TWI784310B - Active modified atmosphere fresh-keeping film for vegetable and fruit packaging and preparation method thereof - Google Patents

Abstract

An active modified atmosphere plastic wrap for fruit and vegetable packaging and a preparation method thereof. The surface of the LDPE film is modified by plasma, and coated with collagen (COL) or carboxymethyl cellulose (CMC), which becomes the modified atmosphere of the LDPE film after drying. Floor. Using this plastic wrap as the packaging of fruits and vegetables reduces the rate of gas exchange, and with the different coating concentrations of collagen (COL) or carboxymethyl cellulose (CMC), the permeability of carbon dioxide can be controlled, making the film and fruits and vegetables A gas environment with a carbon dioxide content higher than the oxygen content is formed, which reduces the increase rate of malondialdehyde (MDA) in packaged fruits and vegetables, effectively slows down the deterioration of fruits and vegetables, and prolongs the freshness period of fruits and vegetables. Taking Agaricus bisporus as an example, the shelf life can be extended from 3 days to 21 days at 4°C.

Description

Active modified atmosphere fresh-keeping film for vegetable and fruit packaging and preparation method thereof

The invention belongs to the field of food preservation, and in particular relates to a modified atmosphere preservation film for fruit and vegetable packaging and a preparation method for the film.

The post-harvest pretreatment of Agaricus bisporus is the basis for subsequent packaging, transportation and sales. If there are good packaging materials and packaging environment before transportation, combined with refrigerated storage during transportation, the shelf life of the product can be extended more effectively. , so that products are transported to further markets.

To extend the shelf life, Modified Atmosphere Packaging (MAP) and Equilibrium Modified Atmosphere Packaging (EMAP) are used.

MAP usually uses polymer materials with better barrier properties, but due to the continuous respiration of fruits and vegetables after harvest, once the oxygen concentration in the packaging is lower than 1%, it will cause anaerobic respiration to produce odor and odor, and anaerobic food-borne The growth of pathogenic bacteria (such as botulism), resulting in a decline in quality.

EMAP is to carry out micro-perforation on the MAP packaging bag, and use the respiration of fruits and vegetables and the air permeability of the packaging film to balance the gas exchange inside and outside the packaging. However, the perforated membrane will reduce the gas selectivity of the membrane and easily cause microbial contamination.

Chinese patent CN104109275A discloses a fresh-keeping packaging material with a controllable atmosphere function. The main components are inorganic substances with a mass fraction of 5-25wt%, block copolymers and polyolefin materials with a mass fraction of 2-50wt%. After the materials mixed in proportion are melt blended and granulated, they are blown into film or extruded The packaging film made by using this material as the outer packaging of fresh fruits and vegetables can provide more suitable humidity (RH80~95%) and suitable modified atmosphere packaging atmosphere of oxygen and carbon dioxide for fruits and vegetables.

Chinese patent CN109867849 discloses a modified atmosphere fresh-keeping bag for pitaya and its preparation method. The modified atmosphere fresh-keeping bag is made of low-density polyethylene resin, porous polymer, biodegradable polymer material, plasticizer, dispersant, organic It is prepared from antibacterial agent, inorganic antibacterial agent, ethylene absorption and decomposition agent, inorganic filler, antioxidant and defoamer. Compared with ordinary commercially available PE fresh-keeping bags, the prepared fresh-keeping bags can exchange gas with the outside world, automatically adjust the content and ratio of carbon dioxide and oxygen, and reduce the rotten fruit rate of dragon fruit.

Chinese patent CN109912947A provides a modified atmosphere plastic wrap for fruits and vegetables and its preparation method. The components act synergistically and have a strong bidirectional adjustment ability to oxygen and carbon dioxide, which can adjust the permeability and barrier rate of oxygen and carbon dioxide of the plastic wrap. Make the content of carbon dioxide in the plastic wrap greater than the content of oxygen, inhibit the growth of bacteria on the surface of fruits and vegetables, effectively slow down food deterioration, and prolong the freshness period of fruits and vegetables. The modified atmosphere plastic wrap includes the following components in parts by weight: 140 parts of poly 3-hydroxybutyrate-polyethylene glycol, 14 parts of cellulose acetate, 7 parts of cellulose acetate propionate, 30 parts of konjac glucomannan , 6 parts of glyceryl monostearate, 12 parts of sodium citrate, 4 parts of pyridoxal phosphate, 4.5 parts of chitosan modified silicon dioxide, 20 parts of attapulgite with a particle size of 100~200nm, 13 parts of granular Sanidine with a diameter of 50-100nm, 10 parts of iron powder with a particle size of 200-400nm, 23 parts of porous filler, 3.5 parts of antibacterial substances, and 35 parts of gelling agent.

