two biomacromolecules, thus giving Pickering emulsions better stability. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a method for preserving emulsified meat products using zein-β-cyclodextrin complex particles (Zein-β-CD).

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preserving emulsified meat products involves adding a high internal phase Pickering emulsion loaded with clove essential oil to the meat products for preservation. The high internal phase Pickering emulsion loaded with clove essential oil is obtained by homogenizing modified Zein-β-CD particles with a mixed oil phase of clove essential oil and corn oil. The amount of emulsion added accounts for 16% of the total amount.

[0010] The modified Zein-β-CD particles were obtained by ultrasonic treatment of zein and β-cyclodextrin at pH 7.0.

[0011] The zein protein was mixed with the β-cyclodextrin solution, the pH of the system was adjusted to 11, and the mixture was magnetically stirred for 1 hour. Then, the pH of the system was adjusted to neutral with acid, and the mixture was magnetically stirred for another 15 minutes to obtain the modified Zein-β-CD particles.

[0012] The process involves mixing zein and β-cyclodextrin solution, adjusting the pH of the system to 11 with NaOH, maintaining magnetic stirring for 1 hour, adjusting the pH to 7 with HCl, continuing magnetic stirring for 15 minutes, and then performing ultrasonic treatment to obtain modified Zein-β-CD particles. The ultrasonic settings are: 30 kHz, ultrasonic power 150 W–450 W, operating in a 4-second, 2-second interval mode, for 2–18 minutes. The mass ratio of zein to β-cyclodextrin is 3:1–1:3 (preferably 1:1).

[0013] The β-cyclodextrin solution is prepared by dissolving β-cyclodextrin in distilled water to obtain a 2% (w / w) solution, and then stirring and heating it in a water bath at 40–50°C until it is completely dissolved to obtain a saturated solution.

[0014] The high internal phase Pickering emulsion loaded with clove essential oil is obtained by thoroughly mixing clove essential oil and corn oil as the oil phase, and then homogenizing the oil phase with modified Zein-β-CD particles; wherein, the homogenization conditions are: 12000 r / min, 2 min, and the oil phase accounts for 50% to 80% of the emulsion volume.

[0015] The clove essential oil in the oil phase is dissolved in corn oil, so that the concentration of clove essential oil is 1 mg / mL.

[0016] An emulsified meat product with a long shelf life, comprising, by weight percentage, 60% lean pork, 2% pork fat, 16% ice water, 2% salt, 3% starch, 0.2% compound phosphate, 0.8% carrageenan, and the remainder being the high internal phase Pickering emulsion loaded with clove essential oil.

[0017] Specific preparation:

[0018] Separate the lean pork and fat and cut them into small pieces. Grind each piece separately in a meat grinder for 30 seconds. Divide the minced meat into three groups: a blank group, an essential oil group, and an emulsion group. Add the ingredients according to the proportions, mix well, and then quickly chop and mix for 3 minutes. Shape the mixture into pork patties with a diameter of about 7.5 cm and a thickness of about 2 cm. Bake them in the oven and store them at 4°C.

[0019] The amount of emulsion added is 16%.

[0020] The baking conditions are 180℃ for 20 minutes.

[0021] The principle of this invention is as follows:

[0022] This invention utilizes zein, a naturally hydrophobic protein, dissolved under strong alkaline conditions. Through pH shifting and specific ultrasonic treatment, the internal structure of the zein-β-CD particles is affected, resulting in modified zein-β-CD (as a stabilizer) containing both hydrophobic –C=C– double bonds and hydrophilic hydroxyl groups (-OH), enhancing its hydrophilic and lipophilic properties and thus improving its emulsifying ability. In stabilizing high internal-phase Pickering emulsions, the modified zein-β-CD forms a very dense film at the oil-water interface, preventing emulsion droplet aggregation and maintaining high emulsion stability. The gel network structure formed by the stabilized high internal-phase Pickering emulsion improves the stability of clove oil, enhances its antioxidant properties, and delays its volatilization. The high internal-phase Pickering emulsion loaded with clove oil is used for preserving emulsified meat products, improving product quality and extending shelf life.

[0023] The preparation method and the product obtained by the present invention have the following advantages and beneficial effects:

[0024] 1. This invention utilizes pH shifting and ultrasonic technology to assist in the preparation of Zein-β-CD particles, enhancing the hydrophobicity of β-cyclodextrin. This physical modification is pollution-free, and the preparation process is safe, green, and will not affect human health. Furthermore, the interfacial properties of the particles are significantly improved, exhibiting excellent salt ion tolerance and thermal stability.

[0025] 2. The high internal phase Pickering emulsion prepared by the present invention using pH shift and ultrasound technology to assist in the preparation of Zein-β-CD particles exhibits good antioxidant properties, storage stability, pH stability, ionic stability and thermal stability, making it suitable as a carrier for bioactive ingredients.

[0026] 3. The high internal phase Pickering emulsion prepared by this invention provides a highly stable environment for encapsulating active substances (such as clove oil), improves the bioavailability of active substances, and minimizes the impact on the sensory characteristics of the product.

