Edible fish gelatin liquid film with antibacterial activity and preparation method thereof

Abstract

The present invention belongs to the technical field of food preservation, and specifically relates to an edible fish gelatin liquid film with antibacterial activity and a preparation method thereof. The edible fish gelatin liquid film with antibacterial activity provided by the present invention is mainly prepared from ingredients such as fish gelatin, gum arabic, glycerol, edible oil, Tween 80, nisin and transglutaminase, and the prepared edible fish gelatin liquid film with antibacterial activity has the advantages of significant antibacterial effect, good preservation effect and long maintenance period. Moreover, the present invention adopts nisin as an antibacterial agent. Compared with other similar edible films with essential oils and polyphenols added, the liquid film has a smell closer to fish meat and will not bring other peculiar smells to the fish meat. At the same time, it is stable at low temperature and can be refrigerated or frozen together with the fish meat. It is a relatively ideal edible liquid fresh-keeping film for aquatic products fish gelatin.

Description

Technical Field

[0001] The invention belongs to the technical field of food preservation, and in particular relates to an edible fish gelatin liquid film with antibacterial activity and a preparation method thereof. Background Art

[0002] Traditional food packaging materials are derived from petroleum polymers, which are non-renewable resources. At the same time, these polymers are difficult to degrade and can easily damage the natural environment. On the other hand, traditional food packaging materials have poor thermal stability and are easily decomposed at high temperatures to produce harmful substances. In addition, plastic wraps, for example, produce plastic particles when in long-term contact with food. These harmful substances enter the human body through food and cause harm to human health. Therefore, the country has promoted the "plastic ban" and urgently needs to find new degradable and eco-friendly materials to replace traditional food packaging materials.

[0003] Aquatic products are easily contaminated by microorganisms during storage, transportation, processing and sales due to their high protein content, high water content and rich in unsaturated fatty acids, causing spoilage. Therefore, the preservation step of aquatic products is particularly important for the processing and transportation of aquatic products. Single proteins, polysaccharides and other edible natural biomacromolecules can form a network structure through intramolecular or intermolecular cross-linking, and form a membrane structure with certain mechanical properties after drying. However, studies have found that complex colloids such as proteins and polysaccharides are more conducive to improving the comprehensive performance of the membrane, and the network structure formed by biomacromolecules is very suitable for the embedding of some functional active agents such as polyphenols, essential oils, antibiotics, etc., so as to achieve the protection and controlled release of functional active substances.

[0004] Rosemary is rich in carnosic acid, carnosol, rosmarinic acid and other polyphenols, and has multiple physiologically active functions. It is a natural, safe and highly effective antioxidant and antibacterial agent. Yao Lei published a paper entitled "The Effect of Fish Scale Gelatin Edible Film Added with Rosemary Extract and Phytic Acid on the Preservation Effect of Crucian Carp", which showed that the fish scale gelatin edible film added with rosemary extract and phytic acid had a significant preservation effect on crucian carp within 6 days and during storage at 4°C. However, rosemary extract can improve the solubility of fish scale gelatin, resulting in the inability to absorb the water of crucian carp well, and obvious liquid appears during storage. In addition, the peptides produced by enzymatic hydrolysis of fish scales provide nutrients for the growth of bacteria, which leads to the accelerated deterioration of fish scale gelatin edible film added with rosemary extract after 6 days, and the preservation effect is worse than that of crucian carp that has not been preserved.

[0005] Patent document CN110506783A discloses a ginger essential oil fresh-keeping solution for salmon and a fresh-keeping method for salmon, the fresh-keeping solution is mainly composed of ginger essential oil, sodium caseinate, plasticizer, emulsifier and water, the prepared ginger essential oil fresh-keeping solution has an obvious fresh-keeping effect on salmon storage, can significantly delay the change of salmon taste and flavor, delay the change of salmon hardness and color, inhibit the growth of lipid peroxide value, volatile basic nitrogen value and total bacterial count, thereby extending the shelf life, and the method is simple, easy to obtain materials, low cost, easy to promote. However, the added ginger essential oil antibacterial agent has poor stability, easy to volatilize defects, can not guarantee the fresh-keeping effect, and the fresh-keeping time is also short, which is not conducive to large-scale promotion and application. Summary of the invention

[0006] In order to solve the defects of aquatic product cling film in the prior art, the present invention provides an edible fish gelatin liquid film with antibacterial activity and a preparation method thereof, wherein the edible fish gelatin liquid film with antibacterial activity is mainly prepared from fish gelatin and gum arabic as film-forming components, nisin as an antibacterial agent, transglutaminase as a cross-linking agent and other raw materials. The edible fish gelatin liquid film prepared by the present invention has the advantages of significant antibacterial effect, high safety, good and long-term preservation effect on aquatic products, and is a natural, degradable, and significant preservation effect edible fish gelatin liquid film.

[0007] The present invention provides an edible fish gelatin liquid film with antibacterial activity, comprising the following components and their weight proportions:

[0008] 38-42 parts of fish gelatin, 3-12 parts of gum arabic, 3-8 parts of glycerol, 110-130 parts of edible oil, 3-8 parts of Tween 80, 3-8 parts of nisin and 0.2-2 parts of transglutaminase.

