CN111999286B - Preparation method and application of a visual indicator label for monitoring the edible quality of aquatic products - Google Patents

Abstract

The invention provides a preparation method of a visual indication label for monitoring the edible quality of aquatic products, which organically combines different quality indexes of the aquatic products, divides the aquatic products according to quality grades in different storage stages, matches quality descriptors in corresponding stages, uses natural plant anthocyanin as a color developing agent, and realizes the quality description display of the aquatic products in different quality stages according to the positive correlation between the color developing sensitivity and the anthocyanin content; the visual indication label is pasted in the package, the package bag in the label display range is a transparent layer, the label displays different contents along with the storage time, the quality change of aquatic products can be monitored in real time, and meanwhile, the consumer can conveniently know the quality of the products in different stages, and the product purchasing is facilitated; the natural pigment is selected as the gas-sensitive indicator material, is non-toxic and harmless, and can be widely applied to the packaging of various aquatic foods.

Description

Preparation method and application of a visual indicator label for monitoring the edible quality of aquatic products

technical field

The invention relates to the field of food preservation, in particular to a preparation method and application of a visual indicator label for monitoring the edible quality of aquatic products.

Background technique

As the world's largest producer and consumer of aquatic food, the preservation, packaging and storage of aquatic food is one of the development directions of food industrialization. Although there are many evaluation methods for the edible quality of aquatic products, and these physical and chemical experimental methods and sensory evaluation methods can better judge the edible quality of aquatic products, these methods also have the advantages of complicated operation, time-consuming and labor-intensive, and high technical requirements for experimenters. limitation. Moreover, there are blind spots for rapid quality monitoring of products in the sales process, and it is not straightforward enough. At the same time, for consumers, how to judge the edible quality of the purchased products has no way of starting, and can only rely on experience.

Odor is a natural property of food, which is closely related to the quality of food. With the storage of food, the physical and chemical properties of the food itself, enzymes, microorganisms and other factors will change the odor of the food, and the change of the key odor composition will directly affect the consumer's acceptance of the food, which can also reflect the food texture, Food quality such as taste and taste. The volatile gas components that make up the smell of food usually have the characteristics of acidity and alkalinity and their own volatile characteristics. Therefore, using these characteristics, the sensitivity of pigments and the principle of acid-base color development can be used to make gas-sensitive sensors, which can be combined with other food indicators. The direct connection with the smell enables rapid, non-destructive testing of food quality.

The research on odor visualization sensors has been relatively mature, and most of them perform qualitative and quantitative analysis by using the color changes before and after the reaction of specific gas-sensing materials with the gas to be measured, such as porphyrins and hydrophobic pH indicators. Although these gas-sensitive materials have high sensitivity, they are not suitable for direct non-destructive testing of food due to their chemical toxicity, let alone contact with food. Therefore, some studies use natural pigments to replace these gas-sensitive materials to make gas-sensitive sensors for the detection of food materials. However, most of these studies are limited to the application of pork products, and can only be used for the detection of pork freshness. At the same time, the freshness can only be expressed by the overall color change of the sensor. For consumers who are not familiar with the technology, the freshness can be judged by color. Still prone to confusion and confusion.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a packaging method with an indicator label for the periodic change of the edible quality of aquatic products. The overall acid-base strength of the formed volatile odorants will change in a trend. The characteristic odor changes of aquatic products at different storage stages are linked with quality analysis indicators such as texture and sensory evaluation, and they are divided into different quality grades. Different contents of natural plant anthocyanin extracts are recorded in the label form as grade indicators and placed in the package. With the passage of storage time, it is affected by the linear change of the overall pH of the volatile odor substances in aquatic food. Through the color development of different concentrations of anthocyanins under different acid-base strength gases, the corresponding quality description will be displayed through color changes.

