CN113150560B

CN113150560B - pH colorimetric sensing membrane, preparation method and application thereof

Info

Publication number: CN113150560B
Application number: CN202110125241.9A
Authority: CN
Inventors: 王丽; 王娇; 孙新玉; 张辉; 董梦娜; 李丽华
Original assignee: Northwest A&F University
Current assignee: Northwest A&F University
Priority date: 2021-01-29
Filing date: 2021-01-29
Publication date: 2022-09-20
Anticipated expiration: 2041-01-29
Also published as: CN113150560A

Abstract

A pH colorimetric sensing film, its preparation method and application, the raw materials include film forming matrix, plasticizer and alizarin solution. The pH colorimetric sensing film changes from yellow with low pH value to purple with high pH value according to the change of acid-base conditions, and the color change reappears under repeated pH change; meanwhile, when the meat product is deteriorated, the acid-base environment of the meat product is changed due to the growth increase of microorganisms and the generation of biogenic amine, the pH colorimetric sensing film shows great potential application in the freshness monitoring of the food meat, and the whole pH colorimetric sensing film has the advantages of convenience and rapidness in use, safety, no toxicity, degradability, edibility, potential in food pH monitoring and the like.

Description

pH colorimetric sensing membrane, preparation method and application thereof

Technical Field

The invention belongs to the technical field of food engineering, and particularly relates to a pH colorimetric sensing membrane, a preparation method and application thereof.

Background

The explosive growth of food waste and the problem of food safety are always one of the focus scientific problems which are continuously concerned by all the social circles, pork is edible meat with the largest consumption in China, and fresh meat is one of the development directions of meat industry for fresh meat preservation and packaging storage. The freshness of meat refers to the basic nitrogen-containing substances such as ammonia, amines and the like, which are generated by decomposing proteins in the putrefaction process of animal food due to the action of enzymes and bacteria, such as ammonia gas, dimethylamine, trimethylamine and the like. The volatile basic nitrogen has definite corresponding relation with the putrefaction and deterioration of animal food, and is an important index of food hygiene inspection standard, especially for fresh meat and meat products. Although a plurality of physicochemical experimental methods and sensory evaluation methods can judge the freshness of pork, the traditional method has the limitations of complex operation, time and labor consumption, high technical requirements on experimenters and the like.

Disclosure of Invention

Aiming at the defects and shortcomings in the prior art, the pH colorimetric sensing membrane, the preparation method and the application thereof are adopted, the pH colorimetric sensing membrane is changed from yellow with low pH value to purple with high pH value according to the change of acid-base conditions, and the color change can reappear under the repeated pH change; meanwhile, when the meat product is deteriorated, the acid-base environment of the meat product is changed due to the growth increase of microorganisms and the generation of biogenic amine, the pH colorimetric sensing film shows great potential application in the freshness monitoring of the food meat, and the whole pH colorimetric sensing film has the advantages of convenience and rapidness in use, safety, no toxicity, degradability, edibility, potential in food pH monitoring and the like.

In order to achieve the technical effects, the technical scheme adopted by the invention is as follows:

a pH colorimetric sensing film comprises raw materials including a film forming matrix and a plasticizer, wherein the raw materials include the film forming matrix, the plasticizer and an alizarin solution.

Further, the raw materials also comprise an antibacterial solution, the alizarin solution and the antibacterial solution are mixed to prepare a mixed solution, the components of the alizarin solution and the antibacterial solution in the mixed solution are respectively 50% -100% and 50% -0, and the component of the antibacterial solution is not 0.

Preferably, the alizarin solution is prepared by mixing alizarin emulsion and ultrapure water according to the volume ratio of 1 (9-10); the alizarin emulsion is prepared by mixing alizarin and ethanol with the solid-to-liquid ratio of (2-6) to 1 g/L.

Preferably, the antibacterial solution is prepared by mixing lavender essential oil and gelatin nanoparticle solution in a volume ratio of 4 (45-47); the gelatin nano-particle solution is prepared from the following components in a mass ratio of 1: (499-500) by mixing the gelatin nanoparticles with ultrapure water.