[0009] Furthermore, the edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0010] 40 parts of fish gelatin, 5-10 parts of gum arabic, 4-5 parts of glycerol, 120-125 parts of edible oil, 4-5 parts of Tween 80, 4-7 parts of nisin and 0.5-1 part of transglutaminase.

[0011] Furthermore, the fish gelatin is type A fish gelatin, and the edible oil is one or a combination of two or more of soybean oil, peanut oil, rapeseed oil, perilla oil and olive oil.

[0012] The preparation method of type A fish gelatin is as follows: after crushing tilapia scales, rinse with clean water to obtain fish scale raw material, add the fish scale raw material into 0.5 mol / L citric acid solution, and continuously stir to decalcify for 1 hour, the solid-liquid ratio of the fish scale raw material to the citric acid solution is 1 g:10 mL, rinse with clean water after decalcification to obtain decalcified fish scales, then add 1 mol / L NaOH solution to adjust the pH to 6.0, then add water, heat in a water bath at a temperature of 70 to 80° C. for 2 to 3 hours, the solid-liquid ratio of the decalcified fish scale to water is 1 g:3 mL, filter out fish scale residues, and freeze-dry the filtrate to obtain type A fish gelatin.

[0013] Furthermore, the edible fish gelatin liquid film with antibacterial activity also includes 1 to 3 parts of chitosan quaternary ammonium salt.

[0014] In addition, the present invention also provides a method for preparing the edible fish gelatin liquid film with antibacterial activity, comprising the following steps:

[0015] S1. Add fish gelatin to water, heat in a water bath to 40-60°C, heat for 1-2 hours, and stir until fully dissolved to obtain a fish gelatin solution;

[0016] S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 30 to 40°C, and then glycerol, cooking oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, a monolayer emulsion is obtained;

[0017] S3. Adding gum arabic to water, heating in a water bath to 40-60° C., heating for 1-2 h, stirring until fully dissolved, to obtain a gum arabic solution, then adding the gum arabic solution to the single-layer emulsion obtained in step S2, subjecting the mixture to shear homogenization and ultrasonic treatment, and then high-pressure homogenization to obtain a double-layer emulsion;

[0018] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 40-45°C, glutamine transaminase is added, and the reaction is stirred for 1-2 hours. After the reaction is completed, the enzyme is inactivated in a water bath at 90-100°C for 5-8 minutes, high-pressure homogenization is performed, and the product is sealed and packaged.

[0019] Furthermore, the shear homogenization conditions in step S2 and step S3 are: shear rate of 6000-12000 rpm, shear time of 3-10 min; the ultrasonic treatment conditions are: ultrasonic power of 200-500 W, ultrasonic working time of 3-15 min.

[0020] Furthermore, the conditions for the high-pressure homogenization treatment in step S3 are: a pressure of 80 to 120 MPa, and a treatment time of 3 to 8 minutes.

[0021] Furthermore, the conditions for the high-pressure homogenization treatment in step S4 are: a pressure of 80 to 120 MPa, and a treatment time of 2 to 5 minutes.

[0022] Furthermore, the step S4 also includes adding chitosan quaternary ammonium salt, and the specific adding steps are: after the enzyme is inactivated, chitosan quaternary ammonium salt is added, stirred evenly, left to stand for 2 to 3 minutes, subjected to high pressure homogenization treatment, and sealed and filled.

[0023] Furthermore, the pH of the prepared edible fish gelatin liquid film with antibacterial activity is 5.5-6.0.

[0024] The invention mainly uses natural macromolecular type A fish gelatin and gum arabic as film-forming raw materials, nisin as an antibacterial agent, and transglutaminase as a cross-linking agent. Specifically, the fish gelatin is heated in water to completely melt, and then a certain amount of glycerol, edible oil, Tween 80 and nisin are added to prepare a single-layer emulsion. Then, the gum arabic solution is also heated in water to completely melt and then added to the single-layer emulsion to prepare a double-layer emulsion. Finally, transglutaminase is added to cross-link the colloidal network of the double-layer emulsion, and then high-pressure homogenization is performed and the mixture is filled. The prepared edible fish gelatin liquid film with antibacterial activity has the advantages of good stability and significant antibacterial effect.

[0025] After the type A fish gelatin provided by the present invention is dissolved in water, its charge is mainly positive, and it can be self-assembled with the negatively charged gum arabic through electrostatic action to form a stable double-layer emulsion structure, which can extend the service life of the liquid film. Nisin is a natural bioactive antimicrobial peptide. Adding a specific amount of nisin to the liquid film system of the present invention can better promote the antibacterial activity of nisin. At the same time, after being cross-linked and embedded in the liquid film colloid, the antibacterial activity of nisin can be greatly extended, thereby forming an edible fish gelatin liquid film with high stability and significant antibacterial effect.

