CN116148249A

CN116148249A - Colorimetric film for monitoring freshness of penaeus vannamei boone and preparation method and application thereof

Info

Publication number: CN116148249A
Application number: CN202211511100.1A
Authority: CN
Inventors: 刘宇; 于雪娜; 杨伟; 李双碟; 姜维; 胡世伟; 余中节; 马庆保; 孙迪
Original assignee: Zhejiang Ocean University ZJOU
Current assignee: Zhejiang Ocean University ZJOU
Priority date: 2022-11-29
Filing date: 2022-11-29
Publication date: 2023-05-23

Abstract

The invention discloses a colorimetric film for monitoring freshness of penaeus vannamei boone and a preparation method and application thereof, wherein the preparation method comprises the following steps: 1) Obtaining a film forming liquid: preparing an aqueous solution containing myrica rubra dreg anthocyanin and curcumin, adding 4% glycerol (w/v), adding 0.8% (w/v) pullulan, stirring for 1h, and finally adding 1.2% (w/v) sodium alginate, and stirring for 3 h; 2) Preparation of a colorimetric film: film formation at 25 ℃,40% relative humidity; 3) Balanced colorimetric film: the mixture was equilibrated in an atmosphere of 50% relative humidity at 25℃for 24h. The colorimetric film is cut into a round shape with the diameter of 2cm and is attached to the top of the inner side of the preservation box for monitoring the freshness change of the penaeus vannamei during storage. The colorimetric film added with anthocyanin and curcumin has great application potential in the aspects of shrimp freshness monitoring and intelligent packaging.

Description

Colorimetric film for monitoring freshness of penaeus vannamei boone and preparation method and application thereof

Technical Field

The invention belongs to the field of food packaging, and particularly relates to a colorimetric film for monitoring freshness of penaeus vannamei boone, a preparation method and application thereof.

Background

The process of decreasing freshness of food products is often accompanied by a change in pH, for example, protein-rich seafood is susceptible to oxidative spoilage during transportation and storage, producing volatile amines, leading to an increase in pH in the package; however, fruits and vegetables are spoiled by spoilage caused by different microorganisms (lactic acid bacteria, yeast, mold, etc.), and metabolites such as ethanol, aromatic compounds, organic acids, ketones, acetaldehyde, etc. are produced, resulting in a decrease in the pH of the packaging environment. The food freshness indicating film can change color according to the change of the pH value in the packaging environment, and has great significance for indicating the food freshness.

The color change principle of the intelligent packaging system is that volatile ammonia diffuses into the film matrix and combines with moisture in the film to form NH ₃ ·H ₂ O, which is further hydrolyzed to NH4 ⁺ And OH (OH) ^- Resulting in an alkaline packaging environment, thereby altering the structure of the anthocyanin, causing a color change. Indicators are an important component of a colorimetric film, and commonly used indicators generally include synthetic chemical indicators and natural indicators. Synthetic indicators include methyl red, methyl blue, bromocresol green, and the like. Chemical indicators have advantages such as low cost and good indication effect, but in view of safety, more researches are currently conducted on using natural pigments instead of chemical indicators. Natural indicators include anthocyanins, curcumin, betaines, chlorophyll, and the like. The anthocyanin has very strong pH sensitivity, can show different colors under different pH values, but is sensitive to external environments such as photo-thermal and the like, and the stability is required to be further improved; curcumin is used as one of the indicators and has strong stability, but has poor sensitivity to external environments such as photo-thermal environment and the like, and the curcumin has strong stabilityA colorimetric film having high photo-thermal sensitivity is necessary.

Disclosure of Invention

Aiming at the problems existing in the prior art, the invention aims to provide a colorimetric film for monitoring the freshness of the penaeus vannamei boone, a preparation method and application thereof. The anthocyanin and the curcumin are used as the mixed indicator, so that the indicating performance, the stability and the color distinguishing degree of the colorimetric film are improved.

