Preparation method and application of fish skin albumen glue edible film

Abstract

The invention discloses a preparation method and application of a fish skin albumen glue edible film, and belongs to the technical field of food film packaging and preparation.The method comprises the steps that a fish skin albumen glue solution and a low-acyl gellan gum solution are mixed, first homogenization treatment, high-pressure microjet treatment and spray drying treatment are sequentially conducted, and a fish skin albumen glue mixture is obtained; dissolving in water, adding glycerol and stirring to obtain a mixed solution; and after ultrasonic defoaming treatment, putting into a mold, drying and demolding to obtain the fish skin albumen glue edible film. When the fish skin albumen glue prepared by the preparation method provided by the invention is applied to the manufacturing process of the film, the safety performance of the film can be effectively improved, the advantage of degradability is beneficial to environmental protection, and in addition, the film produced by adopting the fish skin albumen glue has the advantages of degradability, edibility, good mechanical property, high safety and the like.

Description

Technical Field

[0001] The present application belongs to the technical field of food film packaging preparation, and specifically relates to a preparation method and application of a fish skin protein glue edible film. Background Art

[0002] At present, with the improvement of people's living standards, the concept of healthy life has gradually been deeply rooted in people's hearts. The quality of food packaging is also directly related to the freshness and safety of the food in the package, especially the research and development and application of emerging edible films, antibacterial films and other products. Protein glue is a product obtained by moderate hydrolysis and thermal denaturation of collagen, and has the advantages of good film-forming properties, good toughness and strength, and degradability. Fish skin contains rich collagen, which can be used as an important source for preparing protein glue, and fish skin protein glue is not restricted by religious culture. Compared with mammal protein glue, fish skin protein glue is safer and is a high-quality base material for the development of edible films. However, fish skin protein glue shows lower gel properties, especially the melting temperature and gel temperature, which has become the main factor limiting the application of fish skin protein glue instead of mammal protein glue. Summary of the invention

[0003] The purpose of the embodiments of the present application is to provide a method for preparing an edible fish skin protein glue film, which can solve the problem of low melting temperature and gel temperature.

[0004] In order to solve the above technical problems, this application is implemented as follows: In a first aspect, the present application provides a method for preparing an edible fish skin protein glue film, comprising the following steps: The fish skin protein glue solution and the low acyl gellan gum solution are mixed to obtain a fish skin protein glue-low acyl gellan gum mixed solution; The fish skin protein glue-low acyl gellan gum mixed solution is sequentially subjected to a first homogenization treatment, a high-pressure microfluidization treatment and a spray drying treatment to obtain a fish skin protein glue mixture; Dissolving the fish skin protein glue mixture in water to obtain a fish skin protein glue mixed solution; Adding glycerol to the fish skin protein glue mixed solution and stirring to obtain a mixed solution; Performing ultrasonic defoaming treatment on the mixed solution to obtain a defoaming solution; The defoaming solution is placed in a mold, dried at a preset temperature and preset humidity, and demoulded to obtain an edible fish skin protein glue film.

[0005] Optionally, the step of adding glycerol to the fish skin protein glue mixed solution and stirring to obtain a mixed solution specifically comprises: Glycerol and anthocyanidin are added to the fish skin protein glue mixed solution and stirred to obtain a mixed solution.

[0006] Optionally, the mass ratio of the fish skin protein gelatin, glycerol and anthocyanin is 1:0.1:0.1 to 1:0.5:0.3.

[0007] Optionally, the anthocyanidin is black wolfberry anthocyanidin, and before the step of adding glycerol and anthocyanidin to the fish skin protein gel mixed solution and stirring to obtain a mixed solution, the preparation method further comprises: According to a preset material-liquid ratio, the pretreated black wolfberry is placed in an ethanol solution to obtain a mixed solution; The mixed solution is subjected to a second homogenization treatment and a high-voltage pulse electric field treatment in sequence, and then allowed to stand to obtain a supernatant; The supernatant is subjected to rotary evaporation drying to obtain the black wolfberry anthocyanin; The preset material-liquid ratio is: the usage ratio of black wolfberry to ethanol solution is 30g:1L~50g:1L, wherein the concentration of ethanol solution is 70%~80%.

[0008] Optionally, the treatment conditions in the second homogenization process are: pressure 10 MPa to 50 MPa, and treatment times 1 to 8 times; The treatment conditions in the above high-voltage pulse electric field treatment process are: electric field intensity of 30 kV / cm to 60 kV / cm, and the number of pulses of 4 to 8 times.

