CN112978081A

CN112978081A - Fruit and vegetable preservative film and preparation method and application thereof

Info

Publication number: CN112978081A
Application number: CN202110215020.0A
Authority: CN
Inventors: 刘洋; 刘克增; 刘克川; 衣治政
Original assignee: Laiyang Chengfeng Food Co ltd
Current assignee: Laiyang Chengfeng Food Co ltd
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2021-06-18

Abstract

The application relates to the field of preservative films, and particularly discloses a fruit and vegetable preservative film and a preparation method and application thereof. The fruit and vegetable preservative film is prepared from the following raw materials in parts by weight: 50 parts of polyethylene, 40-120 parts of white oil, 1-10 parts of sodium polyacrylate, 3-12 parts of degradable master batch, 0.5-3 parts of zeolite, 0.3-2.5 parts of quartz stone and 0.5-3 parts of nano titanium dioxide. The preparation method of the fruit and vegetable preservative film comprises the steps of raw material mixing, melt extrusion, inflation film forming, cooling soaping and the like. The application of the fruit and vegetable preservative film can be used for wrapping single-grain fresh pears. This application can improve the fresh-keeping effect of fruit vegetables plastic wrap to fruit vegetables through the mutual compatibility of polyethylene, white oil, sodium polyacrylate and other components, has prolonged the save time of fruit vegetables. Meanwhile, the fresh pear is wrapped by the single fresh-keeping film, so that the aim of ventilating and fresh-keeping the fresh pear is fulfilled, the loss of water in the fresh pear is reduced, and the storage time of the fresh pear and the preservation time of the crispness of the fresh pear are prolonged.

Description

Fruit and vegetable preservative film and preparation method and application thereof

Technical Field

The application relates to the field of preservative films, in particular to a fruit and vegetable preservative film and a preparation method and application thereof.

Background

The fruits are placed in a refrigeration house for storage after being picked, the time is basically 3-7 days before the fruits are delivered to markets for circulation and arrive at the hands of consumers, and some fruits even reach as long as one month. The circulation process needs to be fresh-keeping, and the mode that wherein adopts the plastic wrap to lock the fresh recirculation with fruit vegetables parcel is comparatively commonly used and convenient a mode. In the mode, the fruit and vegetable preservative film plays an important role.

At present, in the related technology, the fruit and vegetable preservative film is prepared by using polyethylene as a base material and adding degradable master batches, color master batches, antioxidants and other auxiliary agents. The preservative film has good corrosion resistance and low temperature resistance; and the coating does not contain a plasticizer, is odorless and nontoxic and has high safety. Meanwhile, the polyethylene preservative film also has certain air permeability.

In view of the above-mentioned related technologies, the inventor believes that the requirements for the freshness preservation of fruits and vegetables are higher and higher due to the development of society and the improvement of the requirements for life quality, and further improvement of the freshness preservation capability of the preservative film for fruits and vegetables is required.

Disclosure of Invention

In order to improve the fresh-keeping capacity of the fresh-keeping film on fruits and vegetables, the application provides the fresh-keeping film for fruits and vegetables and the preparation method and application thereof.

In a first aspect, the application provides a fruit and vegetable preservative film, which adopts the following technical scheme:

the fruit and vegetable preservative film is prepared from the following raw materials in parts by weight: 50 parts of polyethylene, 40-120 parts of white oil, 1-10 parts of sodium polyacrylate, 3-12 parts of degradable master batch, 0.5-3 parts of zeolite, 0.3-2.5 parts of quartz stone and 0.5-3 parts of nano titanium dioxide.

By adopting the technical scheme, the white oil can be used as a diluent to be uniformly mixed with polyethylene into a whole under the high-temperature melting condition. While when cooled, the white oil and polyethylene will separate; due to the separation of the white oil, micropores are left on the obtained polyethylene preservative film, so that the polyethylene preservative film is more breathable. Meanwhile, the addition of the sodium polyacrylate can enable the preservative film to have certain hygroscopicity, can absorb moisture around the fruits and vegetables, and inhibits the respiration of the fruits and vegetables, so that the transpiration effect is reduced, and further the loss of moisture of the fruits and vegetables is reduced. The preservation capability of the fruit and vegetable preservative film on fruits and vegetables can be improved and the storage time of the fruits and vegetables can be prolonged through the mutual compatibility of polyethylene, white oil, sodium polyacrylate and other components.