[0026] In addition, the inventors found that the added nisin antibiotic would affect the elongation at break, tensile strength and water solubility of the liquid film, thereby affecting the preservation effect of the liquid film. Moreover, the inventors also found in their in-depth study of salmon that the spoilage bacteria of salmon in the early stage of cold storage were mainly Staphylococcus, Pseudomonas, Pediococcus, Micrococcus, etc. As the storage time increased, the spoilage bacteria gradually became single, and the content of major species such as Staphylococcus, Pediococcus, Micrococcus, etc. continued to decrease, and the remaining small part of the strains would completely disappear, while the content of Pseudomonas continued to increase and became the absolute dominant species. Pseudomonas is a type of Gram-negative bacteria. A large amount of lipopolysaccharide attached to the surface of its cell wall can limit the penetration of nisin containing more hydrophobic amino acids, greatly reducing the antibacterial effect of nisin. As a result, the plastic wrap with single nisin as an antibacterial agent has significant antibacterial effect in the early stage. However, as the storage time of salmon increases, the number of Gram-negative bacteria continues to increase, and its antibacterial effect will continue to decline.

[0027] In order to further solve the above-mentioned problem, the inventor continuously studies, and in an attempt to explore the test, the inventor attempts to add chitosan quaternary ammonium salt in liquid film to increase the antimicrobial effect of the liquid film in the later stage. Through the test, it is unexpectedly found that this chitosan quaternary ammonium salt can form a synergistic antimicrobial effect with nisin, which can not only greatly improve the antimicrobial effect of the liquid film, but also can ensure and maintain the long-time antimicrobial effect of the liquid film. Simultaneously, the inventor also unexpectedly finds that this chitosan quaternary ammonium salt can also effectively make up for the problem that the fresh-keeping period is shortened due to the decline in properties after the liquid film forming, and further improves the fresh-keeping quality of the liquid film.

[0028] After in-depth research, the inventor guesses that its principle is: the chitosan quaternary ammonium salt added forms a uniform film after being soluble in water and covers the surface of the double-layer emulsion, and the chitosan film has a good bactericidal effect, and it can cooperate with the nisin of the package to play the effect of enhancing antibacterial, improve the fresh-keeping effect of salmon. And this chitosan makes self-filming, does not crosslink with fish gelatin and gum arabic, and the quaternary ammonium salt with positive charge does irregular movement and constantly contacts with Pseudomonas after absorbing water, increases the interaction with the negative charge of the bacterial outer membrane, causes the destruction of the cell outer membrane, stops the growth and proliferation of bacteria, thereby ensures the bactericidal effect of the liquid film in the later stage. The film formed by this chitosan quaternary ammonium salt simultaneously has good tensile strength, good water retention and water absorption effect, solves the influence of nisin on the liquid film, and can further extend the fresh-keeping period of the fresh-keeping film to aquatic products.

[0029] Compared with the prior art, the edible fish gelatin liquid film with antibacterial activity provided by the present invention has the following advantages:

[0030] (1) The edible fish gelatin liquid film with antibacterial activity provided by the present invention uses natural macromolecular fish gelatin and gum arabic as raw materials. The raw materials have a large natural reserve and are easy to obtain. They are edible, degradable and environmentally friendly. Type A gelatin is mainly positively charged after being dissolved in water, and can self-assemble with negatively charged gum arabic through electrostatic action to form a double-layer emulsion with good stability.

[0031] (2) The edible fish gelatin liquid film with antibacterial activity provided by the present invention has the advantages of significant antibacterial effect, good preservation effect and long maintenance period. The present invention adopts nisin antibacterial agent. Compared with other similar edible films with added essential oils and polyphenols, the liquid film has a smell closer to fish meat and will not bring other odors to the fish meat. At the same time, it is stable at low temperature and can be refrigerated or frozen together with the fish meat. It is a more ideal edible liquid preservative film of fish gelatin for aquatic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a scanning electron microscope image of an edible fish gelatin liquid film with antibacterial activity, where A is the membrane surface and B is the membrane cross section. DETAILED DESCRIPTION

[0033] The present invention is further described below by the description of specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not deviate from the basic idea of ​​the present invention, they are all within the scope of the present invention. The materials and reagents involved in the present invention are all food grade and can be obtained by commercially available or conventional technical means in the art. Wherein: the chitosan quaternary ammonium salt (also known as hydroxypropyl trimethyl ammonium chloride chitosan, chitosan quaternary ammonium salt) was purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0034] Example 1: Edible fish gelatin liquid film with antibacterial activity

[0035] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0036] Type A fish gelatin 42g, gum arabic 5g, glycerol 4g, soybean oil 120g, Tween 80 4g, nisin 4g and transglutaminase 0.5g.