[0009] Optionally, after placing the defoaming solution in a mold, drying at a preset temperature and preset humidity, and demolding, the preparation method further comprises: The demoulded protein glue is placed in a desiccator for storage to obtain the fish skin protein glue edible film.

[0010] Optionally, the volume ratio of the fish skin protein glue solution to the low acyl gellan gum solution in the above-mentioned fish skin protein glue-low acyl gellan gum mixed solution is 99.5:0.5 to 80:20.

[0011] Optionally, the mass fraction of fish skin protein glue in the above fish skin protein glue solution is 5% to 10%; The mass fraction of low acyl gellan gum in the above-mentioned low acyl gellan gum solution is 1% to 3%.

[0012] Optionally, the treatment conditions in the first homogenization process are: pressure 10 MPa to 50 MPa, treatment times 1 to 8 times; The treatment conditions in the above high-pressure microfluidization treatment process are: pressure 50 MPa to 250 MPa, treatment times 1 to 9 times; The treatment conditions in the above-mentioned spray drying process are: inlet air temperature 175℃~185℃, outlet air temperature 80℃~100℃.

[0013] In a second aspect, an embodiment of the present application provides an application of an edible film of fish skin protein glue prepared by the above-mentioned preparation method in food packaging, and the edible film of fish skin protein glue can analyze the freshness of food according to the pH value.

[0014] In the embodiments of the present application, the present invention adopts low acyl gellan gum to effectively improve the gel properties of fish protein glue, expands the application range of fish skin protein glue, and promotes the interaction between fish protein glue and low acyl gellan gum through homogenization treatment combined with dynamic high-pressure microfluidization treatment. Compared with the simple mixing of fish protein glue and low acyl gellan gum, the gel properties of fish protein glue are improved, thereby improving the performance of protein glue film. Therefore, the fish skin protein glue prepared by the preparation method proposed in the present invention is applied to the production process of the film, which can effectively improve the safety performance of the film, and the advantage of being degradable is beneficial to environmental protection. In addition, the film produced by the present invention and using fish skin protein glue has the advantages of being degradable, edible, having good mechanical properties, and high safety. DETAILED DESCRIPTION

[0015] The following will be combined with the specific embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0016] The preparation method and application of the fish skin protein glue edible film provided in the embodiments of the present application are described in detail below through specific examples and application scenarios.

[0017] In a first aspect, the present application provides a method for preparing a fish skin protein glue edible film, comprising the following steps: The fish skin protein glue solution and the low acyl gellan gum solution are mixed to obtain a fish skin protein glue-low acyl gellan gum mixed solution; The fish skin protein glue-low acyl gellan gum mixed solution is sequentially subjected to a first homogenization treatment, a high-pressure microfluidization treatment and a spray drying treatment to obtain a fish skin protein glue mixture; Dissolving the fish skin protein glue mixture in water to obtain a fish skin protein glue mixed solution; Adding glycerol to the fish skin protein glue mixed solution and stirring to obtain a mixed solution; Performing ultrasonic defoaming treatment on the mixed solution to obtain a defoaming solution; The defoaming solution is placed in a mold, dried at a preset temperature and preset humidity, and demoulded to obtain the fish skin protein glue edible film.

[0018] The beneficial effects of the present invention are that the use of low-acyl gellan gum can effectively improve the gelling properties of fish protein glue, expand the application range of fish skin protein glue, promote the interaction between fish protein glue and low-acyl gellan gum through homogenization treatment combined with dynamic high-pressure microfluidization treatment, and improve the stability of the gel network structure by promoting the formation of non-covalent bonds such as hydrogen bonds and hydrophobic forces between the two. Compared with the simple mixing of fish protein glue and low-acyl gellan gum, the gelling properties of fish protein glue are improved, thereby improving the performance of the protein glue film. Therefore, the fish skin protein glue prepared by the preparation method proposed by the present invention is applied to the production process of the film, which can effectively improve the safety performance of the film, and the advantage of being degradable is beneficial to environmental protection.

[0019] In some embodiments, the step of adding glycerol to the above-mentioned fish skin protein mixed gel solution and stirring to obtain a mixed solution specifically includes: Glycerol and anthocyanidin are added to the fish skin protein glue mixed solution and stirred to obtain a mixed solution.

