Edible film and its preparation method and use

Abstract

A preparation method of an edible film, comprising the following steps: 1) taking corn starch and water, mixing and gelatinizing to obtain a gelatinized liquid, adding glycerol, and then adding starch nanocrystals after temperature reduction, stirring, spreading and drying to obtain a lower layer film; 2) pouring a chitosan solution on the lower layer film and spreading and drying; and 3) balancing under constant temperature and humidity conditions to obtain the edible film. The edible film prepared by the method has the advantages of biodegradability and edibility, and is especially suitable for use in butter top milk tea and milk cover top milk tea products.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food, in particular to a kind of edible film and its preparation method and use. BACKGROUND

[0002] Cream top milk tea, milk cover top milk tea cylinder contains tea bottom, cylinder cover contains cream or milk cover.Before sale, cream or milk cover is separated from the tea bottom below, when needing to be eaten, cream or milk cover is mixed with tea bottom, i.e.

[0003] At present, this kind of milk tea product is generally separated by plastic film between cylinder cover and cylinder body.Due to the chemical and physical characteristics of plastic film, its mechanical strength is high, and it is more laborious to mix cream or milk cover with tea bottom, and a large amount of plastic film cannot be biodegraded, causing serious environmental pollution, and harmful to human body.

[0004] Therefore, how to design a kind of biodegradable edible film for separating cream and tea bottom is a problem to be solved by those skilled in the art. SUMMARY

[0005] One of the purposes of the present application is to overcome the shortcomings of the prior art, provide an edible film, which is prepared from biodegradable raw materials, has the advantages of biodegradability and edibility, and is especially suitable for cream top milk tea and milk cover top milk tea products.

[0006] The second purpose of the present application is to provide a preparation method of the above-mentioned edible film, which has simple process and moderate parameters, and is suitable for large-scale production.

[0007] The technical scheme for achieving the purpose of the present application is: a preparation method of an edible film, comprising the following steps:

[0008] 1) corn starch, water, mixed paste, obtained paste liquid, glycerol, after cooling, starch nanocrystals are added, stirred and spread flat and dried to obtain lower layer film;

[0009] 2) pouring chitosan solution on the lower layer film, and spreading flat and drying;

[0010] 3) equilibrium under constant temperature and humidity conditions to obtain edible film.

[0011] Further, the mass-volume ratio of corn starch and water in step 1) is 1:16-20, and the mixed paste is stirred and pasted at 85-100 DEG C.

[0012] Further, the amount of glycerol added in step 1) is 1:2.5-3 of the mass ratio of corn starch.

[0013] Further, the temperature of step 1) is reduced to 25±3℃, and the starch nanocrystal is added in an amount of 1:6-20 by mass ratio to the gelatinized liquid.

[0014] Further, the thickness of the flattened material in step 1) is 0.5-0.7cm, and the drying is performed by hot air drying at 45℃.

[0015] Further, the concentration of the cast chitosan solution in step 2) is 2% w / v, and the thickness of the flattened material is 0.5-0.7cm.

[0016] Further, the temperature of the drying in step 2) is 45-55℃, and the drying is performed for 6-8h until the weight is constant.

[0017] Further, the temperature of the constant temperature in step 3) is 24±3℃, the constant humidity is 50±5% RH, and the equilibration time is 24-36h.

[0018] The application also provides an edible film prepared by any of the above preparation methods.

[0019] The application claims the use of the above edible film for separating cream and tea base.

[0020] The above technical solution has the following beneficial effects:

[0021] 1. The edible film prepared by the application can slowly absorb water and swell after being in contact with tea base for 30-60min, the mechanical strength is reduced, and the film can be easily poked by a straw to mix the cream or milk cover above with the tea base below.

[0022] 2、The edible film prepared by the application, the lower film is prepared by pasting corn starch, adding glycerol and starch nanocrystals, and then flattening, drying, etc., wherein the starch is a natural, renewable and biodegradable biopolymer, has strong film-forming ability, forms a continuous matrix, and has no taste and color, and is more easily accepted by consumers. By adding starch nanocrystals, the mechanical strength (including tensile strength, Young's modulus, elongation at break) and barrier properties of the starch matrix are improved, and the water vapor permeability is reduced. The added glycerol acts as a plasticizer in the preparation process, which destroys the intermolecular / intramolecular hydrogen bonds of the granular starch, eliminates the interaction between starch and starch, and is replaced by starch-plasticizer interaction, accompanied by partial depolymerization of the starch skeleton, and the melting temperature of the starch is reduced below its decomposition temperature, thereby playing a lubricating role, promoting the flowability of the polymer chain, and slowing down the retrogradation of the starch. The formation of a uniform and stable starch film has a certain barrier effect on the tea base, and has hygroscopicity, which promotes the slow water absorption and swelling of the starch matrix within 30-60 minutes of contact with water, and the mechanical strength is weakened, so that the consumer can directly use a straw to pierce it, facilitating the mixing of cream and tea base. The upper film is prepared by flattening and drying a chitosan solution, and the chitosan is a deacetylated derivative of chitin and has some unique properties, such as biodegradability, non-toxicity, biocompatibility and antifungal properties. The chitosan film also exhibits flexibility, durability, strength, toughness and high folding resistance, and has moderate water and oxygen permeability, which helps to reduce the respiration rate of food, effectively blocks the lipid materials such as cream and milk cover, and meets the purpose of separating cream and tea base before use.