[0027] 4. The high internal phase Pickering emulsion of loaded clove essential oil prepared by this invention has high stability. When used in the processing and preservation of emulsified meat products, it can improve the texture and sensory quality of meat products and delay oil oxidation and spoilage of meat products.

[0028] 5. The high internal phase Pickering emulsion of loaded clove essential oil prepared by this invention has high stability and has good application prospects in the processing and preservation of emulsified meat products. Attached Figure Description

[0029] Figure 1The graph shows the effect of different ultrasonic powers on the particle size, potential, and dispersibility index of Zein-β-CD particles, as provided in Example 1 of this invention.

[0030] Figure 2 This is a graph showing the effect of different ultrasonic powers on the surface hydrophobicity of Zein-β-CD particles, as provided in Embodiment 1 of the present invention.

[0031] Figure 3 The graph shows the effect of different ultrasonic times on the particle size, potential, and dispersibility index of Zein-β-CD particles, as provided in Example 2 of this invention.

[0032] Figure 4 This is a graph showing the effect of different ultrasonic times on the surface hydrophobicity of Zein-β-CD particles, as provided in Example 2 of the present invention.

[0033] Figure 5 The three-phase contact angles of the Zein-β-CD particles provided in Embodiment 3 of the present invention are shown below; where A is the three-phase contact angle of β-CD; B is the three-phase contact angle of Zein; and C is the three-phase contact angle of Zein-β-CD.

[0034] Figure 6 The ionic stability of the Zein-β-CD particles provided in Example 3 of the present invention is shown in Figure A, where A is the appearance of the emulsion at different ion concentrations, and B is the particle size, potential, and dispersibility index at different ion concentrations.

[0035] Figure 7 The thermal stability of the Zein-β-CD particles provided in Example 3 of the present invention is shown; wherein, A is the appearance of the emulsion at different temperatures; and B is the particle size, potential and dispersibility index at different temperatures.

[0036] Figure 8 This is a graph showing the effect of different oil phase ratios on the particle size of Pickering emulsions, as provided in Example 4 of the present invention.

[0037] Figure 9 This is a diagram showing the effect of different oil phase ratios on the microstructure of Pickering emulsions provided in Example 4 of the present invention.

[0038] Figure 10 This is a graph showing the effect of different oil phase ratios on the rheological properties of Pickering emulsions provided in Example 4 of the present invention; where A is the storage modulus graph and B is the loss modulus graph.

[0039] Figure 11 This is a graph showing the effect of different oil phase ratios on the bioavailability of Pickering emulsions provided in Example 4 of the present invention.

[0040] Figure 12The graph shows the effect of different oil phase ratios on the antioxidant properties of Pickering emulsion provided in Example 4 of the present invention; wherein, A is the scavenging capacity of DPPH and ABTS; B is the scavenging capacity of superoxide anion and hydroxyl radical; C is the graph showing the change in hydroperoxide content; and D is the graph showing the change in malondialdehyde content.

[0041] Figure 13 This is a graph showing the effect of different oil phase ratios on the storage stability of high internal phase Pickering emulsions provided in Example 4 of the present invention.

[0042] Figure 14 The graph shows the effect of the optimal oil phase ratio on the thermal stability of the Pickering emulsion provided in Example 4 of this invention.

[0043] Figure 15 The diagram shows the effect of the optimal oil phase ratio on the ionic stability of the Pickering emulsion provided in Example 4 of this invention.

[0044] Figure 16 The effect of the optimal oil phase ratio on the pH stability of the Pickering emulsion provided in Example 4 of this invention is shown in the figure.

[0045] Figure 17 This is a graph showing the effect of different groups on the texture of pork patties during different storage periods, as provided in Embodiment 5 of the present invention.

[0046] Figure 18 This is a diagram illustrating the effect of different groups on the color difference of pork patties during different storage periods, as provided in Embodiment 5 of the present invention.

[0047] Figure 19 This is a graph showing the effect of different groups on the pH of pork patties during different storage periods, as provided in Example 5 of the present invention.

[0048] Figure 20 This is a graph showing the effect of different groups on TVB-N in pork patties during different storage periods, as provided in Embodiment 5 of the present invention.

[0049] Figure 21 This is a graph showing the effect of different groups on the TBARS of pork patties during different storage periods, as provided in Embodiment 5 of the present invention. Detailed Implementation

[0050] In view of the technical problems existing in the prior art, the experimental scheme of the present invention was proposed after extensive practice. The specific embodiments of the present invention will be further described below with reference to examples. It should be noted that the specific embodiments described herein are only for illustration and explanation of the present invention and are not limited to the present invention.