[0020] The present invention adds anthocyanin into the film, which can be used to display different colors under different pH values, and can timely and accurately analyze the freshness of food.

[0021] In some embodiments, the mass ratio of the fish skin protein gelatin, glycerol, and anthocyanidin is 1:0.1:0.1 to 1:0.5:0.3. In the above preparation process, if there is too much or too little glycerol, it will be difficult to form a film; if there is too much anthocyanidin, the color will be difficult to distinguish, resulting in difficulty in observation and waste.

[0022] In some embodiments, the anthocyanidin is black wolfberry anthocyanidin, and before the step of adding glycerol and anthocyanidin to the fish skin protein gel mixed solution and stirring to obtain a mixed solution, the preparation method further comprises: According to a preset material-liquid ratio, the pretreated black wolfberry is placed in an ethanol solution to obtain a mixed solution; The mixed solution is subjected to a second homogenization treatment and a high-voltage pulse electric field treatment in sequence, and then allowed to stand to obtain a supernatant; The supernatant is subjected to rotary evaporation drying to obtain the black wolfberry anthocyanin; The preset material-liquid ratio is: the dosage ratio of black wolfberry to ethanol solution is 30g:1L~50g:1L, wherein the concentration of ethanol solution is 70%~80%. Compared with other anthocyanins, the wolfberry anthocyanin used in the present invention has high content and high physiological activity; and the anthocyanin extracted by homogenization and high-voltage pulse electric field extraction steps not only improves the extraction efficiency, but also reduces the use of organic solvents, which is a more environmentally friendly and efficient extraction method.

[0023] The pretreatment process of black wolfberry in the above extraction step is: selecting black wolfberry with good appearance, cleaning the mud and impurities on the surface of the wolfberry, draining the surface water and then grinding.

[0024] In some embodiments, the treatment conditions in the second homogenization process are: pressure 10 MPa to 50 MPa, treatment times 1 to 8 times; The treatment conditions in the high-voltage pulse electric field treatment process are: electric field strength 30 kV / cm to 60 kV / cm, and the number of pulses is 4 to 8. In the above preparation process, too high or too low conditions in the homogenization process and the high-voltage pulse electric field treatment process will lead to low extraction efficiency.

[0025] In some embodiments, after placing the defoaming solution in a mold, drying at a preset temperature and a preset humidity, and demolding, the preparation method further comprises: The demoulded protein glue is placed in a desiccator for storage to obtain the fish skin protein glue edible film.

[0026] The method of the present invention places the demoulded protein glue in a dryer for storage, so that the performance of the fish skin protein glue edible film is better when it is used later.

[0027] In some embodiments, the volume ratio of the fish skin protein gelatin solution to the low acyl gellan gum solution in the fish skin protein gelatin-low acyl gellan gum mixed solution is 99.5:0.5 to 80:20. In the preparation process of the present invention, the volume ratio of the fish skin protein gelatin solution to the low acyl gellan gum solution is optimal within this range. If it exceeds this range, problems such as weakened gel performance will occur.

[0028] In some embodiments, the mass fraction of fish skin protein glue in the above fish skin protein glue solution is 5% to 10%; The mass fraction of low acyl gellan gum in the above-mentioned low acyl gellan gum solution is 1% to 3%.

[0029] In the preparation process of the present invention, the mass fraction of fish skin protein glue and the mass fraction of low acyl gellan gum have better solubility within the above range and can be better mixed evenly; if the mass fraction is too large, mixing stratification will occur, and if it is too small, the gel performance improvement will not be obvious.

[0030] In some embodiments, the treatment conditions in the first homogenization process are: pressure 10 MPa to 50 MPa, treatment times 1 to 8 times; The treatment conditions in the above high-pressure microfluidization treatment process are: pressure 50 MPa to 250 MPa, treatment times 1 to 9 times; The treatment conditions in the above-mentioned spray drying process are: inlet air temperature 175℃~185℃, outlet air temperature 80℃~100℃. In the above-mentioned preparation process, spray drying is used. If the inlet air temperature is too high, the product temperature may exceed its extreme tolerance temperature, causing the product to overheat or denature; if the outlet air temperature is too high, the product may continue to dry after leaving the drying tower, resulting in overdrying or degradation of product performance. On the contrary, if the outlet air temperature is too low, the moisture content of the product may be too high, affecting its stability and subsequent application.

