In simple modified atmosphere packaging, the main factors influencing the gas composition in the bag include the respiration rate, weight, breathability, thickness, surface area and storage temperature of the film, humidity, and the volume of the bag. For this reason, films for simple atmosphere packaging are usually made of low-density polyethylene, polypropylene, polystyrene, cellulose acetate, etc., which have good air permeability.
Polyethylene: Low-density polyethylene with a density of 0.91-0.93 is mainly used because polyethylene is inexpensive, chemically stable, and has suitable air permeability. However, poor water vapor permeability will condense small droplets. Anti-coagulation technology has been developed. Second, low-density polyethylene is less transparent. Medium and high density polyethylene are less transparent.
Polypropylene: Polypropylene has better transparency than polyethylene, biaxially oriented polypropylene has good elasticity, and air permeability is slightly lower than that of polyethylene. Water vapor permeability is similar to polyethylene. Anti-coagulation technology has also been developed and is suitable for packaging leafy vegetables. Polystyrene: suitable for breathability, good transparency, gloss, good water vapor permeability, suitable for packaging fresh fruit. There are also anti-coagulation films, suitable for packaging lettuce and other leaves and mushrooms.
Polyvinyl chloride: Polyvinyl chloride is highly transparent, and fruit and vegetable packaging usually uses biaxially stretched polyvinyl chloride. By improving the airtightness, there is the prevention of water vapor and aroma overflow, and it is suitable for food packaging materials. Fruit and vegetable packaging use soft and flexible PVC film.
Polybutadiene: Polybutadiene shows good brightness, softness, good stretchability, and high tensile strength. Oxygen, carbon dioxide, water vapor permeability is good, with good properties of fruit and vegetable packaging materials. In order to prolong the storage period, people have developed new films for fruit and vegetable preservation with other functions.
Inorganic material-containing films: Mostly inhibit the ripening of fruits and vegetables while adsorbing, decomposing or excluding ethylene. Inorganic porous materials, such as zeolites, and clay workers are often added to plastic films (especially low-density polyethylene). Ethylene is adsorbed through pores on the surface of the inorganic material. When the humidity is high, water in the pores is also replaced with ethylene. However, basic research is not enough. Such as: whether to absorb ethylene or discharge ethylene to keep fresh.
Anti-coagulation (water beads) film: The respiration of fruits and vegetables will make the water droplets condense on the film. This is one of the reasons for the rot of fruits and vegetables. The active agent is used to treat the inner surface of the film to prevent condensation. This not only looks beautiful, but also extends the storage period. This type of anti-condensation film is mainly made of polypropylene, polyethylene, polybutadiene, etc. The film not only contains a moisture conditioner to absorb excessive moisture to maintain a proper humidity, but also added a bactericide such as hinokitiol. Antibacterial film: This is a film containing silver zeolite. It uses the antibacterial effect of silver ions for preservation purposes. That is, a layer of silver zeolite is coated on the non-woven fabric to regulate moisture and inhibit the growth of microorganisms.
Microporous plastic film: Use a laser, acupuncture, etc. to open micro-holes with a diameter of 50-100 μm on the plastic film to adjust its permeability. This film is suitable for packaging sliced ​​vegetables, onion, spinach, cauliflower and so on. This kind of microporous plastic film is mostly made of polypropylene with good transparency to achieve the best packaging effect. However, people are worried that when the temperature rises, the fruits and vegetables will produce water droplets that will clog the micropores. Therefore, they need to be used together with the humidity-controlling material.
The combination of vacuum pre-cooling and simple modified atmosphere packaging controls the composition of the ambient gas. The specific method is to affix the film on the container part, put the fruits and vegetables, vacuum precooling and then return to normal pressure with the mixed gas to form a low oxygen, high carbon dioxide environment. Due to the gas permeability of the film, the gas exchanges inside and outside the container to form a simple air-conditioned state. Experts predict that this is a technology developed on the basis of vacuum precooling (which has been popularized). In the area of ​​circulation can be used thin film, laminated corrugated carton packaging form.
