Essential oil double-layer composite slow-release barrier anti-oxidation film and preparation method thereof

Abstract

The invention belongs to the field of preparation of food packaging materials, and particularly relates to a double-layer composite slow-release barrier anti-oxidation film which is a multifunctional packaging material for food preservation. The preparation method comprises the following steps: encapsulating cumin essential oil in the form of Pickering emulsion, adding the cumin essential oil serving as a functional substance into a TOCNF / chitosan system, encapsulating again, and improving the ultraviolet barrier property, water vapor barrier property, oxygen barrier property and oxidation resistance of the composite membrane by using the Pickering emulsion, thereby preparing the novel composite membrane.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of food packaging material preparation, and particularly relates to a double-layer composite slow-release type barrier antioxidant film of essential oil and a preparation method thereof. BACKGROUND

[0002] According to the investigation of the World Health Organization, every year, one-tenth of the world's population is affected by food pollution, and many people die from it. Therefore, finding a safe and effective barrier antioxidant food active packaging has become an urgent matter. At present, petroleum-based plastics are the main food packaging materials, which provide convenience and efficiency, but the cost of their extensive use is serious environmental pollution and depletion of non-renewable resources. Among natural polymer materials, cellulose has the characteristics of non-toxicity, abundant source and high chemical resistance, which has attracted special attention in food packaging applications. Using green biologically active packaging materials to replace traditional petroleum-based materials is the current development trend.

[0003] Cumin essential oil contains cumin aldehyde, terpenes and phenols and other substances, has antioxidant, antibacterial and insect repellent functions, and has good effects in controlling aspergillus flavus and protecting meat, and the cost is relatively low, so it has attracted much attention in various fields. Most of the bioactive compounds of essential oil are volatile. The conventional method to stabilize essential oil is emulsion. As an alternative to traditional emulsion, Pickering emulsion is a solid particle stabilized emulsion, which has the characteristics of anti-coalescence stability, low toxicity or non-toxicity and low stabilizer dosage, so that the bioactive carrier molecules are released slowly and sustainably. The solid particles in it can interact with the active film matrix to improve the performance of the active film. In order to further encapsulate into nanostructure, under the TEMPO oxidation reaction of nanocellulose, the obtained TOCNF has a high density of functional groups such as hydroxyl and carboxyl groups on the surface, so it has extremely high surface free energy and excellent oxygen barrier property. Chitosan (CS) is a positively charged polymer derived from polysaccharides in the shells of crustaceans. Due to the presence of amino groups, it has excellent antibacterial properties, high water vapor permeability and low water solubility. The preparation of TOCNF / CS blended solution can overcome the single disadvantage and achieve the encapsulation of essential oil emulsion. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings in the prior art and provide a double-layer composite slow-release type barrier antioxidant film of essential oil and a preparation method thereof.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is:

[0006] The application discloses a preparation method of an essential oil double-layer composite sustained-release barrier antioxidant film, and comprises the following steps: 1) preparing a Pickering emulsion of sodium caseinate / beta-cyclodextrin / tween-20 composite solid particles coated with cumin essential oil; and 2) adding the product obtained in the step 1) into a TOCNF / chitosan mixed solution to perform re-encapsulation to obtain the double-layer composite sustained-release barrier antioxidant film.

[0007] The specific steps of the step 1) are as follows: sodium caseinate, beta-cyclodextrin and tween-20 are added into deionized water to perform reaction, and after the reaction is completed, a sodium caseinate / beta-cyclodextrin / tween-20 composite solid particle solution is obtained; and cumin essential oil is high-speed homogenized to obtain a Pickering emulsion of the cumin essential oil.

[0008] The percentage of the sodium caseinate, the beta-cyclodextrin and the tween-20 is (2-6%):(1-5%):(1-5%), and the percentage of the sodium caseinate / beta-cyclodextrin / tween-20 composite solid particles and the cumin essential oil is (4-16%):(10-20%).

[0009] The reaction temperature of the step 1) is specifically 30-80 DEG C, the reaction time is 2-5h, the homogenization speed is 18000-22000 rpm, and the homogenization time is 4-10 min.

[0010] The specific steps of the step 2) are as follows: TOCNF is uniformly dispersed to obtain a TOCNF solution, chitosan is added into an acetic acid solution and uniformly dispersed to obtain a chitosan solution, the above-mentioned solutions are uniformly mixed with glycerol respectively, then homogenization and dispersion are performed according to the proportion, the Pickering emulsion of the cumin essential oil is added into the mixed solution to perform shearing homogenization and re-encapsulation, and then the film is formed by pouring into a polytetrafluoroethylene plate and drying at 60-70 DEG C for 36h.