Chinese patent CN110452509A provides a fresh-keeping film containing hydroxymethyl cellulose grafted with hydroxyl or amino carboxylic acid preservatives, which can effectively reduce the total number of bacterial colonies of meat during storage, and can effectively reduce the speed of meat weight loss and hardness reduction , Extend shelf life.

The above literature provides Active Modified Atmosphere Packaging (Active Modified Atmosphere Packaging, referred to as AMAP), is different from MAP in that AMAP does not need to fill the package with fresh air, but uses the natural breathing of fruits and vegetables to adjust the atmosphere in the package. Different from EMAP, the packaging film of AMAP does not have micropores, but actively adjusts the atmosphere to control oxygen, moisture and carbon dioxide. This is the recent development trend of fresh-keeping packaging for fruits and vegetables.

The main purpose of the present invention is to provide an active modified atmosphere plastic wrap for vegetable and fruit packaging, modify the surface of the low-density polyethylene (LDPE) film through plasma, and then coat and fix it on one of the surfaces of the film by collagen (COL) or The coating agent composed of carboxymethyl cellulose (CMC) constitutes the air-conditioning layer of the LDPE film, and is used as an active packaging film for extending the fresh-keeping period of vegetables and fruits.

Technical features of the present invention:

An active atmosphere-modified fresh-keeping film for vegetable and fruit packaging, which is composed of a polymer film and an atmosphere-modified layer fixed on one surface of the polymer film; the atmosphere-modified layer is grafted and fixed on the polymer film after drying The surface is composed of a coating agent; the coating agent is composed of collagen with a concentration of 0.5% to 5% by weight; the oxygen permeability of the active modified atmosphere plastic wrap is 2.38 to 2.67×10- 15kg. m. m-2. s-1. Pa-1, carbon dioxide permeability is 2.42~5.88×10-15kg. m. m-2. s-1. Pa-1.

An active atmosphere-modified fresh-keeping film for vegetable and fruit packaging, which is composed of a polymer film and an atmosphere-modified layer fixed on one surface of the polymer film; the atmosphere-modified layer is grafted and fixed on the polymer film after drying The surface is composed of a coating agent; the coating agent is composed of carboxymethyl cellulose with a concentration of 0.5% to 5% by weight; the oxygen permeability of the active modified atmosphere plastic wrap is 2.69 to 3.87 ×10-15kg. m. m-2. s-1. Pa-1, carbon dioxide permeability is 2.67~6.85×10-15kg. m. m-2. s-1. Pa-1.

A method for preparing an active-modified-atmosphere plastic wrap for fruit and vegetable packaging, comprising: subjecting a polymer film to a plasma treatment step to modify its surface to be hydrophilic; applying a coating agent to the surface of the modified polymer film, The coating agent is composed of 0.5% to 5% by weight of collagen or 0.5% to 5% by weight of carboxymethyl cellulose; and the coating is dried and grafted after coating It is fixed on one of the surfaces of the polymer film to form an atmosphere-modifying layer.

Efficacy of the present invention:

The surface of LDPE film is modified by plasma and coated with collagen (COL) or carboxymethyl cellulose (CMC) to make a film with an atmosphere-modified layer, which is used as a new type of active packaging to extend the shelf life of fruits and vegetables (especially Agaricus bisporus).

The permeability of the film to oxygen and carbon dioxide is significantly different from that of LDPE films not coated with collagen (COL) or carboxymethyl cellulose (CMC). The film of the present invention reduces the exchange rate of gas, and with the different coating concentrations of collagen (COL) or carboxymethyl cellulose (CMC), the permeability of carbon dioxide can be controlled, and the permeability of oxygen remains lower than Steady low levels of carbon dioxide permeability.

The film with the atmosphere-modifying layer of the present invention can adjust the permeability and barrier rate of oxygen and carbon dioxide, so that a gas environment with a carbon dioxide content higher than the oxygen content is formed between the film and the fruits and vegetables, and the malondialdehyde (MDA) of the packaged fruits and vegetables is reduced. Increase the speed, effectively slow down the deterioration of fruits and vegetables, and extend the freshness period of fruits and vegetables. Taking Agaricus bisporus as an example, the shelf life can be extended from 3 days to 21 days at 4°C.