In order to achieve the above purpose, the present invention provides a preparation method of a visual indicator label for monitoring the edible quality of aquatic products, comprising the steps of:

S1, product testing and classification:

Measure the physical and chemical indicators in the preservation process of aquatic products, including: sensory evaluation, texture, volatile base nitrogen (TVB-N), total number of colonies (TVC); determine the quality of aquatic products according to the results of physical and chemical indicators and sensory evaluation Grade, which corresponds to the quality grade of aquatic products, volatile substances and the color sensitivity of natural plant anthocyanin extracts with different contents, as the basis for label preparation;

S2. Make labels

Relationship between volatile substances and visual indicator labels:

The visual indicator label is composed of labels indicating different quality levels; the visual indicator label indicating the same quality level is composed of a descriptor and a background film; the visual indicator label is composed of anthocyanin, starch, methyl cellulose The background film is made of the following raw materials with mass concentration: anthocyanin 0.0002-0.025mg/g), starch 10-30mg/g, methylcellulose 10-30mg/g g, dextran 10-30mg/g, gelatin 10-30mg/g; except the content of the anthocyanin extract is different, the material composition and content of the background film and the descriptor are the same;

The anthocyanin content in the background film and the descriptor is different according to the quality of the aquatic product, and the addition amount is different; wherein, the relationship between the quality of the aquatic product and the mass concentration of anthocyanin in the background film is shown in Table 1, the quality of the aquatic product and the The relationship between the mass concentration of anthocyanin in the descriptor is shown in Table 2;

Table 1 The relationship between the quality of aquatic products and the mass concentration of anthocyanins in the background film

serial number TVB-N(mg/100g) TVC(cfu/g) Anthocyanin concentration (mg/g) 1 0～10 0～80 0.0100～0.0134 2 11～20 81～1000 0.0036～0.0099 3 21～45 1001～49999 0.0005～0.0035 4 ≥46 ≥50000 0.0002～0.0004

Table 2 The relationship between the quality of aquatic products and the mass concentration of anthocyanins in water

serial number TVB-N(mg/100g) TVC(cfu/g) Anthocyanin concentration (mg/g) 1 0～10 0～80 0.0135～0.0250 2 11～20 81～1000 0.0100～0.0134 3 21～45 1001～49999 0.0036～0.0099 4 ≥46 ≥50000 0.0005～0.0035

The production method is:

According to the composition of the background film and the descriptor, the labeling solution was prepared as follows:

Add starch, methylcellulose, dextran and gelatin into water, heat at 50-80°C until completely dissolved to form a gel solution, stir continuously, and slowly add cyanidin; mix thoroughly, use 0.1mol/ml NaOH and 0.1mol/ml H ₂ SO ₄ was used to adjust the pH to make the gel solution into a colorless state; remove the air bubbles in the gel solution to obtain a background film solution and a descriptor solution, respectively; wherein, the gel solution showed a red color selection _The pH of the gel solution is about 6.0 in the colorless state _; the pH is different in the colorless state according to the content and type of anthocyanin used;

Cast the background film solution on a glass plate and let it stand for drying. Before drying to form a film, according to the descriptor, use the laser spray printing technology to spray the descriptor solution of the same quality level as the background film on the background film; wherein, the description The word is a word describing the quality level of aquatic products, which can be set according to actual needs; the label size can be set according to the actual packaging size;

S3. Arrange the finished indicator labels of different grades in the order of grades, and wrap them with low-density polyethylene films to obtain finished labels.

In a preferred manner, the anthocyanins described in step S2 can be derived from natural plants such as Chinese rose, rose, forget-me-not, Zhaoshui plum, and green calyx plum. According to the description, the ultrasonic extraction method is selected, and the solid powder is prepared through the steps of ultra-fine grinding, ultrasonic extraction, cooling, filtration, concentration under reduced pressure, freeze-drying, etc.; the anthocyanins can also be purchased through commercial channels.

In a preferred manner, the aquatic product in step S1 is mackerel or eel.

In a preferred manner, the method for removing bubbles in the gel solution in step S2 is to place the gel solution in a vacuum box with a vacuum degree of 0.2 MPa, and slowly stir at 100 rpm for 30 min.

The visual indicator label prepared by the present invention can be used to indicate the quality change of aquatic products and their products, and the method for monitoring the quality change of aquatic products by using the visual indicator label comprises the steps of: applying the label description with the sprayed surface facing inward on a package In the package with aquatic products, the place where it is placed is the transparent part of the package. Wherein, the aquatic products include aquatic products and their products.

