Curcumin nanoemulsion coating agent, and preparation method and application thereof

Abstract

This invention discloses a curcumin nanoemulsion coating agent, its preparation method, and its application. The coating agent is an oil-in-water nanoemulsion comprising the following components: curcumin, emulsifier, edible oil, sugar, and water, wherein curcumin is encapsulated within the nanoemulsion. The emulsifier is a food-grade emulsifier selected from one or more of modified soybean lecithin, sodium caseinate, octenyl succinate starch ester, and sucrose fatty acid ester. The w / v concentration of curcumin in the coating agent is 0.01%~0.05%, and the w / v concentration of the emulsifier in the coating agent is 1%~10%. The nanoemulsion coating agent provided by this invention can effectively deliver curcumin, improve its stability, form a protective coating on the surface of heat-processed meat products, and effectively inhibit the formation of heterocyclic amines.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a curcumin nanoemulsion coating agent and its preparation method and application. Background Technology

[0002] Processed meat products are an important part of modern diets, but harmful compounds such as heterocyclic amines (HAs) are easily generated during high-temperature cooking processes (such as frying, grilling, and roasting). Heterocyclic amines have strong mutagenic and carcinogenic properties, and long-term intake increases the risk of cancer, making them a hot research topic in the field of food safety. Studies have shown that heterocyclic amines are mainly generated through Maillard reactions and the pyrolysis of amino acids and creatine, and their formation is closely related to factors such as processing temperature, time, and raw material composition.

[0003] Curcumin, a natural polyphenolic compound extracted from turmeric, possesses excellent free radical scavenging and metal chelating properties, showing promising potential in inhibiting the formation of heterocyclic amines. Previous studies have reported that directly adding curcumin to minced meat products can reduce the formation of heterocyclic amines by approximately 50%. However, as a fat-soluble compound, curcumin exhibits poor dispersibility in aqueous meat product matrices; it is also sensitive to heat, light, and alkaline conditions, and is easily degraded and inactivated during thermal processing; furthermore, current applications are largely limited to minced meat products (such as meat patties and minced meat), making it difficult to apply to whole muscle tissue or surface-treated meat products. These limitations severely restrict the practical application of curcumin in meat processing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a nanoemulsion coating agent that can effectively encapsulate curcumin, improve its physicochemical stability, and continuously inhibit heterocyclic amines during thermal processing, as well as its preparation method and application.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A curcumin nanoemulsion coating agent for inhibiting the formation of heterocyclic amines in heat-processed meat products, the coating agent being an oil-in-water nanoemulsion comprising the following components: curcumin, emulsifier, edible oil, sugars, and water, wherein curcumin is encapsulated in the nanoemulsion; The emulsifier is a food-grade emulsifier selected from one or more of modified soybean lecithin, sodium caseinate, octenyl succinate starch ester, and sucrose fatty acid ester. The curcumin has a w / v concentration of 0.01% to 0.05% in the coating agent; the emulsifier has a w / v concentration of 1% to 10% in the coating agent.

[0006] Furthermore, the emulsifier is sodium caseinate, with a w / v concentration of 8% to 10% in the coating agent; or the emulsifier is sucrose fatty acid ester, with a w / v concentration of 1% to 10% in the coating agent.

[0007] Furthermore, the edible oil is one or more of corn oil, soybean oil, and rapeseed oil, and the volume fraction of the edible oil in the coating agent is 5% to 20%.

[0008] Furthermore, the sugar is one or more of xylose, glucose, and fructose, and the w / v concentration of the sugar in the coating agent is 1% to 5%.

[0009] Furthermore, the coating agent has an average particle size of 150~350 nm, PDI≤0.3, and an absolute value of Zeta potential ≥30mV.

[0010] The present invention also provides a method for preparing the curcumin nanoemulsion coating agent, comprising the following steps: (1) Dissolve sugars in water to form an aqueous phase; (2) Dissolve curcumin and emulsifier in edible oil to form an oil phase; (3) The aqueous phase and oil phase are mixed and subjected to high-speed shearing to obtain a crude emulsion; (4) The crude emulsion was subjected to high-pressure homogenization to obtain curcumin nanoemulsion coating agent.