[0037] Preparation method:

[0038] S1. Add type A fish gelatin into water, heat in a water bath to 40°C for 2 h, and stir until fully dissolved to obtain a fish gelatin solution;

[0039] S2. The temperature of the fish gelatin solution prepared in step S1 is controlled at 30°C, and then glycerol, soybean oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 8000rpm, shear time of 8min; the ultrasonic treatment conditions are: ultrasonic power of 250W, ultrasonic working time of 10min, to obtain a single-layer emulsion;

[0040] S3. Adding gum arabic to water, heating in a water bath to 40° C. for 2 h, stirring until fully dissolved, to obtain a gum arabic solution, then adding the gum arabic solution to the single-layer emulsion obtained in step S2, and subjecting to shear homogenization and ultrasonic treatment, wherein the shear homogenization conditions are: a shear rate of 8000 rpm and a shear time of 8 min; the ultrasonic treatment conditions are: an ultrasonic power of 250 W and an ultrasonic working time of 10 min, and then subjecting to high-pressure homogenization treatment, wherein the high-pressure homogenization treatment conditions are: a pressure of 100 MPa and a treatment time of 6 min, to obtain a double-layer emulsion;

[0041] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 40°C, glutamine aminotransferase is added, and the reaction is stirred for 1 hour. After the reaction is completed, the enzyme is inactivated in a 90°C water bath for 8 minutes, and high-pressure homogenization is performed. The conditions of the high-pressure homogenization treatment are: pressure of 80 MPa, treatment time of 2 minutes, and sealed filling.

[0042] Example 2: Edible fish gelatin liquid film with antibacterial activity

[0043] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0044] Type A fish gelatin 40g, gum arabic 8g, glycerol 4.2g, peanut oil 125g, Tween 80 4.2g, nisin 5g and transglutaminase 0.8g.

[0045] Preparation method:

[0046] S1. Add type A fish gelatin to 1L of water, heat in a water bath to 50°C for 1.5h, and stir until fully dissolved to obtain fish gelatin solution;

[0047] S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 35°C, and then glycerol, peanut oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 9000rpm, shear time of 5min; the ultrasonic treatment conditions are: ultrasonic power of 350W, ultrasonic working time of 8min, to obtain a single-layer emulsion;

[0048] S3. Add arabic gum to 1L of water, heat to 50°C in a water bath, heat for 1.5h, and stir until fully dissolved to obtain an arabic gum solution. Then add the arabic gum solution to the single-layer emulsion obtained in step S2, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 9000rpm, shear time of 5min; the ultrasonic treatment conditions are: ultrasonic power of 350W, ultrasonic working time of 8min, and then high-pressure homogenization treatment, the high-pressure homogenization treatment conditions are: pressure of 110Mpa, treatment time of 5min, to obtain a double-layer emulsion;

[0049] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 42°C, glutamine aminotransferase is added, and the reaction is stirred for 1.5 hours. After the reaction is completed, the enzyme is inactivated in a 95°C water bath for 6 minutes, and high-pressure homogenization is performed. The conditions of the high-pressure homogenization treatment are: pressure of 100 MPa, treatment time of 3 minutes, and sealed filling.

[0050] Example 3: Edible fish gelatin liquid film with antibacterial activity

[0051] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0052] Type A fish gelatin 38g, gum arabic 10g, glycerol 4.5g, olive oil 130g, Tween 80 4.5g, nisin 7g and transglutaminase 1g.

[0053] Preparation method:

[0054] S1. Add type A fish gelatin to 1L of water, heat in a water bath to 55°C for 1h, and stir until fully dissolved to obtain fish gelatin solution;

[0055] S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 40°C, and then glycerol, olive oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 10000rpm, shear time of 4min; the ultrasonic treatment conditions are: ultrasonic power of 450W, ultrasonic working time of 6min, to obtain a single-layer emulsion;

[0056] S3. Add arabic gum to 1L of water, heat to 55°C in a water bath, heat for 1h, and stir until fully dissolved to obtain an arabic gum solution. Then add the arabic gum solution to the single-layer emulsion obtained in step S2, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 10000rpm, shear time of 4min; the ultrasonic treatment conditions are: ultrasonic power of 450W, ultrasonic working time of 6min, and then high-pressure homogenization treatment, the high-pressure homogenization treatment conditions are: pressure of 120Mpa, treatment time of 3min, to obtain a double-layer emulsion;

[0057] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 45°C, glutamine aminotransferase is added, and the reaction is stirred for 1 hour. After the reaction is completed, the enzyme is inactivated in a water bath at 100°C for 5 minutes, and high-pressure homogenization is performed. The conditions of the high-pressure homogenization treatment are: pressure of 110 MPa, treatment time of 2 minutes, and sealed filling.

[0058] Example 4: Edible fish gelatin liquid film with antibacterial activity

[0059] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0060] Type A fish gelatin 42g, gum arabic 5g, glycerol 4g, soybean oil 120g, Tween 80 4g, nisin 4g, transglutaminase 0.5g and chitosan quaternary ammonium salt 3g.

[0061] Preparation method:

[0062] S1. Add type A fish gelatin into water, heat in a water bath to 40°C for 2 h, and stir until fully dissolved to obtain a fish gelatin solution;

[0063] S2. The temperature of the fish gelatin solution prepared in step S1 is controlled at 30°C, and then glycerol, soybean oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 8000rpm, shear time of 8min; the ultrasonic treatment conditions are: ultrasonic power of 250W, ultrasonic working time of 10min, to obtain a single-layer emulsion;

[0064] S3. Adding gum arabic to water, heating in a water bath to 40° C. for 2 h, stirring until fully dissolved, to obtain a gum arabic solution, then adding the gum arabic solution to the single-layer emulsion obtained in step S2, and subjecting to shear homogenization and ultrasonic treatment, wherein the shear homogenization conditions are: a shear rate of 8000 rpm and a shear time of 8 min; the ultrasonic treatment conditions are: an ultrasonic power of 250 W and an ultrasonic working time of 10 min, and then subjecting to high-pressure homogenization treatment, wherein the high-pressure homogenization treatment conditions are: a pressure of 100 MPa and a treatment time of 6 min, to obtain a double-layer emulsion;