Optionally, the raw material also comprises glyceryl monostearate, and the addition amount of the glyceryl monostearate is 2-6wt% of the polyethylene.

By adopting the technical scheme, the addition of the glyceryl monostearate is favorable for improving the compatibility among the components of the raw materials, so that the mixing uniformity of the components of the raw materials is improved, and the performance of the fruit and vegetable preservative film is further improved.

Optionally, the raw materials further comprise a milky white color master batch and an antioxidant; the addition amount of the milky white color master batch is 2-6wt% of the polyethylene, and the addition amount of the antioxidant is 0.4-1wt% of the polyethylene.

By adopting the technical scheme, the addition of the milky white master batch endows the fruit and vegetable preservative film with milky color. The antioxidant is added to improve the oxidation resistance of the fruit and vegetable preservative film.

Optionally, the feed additive is prepared from the following raw materials in parts by weight: 50 parts of polyethylene, 50-100 parts of white oil, 4-8 parts of sodium polyacrylate, 5-8 parts of degradable master batch, 1-2 parts of zeolite, 0.8-1.5 parts of quartz stone, 1.2-2.5 parts of nano titanium dioxide, 1-3 parts of glyceryl monostearate, 1-3 parts of milky white master batch and 0.2-0.5 part of antioxidant.

By adopting the technical scheme, the compatibility of the components is further optimized, and the comprehensive performance of the fruit and vegetable preservative film is favorably improved.

Optionally, the kinematic viscosity of the white oil at 40 ℃ is 12-75mm²/s。

By adopting the technical scheme, the white oil with excessively high kinematic viscosity is not beneficial to the operation of melt extrusion; white oil with lower kinematic viscosity has correspondingly lower flash point, which is not beneficial to the high-temperature melting process.

Optionally, the polyethylene is low density polyethylene, and the density of the polyethylene is 0.916-0.927g/cm for carrying out the high-speed harvest.

By adopting the technical scheme, the high-density polyethylene has higher crystallinity compared with the low-density polyethylene, so the flexibility of the high-density polyethylene is poorer; the obtained preservative film is compact and has poor air permeability.

Optionally, the particle size of the zeolite is 0.2-0.8 μm, and the particle size of the quartz stone is 0.2-0.8 μm.

By adopting the technical scheme, the zeolite and the quartz stone are added to be beneficial to forming mutually communicated micropores or channels in the preservative film, but the formation of the micropores can be influenced by the undersize particle sizes of the zeolite and the quartz stone; the appearance and mechanical properties of the preservative film are adversely affected by the excessively large particle size.

In a second aspect, the application provides a preparation method of a fruit and vegetable preservative film, which adopts the following technical scheme:

the preparation method of the fruit and vegetable preservative film comprises the following steps:

weighing raw materials of each component and uniformly mixing;

melting and extruding the mixed raw materials to obtain a blank;

blowing a blank to form a film, wherein the blowing ratio of the blank in the blowing film forming process is controlled to be 2.1-2.9, and the traction ratio is controlled to be 4-5.2;

and cooling the film, soaping and drying.

By adopting the technical scheme, the fruit and vegetable preservative film is smoothly prepared. The white oil separated from the preservative film can be cleaned by soaping.

In a third aspect, the application provides an application of a fruit and vegetable preservative film, which adopts the following technical scheme:

the application of the fruit and vegetable preservative film is used for wrapping single-grain fresh pears.

By adopting the technical scheme, the fresh pears are wrapped by the single fruit and vegetable preservative film, so that the purposes of ventilation and preservation of the fresh pears are achieved, the water loss of the fresh pears is reduced, the storage time of the fresh pears is prolonged, and the crispness of the fresh pears is kept.