[0011] Furthermore, the rotational speed of the high-speed shearing in step (3) is 10,000~20,000 rpm, and the pressure of the high-pressure homogenization in step (4) is 20~30 MPa.

[0012] The present invention also provides an application of the curcumin nanoemulsion coating agent, wherein the coating agent is applied to the surface of meat products and then subjected to heat treatment to inhibit the formation of heterocyclic amines in heat-processed meat products.

[0013] Furthermore, the meat products include poultry, livestock meat and their products; the heat processing includes at least one of air frying, deep frying, grilling and pan-frying.

[0014] Furthermore, the coating method involves immersing the meat product in the coating agent for 5 to 20 minutes, or spraying or brushing the coating agent onto the surface of the meat product.

[0015] This invention aims to address the technical problems encountered when curcumin is directly applied to meat products, such as low solubility, poor thermal stability, and difficulty in uniform distribution on the surface of whole meat products. Studies have shown that encapsulating curcumin in an oil-in-water nanoemulsion can significantly improve its solubility, stability, and bioavailability, and it can be applied to the surface treatment of meat products through coating, impregnation, and other methods. The choice of emulsifier is crucial to the stability and functionality of the nanoemulsion. Modified soybean lecithin, sodium caseinate, octenyl succinate starch ester, sucrose fatty acid ester, etc., each possess different interfacial properties and stabilization mechanisms. Furthermore, their effects on inhibiting heterocyclic amines in whole meat products require special investigation.

[0016] This invention provides a nanoemulsion coating agent that can effectively deliver curcumin, improve its stability, form a protective coating on the surface of heat-processed meat products, and efficiently inhibit the formation of heterocyclic amines.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By encapsulating curcumin in a nanoemulsion, the present invention significantly improves its dispersibility in an aqueous system and solves the problem of poor solubility of curcumin when applied directly; at the same time, the interfacial layer formed by the emulsifier protects curcumin and improves its stability during thermal processing.

[0018] (2) The present invention systematically compared the effects of four commonly used food emulsifiers on the properties of curcumin nanoemulsions and found that nanoemulsions stabilized by sodium caseinate (especially 10% concentration) have the best particle size distribution (164.1~216.2 nm), PDI (0.187), Zeta potential (-37.3~-53.7 mV), as well as thermal stability and ionic stability. They can resist the damage of high temperature and salt ion environment and are suitable for application in the heat processing of salted meat products.

[0019] (3) The curcumin nanoemulsion coating agent of the present invention exhibits excellent inhibition effect on heterocyclic amines in practical applications. Experiments show that after chicken wings are treated with 10% sodium caseinate-stabilized curcumin nanoemulsion (Cur-NE-10gSC) and then air-fried at 190°C for 15 min, the total heterocyclic amine content is reduced by 93%, with PhIP inhibition rate reaching 99% and MeIQx inhibition rate reaching 97%, which is significantly better than the non-emulsified control group (63% inhibition rate) and other emulsifier groups.

[0020] (4) The sucrose fatty acid ester-stabilized curcumin nanoemulsion of the present invention exhibits the best permeability and uniform distribution characteristics in the skin of chicken wings. CLSM images show that it can penetrate deep into the skin layer and form a continuous coating, giving the treated chicken wings better color (sensory score 9.27) and taste (sensory score 8.16), thus achieving a balance between food safety and sensory quality.

[0021] (5) The preparation method provided by this invention is simple and easy to implement. All raw materials used are food-grade and comply with national food safety standards. It is suitable for industrial production and widespread application. By treating whole meat products with a coating method, the application range of curcumin in non-minced meat products is expanded, providing a new technical means for producing safer heat-processed meat products. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 CLSM images of curcumin nanoemulsions stabilized with different emulsifiers.

[0024] Figure 2 This invention illustrates the effect of different emulsifiers on the thermal stability of curcumin nanoemulsions. A1 / A2, B1 / B2, and C1 / C2 represent the changes in particle size distribution, PDI, and Zeta potential after treatment at different temperatures, respectively.

[0025] Figure 3 This invention illustrates the effect of different emulsifiers on the ionic stability of curcumin nanoemulsions. A1 / A2, B1 / B2, and C1 / C2 represent the changes in particle size distribution, PDI, and Zeta potential after treatment with different NaCl concentrations, respectively.