In a preferred manner, the packaging is bagged or boxed.

The beneficial effects of the present invention are:

The sensitivity of natural plant anthocyanins to the acid-base strength of volatile odors is related to the content of anthocyanins. Using this color development feature, the color development sequence can be controlled by selecting different anthocyanin contents. Therefore, the present invention utilizes natural anthocyanins to make aquatic product quality labels, converts the edible quality of aquatic products into odor characteristics, then converts odor characteristics into color characteristics, and then converts color characteristics into text characteristics. The method converts the quality characteristics of aquatic products, which are difficult to be judged by naked eyes, into visualization through visual indicator labels, which is beneficial to consumers' cognition of product quality and the supervision of product quality by regulatory authorities.

The method of the invention is simple in operation, low in cost, green and environmentally friendly, can be popularized in aquatic product enterprises and food processing enterprises, and has wide application prospects;

The indicator label adopted in the present invention is displayed in staged color characters, which intuitively expresses the edible quality of aquatic products in different storage stages, which is convenient for consumers to purchase and for sellers to manage and coordinate the sales products.

Description of drawings

Fig. 1 is the sensory evaluation score chart of the different stages of storage of grilled eel in Example 1 of the present invention;

Fig. 2 is the sensory evaluation score diagram of the different stages of storage of smoked mackerel in Example 2 of the present invention;

Fig. 3 is the sensory evaluation score diagram of the different stages of storage of chilled fresh eel in Example 3 of the present invention;

Fig. 4 is the tenderness change diagram of the different stages of storage of roasted eel in the embodiment of the present invention 1;

Fig. 5 is the tenderness change diagram of the different stages of storage of smoked mackerel in the embodiment of the present invention 2;

Fig. 6 is the tenderness variation diagram of the embodiment of the present invention 3 chilled fresh eel storage different stages;

Fig. 7 is the processing technology schematic diagram of the roasted eel in the embodiment of the present invention 1;

Fig. 8 is the processing technology schematic diagram of smoked mackerel in the embodiment of the present invention 2;

Fig. 9 is the best edible period label display schematic diagram of embodiment 1 of the present invention;

10 is a schematic diagram showing the label display in the quality decline period of Example 1 of the present invention;

11 is a schematic diagram showing the edible period label in Example 1 of the present invention;

Fig. 12 is a schematic diagram showing the label display of the spoiled product in Example 1 of the present invention.

Detailed ways

The present invention will be further described below through specific embodiments.

1. Product testing and classification: use electronic nose, texture analyzer, colorimeter and sensory evaluation to analyze the changes of each index during the storage process of aquatic products, and then classify the products into different levels according to the differences of the indexes; for example, the following quality Grades: ①Best edible period; ②Quality decline period; ③Edible period; ④Deteriorated product; corresponding odor descriptors, texture descriptors and sensory evaluation descriptors are assigned to each stage.

2. Grade label production: label production is divided into two parts, namely label background and indication descriptor; anthocyanin extracts of different concentrations are divided according to quality grades as color indicators. Select natural plant anthocyanin extracts such as Chinese rose, rose, forget-me-not, Zhaoshui plum, green calyx plum as color developing agent, wherein the content of each natural plant anthocyanin extract is as shown in Table 3;

The anthocyanin content of the cyanidin extract used in the background of the best edible period is 2.0-2.5 mg/g; the content of the cyanidin extract used in the background of the quality decline period is 1.5-2.0 mg/g; The content of the cyanidin extract used is 1.0-1.5 mg/g; the content of the cyanidin extract used in the background of the spoiled product is 0.5-1.0 mg/g.

The anthocyanin content of the cyanidin extract used in the descriptor of the best edible period is 2.5mg/g; the content of cyanidin extract used in the descriptor of the quality decline period is 2.0-2.5mg/g; the descriptor of the edible period The content of the cyanidin extract used is 1.5-2.0 mg/g; the content of the cyanidin extract used in the description of the spoiled product is 1.0-1.5 mg/g.