Plasma treatment is a fast, effective and environmentally friendly method without the use of organic solvents Plasma modification technology can generate new functional groups on the surface of the film, improve the hydrophilicity of the film, and then collagen (COL) or carboxymethyl cellulose (CMC) can be grafted and fixed on the film. The film-making method of the present invention is easy to operate, fast and environmentally friendly, and does not use other adhesives or other compounds for fixing collagen (COL) or carboxymethyl cellulose (CMC).

Collagen (COL) or carboxymethyl cellulose (CMC) is used as the air-conditioning layer of the LDPE film to simplify the air-conditioning components of the film, and the selective air-conditioning effect is specific and significant.

10: Polymer film

20: Modified atmosphere layer

[Fig. 1] Schematic diagram of the structure of the active modified atmosphere plastic wrap of the present invention.

[Fig. 2] The experimental results of the present invention, about the appearance image of Agaricus bisporus.

[Fig. 3] Browning curve graph depicting the browning effect of uncoated and collagen (COL)-coated LDPE films on Agaricus bisporus.

[FIG. 4] Browning graph depicting the browning effect of uncoated and CMC-coated LDPE films on Agaricus bisporus.

[Fig. 5] Hardness bar graph depicting the effect of uncoated and coated collagen (COL) and carboxymethyl cellulose (CMC) coated LDPE films on the hardness of Agaricus bisporus.

[FIG. 6] Lipid peroxidation bar graph depicting the effect of uncoated and collagen (COL)-coated and carboxymethylcellulose (CMC)-coated LDPE films on lipid peroxidation of Agaricus bisporus.

As shown in Figure 1, the legend is drawn according to the proportion and size suitable for explanation, not according to the proportion of the actual component, so please describe first. The active modified atmosphere fresh-keeping film of the present invention includes a polymer film 10 , and a coating agent is grafted and fixed on the surface of the polymer film 10 to form a modified atmosphere layer 20 . said The polymer film is preferably a polyethylene (PE) film, or a low density polyethylene (LDPE) film. The film thickness is 0.03mm~0.04mm. The coating agent is composed of collagen (COL) with a concentration of 0.5% to 5% by weight, or carboxymethyl cellulose (CMC) with a concentration of 0.5% to 5% by weight; the coating agent After coating, it is dried and then grafted and fixed on one surface of the film 10 .

The preparation method of the active modified atmosphere fresh-keeping film of the present invention comprises: preparing a polymer film; carrying out surface hydrophilic modification of the polymer film through a plasma treatment step; applying a A film coating agent, the film coating agent is composed of collagen (COL) with a concentration of 0.5% to 5% by weight, or carboxymethyl cellulose (CMC) with a concentration of 0.5% to 5% by weight ; The film coating agent is dried and grafted and fixed on one of the surfaces of the film to form an air-conditioning layer after coating.

Effect example:

Experimental sample: general LDPE film, and the present invention has the LDPE film of atmosphere-modulating layer, and the collagen protein (COL) in the coating agent, carboxymethyl cellulose (CMC) weight percent concentration is respectively 0.5% (P-0.5COL , P-0.5CMC), 1% (P-1COL, P-1CMC), 3% (P-3COL, P-3CMC), 5% (P-5COL, P-5CMC).

experimental method:

(1) Measure the oxygen and carbon dioxide permeability of the experimental samples with a gas permeability rate tester.

(2) Hold three Agaricus bisporus on a plastic tray, cover and seal the plastic tray and all Agaricus bisporus on the plastic tray and the above-mentioned experimental samples of the present invention. Refrigerate at 4°C for 21 days. Afterwards, the appearance, browning degree and hardness of each group of mushrooms were observed.

Experimental results:

The gas permeability rate tester was used to measure the oxygen and carbon dioxide permeability of the experimental samples, and the results are shown in Table 1 below. The oxygen and carbon dioxide permeability of the film of the present invention are lower than those of common LDPE films. As the coating concentration of collagen (COL) and carboxymethyl cellulose (CMC) increased, the carbon dioxide permeability also increased, but the oxygen permeability did not change much. This result indicates that the film of the present invention is a gas-selective film and can control the permeability of carbon dioxide.

According to Table 1, the film coated with collagen (COL): the oxygen permeability is between 2.38~2.67×10 ^-15 kg. m. m ^-2 . s ^-1 . Pa ^-1 .

Carbon dioxide permeability ranges from 2.42 to 5.88×10 ^-15 kg. m. m ^-2 . s ^-1 . Pa ^-1 .

Films coated with carboxymethyl cellulose (CMC): the oxygen permeability is between 2.69~3.87×10 ^-15 kg. m. m ^-2 . s ^-1 . Pa ^-1 .