Optionally, the method for wrapping fresh pears with the fruit and vegetable preservative film comprises the following steps:

placing single fresh pears in the middle of the fruit and vegetable preservative film;

turning over one corner of the fruit and vegetable preservative film forwards and covering the fruit and vegetable preservative film on the fresh pears, and then turning over the turned-over part of the fruit and vegetable preservative film and the fresh pears forwards together;

folding the fruit and vegetable preservative films positioned on the two sides of the fresh pears forwards;

overlapping the corners of the fruit and vegetable preservative film facing forwards and rotating the corners to wind the corners together;

sticking a label to fix the corners of the twisted fruit and vegetable preservative film;

and further sticking a label on the fruit and vegetable preservative film, wherein the two labels are symmetrical about the fresh pear.

By adopting the technical scheme, the single-grain fresh pears can be completely and firmly wrapped in the fruit and vegetable preservative film, and the single-grain fresh-keeping of the fresh pears is realized.

In summary, the present application has at least one of the following beneficial technical effects:

1. this application can improve the fresh-keeping ability of fruit vegetables plastic wrap to fruit vegetables through the mutual compatibility of polyethylene, white oil, sodium polyacrylate and other components to the latency of fruit vegetables has been prolonged. The white oil can make the polyethylene preservative film have micropores, so that the polyethylene preservative film has higher air permeability. The addition of the sodium polyacrylate can enable the preservative film to have certain hygroscopicity, can reduce the humidity around the fruits and vegetables, and inhibit the respiration of the fruits and vegetables, so that the transpiration effect is reduced, further the loss of the moisture of the fruits and vegetables is reduced, and the problem of the loss increase of the moisture of the fruits and vegetables caused by the increase of the micropores of the preservative film is favorably solved.

2. The compatibility between each component of the raw materials is improved by adding the glyceryl monostearate, so that the raw materials are mixed more uniformly, and the comprehensive performance of the fruit and vegetable preservative film is improved.

3. The fresh pear preservative film is used for wrapping fresh pears with single particles, so that the purpose of ventilating and refreshing the fresh pears is favorably achieved, the loss of moisture of the fresh pears is reduced, and the storage time of the fresh pears and the preservation time of the crispness of the fresh pears are prolonged.

4. The application relates to a method for wrapping single-grain fresh pears, which can wrap the preservative film on the fresh pears completely and fixedly. The wrapping method is efficient and convenient.

Detailed Description

With the improvement of the preservation requirements of fruits and vegetables, the preservation capability of the preservative film on fruits and vegetables needs to be further improved, the air permeability of the preservative film is improved, and the water loss capability of the fruits and vegetables is reduced. The breathability of the cling film can be achieved by increasing the microporosity on the cling film. The inventor adds micropores on the preservative film through the introduction of white oil. However, the increase of the micropores on the preservative film is more beneficial to the loss of the moisture of the fruits and the vegetables, thereby being not beneficial to the preservation of the fruits and the vegetables. Therefore, the inventor introduces sodium polyacrylate with moisture absorption capacity on the preservative film, and reduces the moisture loss of fruits and vegetables by reducing the humidity around the fruits and vegetables, further inhibiting the respiration of the fruits and vegetables and reducing the transpiration. Therefore, the preservation capability of the preservative film on fruits and vegetables is improved through the mutual compatibility of polyethylene, white oil, sodium polyacrylate and other components.

The present application will be described in further detail with reference to examples.

Among the relevant raw materials used in the examples:

low Density Polyethylene (LDPE) with a density of 0.916g/cm was obtained from Shanghai super cyclone chemical technology, Inc. (trademark: MB 9500). Low density polyethylene having a density of 0.927g/cm was obtained from Suzhou New crystalline Rice material, Inc. (trademark: 1007). High density polyethylene was purchased from Stand alone chemical Co., Ltd, Dongguan (trade name: HE 7541-PH). The 15# white oil, the 26# white oil, the 36# white oil and the 70# white oil are all food grade and are purchased from Foshan Oster science and technology Co. Sodium polyacrylate was purchased from denna wheat chemical ltd. The degradable master batch is purchased from Jiajiajia plastic raw materials Co., Ltd, Dongguan city (product number: JJ 316).

Examples 1 to 13

As shown in Table 1, examples 1-13 differ mainly in the ratios of the raw materials.