Preferably, the pH colorimetric sensing membrane is prepared by adding 40g/L of membrane forming matrix and 10g/L of plasticizer into the mixed solution or alizarin solution, mixing and degassing at 45 +/-1 ℃ to obtain membrane forming solution, spreading the membrane forming solution to the thickness of 4 +/-0.5 mm, and forming the membrane at the temperature of 23 +/-0.5 ℃, the humidity of 50 +/-3% and the membrane forming time of 24-48 hours.

Preferably, the film forming matrix is gelatin and the plasticizer is glycerol.

The invention discloses a preparation method of a pH colorimetric sensing film, which comprises the following steps:

step 1, preparation of alizarin solution: mixing alizarin and ethanol at a solid-liquid ratio of (2-6) to 1g/L to obtain alizarin emulsion, and mixing the alizarin emulsion and ultrapure water at a volume ratio of 1 (9-10) to obtain an alizarin solution;

step 2, preparing a film forming solution: adding 40g/L of film forming matrix and 10g/L of plasticizer into the alizarin solution obtained in the step 1, and mixing and degassing at the temperature of 45 +/-1 ℃ to obtain a film forming solution;

and 3, spreading the film-forming solution obtained in the step 2 to a thickness of 4 +/-0.5 mm, and forming the film at a temperature of 23 +/-0.5 ℃, a humidity of 50 +/-3% and a film-forming time of 24-48h to obtain the pH colorimetric sensing film.

Further, the method also comprises the following steps:

step 4, preparing an antibacterial solution: mixing the components in a mass ratio of 1: (499-500) mixing the gelatin nano-particles with ultrapure water to obtain a gelatin nano-particle solution, and then mixing the lavender essential oil with the volume ratio of 4 (45-47) with the gelatin nano-particle solution to obtain an antibacterial solution;

step 5, preparing a mixed solution: mixing the alizarin solution obtained in the step 1 and the antibacterial solution obtained in the step 4 to obtain a mixed solution, wherein the components of the alizarin solution and the antibacterial solution in the mixed solution are respectively 50% -100% and 50% -0, and the component of the antibacterial solution is not 0;

step 6, preparing an antibacterial film forming solution: adding 40g/L of film forming matrix and 10g/L of plasticizer into the mixed solution obtained in the step 5, and mixing and degassing at the temperature of 45 +/-1 ℃ to obtain an antibacterial film forming solution;

and 7, spreading the antibacterial film-forming solution obtained in the step 6 to a thickness of 4 +/-0.5 mm, and forming the film at a temperature of 23 +/-0.5 ℃, a humidity of 50 +/-3% and a film-forming time of 24-48h to obtain the pH colorimetric sensing film.

Preferably, the film forming matrix is gelatin and the plasticizer is glycerol.

The invention discloses an application of a pH colorimetric sensing film used as a meat food packaging film.

Due to the adoption of the technical scheme, the method has the following beneficial effects:

(1) according to the pH colorimetric sensing membrane, the preparation method and the application thereof, the sensing membrane is changed from yellow with a low pH value to purple with a high pH value according to the change of acid-base conditions; meanwhile, when the meat product is deteriorated, the acid-base environment of the meat product is changed due to the growth increase of microorganisms and the generation of biogenic amine, and the pH colorimetric sensing film has great potential application in the freshness monitoring of the food meat.

(2) According to the pH colorimetric sensing film, the preparation method and the application of the pH colorimetric sensing film, the yellow color with low pH value is changed into the purple color with high pH value, and the color change can reappear under repeated pH change, so that the practicability of indicating the freshness of food by the pH colorimetric sensing film is increased.

(3) The pH colorimetric sensing film, the preparation method and the application thereof have good antibacterial performance, can prevent external microorganisms from contacting with food, and inhibit the food from rotting, thereby achieving the effects of keeping the food fresh and prolonging the shelf life.

