With the continuous development of Commerce, food packaging bags become more and more important. But the safety of food is always put in the first place, how to ensure the safety of food, and how to extend the shelf life of food. Then we must solve the problem from the basic materials. Here we will introduce which materials are suitable for which food:
1、 Polyethylene film should not be used as food package for frying vegetable oil or food containing vegetable oil
In order to enhance or complement the properties of PE (polyethylene) plastic film in actual tape casting or blowing drawing, high pressure polyethylene, low pressure polyethylene and linear polyethylene are often mixed in proportion. The film is named after which substance accounts for a large proportion. For example, milk packaging film contains high-pressure polyethylene components, known as high-pressure polyethylene film. Yogurt, convenience bag packaging film contains more ingredients of low-pressure polyethylene, it is called low-pressure polyethylene plastic film.

Although PE (polyethylene) film has good air permeability (packaging fruits and vegetables has the effect of keeping water and discharging carbon dioxide), after contacting with vegetable oil, PE (polyethylene) film will quickly permeate, swell and change color. For example, packaging food containing vegetable oil will not only greatly shorten the shelf life of food, but also long-term contact with vegetable oil, PE (polyethylene) film will not only greatly shorten the shelf life of food, but also long-term contact with vegetable oil The "naphthalene" in the film will leach out and dissolve into vegetable oil, which is harmful to human health. Therefore, PE (polyethylene) film should not be used to package fried food and food containing vegetable oil, as well as melon seed, dried fruit seed and nut seed containing oil.

2、 PE plastic film under five layers co extrusion is not suitable for milk packaging
Co extrusion PE (polyethylene) plastic film packaging, the current market popular milk packaging, dairy products packaging, soy sauce, vinegar packaging is a typical co extrusion plastic film packaging. Transparent non printing vacuum or cooking bags are also used for coextruded plastic film packaging. Although the current milk packaging uses black and white co extrusion plastic film with white outside and black inside, the shelf life has been extended. However, if the three-layer coextrusion plastic film is used, due to the lack of barrier layer, it can hardly reach the shelf life marked on the package.
The five layer coextrusion with EVOH barrier layer and the plastic film coated with PVA barrier layer can prolong the shelf life, but the cost is higher. In today's market with only price competition, some enterprises use two or three layers of coextrusion black and white plastic film and symbolic PE film coated with barrier material to package milk, dairy products, soy sauce and vinegar. Then the PE (polyethylene) film mixed with black masterbatch is in direct contact with milk, dairy products, soy sauce and vinegar, and the inert carbon black pigment will penetrate (the package will be contaminated). So symbolically coated with barrier material of plastic film, can cope with the inspection and testing, but can not play a barrier role, also can not guarantee the shelf life of the contents.
At present, many PE (polyethylene) convenience bags and hand tear inner packaging bags on the market are thickened. However, many bag manufacturers add a lot of fillers to reduce the cost. The transparency and opening of the bags become worse, the strength becomes lower and the smell becomes stronger. Although the bags are printed with environmental protection and food safety signs and words, they actually do not use degradable materials, Also did not use the environmental protection ink printing, not only increased the production cost, but also increased the solvent residue, the security is also worrying.
3、 Al foil cannot be replaced by DAL vacuum aluminizing film in plastic flexible packaging
Al metal aluminum foil has bright metallic luster, non-toxic, tasteless, excellent light shielding, reflective rate up to 95%, stable at high temperature and low temperature, and does not shrink or deform in the range of 73-371 ℃; it is an excellent middle-level substrate film for high-grade packaging with good barrier, air, oxygen, moisture and fragrance retention; it is mainly used in high-grade packaging and blister packaging of drugs, moisture-proof tissue and chocolate It includes high-grade packaging of daily chemical products, sealing film of instant noodle bowl, sealing trademark of beer and champagne, paper / aluminum / plastic composite packaging of milk and milk products and juice, high-grade aroma preserving packaging of food and condiments, steaming packaging of cooked meat, grilled chicken and roast duck, moisture-proof and anti-static packaging of integrated circuit board.