[0051] This invention employs pH shifting and ultrasonic technology to synthesize zein and β-cyclodextrin into composite particles, thereby improving the amphiphilicity of the composite particles. Clove oil and corn oil are mixed with the prepared Zein-β-CD composite particles and homogenized to obtain a clove oil-loaded high internal phase Pickering emulsion, which is then used for the preservation of emulsified meat products. This invention embeds some or all of the clove oil into the high internal phase Pickering emulsion, reducing its contact with the surrounding environment and increasing its stability, thus better exerting its antibacterial effect. The resulting high internal phase Pickering emulsion exhibits good stability and antioxidant properties. Using the prepared high internal phase Pickering emulsion for the preservation of emulsified meat products achieves antibacterial and antiseptic effects while significantly improving the quality and shelf life of emulsified meat products.

[0052] Example 1

[0053] Weigh 2g of β-cyclodextrin and dissolve it in distilled water to prepare a 2% β-cyclodextrin solution; stir and dissolve at 36℃; weigh 2g of commercially available zein and dissolve it in distilled water to prepare a 2% zein solution.

[0054] The above β-cyclodextrin solution and zein solution were mixed in equal volumes. The pH of the β-cyclodextrin and zein mixture was adjusted to 11 using 1M NaOH. After magnetic stirring for 1 hour, the pH of the mixture was adjusted back to 7 using 1M HCl. Magnetic stirring was continued for 15 minutes. The mixture was then treated with different ultrasonic powers for 10 minutes to obtain zein-β-cyclodextrin composite particles under different ultrasonic powers.

[0055] The instrument used for ultrasound was an ultrasonic cell disruptor (Sonics VCX750 ultrasonic cell disruptor, USA). The parameters were set to 30 kHz, with ultrasonic power set to 150, 225, 300, 375, and 450 W respectively. The ultrasound duration was 10 min, with a 4-second on-time and 2-second intermittent mode. The optimal ultrasonic power was determined by considering particle size, potential, dispersibility index, and surface hydrophobicity. In addition to the cavitation effect of ultrasonic oscillation, the ultrasonic cell disruptor also utilizes shearing, emulsification, and homogenization effects.

[0056] The particle size, potential, dispersibility index, and surface hydrophobicity of the Zein-β-CD particles obtained by the above modification treatment were then tested (see [reference]). Figure 1-2 ).Depend on Figure 1It can be seen that with the increase of ultrasonic power, the effect on Zein-β-CD particle size, potential, and dispersibility index decreases and then increases; when the ultrasonic power reaches 375W, the Zein-β-CD particle size and dispersibility index reach their minimum values, while the potential reaches its maximum value; as the ultrasonic power continues to increase, the particle size begins to increase, while the potential begins to decrease. Figure 2 It can be seen that the effect of ultrasonic power on the hydrophobicity of Zein-β-CD surface also shows a trend of first decreasing and then increasing, with the surface hydrophobicity value being the largest at 375W.

[0057] The data above shows that an ultrasonic power of 375W is the optimal power.

[0058] Example 2

[0059] Weigh 2g of β-cyclodextrin and dissolve it in distilled water to prepare a 2% β-cyclodextrin solution; stir and dissolve at 36℃, and weigh 2g of zein and dissolve it in distilled water to prepare a 2% zein solution.

[0060] Equal volumes of β-cyclodextrin solution and zein solution were mixed. The pH of the β-cyclodextrin-zein mixture was adjusted to 11 using 1M NaOH. After magnetic stirring for 1 hour, the pH was adjusted back to 7 using 1M HCl, and magnetic stirring was continued for another 15 minutes. Subsequently, the mixture was subjected to ultrasonic treatment at 375W for different times to obtain zein-β-cyclodextrin composite particles with different ultrasonic treatment times.

[0061] The instrument used for ultrasound was an ultrasonic cell disruptor (Sonics VCX750 ultrasonic cell disruptor, USA). The parameters were set to 30 kHz, and the ultrasound times were set to 2 min, 6 min, 10 min, 14 min, and 18 min, respectively. The ultrasound power was 375 W, with a 4-second operation and a 2-second interval mode. The optimal ultrasound time was determined by considering particle size, potential, dispersibility index, and surface hydrophobicity.

[0062] The particle size, potential, dispersibility index, and surface hydrophobicity of the Zein-β-CD particles obtained by the above modification treatment were then tested (see [reference]). Figure 3-4 ).Depend on Figure 3 It can be seen that with increasing ultrasonic time, the effects on Zein-β-CD particle size, potential, and dispersibility index decrease and then increase; when the ultrasonic time reaches 14 min, the Zein-β-CD particle size and dispersibility index reach their minimum values, while the potential reaches its maximum value; as the ultrasonic time continues to increase, the particle size begins to increase, while the potential begins to decrease. Figure 4 It can be seen that the effect of ultrasonic time on the hydrophobicity of Zein-β-CD surface shows a trend of first increasing and then decreasing, with the surface hydrophobicity value being the largest at 14 min.

[0063] Based on the above data, an ultrasonic time of 14 minutes is optimal. That is, when the ultrasonic power is 375W and the ultrasonic reaction time is 14 minutes, the prepared Zein-β-CD particles have the smallest particle size, the largest absolute potential value, and the best hydrophobicity.