(4) According to the pH colorimetric sensing membrane, the preparation method and the application thereof, the raw material source is wide, and alizarin is a green, natural, non-toxic and harmless raw material; the whole body has the advantages of convenient use, safety, no toxicity, degradability, edibility, potential of monitoring the pH value of food and the like.

Drawings

FIG. 1 is an SEM image of a conventional adhesive film and a pH colorimetric sensor film according to the present invention;

(wherein FIG. 1a is an SEM picture of a conventional adhesive film prepared in example 1; FIG. 1b is an SEM picture of a pH colorimetric sensor film prepared in example 2; FIG. 1c is an SEM picture of a pH colorimetric sensor film prepared in example 3; FIG. 1d is an SEM picture of a pH colorimetric sensor film prepared in example 4; FIG. 1e is an SEM picture of a pH colorimetric sensor film prepared in example 5.)

FIG. 2 is a comparative XRD pattern for examples 1-5;

FIG. 3 is a comparison of tensile stress strain curves for examples 1-5;

FIG. 4 is a graph comparing tensile strength and elongation at break for examples 1-5, wherein the different letters in the graph indicate significant differences (P ≦ 0.05);

FIG. 5 is a graph comparing the thicknesses of examples 1-5, wherein the different letters in the graph indicate significant differences (P ≦ 0.05);

FIG. 6 is a graph comparing light transmittance of examples 1-5;

FIG. 7 is a graph comparing the water vapor transmission rates of examples 1-5, wherein the different letters in the graph indicate significant differences (P ≦ 0.05);

FIG. 8 is a graph comparing the sterilization rates of examples 1-5, with different letters indicating significant differences (P.ltoreq.0.05);

the invention is described in detail below with reference to the drawings and the detailed description.

Detailed Description

Alizarin, lavender essential oil, gelatin and glycerin in this example are all existing materials, wherein alizarin and lavender essential oil are all purchased from Shanghai Merlin Biochemical Co., Ltd, gelatin is purchased from Chengdu Kelong chemical Co., Ltd, and glycerin is purchased from the development area of the Magnolia town industry in New City of Chengdu City in China.

The gelatin nanoparticles of the embodiment are any available material purchased on the market, and can also be prepared by adopting an existing two-step desolventizing method, and specifically comprise the following steps: 1.25g of gelatin was dissolved in 25ml of ultrapure water, and heated at 45 ℃ with continuous stirring to obtain a gelatin solution. Subsequently, 25mL of acetone was added, desolventized, high molecular weight gelatin was precipitated, and the supernatant was discarded. Then, 25mL of ultrapure water was added to the remaining solution to adjust the pH of the solution to 12. Then 75ml of acetone were added dropwise and 10 min was stirred, glutaraldehyde (250. mu.L, 25%) was added to crosslink the particles, and stirring was continued for 16 h. And concentrating and freeze-drying the obtained solution to obtain the gelatin nano-particles.

Example 1

This embodiment is a method for preparing a conventional pure gelatin film, including the following steps:

(1) preparing a pure gelatin film forming solution: weighing 0.4g of gelatin, adding the gelatin into 10mL of ultrapure water, magnetically stirring in a constant-temperature water bath at 45 ℃ until the gelatin is completely dissolved, adding 0.1g of glycerol as a plasticizer, continuously stirring the film forming solution under the condition of the constant-temperature water bath until the film forming solution is uniformly mixed, and ultrasonically degassing for 15 min to obtain the uniform pure gelatin film forming solution.

(2) Preparing a pure gelatin film: measuring 10mL of the film-forming liquid, pouring and spreading the film-forming liquid into an organic glass film-forming die (120mm multiplied by 80mm multiplied by 4mm), wherein the film-forming temperature is 23 +/-0.5 ℃, the humidity is 50 +/-3%, and the film-forming time is 24-48h, and then manually removing the film to obtain the pure gelatin film.

The surface of the prepared pure gelatin film was subjected to SEM measurement, and the result is shown in fig. 1 a.