The method is realized by the following technical scheme:

the first object of the invention is to provide a preparation method of a colorimetric film for monitoring freshness of a penaeus vannamei boone, which comprises the following steps:

1) Preparing a colorimetric film forming liquid: weighing a certain amount of curcumin, dissolving in a small amount of NaOH solution with pH=10, diluting with distilled water after complete dissolution to obtain diluted curcumin solution, regulating the pH value to 7.0 with HCl solution, sequentially adding a certain amount of myrica rubra residue anthocyanin, glycerol and pullulan polysaccharide for dissolving for 1h, and finally adding a certain amount of sodium alginate and stirring for 3h to obtain film forming solution containing myrica rubra residue anthocyanin and curcumin;

2) Preparation of a colorimetric film: pouring the film forming liquid prepared in the step 1) into a plastic dish, and forming a film under the condition of 25 ℃ and 40% relative humidity to prepare a colorimetric film;

3) Balanced colorimetric film: the colorimetric film prepared in the step 2) is balanced for 24 hours at 25 ℃ in an environment with 50% relative humidity.

Further, in the step 1), the addition amount of curcumin was 0.272g, the addition amount of glycerin was 0.4g, the addition amount of pullulan was 0.8g, and the addition amount of sodium alginate was 1.2g per 100mL of diluted NaOH solution.

Further, in the step 1), the proportion of anthocyanin content and curcumin content in the waxberry dregs is 1:1.

Further, the curcumin is obtained by purchase and has a purity of 95-100%.

The second purpose of the invention is to provide the colorimetric film with the freshness of the penaeus vannamei boone prepared by the preparation method.

The third object of the invention is to provide application of the litopenaeus vannamei freshness colorimetric film as litopenaeus vannamei freshness monitoring.

Compared with the prior art, the invention has the following advantages: the colorimetric film disclosed by the invention is natural, safe and nontoxic, is sensitive to pH value, has great application potential in aspects of freshness monitoring and intelligent packaging of penaeus vannamei, and has higher sensitivity, stability and more obvious color distinguishing degree compared with an indicator film added with one pigment. As the freshness of the shrimp decreases, a corresponding color change in the colorimetric film will occur, indicating the freshness of the shrimp in the package.

Drawings

FIG. 1 is a cross-sectional scanning electron microscope view of a colorimetric film; (a) cross-sectional profiles of PSA, PSCA, and PSC at 1 KX; (B) cross-sectional profiles of PSA, PSCA, and PSC at 4 KX;

FIG. 2 is a photograph of water contact angle values;

FIG. 3 is a graph of the sensitivity of a colorimetric film to ammonia;

FIG. 4 is a color difference plot of the stability of the colorimetric film;

FIG. 5 is a graph showing the monitoring of 6 days of changes in Penaeus vannamei Boone at 4deg.C by a colorimetric film; (a) physical pictures, (B) pictures of PSA, PSC and PSAC, (C) color change parameters;

FIG. 6 is a graph showing the monitoring of color parameter changes of Penaeus vannamei Boone and changes in pH and TVB-N values of Penaeus vannamei Boone during storage at 4deg.C.

Detailed Description

The present invention is described in further detail below in conjunction with specific embodiments to provide a better understanding of the present technical solution.

Examples

S1, preparing a colorimetric film forming solution, namely weighing a certain amount of curcumin, dissolving the curcumin into a small amount of NaOH solution with pH of 10, diluting the solution with distilled water after complete dissolution, regulating the pH value to 7.0 by using an HCl solution, regulating the final content to 0.272% (w/v), regulating the pH value to 7.0 by using the HCl solution, then adding a certain amount of myrica rubra residue anthocyanin, wherein the proportion of anthocyanin content to curcumin content is 1:1, then adding 0.4% of glycerol (w/v), then adding 0.8% (w/v) of pullulan polysaccharide, dissolving for 1h, and finally adding 1.2% (w/v) of sodium alginate, and stirring for 3h to obtain a film forming solution containing myrica rubra residue anthocyanin and curcumin;

s2, preparation of a colorimetric film: pouring the film forming liquid prepared in the step S1 into a plastic dish, and forming a film under the condition of 25 ℃ and 40% relative humidity to prepare a colorimetric film;

s3 equilibrium colorimetric film: the colorimetric film prepared in S2 is equilibrated for 24 hours at 25 ℃ in an environment of 50% relative humidity.

Comparative example 1

Weighing a certain amount of waxberry residue anthocyanin, dissolving in distilled water, wherein the final content is 0.272% (w/v), adding 0.4% of glycerol (w/v), stirring uniformly, adding 0.8% (w/v) of pullulan polysaccharide, dissolving for 1h, adding 1.2% (w/v) of sodium alginate, stirring for 3h to obtain film-forming liquid containing anthocyanin, forming film at 25 ℃ under 40% of relative humidity, and balancing for 24h in an environment with 50% of relative humidity at 25 ℃.

Comparative example 2

Weighing a certain amount of curcumin, dissolving in a small amount of NaOH solution with pH=10, diluting with distilled water after complete dissolution, regulating the pH value to 7.0 by using HCl solution, then adding 0.4% of glycerin (w/v), firstly adding 0.8% (w/v) of pullulan for dissolving for 1h, then adding 1.2% (w/v) of sodium alginate, stirring for 3h, obtaining film-forming solution containing curcumin, forming a film under the condition of 25 ℃ and 40% relative humidity, and balancing for 24h in the environment of 25 ℃ and 50% relative humidity.

Application of colorimetric film: the colorimetric films prepared in the examples and comparative examples 1 and 2 were cut into a round shape with a diameter of 2cm and attached to the top of the inside of a 13cm×17cm×5cm fresh-keeping box for monitoring the freshness change of penaeus vannamei during storage.

Verification example

The performance test methods for obtaining the colorimetric films from the three different indicator solutions in the examples and comparative examples are as follows:

cross-sectional morphology of the film: the cross-sectional morphology of the films was observed using a scanning electron microscope at 4000 times magnification. The film was quenched in liquid nitrogen and vacuum sputtered metal spraying was performed prior to testing.

Stability test of film: films were measured for L (brightness), a (redness-greenness) and b (bluish-yellowness) using a hand-held CR-400 colorimeter. The total color difference (Δe) is calculated as follows:

wherein L, a and b are color parameters of the film; l (L) ₀ *、a ₀ *、b ₀ * Is a color parameter of a standard whiteboard.

The indicator film was placed on a standard whiteboard, the color of the indicator film was recorded with a digital camera, and the color parameters (L, a, and b) were measured with a handheld CR-400 color difference meter. The total color difference (Δe) is calculated according to the above formula.

Film thickness and mechanical properties: the thickness of the film was measured with a gauge (precision 0.001 mm), and 10 points on the film were randomly taken for measurement. The mechanical properties of the film were measured for tensile strength and elongation at break by an electronic tensile tester, the film was cut into a rectangular shape (20 mm. Times.70 mm), and the film was fixed between two clamps of a tensile machine, the clamping distance was set to 40mm, and the tensile speed was set to 50mm/min. Each membrane was assayed in 6 replicates.

Moisture content of the film: the pre-and post-drying mass of the film was determined by drying the film in an oven at 105 ℃ to constant weight, and the moisture content was calculated as follows:

wherein M and M are the pre-drying mass and post-drying mass of the film, respectively.

Water contact angle of film: the water contact angle of the film surface was measured using an optical contact angle meter. The film was cut into rectangles (20 mm. Times.50 mm) and tightly attached to a glass slide. A drop of 10 μl of ultrapure water was placed on the membrane surface, a photograph of the instantaneous drop was recorded by a high-speed camera, and laplace Yang Fangcheng was selected to fit the drop profile data. Each membrane was assayed in 6 replicates.

Water vapor transmission coefficient of the film: water vapor transmission coefficient (Water vapor permeability, WVP) of the membrane. Placing a weighing bottle in an oven, drying to constant weight at 105 ℃, placing 10g of allochroic silica gel, selecting a film with uniform surface and no holes, measuring the thickness of the film, covering the film on a weighing bottle mouth, sealing with liquid paraffin and rubber band, and weighing. The weighed weighing flask was placed in a desiccator containing distilled water (100% relative humidity). The weighed amount was taken out every 24 hours at room temperature, and the reaction was continued for 6 days. The water vapor transmission coefficient calculation formula is as follows:

wherein WVP-water vapor permeability coefficient, deltam-weight gain of the weighing bottle in the same time, g; d-thickness of film, mm; penetration area of A-membrane, m ² The method comprises the steps of carrying out a first treatment on the surface of the Δt-measuring time interval, s; ΔP-the water vapor pressure differential across the membrane, pa.

Swelling index: the colorimetric film was cut into a circular shape of 2cm in diameter, weighed under air-drying conditions, then immersed in deionized water for 120s, wiped off the excess moisture with filter paper, and weighed. The swelling index was calculated as follows:

m and M are the mass of the colorimetric film before and after water absorption, respectively.