[0031] The concentrations of fish skin protein glue and low acyl gellan gum in the preparation of the fish skin protein glue-low acyl gellan gum mixed solution are inconsistent with the glue concentration required for the subsequent preparation of the film. The film requires a higher glue concentration and a lower water content, so spray drying is used to treat the glue, which is beneficial to the subsequent preparation of the film.

[0032] In a second aspect, the present application provides an application of an edible fish skin protein glue film prepared by the above-mentioned preparation method in food packaging, wherein the edible fish skin protein glue film can analyze the freshness of food according to the pH value.

[0033] Example 1 A method for preparing a fish skin protein glue edible film specifically comprises the following steps: (1) dissolving fish skin protein glue in distilled water to obtain a fish skin protein glue solution with a solute mass fraction of 6%; dissolving low acyl gellan gum in distilled water to obtain a low acyl gellan gum solution with a solute mass fraction of 2%; mixing the 6% fish skin protein glue solution and the 2% low acyl gellan gum solution in a volume ratio of 99.5:0.5 to obtain a fish skin protein glue-low acyl gellan gum mixed solution; (2) subjecting the fish skin protein glue-low acyl gellan gum mixed solution to homogenization treatment (pressure set to 50 MPa, treatment times 6 times) and high-pressure microfluidization treatment (pressure set to 200 MPa, treatment times 8 times), and spray drying (inlet air temperature of 180° C., outlet air temperature of 90° C.) to obtain a fish skin protein glue mixture; (3) dissolving the fish skin protein glue mixture in distilled water to obtain a fish skin protein glue mixed solution with a solute mass fraction of 6%; (4) adding glycerol to the fish skin protein glue mixed solution at a mass ratio of 1:0.25, and stirring for 30 min at 50° C. to fully mix the mixture, thereby obtaining a mixed solution; (5) After ultrasonic defoaming treatment, the mixed solution is evenly poured onto a mold (with a diameter of 10 cm) and dried in a constant temperature and humidity incubator at a temperature of (25±1)°C and a relative humidity of (50±5)% for 24 h. The dried protein film is manually peeled off and placed in a desiccator for storage to obtain an edible fish skin protein glue film.

[0034] Example 2 A method for preparing an edible fish skin protein glue film, which is different from Example 1 in that the step (1) of uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 99.5:0.5 is replaced by uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 99:1, and the other steps are the same as Example 1, to obtain an edible fish skin protein glue film.

[0035] Example 3 A method for preparing an edible fish skin protein glue film, which is different from Example 1 in that the step (1) of uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 99.5:0.5 is replaced by uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 97.5:2.5, and the other steps are the same as Example 1, to obtain an edible fish skin protein glue film.

[0036] Example 4 A method for preparing an edible fish skin protein glue film, which is different from Example 1 in that the step (1) of uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 99.5:0.5 is replaced by uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 92.5:7.5, and the other steps are the same as Example 1, to obtain an edible fish skin protein glue film.

[0037] Example 5 A method for preparing an edible fish skin protein glue film, which is different from Example 1 in that the step (1) of uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 99.5:0.5 is replaced by uniformly mixing a 6% fish skin protein glue solution and a 2% low acyl gellan gum solution in a volume ratio of 80:20, and the other steps are the same as Example 1, to obtain an edible fish skin protein glue film.

[0038] Example 6 A method for preparing a fish skin protein glue edible film specifically comprises the following steps: (1) dissolving fish skin protein glue in distilled water to obtain a fish skin protein glue solution with a solute mass fraction of 6%; dissolving low acyl gellan gum in distilled water to obtain a low acyl gellan gum solution with a solute mass fraction of 2%; mixing the 6% fish skin protein glue solution and the 2% low acyl gellan gum solution in a volume ratio of 99.5:0.5 to obtain a fish skin protein glue-low acyl gellan gum mixed solution; (2) subjecting the fish skin protein glue-low acyl gellan gum mixed solution to homogenization treatment (pressure set to 50 MPa, treatment times 6 times) and high-pressure microfluidization treatment (pressure set to 200 MPa, treatment times 8 times), and spray drying (inlet air temperature of 180° C., outlet air temperature of 90° C.) to obtain a fish skin protein glue mixture; (3) dissolving the fish skin protein glue mixture in distilled water to obtain a fish skin protein glue mixed solution with a solute mass fraction of 6%; (4) adding glycerol and anthocyanin to the fish skin protein glue mixed solution according to the mass ratio of fish skin protein glue: glycerol: anthocyanin being 1:0.1:0.2, and stirring continuously for 30 minutes at 50° C. to fully mix the mixture to obtain a mixed solution; (5) After ultrasonic defoaming treatment, the mixed solution is evenly poured onto a mold (with a diameter of 10 cm) and dried in a constant temperature and humidity incubator at a temperature of (25±1)°C and a relative humidity of (50±5)% for 24 h. The dried protein film is manually peeled off and placed in a desiccator for storage to obtain an edible fish skin protein glue film.