The following description will be made of example 1. The polyethylene in this example was low density polyethylene having a density of 0.916 g/cm. The low-density polyethylene is a base material of the preservative film, has good flexibility, extensibility, transparency and chemical stability, and has certain air permeability. Therefore, the preservative film prepared from the low-density polyethylene has air permeability, and is beneficial to the ventilation of the coated fruits and vegetables, thereby being beneficial to realizing the aim of preserving the fruits and vegetables.

The white oil is food grade 36# white oil with kinematic viscosity of 35.5mm at 40 deg.C²And s. White oil as a diluent is uniformly mixed with polyethylene under high-temperature melting to form a whole. And after cooling, the white oil and the polyethylene can be separated, and the white oil leaves the polyethylene preservative film and leaves micropores on the preservative film, so that the preservative film is more breathable.

The sodium polyacrylate has the moisture absorption capacity, so the addition of the sodium polyacrylate can enable the preservative film to have the effect of reducing the humidity around the fruits and vegetables. The relatively dry environment is favorable for inhibiting the respiration of the fruits and vegetables, so that the transpiration of the fruits and vegetables can be reduced. Therefore, the addition of the sodium polyacrylate is beneficial to reducing the loss of water in the fruits and the vegetables, and is further beneficial to improving the freshness of the fruits and the vegetables.

The main components of the degradable master batch are polylactic acid and monosaccharide, and the degradable master batch has degradability; in the environment with active microorganisms, the degradable master batch can attract various microorganisms to erode the digestive polymer product, and the biodegradability of the fruit and vegetable preservative film is improved.

The zeolite, the quartz stone and the nano titanium dioxide can form mutually communicated micropores or channels in the preservative film, thereby being beneficial to improving the air permeability of the prepared preservative film. In addition, the particle size of the zeolite is controlled to be 0.2-0.8 μm, and the particle size of the quartz is controlled to be 0.2-0.8 μm; the formation of micropores can be influenced when the particle sizes of the two are too small, and the appearance and the mechanical property of the preservative film can be adversely influenced when the particle sizes are too large. The average primary particle size of the nano titanium dioxide is 20-30 nm.

The fruit and vegetable preservative film is prepared by the following method:

(1) polyethylene, white oil, sodium polyacrylate, degradable master batch, zeolite, quartz stone and nano titanium dioxide are weighed according to the formula and placed in a stirrer, and are uniformly mixed at 40 ℃.

(2) Introducing the mixed raw materials into a double-screw extruder to be melted and extruded to obtain a blank; wherein the temperature of each zone of the extruder is controlled to be 135 ℃, 145 ℃, 155 ℃ and 165 ℃ respectively.

(3) Blowing the blank into a blow molding machine to be blown into a film; wherein, the blank blow-up ratio is controlled to be 2.5, and the traction ratio is controlled to be 4.5.

(4) Cooling the preservative film to room temperature; then, the preservative film is rinsed by using an aqueous solution containing 5 percent of common detergent (or scrubbed by using cloth or a roller with detergent on the surface) to remove the white oil separated during cooling, and then the preservative film is washed clean by using clean water. And finally, drying the preservative film to obtain a finished product. The fruit and vegetable preservative film can be cut into square or strip films according to the actual application requirements.

The fruit and vegetable preservative film is suitable for wrapping single fresh pears (such as autumn and moon pears). The specific wrapping method comprises the following steps:

(1) taking the fruit and vegetable preservative film cut into squares; and placing the single fresh pear in the middle of the preservative film.

(2) Turning up and covering one corner (defined as a corner A) of the preservative film along a diagonal line forwards (the direction facing to the opposite corner of the corner A is defined as the forward direction) on the fresh pear, and then turning over the turned-up part of the preservative film and the fresh pear along the diagonal line forwards; at the moment, the preservative film rolls the fresh pears therein.

(3) The fruit and vegetable preservative films positioned on two sides of the fresh pears are folded forwards (namely towards the direction of the opposite angle of the angle A), so that the other angles of the preservative films except the angle A all face the same direction (namely towards the front).

(5) Overlapping and rotating the corners of the preservative film facing forwards to wind the corners of the preservative film together; at the moment, the fresh pear is completely wrapped in the preservative film.