Labels of different grades are made separately. First add starch, methylcellulose, dextran, gelatin, etc. into water, heat at 50-80°C, and stir continuously after forming a gel, and slowly add cyanidin extract. Among them, cyanidin extract and starch, methylcellulose, dextran, gelatin, etc. use water as solvent, and the proportion of each component is: 1%-10% cyanidin extract, 1%-3% starch, 1%-3% % methyl cellulose, 1% to 3% dextran, 1% to 3% gelatin. After complete mixing, pH was adjusted with 0.1 mol/ml NaOH and 0.1 mol/ml H2SO4 to make the solution colorless. The air bubbles in the solution were removed, and the solution was cast on a glass plate and left to dry.

Before the solution is about to dry to form a film, use a high-level concentration of transparent anthocyanin solution to use laser spray printing technology to spray grade descriptors, odor descriptors, texture descriptors and sensory evaluation descriptors on the background film. After drying to form a film, it is cut into a uniform specification label.

3. Arrange the finished indicator labels of different grades of uniform specifications in order, and wrap them with low-density polyethylene film. The descriptors are sprayed inward and placed in the package. The place where the label is placed is the transparent part of the package. Can be in bags or boxes.

The anthocyanins used in the following examples are extracted from natural plants such as Chinese rose, rose, forget-me-not, Zhaoshui plum, green calyx plum, and ultrasonic waves are selected according to the description in "The Extraction Method of Anthocyanin and Application Research Progress" by Li Xiaodong, etc. Extraction method, prepare solid powder by steps such as ultra-fine grinding, ultrasonic extraction, cooling, filtration, concentration under reduced pressure, freeze-drying, wherein the content of anthocyanin in the natural plant anthocyanin extract obtained by different plants is as shown in Table 3 shown:

Table 3 Source of anthocyanin extract and anthocyanin content

Example 1: A grilled eel product with a label indicating the phase change of edible quality

A method for preparing a visual indicator label for monitoring the eating quality of grilled eel, comprising the steps of:

S1, product testing and classification:

Measure the physical and chemical indicators of grilled eel during storage, including: sensory evaluation, tenderness, volatile base nitrogen (TVB-N), total bacterial colony (TVC); determine the quality of the product according to the results of physical and chemical indicators and sensory evaluation Grade, the quality grade of the product and the color sensitivity of different contents of natural plant anthocyanins are corresponding, as the basis for label preparation; wherein, the tenderness is measured by texture, and the sensory evaluation method is shown in Table 4:

Table 4 Sensory evaluation index of grilled eel stage changes

S2, label making

Relationship between volatile substances and visual indicator labels:

The relationship between the visual indicator labels: the visual indicator labels are composed of labels indicating different quality levels; the visual indicator labels indicating the same quality level are composed of a descriptor and a background film. According to the detection result described in step S1 , set the following four labels, and the text descriptions of the descriptors are:

①Best edible period: The grilled eel has a strong aroma, a moderate taste, and the meat is tender and juicy;

②Quality decline period: The aroma of grilled eel is lighter, the meat is slightly hardened, and the tenderness of the meat is reduced;

③ Edible period: there is a fishy smell, the meat is hard, and the water loss is more obvious;

④ spoiled products: rancid and spoiled, inedible;

The visual indicator label is made of cyanidin, starch, methylcellulose, polysaccharide, gelatin and water; the mass concentration content of each component in water is cyanidin (as shown in Table 5), starch 20mg/g, Methylcellulose 10mg/g, dextran 20mg/g, gelatin 20mg/g;

According to the physical and chemical indicators and product quality of grilled eel stored in different periods measured in this example, the mass concentration of anthocyanin in the label is shown in Table 5. In the visual indicator label of the same quality level, the cyanine in the background film is shown in Table 5. The anthocyanin concentration is one level lower than the descriptor anthocyanin concentration.

