Materials used for food packaging must have appropriate barrier properties, such as oil and fat foods require high oxygen barrier and oil resistance, dry foods require high moisture resistance, aromatic foods require high resistance and odor, fruits, vegetables and fresh foods require packaging There is a certain degree of oxygen, carbon dioxide and water vapor permeability, but at the same time, there must be good mechanical properties, including the material's tensile strength, tear resistance, impact resistance, etc.; have a good chemical stability, There should be no chemical reaction with the food inside to ensure food safety. In addition, it also has a higher temperature resistance, suitable for high temperature sterilization of food and low temperature storage and other characteristics.
At present, new high-barrier plastics have been widely used abroad, and domestic technology has also been introduced. The use of high-strength, high-barrier plastics can not only improve the protection of foods, but also reduce the amount of plastics used when packaging the same amount of food, and can even be reused. For processed foods that require high barrier protection, they are generally packaged in composite materials. In multilayer composites, there must be more than one layer of high barrier material. Currently used in China high barrier materials are aluminum foil, nylon, polyester, polyvinylidene chloride and so on. With the increase in food requirements for protection, more barrier ethylene-vinyl alcohol copolymers, polyvinyl alcohol, etc. have also begun to apply. PEN developed by developed countries and with a small amount of applications will bring great changes to food packaging in the new century.
At present, in many food packaging materials, plastic products and composite packaging materials play a decisive role. However, due to the defects of plastic materials, such as environmental pollution, the overall temperature resistance and barrier properties are not as good as those of metals. Glass containers, etc. Therefore, the rapid development of the food industry has raised new issues for the chemical industry, especially the plastics industry. This is to improve the properties of existing plastics, develop new varieties, increase their strength and barrier properties, and reduce their usage (thick-walled); At the same time, it must be easy to reuse, sort and recycle to protect the environment.
Inorganic high barrier microwave food packaging materials will become the new favorite. Because the packaging made of aluminum foil and some plastic composite materials has defects that are not transparent, easy to recycle, and cannot be used for microwave processing, the SiOX plating material developed in recent years can be used as a substitute. SiOX is a thin layer of silicon oxide on PET, PA, PP and other substrates. It not only has better barrier properties, but also has excellent adaptability to the atmospheric environment. Its barrier property is almost independent of the ambient temperature and humidity. Impact of change. SiOX coating has high barrier property, high microwave transmittance, and transparency, and can be used for soft packaging such as high-temperature cooking and microwave processing, and can also be used as a packaging container for beverages and edible oils. The cost of SiOX coating is high, and large-scale production technology is still imperfect. At present, China has begun a certain amount of research, and a few developed countries have begun to apply.
The application of active packaging technology will become a trend. Active packaging technology includes the interaction between gas and food inside the package. Active packaging can effectively maintain the nutrition and flavor of foods. Due to advances in materials science, biological sciences, and gas packaging, active packaging technology has developed rapidly in recent years. Oxygen in the remaining space of the packaging will accelerate the oxidation of foods, and an oxygen-scavenging active packaging system has emerged. In the 1970s, deoxidizers began to be used for food packaging. Among them, iron-based deoxidizers were a class of deoxidizers that developed rapidly. Later, nitrite-based systems, enzyme-catalyzed systems, organic deoxidizers, and photo-deoxidizers were developed. and many more. Another example is an active packaging system that can produce sterilant, including a sterilizing system such as ethanol, which absorbs food-grade ethanol onto a carrier and stores it in a food bag to make the food sterilized for a long period of time. The system of the combination of active sterilization material and packaging material is to add sorbitol, sorbate, sodium benzoate, silver zeolite and other substances to the materials used to make the packaging containers, and then to form and process the containers to release them slowly. Sterilized active ingredients.
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