[0011] The mass ratio of the TOCNF, the chitosan and the glycerol is (1-3):(7-9):(0.2-0.4), the acetic acid solution is 0.01-0.2M, and the percentage of the TOCNF / chitosan mixed solution and the Pickering emulsion is (95-100%):(0-5%).

[0012] The homogenization speed is 8000-15000 rpm, and the homogenization time is 8-15 min.

[0013] Compared with the prior art, the application has the beneficial effects that:

[0014] The essential oil is encapsulated in the form of a Pickering emulsion, and then the Pickering emulsion is added into a TOCNF / chitosan system as a functional substance to perform re-encapsulation, so that a novel composite film is prepared.

[0015] Cuminum cyminum L. essential oil (CEO) contains cumin aldehyde, terpenes and phenols, etc. It has antioxidant, antibacterial and insect repellent functions, and has good effect on controlling aspergillus flavus and protecting meat. It is low in cost, so it has attracted much attention in various fields. Most bioactive compounds of essential oil are volatile. Pickering emulsion is a solid particle stabilized emulsion, which has the characteristics of anti-coalescence stability, low toxicity or non-toxicity, and low dosage of stabilizer, so that the bioactive carrier molecules are released slowly and continuously. The solid particles in it can interact with the active film matrix to improve the performance of the active film.

[0016] Under the TEMPO oxidation reaction, the obtained TOCNF has a high density of functional groups such as hydroxyl and carboxyl groups on the surface, so it has a very high surface free energy and excellent oxygen barrier property.

[0017] Chitosan (CS) is a positively charged polymer derived from polysaccharides from the shells of crustaceans. Due to the presence of amino groups, it has excellent antibacterial properties, film-forming properties, and low water solubility. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The Fourier transform infrared absorption spectrum of the infrared spectrum of the essential oil, emulsion, TCP0, TCP2, TCO prepared for Examples 1-2 and Comparative Examples 1-2;

[0019] Figure 2 The UV-Vis light transmittance curve of TCP0, TCP1, TCP2, TCP3, TCO prepared for Example 1-3 and Comparative Example 1-2;

[0020] Figure 3 The water vapor transmission amount of TCP0, TCP1, TCP2, TCP3, TCO prepared for Example 1-3 and Comparative Example 1-2;

[0021] Figure 4 The oxygen transmission amount of TCP0, TCP1, TCP2, TCP3, TCO prepared for Example 1-3 and Comparative Example 1-2;

[0022] Figure 5 The DPPH clearance rate of TCP0, TCP1, TCP2, TCP3, TCO prepared for Example 1-3 and Comparative Example 1-2;

[0023] Figure 6 The essential oil release rate of TCP1, TCP2, TCP3, TCO prepared for Example 1-3 and Comparative Example 2. DETAILED DESCRIPTION

[0024] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in combination with the drawings and the best mode.

[0025] Example 1

[0026] The preparation method of the essential oil double-layer composite slow-release type barrier antioxidant film described in this embodiment comprises the following steps:

[0027] (1) Add β-CD (1.45%, w / v) to deionized water at 70°C, stir at 800 rpm until completely dissolved, and then cool to 45°C. Next, mix the aqueous solutions of Tween-20 (2.76%, w / v) and sodium caseinate (5.79%, w / v) at 45°C, and then add them to the β-CD solution. After thorough mixing, cool the suspension to room temperature and continuously stir at 500 rpm for 3 hours.

[0028] (2) Prepare an oil-in-water Pickering nanoemulsion with β-CD: heat the above suspension and maintain it at 45°C, drop cumin essential oil into the water phase containing the emulsifier mixture, and then stir at 800 rpm for about 30 minutes. Finally, homogenize the emulsion by a high-speed homogenizer at 20000 rpm for 6 min to obtain a Pickering nanoemulsion containing cumin essential oil

[0029] (3) Dissolve TOCNF in ultrapure water at 75°C for 2h to form a TOCNF solution (0.2%, w / v), and then add 30% (w / w, based on dry mass) of glycerol to the TOCNF solution to obtain a TOCNF solution. Dissolve chitosan in an aqueous acetic acid solution (0.1M) in a 60°C water bath for 2h to form a chitosan solution (1%, w / v), and then add 30% (w / w, based on the dry weight of chitosan) of glycerol to the chitosan solution. Mix the TOCNF solution and the chitosan solution to form a mixed solution.

