CN110172169B

CN110172169B - Preparation method of food packaging film

Info

Publication number: CN110172169B
Application number: CN201910480053.0A
Authority: CN
Inventors: 吕庆云; 常锦玉
Original assignee: Wuhan Polytechnic University
Current assignee: Wuhan Polytechnic University
Priority date: 2019-06-03
Filing date: 2019-06-03
Publication date: 2021-05-14
Anticipated expiration: 2039-06-03
Also published as: CN110172169A

Abstract

The invention discloses a preparation method of a food packaging film, and relates to the technical field of food packaging. The preparation method of the food packaging film comprises the following steps: mixing highland barley bran with water, and sterilizing to obtain bran mixed solution; inoculating a bacteria liquid of aureobasidium pullulans into the bran mixed liquid, and culturing to obtain a fermentation liquid; centrifuging the fermentation liquor, collecting supernatant, adding ethanol into the supernatant to generate precipitate, and collecting the precipitate; purifying the precipitate, and drying to obtain polysaccharide extract; dissolving the polysaccharide extract in water, adding glycerol, uniformly stirring to prepare a membrane casting solution, and paving and baking the membrane casting solution to obtain the food packaging membrane. The invention aims to prepare a food packaging film which has the advantages of good mechanical property and barrier property.

Description

Preparation method of food packaging film

Technical Field

The invention relates to the technical field of food packaging, in particular to a preparation method of a food packaging film.

Background

The traditional food packaging film is mainly made of synthetic plastics such as polyethylene, polypropylene and the like, but the synthetic plastics are increasingly exposed to the characteristics of non-degradability, non-regeneration, influence on food safety and the like, cause serious pollution to the environment and increase the additional investment of pollution discharge treatment. With the improvement of the consciousness and the shape of people, consumers pursue more environment-friendly, safe, green and organic food packaging materials, and edible food packaging films become hot spots of current research.

At present, the most popular food packaging film is prepared from natural macromolecules, and has the characteristics of edibility, biodegradability, good appearance, certain barrier and barrier properties, no toxicity, no pollution, low cost and the like.

In addition, the highland barley has the nutritional ingredient composition of three high, two low, namely the characteristics of high protein, high dietary fiber, high vitamin, low fat, low sugar and the like, and is widely applied to the fields of food, feed, brewing, medical treatment and the like. With the rise of the highland barley processing industry, the byproducts of the highland barley products are correspondingly increased, the highland barley bran processed by the highland barley is rich in various nutrient components, but the highland barley bran is mostly used for preparing the feed and cannot exert the maximum value.

Disclosure of Invention

The invention mainly aims to provide a preparation method of a food packaging film, and aims to prepare the food packaging film which has the advantages of good mechanical property and barrier property.

In order to achieve the above object, the present invention provides a method for preparing a food packaging film, comprising the steps of:

mixing highland barley bran with water, and sterilizing to obtain bran mixed solution;

inoculating a bacteria liquid of aureobasidium pullulans into the bran mixed liquid, and culturing to obtain a fermentation liquid;

centrifuging the fermentation liquor, collecting supernatant, adding ethanol into the supernatant to generate precipitate, and collecting the precipitate;

purifying the precipitate, and drying to obtain polysaccharide extract;

dissolving the polysaccharide extract in water, adding glycerol, uniformly stirring to prepare a membrane casting solution, and paving and baking the membrane casting solution to obtain the food packaging membrane.

Optionally, in the step of inoculating the fungus liquid of aureobasidium pullulans to the bran mixed liquid and culturing to obtain the fermentation liquid,

the inoculation amount is 2-4 (v/v)%; and/or the presence of a gas in the gas,

the culture time is 2-5 days.

Optionally, the step of inoculating the fungus liquid of aureobasidium pullulans to the bran mixed liquid, and the step of culturing to obtain the fermentation liquid further includes:

carrying out mutagenesis breeding on the aureobasidium pullulans to obtain a mutagenized strain which does not produce melanin;

and inoculating the mutagenic strain into a liquid culture medium, and culturing for 24-36 h to obtain a bacterial liquid of the aureobasidium pullulans.