Due to the low price of plastic packaging, people have great expectations for low-temperature circulation and simple atmosphere packaging technology.
Polyethylene: Low-density polyethylene with a density of 0.91-0.93 is mainly used because polyethylene is inexpensive, chemically stable, and has suitable air permeability. However, poor water vapor permeability will condense small droplets. Anti-coagulation technology has been developed. Second, low-density polyethylene is less transparent. Medium and high density polyethylene are less transparent.
Polypropylene: Polypropylene has better transparency than polyethylene, biaxially oriented polypropylene has good elasticity, and air permeability is slightly lower than that of polyethylene. Water vapor permeability is similar to polyethylene. Anti-coagulation technology has also been developed and is suitable for packaging leafy vegetables. Polystyrene: suitable for breathability, good transparency, gloss, good water vapor permeability, suitable for packaging fresh fruit. There are also anti-coagulation films, suitable for packaging lettuce and other leaves and mushrooms.
Polyvinyl chloride: Polyvinyl chloride is highly transparent, and fruit and vegetable packaging usually uses biaxially stretched polyvinyl chloride. By improving the airtightness, there is the prevention of water vapor and aroma overflow, and it is suitable for food packaging materials. Fruit and vegetable packaging use soft and flexible PVC film.
Polybutadiene: Polybutadiene shows good brightness, softness, good stretchability, and high tensile strength. Oxygen, carbon dioxide, water vapor permeability is good, with good properties of fruit and vegetable packaging materials. In order to prolong the storage period, people have developed new films for fruit and vegetable preservation with other functions.
Inorganic material-containing films: Mostly inhibit the ripening of fruits and vegetables while adsorbing, decomposing or excluding ethylene. Inorganic porous materials, such as zeolites, and clay workers are often added to plastic films (especially low-density polyethylene). Ethylene is adsorbed through pores on the surface of the inorganic material. When the humidity is high, water in the pores is also replaced with ethylene. However, basic research is not enough. Such as: whether to absorb ethylene or discharge ethylene to keep fresh.
Anti-coagulation (water beads) film: The respiration of fruits and vegetables will make the water droplets condense on the film. This is one of the reasons for the rot of fruits and vegetables. The active agent is used to treat the inner surface of the film to prevent condensation. This not only looks beautiful, but also extends the storage period. This type of anti-condensation film is mainly made of polypropylene, polyethylene, polybutadiene, etc. The film not only contains a moisture conditioner to absorb excessive moisture to maintain a proper humidity, but also added a bactericide such as hinokitiol. Antibacterial film: This is a film containing silver zeolite. It uses the antibacterial effect of silver ions for preservation purposes. That is, a layer of silver zeolite is coated on the non-woven fabric to regulate moisture and inhibit the growth of microorganisms.
Microporous plastic film: Use a laser, acupuncture, etc. to open micro-holes with a diameter of 50-100 μm on the plastic film to adjust its permeability. This film is suitable for packaging sliced ​​vegetables, onion, spinach, cauliflower and so on. This kind of microporous plastic film is mostly made of polypropylene with good transparency to achieve the best packaging effect. However, people are worried that when the temperature rises, the fruits and vegetables will produce water droplets that will clog the micropores. Therefore, they need to be used together with the humidity-controlling material.
The combination of vacuum pre-cooling and simple modified atmosphere packaging controls the composition of the ambient gas. The specific method is to affix the film on the container part, put the fruits and vegetables, vacuum precooling and then return to normal pressure with the mixed gas to form a low oxygen, high carbon dioxide environment. Due to the gas permeability of the film, the gas exchanges inside and outside the container to form a simple air-conditioned state. Experts predict that this is a technology developed on the basis of vacuum precooling (which has been popularized). In the area of ​​circulation can be used thin film, laminated corrugated carton packaging form.
Due to the low price of plastic packaging, people have great expectations for low-temperature circulation and simple atmosphere packaging technology.
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