[0039] The anthocyanidin used in this embodiment is wolfberry anthocyanidin, and its extraction process is as follows: S1: Select black wolfberries with good appearance, clean the mud and impurities on the surface of the wolfberries, drain the surface water and grind them, then add ethanol (78%) solution at a solid-liquid ratio of 35 g: 1 L to obtain a mixed solution; S2: The mixed solution was homogenized (the pressure was set to 50 MPa and the number of treatments was 8 times), and then subjected to a high-voltage pulse electric field treatment (the electric field strength was 40 kV / cm and the number of pulses was 6.8 times). After the treatment, the mixture was allowed to stand for 18 hours to obtain a supernatant; S3: The supernatant after standing is dried by rotary evaporation at 50°C to obtain wolfberry anthocyanins, which are then stored at low temperature and away from light.

[0040] Example 7 A method for preparing an edible fish skin protein glue film, which is different from Example 6 in that the mass ratio of fish skin protein glue: glycerol: anthocyanin in step (4) is replaced with a mass ratio of fish skin protein glue: glycerol: anthocyanin of 1:0.1:0.2, and the other steps are the same as Example 6 to obtain an edible fish skin protein glue film.

[0041] Example 8 A method for preparing an edible fish skin protein glue film, which is different from Example 6 in that the mass ratio of fish skin protein glue: glycerol: anthocyanin in step (4) is replaced with a mass ratio of fish skin protein glue: glycerol: anthocyanin of 1:0.5:0.2, and the other steps are the same as Example 6 to obtain an edible fish skin protein glue film.

[0042] Comparative Example 1 A method for preparing a pigskin protein glue edible film comprises the following steps: (1) dissolving pigskin protein glue in distilled water to obtain a pigskin protein glue solution with a solute mass fraction of 6%; (2) subjecting the pigskin protein glue solution to homogenization treatment (pressure set to 50 MPa, treatment times 6 times) and high-pressure microfluidization treatment (pressure set to 200 MPa, treatment times 8 times), and spray drying (inlet air temperature of 180°C, outlet air temperature of 90°C) to obtain a pigskin protein glue mixture; (3) dissolving the pigskin protein glue mixture in distilled water to obtain a pigskin protein glue mixed solution with a solute mass fraction of 5% to 10%; (4) adding glycerol and anthocyanin to the mixed solution of pigskin protein glue according to the mass ratio of pigskin protein glue: glycerol: anthocyanin of 1:0.25:0.2, and stirring for 30 minutes at 50°C to fully mix the mixture, thereby obtaining a mixed solution; (5) After ultrasonic defoaming treatment, the mixed solution was evenly poured onto a mold (with a diameter of 10 cm) and dried in a constant temperature and humidity incubator at a temperature of (25±1)°C and a relative humidity of (50±5)% for 24 h. The dried protein film was manually peeled off and placed in a desiccator for storage to obtain an edible pig skin protein glue film.

[0043] The anthocyanins used in this example are consistent with those in Example 6.

[0044] Comparative Example 2 A method for preparing a fish skin protein glue edible film specifically comprises the following steps: (1) dissolving fish skin protein glue in distilled water to obtain a fish skin protein glue solution with a solute mass fraction of 6%; (2) subjecting the fish skin protein glue solution to homogenization treatment (pressure set to 50 MPa, treatment times 6 times) and high-pressure microfluidization treatment (pressure set to 200 MPa, treatment times 8 times), and spray drying (inlet air temperature of 180° C., outlet air temperature of 90° C.), to obtain fish skin protein glue; (3) dissolving fish skin protein glue in distilled water to obtain a fish skin protein glue mixed solution with a solute mass fraction of 5% to 10%; (4) adding glycerol and anthocyanin to the fish skin protein glue mixed solution according to the mass ratio of fish skin protein glue: glycerol: anthocyanin being 1:0.25:0.2, and stirring continuously for 30 minutes at 50° C. to fully mix the mixture to obtain a mixed solution; (5) After ultrasonic defoaming treatment, the mixed solution is evenly poured onto a mold (with a diameter of 10 cm) and dried in a constant temperature and humidity incubator at a temperature of (25±1)°C and a relative humidity of (50±5)% for 24 h. The dried protein film is manually peeled off and placed in a desiccator for storage to obtain an edible fish skin protein glue film.