[0023] 3、The preparation method of the application, first, the starch aqueous solution is heated and pasted, so that the starch swells and forms a viscous paste, and the starch particle structure undergoes a phase change from order to disorder in water. The starch particles continue to swell by absorbing water, and when the volume swells to a certain limit, the starch particles break, and the starch molecules in the particles spread and diffuse in all directions, and the extended starch molecules are connected and intertwined to form a three-dimensional network containing water. Then glycerol is added, which is a small molecule compound and can be uniformly dispersed in the three-dimensional network containing water, improving the flexibility and processability of the finally prepared film. Then starch nanocrystals are added and mixed uniformly, so that the lower film obtained by drying is transparent and uniform in color. Then chitosan solution is poured on the lower film and dried to obtain the upper film, which can effectively block the lipid materials such as cream and milk cover. Finally, under constant temperature and humidity conditions, the solvent is better volatilized, the internal structure is stabilized, and it is not easy to change with temperature and humidity.

[0024] The edible film prepared by the application has mechanical properties including tensile strength, Young's modulus and elongation at break of 8.49 MPa, 10.22 MPa and 86.33%, respectively, which meet the purpose of separating butter from tea base before use. After the film is soaked in tea base for 1 h, the mechanical properties are 6.12 MPa, 7.65 MPa and 104.66%, respectively, which indicates that the starch film is more prone to breakage and the brittleness increases after being soaked in tea water for 1 h, and the film can be directly poked by a straw to facilitate the mixing of butter and tea base for consumers.

[0025] Further description is made in combination with the specific embodiments.

[0026] Drawings of the specification

[0027] Figure 1 The photo of the edible film prepared in Example 1. Specific embodiments

[0028] In the application, corn starch: Chongqing Yue Xiang Chemical Co., Ltd., food grade; glycerol: Chongqing Yue Xiang Chemical Co., Ltd., reagent purity; chitosan: DAC > 95%, Chongqing Amida Biological Technology Co., Ltd.; starch nanocrystals: self-made, the average particle size is 521 nm and the zeta potential is -33.8 mV, which are measured by using a nanoparticle size analyzer.

[0029] Example 1

[0030] 5 g of corn starch powder (dry basis) is weighed and added to a 250 mL conical flask containing 100 mL of deionized water, and stirred uniformly. Then the starch suspension is heated in a water bath at 90°C for 30 minutes while stirring at a speed of 500 rpm to completely gelatinize the starch. Then the heating is stopped and it is cooled to 40°C. 1.5 g of glycerol is added, 0.02 g of starch nanocrystals is added, and stirring is performed at 150 rpm for 20 minutes. Finally, 40 mL of film-forming solution is poured into a Teflon mold (150 mm x 150 mm x 10 mm) with a thickness of 0.5-0.7 cm, and placed in an oven for hot air drying at 45°C. The lower layer film is obtained; chitosan solution (2% w / v) is poured on the lower layer film, and the thickness of the flat surface is 0.5-0.7 cm. The film is naturally leveled and dried again at 45°C. After 48 hours of equilibrium in a constant temperature and humidity box with a temperature setting of 25°C and a relative humidity setting of 50% RH, the film is carefully peeled off to obtain a colorless and high-transparency edible film, as shown in Figure 1 .

[0031] Example 2

[0032] Take 5 g of corn starch powder (dry basis) into a 250 mL conical flask containing 100 mL of deionized water and stir evenly. Then heat the starch suspension in a water bath at 90°C for 30 minutes while stirring at a speed of 500 rpm to completely gelatinize the starch. Then stop heating and cool it to 40°C. Add 1.5 g of glycerol, add 0.04 g of starch nanocrystals, and stir at 150 rpm for 20 minutes. Finally, pour 40 mL of the film-forming solution into a Teflon mold (150 mm x 150 mm x 10 mm) with a thickness of 0.5-0.7 cm, and place it in an oven for hot air drying at 45°C; pour the chitosan solution (2% w / v) on top of the lower layer film, spread it to a thickness of 0.5-0.7 cm, and let it flow naturally, then dry it again at 45°C, and place it in a constant temperature and humidity chamber with a temperature setting of 25°C and a relative humidity setting of 50% RH, and after 48 hours of equilibrium, carefully peel off the film to obtain a colorless, high-transparency edible film.

