Material Selection For Food Packaging Bags

- Jun 18, 2019-

As business continues to evolve, food packaging bags are becoming more and more important. But the safety of food is always 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 is a brief introduction of which material is suitable for which food:

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1. Polyethylene film should not be used as vegetable oil fried food or food packaging containing vegetable oil.


In the actual casting or drawing process of PE (polyethylene) plastic film, in order to enhance or complement the performance of the film, high-pressure polyethylene, low-pressure polyethylene and linear polyethylene are often used in proportion. Which kind of substance is a large proportion, the film is named after the substance. For example, milk packaging films containing high-pressure polyethylene have many components and are called high-pressure polyethylene films. Yogurt and convenience bag packaging film contains low-pressure polyethylene, which is called low-pressure polyethylene plastic film.


Although PE (polyethylene) preservative film has good air permeability (packaging fruits and vegetables have the effect of retaining moisture and emitting carbon dioxide gas), PE (polyethylene) film will quickly penetrate, swell, discolor, such as packaging after contact with vegetable oil. Vegetable oil-containing foods not only greatly shorten the shelf life of foods, but also long-term exposure to vegetable oils. The "naphthalene" in PE (polyethylene) film will be dissolved in vegetable oil, which is harmful to human health, so PE (polyethylene) film It should not be used to package fried foods and foods containing vegetable oils, nor to package foods such as melon seeds, dried fruit seeds, and nut seeds.



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The second and fifth layers of the same PE plastic film should not be made into milk packaging.


Co-extruded PE (polyethylene) plastic film packaging, the current popular milk packaging, dairy packaging, soy sauce, vinegar packaging, etc. is a typical co-extruded plastic film packaging. A clear, non-printable vacuum or retort pouch, also a package of coextruded plastic film. Although the current milk packaging uses a white-and-white black-and-white coextruded plastic film, the shelf life has been extended. However, if a three-layer coextruded plastic film is used, the shelf life indicated on the package is rarely achieved due to the lack of a barrier layer.


A five-layer co-extruded and coated PVA (polyvinyl alcohol) barrier layer of plastic film with an EVOH (ethylene/vinyl alcohol copolymer) barrier layer can extend the shelf life but at a higher cost. In today's market where there is only price competition, some companies use two or three layers of co-extruded black and white plastic film and a symbolic PE film coated with barrier material to package milk, dairy products and soy sauce and vinegar. Then the PE (polyethylene) film with the black color masterbatch directly contacts the milk, dairy products and soy sauce, vinegar, then the inert carbon black pigment will penetrate (the package will be contaminated). Then the plastic film symbolically coated with the barrier material can cope with the inspection and test, but it can not get the barrier effect, and can not guarantee the shelf life of the contents.


Many PE (polyethylene) convenience bags and continuous tearing inner bags on the market are thickened, but many bag manufacturers have added a large amount of fillers to reduce the cost, and the transparency and opening of the bags are deteriorated. The intensity is low and the smell is large. Although the label and the words of environmental protection and food safety are printed on the bag, the degradation material is not actually used, and the environmentally friendly ink is not used for printing, which not only increases the production cost but also increases the production cost. Solvent residue and safety are also worrying.


Third, DAL vacuum aluminum-plated film in plastic flexible packaging can not replace Al metal aluminum foil


Al metal aluminum foil has shiny metallic luster, non-toxic, odorless, excellent light-shielding, reflection rate up to 95%, stable at high temperature and low temperature, no shrinkage deformation in the range of 73-371 °C; good barrier property, gas barrier It is an excellent middle-layer substrate film for high-grade packaging; it is used for high-grade packaging and blister packaging of medicines, moisture-proof and fragrant paper for cigarettes, high-grade packaging for chocolate, and anti-seepage for daily chemical products. Leakable packaging, sealing film for instant noodle bowls, sealing trademark for beer and champagne, paper/aluminum/plastic composite packaging for milk and dairy products, juice, high-grade fragrance packaging for food and condiments, cooked meat, pheasant, roast duck, etc. The cooking package, the moisture-proof packaging of the integrated circuit board, and the anti-static packaging.