Color change sensitivity of the film to volatile ammonia: measurement of the sensitivity of the membrane to volatile ammonia. The membrane (30 mm. Times.40 mm) was exposed to 0.8M aqueous ammonia solution for 24min at a distance of 1cm from the membrane. The color was recorded every 2min with a digital camera and the film color parameters (R, G and B) were measured with a hand-held CR-400 colorimeter to calculate the film sensitivity to volatile ammonia.

Wherein R is _i 、G _i 、B _i And R is _f 、G _f 、B _f The initial value and the measured value of the film, respectively.

And monitoring the freshness of the penaeus vannamei boone by using a colorimetric film. The colorimetric film is fixed on the top of a plastic dish filled with three fresh south-white prawns, sealed by a sealing film, and stored for 6d at 4 ℃. And measuring the volatile basic nitrogen content and the pH value of the penaeus vannamei boone every day, and establishing the correlation between the color change of the colorimetric film and the volatile basic nitrogen content of the penaeus vannamei boone. At the same time, the color of the colorimetric film is photographed with a camera.

Experiments were performed on the colorimetric film, wherein PSA represents the colorimetric film added with anthocyanin only from the waxberry residue, PSAC represents the colorimetric film added with anthocyanin and curcumin, and PSC represents the colorimetric film added with curcumin.

The results of SEM (scanning electron microscope) combined with figures 1 and 2 show that the anthocyanin and the curcumin in the waxberry dregs have good compatibility with the film-forming matrix. The section is even and smooth, and the section of the film is gradually rough along with the addition of curcumin. The water contact angle value becomes larger, and the increase is due to the addition of curcumin, which increases the roughness of the film, and the hydrophobic group of curcumin causes the water contact angle value to become larger.

With reference to fig. 3, the film with added curcumin and anthocyanin has the highest sensitivity, the film with added anthocyanin has higher sensitivity, and the film with added curcumin alone has lower sensitivity, because anthocyanin is more sensitive to pH. Referring to fig. 4, the colorimetric film has a high stability during storage, wherein the stability of the film containing curcumin is higher than that of the film containing only anthocyanin, indicating that the addition of curcumin is beneficial for enhancing the stability of the colorimetric film.

Physical and mechanical property measurements were performed on each group of colorimetric films, and the measurement results of the physical property measurements are shown in table 1.

TABLE 1

The addition of curcumin has no significant effect on the water vapor transmission rate of the film (p > 0.05), the tensile strength, swelling performance become strong, the moisture content and elongation at break are reduced, which is mainly related to the hydrophobic property of curcumin and the interaction between the components.

With reference to fig. 5 and 6, by comparing the results and with reference to the color parameters, the spoilage of the penaeus vannamei boone has a good indication effect, and the visible color change is consistent with the spoilage degree of the penaeus vannamei boone.

The color parameters of the colorimetric film and the multiple linear regression analysis of TVB-N values of the penaeus vannamei are shown in Table 2.

TABLE 2

The color parameter change of the colorimetric film has obvious correlation with the TVB-N value of the penaeus vannamei and R is obtained through multiple linear regression analysis ² The color change is larger than 0.9, so that the freshness of the penaeus vannamei boone can be better explained.

The colorimetric film based on the addition of anthocyanin and curcumin has great application potential in the aspects of shrimp freshness monitoring and intelligent packaging. Provides a reference for the application of the natural anthocyanin indicator film in food shelf life monitoring.

Claims

1. The preparation method of the colorimetric film for monitoring the freshness of the penaeus vannamei boone is characterized by comprising the following steps of:

2. The method for preparing a colorimetric film for monitoring freshness of penaeus vannamei according to claim 1, wherein in the step 1), the adding amount of curcumin is 0.272 and g, the adding amount of glycerin is 0.4g, the adding amount of pullulan is 0.8g, and the adding amount of sodium alginate is 1.2g in each 100mL of diluted NaOH solution.

3. The method for preparing a colorimetric film for monitoring freshness of penaeus vannamei boone as claimed in claim 1, wherein the proportion of anthocyanin content to curcumin content in the waxberry residue in the step 1) is 1:1.

4. The method for preparing a colorimetric film for monitoring freshness of penaeus vannamei boone as claimed in claim 1, wherein the purity of the curcumin is 95-100%.

5. A colorimetric film of the freshness of penaeus vannamei produced by the production method of any one of claims 1 to 4.

6. The use of the colorimetric film for freshness monitoring of penaeus vannamei boone as claimed in claim 5.