[0065] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 40°C, glutamine aminotransferase is added, and the reaction is stirred for 1 hour. After the reaction is completed, the enzyme is inactivated in a water bath at 90°C for 8 minutes, and then chitosan quaternary ammonium salt is added. After stirring evenly, the mixture is allowed to stand for 2 to 3 minutes, and high-pressure homogenization is performed. The conditions for the high-pressure homogenization treatment are: pressure of 80 MPa, treatment time of 2 minutes, and sealed filling.

[0066] Example 5: Edible fish gelatin liquid film with antibacterial activity

[0067] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0068] Type A fish gelatin 40g, gum arabic 8g, glycerol 4.2g, peanut oil 125g, Tween 80 4.2g, nisin 5g, transglutaminase 0.8g and chitosan quaternary ammonium salt 2g.

[0069] Preparation method:

[0070] S1. Add type A fish gelatin to 1L of water, heat in a water bath to 50°C for 1.5h, and stir until fully dissolved to obtain fish gelatin solution;

[0071] S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 35°C, and then glycerol, peanut oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 9000rpm, shear time of 5min; the ultrasonic treatment conditions are: ultrasonic power of 350W, ultrasonic working time of 8min, to obtain a single-layer emulsion;

[0072] S3. Add arabic gum to 1L of water, heat to 50°C in a water bath, heat for 1.5h, and stir until fully dissolved to obtain an arabic gum solution. Then add the arabic gum solution to the single-layer emulsion obtained in step S2, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 9000rpm, shear time of 5min; the ultrasonic treatment conditions are: ultrasonic power of 350W, ultrasonic working time of 8min, and then high-pressure homogenization treatment, the high-pressure homogenization treatment conditions are: pressure of 110Mpa, treatment time of 5min, to obtain a double-layer emulsion;

[0073] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 42°C, glutamine aminotransferase is added, and the reaction is stirred for 1.5 hours. After the reaction is completed, the enzyme is inactivated in a 95°C water bath for 6 minutes, and then chitosan quaternary ammonium salt is added. After stirring evenly, the mixture is allowed to stand for 2 to 3 minutes, and high-pressure homogenization is performed. The conditions for the high-pressure homogenization treatment are: a pressure of 100 MPa, a treatment time of 3 minutes, and sealed and filled.

[0074] Example 6: Edible fish gelatin liquid film with antibacterial activity

[0075] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0076] Type A fish gelatin 38g, gum arabic 10g, glycerol 4.5g, olive oil 130g, Tween 80 4.5g, nisin 7g, transglutaminase 1g and chitosan quaternary ammonium salt 1g.

[0077] Preparation method:

[0078] S1. Add type A fish gelatin to 1L of water, heat in a water bath to 55°C for 1h, and stir until fully dissolved to obtain fish gelatin solution;

[0079] S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 40°C, and then glycerol, olive oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 10000rpm, shear time of 4min; the ultrasonic treatment conditions are: ultrasonic power of 450W, ultrasonic working time of 6min, to obtain a single-layer emulsion;

[0080] S3. Add arabic gum to 1L of water, heat to 55°C in a water bath, heat for 1h, and stir until fully dissolved to obtain an arabic gum solution. Then add the arabic gum solution to the single-layer emulsion obtained in step S2, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 10000rpm, shear time of 4min; the ultrasonic treatment conditions are: ultrasonic power of 450W, ultrasonic working time of 6min, and then high-pressure homogenization treatment, the high-pressure homogenization treatment conditions are: pressure of 120Mpa, treatment time of 3min, to obtain a double-layer emulsion;

[0081] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 45°C, glutamine aminotransferase is added, and the reaction is stirred for 1 hour. After the reaction is completed, the enzyme is inactivated in a water bath at 100°C for 5 minutes, and then chitosan quaternary ammonium salt is added. After stirring evenly, the mixture is allowed to stand for 2 to 3 minutes, and high-pressure homogenization is performed. The conditions for the high-pressure homogenization treatment are: a pressure of 110 MPa, a treatment time of 2 minutes, and sealed and filled.

[0082] Comparative Example 1: Edible fish gelatin liquid film with antibacterial activity

[0083] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0084] Type A fish gelatin 40g, gum arabic 8g, glycerol 4.2g, peanut oil 125g, Tween 80 4.2g and transglutaminase 0.8g.

