With the rapid development of science and technology, more and more plastic products have been widely used in packaging. In particular, there has been a breakthrough in the field of food preservation. Functional cling film: Although the traditional film can play a role in packaging, has a certain effect of preservation, but it has obviously failed to meet the preservation needs of the modern market, therefore, a large number of new cling film was developed. These functional cling films not only have the effect of preventing moisture from evaporating in the conventional film, but also have a simple effect of controlling the gas, and further increase the freshness of fruits and vegetables. Ethylene Adsorption Film: Ethylene Adsorption Film is used to remove harmful ethylene gas. Plastic film (especially LDPE) is mixed with gas-adsorption porous material such as tuff and zeolite, quartz stone and silica, clay mineral, stone powder and other fine powders. Most can absorb ethylene or far infrared radiation. The mechanism of ethylene adsorption is that the pores on the surface of the porous inorganic material can capture ethylene, and even in the case of high moisture, the water molecules present in the pore can be replaced with ethylene. However, the amount of gas adsorbent added is 3% to 5% because the adsorption capacity of ethylene gas is limited. At present, in the foreign countries, the use of titanite-based films is mainly due to the addition of silicic anhydride-based ceramics. Anti-dew film: The cling film used for fruits and vegetables is generally a film made of a resin with high gas permeability such as low density polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer, and polyvinyl chloride, but When the water vapor produced by these film-packed fruits and vegetables is condensed on the inner surface of the film, not only the transparency thereof is poor, but also the water droplets gather, so that the bacteria proliferate quickly and the fruits and vegetables are corrupted. The solution to this problem is the prevention of dew film. The anti-corrosion film uses an interfacial agent to treat the inner surfaces of the above-mentioned materials, such as polyethylene, polypropylene, and polystyrene, to absorb excess moisture, and to appropriately maintain the humidity inside the package. The purpose of preservation. The substance that can be used both as a food additive and as a demulsifier is a fatty acid ester. Antibacterial film: The antibacterial film is a mixture of silver zeolite with antibacterial properties. The silver zeolite is replaced with sodium ions in the crystalline structure of silver and zeolite with antibacterial properties, or silver ions and synthetic loose zeolite made of aluminum and silicon. mixture. This film can inhibit the proliferation of bacteria to some extent, play a role in preservation. Fresh-keeping sheets: The single packaging of fruits and vegetables uses plastic platters and thin-film composite products, so the functional sheet placed on the platter body or above has a fresh-keeping function. These sheets often have one or more functions such as humidity control, dew proofing, ethylene gas absorption, and antibacterial. Among them, moisture-adsorption and water-absorption is a multi-layer structure composed of a superabsorbent resin and a non-woven fabric, a thin paper, and a water-absorbing polymer; the absorption of ethylene gas mostly utilizes the porosity of activated carbon; the antibacterial property is due to the addition of a sheet Silver zeolite and other inorganic substances with antibacterial properties or antibacterial ingredients extracted from plants. Preservative: Since the absorption of the functional film that absorbs ethylene gas is limited by the amount of use, preservatives that adsorb ethylene gas are widely used. Packaging fruits and vegetables together with preservatives can achieve a certain purpose of inhibiting ethylene gas. Currently used preservatives often use oxidants such as potassium permanganate, gas adsorbents such as activated carbon and mineral powder, and palladium catalysts. Refrigerant: As the preservation of fruits and vegetables at low temperatures is conducive to maintaining freshness, the use of cold storage materials has become an important means of preservation technology. An elastic gel-like material containing a polymer obtained by polymerizing and crosslinking polyacrylic acid as a main component is a high-performance cold storage material. If you use it with a heat shield, it works better. New type of fresh-keeping trays: The fresh-keeping trays are obtained by heating the continuous extruded original plate (thermoplastic resin sheet) through vacuum forming and stamping. In addition to preventing fresh food from being damaged, the use of a tray also has a certain degree of thermal insulation. The so-called new tray is a molded product obtained by adding a functional film or a long fiber nonwoven fabric to an original sheet. This kind of tray adds functions such as adjusting humidity, controlling gas content, preventing mould propagation, etc. on the basis of original functions, so it can maintain the freshness of vegetables and fruits. This kind of tray can reduce the change of packing size caused by absorbing moisture.
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