(6) A label is attached to each corner of the twisted fruit and vegetable preservative film and is fixed to seal the fruit and vegetable preservative film, so that fresh pears are firmly wrapped by the preservative film.

(7) And then, a label is attached to the preservative film, and the two labels are symmetrical about the fresh pear. Therefore, the appearance is attractive and the mark is convenient.

TABLE 1 examples 1-18 raw material ratios

Serial number	Polyethylene	White oil	Polyacrylamide sodium salt	Degradable master batch	Zeolite	Quartz stone	Nano titanium dioxide	Glyceryl monostearate	Milky white color master batch	Antioxidant agent
											Example 1	50	40	10	3	3	0.3	0.5	0	0	0
Example 2	50	50	8	5	2	0.8	2	0	0	0
											Example 3	50	80	6	6	2	1	2.5	0	0	0
Example 4	50	100	4	8	1	1.5	1.2	0	0	0
											Example 5	50	120	1	12	0.5	2.5	3	0	0	0
Example 6	50	40	6	6	2	1	2.5	0	0	0
											Example 7	50	50	6	6	2	1	2.5	0	0	0
Example 8	50	100	6	6	2	1	2.5	0	0	0
											Example 9	50	120	6	6	2	1	2.5	0	0	0
Example 10	50	80	1	6	2	1	2.5	0	0	0
											Example 11	50	80	4	6	2	1	2.5	0	0	0
Example 12	50	80	8	6	2	1	2.5	0	0	0
											Example 13	50	80	10	6	2	1	2.5	0	0	0
Example 14	50	80	6	6	2	1	2.5	1	0	0
											Example 15	50	80	6	6	2	1	2.5	2	0	0
Example 16	50	80	6	6	2	1	2.5	3	0	0
											Example 17	50	80	6	6	2	1	2.5	2	1	0.2
Example 18	50	80	6	6	2	1	2.5	2	3	0.5

Note: the addition unit of each component is kg.

Examples 14 to 16

As shown in Table 1, examples 14-16 are substantially the same as example 3, except that glyceryl monostearate was added to each of examples 14-16. The material has good surface activity, and is beneficial to improving the mixing uniformity of all components.

Meanwhile, the main difference between examples 14 to 16 is that the amount of glycerol monostearate added is different.

Examples 17 to 18

As shown in Table 1, examples 17 to 18 were substantially the same as example 15 except that milky white master batches and an antioxidant were added to the examples 17 to 18. Wherein, the addition of the milky white color master batch enables the preservative film to have milky white color; the antioxidant is added to improve the oxidation resistance of the preservative film.

Meanwhile, the main difference between example 17 and example 18 is that the amount of the opal color concentrate and the antioxidant added is different.

Example 19

This example is essentially the same as example 18 except that the white oil was a food grade 15# white oil; the white oil has a kinematic viscosity of 12mm at 40 deg.C²/s。

Example 20

This example is essentially the same as example 18 except that the white oil was a food grade 26# white oil; the white oil has a kinematic viscosity of 26mm at 40 deg.C²/s。

Example 21

This example is essentially the same as example 18 except that the white oil was a food grade 70# white oil; the white oil has a kinematic viscosity of 75mm at 40 deg.C²/s。

Example 22

This example is substantially the same as example 18, except that the polyethylene is low density polyethylene having a density of 0.927 g/cm.

Example 23

This example is substantially the same as example 18, except that the high density polyethylene having a density of 0.954g/cm was taken as the polyethylene.

Example 24

This example is substantially the same as example 18 except that the billet inflation ratio and the draft ratio in step (3) of the cling film production method are different.

The method specifically comprises the following steps: and (3): blowing the blank into a blow molding machine to be blown into a film; wherein, the blank blow-up ratio is controlled to be 2.9, and the traction ratio is controlled to be 5.2.

Example 25

The method specifically comprises the following steps: and (3): blowing the blank into a blow molding machine to be blown into a film; wherein, the blank blow-up ratio is controlled to be 2.1, and the traction ratio is controlled to be 4.0.

Comparative example 1

This comparative example is essentially the same as example 18 except that the feed composition does not contain white oil.