[0085] Preparation method:

[0086] S1. Add type A fish gelatin to 1L of water, heat in a water bath to 50°C for 1.5h, and stir until fully dissolved to obtain fish gelatin solution;

[0087] S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 35°C, and then glycerol, peanut oil, and Tween 80 are added. After shear homogenization and ultrasonic treatment, the shear homogenization conditions are: a shear rate of 9000 rpm and a shear time of 5 min; the ultrasonic treatment conditions are: an ultrasonic power of 350 W and an ultrasonic working time of 8 min, to obtain a single-layer emulsion;

[0088] S3. Add arabic gum to 1L of water, heat to 50°C in a water bath, heat for 1.5h, and stir until fully dissolved to obtain an arabic gum solution. Then add the arabic gum solution to the single-layer emulsion obtained in step S2, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 9000rpm, shear time of 5min; the ultrasonic treatment conditions are: ultrasonic power of 350W, ultrasonic working time of 8min, and then high-pressure homogenization treatment, the high-pressure homogenization treatment conditions are: pressure of 110Mpa, treatment time of 5min, to obtain a double-layer emulsion;

[0089] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 42°C, glutamine aminotransferase is added, and the reaction is stirred for 1.5 hours. After the reaction is completed, the enzyme is inactivated in a 95°C water bath for 6 minutes, and high-pressure homogenization is performed. The conditions of the high-pressure homogenization treatment are: pressure of 100 MPa, treatment time of 3 minutes, and sealed filling.

[0090] Comparative Example 2: Edible fish gelatin liquid film with antibacterial activity

[0091] The edible fish gelatin liquid film with antibacterial activity is composed of the following components and their weight proportions:

[0092] Type A fish gelatin 40g, gum arabic 8g, glycerol 4.2g, peanut oil 125g, Tween 80 4.2g, nisin 5g, transglutaminase 0.8g and chitosan quaternary ammonium salt 2g.

[0093] Preparation method:

[0094] S1. Add type A fish gelatin to 1L of water, heat in a water bath to 50°C for 1.5h, and stir until fully dissolved to obtain fish gelatin solution;

[0095] S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 35°C, and then glycerol, peanut oil, Tween 80, nisin and chitosan quaternary ammonium salt are added, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 9000rpm, shear time of 5min; the ultrasonic treatment conditions are: ultrasonic power of 350W, ultrasonic working time of 8min, to obtain a single-layer emulsion;

[0096] S3. Add arabic gum to 1L of water, heat to 50°C in a water bath, heat for 1.5h, and stir until fully dissolved to obtain an arabic gum solution. Then add the arabic gum solution to the single-layer emulsion obtained in step S2, and after shear homogenization and ultrasonic treatment, the shear homogenization conditions are: shear rate of 9000rpm, shear time of 5min; the ultrasonic treatment conditions are: ultrasonic power of 350W, ultrasonic working time of 8min, and then high-pressure homogenization treatment, the high-pressure homogenization treatment conditions are: pressure of 110Mpa, treatment time of 5min, to obtain a double-layer emulsion;

[0097] S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 42°C, glutamine aminotransferase is added, and the reaction is stirred for 1.5 hours. After the reaction is completed, the enzyme is inactivated in a water bath at 95°C for 6 minutes, and high-pressure homogenization is performed. The conditions of the high-pressure homogenization treatment are: pressure of 100 MPa, treatment time of 3 minutes, and sealed filling.

[0098] 1. Test subjects:

[0099] The double-layer emulsions prepared in Example 1, Example 2 and Step S3 of Example 3.

[0100] 2. Test methods:

[0101] The particle size and potential value of the double-layer emulsions prepared in Example 1, Example 2 and Step S3 of Example 3 were detected, and then the particle size and potential value of the double-layer emulsions were measured again after being stored at 25°C for 3 weeks, wherein the particle size and potential value were detected using a Malvern particle size analyzer.

[0102] 3. Test results:

[0103] The test results are shown in Table 1.

[0104] Table 1 Stability test data of double-layer emulsion

[0105]

[0106] As can be seen from Table 1, the particle size distribution of the double-layer emulsions prepared in Examples 1 to 3 of the present invention is uniform, and the large absolute value of the potential is conducive to the stability of the double-layer emulsion. The particle size and potential value of the double-layer emulsion after storage at 25°C for 3 weeks change little, indicating that the double-layer emulsion prepared by the present invention has high stability.

[0107] Test Example 2: Film Formation Test of Edible Fish Gelatin Liquid Film with Antibacterial Activity

[0108] 1. Test subjects:

[0109] The edible fish gelatin liquid film with antibacterial activity prepared in Example 2.

[0110] 2. Test methods:

[0111] 15 mL of the edible fish gelatin liquid membrane with antibacterial activity prepared in Example 2 was transferred to a culture dish, naturally air-dried, sprayed with gold, and then tested by scanning electron microscopy.

[0112] 3. Test results:

[0113] The results of SEM test are as follows Figure 1 As shown by Figure 1 From the microstructure, the size of the film is relatively consistent and there are no large cracks, which shows that the edible fish gelatin liquid film with antibacterial activity prepared by the present invention can form a complete film with mechanical properties on the surface of food after drying.

[0114] Test Example 3: Test on the preservation effect of edible fish gelatin liquid film with antibacterial activity

[0115] 1. Test subjects:

[0116] Edible fish gelatin liquid films with antibacterial activity prepared in Example 1, Example 2, Example 3 and Comparative Example 1.