The pure gelatin film prepared in this example was measured for XRD, tensile stress-strain curve, tensile strength and elongation at break, thickness, light transmittance, water vapor transmittance, and sterilization rate, and the results are sequentially shown in fig. 2 to 8.

Analyzing the material structure in the pure gelatin membrane by X-ray diffraction (XRD); the tensile stress-strain curve, the tensile strength, the elongation at break and the thickness represent the physical and mechanical properties of the pure gelatin film, the shape of the tensile stress-strain curve reflects the deformation process of the pure gelatin film under the action of external force, the tensile strength represents the maximum tensile stress which can be borne by the pure gelatin film at the breaking point, and the elongation at break represents the elastic property of the pure gelatin film; the light transmittance and the water vapor transmission rate characterize the barrier performance of the film to light rays and water vapor. The antibacterial performance of the pure gelatin film is determined by the inhibition and killing effect on escherichia coli and staphylococcus aureus.

The surface of the pure gelatin film of the embodiment is smooth, and the section has no gap, so that the pure gelatin film has poor toughness and elasticity, and hard texture, and is not suitable for food packaging. The pure gelatin film has the advantages of thin thickness, high light transmittance and water vapor transmission rate, poor light and water vapor blocking effect, basically no antibacterial effect and no PH indicating effect.

Example 2

The embodiment is a method for preparing a pH colorimetric sensing membrane, which includes the following steps:

step 1, preparation of alizarin solution: 30mg of alizarin is weighed in a 10mL test tube, 5mL of ethanol is added for dissolving, 1mL of alizarin ethanol solution is measured, the alizarin ethanol solution is added into 9mL of ultrapure water solution, and the solution is stirred by magnetic force until the concentration is uniform, so that the alizarin solution with the concentration of 6mg/mL is obtained.

Step 2, preparing an antibacterial solution: mixing 0.5 wt% of gelatin nanoparticles with 8% of lavender essential oil to obtain the stable antibacterial solution of gelatin nanoparticles.

Step 3, preparing a mixed solution: and (3) mixing the alizarin solution with the concentration of 6mg/mL obtained in the step (1) and the antibacterial solution obtained in the step (2) according to the volume ratio of 1:1 to obtain a mixed solution.

Step 4, preparing an antibacterial film forming solution: weighing 0.4g of gelatin, adding the gelatin into 10mL of the mixed solution obtained in the step 3, magnetically stirring in a 45 ℃ constant-temperature water bath until the gelatin is completely dissolved, adding 0.1g of glycerol as a plasticizer, continuously stirring under the 45 ℃ constant-temperature water bath condition until the gelatin is uniformly mixed, and ultrasonically degassing for 15 min to obtain a uniform antibacterial film-forming solution.

Step 5, preparing a pH colorimetric sensing film: measuring 10mL of the antibacterial film-forming solution obtained in the step 4, pouring and spreading the antibacterial film-forming solution into an organic glass film-forming mold (120mm multiplied by 80mm multiplied by 4mm), forming the film at the film-forming temperature of 23 +/-0.5 ℃, the humidity of 50 +/-3 percent and the film-forming time of 24-48h, and manually removing the film to obtain the pH colorimetric sensing film.

SEM measurement was performed on the surface of the prepared pH colorimetric sensor film, and the result is shown in fig. 1 b.

Compared with example 1, the pH colorimetric sensor film obtained in example 2 has no great difference between the surface and the cross section, but the tensile strength is reduced and the elongation at break is increased due to the addition of the antibacterial solution, so that the sensor film has good toughness and soft texture. The thickness of the sensor film is increased along with the addition of the alizarin and the antibacterial solution, and the barrier performance of the sensor film to light and water vapor is improved. The antibacterial solution endows the sensing membrane with certain performance of inhibiting the growth of escherichia coli and staphylococcus aureus and also has an obvious PH indicating effect.