Table 5 Concentration of anthocyanin in the visual indicator label of grilled eel

To make labels, labels of different grades are made separately; according to the raw material composition of the background film and descriptor, the label solutions are prepared according to the following methods:

Add starch, methylcellulose, dextran and gelatin into water, heat at 70°C to form a gel solution, stir continuously, and slowly add cyanidin; mix thoroughly, use 0.1mol/ml NaOH and 0.1mol/ml Adjust the pH with H ₂ SO ₄ to make the gel solution colorless; place the gel solution in a vacuum box with a vacuum degree of 0.2 MPa, stir slowly at 100 rpm for 30 min, remove the bubbles in the gel solution, and obtain the background thin film gel respectively solution and visual indicator font gel solution;

Casting the background film gel solution on a glass plate and standing to dry, before drying to form a film, spray the descriptor solution of the same quality level as the background film on the background film according to the descriptor and using the laser spray printing technology;

S3. Arrange the finished indicator labels of different quality grades in order, and wrap them with low-density polyethylene film to obtain a finished label.

Paste the descriptor with the sprayed surface facing inward in the package, and the place where it is attached is the transparent part of the package; wherein, the package may be in a bag or a box.

The label made in this embodiment can convert the quality characteristics of grilled eel products that are difficult to visually determine into visualization, which is beneficial to consumers' cognition of the quality of grilled eel products and the supervision of the quality of grilled eel products by regulatory authorities.

Wherein, the preparation method of the grilled eel is shown in FIG. 7 .

Example 2: A cold-smoked mackerel product with a label indicating the phase change of edible quality

A preparation method of a visual indicator label for monitoring the edible quality of cold-smoked mackerel, comprising the steps of:

S1, product testing and classification:

The physical and chemical indicators during the storage process of cold-smoked mackerel were measured, including: sensory evaluation, tenderness, volatile base nitrogen (TVB-N), and total number of bacterial colonies (TVC). Quality grade, which corresponds to the quality grade of the product and the color sensitivity of natural plant anthocyanins with different contents, as the basis for label preparation; among them, the sensory evaluation method is shown in Table 6;

Table 6 Sensory evaluation indexes of staged changes of smoked mackerel

S2, label making

Relationship between volatile substances and visual indicator labels:

The relationship between the visual indicator labels: the visual indicator labels are composed of labels indicating different quality levels; the visual indicator labels indicating the same quality level are composed of a descriptor and a background film. According to the detection result described in step S1 , set the labels of the following four quality levels, and the text descriptions of the descriptors are:

①Best edible period: strong smoky flavor, moderate taste, and tender meat;

② quality decline period: the smoked aroma is lighter, the meat is slightly hardened, and the tenderness of the meat is reduced;

③Eatable period: the fishy smell is obvious, and the meat is hard;

④ spoiled products: rancid and spoiled, inedible;

The visual indicator label is made of cyanidin, starch, methylcellulose, polysaccharide, gelatin and water; the mass concentration of each component in water is: cyanidin (as shown in Table 7), starch 30mg/g, Methyl 30mg/g cellulose, dextran 10mg/g, gelatin 10mg/g;

The cold-smoked mackerel measured according to the present embodiment places the physical and chemical indicators and product quality in different periods, and the relationship between the anthocyanin content in the label is as shown in Table 7:

Table 7 Relationship between different edible qualities of smoked mackerel and the amount of anthocyanin added in the visual indicator label

Make grade labels, and make different grade labels separately; according to the composition of the background film and descriptor, prepare the label solution according to the following methods:

Add starch, methylcellulose, dextran and gelatin into water, heat at 70°C to form a gel solution, stir continuously, and slowly add cyanidin; mix thoroughly, use 0.1mol/ml NaOH and 0.1mol/ml Adjust the pH with H ₂ SO ₄ to make the gel solution colorless; place the gel solution in a vacuum box with a vacuum degree of 0.2 MPa, stir slowly at 100 rpm for 30 min, remove air bubbles in the gel solution, and obtain background thin film gels respectively solution and descriptor gel solution;

Cast the background film gel solution on a glass plate and let it stand for drying. Before drying to form a film, according to the descriptor, use the laser spray printing technology to spray the descriptor gel solution of the same quality level as the background film on the background film;

S3. Arrange the finished indicating labels of different quality grades in order, and wrap them with low-density polyethylene film to obtain a finished label.