[0117] 2. Test methods:

[0118] The preservation effect of the edible fish gelatin liquid film with antibacterial activity prepared in Example 1, Example 2, Example 3 and Comparative Example 1 on salmon was detected, and the total colony count, K value and TVB-N content of the salmon soaked in the edible liquid preservative film of fish gelatin were detected. The salmon meat purchased in the market, the materials in contact with the fish meat must be sterilized in advance, cut into fish pieces of similar size at room temperature, and ultraviolet irradiation in an ice bath for 15 minutes to kill surface microorganisms, and then the fish pieces were immersed in the edible fish gelatin liquid film with antibacterial activity prepared in Example 1, Example 2, Example 3 and Comparative Example 1 for 30 seconds, and the process of cutting to coating was controlled to be completed within 20 minutes, and then immediately placed in -20°C refrigeration for 1 minute, so that the edible liquid preservative film of fish gelatin can quickly form a solid film on the surface of the salmon meat. The fish meat without coating preservation was used as the control group, and all the fish meat was placed in a plate, covered with a lid, and stored at 4°C.

[0119] 2.1. Determination of total colony count: The total colony count was measured every 2 days, with the end point being when the total colony count in fish meat reached 7 log cfu / g. The days to reach this end point were recorded for each group of fish meat.

[0120] 2.2. K value determination: refer to the national standard SC / T 3048-2014 method and measure once every 3 days, and record the K value within 12 days.

[0121] 2.3. Determination of TVB-N content: The changes in TVB-N content in fish meat during storage were determined by semi-micro nitrogen determination. The measurement was conducted every 3 days, and the K value of TVB-N content was recorded within 12 days.

[0122] 3. Test results:

[0123] The test results are shown in Tables 2 to 4.

[0124] Table 2 Determination data of total colony count of edible fish gelatin liquid film with antibacterial activity

[0125] Days for the total colony count in fish meat to reach 7 log cfu / g Control group Day 6 (total colony count was 7.05±0.32log cfu / g) Example 1 Day 14 (total colony count was 7.02±0.31log cfu / g) Example 2 Day 14 (total colony count was 7.00±0.29log cfu / g) Example 3 Day 14 (total colony count was 7.04±0.30log cfu / g) Comparative Example 1 Day 6 (total colony count was 7.1±0.28log cfu / g)

[0126] As can be seen from Table 2, there is no significant difference in the number of days to reach 7log cfu / g between the control group and the comparative example 1 group during storage, while the salmon treated with the edible fish gelatin liquid film with antibacterial activity prepared by Examples 1 to 3 of the present invention can greatly extend the number of days to reach 7log cfu / g of the total colony count of the fish meat, thereby greatly extending the shelf life of the fish meat.

[0127] Table 3 K value determination data of edible fish gelatin liquid film with antibacterial activity

[0128] Day 0 Day 3 Day 6 Day 9 Day 12 Control group 11.97±0.78 23.12±2.36 39.55±1.63 60.84±2.75 82.31±1.68 Example 1 12.03±1.54 16.43±1.23 33.87±2.03 40.11±1.54 60.78±3.15 Example 2 11.99±1.06 15.14±1.24 30.56±1.87 36.55±1.23 50.35±2.87 Example 3 12.05±1.21 17.18±1.30 34.74±2.06 42.09±1.98 61.44±3.09 Comparative Example 1 11.87±1.01 24.89±1.47 42.29±1.5 66.58±1.69 86.29±2.75

[0129] It can be seen from Table 3 that the K value of the salmon treated with the edible fish gelatin liquid film with antibacterial activity prepared in Examples 1 to 3 of the present invention increases slowly, indicating that the fish gelatin edible liquid preservative film prepared in the present invention can slow down the increase in K value during the storage of fish.

[0130] Table 4 Determination data of TVB-N content in edible fish gelatin liquid film with antibacterial activity

[0131] Day 0 Day 3 Day 6 Day 9 Day 12 Control group 13.64±0.30 19.21±0.12 23.45±0.26 25.31±0.39 29.04±0.19 Example 1 13.91±0.44 17.12±0.21 18.05±0.17 19.20±0.34 20.33±0.21 Example 2 13.34±0.42 16.85±0.25 17.13±0.15 18.42±0.35 18.97±0.25 Example 3 13.88±0.39 17.31±0.22 18.54±0.20 19.98±0.36 20.99±0.23 Comparative Example 1 13.87±0.62 18.9±0.24 23.78±0.31 26.01±0.26 31.36±0.75

[0132] It can be seen from Table 4 that the TVB-N content of the salmon treated with the edible fish gelatin liquid film with antibacterial activity prepared in Examples 1 to 3 of the present invention increases slowly, indicating that the fish gelatin edible liquid preservative film prepared in the present invention can effectively reduce the TVB-N content during the storage of fish.

[0133] Test Example 4: Test on the preservation effect of edible fish gelatin liquid film with antibacterial activity

[0134] 1. Test subjects:

[0135] Edible fish gelatin liquid films with antibacterial activity prepared in Example 2, Example 4, Example 5, Example 6 and Comparative Example 2.

[0136] 2. Test methods:

[0137] Referring to the test method of Test Example 3, the preservation effect of the edible fish gelatin liquid film with antibacterial activity prepared in Example 2, Example 4, Example 5, Example 6 and Comparative Example 2 on salmon was determined, and the total colony count, K value and TVB-N content of the salmon soaked in the fish gelatin edible liquid preservative film were detected. The situation and days of the appearance of liquid in the fish meat during the detection process were observed and recorded, and the K value and TVB-N content recorded the data on the 0th day and the 12th day.