[0026] Figure 4 The effect of different emulsifiers on the physical stability of curcumin nanoemulsion in this invention (LUMiSizer measurement results).

[0027] Figure 5 This is a CLSM image showing the permeation and distribution of different curcumin nanoemulsions in chicken wing skin according to the present invention. Detailed Implementation

[0028] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0029] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0031] This invention provides a curcumin nanoemulsion coating agent to inhibit the formation of heterocyclic amines in heat-processed meat products. The coating agent is an oil-in-water nanoemulsion comprising the following components: curcumin, emulsifier, edible oil, sugar, and water. The emulsifier is a food-grade emulsifier selected from one or more of modified soybean lecithin (MSP), sodium caseinate (SC), octenyl succinate starch ester (SSOS), and sucrose fatty acid ester (SE). The concentration of curcumin in the coating agent is 0.01%~0.05% (w / v); the concentration of the emulsifier in the coating agent is 1%~10% (w / v).

[0032] In this invention, the unit "% (w / v)" is g / 100mL. For example, 0.01% (w / v) is 0.01g / 100mL.

[0033] Preferably, the emulsifier is sodium caseinate, and its concentration in the coating agent is preferably 8%~10% (w / v), most preferably 10% (w / v). The coating agent has an inhibition rate of ≥90% against heterocyclic amines. Sodium caseinate can form a dense interfacial layer, giving the emulsion excellent thermal and ionic stability.

[0034] Preferably, the emulsifier is a sucrose fatty acid ester, and its concentration in the coating agent is 1%~10% (w / v). This coating agent has excellent penetration and uniform distribution characteristics on the surface of meat products. Sucrose fatty acid ester is a nonionic emulsifier, and the emulsion it forms has good affinity for the surface of meat products.

[0035] Preferably, the edible oil is one or more of corn oil, soybean oil, and rapeseed oil, with corn oil being the most preferred; the volume fraction of the edible oil in the coating agent is 5% to 20%. Corn oil has good oxidative stability and the ability to dissolve curcumin, making it suitable as an oil phase carrier.

[0036] Preferably, the sugar is one or more of xylose, glucose, and fructose, with xylose being the most preferred; the concentration of the sugar in the coating agent is 1% to 5% (w / v). Xylose, as a Maillard reaction substrate, can react with amino acids and other substances on the surface of meat products in the coating system, which helps to form a uniform coating structure.

[0037] In a preferred embodiment, the emulsion composition is: 0.01%~0.05% (w / v) curcumin, 1%~10% (w / v) emulsifier, 1%~5% (w / v) sugar, 5%~20% (v / v) edible oil, and the balance being water. More preferably, the composition is: 10% (w / v) sodium caseinate, 0.02% (w / v) curcumin, 3% (w / v) xylose, and 10% (v / v) corn oil.

[0038] Preferably, the coating agent has an average particle size of 150~350 nm, a PDI ≤ 0.3, and an absolute value of a Zeta potential ≥ 30 mV. This particle size range facilitates the uniform spreading and penetration of the emulsion on the surface of meat products, while the higher Zeta potential ensures the electrostatic stability of the emulsion.

[0039] The present invention also provides a method for preparing the above-mentioned curcumin nanoemulsion coating agent, comprising the following steps: (1) Dissolve sugars in water to form an aqueous phase; (2) Dissolve curcumin and emulsifier in edible oil to form an oil phase; (3) The aqueous phase and oil phase are mixed and subjected to high-speed shearing to obtain a crude emulsion; (4) The crude emulsion was subjected to high-pressure homogenization to obtain curcumin nanoemulsion coating agent.

[0040] Preferably, the high-speed shearing speed in step (3) is 10,000~20,000 rpm and the shearing time is 3~10 min.

[0041] Preferably, the pressure of the high-pressure homogenization in step (4) is 20~30 MPa, and the number of homogenization cycles is 2~5.

[0042] This invention further provides the application of the above-mentioned curcumin nanoemulsion coating agent in inhibiting the formation of heterocyclic amines in heat-processed meat products. The coating agent is applied to the surface of the meat product, followed by heat processing. The meat product includes poultry, livestock meat, and their products, preferably chicken wings. The heat processing includes at least one of air frying, deep-frying, grilling, and pan-frying.