Paste the label descriptor with the sprayed surface facing inwards in the package, and the sticking place is the transparent part of the package; wherein, the package may be in a bag or a box.

Using the label made in this embodiment, the quality characteristics of smoked mackerel products that are difficult to be judged by naked eyes can be converted into visualization, which is beneficial to consumers' cognition of the quality of smoked mackerel products and the supervision department's perception of the quality of smoked mackerel products. monitoring.

Wherein, the preparation method of the smoked mackerel is shown in FIG. 8 .

Example 3: A chilled fresh eel product with a label indicating the stage change of edible quality

A preparation method of a visual indicator label for monitoring the eating quality of chilled fresh eel, comprising the steps of:

S1, product testing and classification:

The physical and chemical indicators of chilled fresh eel during storage were measured, including: sensory evaluation, texture, volatile base nitrogen (TVB-N), total number of colonies (TVC); Quality grade, the quality grade of the product corresponds to the color sensitivity of natural plant anthocyanins with different contents, as the basis for label preparation; wherein, the sensory evaluation method is shown in Table 8;

Table 8 Sensory evaluation index of fresh eel stage changes

S2, label making

Relationship between volatile substances and visual indicator labels:

The relationship between the visual indicator labels: the visual indicator labels are composed of labels indicating different quality levels; the visual indicator labels indicating the same quality level are composed of a descriptor and a background film. According to the detection result described in step S1 , set the labels of the following four quality levels, and the text descriptions of the descriptors are:

①Best edible period: fresh fish flavor, fresh and tender meat;

② Quality decline period: the fishy smell is aggravated, the meat is slightly hardened, and the tenderness of the meat is reduced;

③ Edible period: there is a strong fishy smell, the meat is hard, and the water loss is obvious;

④ spoiled products: rancid and spoiled, inedible;

The visual indicator label is made of cyanidin, starch, methylcellulose, polysaccharide, gelatin and water; the mass concentration content of each component in water is cyanidin (as shown in Table 9), starch 10mg/g , methylcellulose 20mg/g, dextran 30mg/g, gelatin 30mg/g.

The cold fresh eel that records according to the present embodiment is placed the physical and chemical index and product quality of different periods, and the relation between the anthocyanin content in the label is as shown in Table 9:

Table 9 The relationship between different edible qualities of fresh eel and the amount of anthocyanin added in the visual indicator label

Make grade labels, and make different grade labels separately; according to the composition of the background film and descriptor, prepare the label solution according to the following methods:

Add starch, methylcellulose, dextran and gelatin into water, heat at 70°C to form a gel solution, stir continuously, and slowly add cyanidin; mix thoroughly, use 0.1mol/ml NaOH and 0.1mol/ml Adjust the pH with H ₂ SO ₄ to make the gel solution colorless; place the gel solution in a vacuum box with a vacuum degree of 0.2 MPa, stir slowly at 100 rpm for 30 min, remove air bubbles in the gel solution, and obtain background thin film gels respectively solution and descriptor gel solution;

Cast the background film gel solution on a glass plate and let it stand for drying. Before drying to form a film, spray the descriptor solution with the same quality level as the background film on the background film according to the descriptor and using the laser spray printing technology;

S3. Arrange the finished indication labels of different quality grades in order, and wrap them with low-density polyethylene film. The descriptors are sprayed inward and placed in the package, and the place where they are placed is the transparent part of the package; The packaging can be bagged or boxed.

The label made in this embodiment can convert the quality characteristics of chilled eel products that are difficult to visually determine into visualization, which is beneficial to consumers' cognition of the quality of chilled eel products and the supervision of the quality of chilled eel products by regulatory authorities.