DAL vacuum aluminized film is made by vacuum evaporation of 99.99% or more of high-purity aluminum to BPET (biaxially stretched polyester), BOPP (biaxially oriented polypropylene), PVC (polyvinyl chloride) ), CPP (cast polypropylene), CPE (chlorinated polyethylene) plastic film products. The gas barrier and oxygen barrier of the aluminized film mainly depend on the aluminum film base film itself, instead of the aluminum plating layer, and the aluminum plating layer only serves as a decoration. The barrier properties of BOPP (biaxially oriented polypropylene), PVC (polyvinyl chloride), CPP (cast polypropylene), CPE, etc. are not good, so the vacuum aluminized film made using the above substrate cannot be vacuum packed. Vacuum packaging can only be done after compounding or aluminizing a plastic film with good barrier properties. BPET (biaxially stretched polyester) vacuum aluminized film can only be made in vacuum packaging, but it can not be used in cooking packaging. In order to reduce costs, it is wrong to use aluminum-plated film instead of metal foil.


The biggest feature of aluminized packaging is its excellent decoration. Therefore, the pattern design should be hollowed out as much as possible so that the bright silver and the dyed color can be fully displayed. The packaging pattern with unreasonable design is selected, such as: aluminized composite packaging printed with white ink or spot color ink, thus increasing the residual amount of ink and solvent, reducing the composite firmness of the plastic composite film, and also disadvantageous Increasing the speed of printing will increase the cost of packaging. It is not possible to ensure that the food in the package reaches the shelf life indicated on the package.


In addition, although the vacuum aluminum-plated plastic film has good mechanical properties, the aluminum-plated surface is flat and bright, is not easy to produce pinholes, has strong decorative properties, and has certain functions of gas barrier, light shielding and shielding, and can complement the calendered aluminum foil with low strength and easy tearing. It is easy to break when folded, easy to produce pinholes, and is not resistant to acid and alkali. However, the aluminum layer of vacuum aluminum-plated plastic film has poor water resistance, and will fall off when wet, and the aluminum stripping will cause the opening of the composite bag. In addition, the aluminum layer is too thin (the aluminum plating layer is only 400 Å), which means that the plastic film coated with 50,000 m2 only needs about 1 kg of high-purity aluminum, and its shading and shielding performance is much lower than that of the rolled aluminum foil (metal pure aluminum foil). Aluminized film is not a substitute for rolled aluminum foil in the use of substrates for plastic composite packaging.


Fourth, PET (polyester) film can not replace PA (nylon) film for cooking packaging


The function of the retort packaging is to kill the fungi in the food in the package by the high temperature of cooking, and to extend the shelf life of the food; the fungus is only killed if the high temperature is transmitted to the package by the package. The PA (nylon) film has a high water vapor transmission rate, and the metal aluminum foil is a good thermal conductor. The PET (polyester) film with excellent insulation properties and good gas barrier properties has poor thermal conductivity, and its water vapor transmission rate is low, which can prevent partial or reduced cooking temperature introduction; in addition, PET (polyester) film The hardness and stiffness are high, and the air is not easy to be exhausted. Although it has excellent barrier properties, it reduces the effect of retort sterilization. Therefore, PET (polyester) film should only be vacuum-packed and cannot be cooked.


Replacing PA (nylon) film with PET (polyester) film to make retort packaging or adding four-layer retort packaging of composite PET (polyester) film can only reduce the cost, but there is no PA (nylon) / AL (metal aluminum foil) / CPP (casting polypropylene) three-layer composite cooking package has good bactericidal effect and long shelf life.


5. Paper-plastic composite film packaging is not necessarily environmentally friendly.


The packaging of paper-plastic composite film is a composite packaging of paper and plastic, which is usually compounded by a composite processing process of paper-cast PE (polyethylene) and PP (polypropylene) (higher processing cost by dry composite method). Paper-plastic packaging is more breathable than plastic packaging, and has poor water resistance and barrier properties. Therefore, it is often used for packaging that requires release and moisture absorption, such as inner packaging of camphor tablets, moisture-proofing agent (drying agent), and the like. The paper can be heat-sealed only after the plastic is compounded, but the composite plastic is not easy to recycle or naturally decompose. In addition, the raw material of the paper is wood, and mass use is also a waste of natural resources. Therefore, some people think that paper-plastic composite packaging is not reasonable compared to plastic packaging. Whether the paper-plastic composite packaging of melon seeds and dried fruit foods is reasonable is also worth exploring.