[0043] Preferably, the coating method is to immerse the meat product in the coating agent for 5 to 20 minutes, or to spray or brush the coating agent onto the surface of the meat product.

[0044] In a preferred embodiment, the meat products are immersed in a coating agent and soaked at 4°C for 10 min, followed by air frying at 190°C for 15 min.

[0045] After treatment with this invention, the total heterocyclic amine inhibition rate of meat products can reach ≥90%, and the sensory quality is maintained or better than the untreated control.

[0046] The curcumin nanoemulsion coating agent provided by this invention can be widely used in the safe treatment of heat-processed meat products. This coating agent can be applied to the surface of meat products on the production line of meat processing enterprises through methods such as dipping or spraying, followed by subsequent heat processing (such as air frying, deep-frying, grilling, etc.). This method is simple and easy to implement, requires no changes to existing production processes, and can be directly integrated into existing production lines. The treated meat products show a significant reduction in heterocyclic amine content while maintaining or improving sensory quality, demonstrating good market application prospects.

[0047] Example 1: Preparation of curcumin nanoemulsion coating agent Curcumin nanoemulsions were prepared using modified soybean lecithin (MSP), sodium caseinate (SC), octenyl succinate starch ester (SSOS), and sucrose fatty acid ester (SE) as emulsifiers, respectively.

[0048] Preparation method: 3% (w / v) xylose was dissolved in 100 mL of deionized water as the aqueous phase. 0.02% (w / v) curcumin and different proportions (1% and 10%, w / v) of emulsifier were dissolved in corn oil as the oil phase (corn oil accounted for 10% of the total volume). The aqueous and oil phases were mixed and sheared for 5 min at 16,000 rpm using a high-speed shear emulsifier (Fangxu, Shanghai, China) to obtain a crude emulsion. The crude emulsion was homogenized at 25 MPa using an ultra-high pressure homogenizer (AH-NANO, ATS, China) for 4 min, and the process was repeated 3 times to obtain a curcumin nanoemulsion.

[0049] The obtained samples were named as follows: Cur-NE-1gMSP, Cur-NE-1gSC, Cur-NE-1gSSOS, Cur-NE-1gSE, Cur-NE-10gMSP, Cur-NE-10gSC, Cur-NE-10gSSOS, and Cur-NE-10gSE.

[0050] Example 2: Determination of particle size and zeta potential of nanoemulsions The particle size, PDI, and Zeta potential of each nanoemulsion prepared in Example 1 were determined using a Zetasizer NanoZS particle size analyzer (Malvern Instruments, UK). The samples were diluted 100-fold with deionized water and equilibrated at 25°C for 120 s before measurement. The results are shown in Table 1.

[0051] Table 1 Physicochemical properties of different curcumin nanoemulsions

[0052] As shown in Table 1, Cur-NE-10gMSP had the smallest particle size (156.0 nm), while Cur-NE-10gSSOS had the largest (1150.7 nm). The SC and SE-stabilized emulsions had smaller and more uniform particle sizes, with PDI values ​​below 0.25. The MSP-stabilized emulsion exhibited a high absolute Zeta potential (-49 to -55 mV), demonstrating strong electrostatic stabilization. The SE-stabilized emulsion had a higher pH, which may affect the stability of curcumin.

[0053] Example 3: Microstructure observation of nanoemulsions The microstructure of the nanoemulsion prepared in Example 1 was observed using a confocal laser scanning microscope (CLSM, STELLARIS 5, Leica, Germany). 1 mL of the emulsion sample was taken, and 40 μL of Nile Red staining solution (1 mg / mL, dissolved in ethanol) was added. The mixture was shaken in the dark for 10 min and incubated at 4°C for 3 h. Excitation wavelengths were 488 nm and 561 nm, and observation was performed using a 60× objective lens.

[0054] The results are as follows Figure 1 The results showed that at an emulsifier concentration of 1%, the droplets were uniformly dispersed but had a relatively large particle size; when the emulsifier concentration increased to 10%, except for SSOS, the droplet size decreased significantly and the distribution became more uniform. Cur-NE-10gSSOS showed obvious aggregation, consistent with the particle size determination results. Cur-NE-1gSE droplets were fine and uniform, showing good dispersibility.