[0033] Example 3

[0034] Take 5 g of corn starch powder (dry basis) into a 250 mL conical flask containing 100 mL of deionized water and stir evenly. Then heat the starch suspension in a water bath at 90°C for 30 minutes while stirring at a speed of 500 rpm to completely gelatinize the starch. Then stop heating and cool it to 40°C. Add 1.5 g of glycerol, add 0.04 g of starch nanocrystals, and stir at 150 rpm for 20 minutes. Finally, pour 40 mL of the film-forming solution into a Teflon mold (150 mm x 150 mm x 10 mm) with a thickness of 0.5-0.7 cm, and place it in an oven for hot air drying at 45°C; pour the chitosan solution (2% w / v) on top of the lower layer film, spread it to a thickness of 0.5-0.7 cm, and let it flow naturally, then dry it again at 45°C, and place it in a constant temperature and humidity chamber with a temperature setting of 25°C and a relative humidity setting of 50% RH, and after 48 hours of equilibrium, carefully peel off the film to obtain a colorless, high-transparency edible film.

[0035] Example 4

[0036] Take 5 g of corn starch powder (dry basis) into a 250 mL conical flask containing 100 mL of deionized water and stir evenly. Then heat the starch suspension in a water bath at 90°C for 30 minutes while stirring at a speed of 500 rpm to completely gelatinize the starch. Then stop heating and cool it to 40°C. Add 1.5 g of glycerol, add 0.02 g of starch nanocrystals, and stir at 150 rpm for 20 minutes. Finally, pour 40 mL of the film-forming solution into a Teflon mold (150 mm x 150 mm x 10 mm) with a thickness of 0.5-0.7 cm, and place it in an oven for hot air drying at 65°C; pour the chitosan solution (2% w / v) on top of the lower film, spread it to a thickness of 0.5-0.7 cm, and let it flow naturally, then dry it again at 45°C, and place it in a constant temperature and humidity chamber with a temperature setting of 25°C and a relative humidity setting of 50% RH, and equilibrate for 48 hours, then carefully peel off the film to obtain a colorless, high-transparency edible film.

[0037] The mechanical strength data of the edible films prepared in Examples 1-4 were detected as shown in the following table:

[0038] Treatment Tensile strength (MPa) Young's modulus (MPa) Elongation at break % Example 1 8.49 10.22 86.33 Example 2 10.55 13.83 58.91 Example 3 9.50 11.32 75.64 Example 4 6.98 9.34 92.54 The mechanical performance data of the films prepared in each example after 1 h of immersion are shown in the following table:

[0039] Treatment Tensile strength (MPa) Young's modulus (MPa) Elongation at break % Example 1 4.11 2.61 125.99 Example 2 3.53 2.87 93.67 Example 3 2.83 7.65 51.66 Example 4 1.72 3.87 40.92

Claims

1. A method of preparing an edible film, characterized by: The edible film for separating butter and tea base comprises the following steps: 1) taking corn starch and water, mixing and gelatinizing to obtain a gelatinized liquid, adding glycerol, then adding starch nanocrystals after cooling, stirring and then spreading and drying to obtain a lower layer film, the mass ratio of the added glycerol to the corn starch is 1:2.5-3, the mass ratio of the added starch nanocrystals to the gelatinized liquid is 1:6-20, and the temperature is cooled to 25±3℃; 2) pouring a chitosan solution on the lower layer film and then spreading and drying, the concentration of the poured chitosan solution is 2% w / v, and the thickness of the spread film is 0.5-0.7cm; 3) balancing under constant temperature and humidity conditions to obtain the edible film, the temperature of the constant temperature is 24±3℃, the humidity of the constant humidity is 50±5%RH, and the balancing time is 24-36h.

2. The production method according to claim 1, characterized by, In step 1), the mass-volume ratio of the corn starch and water is 1:16-20, and the mixing and gelatinizing is carried out under the condition of stirring and gelatinizing at 85-100℃.

3. The production method according to claim 1, characterized by, In step 1), the thickness of the spread film is 0.5-0.7cm, and the drying is hot air drying at 45℃.

4. The method of claim 1, wherein, In step 2), the drying temperature is 45-55℃, and the drying is carried out for 6-8h until the weight is constant.

5. Use of an edible film for separating cream and tea base, characterized in that, The edible film is prepared by any one of the preparation methods in claims 1-4.

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