CN108586828A - A kind of edible compound fresh-keeping film and its preparation method and application - Google Patents

Abstract

The invention discloses an edible composite fresh-keeping film, a preparation method and application thereof. The composite film is obtained by adding polyvinyl alcohol solution, chitosan solution, phenolic acid substances, and plasticizers to the edible polysaccharide Curdlan suspension, and adjusting the pH value of the mixture to 3-5; ultrasonic degassing, Obtain the film-forming solution; pour the film-forming solution into a polytetrafluoroethylene plate, heat it at 90-120°C for 8-10 minutes, shape it and sterilize it, irradiate it with ultraviolet light for 5-10 minutes, and dry it with hot air circulation at 90-120°C for 30 minutes ‑60 minutes, after cooling at 4°C, an edible composite plastic wrap was obtained. The edible composite film prepared by the invention has high tensile strength and strong extensibility, and can still maintain good integrity, tensile strength and extensibility after boiling in boiling water for 1 hour. And it can effectively prolong the shelf life of fruits, vegetables and meat products.

Description

A kind of edible compound fresh-keeping film and its preparation method and application

technical field

The invention belongs to the field of food industry biotechnology, and relates to an edible composite fresh-keeping film with excellent mechanical properties, excellent water vapor barrier performance, antibacterial and anti-oxidation functions, a rapid preparation method thereof and its application in food.

Background technique

At present, based on petrochemical products such as polyethylene (PE), polyvinyl chloride (PVE), etc. as food packaging films, they have been widely used because of their low price, good physical properties and convenient use. However, these chemically synthesized packaging films are not easily biodegradable, and incineration will also produce harmful gases, which have already caused great harm to the environment. At the same time, plastic packaging films are not suitable for fried and other high-temperature ready-to-eat foods because they will decompose and produce harmful substances under high temperature conditions. Therefore, edible films made of natural non-toxic and biodegradable materials have gradually become a research hotspot.

Edible films are film products prepared from edible materials, such as sodium alginate, carrageenan, konjac gum, chitosan, whey protein, soybean protein, carboxymethyl cellulose, etc. At present, the application of edible film is not widely used and cannot replace the use of plastic, mainly because although the above-mentioned materials have good film-forming properties, they still cannot meet the requirements of practical application in terms of mechanical properties, water resistance, and stability. . Another very important point is that petrochemical products have the characteristics of rapid film formation, while the current film formation time of edible materials is too long, taking hours or even days, which is difficult to meet the requirements of industrialized rapid manufacturing.

Curdlan, the Chinese name can get ran gum, also known as curdlan polysaccharide, is a kind of polyglucose derived from microorganisms, which is composed of a single D glucose molecule at the C1 and C3 positions, connected by β-1,3 glycosidic bonds. Branched linear molecule, the degree of polymerization is between 135-455, insoluble in water. Curdlan has the unique property of forming a gel under heating conditions. Curdlan can form a reversible low-strength gel in the temperature range of 55°C-60°C, and will form an irreversible gel when the temperature rises above 80°C. high-elastic high-strength gel.

Due to its special physical and chemical properties, Curdlan has attracted widespread attention in the food field, and is now used as a coagulant, water-retaining agent, stabilizer, film-forming agent, etc. in noodle foods and frozen foods. Curdlan has excellent film-forming properties. After heating Curdlan polysaccharide solution, pour it into a mold and dry it to form a film, but the mechanical properties of pure Curdlan film are poor, so there are not many researches on Curdlan polysaccharide film at home and abroad. See. It has been reported in the literature that Curdlan/chitosan (Preparation and characterization of novel curdlan/chitosan blending membranes for antibacterial applications, Carbohydrate Polymers, 2011, 84:952-959) and konjac gum/Curdlan (Structural characterization and properties of konjac glucomannan/curdlan blend films , Carbohydrate Polymers, 2012, 89:497-503) blend film. These two films either have low tensile strength (TS) or poor elongation (EB), and the blending of polysaccharide and Curdlan and the preparation of the film take several hours. These problems limit the application of Curdlan-related membrane products.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art and develop an edible composite fresh-keeping film that uses Curdlan as the main matrix, has excellent mechanical properties, excellent barrier properties, and has antibacterial and antioxidative functions.

Another object of the present invention is to provide a rapid preparation method of the edible composite plastic wrap.

The purpose of the present invention can be achieved through the following technical solutions:

An edible composite fresh-keeping film, the film-forming liquid contains the following raw materials:

(a) Curdlan: content 5%-10%;

(b) chitosan: content 0.25%-0.5%;

(c) polyvinyl alcohol: content 1%-3%;

(d) Phenolic acids, one or more of ferulic acid, caffeic acid, chlorogenic acid, gallic acid, gallic acid, catechin, tannic acid, tea polyphenols, etc.: content 0.01%-0.05 %;

(e) Plasticizer, one or more in glycerin, sorbitol, polyethylene glycol: content 2-5%;

The above % means mass volume ratio g/100ml.

The edible composite plastic wrap of the present invention is prepared by the following method:

(1) Weigh the Curdlan powder, dissolve it in pure water, and after the Curdlan is fully swollen, under the action of a high-speed shear, prepare a 10-20g/100mL Curdlan suspension;

(2) Take chitosan powder, under the effect of magnetic stirrer, be dissolved in the lactic acid or acetic acid solution of 1-2% (V/V), prepare the chitosan solution of 1-2g/100mL;

(3) Weigh polyvinyl alcohol powder and dissolve it in pure water at 70-90°C under the action of a magnetic stirrer to prepare a polyvinyl alcohol solution of 4-12g/100mL;

(4) Curdlan suspension, chitosan solution, and polyvinyl alcohol solution are mixed under the effect of a magnetic stirrer according to the volume ratio of 2:1:1 to obtain a mixed solution;

(5) Add phenolic acids and plasticizers respectively, and adjust the pH to 3-5 with 1-3 mol/L of lactic acid, hydrochloric acid, acetic acid, phosphoric acid or citric acid to obtain a film-forming solution ; Wherein the amount of phenolic acid added is 10-50mg/100mL mixed solution, the added amount of plasticizer is 2-5g/100mL mixed solution;

(6) Ultrasonic degassing of the film-forming solution, poured into a polytetrafluoroethylene plate;

(7) 90-120°C setting for 8-10 minutes;

(8) UV irradiation treatment for 5-10 minutes;

(9) 90-120°C hot air circulation drying treatment for 30-60 minutes, and obtain an edible composite plastic wrap after cooling down at 4°C.

The preparation method of edible composite plastic wrap of the present invention comprises the following steps:

(1) Weigh Curdlan powder, dissolve it in pure water, and after Curdlan is fully swollen, under the action of high-speed shearing machine, prepare 10-20g/100mL Curdlan suspension;

(2) Take chitosan phenol powder, under the effect of magnetic stirrer, be dissolved in the lactic acid or acetic acid solution of 1-2% (V/V), prepare the chitosan solution of 1-2g/100mL;

(3) Weigh polyvinyl alcohol powder and dissolve it in pure water at 70-90°C under the action of a magnetic stirrer to prepare a polyvinyl alcohol solution of 4-12g/100mL;

(4) With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to 2:1:1 volume ratio, 3 kinds of solutions are blended to obtain mixed solution;

(5) Add phenolic acids and plasticizers respectively, and adjust the pH to 3-5 with 1-3 mol/L of lactic acid, hydrochloric acid, acetic acid, phosphoric acid or citric acid to obtain a film-forming solution ; Wherein the amount of phenolic acid added is 10-50mg/100mL mixed solution, the added amount of plasticizer is 2-5g/100mL mixed solution;

(6) Ultrasonic degassing of the film-forming solution, poured into a polytetrafluoroethylene plate;

(7) 90-120°C setting for 8-10 minutes;

(8) UV irradiation treatment for 5-10 minutes;

(9) 90-120°C hot air circulation drying treatment for 30-60 minutes, and obtain an edible composite plastic wrap after cooling down at 4°C.

The application of the edible composite fresh-keeping film of the invention in the fresh-keeping of fruits, vegetables and meat products.

The application of the edible composite fresh-keeping film of the present invention in food processing is preferably the application in the preparation of sausage casings.

The application of the edible composite fresh-keeping film-forming liquid in the fresh-keeping of fruits, vegetables and meat products.

Preferably, the edible composite fresh-keeping film-forming liquid is directly applied to the surface of fruits, vegetables and meat products.

Further preferably, the edible composite fresh-keeping film-forming liquid is directly applied to the surface of fruits, vegetables and meat products, and then treated with ultraviolet light for 5-10 minutes; and then subjected to 90-120°C hot air circulation drying treatment for 30-60 minutes.

Beneficial effect:

At present, the research on edible film at home and abroad is progressing rapidly. However, compared with chemically synthesized films, the problems of poor mechanical strength, poor water resistance, and poor stability of edible films still need to be solved urgently. In addition, the preparation time of edible films is generally several hours or even days, and the long film preparation time is also an important factor restricting the development and use of edible films.

A variety of edible materials can form a tight porous network structure by cross-linking the interaction between different molecules through appropriate proportions, which can improve the physical properties of the film. Curdlan is a kind of thermal gel, has excellent thermal stability and water insolubility, in the present invention, it is used as a reinforcing agent for film thermal stability and water vapor barrier performance; polyvinyl alcohol has a stable molecular structure and can endow the film with excellent mechanical properties. In the present invention, it is used as a film mechanical performance enhancer; chitosan has good antibacterial properties, and it is used as an antibacterial substance in the present invention; phenolic acids have antioxidant activity and antioxidant activity, and can improve the functionality of edible films. The edible composite film prepared by the present invention has a tensile strength (TS) of 16-18 MPa and an extensibility (EB) of 65.5-75.5%, and it still maintains good integrity, tensile strength and elongation after boiling in boiling water for 1 hour. sex. And it can effectively prolong the shelf life of fruits, vegetables and meat products.

The method for preparing the edible film provided by the invention significantly shortens the film-making time. Utilizing the Curdlan thermal gel properties, by controlling the film forming temperature (90-120°C) and pH (3-5), the setting of the film is completed within 10 minutes. One of the purposes of ultraviolet irradiation treatment is to play a bactericidal effect; the other is to induce phenolic acid to generate free radicals and graft chitosan to form a network structure, further strengthen the mechanical properties of the film, and induce the formation of chitosan grafted phenolic acid. The reaction endows the composite plastic wrap with higher antibacterial and antioxidant activity, and this step takes 5-10 minutes. Hot air circulation drying can quickly evaporate the water in the film, shorten the time of water removal to 30-60min, and obtain the final film product. Therefore, the shortest time for the entire film preparation is only 45 min. Compared with the hours or even days reported in the past, the film production time is significantly shortened, which effectively improves the production efficiency.

Detailed ways

Example 1: Preparation process of edible composite plastic wrap with different components, and film-making time comparison

(1) Preparation of Curdlan component film

① Weigh 12g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Curdlan suspension and pure water are blended according to the ratio (volume ratio) of 1:1, and the total volume of the blend is 100mL.

③Add 2.5g of glycerin, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

④ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate, and dry it naturally to obtain a film.

(2) Preparation of Curdlan/chitosan component film

① Weigh 12g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 2g of chitosan powder, dissolve it in 100mL of 2% lactic acid solution, and prepare a chitosan solution under the action of a magnetic stirrer;

③Curdlan suspension, chitosan solution, and pure water were blended under the action of a magnetic stirrer according to the ratio (volume ratio) of 2:1:1, and the total volume of the blend was 100 mL;

④Add 2.5g glycerin, adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑤ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate, and dry it naturally to obtain a film.

(3) Preparation of Curdlan/chitosan/PVA component film

① Weigh 12g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 2g of chitosan powder, dissolve it in 100mL of 2% lactic acid solution, and prepare a chitosan solution under the action of a magnetic stirrer;

③ Weigh 5g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 2.5g glycerin, adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate, and dry it naturally to obtain a film.

(4) Preparation of Curdlan/chitosan/PVA/phenolic acid component film

① Weigh 12g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 2g of chitosan powder, dissolve it in 100mL of 2% lactic acid solution, and prepare a chitosan solution under the action of a magnetic stirrer;

③ Weigh 5g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 10mg of tea polyphenols and 2.5g of glycerin respectively, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate, and dry it naturally to obtain a film.

(5) Preparation of Curdlan/chitosan/PVA/phenolic acid+90°C setting film

① Weigh 12g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 2g of chitosan powder, dissolve it in 100mL of 2% lactic acid solution, and prepare a chitosan solution under the action of a magnetic stirrer;

③ Weigh 5g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 10mg of tea polyphenols and 2.5g of glycerin respectively, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate;

⑦Set at 90°C for 10 minutes, and dry naturally to obtain a film.

(6) Preparation of Curdlan/chitosan/PVA/phenolic acid + 90°C setting + ultraviolet irradiation treatment film

① Weigh 12g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 2g of chitosan powder, dissolve it in 100mL of 2% lactic acid solution, and prepare a chitosan solution under the action of a magnetic stirrer;

③ Weigh 5g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 10mg of tea polyphenols and 2.5g of glycerin respectively, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate;

⑦90°C for 10 minutes;

⑧Ultraviolet irradiation treatment for 10 minutes, then dry naturally to obtain a film.

(7) Preparation of Curdlan/chitosan/PVA/phenolic acid + 90°C setting + ultraviolet irradiation treatment + hot air drying treatment film

① Weigh 12g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 2g of chitosan powder, dissolve it in 100mL of 2% lactic acid solution, and prepare a chitosan solution under the action of a magnetic stirrer;

③ Weigh 5g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 10mg of tea polyphenols and 2.5g of glycerin respectively, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate;

⑦90°C for 10 minutes;

⑧ UV irradiation treatment for 10 minutes;

⑨100°C hot air circulation drying treatment for 30 minutes, after cooling down at 4°C, a high-performance composite plastic wrap can be obtained.

The film-making time of edible composite film with different components and preparation conditions is shown in Table 1.

The film-making time of the edible preservative film of table 1 different components and preparation method

It can be seen that Curdlan/chitosan/PVA/phenolic acid components, and the film-forming time of the edible composite preservative film after ultraviolet irradiation and hot air drying are greatly shortened, only 0.75 hours, that is, 45 minutes. The mechanical performance indexes are the best.

Embodiment 2: the performance measurement of edible composite plastic wrap

(1) Mechanical properties

The film was cut into strips of 8cm*2cm, and fixed on a physical property analyzer for measurement. Set the initial distance between the two fixtures of the physical property meter to 80mm, and the speed to 0.8mm/sec. After the measurement, record the force (g) at the instant the film breaks and the distance L between the two clamps when the film breaks. For each sample, five parallel samples were taken for determination.

Tensile strength TS (g) is calculated according to the following formula:

TS=Fm/d*W

Where: TS—tensile strength, (MPa);

Fm—the maximum tension that the sample bears when it breaks, (N);

d—film thickness, (m);

W—film width, (m).

The elongation at break E (%) is calculated according to the following formula:

E=(L ₁ -L ₀ )/L ₀

In the formula: E—the elongation at break of the film (%);

L ₁ —the distance between the two clamps when the film is broken (mm);

L ₀ —the initial distance between the two fixtures (mm).

(2) Water resistance

water vapor transmission rate

Take a round open plastic cup with a diameter of 3cm and a depth of 4cm, add 3g of dry CaCl ₂ , cut a film sample with a diameter of 7cm, cover the mouth of the cup, and seal the interface between the film and the cup with paraffin. Each cup was then placed in a desiccator (21 °C, 75% relative humidity) with 1000 mL of distilled water added to the bottom. Weighing every 12h for 1 week. The amount of water vapor permeation is determined by the increase in cup weight. Calculate water vapor transmission rate (WVP) according to ASTM method (E96-93, 1993).

(3) thermal stability of composite plastic wrap

The prepared polysaccharide gel composite film was boiled in boiling water for 30 minutes, dried at 30°C for 12 hours, and the tensile strength, elongation, water vapor transmission rate and water absorption of the film were measured according to the above method.

According to the above method, the performance indexes of the composite membranes prepared with different components and conditions are shown in Table 2.

Table 2 Mechanical properties of edible plastic wrap with different components

It can be seen that Curdlan/chitosan/PVA/phenolic acid components, and the edible composite plastic wrap after ultraviolet irradiation and hot air drying have the best mechanical properties.

Embodiment 3: the antioxidant performance of edible composite plastic wrap

The antioxidant capacity of edible composite plastic wrap was expressed by measuring the scavenging capacity of DPPH. Cut the composite membrane into 20mm×20mm and put it into a beaker, add 100mL of distilled water, and stir on a magnetic stirrer at a speed of 150r/min and a temperature of 25±0.5°C. Sampling 1mL into a test tube at regular intervals, using 1mL of distilled water as a blank control, adding 4mL of DPPH methanol solution (150umol/L) to mix well, keeping it in the dark for 30min to fully react, and measuring the absorbance at 516nm with a UV spectrophotometer. DPPH free radical scavenging ability is calculated as follows:

DPPH free radical scavenging capacity=(1-A _sample )×100%/A _control

A _sample is the absorbance value of the sample, and A _control is the absorbance value of the blank.

The antioxidant capacity of the plastic wrap prepared with different components and conditions is shown in Table 3.

Table 3 Antioxidant performance of different components of edible plastic wrap

It can be seen that the composition of Curdlan/chitosan/PVA/phenolic acid, and the edible composite plastic wrap after ultraviolet irradiation and hot air drying have the best antioxidant performance.

Embodiment 4: the antibacterial performance of edible composite fresh-keeping film

The antibacterial ability of the composite film against Escherichia coli, Staphylococcus aureus, Bacillus and yeast was tested. Pour the culture medium (bacteria: beef extract peptone medium; yeast: PDA medium) added with 0.1mL indicator bacteria (bacteria concentration: 10 ⁵ ~ 10 ⁶ CFU/mL), and cool naturally for 30 minutes. Cut the composite plastic wrap into discs with a diameter of 1 cm, and place them on the surface of the medium plate. The plates were placed in an incubator and cultured for 24 hours (Escherichia coli, Staphylococcus aureus, Bacillus subtilis at 37°C; yeast at 28°C), and the diameter of the inhibition zone was measured.

The antibacterial activity of edible plastic wrap prepared with different components and conditions against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and yeast is shown in Table 4.

Table 4 Antibacterial performance of edible plastic wrap

It can be seen that the composition of Curdlan/chitosan/PVA/phenolic acid, and the edible composite plastic wrap after ultraviolet irradiation and hot air drying have the best antibacterial activity.

Embodiment 5: Fresh-keeping application of edible composite film fresh-keeping film to fruits and vegetables

Take the fresh-keeping effect of edible plastic wrap on strawberries as an example to illustrate.

strawberry treatment

Choose strawberries with the same size, color, uniform shape, and no defects and diseases to put into fresh-keeping boxes (10 pieces per fresh-keeping box). The control group is sealed with Curdlan single-component film, and the treatment group is sealed with composite plastic wrap. Then put it in a constant temperature and humidity box with RH50% and 21°C for 6 days, and measure the physiological and biochemical indexes every two days.

Determination of Physiological Indexes of Strawberry

The weight of strawberry fruit was weighed by electronic balance. The determination of SOD enzyme activity was carried out by kit (WST-1 method); the conductivity was determined by conductivity meter; the content of vitamin C was determined by 2,6-dichlorophenol-indophenol method; the organic acid was determined by acid-base titration method; Hardness was measured using GY-1 hand-held hardness tester, the unit is N (N; kg/cm ² )

Strawberry preservation effect

Table 5 shows the fresh-keeping effects of fresh-keeping films prepared with different components and conditions on strawberries stored for 6 days.

The fresh-keeping effect of table 5 edible plastic wrap to strawberry

From the various physiological and biochemical indicators of strawberries stored for 6 days in Table 5, it can be seen that Curdlan/chitosan/PVA/phenolic acid components, and the edible composite plastic wrap after ultraviolet irradiation and hot air drying, have a good effect on strawberry storage. Best for keeping fresh.

Embodiment 6: Fresh-keeping application of edible composite film fresh-keeping film to meat products

Take the fresh-keeping effect of edible plastic wrap on chilled meat as an example to illustrate.

chilled meat treatment

The chilled fresh meat was accurately weighed according to the measured standard, and randomly divided into six groups, five of which were wrapped with different composite films, the control group was wrapped with Curdlan single-component film, and the treatment group was wrapped with composite plastic wrap, and then Store in a refrigerator at a temperature of 4±0.5°C. The indicators were sampled every 2 days.

Total number of colonies in chilled meat

Refer to GB 4789.2-2010 National Food Safety Standard, Determination of the total number of colonies in food microbiology inspection.

Volatile Basic Nitrogen (TVB-N)

Refer to the semi-micro nitrogen determination method in GB/T 5009.44-2003.

Thiobarbituric Acid Reactants (TBARS)

Weigh 5g sample and add 15mL solution A (weigh 75.0g trichloroacetic acid, 1.0g EDTA and 1.0g propyl gallate, dilute to 1L with ddH ₂ O), homogenize and filter. Draw 5.0mL of the filtrate into a stoppered graduated test tube, add 5mL of B solution, mix well, react in boiling water at 100°C for 40min, and measure the absorbance. The MDA content was calculated against the malondialdehyde (MDA) standard curve, and the TBARS value was expressed as mg MDA/kg.

Determination of pH value

Refer to GB/T 9695.5-2008 "Meat and Meat Products pH Determination" for measurement.

Freshness preservation effect of chilled meat

Table 6 shows the fresh-keeping effect of edible plastic wraps prepared with different components and conditions on chilled meat stored for 6 days.

Table 6 The fresh-keeping effect of edible plastic wrap on chilled meat

From the quality indicators of the chilled meat stored for 6 days in Table 6, it can be seen that the Curdlan/chitosan/PVA/phenolic acid component, and the edible composite preservative film after ultraviolet irradiation and hot air drying, has a good effect on cooling. Meat storage and preservation effect is the best.

Example 7

① Weigh 10g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 1.5g chitosan powder, dissolve in 100mL of 2% lactic acid solution, and prepare chitosan solution under the action of magnetic stirrer;

③ Weigh 3g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 20mg of ferulic acid and 2.5g of glycerol respectively, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate;

⑦Set at 100°C for 8 minutes;

⑧ UV irradiation treatment for 10 minutes;

⑨100°C hot air circulation drying treatment for 30 minutes, after cooling down at 4°C, a high-performance composite plastic wrap can be obtained.

Example 8

① Weigh 20g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

② Weigh 3g of chitosan powder, dissolve in 100mL of 2% lactic acid solution, and prepare chitosan solution under the action of a magnetic stirrer;

③ Weigh 8.75g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 40mg of gallic acid and 5g of glycerin respectively, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate;

⑦120℃ for 8 minutes;

⑧ UV irradiation treatment for 10 minutes;

⑨120°C hot air circulation drying treatment for 30 minutes, after cooling down at 4°C, a high-performance composite plastic wrap can be obtained.

Example 9

① Weigh 15g of Curdlan powder, dissolve it in 100mL of pure water, and after Curdlan is fully swollen, prepare a suspension under the action of a high-speed shear;

②Weigh 2.5g chitosan powder, dissolve in 100mL of 2% lactic acid solution, and prepare chitosan solution under the action of magnetic stirrer;

③ Weigh 7g of polyvinyl alcohol powder, dissolve it in 100mL of 80°C pure water, and prepare a polyvinyl alcohol solution under the action of a magnetic stirrer;

4. With Curdlan suspension, chitosan solution, polyvinyl alcohol solution under the effect of magnetic stirrer, according to the ratio (volume ratio) of 2:1:1, three kinds of solutions are blended, and the total volume of blended liquid is 100mL;

⑤Add 40mg of chlorogenic acid and 3g of glycerol respectively, and adjust the pH to 4 with 1mol/L lactic acid solution to obtain a film-forming solution;

⑥ After ultrasonic degassing of the film-forming solution, pour 50ml into a 18cm*18cm polytetrafluoroethylene plate;

⑦90°C for 10 minutes;

⑧ UV irradiation treatment for 10 minutes;

⑨100°C hot air circulation drying treatment for 30 minutes, after cooling down at 4°C, a high-performance composite plastic wrap can be obtained.

Claims (9)

1. a kind of Compound Edible Coating for Preservation, it is characterised in that in film liquid contain following raw material：

(a)Curdlan：Content 5%-10%；

(b) chitosan：Content 0.25%-0.5%；

(c) polyvinyl alcohol:Content 1%-3%；

(d) phenolic acid, ferulic acid, caffeic acid, chlorogenic acid, gallic acid, gallic acid, catechin, tannic acid, tea polyphenols It is one or more in：Content 0.01%-0.05%；

(e) plasticizer, it is one or more in glycerine, sorbierite, polyethylene glycol：Content 2-5%；

The above % indicates mass volume ratio g/100ml.

2. Compound Edible Coating for Preservation according to claim 1 or 2, it is characterised in that be prepared by the following method to obtain：

(1) it weighs Curdlan powder, in molten pure water, after Curdlan is fully swollen, under high-speed shearing machine effect, prepares The Curdlan suspensions of 10-20g/100mL；

(2) Chitosan powder is weighed, under the action of magnetic stirring apparatus, is dissolved in the lactic acid or acetic acid solution of 1-2% (V/V), is made It is standby go out 1-2g/100mL shitosan lysate；

(3) polyvinyl alcohol powder is weighed, under the action of magnetic stirring apparatus, is dissolved in 70-90 DEG C of pure water, prepares 4-12g/ The poly-vinyl alcohol solution of 100mL；

(4) by Curdlan suspensions, shitosan lysate, poly-vinyl alcohol solution under the action of magnetic stirring apparatus, according to 2:1: 1 volume ratio mixes three kinds of solution, obtains mixed solution；

(5) it is separately added into phenolic acid, plasticizer, in the lactic acid of 1-3mol/L, hydrochloric acid, acetic acid, phosphoric acid or citric acid One or more acid solutions adjust pH to 3-5 and obtain edibility composite fresh-keeping into film liquid；Wherein phenolic acid addition is 10- 50mg/100mL mixed solutions, plasticizer addition are 2-5g/100mL mixed solutions；

(6) it deaerates at film liquid ultrasound, pours into polyfluortetraethylene plate；

(7) it shapes 8-10 minutes for 90-120 DEG C；

(8) ultraviolet treatment with irradiation 5-10 minutes；

(9) 90-120 DEG C of hot air circulation is dried 30-60 minutes, and Compound Edible Coating for Preservation is obtained after 4 DEG C of coolings.

3. the preparation method of Compound Edible Coating for Preservation described in claim 1, it is characterised in that comprise the steps of：

(1) Curdlan powder is weighed, is dissolved in pure water, after Curdlan is fully swollen, under high-speed shearing machine effect, is prepared The Curdlan suspensions of 10-20g/100mL；

(2) chitosan phenol powder is weighed, under the action of magnetic stirring apparatus, is dissolved in the lactic acid or acetic acid solution of 1-2% (V/V), Prepare the shitosan lysate of 1-2g/100mL；

(3) pva powder is weighed, under the action of magnetic stirring apparatus, is dissolved in 70-90 DEG C of pure water, prepares 4-12g/ The poly-vinyl alcohol solution of 100mL；

(4) by Curdlan suspensions, shitosan lysate, poly-vinyl alcohol solution under the action of magnetic stirring apparatus, according to 2:1: 3 kinds of solution blendings are obtained mixed solution by 1 volume ratio；

(5) it is separately added into phenolic acid, plasticizer, in the lactic acid of 1-3mol/L, hydrochloric acid, acetic acid, phosphoric acid or citric acid One or more acid solutions adjust pH to 3-5 and obtain into film liquid；Wherein phenolic acid addition mixes for 10-50mg/100mL Solution, plasticizer addition are 2-5g/100mL mixed solutions；

(6) it deaerates at film liquid ultrasound, pours into polyfluortetraethylene plate；

(7) it shapes 8-10 minutes for 90-120 DEG C；

(8) ultraviolet treatment with irradiation 5-10 minutes；

(9) 90-120 DEG C of hot air circulation is dried 30-60 minutes, and Compound Edible Coating for Preservation is obtained after 4 DEG C of coolings.

4. application of the Compound Edible Coating for Preservation as claimed in claim 1 or 2 in fruits and vegetables, food preservation.

5. application of the Compound Edible Coating for Preservation as claimed in claim 1 or 2 in terms of food processing.

6. application according to claim 5, it is characterised in that Compound Edible Coating for Preservation as claimed in claim 1 or 2 exists Prepare the application in terms of casing.

7. application of the edibility composite fresh-keeping at film liquid in fruits and vegetables, food preservation described in claim 2.

8. application according to claim 7, it is characterised in that edibility composite fresh-keeping is directly applied to fruits and vegetables, meat at film liquid Product surface.

9. application according to claim 8, it is characterised in that edibility composite fresh-keeping is directly applied to fruits and vegetables, meat at film liquid Ultraviolet treatment with irradiation 5-10 minutes after product surface；It is dried 30-60 minutes through 90-120 DEG C of hot air circulation again.