[0055] Example 4: Evaluation of the thermal stability of nanoemulsions The nanoemulsions prepared in Example 1 were treated at 60°C, 80°C, and 100°C for 60 min, respectively, and the changes in particle size, PDI, and Zeta potential before and after treatment were measured.

[0056] The results are as follows Figure 2 As shown, SC and SE-stabilized emulsions exhibited the best thermal stability, with minimal changes in particle size and PDI. The particle size of Cur-NE-1gSC remained within the range of 201.6–216.2 nm, and the SE-stabilized emulsion also showed similar good stability. The particle size of the SSOS-stabilized emulsion decreased significantly after heating (Cur-NE-10gSSOS decreased from 1150.7 nm to 754.7 nm), which may be due to thermally induced depolymerization, but its absolute size was still too large. The particle size of the MSP-stabilized emulsion increased slightly, indicating slight agglomeration or Ostwald ripening. After heating, the Zeta potentials of MSP and SE emulsions remained at a high level, the surface charge of the SC emulsion remained stable, and the SSOS emulsion had the lowest Zeta potential, further confirming its poor stability.

[0057] Example 5: Evaluation of the ionic stability of nanoemulsions The nanoemulsions prepared in Example 1 were mixed with NaCl solutions of different concentrations (final concentrations of 0.2, 0.5, and 1.0 M), and the changes in particle size, PDI, and Zeta potential were measured after standing for 0.5 h.

[0058] The results are as follows Figure 3 As shown, SSOS-stabilized emulsions are extremely sensitive to ionic strength. Cur-NE-1gSSOS exhibits severe aggregation in 1.0 M NaCl as its particle size increases from 306 nm to over 1077 nm. SC-stabilized emulsions demonstrate excellent ionic stability, with the particle sizes of Cur-NE-1gSC and Cur-NE-10gSC remaining essentially unchanged (197–220 nm), attributed to the steric stabilization mechanism of SC. MSP and SE-stabilized emulsions exhibit moderate stability, with Cur-NE-10gMSP maintaining a relatively small particle size of 165.7 nm in 1.0 M NaCl. The absolute value of the Zeta potential for all emulsions decreases with increasing ionic strength, with the most significant decrease observed in SSOS emulsions (Cur-NE-1gSSOS decreasing from -35.1 mV to -9.5 mV), directly related to its severe aggregation.

[0059] Example 6: Physical stability analysis of nanoemulsions The physical stability of the nanoemulsion prepared in Example 1 was evaluated using a LUMiSizer stability analyzer (LUMiFuge-111, Germany). Test conditions: rotation speed 4000 rpm, test time 9000 s, temperature 25℃.

[0060] The results are as follows Figure 4 As shown, when the emulsifier concentration is 1%, the MSP and SC-stabilized emulsions form a distinct emulsion layer (~9 mm) with a transmittance as high as 80%, indicating that the emulsion droplets migrate rapidly and emulsion separate under centrifugal force. The SE-stabilized emulsion has the smallest emulsion layer (~5 mm) and the lowest transmittance (~60%), exhibiting excellent anti-separation ability. When the emulsifier concentration increases to 10%, the SC, SSOS, and SE-stabilized emulsions do not form a distinct emulsion layer, and the transmittance is close to 0%, showing excellent kinetic stability. Although the 10% MSP-stabilized emulsion is significantly improved compared to 1% (emulsion layer ~4 mm, transmittance ~50%), it does not reach the stability level of other emulsifiers, indicating that the stabilization mechanism of MSP may mainly rely on electrostatic repulsion, and its stability is insufficient under strong centrifugal force.

[0061] Example 7: Evaluation of the antioxidant capacity of nanoemulsions The antioxidant activity of each nanoemulsion prepared in Example 1 was evaluated using the ABTS method, DPPH method, and total antioxidant capacity (T-AOC) kit, respectively, and a weighted comprehensive evaluation method (ABTS weight 0.4, DPPH weight 0.4, T-AOC weight 0.2) was used for comprehensive evaluation.