[0045] Comparative Example 3 A method for preparing a fish skin protein glue edible film specifically comprises the following steps: (1) dissolving fish skin protein glue in distilled water to obtain a fish skin protein glue solution with a solute mass fraction of 6%; (2) adding glycerol and anthocyanin to the fish skin protein glue mixed solution according to the mass ratio of fish skin protein glue: glycerol: anthocyanin of 1:0.25:0.2, and stirring for 30 minutes at 50°C to fully mix the mixture, thereby obtaining a mixed solution; (3) After ultrasonic defoaming treatment, the mixed solution is evenly poured onto a mold (with a diameter of 10 cm) and dried in a constant temperature and humidity incubator at a temperature of (25±1)°C and a relative humidity of (50±5)% for 24 h. The dried protein film is manually peeled off and placed in a desiccator for storage to obtain an edible fish skin protein glue film.

[0046] Example 9 The fish skin protein gel edible film prepared in Example 8 was cut into 3 cm×3 cm sizes and placed in buffer solutions with a pH of 2 to 12. After standing for 5 min, the color change of the film was observed. The results are shown in Table 1.

[0047] Table 1 Note: -1 to -4 means the color becomes lighter and lighter visibly to the naked eye; +1 to +2 means the color becomes darker and darker visibly to the naked eye.

[0048] As can be seen from Table 1, the fish skin protein glue edible film shows different colors in different pH solutions, and can be used for rapid detection of the freshness and safety of packaged food.

[0049] Example 10 The fish skin protein glue mixture prepared in step (2) of Examples 1 to 5 and the pig skin protein glue mixture and fish skin protein glue prepared in step 2 of Comparative Examples 1 to 3 were tested for gelation temperature and melting temperature, respectively. The protein glue edible films and pig skin protein glue edible films prepared in Examples 6 to 8 and Comparative Examples 1 to 2 were tested for film thickness, tensile strength, elongation at break and water vapor transmission rate, respectively. The specific process is as follows: The method for testing the glue temperature and the melting temperature of the glue is as follows: a temperature scanning test of the protein glue is performed using a rheometer with a PP50 cylinder. Maintain at 40°C for 5 minutes, strain 0.5%, frequency 1Hz, according to 0.5°C / min, from 40°C to 5°C, maintain at 5°C for 30 minutes, and then from 5°C to 40°C. The method for testing the thickness of the film is as follows: a digital thickness gauge is used to measure the thickness of the film. Six pieces of each film are selected for measurement, and 9 points are selected for each piece, one of which is the center point. The method for testing the water vapor permeability is as follows: dry silica gel is placed in a 10 mL beaker with a diameter of 2.5 cm, the mouth of the beaker is covered with a film, and the small beaker is placed in a (25±1)°C drying dish filled with distilled water, and the mass of the beaker is measured every 1 h. Water vapor permeability = (Δm×d) / (A×t×Δp), where: ∆m is the increase in mass of the beaker at time interval t / g; d is the thickness of the film / m; A is the area of ​​the beaker mouth / m 2 ; t is the measurement time interval / s; ∆p is the vapor pressure difference between the inside and outside of the membrane / Pa; the results are shown in Table 2.

[0050] The tensile strength and elongation at break were determined by cutting the protein film into small pieces of 10 mm × 35 mm in width and using a texture analyzer to measure the tensile strength and elongation at break. The texture analyzer parameters were: interval 15 mm, tensile rate 30 mm / min. Tensile strength = F / S, where: F is the maximum tension at break of the film / N; S is the cross-sectional area of ​​the film / m 2 Elongation at break = E / 15, where E is the elongated length of the film when it breaks / mm; the results are shown in Table 3.