Example 3

The embodiment is a method for preparing a pH colorimetric sensor film, which includes the following steps:

step 1, preparation of alizarin solution: weighing 20mg of alizarin into a 10mL test tube, adding 5mL of ethanol for dissolving, measuring 1mL of alizarin ethanol solution, adding the alizarin ethanol solution into 9mL of ultrapure water solution, and magnetically stirring until the alizarin ethanol solution is uniform to obtain an alizarin solution with the concentration of 4 mg/mL.

Step 2, the preparation of the antimicrobial solution was identical to step 2 of example 2.

Step 3, preparing a mixed solution: and (3) mixing the alizarin solution with the concentration of 4mg/mL obtained in the step (1) with the antibacterial solution obtained in the step (2) according to the volume ratio of 1:1 to obtain a mixed solution.

Step 4, preparation of the antibacterial-deposition-solution deposition solution was made in accordance with step 4 of example 2.

Step 5, preparation of the pH colorimetric sensor film was identical to step 5 of example 2.

SEM measurement was performed on the surface of the prepared pH colorimetric sensor film, and the result is shown in fig. 1 c.

Compared with the example 1, the pH colorimetric sensing film obtained in the example 3 has a smooth surface and a reticular structure in cross section, which may be a reason for further increasing the elongation at break, so that the toughness and elasticity of the sensing film are greatly improved, the texture is soft, and the pH colorimetric sensing film is suitable for food packaging. Compared with the pH colorimetric sensor film obtained in example 1 and example 3, the thickness of the sensor film is increased, and the barrier performance of the sensor film to light and water vapor is improved. The pH colorimetric sensing membrane obtained in example 3 has strong inhibition and killing effects on Escherichia coli and Staphylococcus aureus, and also has an obvious pH indicating effect.

Example 4

step 1, preparation of alizarin solution: weighing 10mg of alizarin in a 10mL test tube, adding 5mL of ethanol for dissolving, measuring 1mL of alizarin ethanol solution, adding the alizarin ethanol solution into 9mL of ultra-pure water solution, and performing magnetic stirring until the alizarin solution with the concentration of 2mg/mL is uniform.

Step 3, preparing a mixed solution: and (3) mixing the alizarin solution with the concentration of 2mg/mL obtained in the step (1) and the antibacterial solution obtained in the step (2) according to the volume ratio of 1:1 to obtain a mixed solution.

Step 4, preparation of the antibacterial deposition solution was identical to step 4 of example 2.

SEM measurement was performed on the surface of the prepared pH colorimetric sensor film, and the result is shown in fig. 1 d.

Compared with the pH colorimetric sensing film obtained in the embodiment 1, the pH colorimetric sensing film obtained in the embodiment 4 has a smooth surface and a regular net-shaped cross section, so that the elongation at break is increased to the maximum, the toughness and the elasticity of the sensing film are further improved, the texture is softer, and the pH colorimetric sensing film is suitable for packaging food. Compared with example 1, the thickness of the pH colorimetric sensor film obtained in example 4 is increased, and the blocking performance of the sensor film on light and water vapor is improved. The pH colorimetric sensor film obtained in example 4 has strong inhibition and killing effects on Escherichia coli and Staphylococcus aureus, and also has an obvious pH indicating effect.

Example 5

step 1, the alizarin solution was prepared in accordance with step 1 of example 2.

Step 2, preparing a film forming solution: weighing 0.4g of gelatin, adding the gelatin into 10mL of the alizarin solution obtained in the step 1, magnetically stirring in a 45 ℃ constant-temperature water bath until the gelatin is completely dissolved, adding 0.1g of glycerol as a plasticizer, continuously stirring under the 45 ℃ constant-temperature water bath condition until the gelatin is uniformly mixed, and ultrasonically degassing for 15 min to obtain a uniform film-forming solution.

SEM measurement was performed on the surface of the prepared pH colorimetric sensor film, and the result is shown in fig. 1 e.

Compared with the example 1, the pH colorimetric sensing film obtained in the example 5 has the advantages of smooth surface, similar cross section to that of the example 1, minimum breaking elongation and tensile strength, poorer toughness and strength, harder texture and increased thickness, and the light and water vapor barrier performance of the sensing film is improved. The pH colorimetric sensor film obtained in example 5 has no inhibiting and killing effect on Escherichia coli and Staphylococcus aureus, but has obvious pH indicating effect.