Optionally, the step of performing mutagenesis and breeding on the aureobasidium pullulans to obtain a mutagenized strain which does not produce melanin comprises:

preparing the aureobasidium pullulans into a bacterial suspension;

carrying out ultraviolet irradiation on the bacterial suspension for 5-10 s under the conditions of aseptic environment and stirring;

and inoculating the bacterial suspension subjected to ultraviolet irradiation to a PDA culture medium for culturing for 3-5 days to obtain the mutagenic strain incapable of producing melanin.

Optionally, in the step of inoculating the mutagenic strain to a liquid culture medium, and culturing for 24-36 hours to obtain a bacterial liquid of aureobasidium pullulans, the liquid culture medium comprises, in parts by weight: 30-50 parts of sucrose, 3-6 parts of dipotassium phosphate, 0.5-2 parts of sodium chloride, 0.1-0.5 part of magnesium sulfate heptahydrate, 0.3-1 part of ammonium sulfate, 2-5 parts of yeast extract and 800-1500 parts of distilled water.

Optionally, the step of sterilizing the mixture of the highland barley bran and the water to obtain a bran mixture comprises:

crushing highland barley bran, and sieving with a 100-200 mesh sieve to obtain highland barley bran powder;

taking 2-5 parts of highland barley bran powder, and adding 40-100 parts of deionized water to prepare a suspension;

and adjusting the pH of the suspension to 5-6.5, and then sterilizing at 120-125 ℃ to obtain a bran mixed solution.

Optionally, the step of centrifuging the fermentation broth, collecting the supernatant and adding ethanol to the supernatant to precipitate, the step of collecting the precipitate comprising:

centrifuging the fermentation liquor, and collecting supernatant;

and adding ethanol into the supernatant, placing the supernatant in an environment at 0-4 ℃ for 10-15 hours, and collecting the precipitate.

Optionally, in the step of drying the polysaccharide extract after the purification treatment of the precipitate, the purification treatment comprises the following steps: starch removal, protein removal, and small molecule salt removal.

Optionally, after dissolving the polysaccharide extract in water, adding glycerol and stirring uniformly to prepare a membrane casting solution, spreading and drying the membrane casting solution to obtain the food packaging membrane,

the mass ratio of the polysaccharide extract to the glycerol is (0.1-0.4): (0.06-0.1); and/or the presence of a gas in the gas,

the baking temperature is 30-50 ℃.

In the technical scheme of the invention, the highland barley bran is fermented by using aureobasidium pullulans, and because the highland barley bran is rich in beta-glucan and other polysaccharides with high nutritive value, the beta-glucan has swelling property, certain water holding capacity and gel property, and can improve the mechanical property of the membrane; meanwhile, the aureobasidium pullulans can secrete a water-soluble extracellular polysaccharide-pullulan when highland barley bran is fermented, and the pullulan can improve the film forming property of the film so that the film has good barrier property. The product of highland barley bran fermented by aureobasidium pullulans has the nutrients contained in beta-glucan, pullulan and other highland barley bran, so that the prepared food packaging film has good mechanical property and barrier property, is healthy and safe, and is suitable for market popularization.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic flow chart of an embodiment of a method for preparing a food packaging film according to the present invention;

fig. 2 is a schematic flow chart of another embodiment of the method for preparing the food packaging film according to the present invention.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

It should be noted that the meaning of "and/or" appearing throughout includes three parallel schemes, such as "a and/or B" includes scheme a, or scheme B, or schemes where both a and B are satisfied. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

In view of this, the present invention proposes a method of producing a food packaging film, by which a food packaging film can be produced, which can be used as food packaging, has good mechanical properties and barrier properties, and is healthy and safe. In conjunction with the schematic flow chart of an embodiment of the method for preparing a food packaging film shown in fig. 1, the method for preparing a food packaging film comprises the following steps:

step S30, mixing highland barley bran with water, and sterilizing to obtain bran mixed solution.

Wherein the highland barley bran is preferably white highland barley bran.

The highland barley is rich in beta-glucan, is the crop with the highest beta-glucan content in wheat crops in the world, and has the average content of 5 percent. However, the research shows that the beta-glucan in the highland barley is mainly enriched in bran and mainly distributed in the aleurone layer cell wall, and the content of the beta-glucan in the highland barley aleurone layer cell wall is about 26 percent. The beta-glucan has swelling property, certain water holding capacity and gel property, and can improve the mechanical property of the film, so that the film has good tensile strength, elongation at break and sealing strength. In addition, the highland barley bran also contains other polysaccharides and trace elements, and the highland barley bran is used as a substrate to be fermented to prepare the polysaccharide extract rich in beta-glucan and other nutrient substances.