[0064] Example 3

[0065] Weigh 2g of β-cyclodextrin and dissolve it in distilled water to prepare a 2% β-cyclodextrin solution; stir and dissolve at 36℃, and weigh 2g of zein and dissolve it in distilled water to prepare a 2% zein solution.

[0066] Equal volumes of β-cyclodextrin solution and zein solution were mixed. The pH of the β-cyclodextrin-zein mixture was adjusted to 11 using 1M NaOH. After magnetic stirring for 1 hour, the pH was adjusted back to 7 using 1M HCl, and magnetic stirring was continued for 15 minutes. The mixture was then sonicated to obtain zein-β-cyclodextrin composite particles at different ultrasonic powers. The ultrasonic conditions were: 30 kHz, 14 min, 375 W, 4 s operation followed by 2 s intermittent operation. The interfacial properties of the composite particles were observed using the three-phase contact angle. The ionic and thermal stability of the composite particles were observed using particle size, potential, dispersibility index, and particle appearance (see [reference]). Figure 5-7 ).

[0067] Figure 5 The figures show the three-phase contact angles of single-component β-CD (A), Zein (B), and the composite particle Zein-β-CD (C). It can be seen that Zein protein itself has strong hydrophobicity, resulting in a large three-phase contact angle of 133.6°. β-Cyclodextrin has a special structure with an extremely hydrophilic outer surface and partial water solubility. Therefore, when water droplets fall onto the surface of β-cyclodextrin flakes, the water droplets are immediately absorbed by the β-cyclodextrin, resulting in a contact angle of approximately 8.3°. When Zein and β-CD are combined via ultrasound, hydrophobic groups are introduced through hydrogen bonding and hydrophobic interactions, increasing the Zein-β-CD three-phase contact angle to 21.7°.

[0068] Figure 6 This is a graph showing the ionic stability of the Zein-β-CD composite particles. Figure 6 As shown in A, compared to day 1, the appearance of the particulate solution on day 5 showed no significant change, and no precipitate was observed. From... Figure 6As shown in section B, compared with the control, the particle size exhibited a trend of first increasing, then decreasing, and then increasing again with increasing salt ion concentration. The particle size was smallest at a salt ion concentration of 0.4 mol / L. Increasing the salt ion concentration led to an increase in particle size, but the overall particle size remained below 200 nm. The dispersibility index also showed the same trend (P < 0.05), indicating that the Zein-β-CD composite particles possess salt ion tolerance. Compared with the control, the absolute value of the Zeta potential decreased overall with increasing salt ion concentration, indicating that different concentrations of salt ions have a charge-shielding effect on the Zein-β-CD composite particles.

[0069] Figure 7 The thermal stability diagram of the Zein-β-CD composite particles is shown. Figure 7 As shown in A, after heating at different temperatures (75℃, 80℃, 100℃, 115℃, 121℃) for 30 minutes, compared with day 1, the composite particles showed no significant change in appearance color or precipitation after 5 days, indicating that the composite particles have strong thermal stability. Figure 7 As shown in B, the particle size and dispersibility index increase with increasing heating temperature. When heated to 121℃, the particle size of the composite particles is still below 100nm and has good dispersibility (PDI = 0.45). Meanwhile, the absolute value of the Zeta potential decreases with increasing temperature, which may be because high-temperature heating causes partial aggregation of protein and a reduction in functional groups.

[0070] Based on the above data, it can be seen that Zein-β-CD composite particles have good interfacial properties, ionic stability, and thermal stability.

[0071] Example 4

[0072] Corn oil and clove essential oil were mixed and dispersed as the oil phase in the Zein-β-CD composite particle dispersion obtained above, wherein the oil phase accounted for different volume percentages of the emulsion of 50%, 60%, 70%, 75%, 80%, and 85%.

[0073] Different oil phases were dispersed into the composite particle dispersion obtained above and then homogenized for 2 minutes using a high-speed dispersing shear mill at a speed of 12,000 rpm to obtain a high internal phase Pickering emulsion.

[0074] The properties of the emulsions with different oil phases obtained above were measured, see [reference]. Figure 8-16 (Among them, bioavailability, antioxidant properties and stability tests can be carried out in accordance with conventional methods. For example, the determination of in vitro digestibility can be referenced from Li Wenjing (2023).)

[0075] The determination of DPPH free radical scavenging capacity was based on Wang Chunying (2020), the determination of ABTS free radical scavenging capacity was based on Liu Qian (2021), the determination of hydroxyl free radical scavenging capacity was based on Duan Xueqin (2014), the determination of superoxide free radical scavenging capacity was based on Yang Xiaohua (2022), the determination of primary lipid oxidation degree (content of hydroperoxide) and secondary lipid oxidation degree (content of malondialdehyde) was based on Liu Qian (2021), and the determination of emulsion stability was based on Yu Di (2022). The determination methods were slightly modified according to the actual situation.

[0076] Wang Chunying. 2020. Preparation of high internal phase Pickering emulsion of egg white protein and its performance in encapsulating curcumin [D]. Jilin University.