[0030] (4) Shear mix the 2% Pickering emulsion with the mixed solution to re-encapsulate, with a total volume of 30mL. Such a mixture is treated with a high-speed homogenizer at 10000 rpm and room temperature for 15 minutes, and then ultrasonically treated at 25°C for 15 minutes to remove air bubbles, to obtain a film-forming liquid. Finally, completely pour the film-forming liquid onto a polytetrafluoroethylene plate with a diameter of 10cm, and dry it at 60°C for 36 hours.

[0031] Example 2

[0032] The difference between Example 2 and Example 1 is only that the amount of Pickering emulsion added in step (4) is different, specifically 2%.

[0033] Example 3

[0034] Example 3 differs from Example 1 only in that the amount of Pickering emulsion added in step (4) is different, specifically 3%.

[0035] Comparative Example 1

[0036] Comparative Example 1 differs from Example 1 in that it does not contain a Pickering emulsion, and is prepared using the following steps:

[0037] (1) TOCNF was dissolved in ultrapure water at 75 °C for 2 h to form a TOCNF solution (0.2%, w / v), then 30% (w / w, based on dry mass) of glycerol was added to the TOCNF solution to obtain a TOCNF solution. Chitosan was dissolved in an aqueous acetic acid solution (0.1 M) in a water bath at 60 °C for 2 h to form a chitosan solution (1%, w / v), then 30% (w / w, based on chitosan dry weight) of glycerol was added to the chitosan solution. The TOCNF solution and the chitosan solution were mixed in proportion to form a mixed solution.

[0038] (2) The mixed solution was treated with a high-speed homogenizer at 10000 rpm and room temperature for 15 minutes, and then ultrasonically treated at 25 °C for 15 minutes to remove bubbles, to obtain a film-forming liquid. Finally, the film-forming liquid was completely cast on a polytetrafluoroethylene plate with a diameter of 10 cm and dried at 60 °C for 36 hours.

[0039] Comparative Example 2

[0040] Comparative Example 2 differs from Example 1 in that the essential oil is not coated by a Pickering emulsion, and is prepared using the following steps:

[0041] (1) TOCNF was dissolved in ultrapure water at 75 °C for 2 h to form a TOCNF solution (0.2%, w / v), then 30% (w / w, based on dry mass) of glycerol was added to the TOCNF solution to obtain a TOCNF solution. Chitosan was dissolved in an aqueous acetic acid solution (0.1 M) in a water bath at 60 °C for 2 h to form a chitosan solution (1%, w / v), then 30% (w / w, based on chitosan dry weight) of glycerol was added to the chitosan solution. The TOCNF solution and the chitosan solution were mixed in proportion to form a mixed solution.

[0042] (2) The same amount of cumin essential oil as 2% Pickering emulsion was mixed with the mixed solution, with a total volume of 30 mL. Such a mixture was treated with a high-speed homogenizer at 10000 rpm and room temperature for 15 minutes, and then ultrasonically treated at 25 °C for 15 minutes to remove bubbles, to obtain a film-forming liquid. Finally, the film-forming liquid was completely cast on a polytetrafluoroethylene plate with a diameter of 10 cm and dried at 60 °C for 36 hours.

[0043] Tests and Results:

[0044] Figure 1 Fourier transform infrared absorption spectra of essential oils, emulsions, TCP0, TCP2, and TCO prepared in Examples 1-2 and Comparative Examples 1-2 are shown.

[0045] Depend on Figure 1 It can be seen that the essential oil is 1739cm -1 The presence of cuminaldehyde was observed, with a slight peak in the emulsion indicating that most of the essential oils were successfully emulsified by the particles. At 3286 cm⁻¹ in TCP2... -1 The peak becomes sharper, 1560cm -1 Further shift of the N-H of the nearby amide II, and the addition of the emulsion, enhanced the hydrogen bonding and electrostatic interactions with TOCNF / CS, resulting in further encapsulation. 1739cm -1 The presence of this indicates that the essential oil component cuminaldehyde is being released within the membrane system.

[0046] Figure 2 The UV-Vis transmittance curves of TCP0, TCP1, TCP2, TCP3, and TCO prepared in Examples 1-3 and Comparative Examples 1-2 are shown.

[0047] Figure 2 The results indicate that the addition of the emulsion significantly reduces the UV transmittance of the composite film in the 200-400 nm range, which is attributed to the UV-absorbing compounds in CEO.

[0048] Figure 3 The diagram shows the water vapor permeation rates of TCP0, TCP1, TCP2, TCP3, and TCO prepared in Examples 1-3 and Comparative Examples 1-2. Figure 3 The results show that, compared with the TCP0 membrane, the addition of the emulsion reduced the WVTR of the TOCNF / CS membrane by approximately 60% under 38° / 90% RH conditions.