The concrete raw materials comprise: 50kg of polyethylene, 6kg of sodium polyacrylate, 6kg of degradable master batch, 2kg of zeolite, 1kg of quartz stone, 2.5kg of nano titanium dioxide, 2kg of glycerin monostearate, 3kg of milky white master batch and 0.5kg of antioxidant.

Comparative example 2

This comparative example is essentially the same as example 18 except that the starting material composition does not contain sodium polyacrylate.

The concrete raw materials comprise: 50kg of polyethylene, 80kg of white oil, 6kg of degradable master batch, 2kg of zeolite, 1kg of quartz stone, 2.5kg of nano titanium dioxide, 2kg of glycerin monostearate, 3kg of milky white master batch and 0.5kg of antioxidant.

Comparative example 3

This comparative example is essentially the same as example 18 except that the raw material composition does not contain zeolite, quartz and nano-titania.

The concrete raw materials comprise: 50kg of polyethylene, 80kg of white oil, 6kg of sodium polyacrylate, 6kg of degradable master batch, 2kg of glyceryl monostearate, 3kg of milky master batch and 0.5kg of antioxidant.

Performance detection

The fruit and vegetable preservative films obtained in examples 1 to 25 and comparative examples 1 to 3 were subjected to performance tests.

1. Oxygen transmission rate test: the test was performed with reference to the standard GB/T1038-2000. Wherein the testing temperature is 25 ℃; the thickness of the sample was 100. mu.m.

2. Testing the tensile strength; the test was performed with reference to standard QB/T1040.3-2006. Wherein the sample is a type 2 sample, and the width of the sample is 10 mm; the gauge length is 50 mm; the test speed (no load) was 500 mm/min.

3. Fresh-keeping test: wrapping autumn and moon pears with fruit and vegetable preservative films, and placing for 21 days at 6 ℃. The pear was then removed and evaluated by 5 professionals for freshness.

The test results are as follows:

TABLE 2 Performance test of the fruit and vegetable preservative films obtained in examples 1-25 and comparative examples 1-3

Serial number	Oxygen transmission capacity cm³/(m²•24h·atm)	Tensile strength Mpa	Fresh condition of autumn and moon pears
				Example 1	12990	13.3	Fresh without shriveling or softening
Example 2	13217	13.3	Fresh without shriveling or softening
				Example 3	13488	13.2	Fresh without shriveling or softening
Example 4	13522	13.5	Fresh without shriveling or softening
				Example 5	13600	12.7	Fresh without shriveling or softening
Example 6	13122	13.2	Basic freshness
				Example 7	13298	13.1	Fresh without shriveling or softening
Example 8	13589	13.0	Fresh without shriveling or softening
				Example 9	13605	13.1	Fresh without shriveling or softening
Example 10	13476	14.0	Basic freshness
				Example 11	13452	13.5	Fresh without shriveling or softening
Example 12	13488	12.8	Fresh without shriveling or softening
				Example 13	13443	12.3	Fresh without shriveling or softening
Example 14	13568	13.5	Fresh without shriveling or softening
				Example 15	13617	13.7	Fresh without shriveling or softening
Example 16	13592	13.6	Fresh without shriveling or softening
				Example 17	13608	13.6	Fresh without shriveling or softening
Example 18	13612	13.6	Fresh without shrivelingOr soften it
				Example 19	13615	13.5	Fresh without shriveling or softening
Example 20	13603	13.7	Fresh without shriveling or softening
				Example 21	13601	13.4	Fresh without shriveling or softening
Example 22	13608	13.8	Fresh without shriveling or softening
				Example 23	12503	13.9	Basic freshness
Example 24	13620	13.0	Fresh without shriveling or softening
				Example 25	13609	13.6	Fresh without shriveling or softening
Comparative example 1	10213	12.9	Soft and crisp taste
				Comparative example 2	13602	12.9	Shrivelled and has less water
Comparative example 3	12132	14.0	Has crisp taste

Referring to Table 2, examples 1-5 examined the properties of the fruit and vegetable preservative films prepared by different formulations. As can be seen from the test results in the table: the oxygen transmission capacity of the prepared fruit and vegetable preservative film is 12990 cm³/(m²24h · atm) or more, showing better air permeability; and the tensile strength of the prepared fruit and vegetable preservative film is more than 10Mpa, which accords with the national standard of preservative films. Meanwhile, the autumn-moon pears wrapped by the prepared fruit and vegetable preservative film still keep fresh, do not shrink or soften after being placed for 21 days at the temperature of 6 ℃, and have crisp mouthfeel and rich water.