Carbon dioxide permeability is between 2.67~6.85×10 ^-15 kg. m. m ^-2 . s ^-1 . Pa ^-1 .

This polymer film utilizes the side chain polar groups of carboxymethylcellulose (CMC) to interact with _CO2 gas. The polymer film 10 allows CO ₂ to permeate into the film structure relatively quickly through the amine carrier of collagen (COL).

Table 1

As shown in Figure 2, after 21 days of storage, it can be observed that the appearance of Agaricus bisporus in the P-1.0 COL and P-1.0 CMC groups is the best. Agaricus bisporus packaged in general LDPE showed very obvious browning on the third day.

As shown in Figure 3 and Figure 4, the degree of browning of Agaricus bisporus will affect the degree of acceptance by consumers. P-1.0 COL and P-1.0 CMC have the lowest degree of browning, which is consistent with the appearance results in Figure 2.

As shown in Figure 5, firmness is an important factor affecting quality, reflecting the changes in moisture and metabolism of mushrooms. In all groups, the hardness value decreases with the increase of storage time, P-1.0 COL and P-1.0 CMC have a lower hardness decrease rate in all groups, and the hardness decrease rate of P-1.0 COL 61.09% is the lowest, showing that the film coated with 1% collagen can better maintain the tissue hardness of Agaricus bisporus during storage. The decrease rate of hardness in P-3.0 CMC and P-5.0 CMC groups was significantly higher than that in the control group (LDPE), which were 89.33% and 92.59% respectively.

As shown in Figure 6, lipid peroxidation is an oxidative change of polyunsaturated fatty acids in cell membranes, which can produce a variety of degradation products. Malondialdehyde (MDA) is one of the products of lipid peroxidation and is widely considered as an important indicator of cell oxidative damage. MDA increased continuously during storage, and P-1.0 COL after plasma treatment significantly slowed down the increase of MDA content after 21 days of storage. speed. Reducing MDA content can further prevent lipid oxidation while maintaining the integrity of mushroom cell membranes.

According to the above experimental results, the optimal weight percentage concentration of collagen (COL) and carboxymethyl cellulose (CMC) is 0.5%~1%.

Although the present invention takes Agaricus bisporus as an experimental example, it is not limited thereto. For example, the film of the present invention is suitable for all fruits and vegetables that can breathe naturally during packaging and transportation.

10: Polymer film

20: Modified atmosphere layer

Claims (4)

An active atmosphere-modified fresh-keeping film for vegetable and fruit packaging, which is composed of a polymer film and an atmosphere-modified layer fixed on one surface of the polymer film; the atmosphere-modified layer is grafted and fixed on the polymer film after drying The surface is composed of a coating agent; the coating agent is composed of collagen with a concentration of 0.5% to 5% by weight; the oxygen permeability of the active modified atmosphere plastic wrap is 2.38 to 2.67×10- 15kg. m. m-2. s-1. Pa-1, carbon dioxide permeability is 2.42~5.88×10-15kg. m. m-2. s-1. Pa-1. An active atmosphere-modified fresh-keeping film for vegetable and fruit packaging, which is composed of a polymer film and an atmosphere-modified layer fixed on one surface of the polymer film; the atmosphere-modified layer is grafted and fixed on the polymer film after drying The surface is composed of a coating agent; the coating agent is composed of carboxymethyl cellulose with a concentration of 0.5% to 5% by weight; the oxygen permeability of the active modified atmosphere plastic wrap is 2.69 to 3.87 ×10-15kg. m. m-2. s-1. Pa-1, carbon dioxide permeability is 2.67~6.85×10-15kg. m. m-2. s-1. Pa-1. A method for preparing an active-modified-atmosphere plastic wrap for fruit and vegetable packaging as described in Claim 1, comprising: subjecting the polymer film to a plasma treatment step for surface hydrophilic modification; Prepare the coating agent, the coating agent is composed of collagen with a concentration of 0.5% to 5% by weight; and the coating agent is dried and grafted and fixed on one of the surfaces of the polymer film after coating The atmosphere-modifying layer is formed. A method for preparing an active-modified-atmosphere plastic wrap for fruit and vegetable packaging as described in Claim 1, comprising: The polymer film is subjected to a plasma treatment step to carry out surface hydrophilic modification; the surface of the modified polymer film is applied with a coating agent, and the coating agent is composed of 0.5% to 5% by weight The carboxymethyl cellulose is formed; and the film coating agent is dried and grafted and fixed on one of the surfaces of the polymer film to form the air-conditioning layer.

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