[0049] Figure 4 The diagram shows the oxygen permeation rates (OTR) of TCP0, TCP1, TCP2, TCP3, and TCO prepared in Examples 1-3 and Comparative Examples 1-2. The addition of the emulsion increased the OTR of the TOCNF / CS membrane from 75.866 cm⁻¹. 3 / m 2 • 24h • 0.1MPa decreased to 56.05

[0050] cm 3 / m 2 • 24h • 0.1MPa. The addition of pure essential oils makes the film less effective at blocking oxygen.

[0051] Figure 5The DPPH clearance rate of TCP0, TCP1, TCP2, TCP3, TCO prepared by Example 1-3 Comparative Example 1-2 is shown in the figure, and the results show that the DPPH clearance rate is increased from 9.42% of TCP0 film to 19.08% of TCP3 after adding the emulsion; under the same essential oil addition amount, the clearance rate of TCO is 18.17%, slightly higher than that of TCP2, because the essential oil release rate of TCO is higher than that of TCP2, and the Pickering emulsion has a slow-release characteristic for essential oil.

[0052] Figure 6 The essential oil slow-release rate of TCP1, TCP2, TCP3, TCO prepared by Example 1-3 Comparative Example 2 is shown in the figure, and the results show that the film of cumin essential oil loaded by Pickering exhibits a sustained release behavior, and the essential oil release of the film can be adjusted by changing the Pickering content.

[0053] As can be seen from the above, the essential oil double-layer composite slow-release type barrier antioxidant film of the present application encapsulates cumin essential oil in the form of Pickering emulsion, and then adds it as a functional substance into the TOCNF / chitosan system for re-encapsulation to prepare a new type of slow-release composite film. The double-layer slow-release purpose is achieved for essential oil, and the ultraviolet barrier, water vapor barrier, oxygen barrier performance and antioxidant capacity of the composite film are improved.

[0054] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a double-layered composite barrier and antioxidant film of essential oils, characterized in that: The preparation method comprises the following steps: 1) preparing a Pickering emulsion of cased cumin essential oil coated with sodium caseinate / β-cyclodextrin / tween-20 composite solid particles; 2) adding the product obtained in step 1) to a TOCNF / chitosan mixed solution to re-encapsulate to obtain a double-layer composite slow-release barrier antioxidant film.

2. The method for preparing a double-layer composite barrier and antioxidant film of essential oil according to claim 1, characterized in that, The specific steps of step 1) are as follows: sodium caseinate, β-cyclodextrin and tween-20 are added to deionized water for reaction to obtain a sodium caseinate / β-cyclodextrin / tween-20 composite solid particle solution. The percentage of sodium caseinate, β-cyclodextrin and tween-20 is (2-6%):(1-5%):(1-5%), and the reaction temperature is specifically 30-80°C, and the reaction time is 2-5h.

3. The method for preparing a double-layer composite barrier and sustained-release type antioxidant film of essential oil according to claim 1, characterized in that, The specific steps of step 1) are as follows: cumin essential oil is added to the sodium caseinate / β-cyclodextrin / tween-20 composite solid particle solution for high-speed homogenization to obtain a Pickering emulsion coated with cumin essential oil. The percentage of sodium caseinate / β-cyclodextrin / tween-20 composite solid particles to cumin essential oil is (4-16%):(10-20%), the homogenization speed is 18000-22000rpm, and the homogenization time is 4-10min.

4. The method for preparing a double-layer composite barrier and antioxidant film of essential oil according to claim 1, characterized in that, The specific steps of step 2) are as follows: TOCNF is uniformly dispersed to obtain a TOCNF solution, chitosan is added to an acetic acid solution and uniformly dispersed to obtain a chitosan solution, and the above solutions are uniformly mixed with glycerol, then homogenized and dispersed in proportion, the mass ratio of TOCNF, chitosan and glycerol is (1-3):(7-9):(0.2-0.4), the acetic acid solution is 0.01-0.2M, the homogenization speed is 8000-15000rpm, and the homogenization time is 8-15min.

5. The method of claim 1, wherein the method of preparing a double-layered composite barrier and sustained-release type antioxidant film of essential oil is characterized by, The Pickering emulsion coated with cumin essential oil is added to the TOCNF / chitosan mixed solution, the shearing homogenization speed is 8000-15000rpm, the homogenization time is 2-10min, the percentage of TOCNF / chitosan mixed solution to Pickering emulsion is (95-100%):(0-5%), and re-encapsulation is performed. Pouring in a polytetrafluoroethylene plate and drying at 60-70°C for 36h to form a film.

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