[0051] Table 2 Table 3 It can be concluded from Tables 2 and 3 that compared with the case without adding low acyl gellan gum and without homogenization combined with high pressure microfluidization treatment, the gelling temperature and melting temperature of the fish skin protein glue after adding low acyl gellan gum and homogenization combined with high pressure microfluidization treatment have been improved to a certain extent, and the performance of the prepared edible film is also better. The gelling temperature and melting temperature of Example 5 and the film performance of Example 8 are better than those of pig skin protein glue (Comparative Example 1), which can replace mammal protein glue in more scenarios.

[0052] The embodiments of the present application are described above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the core idea of ​​the present application, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present application and the claims, all of which are within the protection of the present application.

Claims

1. A method for preparing a fish skin protein glue edible film, characterized in that: The following steps are involved: Mixing the fish skin protein glue solution and the low acyl gellan gum solution to obtain a fish skin protein glue-low acyl gellan gum mixed solution; The fish skin protein glue-low acyl gellan gum mixed solution is subjected to a first homogenization treatment, a high-pressure microfluidization treatment and a spray drying treatment in sequence to obtain a fish skin protein glue mixture; Dissolving the fish skin protein glue mixture in water to obtain a fish skin protein glue mixed solution; Adding glycerol to the fish skin protein glue mixed solution and stirring to obtain a mixed solution; Performing ultrasonic defoaming treatment on the mixed solution to obtain a defoaming solution; The defoaming solution is placed in a mold, dried at a preset temperature and preset humidity, and demoulded to obtain the fish skin protein glue edible film.

2. The preparation method according to claim 1, characterized in that: The step of adding glycerol to the fish skin protein glue mixed solution and stirring to obtain a mixed solution specifically comprises: Glycerol and anthocyanidin are added to the fish skin protein glue mixed solution and stirred to obtain a mixed solution.

3. The preparation method according to claim 2, characterized in that: The mass ratio of the fish skin protein glue, the glycerol and the anthocyanin is 1:0.1:0.1 to 1:0.5:0.

3.

4. The preparation method according to claim 2, characterized in that: The anthocyanidin is black wolfberry anthocyanidin, and before the step of adding glycerol and anthocyanidin to the fish skin protein glue mixed solution and stirring to obtain the mixed solution, the preparation method further comprises: According to a preset material-liquid ratio, the pretreated black wolfberry is placed in an ethanol solution to obtain a mixed solution; The mixed solution is subjected to a second homogenization treatment and a high-voltage pulse electric field treatment in sequence, and then allowed to stand to obtain a supernatant; The supernatant is subjected to rotary evaporation drying to obtain the black wolfberry anthocyanin; The preset material-liquid ratio is: the usage ratio of the black wolfberry to the ethanol solution is 30g:1L to 50g:1L, and the concentration of the ethanol solution is 70% to 80%.

5. The preparation method according to claim 4, characterized in that: The treatment conditions in the second homogenization process are: pressure 10 MPa to 50 MPa, and treatment times 1 to 8 times; The treatment conditions during the high-voltage pulse electric field treatment are: electric field intensity of 30 kV / cm to 60 kV / cm, and pulse number of 4 to 8 times.

6. The preparation method according to claim 1, characterized in that: After placing the defoaming solution in a mold, drying at a preset temperature and preset humidity, and demolding, the preparation method further comprises: The demoulded protein glue is placed in a desiccator for storage to obtain the fish skin protein glue edible film.

7. The preparation method according to claim 1, characterized in that: The volume ratio of the fish skin protein glue solution to the low acyl gellan gum solution in the fish skin protein glue-low acyl gellan gum mixed solution is 99.5:0.5-80:

20.

8. The preparation method according to claim 7, characterized in that: The mass fraction of fish skin protein glue in the fish skin protein glue solution is 5% to 10%; The mass fraction of the low acyl gellan gum in the low acyl gellan gum solution is 1% to 3%.

9. The preparation method according to claim 8, characterized in that: The treatment conditions in the first homogenization process are: pressure 10 MPa to 50 MPa, and treatment times 1 to 8 times; The treatment conditions during the high-pressure microfluidic treatment are: pressure 50 MPa to 250 MPa, and treatment times 1 to 9 times; The treatment conditions during the spray drying process are: inlet air temperature 175°C~185°C, outlet air temperature 80°C~100°C.

10. An application of the fish skin protein glue edible film prepared by the preparation method according to any one of claims 2 to 6 in food packaging, characterized in that: The fish skin protein glue edible film can be used to analyze the freshness of food according to the pH value.

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