Example 18 and comparative example 1 examine the effect of the addition of white oil on the performance of fruit and vegetable preservative films. The detection result can find that: when no white oil was added (comparative example 1), the oxygen transmission of the resulting wrap was small; when white oil (example 18) was added, the resulting cling film had good oxygen transmission. This is because white oil can mix with polyethylene to a single phase when melted; and when the plastic wrap is cooled, the white oil and the polyethylene can be separated, so that micropores are left on the obtained polyethylene plastic wrap, a channel is provided for oxygen permeation, and the air permeability of the plastic wrap is improved. Meanwhile, the autumn moon pears wrapped by the preservative film prepared in the embodiment 18 can still keep fresh after being placed in an environment of 6 ℃ for 21 days. In contrast, the autumn moon pears wrapped by the preservative film of the comparative example 1 are softened due to unsmooth ventilation after being placed at 6 ℃ for 21 days, and are poor in taste and not crisp after being bitten; this is due to the poor air permeability of the wrap of comparative example 1.

Example 3 and examples 6 to 9 examine the influence of the addition amount of the white oil on the performance of the fruit and vegetable preservative film. The detection result can find that: with the increasing of the added white oil, the oxygen transmission of the fruit and vegetable preservative film is increased continuously. However, the addition of excessive white oil will cause a burden on the post-cleaning treatment of the wrap. Therefore, the addition amount of the white oil is controlled to be 80-240wt% of the addition amount of the polyethylene; more preferably 100-200 wt%.

Example 18 and comparative example 2 examine the effect of the addition of sodium polyacrylate on the performance of fruit and vegetable preservative films. Comparative example 18 and comparative example 2: the autumn-month pears wrapped by the fruit and vegetable preservative film (comparative example 2) without the sodium polyacrylate are obviously shrunken and have less water after being placed for 21 days; the autumn-month pears wrapped by the fruit and vegetable preservative film added with the sodium polyacrylate (example 3) are still fresh after being placed for 21 days, and are crisp in taste and rich in moisture. The reason is that the sodium polyacrylate has a certain moisture absorption function, and the preservative film with the sodium polyacrylate can reduce the humidity around the fruits and vegetables. And the relatively dry environment is favorable for inhibiting the respiration of fruits and vegetables, so that the transpiration of the fruits and vegetables is reduced, the loss of the water in the fruits and vegetables is reduced, and the freshness of the fruits and vegetables is improved.

Example 3 and examples 10 to 13 investigate the influence of the addition of sodium polyacrylate on the performance of the fruit and vegetable preservative film. By comparison of example 3 with examples 10 to 13 it can be found that: the addition of the sodium polyacrylate has little influence on the oxygen transmission of the preservative film; and with the increase of the addition of the sodium polyacrylate, the mechanical property of the preservative film is reduced. Therefore, the addition amount of the sodium polyacrylate is preferably controlled to be 2-20wt% of the addition amount of the polyethylene.

Example 18 and comparative example 3 examine the effect of the addition of zeolite, quartz and nano titanium dioxide on the performance of the fruit and vegetable preservative film. Comparative example 18 and comparative example 3 show that: the zeolite, the quartz stone and the nano titanium dioxide can improve the air permeability of the preservative film, thereby being beneficial to the preservation of fruits and vegetables wrapped in the preservative film. Meanwhile, the mechanical properties of the preservative film can be reduced to a certain extent by adding the zeolite, the quartz stone and the nano titanium dioxide.

Examples 14-16 glyceryl monostearate was added in addition to example 3. As can be seen from the detection results: the combination of the performance of the wrap films prepared in examples 14-16 is improved over that of example 3. The glyceryl monostearate can ensure that the components of the raw materials are mixed more uniformly, thereby being beneficial to improving the performance of the prepared preservative film.