In a specific implementation, step S30 may include:

step S310, crushing the highland barley bran, and sieving the crushed highland barley bran with a 100-200-mesh sieve to obtain highland barley bran powder;

step S320, taking 2-5 parts of highland barley bran powder, and adding 40-100 parts of deionized water to prepare suspension;

and S330, adjusting the pH of the suspension to 5-6.5, and then sterilizing at 120-125 ℃ to obtain a bran mixed solution.

And step S40, inoculating the aureobasidium pullulans bacterial liquid into the bran mixed liquid, and culturing to obtain fermentation liquid.

The Aureobasidium pullulans can secrete a water-soluble extracellular polysaccharide-pullulan during fermentation, the pullulan belongs to amorphous viscous substances, maltotriose is used as a basic unit in the structure of the pullulan, alpha-1, 6 glycosidic bonds are used for connection, and the unique linkage mode endows a membrane made of the pullulan with good membrane forming property: high water solubility, no color or odor, transparency, flexibility, oil resistance, and oxygen resistance.

In this embodiment, a bacterial liquid of aureobasidium pullulans is inoculated into the mixed bran liquid, and the fermentation liquid is obtained by culturing.

By using highland barley bran as a substrate and adopting aureobasidium pullulans for fermenting the highland barley bran, beta-glucan in the highland barley bran can be extracted while pullulan is prepared, and the prepared food packaging film has the advantages of forming films of the highland barley bran and the pullulan and can make up for defects of the highland barley bran when the highland barley bran and the pullulan are formed films of the highland barley bran mutually: the composite packaging film is colorless, tasteless, transparent, oil-resistant, oxygen-resistant, heat-sealable, strong in tensile strength and flexibility, so that the preservation period of food can be prolonged when the food is preserved; and the better solubility of the compound also makes the compound more suitable for packaging foods such as instant noodle oil or powder; meanwhile, a new application approach is opened up for the highland barley bran, the highland barley utilization degree is improved, and the highland barley is further promoted.

Wherein, when inoculation is carried out, the inoculation amount of the bacterial liquid is 2-4 (v/v)%, namely the volume of the inoculated bacterial liquid is 2-4 (v/v)% of the volume of the bran mixed liquid; the culture time after inoculation is 2-5 days. Wherein one day is 24 hours, and 2-5 days are 48-120 hours.

In addition, the bacterial solution of aureobasidium pullulans can be prepared by a conventional method, i.e., the bacterial solution is prepared by activating and culturing the strain of aureobasidium pullulans, and the specific steps thereof are not described in detail. In this example, the aureobasidium pullulans was purchased from Guangdong strain collection center.

And step S50, centrifuging the fermentation liquor, collecting supernatant, adding ethanol into the supernatant to generate precipitate, and collecting the precipitate.

In specific implementation, the method can comprise the following steps:

step S510, centrifuging the fermentation liquor, and collecting supernatant;

and S520, adding ethanol at 0-4 ℃ into the supernatant, placing the supernatant in an environment at 0-4 ℃ for 10-15 hours, and collecting precipitates.

And step S60, drying the precipitate after purification treatment to obtain polysaccharide extract.

Wherein the purification treatment comprises the following steps: starch removal, protein removal, and small molecule salt removal. Wherein, there is no sequence in the processes of starch removal, protein removal and micromolecule salt removal, various conventional impurity removal methods can be adopted, and various methods such as enzymolysis, alcohol precipitation or dialysis can be adopted for starch removal.

In this embodiment, the removing starch may include the following steps:

step S611, adding a calcium nitrate solution with the mass fraction of 60-70% into the precipitate to obtain a suspension;

and S612, placing the suspension in a boiling water bath for 5-15 min, centrifuging at the rotating speed of 3500-4500 r/min for 10-15 min, and collecting supernatant to obtain the concentrated solution with starch removed.

The removal of the protein may comprise the steps of:

step S621, adding chloroform and n-butanol into the concentrated solution with starch removed, oscillating for 20-40 min, standing for 10-15 min, and centrifuging to obtain a supernatant;

and S622, repeating the step S6213-5 times on the supernate to obtain the concentrated solution with the protein removed.

Wherein the volume ratio of the chloroform to the n-butanol to the concentrated solution without starch is (4-5) to 1 (25-30).

The method for removing the small molecule salt comprises the following steps:

and S630, dissolving the precipitate in water, putting the precipitate into a dialysis bag with the cut-off molecular weight of 12000-15000 for dialysis treatment for 24-48 h, and collecting the cut-off solution to obtain the concentrated solution with the small molecular salt removed.

Further, step S630 may be performed after removing starch, i.e.: and (3) putting the concentrated solution without the starch into a dialysis bag with the cut-off molecular weight of 12000-15000 for dialysis treatment for 24-48 h, and collecting the cut-off solution to obtain the concentrated solution without small molecular salt.

And step S70, dissolving the polysaccharide extract in water, adding glycerol, uniformly stirring to prepare membrane casting solution, and paving and drying the membrane casting solution to obtain the food packaging membrane.

In the embodiment, the mass ratio of the polysaccharide extract to the glycerol is (0.1-0.4): (0.06-0.1); the baking temperature is 30-50 ℃.

Specifically, 0.1-0.4 part of polysaccharide extract is dissolved in 15-30 parts of water, 0.06-0.1 part of glycerol is added, and after uniform stirring, defoaming treatment is carried out to prepare a membrane casting solution; and pouring the casting solution into a mold, and drying in an oven at 30-50 ℃ to form a film, thus obtaining the food packaging film.

In addition, the fungus liquid of the aureobasidium pullulans in step S40 can also be a fungus liquid of an aureobasidium pullulans mutant strain, so that a colorless food packaging film with better transparency can be prepared. That is, the aureobasidium pullulans is bred to obtain a more excellent strain and then the strain is prepared into a bacterial liquid, and then the step S40 is performed.

In another embodiment of the present invention, in combination with the schematic flow chart of another embodiment of the preparation method of the present invention shown in fig. 2, the following steps S10 and S20 are further included before step S40:

step S10, carrying out mutation breeding on the aureobasidium pullulans to obtain a mutation strain which does not produce melanin.

The strain is mutagenized to select a desired excellent strain, and in this example, Aureobasidium pullulans is mutagenized to select an excellent mutagenized strain without producing a pigment. Thus, a colorless and transparent food packaging film can be obtained by orientation. In addition, the mutation breeding mode has a plurality of modes, breeding can be realized by irradiating various rays or microwave radiation, and mutation can be promoted by adding a mutagen.

In view of simplifying the operation steps and reducing the cost, in one embodiment of the present invention, step S10 is implemented as follows:

step S110, preparing aureobasidium pullulans into a bacterial suspension;

and S120, carrying out ultraviolet irradiation on the bacterial suspension for 5-10S in a sterile environment under a stirring condition.

The stirring method may be mechanical stirring, shaking table oscillation, etc., and in this embodiment, a magnetic stirring method is preferred.

And S130, inoculating the bacterial suspension subjected to ultraviolet irradiation to a PDA (potato dextrose agar) culture medium to be cultured for 3-5 days to obtain the mutagenic strain which does not produce melanin.

And step S20, inoculating the mutagenic strain and culturing to obtain a bacterial liquid of the aureobasidium pullulans.

When performing step S20, the following steps may be included:

inoculating the mutagenic strain into a liquid culture medium, and culturing for 24-36 h to obtain a bacterial liquid of aureobasidium pullulans;

wherein the liquid culture medium comprises the following components in parts by weight: 30-50 parts of sucrose, 3-6 parts of dipotassium phosphate, 0.5-2 parts of sodium chloride, 0.1-0.5 part of magnesium sulfate heptahydrate, 0.3-1 part of ammonium sulfate, 2-5 parts of yeast extract and 800-1500 parts of distilled water.

It should be noted that steps S10, S20 and S30 are not in the same order, and may be performed before, after or simultaneously with step S30, and in fig. 2, steps S10, S20 and S30 are taken as an example.

The technical solutions of the present invention are further described in detail below with reference to specific examples and drawings, it should be understood that the following examples are merely illustrative of the present invention and are not intended to limit the present invention.

Example 1

Pulverizing highland barley bran, and sieving with 100 mesh sieve to obtain highland barley bran powder; taking 2g of highland barley bran powder, adding 40g of deionized water to prepare a suspension, adjusting the pH of the suspension to 5, and sterilizing at 120 ℃ to obtain a bran mixed solution for later use.

Inoculating 2% of the volume of the wheat bran mixed solution into the bacteria solution of the aureobasidium pullulans to the wheat bran mixed solution, and culturing for 2d in a constant-temperature incubator at 37 ℃ to obtain a fermentation liquid; and centrifuging the fermentation liquor, collecting supernatant, adding 0-4 ℃ ethanol into the supernatant, placing the supernatant in an environment of 0-4 ℃ for 10 hours, and collecting precipitates.

Adding a calcium nitrate solution with the mass fraction of 60-70% into the precipitate, placing the precipitate in a boiling water bath for 10min, centrifuging the precipitate at the rotating speed of 4000r/min for 10min, and collecting supernatant to obtain concentrated solution from which starch is removed; adding chloroform and n-butanol into the concentrated solution, shaking for 30min, standing for 10min, centrifuging, collecting supernatant, and repeatedly precipitating for 5 times to remove protein to obtain concentrated solution; putting the concentrated solution without the protein into a dialysis bag with the molecular weight cutoff of 14000 for dialysis treatment for 48 hours, and collecting the trapped solution to obtain concentrated solution without micromolecular salt; freeze-drying the concentrated solution with small molecular salt removed to obtain polysaccharide extract.

Dissolving 0.1g of polysaccharide extract in water, adding 0.06g of glycerol, stirring uniformly, and defoaming to prepare a membrane casting solution; pouring the casting solution into a mold, and drying in an oven at 30 ℃ to form a film, thus obtaining the food packaging film.

Example 2

Pulverizing highland barley bran, and sieving with 200 mesh sieve to obtain highland barley bran powder; taking 3g of highland barley bran powder, adding 80g of deionized water to prepare a suspension, adjusting the pH of the suspension to 5.5, and sterilizing at 121 ℃ to obtain a bran mixed solution for later use.

Inoculating 3% of the volume of the wheat bran mixed solution into the bacteria solution of the aureobasidium pullulans, and culturing in a constant-temperature incubator at 37 ℃ for 3d to obtain a fermentation liquid; and centrifuging the fermentation liquor, collecting supernatant, adding 0-4 ℃ ethanol into the supernatant, placing the supernatant in an environment of 0-4 ℃ for 12 hours, and collecting precipitates.

Adding a calcium nitrate solution with the mass fraction of 60-70% into the precipitate, placing the precipitate in a boiling water bath for 15min, centrifuging the precipitate for 15min at the rotating speed of 3500-4500 r/min, and collecting supernatant to obtain concentrated solution with starch removed; adding chloroform and n-butanol into the concentrated solution, shaking for 20min, standing for 12min, centrifuging to obtain supernatant, and repeating the precipitation for 5 times to remove protein to obtain concentrated solution; putting the concentrated solution without the protein into a dialysis bag with the molecular weight cutoff of 14000 for dialysis treatment for 48 hours, and collecting the trapped solution to obtain concentrated solution without micromolecular salt; freeze-drying the concentrated solution with small molecular salt removed to obtain polysaccharide extract.

Dissolving 0.2g of polysaccharide extract in water, adding 0.07g of glycerol, stirring uniformly, and defoaming to prepare a membrane casting solution; pouring the casting solution into a mold, and drying in a 35 ℃ oven to form a film, thus obtaining the food packaging film.

Example 3

Pulverizing highland barley bran, and sieving with 100 mesh sieve to obtain highland barley bran powder; taking 5g of highland barley bran powder, adding 100g of deionized water to prepare a suspension, adjusting the pH of the suspension to 6, and sterilizing at 121 ℃ to obtain a bran mixed solution for later use.

Inoculating 2.8% of the volume of the wheat bran mixed solution into the bacteria solution of the aureobasidium pullulans, and culturing in a constant-temperature incubator at 37 ℃ for 4d to obtain a fermentation liquid; and centrifuging the fermentation liquor, collecting supernatant, adding 0-4 ℃ ethanol into the supernatant, placing the supernatant in an environment of 0-4 ℃ for 14 hours, and collecting precipitates.

Adding a calcium nitrate solution with the mass fraction of 60-70% into the precipitate, placing the precipitate in a boiling water bath for 5min, centrifuging the precipitate at the rotating speed of 3500r/min for 10min, and collecting supernatant to obtain concentrated solution from which starch is removed; adding chloroform and n-butanol into the concentrated solution, shaking for 40min, standing for 15min, centrifuging, collecting supernatant, and repeatedly precipitating for 5 times to remove protein to obtain concentrated solution; putting the concentrated solution without the protein into a dialysis bag with the molecular weight cutoff of 14000 for dialysis treatment for 48 hours, and collecting the trapped solution to obtain concentrated solution without micromolecular salt; freeze-drying the concentrated solution with small molecular salt removed to obtain polysaccharide extract.

Dissolving 0.3g of polysaccharide extract in water, adding 0.08g of glycerol, uniformly stirring, and defoaming to prepare a membrane casting solution; pouring the casting solution into a mold, and drying in a drying oven at 40 ℃ to form a film, thus obtaining the food packaging film.

Example 4

Pulverizing highland barley bran, and sieving with 120 mesh sieve to obtain highland barley bran powder; taking 4g of highland barley bran powder, adding 60g of deionized water to prepare a suspension, adjusting the pH of the suspension to 6.5, and sterilizing at 125 ℃ to obtain a bran mixed solution for later use.

Inoculating the fungus liquid of the aureobasidium pullulans to the bran mixed liquid with the volume of 4 percent of that of the bran mixed liquid, and culturing for 5d in a constant-temperature incubator at 37 ℃ to obtain fermentation liquid; and centrifuging the fermentation liquor, collecting supernatant, adding 0-4 ℃ ethanol into the supernatant, placing the supernatant in an environment of 0-4 ℃ for 15 hours, and collecting precipitates.

Adding a calcium nitrate solution with the mass fraction of 60-70% into the precipitate, placing the precipitate in a boiling water bath for 12min, centrifuging the precipitate at the rotating speed of 3800r/min for 10min, and collecting supernatant to obtain concentrated solution with starch removed; adding chloroform and n-butanol into the concentrated solution, shaking for 30min, standing for 13min, centrifuging, collecting supernatant, and repeatedly precipitating for 5 times to remove protein to obtain concentrated solution; putting the concentrated solution without the protein into a dialysis bag with the molecular weight cutoff of 14000 for dialysis treatment for 48 hours, and collecting the trapped solution to obtain concentrated solution without micromolecular salt; freeze-drying the concentrated solution with small molecular salt removed to obtain polysaccharide extract.

Dissolving 0.4g of polysaccharide extract in water, adding 0.1g of glycerol, stirring uniformly, and defoaming to prepare a membrane casting solution; pouring the casting solution into a mold, and drying in a 50 ℃ oven to form a film, thus obtaining the food packaging film.

Example 5

Preparing aureobasidium pullulans into a bacterial suspension, carrying out ultraviolet irradiation on the bacterial suspension for 5s under the conditions of sterile environment and stirring, then inoculating the bacterial suspension onto a PDA culture medium for culturing for 4 days to obtain a mutagenized strain which does not produce melanin, inoculating the mutagenized strain into a liquid culture medium, and culturing for 24h to obtain a bacterial liquid of the aureobasidium pullulans for later use. Wherein, the components of the liquid culture medium comprise: 30g of sucrose, 6g of dipotassium phosphate, 0.5g of sodium chloride, 0.3g of magnesium sulfate heptahydrate, 1g of ammonium sulfate, 2g of yeast extract and 800g of distilled water.

Example 6

Preparing aureobasidium pullulans into a bacterial suspension, carrying out ultraviolet irradiation on the bacterial suspension for 8s under the conditions of aseptic environment and stirring, then inoculating the bacterial suspension onto a PDA culture medium for culturing for 3 days to obtain a mutagenized strain which does not produce melanin, inoculating the mutagenized strain into a liquid culture medium, and culturing for 30h to obtain a bacterial liquid of the aureobasidium pullulans for later use. Wherein, the components of the liquid culture medium comprise: 40g of sucrose, 3g of dipotassium phosphate, 1.5g of sodium chloride, 0.1g of magnesium sulfate heptahydrate, 0.8g of ammonium sulfate, 5g of yeast extract and 1500g of distilled water.

Inoculating the fungus liquid of the aureobasidium pullulans to the mixed bran liquid with the volume of 3.8 percent of that of the mixed bran liquid, and culturing in a constant-temperature incubator at 37 ℃ for 3.5d to obtain fermentation liquid; and centrifuging the fermentation liquor, collecting supernatant, adding 0-4 ℃ ethanol into the supernatant, placing the supernatant in an environment of 0-4 ℃ for 13 hours, and collecting precipitates.

Dissolving 0.3g of polysaccharide extract in water, adding 0.07g of glycerol, stirring uniformly, and defoaming to prepare a membrane casting solution; pouring the casting solution into a mold, and drying in a drying oven at 32 ℃ to form a film, thus obtaining the food packaging film.

Example 7

Preparing aureobasidium pullulans into a bacterial suspension, carrying out ultraviolet irradiation on the bacterial suspension for 7s under the conditions of aseptic environment and stirring, then inoculating the bacterial suspension onto a PDA culture medium for culturing for 4.5 days to obtain a mutagenic strain which does not produce melanin, inoculating the mutagenic strain into a liquid culture medium, and culturing for 36h to obtain a bacterial liquid of the aureobasidium pullulans for later use. Wherein, the components of the liquid culture medium comprise: 35g of sucrose, 4g of dipotassium phosphate, 2g of sodium chloride, 0.5g of magnesium sulfate heptahydrate, 0.3g of ammonium sulfate, 4g of yeast extract and 1200g of distilled water.

Dissolving 0.2g of polysaccharide extract in water, adding 0.08g of glycerol, uniformly stirring, and defoaming to prepare a membrane casting solution; pouring the casting solution into a mold, and drying in a drying oven at 40 ℃ to form a film, thus obtaining the food packaging film.

Example 8

Preparing aureobasidium pullulans into a bacterial suspension, carrying out ultraviolet irradiation on the bacterial suspension for 10s under the conditions of aseptic environment and stirring, then inoculating the bacterial suspension onto a PDA culture medium for culturing for 5 days to obtain a mutagenized strain which does not produce melanin, inoculating the mutagenized strain into a liquid culture medium, and culturing for 32h to obtain a bacterial liquid of the aureobasidium pullulans for later use. Wherein, the components of the liquid culture medium comprise: 50g of sucrose, 5g of dipotassium phosphate, 1g of sodium chloride, 0.2g of magnesium sulfate heptahydrate, 0.6g of ammonium sulfate, 3g of yeast extract and 1000g of distilled water.

Pulverizing highland barley bran, and sieving with 160 mesh sieve to obtain highland barley bran powder; taking 4.5g of highland barley bran powder, adding 70g of deionized water to prepare a suspension, adjusting the pH of the suspension to 6.5, and sterilizing at 125 ℃ to obtain a bran mixed solution for later use.

Inoculating the fungus liquid of the aureobasidium pullulans to the bran mixed liquid with the volume of 4.2 percent of that of the bran mixed liquid, and culturing for 5d in a constant-temperature incubator at 37 ℃ to obtain fermentation liquid; and centrifuging the fermentation liquor, collecting supernatant, adding 0-4 ℃ ethanol into the supernatant, placing the supernatant in an environment of 0-4 ℃ for 15 hours, and collecting precipitates.

Dissolving 0.4g of polysaccharide extract in water, adding 0.1g of glycerol, stirring uniformly, and defoaming to prepare a membrane casting solution; pouring the casting solution into a mold, and drying in a 50 ℃ oven to form a film, thus obtaining the food packaging film. Comparative example 1

Weighing 0.3g of pullulan, adding 20mL of water, heating and stirring at 75 ℃ for 1.5h to obtain a pullulan solution.

Adding 0.06g of glycerol into the pullulan solution, stirring uniformly, and defoaming to prepare a membrane casting solution; and pouring the casting solution into a mold, and drying in an oven at 30-50 ℃ to form a film, thus obtaining the food packaging film.

Content detection

The polysaccharide content in the films prepared in examples 1 to 8 was measured according to the following method and reported in table 1.

Content of β -glucan: detecting according to a method given in Jiaying highland barley bran water-soluble beta-glucan extraction, separation and purification and property research [ D ], China eastern university, 2013 ];

pullulan amount: the detection is carried out according to a method of QBT 4485-2013 Pullulan.