Dal vacuum aluminizing film is a kind of product that more than 99.99% of high purity aluminum is deposited on the plastic film of bpet (biaxially oriented polyester), BOPP (biaxially oriented polypropylene), PVC (polyvinyl chloride), CPP (cast polypropylene), CPE (chlorinated polyethylene) plastic films under vacuum condition. The gas and oxygen resistance of aluminized film mainly depends on the substrate film itself, not the aluminum coating, which only plays a decorative role. However, the barrier properties of BOPP, PVC, CPP and CPE films are not good. Therefore, the vacuum aluminized films made from the above-mentioned substrates cannot be used for vacuum packaging. Only after the plastic films with good barrier properties are compounded or aluminized can they be vacuum packed. Bpet (biaxially oriented polyester) vacuum aluminized film can only be made into vacuum packaging, but not cooking packaging. In order to reduce the cost, it is wrong to use aluminized film instead of metal aluminum foil packaging.
The biggest feature of aluminized packaging is its excellent decoration. Therefore, the pattern design should be hollowed out as far as possible, so that the bright silver and the dazzle color after dyeing can be fully displayed. The unreasonable design of the packaging pattern, such as aluminum plating composite packaging covered with white ink or spot color ink printing, will increase the residual amount of ink and solvent, reduce the composite firmness of plastic composite film, and is not conducive to improving the printing speed, but will increase the packaging cost. It is not guaranteed that the food in the package reaches the shelf life indicated on the package.
In addition, although the vacuum aluminized plastic film has good mechanical properties, flat and bright aluminum surface, is not easy to produce pinholes, and has strong decoration, it has certain functions of gas barrier, light shielding and shielding. It can complement the disadvantages of calendered aluminum foil, such as low strength, easy to tear, easy to break when folded, easy to produce pinholes, and not resistant to acid and alkali. However, the aluminum layer of vacuum aluminized plastic film has poor water resistance, and will fall off when wet Falling and dealumination will cause delamination of composite packaging bags. In addition, the aluminum layer is too thin (the aluminum coating is only 400 μ m), that is to say, only about 1 kg of high-purity aluminum is needed for 50 000 m2 plastic film, and its shading and shielding properties are far lower than that of rolled aluminum foil (metal pure aluminum foil), so the aluminum film can not replace calendered aluminum foil in the use of plastic composite packaging substrate.
4、 Pet (polyester) film can not replace PA (nylon) film for cooking packaging
The function of cooking packaging is to kill the fungi in the food in the package through the cooking high temperature, and prolong the shelf life of the packed food; only when the high temperature is transferred to the food in the package through the packaging, the fungus will be killed. PA (nylon) film has high water vapor transmission rate, and aluminum foil is a good thermal conductor. However, the thermal conductivity of PET film with excellent insulation performance and good gas resistance is not good, and its water vapor transmission rate is very low, which can prevent part or reduce the introduction of cooking temperature; in addition, the PET film itself has high hardness and stiffness, and the air is not easy to be exhausted. Although it has excellent barrier property, it weakens the cooking sterilization effect, so PET film is only suitable Do vacuum packaging, not cooking packaging.
Using PET (polyester) film instead of PA (nylon) film to make cooking packaging or adding four layers of composite pet (polyester) film can only reduce the cost, but it has no better sterilization effect and longer shelf life than PA (nylon) / Al (metal aluminum foil) / CPP (cast polypropylene) three-layer composite cooking packaging.
5、 Paper plastic composite film packaging is not necessarily environmental protection
The packaging of paper plastic composite film is the composite packaging of paper and plastic, which is usually made by the composite processing technology of paper tape casting PE (polyethylene) and PP (polypropylene) (the processing cost of dry composite method is higher). Compared with plastic packaging, paper plastic packaging has better air permeability, poor water resistance and barrier property, so it is often used in the packaging of articles that need to release and absorb moisture, such as the inner packaging of camphor tablets, moisture-proof agent (desiccant), etc. Paper can only be heat sealed into bags after being compounded with plastics, but it is difficult to recycle or decompose naturally after compounding plastics. In addition, the raw material of paper is wood, so it is a waste of natural resources to use a large amount of paper. Therefore, some people think that paper plastic composite packaging is not reasonable than plastic packaging. It is also worth discussing whether the paper plastic composite packaging of melon seeds and dried fruits is reasonable.