Example 6

The pure gelatin film obtained in example 1 and the pH colorimetric sensor films obtained in examples 3 and 4 were placed at different pH values, and the color changes thereof are shown in table 1. The pH colorimetric sensing film prepared by the invention has color conversion from yellow to purple under the environment of pH 2, 5, 6, 7, 9 and 11 respectively.

Wherein L in table 1 represents the brightness (black and white), a represents the red and green, b represents the yellow and blue, Δ E the total color difference; values are expressed as mean ± sd, values of different letters after the same row differ significantly (p ≦ 0.05).

In the embodiment, the color change of the pure gelatin film/or the pH colorimetric sensing film is measured by a spectrocolorimeter; the spectrophotometer is purchased from Hangzhou color spectrum science and technology company, and has the model number of CS-820.

TABLE 1

The pH colorimetric sensor film prepared in example 4 was suspended in an erlenmeyer flask containing 80mL of ammonia solution (0.8M) at 25 ℃ for 10 minutes, or the pH colorimetric sensor film was exposed to ammonia gas for 10 minutes; the pH colorimetric sensor film was then suspended in acetic acid solution (99.7%) for 10 minutes at 25 ℃. The process is repeated for 3 times to test the reversibility of the indicator membrane under different pH values, and the result is shown in table 1 (when the pH colorimetric sensing membrane is exposed to ammonia gas, the pH colorimetric sensing membrane is purple, and when the pH colorimetric sensing membrane is exposed to acetic acid, the pH colorimetric sensing membrane is yellow), so that the color indication of the prepared pH colorimetric sensing membrane under different acid-base environments has reversibility.

TABLE 2

Claims

1. A pH colorimetric sensing membrane comprises raw materials including a membrane forming matrix and a plasticizer, and is characterized in that the raw materials include the membrane forming matrix, the plasticizer and an alizarin solution;

the raw materials also comprise an antibacterial solution, the alizarin solution and the antibacterial solution are mixed to prepare a mixed solution, the components of the alizarin solution and the antibacterial solution in the mixed solution are respectively 50% -100% and 50% -0, and the component of the antibacterial solution is not 0; the antibacterial solution is prepared by mixing lavender essential oil and gelatin nanoparticle solution in a volume ratio of 4 (45-47); the gelatin nanoparticle solution is prepared from the following components in a mass ratio of 1: (499-500) mixing the gelatin nanoparticles with ultrapure water;

the alizarin solution is prepared by mixing alizarin emulsion and ultrapure water according to the volume ratio of 1 (9-10); the alizarin emulsion is prepared by mixing alizarin and ethanol with the solid-to-liquid ratio of (2-6) to 1 g/L;

the pH colorimetric sensing film is prepared by adding 40g/L of film forming matrix and 10g/L of plasticizer into a mixed solution or alizarin solution, mixing and degassing at 45 +/-1 ℃ to obtain a film forming solution, spreading the film forming solution to a thickness of 4 +/-0.5 mm, and forming the film at a temperature of 23 +/-0.5 ℃, a humidity of 50 +/-3% and a film forming time of 24-48 hours.

2. The pH colorimetric sensor film of claim 1, wherein the film forming matrix is gelatin and the plasticizer is glycerol.

3. A method of making a pH colorimetric sensor film according to any one of claims 1 or 2, comprising the steps of:

4. The method for preparing a pH colorimetric sensor film according to claim 3, further comprising the steps of:

5. The method of making a pH colorimetric sensor film according to any one of claims 3 or 4, wherein the film forming matrix is gelatin and the plasticizer is glycerol.

6. Use of a pH colorimetric sensor film as defined in any one of claims 1 or 2, or produced by the method for producing a pH colorimetric sensor film as defined in any one of claims 3 to 5, as a packaging film for meat products.