[0062] The results are shown in Table 2. Cur-NE-10gSC showed the best performance in the ABTS assay (99.02±0.20% scavenging rate), significantly higher than other groups. Cur-NE-1gSE showed the highest activity in the DPPH assay (51.86±4.25%), while Cur-NE-10gMSP had the highest T-AOC value (160.44±30.74 μmol / mL). The overall score showed that Cur-NE-10gMSP (0.62) and Cur-NE-10gSC (0.58) were the two formulations with the best antioxidant performance. Cur-NE-1gSE and Cur-NE-1gSSOS scores were moderate (0.46 and 0.45), while Cur-NE-10gSSOS score was the lowest (0.10).

[0063] Table 2 Antioxidant capacity of different curcumin nanoemulsions

[0064] Example 8: Inhibitory effect of curcumin nanoemulsion coating agent on heterocyclic amines in air-fried chicken wings Using fresh chicken wings as a model, the inhibitory effects of the various nanoemulsion coatings prepared in Example 1 on the formation of heterocyclic amines were evaluated. Fresh chicken wing midsections were taken, their surface moisture was blotted dry with absorbent paper, and they were randomly divided into groups. The treatment group had their chicken wings completely immersed in the respective nanoemulsions at 4°C for 10 min; the control group was immersed in a non-emulsified mixture containing the same amount of emulsifier and curcumin (denoted as the Cur- group) or pure corn oil. After immersion, the wings were drained for 30 s and then fried in an air fryer preheated to 190°C for 15 min, flipping them over after 7.5 min. After frying, the edible parts (meat and attached coating / skin) were homogenized and stored at -80°C for later testing.

[0065] The preparation method of Cur-10gSC group is as follows: 3% (w / v) xylose is dissolved in 100 mL of deionized water as the aqueous phase. 0.02% (w / v) curcumin and the corresponding proportion of emulsifier (10% SC) are dissolved in corn oil as the oil phase (corn oil accounts for 10% of the total volume). The aqueous phase and the oil phase are mixed to obtain Cur-10gSC as shown in Table 3.

[0066] NE-10gSC is based on Cur-NE-10gSC without the addition of curcumin.

[0067] Extraction and determination of heterocyclic amines: Take 5 g of sample powder, add 50 mL of 2 M NaOH, and extract with ultrasonic assistance (40 kHz, 30 min, 50 ℃). Add 30 mL of ethyl acetate, centrifuge at 3000 × g for 10 min, and collect the precipitate. Hydrolyze the precipitate with an equal volume of 6 M hydrochloric acid at 110 ℃ for 24 h, filter, dilute to 100 mL, and purify by solid-phase extraction. The contents of five heterocyclic amines (MeIQx, PhIP, Harman, Norharman, and 4,8-DiMeIQx) were determined by UPLC-MS / MS.

[0068] The results are shown in Table 3. All emulsion-coated groups showed better inhibition of heterocyclic amines than their corresponding non-emulsified control groups, confirming that the emulsified delivery system can significantly enhance the functionality of curcumin. Cur-NE-10gSC exhibited the most outstanding inhibitory effect, reducing the total heterocyclic amine content from 4.59 ng / mL in the control group to 0.30 ng / mL, with an inhibition rate of 93%, 99% for PhIP, and 97% for MeIQx. Its non-emulsified control group, Cur-10gSC, only achieved an inhibition rate of 63%. Cur-NE-10gMSP and Cur-NE-1gSSOS both achieved a total heterocyclic amine inhibition rate of approximately 84%; Cur-NE-1gSE and Cur-NE-10gSE achieved inhibition rates of 87% and 82%, respectively, consistent with their excellent thermal stability.

[0069] Table 3. Effects of different curcumin nanoemulsions on heterocyclic amine content in air-fried chicken wings (μg / 100g)

[0070] Note: Inhibition rate (%) = (Total HA content in control - Total HA content in treatment) / Total HA content in control × 100% Example 9: Penetration and Distribution of Nanoemulsion in Chicken Wing Skin The penetration depth and distribution uniformity of different nanoemulsions in chicken wing epidermis were observed using CLSM. The emulsion prepared in Example 1 was labeled with Nile Blue A (0.1%, w / v) and uniformly coated on the chicken wing epidermis. After incubation, skin tissue (approximately 1.5 cm × 0.5 cm) was taken, embedded by OCT, frozen sectioned (60 μm), and observed by CLSM (excitation wavelength 640 nm).