TABLE 1 detection of polysaccharide content in food packaging films

Performance testing

The following performance tests were performed on the films prepared in examples 1 to 8 and comparative example, respectively, and the results are reported in table 2.

The detection items comprise: moisture barrier, oxygen barrier, oil penetration, water dissolution time, transparency, sealing strength, and tensile strength.

The detection method comprises the following steps:

tensile strength: detecting by a TA physical property tester according to a method of GB/T1040.3-2006 test conditions for measuring plastic tensile property, part 3, namely film and sheet;

moisture resistance: according to the method of GB1037-1988, the test method of water vapor permeability of plastic films and sheets (cup method), detecting by using a moisture permeable cup;

oxygen barrier properties: the test was carried out according to ASTM D3985-95 using an OX-TRAN2/21MD oxygen transmission rate tester under ambient conditions. (constant temperature incubator-chitosan/lentinan edible film Performance study and characterization)

Water dissolving time: taking a film sample cut into a specification of 2cm multiplied by 2cm, placing the film sample in a beaker filled with water at 90 ℃, starting timing, stopping timing when no particulate matter exists in the water under observation in sunlight after a period of time, and taking the film dissolving time as the water dissolving time;

oil penetration amount: detecting according to a method of GB/T16992-1997 oil permeability test method for packaging materials;

transparency: detection was carried out according to the method given in "Zavarez Eda, R, et al.development of oxidized and heat-existing treated spot to stage film [ J ]. Food Chem,2012.132(1): 344-50";

sealing strength: the test is carried out by a TA physical property tester according to the method of QBT2358-1988, Plastic film packaging bag heat seal strength test.

TABLE 2 Performance test

As can be seen from the above table, the food packaging films prepared in examples 1 to 8 have good moisture resistance, oxygen resistance, oil permeability, water solubility, transparency, sealing strength, tensile strength, and elongation at break, and are significantly superior to comparative examples in moisture resistance, tensile strength, transparency, elongation at break, and sealing strength, indicating that the food packaging films prepared by the preparation method of the present invention have better mechanical properties and barrier properties.

The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.

Claims

1. The preparation method of the food packaging film is characterized by comprising the following steps:

adjusting the pH of the suspension to 5-6.5, and then sterilizing at 120-125 ℃ to obtain a bran mixed solution;

drying the precipitate to obtain polysaccharide extract after removing starch, protein and small molecule salt;

2. The method of claim 1, wherein the step of inoculating the Aureobasidium pullulans bacterial solution into the bran mixed solution and culturing to obtain a fermentation broth,

the inoculation amount is 2-4 (v/v)%; and/or the presence of a gas in the gas,

the culture time is 2-5 days.

3. The method for preparing a food packaging film according to claim 1, wherein the step of inoculating the fungus liquid of aureobasidium pullulans into the bran mixed liquid and culturing to obtain the fermentation liquid further comprises:

4. The method for producing a food packaging film according to claim 3, wherein the step of subjecting Aureobasidium pullulans to mutagenesis and breeding to obtain a mutagenized strain that does not produce melanin comprises:

preparing the aureobasidium pullulans into a bacterial suspension;

5. The method for preparing a food packaging film according to claim 3, wherein the step of inoculating the mutagenic strain into a liquid culture medium, and culturing for 24-36 hours to obtain a bacterial liquid of aureobasidium pullulans comprises the following steps of: 30-50 parts of sucrose, 3-6 parts of dipotassium phosphate, 0.5-2 parts of sodium chloride, 0.1-0.5 part of magnesium sulfate heptahydrate, 0.3-1 part of ammonium sulfate, 2-5 parts of yeast extract and 800-1500 parts of distilled water.

6. The method of manufacturing a food packaging film according to claim 1, wherein the step of centrifuging the fermentation liquid, collecting the supernatant and adding ethanol to the supernatant to cause precipitation, and collecting the precipitate comprises:

centrifuging the fermentation liquor, and collecting supernatant;

and adding ethanol at 0-4 ℃ into the supernatant, placing the supernatant in an environment at 0-4 ℃ for 10-15 hours, and collecting the precipitate.

7. The method for preparing a food packaging film according to claim 1, wherein in the step of dissolving the polysaccharide extract in water, adding glycerol, stirring uniformly to prepare a membrane casting solution, spreading and baking the membrane casting solution to obtain the food packaging film,

the baking temperature is 30-50 ℃.