[0138] 3. Test results:

[0139] The test results are shown in Table 5.

[0140] Table 5 Determination data of the preservation effect of edible fish gelatin liquid film with antibacterial activity

[0141]

[0142] From Table 5, we can see that:

[0143] (1) Compared with Example 2, the edible fish gelatin liquid film with antibacterial activity prepared in Examples 4 to 6 with the addition of chitosan quaternary ammonium salt has improved antibacterial effect, water absorption effect, and effect of reducing K value and TVB-N content compared with Example 2, indicating that the addition of chitosan quaternary ammonium salt can further improve the preservation effect of fish gelatin edible liquid preservative film on salmon, extend the preservation days, reduce the appearance of fish liquid, and further improve the preservation quality of salmon.

[0144] (2) Compared with Example 2, the edible fish gelatin liquid film with antibacterial activity prepared in Comparative Example 2 with the addition of chitosan quaternary ammonium salt has lower antibacterial effect, water absorption effect, and effect of reducing K value and TVB-N content than that of Example 2. The inventors speculate that the reason is that embedding chitosan quaternary ammonium salt in fish gelatin will cause cross-linking, which not only seriously affects the mechanical properties of the cling film, improves the water solubility of the cling film, and shortens the service life of the cling film, but also restricts the movement of the cross-linked chitosan and quaternary ammonium salt, and its antibacterial effect will also be reduced.

[0145] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An edible fish gelatin liquid film with antibacterial activity, characterized in that: It includes the following ingredients and their weight parts: 38-42 parts of fish gelatin, 3-12 parts of gum arabic, 3-8 parts of glycerol, 110-130 parts of edible oil, 3-8 parts of Tween 80, 3-8 parts of nisin and 0.2-2 parts of transglutaminase; The edible fish gelatin liquid film with antibacterial activity also includes 1 to 3 parts of chitosan quaternary ammonium salt; The method for preparing an edible fish gelatin liquid film having antibacterial activity comprises the following steps: S1. Add fish gelatin to water, heat in a water bath to 40-60°C for 1-2 h, and stir until fully dissolved to obtain fish gelatin solution; S2. The temperature of the fish gelatin solution obtained in step S1 is controlled at 30-40°C, and then glycerol, cooking oil, Tween 80 and nisin are added, and after shear homogenization and ultrasonic treatment, a monolayer emulsion is obtained; S3. Adding gum arabic to water, heating in a water bath to 40-60°C for 1-2 h, stirring until fully dissolved, to obtain a gum arabic solution, then adding the gum arabic solution to the single-layer emulsion obtained in step S2, subjecting the mixture to shear homogenization and ultrasonic treatment, and then high-pressure homogenization to obtain a double-layer emulsion; S4. The temperature of the double-layer emulsion obtained in step S3 is controlled at 40-45°C, glutamine transaminase is added, and the reaction is stirred for 1-2 h. After the reaction is completed, the enzyme is inactivated in a water bath at 90-100°C for 5-8 min, high-pressure homogenization is performed, and the mixture is sealed and filled to obtain the product; The step S4 also includes adding chitosan quaternary ammonium salt, and the specific adding steps are: after the enzyme is inactivated, chitosan quaternary ammonium salt is added, stirred evenly, left to stand for 2-3 minutes, subjected to high pressure homogenization, and sealed and filled.

2. The edible fish gelatin liquid film with antibacterial activity according to claim 1, characterized in that: It is composed of the following ingredients and their weight parts: 40 parts of fish gelatin, 5-10 parts of gum arabic, 4-5 parts of glycerol, 120-125 parts of edible oil, 4-5 parts of Tween 80, 4-7 parts of nisin and 0.5-1 part of transglutaminase.

3. The edible fish gelatin liquid film with antibacterial activity according to claim 1 or 2, characterized in that: The fish gelatin is type A fish gelatin, and the edible oil is one or a combination of two or more of soybean oil, peanut oil, rapeseed oil, perilla oil and olive oil.

4. The edible fish gelatin liquid film with antibacterial activity according to claim 1, characterized in that: The conditions for shear homogenization in step S2 and step S3 are: shear rate of 6000-12000 rpm, shear time of 3-10 min; the conditions for ultrasonic treatment are: ultrasonic power of 200-500 W, ultrasonic working time of 3-15 min.

5. The edible fish gelatin liquid film with antibacterial activity according to claim 1, characterized in that: The conditions for the high-pressure homogenization treatment in step S3 are: a pressure of 80-120 MPa and a treatment time of 3-8 min.

6. The edible fish gelatin liquid film with antimicrobial activity according to claim 1, characterized in that: The conditions for the high-pressure homogenization treatment in step S4 are: a pressure of 80-120 MPa and a treatment time of 2-5 min.

7. The edible fish gelatin liquid film with antibacterial activity according to claim 1, characterized in that: The pH of the prepared edible fish gelatin liquid film with antibacterial activity is 5.5-6.0.

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