[0071] The results are as follows Figure 5As shown, the SE-stabilized emulsion exhibits the best permeability and uniform distribution characteristics in chicken wing epidermis, penetrating deep into the skin layer and forming a continuous coating. The SC-stabilized emulsion also shows good distribution uniformity. The MSP-stabilized emulsion has the shallowest penetration, limited distribution, and forms a discontinuous surface film. The SSOS-stabilized emulsion has uneven distribution and exhibits local aggregation. The excellent interfacial distribution characteristics of SE and SC are related to their high efficiency in inhibiting heterocyclic amines and their good sensory quality.

[0072] Example 10: Sensory Evaluation In accordance with the national standard GB / T 16291.1-2012, 20 trained sensory evaluators conducted a sensory evaluation of the fried chicken wings prepared in Example 8. The evaluation indicators included color, aroma, taste, greasiness, and overall acceptability, using a 9-point scale (1 point = extremely disliked, 9 points = extremely liked).

[0073] The results are shown in Table 4. All emulsion-treated samples scored within acceptable ranges in sensory evaluation. The SE-stabilized emulsion-treated group scored highest across multiple indicators, with significantly better scores in color (9.27) and taste (8.16) than the control group (7.59 and 8.27), attributed to the golden hue imparted by curcumin and the good surface texture created by the uniform coating. The SC-stabilized emulsion-treated group performed well in odor and taste, scoring comparable to or slightly higher than the control group. Other treatment groups scored within acceptable ranges, but slightly lower than the SE and SC groups.

[0074] Table 4 Sensory scores of air-fried chicken wings treated with different curcumin nanoemulsion coatings

[0075] Example 11: Effect of different emulsifier concentrations on the properties of nanoemulsions To investigate the effect of emulsifier concentration on the properties of nanoemulsions, curcumin nanoemulsions with sodium caseinate concentrations of 5%, 8%, 10%, and 12% (w / v) were prepared, and particle size, thermal stability, and heterocyclic amine inhibition rate were determined according to the methods in Examples 2, 4, and 8.

[0076] The results showed that as the sodium caseinate concentration increased from 5% to 10%, the emulsion particle size gradually decreased (5%: 198.3 nm; 8%: 175.6 nm; 10%: 164.1 nm), the PDI gradually decreased (5%: 0.246; 8%: 0.211; 10%: 0.187), the thermal stability (particle size change rate after treatment at 100℃ for 60 min) decreased from 18.3% to 6.7%, and the heterocyclic amine inhibition rate increased from 76% to 93%. When the concentration increased to 12%, the particle size slightly increased (172.4 nm), and the inhibition rate slightly decreased to 91%, indicating that 10% was the optimal concentration.

[0077] Comparative Example 1: Compared with direct addition of curcumin Following the method in Example 8, four groups were set up: a Cur-NE-10gSC treatment group, a Cur-10gSC non-emulsified treatment group (containing the same amount of curcumin and sodium caseinate, but not emulsified), an NE-10gSC treatment group (an emulsion without curcumin), and a curcumin-only treatment group (containing only 0.02% curcumin, without emulsifier). The inhibitory effects of the four groups on heterocyclic amines were compared.

[0078] The results showed that the total heterocyclic amine content in the Cur-NE-10gSC treatment group was 0.30 ng / mL, with an inhibition rate of 93%; the total heterocyclic amine content in the Cur-10gSC non-emulsified group was 1.68 ng / mL, with an inhibition rate of 63%; the total heterocyclic amine content in the NE-10gSC treatment group was 2.99 ng / mL, with an inhibition rate of 35%; and the total heterocyclic amine content in the curcumin-only treatment group was 2.87 ng / mL, with an inhibition rate of 37%. This indicates that curcumin plays an important role in the inhibitory effect of the emulsion. Furthermore, emulsification significantly enhanced the inhibitory effect of curcumin, while the effect of simply mixing with the unemulsified form was limited.