[0077] Liu, Qian. 2021. Preparation, characterization and delivery of zein-pullulan-stabilized Pickering emulsion [D]. Hunan University.

[0078] Duan Xueqin. 2014. Extraction, content determination and antioxidant activity study of curcumin from medicinal plants of the genus Curcuma [D]. Sichuan Agricultural University,

[0079] Yu, Di. 2022. Preparation of high internal phase Pickering emulsion stabilized by modified soybean globulin particles and its application as a substitute for fat in sausages [D]. Shenyang Agricultural University.

[0080] Li Wenjing. 2023. Preparation of Pickering emulsion stabilized by prolyl / proanthocyanidins / pectin composite nanoparticles and its loading with curcumin [D]. Shandong Agricultural University.

[0081] Yang Xiaohua. 2022. Preparation of Lycium barbarum leaf flavonoid-collagen complex and its stabilizing effect on lutein emulsion [D]. Ningxia University.

[0082] Figure 8 The figure shows the Pickering emulsion particle size distribution for different oil phase ratios. As can be seen from the figure, the emulsion particle size first increases, then decreases, and then increases again with the increase of oil volume. The particle size reaches its minimum at 75% oil phase. At this point, the interfacial tension increases, causing the particles on the interface to rearrange, increasing the number of effective particles and encapsulating the oil droplets, thus reducing the emulsion particle size.

[0083] Figure 9 The figures show the microstructure of Pickering emulsions with different oil phase ratios. As can be seen from the figures, at 75% oil content, the droplets are the smallest, and the droplets are compressed against each other. The composite particles are evenly distributed at the oil-water interface, which can stabilize the oil-water interface and form a gel network structure.

[0084] Figure 10The figure shows the effect of different oil phase ratios on the rheological properties of Pickering emulsions. As can be seen from the figure, with the increase of temperature, the storage modulus is greater than the loss modulus. The high internal phase Pickering emulsion with 75% oil phase loaded with clove essential oil has the highest storage modulus, indicating that the Pickering emulsion prepared under this condition has gel properties with viscoelasticity as the main characteristic.

[0085] Figure 11 Bioavailability of Pickering emulsions with different oil phase ratios. As shown in the figure, compared with clove oil in corn oil (bioavailability 20.8%), the bioavailability of clove oil delivered using Pickering emulsions generally increased, in the following order: 75% oil volume fraction (32.1%) > 80% oil volume fraction (31.5%) > 70% oil volume fraction (30.5%) > 60% oil volume fraction (25.2%) > 60% oil volume fraction (20.8%). The high internal phase Pickering emulsion with an oil volume fraction of 75% showed the highest bioavailability of clove oil. This phenomenon may be because during digestion, the emulsion can form fatty acid micelles, and the hydrophobic clove oil can dissolve in the micelles, improving its utilization. The high internal phase Pickering emulsion with an oil volume fraction of 75% formed a stable gel network structure, protecting the volatilization of clove oil and allowing it to reach the small intestine smoothly for better utilization.

[0086] Figure 12 Antioxidant activity of Pickering emulsions with different oil phase ratios. DPPH and ABTS can be used to determine the total antioxidant capacity of substances in vitro. Figure 12 A indicates that the overall antioxidant activity of clove essential oil encapsulated in Pickering emulsion was higher than that of the control group. Clove essential oil alone showed scavenging rates of 34.3% and 35.6% for DPPH and ABTS in corn oil, respectively. When the oil phase concentration was increased to 75%, the scavenging rates of DPPH and ABTS increased to 79.5% and 79.1%, respectively, demonstrating the strongest ability to scavenge DPPH and ABTS. Figure 12 According to B, clove essential oil alone showed scavenging rates of 41.2% and 26.4% against hydroxyl radicals and superoxide anions in corn oil. When the oil volume fraction was 75%, the scavenging rates against hydroxyl radicals and superoxide anion radicals reached 69.4% and 78%, respectively, indicating the strongest ability to scavenge hydroxyl radicals and superoxide anion radicals. Figure 12 C and 12D reflect the emulsion's resistance to oil oxidation by measuring the content of primary oxidation products (hydroperoxides) and secondary oxidation products (malondialdehyde). Figure 12As shown in Figure C, the hydroperoxide content increased in different groups with prolonged storage time. After 15 days of storage, the hydroperoxide concentration in corn oil increased from 21.2 mmol / kg to 136.7 mmol / kg. With the addition of clove essential oil, the hydroperoxide concentration increased from 16.03 mmol / kg to 119.1 mmol / kg after 15 days of storage, indicating that the addition of clove essential oil slowed down the oxidation of the oil. The Hydroperoxide concentration in Pickering emulsions with different oil phases encapsulating clove essential oil was significantly lower than that in corn oil and corn oil loaded with clove essential oil during storage. The higher the oil volume fraction, the lower the hydroperoxide concentration; the Pickering emulsion with a 75% oil phase and a high internal phase had the lowest hydroperoxide concentration during storage. Figure 12 D indicates that the malondialdehyde (MDA) content in Pickering emulsions with different oil volume fractions is < the MDA content in corn oil loaded with clove essential oil < the MDA content in corn oil alone. The MDA content in corn oil increased by 16% after 15 days of storage. After adding clove essential oil, the MDA content in corn oil increased by 15.2%, indicating that adding clove essential oil can inhibit the increase in MDA content. Compared with other groups of Pickering emulsions, the MDA content in the 75% oil volume fraction Pickering emulsion increased from 2.8 mmol / kg to 25.4 mmol / kg after 15 days of storage, an increase of 11%, and the lowest MDA content value was observed.

[0087] Figure 13 The figure shows the storage stability of high internal phase Pickering emulsions with different oil phase ratios. As can be seen from the figure, after 150 days of storage, no signs of stratification or thinning of oil were observed in the 75% oil phase Pickering emulsion, indicating that it remained stable.

[0088] Figure 14 The figure shows the thermal stability of the Pickering emulsion with an optimal oil phase ratio of 75% and a high internal phase. As can be seen from the figure, after heating at 75, 80, 90, 115, and 121 °C for 30 min and storing for 150 days, no demulsification or separation occurred, and the emulsion remained stable.

[0089] Figure 15 The figure shows the ionic stability of the high internal phase Pickering emulsion with an optimal oil phase ratio of 75%. As can be seen from the figure, the high internal phase Pickering emulsion exhibits good stability over 150 days at ionic strengths of 0–0.6 M, demonstrating excellent salt ion tolerance.

[0090] Figure 16 This is a pH stability graph for a 75% oil phase high internal phase Pickering emulsion. The graph shows that the high internal phase Pickering emulsion remained stable and did not separate after 150 days of storage at pH 2–12.

[0091] As can be seen from the above, the optimal oil phase ratio is 75%.

[0092] Example 5

[0093] Using the above examples, a high internal phase Pickering emulsion of clove essential oil with an oil ratio of 75% was obtained for the preparation of emulsified meat products:

[0094] Lean pork and fat were separated and cut into small pieces. Each piece was then ground separately in a meat grinder for 30 seconds. The minced meat was divided into three groups: a blank group, an essential oil group, and an emulsion group. The essential oil was commercially available 99% clove essential oil, and the emulsion was a homemade high-internal-phase Pickering emulsion loaded with clove essential oil. Ingredients were added according to the specified ratio, mixed well, and then quickly chopped for 3 minutes to form pork patties approximately 7.5 cm in diameter and 2 cm thick. These patties were baked in an oven and then stored at 4°C.

[0095] The pork patty recipes for different experimental groups are shown in Table 1, with pork patties without clove oil serving as a control.

[0096] Table 1. Recipes for making pork patties in different groups

[0097]

[0098] The preservation status of the pork patties was determined by evaluating their texture, sensory characteristics, color difference, and subsequent storage conditions.

[0099] 1) The textural properties of meat products can reflect their quality and structural characteristics. The greater the firmness, the greater the elasticity, and the more energy is required for chewing. Figure 17 The study showed the trends in hardness, elasticity, cohesiveness, and chewiness of the three groups of pork patties during storage. As the figure shows, the hardness, elasticity, cohesiveness, and chewiness of the control group and the essential oil group initially increased with prolonged storage, then began to decrease from day 9. This indicates that protein and fat oxidation increased at this point, resulting in looser meat and reduced hardness. The emulsion group showed an increasing trend throughout the storage period with stable changes. The hardness, elasticity, cohesiveness, and chewiness of the emulsion group were higher than the other two groups. The gel network structure formed by the high internal phase Pickering emulsion effectively locked in moisture and protected the clove essential oil. The antibacterial effect of the clove essential oil inhibited microbial growth to some extent, and the mucus produced by microbial protein decomposition also affected the texture of the meat products.

[0100] 2) Sensory evaluation of food involves consumers assessing a product based on indicators such as color, texture, flavor, texture, and overall acceptability, which can be used to determine their level of liking for the product. Table 2 shows the sensory evaluation results of the three groups of pork patties. The texture score of the control group's pork patties was lower than that of the essential oil group and the emulsion group, with the emulsion group scoring the highest. This indicates that the pork patties in the control group had a loose and non-dense texture, while the pork patties in the emulsion group had a firm and non-dense overall structure due to the high viscoelasticity network structure of the high internal phase Pickering emulsion, which enhances the interaction between the meat and protein. In terms of color, texture, flavor, and overall acceptability, the emulsion group outperformed the other two groups. Because the high internal phase Pickering emulsion contains a high proportion of oil, the pork patties in the emulsion group had a rich and creamy taste, lacking the distinctive flavor of clove essential oil. This suggests that applying clove essential oil in emulsion encapsulation to meat storage can also result in good sensory evaluation.

[0101] Table 2 Sensory evaluation results of different groups of pork patties

[0102]

[0103] 3) The color of meat products is one of the important indicators reflecting the quality of meat products. Consumers can evaluate the quality of meat products with the naked eye. Figure 18 The graph shows the changes in L*, a*, and b* values ​​of three groups of pork patties during storage. As can be seen from the graph, the L* values ​​of all three groups of pork patties increased on days 1 and 3 of storage. This may be because, in the early stages of storage, the ferrous ions in the muscle tissue were not oxidized to ferric ions, maintaining a good meat color. With increasing storage time, the L* values ​​of all three groups of pork patties decreased significantly (P < 0.05), indicating that the muscle tissue contained a large amount of ferric ions, and the meat color darkened. The L* value of the emulsion group was lower than the other two groups and changed slowly. The a* values ​​of all three groups of pork patties decreased significantly with the extension of storage period (P < 0.05). At the end of storage on day 15, the a* values ​​of the control group, the essential oil group, and the emulsion group decreased by 36.3%, 41.5%, and 25%, respectively. The a* value of the pork patties in the emulsion group showed a slight decrease on day 3, with minimal changes during subsequent storage. This may be attributed to the high internal phase Pickering emulsion inhibiting the volatilization of clove essential oil, thus improving its bioavailability and prolonging its effect. The b* values ​​of all three pork patties increased significantly with increasing storage period (P < 0.05). From day 6, the b* value of the emulsion group was lower than that of the other two groups, indicating that the b* value of the emulsion group was inhibited. The high internal phase Pickering emulsion loaded with clove essential oil inhibited myoglobin formation.

[0104] 4) Microbial growth causes meat products to spoil, and the total bacterial count reflects the degree of spoilage. The national standard stipulates that the total bacterial count for fresh products should be less than 1×10⁻⁶. 6CFU / g. Table 3 shows the changes in total bacterial count in the three groups of pork patties during storage. On day 0, no bacteria were detected in any of the three groups, possibly due to clean processing, minimal contamination, and immediate vacuum packaging after production. As time progressed, the total bacterial count in all three groups of pork patties significantly increased (P < 0.05). The control group reached a total bacterial count of 2.15 × 10⁻⁶ on day 9. 5 The pork patties in the control group spoiled. Both the essential oil and emulsion groups showed some inhibitory effect on bacteria in the pork patties, but the antibacterial effects differed. The pork patties in the essential oil group spoiled on day 12, while those in the emulsion group spoiled on day 15. Clove essential oil, containing eugenol, β-caryophyllene, and other substances, possesses excellent antibacterial properties. However, its unstable characteristics, such as easy volatility and decomposition, result in a short-lived antibacterial effect when applied to meat products. Encapsulating clove essential oil in a high internal phase Pickering emulsion slows down the evaporation rate and prolongs the antibacterial time. Clove essential oil can inhibit the activity of some enzymes in the cell wall of synthetic bacteria. The small particle size and easily permeable high internal phase Pickering emulsion loaded with clove essential oil can better exert its antibacterial effect.

[0105] Table 3. Results of total bacterial count in different groups of pork patties

[0106]

[0107] 6) Product pH can be used to measure the freshness of a product; the pH of fresh meat is between 5.8 and 6.2. The pH value of pork patties was determined according to GB51009.237-2016, "Determination of pH Value in Food". Figure 19 It was observed that as the storage period of the pork patties increased, the pH values ​​of all three groups initially decreased and then increased, with the control group showing the highest pH value. The control group reached its lowest pH value on day 3, while the essential oil and emulsion groups reached their lowest pH values ​​on day 6. The decrease in pH value may be due to a small number of bacteria decomposing glucose in the muscle to produce lactic acid and releasing phosphoric acid from ATP in the early stages of product processing, thus lowering the product's pH. From day 6 onwards, the pH values ​​of all three groups significantly increased (P < 0.05). The control group reached a pH of 6.24 on day 9, showing signs of spoilage, while the essential oil and emulsion groups had pH values ​​below 6 at this time. On day 15, the pH values ​​of the blank group, essential oil group, and emulsion group reached 6.85, 6.72, and 6.63, respectively, indicating that the pH value increased over time. During storage, the number of spoilage microorganisms increased, and these microorganisms decomposed proteins to produce ammonia and trimethylamine. Compared to the control group and essential oil group, the emulsion group was better able to inhibit the volatilization of clove essential oil, prolonging its antibacterial effect and slowing down the spoilage of the pork patties.

[0108] 7) Volatile basic nitrogen (TVB-N) refers to ammonia and amines produced when proteins in meat products are broken down by bacteria or proteases in an alkaline environment. The TVB-N content of meat products can be used to measure their freshness. National safety standards require that the TVB-N value of fresh meat products be below 15 mg / 100g. The TVB-N of pork patties was determined according to GB5009.228-2016, "Determination of Volatile Basic Nitrogen". Figure 20 The changes in TVB-N content of the three groups of pork patties during storage were investigated. On days 0 and 3, there was no significant difference in TVB-N values ​​between the essential oil group and the emulsion group and the control group (P > 0.05). As the storage time increased, the TVB-N values ​​of all three groups of pork patties showed an increasing trend (P < 0.05). The TVB-N value of the control group was significantly higher than that of the other two groups (P < 0.05). The TVB-N value of the control group pork patties reached 15.7 mg / 100g on day 9, exceeding the safety standard first. The TVB-N value of the essential oil group pork patties reached 15.4 mg / 100g on day 12. The TVB-N value of the emulsion group pork patties was lower than that of the other two groups throughout the storage period, and reached 15.6 mg / 100g on day 15. This indicates that the clove essential oil was well protected by the high internal phase Pickering emulsion, which reduced volatility, improved antibacterial effect, and slowed down the generation of TVB-N value in the pork patties.

[0109] 8) The reaction between thiobarbituric acid (TBA) and malondialdehyde (MDA) produces a TBARS value, which is commonly used to measure the degree of fat oxidation in meat products during storage. A higher TBARS value indicates a higher degree of fat oxidation in the meat product. It is generally believed that meat products begin to spoil when the TBARS value exceeds 1 mg MDA / kg. The TBARS value of pork patties is calculated by measuring the absorbance at 532 nm of low-fat meatballs. Figure 21As shown, the TBARS values ​​increased slowly on days 0 and 3. This may be because, in the early stages of storage, the initially generated peroxides did not produce large amounts of malondialdehyde (MDA), and MDA reacted with proteins and carbohydrates in the meat products, thus slowing down the increase in MDA. With the increase in storage period, the TBARS values ​​of the three groups of pork patties gradually increased. The TBARS value of the control group was higher than the other two groups. On day 6, the TBARS value of the control group reached 0.65 mg MDA / kg, and on day 9, it reached 1.12 mg MDA / kg. At this point, the control group began to deteriorate on day 9, and the extended storage period led to the accumulation of large amounts of MDA, causing the TBARS value to gradually increase. The TBARS value of the pork patties in the essential oil group reached 1.06 mg MDA / kg on day 12. Clove essential oil has good antioxidant activity and can inhibit the formation of malondialdehyde in pork patties. However, due to its oxidative loss, its effect is less than that of the emulsion group. The TBARS value of the pork patties in the emulsion group reached 1.3 mg MDA / kg on day 15. Compared with the other two groups, the gel network structure formed by the high internal phase Pickering emulsion provides a stable environment to protect the volatilization of clove essential oil, improve its antioxidant properties, and delay lipid oxidation.

[0110] In summary, Zein-β-CD prepared through pH shifting and ultrasound assistance exhibits the smallest particle size and PDI, the largest absolute potential value, and the best hydrophobicity. A clove-oil-loaded high-internal-phase Pickering emulsion was prepared by mixing clove oil with corn oil and then with Zein-β-CD composite particles. This emulsion demonstrates good storage stability. Using this clove-oil-loaded high-internal-phase Pickering emulsion in the preservation of emulsified meat products can improve product quality and extend shelf life.

Claims

1. A method for preserving emulsified meat products, characterized in that: A high internal phase Pickering emulsion loaded with clove essential oil was added to meat products for preservation; the high internal phase Pickering emulsion loaded with clove essential oil was a modified Zein- β - The oil phase of CD particles mixed with clove essential oil and corn oil is homogenized to obtain the final product; the amount of emulsion added accounts for 16% of the total amount. The modified Zein- β -CD particles are composed of zein and β - The cyclodextrin solution was mixed, and the pH of the system was adjusted to 11. The mixture was magnetically stirred for 1 hour, then the pH was adjusted to neutral with acid. Magnetic stirring was continued for 15 minutes, followed by ultrasonic treatment to obtain the modified Zein-. β -CD particles; wherein, the ultrasonic settings are 30 kHz, ultrasonic power 150 W~450 W, ultrasonic time 2 min~18 min, zein and β - The mass ratio of cyclodextrins is 3:1 to 1:3; The high internal phase Pickering emulsion loaded with clove essential oil consists of a thorough mixture of clove essential oil and corn oil as the oil phase, and the oil phase is mixed with modified Zein- β -CD particles are homogenized to obtain the product; the homogenization conditions are: 12000 r / min, 2 min, and the oil phase accounts for 75% to 80% of the emulsion volume.

2. The method for preserving emulsified meat products according to claim 1, characterized in that: The combination of zein and β - The cyclodextrin solution was mixed, and the pH of the system was adjusted to 11 with NaOH. After magnetic stirring for 1 h, the pH was adjusted to 7 with HCl, and magnetic stirring was continued for 15 min. Then, ultrasonic treatment was performed to obtain the modified Zein-. β -CD particles; wherein, the ultrasonic setting parameters are set to a 4-second working mode with a 2-second interval.

3. An emulsified meat product with a long shelf life, characterized in that: By weight percentage, the composition is 60% lean pork, 2% pork fat, 16% ice water, 2% salt, 3% starch, 0.2% compound phosphate, 0.8% carrageenan, and the remainder is the high internal phase Pickering emulsion loaded with clove essential oil as described in claim 1.

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