The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (7)

1. A preparation method of a visual indication label for monitoring the eating quality of aquatic products is characterized by comprising the following steps:

s1, product detection and grading:

the method for measuring the physical and chemical indexes in the preservation process of the aquatic products comprises the following steps: sensory evaluation, tenderness, volatile basic nitrogen, total number of colonies; judging the quality grade of the product according to the physicochemical indexes and the sensory evaluation result;

s2, label making:

the visual indication label is composed of labels indicating different quality levels; the label indicating the same quality grade is composed of a descriptor and a background film;

the background film is prepared from the following raw materials: the composition comprises anthocyanin, starch, methyl cellulose, glucan, gelatin and water, wherein the mass concentration of the raw materials in the water is as follows: 10-30 mg/g of starch, 10-30 mg/g of methylcellulose, 10-30 mg/g of glucan, 10-30 mg/g of gelatin and 0.0002-0.0134 mg/g of anthocyanin;

the descriptor is prepared from the following raw materials: the composition comprises anthocyanin, starch, methyl cellulose, glucan, gelatin and water, wherein the mass concentration of the raw materials in the water is as follows: 10-30 mg/g of starch, 10-30 mg/g of methylcellulose, 10-30 mg/g of glucan, 10-30 mg/g of gelatin and 0.0005-0.025 mg/g of anthocyanin;

wherein, the descriptors and the background film have the same components and content except the anthocyanin content;

the relationship between the quality of the aquatic product and the mass concentration of anthocyanin in the background film is shown in table 1, and the relationship between the quality of the aquatic product and the mass concentration of anthocyanin in the descriptors is shown in table 2;

TABLE 1 relationship between quality of aquatic products and mass concentration of anthocyanins in background film in water

Serial number TVB-N mg/100g TVC cfu/g The concentration of anthocyanidin is mg/g 1 0～10 0～80 0.0100～0.0134 2 11～20 81～1000 0.0036～0.0099 3 21～45 1001～49999 0.0005～0.0035 4 ≥46 ≥50000 0.0002～0.0004

TABLE 2 relationship between quality of aquatic products and mass concentration of anthocyanidin in descriptor in water

Serial number TVB-N mg/100g TVC cfu/g The concentration of anthocyanidin is mg/g 1 0～10 0～80 0.0135～0.0250 2 11～20 81～1000 0.0100～0.0134 3 21～45 1001～49999 0.0036～0.0099 4 ≥46 ≥50000 0.0005～0.0035

According to the composition of the background film and the descriptors, the label solution is prepared by the following method respectively:

adding starch, methylcellulose, glucan and gelatin into water, heating at 50-80 ℃ until the starch, the methylcellulose, the glucan and the gelatin are dissolved to form a gel solution, continuously stirring, adding anthocyanin, uniformly mixing, and adjusting the pH value to enable the gel solution to be colorless; removing bubbles in the gel solution to respectively obtain a background film solution and a descriptor solution;

casting the background film solution onto a glass plate, standing and drying, and spraying the descriptor solution with the same quality grade onto the background film by using a laser spraying and printing technology before drying and film forming;

and S3, arranging the manufactured indicating labels with different quality grades in sequence, and attaching and wrapping the indicating labels by using a low-density polyethylene film to obtain finished label products.

2. The method for preparing the visual indication label for monitoring the eating quality of the aquatic product according to claim 1, wherein the aquatic product is eel or spanish mackerel in step S1.

3. The method for preparing a visual indication label for monitoring the eating quality of aquatic products according to claim 1, wherein the anthocyanidin is extracted from China rose, forget-me-not, plum or flos Pruni mume at step S2.

4. The method for preparing a visual label for monitoring the eating quality of aquatic products according to claim 1, wherein the step S2 is to remove bubbles from the gel solution by: the gel solution was placed under a vacuum of 0.2MPa and stirred at 100rpm for 30 min.

5. Use of a visual indicator label prepared according to any one of claims 1 to 4 for monitoring changes in the quality of aquatic products and products thereof.

6. A method of monitoring changes in the quality of an aquatic product using a visual indicator prepared according to any one of claims 1 to 4, comprising the steps of: the visual indication label descriptor is pasted in a package containing aquatic products with the spraying surface facing inwards, and the package is sealed; the sticking place is a transparent place of the package.

7. The method of monitoring changes in the quality of aquatic products using visual indicators of claim 6, wherein the packaging is a bag or a box.

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