[0079] Comparative Example 2: Comparison of different oil phases According to the method in Example 1, curcumin nanoemulsions were prepared using 10% sodium caseinate as an emulsifier and corn oil, soybean oil, and rapeseed oil as the oil phase, respectively. The particle size and heterocyclic amine inhibition rate were determined according to Examples 2 and 8.

[0080] The results showed that corn oil had the smallest particle size (164.1 nm) and the highest inhibition rate (93%) when used as the oil phase; soybean oil was second (particle size 178.5 nm, inhibition rate 88%); rapeseed oil had a larger particle size (201.3 nm) and an inhibition rate of 64%. Corn oil, as the oil phase, exhibited superior overall performance.

[0081] Comparative Example 3: Comparison of different sugars According to the method of Example 1, curcumin nanoemulsions were prepared using 10% sodium caseinate as emulsifier and xylose, glucose and fructose (all at 3% w / v) as sugar components. The particle size and heterocyclic amine inhibition rate were determined according to Examples 2 and 8.

[0082] The results showed that the xylose group had the smallest particle size (164.1 nm) and the highest inhibition rate (93%); the glucose group had a particle size of 172.3 nm and an inhibition rate of 69%; and the fructose group had a particle size of 176.8 nm and an inhibition rate of 67%. Xylose, as a sugar component, exhibits superior overall performance.

[0083] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A curcumin nanoemulsion coating agent for inhibiting the formation of heterocyclic amines in heat-processed meat products, characterized in that, The coating agent is an oil-in-water nanoemulsion, comprising the following components: Curcumin, emulsifier, edible oil, sugar and water, wherein curcumin is encapsulated in a nanoemulsion; The emulsifier is a food-grade emulsifier selected from one or more of modified soybean lecithin, sodium caseinate, octenyl succinate starch ester, and sucrose fatty acid ester. The curcumin has a w / v concentration of 0.01% to 0.05% in the coating agent; the emulsifier has a w / v concentration of 1% to 10% in the coating agent.

2. The curcumin nanoemulsion coating agent according to claim 1, characterized in that, The emulsifier is sodium caseinate, and its w / v concentration in the coating agent is 8%~10%; Alternatively, the emulsifier may be a sucrose fatty acid ester, with a w / v concentration of 1% to 10% in the coating agent.

3. The curcumin nanoemulsion coating agent according to claim 1, characterized in that, The edible oil is one or more of corn oil, soybean oil, and rapeseed oil, and the volume fraction of the edible oil in the coating agent is 5% to 20%.

4. The curcumin nanoemulsion coating agent according to claim 1, characterized in that, The sugar is one or more of xylose, glucose, and fructose, and the w / v concentration of the sugar in the coating agent is 1% to 5%.

5. The curcumin nanoemulsion coating agent according to claim 1, characterized in that, The coating agent has an average particle size of 150~350 nm, PDI≤0.3, and absolute value of Zeta potential≥30 mV.

6. A method for preparing the curcumin nanoemulsion coating agent according to claims 1-5, characterized in that, Includes the following steps: (1) Dissolve sugars in water to form an aqueous phase; (2) Dissolve curcumin and emulsifier in edible oil to form an oil phase; (3) The aqueous phase and oil phase are mixed and subjected to high-speed shearing to obtain a crude emulsion; (4) The crude emulsion was subjected to high-pressure homogenization to obtain curcumin nanoemulsion coating agent.

7. The method for preparing the curcumin nanoemulsion coating agent according to claim 6, characterized in that, The rotational speed of the high-speed shearing in step (3) is 10,000~20,000 rpm, and the pressure of the high-pressure homogenization in step (4) is 20~30 MPa.

8. The application of the curcumin nanoemulsion coating agent according to claims 1-5, characterized in that, The coating agent is applied to the surface of meat products, which are then subjected to heat treatment to inhibit the formation of heterocyclic amines in the heat-processed meat products.

9. The application according to claim 8, characterized in that, The meat products include poultry, livestock and their products; the heat processing includes at least one of air frying, deep frying, grilling and pan-frying.

10. The application according to claim 8, characterized in that, The coating method is to immerse the meat product in the coating agent for 5 to 20 minutes, or to spray or brush the coating agent onto the surface of the meat product.

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