Examples 17-18A milky white master batch and an antioxidant were added to example 15. The comparison of the detection results shows that: the addition of the milky white color master batch and the antioxidant has no obvious influence on the air permeability, the tensile strength and the fresh-keeping effect of the fresh-keeping film.

Examples 19-21 changed the white oil grade and, in turn, the kinematic viscosity of the white oil as compared to example 18. The analysis experiment results can find that: the kinematic viscosity is 12-75mm²The white oil/s can be used for preparing the fruit and vegetable preservative film with ideal performance. When the kinematic viscosity of the white oil is too high, certain influence is brought to the melt extrusion processing; when the kinematic viscosity of the white oil is low (namely the mark is too low), the flash point of the white oil is low, which is not beneficial to the preparation of the polyethylene preservative film.

Examples 22-23 varied the type of polyethylene compared to example 18. Through analysis, the following results can be found: the preservative film prepared by adopting the low-density polyethylene with the density of 0.927g/cm (example 22) has ideal performance. While the plastic wrap prepared by high density polyethylene (example 23) with a density of 0.954g/cm was still breathable, the oxygen transmission was significantly lower than that of the plastic wrap prepared by low density polyethylene.

Example 18 and examples 24-25 examine the effect of different blow-up and draw ratios on the performance of a preservative film in the production of a fruit and vegetable preservative film. From the results: the blowing ratio is controlled to be 2.1-2.9, and the traction ratio is controlled to be 4-5.2, so that the preservative film with good performance can be obtained.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The fruit and vegetable preservative film is characterized in that: the feed is prepared from the following raw materials in parts by weight: 50 parts of polyethylene, 40-120 parts of white oil, 1-10 parts of sodium polyacrylate, 3-12 parts of degradable master batch, 0.5-3 parts of zeolite, 0.3-2.5 parts of quartz stone and 0.5-3 parts of nano titanium dioxide.

2. The fruit and vegetable preservative film according to claim 1, characterized in that: the raw material also comprises glyceryl monostearate, and the addition amount of the glyceryl monostearate is 2-6wt% of the polyethylene.

3. The fruit and vegetable preservative film according to claim 2, characterized in that: the raw materials also comprise milky white color master batch and an antioxidant; the addition amount of the milky white color master batch is 2-6wt% of the polyethylene, and the addition amount of the antioxidant is 0.4-1wt% of the polyethylene.

4. The fruit and vegetable preservative film according to claim 3, characterized in that: the feed is prepared from the following raw materials in parts by weight: 50 parts of polyethylene, 50-100 parts of white oil, 4-8 parts of sodium polyacrylate, 5-8 parts of degradable master batch, 1-2 parts of zeolite, 0.8-1.5 parts of quartz stone, 1.2-2.5 parts of nano titanium dioxide, 1-3 parts of glyceryl monostearate, 1-3 parts of milky white master batch and 0.2-0.5 part of antioxidant.

5. Fruit according to claim 4Vegetable preservative film, its characterized in that: the kinematic viscosity of the white oil at 40 ℃ is 12-75mm²/s。

6. The fruit and vegetable preservative film according to claim 4, characterized in that: the polyethylene is low density polyethylene, and the density of the polyethylene is 0.916-0.927g/cm for carrying out the high speed cultivation.

7. The fruit and vegetable preservative film according to claim 4, characterized in that: the particle size of the zeolite is 0.2-0.8 μm, and the particle size of the quartz stone is 0.2-0.8 μm.

8. The method for preparing the fruit and vegetable preservative film according to any one of claims 1 to 7, which is characterized by comprising the following steps: the method comprises the following steps:

weighing raw materials of each component and uniformly mixing;

melting and extruding the mixed raw materials to obtain a blank;

and cooling the film, soaping and drying.

9. The use of the fruit and vegetable preservative film according to any one of claims 1 to 7, characterized in that: the fruit and vegetable preservative film is used for wrapping single-grain fresh pears.

10. The application of the fruit and vegetable preservative film according to claim 9, which is characterized in that: the method for wrapping fresh pears by the fruit and vegetable preservative film comprises the following steps: