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Review on the development of plastic flexible packaging for food at home and abroad (II)

III progress in new technology of plastic flexible packaging for food in June 2005, a British company successfully developed a new type of plastic food packaging, which has both passive and active barrier functions, and can effectively inhibit the infiltration of oxygen. Even after the cooking of food bags, the effect will not be weakened. The new packaging can not only prolong the storage period of the packaged food, but also directly use the microwave oven for heating, which is especially suitable for the packaging of convenience food. This new package is made of 6 layers of different materials. The first layer is polypropylene, a polymer material with high oil resistance. The second layer and the fourth layer are adhesive, between which is the oxygen resistant polymer material EVOH. Before unpacking, check whether the outside of the box is damaged (passive barrier). The fifth layer is deaerator gb/t 2101-2008 (general provisions for acceptance, packaging, marking and quality certificate of section steel); The mixture, called active barrier, can not only prevent the entry of foreign oxygen molecules, but also absorb the oxygen in the package. Finally, there is a layer of polypropylene material. Polypropylene is an ideal material for manufacturing heating containers for dairy products. During the high-temperature sterilization process of EVOH material, the barrier function is reduced due to water immersion. After 50 days, the product may change color and taste. In the new packaging, the deoxidizer can remain active even in the presence of water, thus ensuring the shelf life of the food

Troy, Mississippi, United States has adopted the method of putting a layer of plastic film in the conventional packaging bag, and initially received good results. The film contains a chemical called amosorb that removes oxygen from the bag- Repeated experiments for a long time show that the food stored in the new fresh-keeping bag can achieve the effect of long-term preservation. A similar study is being carried out by Wayne Hendrix of Australia. Scientists use the method of filling mixed chemicals into plastic bags, but do not remove oxygen, but eliminate the gas in the bags that promotes the ripening and deterioration of fruits, so as to keep the fruits fresh for a long time. The Australian research team is also conducting a test of a deoxidizing chemical. The physical properties of the substance are similar to amosorb, but the fresh-keeping effect is better. It is said that the substance was in a dormant state before it was irradiated by a special light wave. When it was irradiated by a light wave, its chemical molecules began to become active. In other words, there is no need to carry out complex deoxidization treatment when packaging food, as long as special light waves are used in the last process of packaging food

in order to prevent this, German scientists have developed an antibacterial plastic food packaging material by using medical expertise to prevent the reproduction of these uninvited guests. This packaging uses the latest surface coating technology to add a layer of anti-corrosion materials on the plastic packaging film to replace the preservatives added in food and further improve the safety of food packaging. This kind of coating can be realized by using composite resin as base material and special technology. It is said that this new technology is an important change in food packaging. It can prevent food mildew without food preservatives

Canadian toxin alert company has developed a new packaging material that can detect disease bacteria. The material can detect Salmonella, Campylobacter, Escherichia coli 0157 and Listeria. Discoloration reaction occurs when packaging materials contact contaminated food. The packaging material can also be used to detect the protein characteristics of pests or genetically engineered foods. Component 80% is polymer film, the rest is metal and sheet

France has introduced a new packaging film processed from ordinary PVC materials, which can identify whether the packaged food uses GM materials. Using this kind of PVC film for packaging with special treatment, it can be determined whether the contents of the packaging, such as soybean oil, are made of genetically modified soybeans, even if they contain only 5-10% of genetically modified soybeans. It is mainly used for packaging non GM soybeans cultivated in southern Europe as a follow-up inspection and to ensure that no GM soybeans are mixed in the circulation process

British researchers have recently developed a new packaging material PHB bacterial plastic, which can be widely used in the food packaging industry. In this technology, a kind of bacteria is first cultivated with sugar through bacteria culture technology, and then a material similar to polypropylene is made through special processing technology. The product is non-toxic, biodegradable and has no pollution to the environment

IV. safety of plastic food flexible packaging

in order to increase its viscosity, transparency and elasticity during the manufacturing process, a certain amount of plasticizer has been added to the PVC fresh-keeping film, and the plasticizer contains a compound agent, which has great damage to the human endocrine system, will disturb the human hormone metabolism, and is very easy to penetrate into food, especially high-fat food, The cooked food in the supermarket is mostly high-fat food- If the food is wrapped for a long time, the oil in the food will easily dissolve the harmful substances in the fresh-keeping film, and when heated, it will accelerate the release of the compound agent in the plasticizer into the food. After eating, it can cause women to suffer from breast cancer, congenital defects of newborns, decrease in the number of male spermatozoa, and even mental diseases. The main component of plastic stabilizer is lead stearate, which is also toxic. This kind of lead salt is very easy to precipitate, once it enters the human body, it will cause cumulative lead poisoning. These toxic substances are harmful to human health if eaten together with food. In particular, when PVC plastic bags are used to contain food whose temperature exceeds 50 ~ 60 ℃, the lead in the bags will dissolve into the food

the American consumers' Union recently tested the cheese packaged with fresh-keeping film, and found that among 19 products, 7 kinds of cheese packaged in fresh-keeping film contain a high amount of plasticizer, and each million units of cheese contains 51 ~ 270 units of plasticizer. The average is 153 units, far beyond the safe range. The allowable range for European countries is 18 units per million units at most. At present, the use of plasticizers has been restricted in Europe and banned in Korea

relevant experts specially remind that it is better not to use colored plastic bags when packaging cooked food, snacks and other direct food with plastic bags. Because the pigment used for dyeing plastic bags has strong permeability and volatility, it is easy to exude when it meets oil and heat. If it is an organic dye, it will also contain aromatic hydrocarbons, which will have a certain impact on health. At present, some brands of plastic baby bottles sold on the market contain heavy metals harmful to health in their color patterns. Consumers must be careful in choosing and purchasing

consumers cannot distinguish between food and non food plastic bags, so a considerable number of unqualified plastic bags are used for food packaging, which seriously endangers people's health. At present, the unqualified plastic packaging bags used in the market are mainly recycled plastic products, or even made of recycled waste plastics. The vast majority of these plastic packaging bags come from some small individual plastic bag processing Shendong development preparation center. The waste materials are returned to the factory to save 1.1 million yuan. The production cost is low and the process is simple. Packaging food with such plastic bags, especially the food packaged in bulk and imported directly, does not meet the food hygiene standards, but also endangers the health of consumers. There are many bacteria and even viruses on these plastic packaging. The "close contact" between unqualified food packaging bags and food will not only pollute food, but also affect health. In particular, some food packaging bags will decompose some toxic substances when they are heated or packed into hot food, which will affect human health. As early as the 1990s, the Ministry of health expressly stipulated that "recycled plastics shall not be used for processing plastic tableware, containers and food packaging materials, and recycled plastics shall not be used for medical and health appliances."

the inspection of Baoding city found that most of the plastic packaging bags in the farmers' market are "three no products" from the counties and cities around Baoding, and some are even recycled products after crushing and granulating with plastic pesticide bottles, chemical agent bottles, medical plastic waste and other waste plastic materials. Manufacturers that use recycled plastics to make food packaging bags often add fluorescent substances to bleach the impurities in the products to make the products look whiter and better. This kind of packaging bag flows into the farmers' market in large quantities with the advantage of low price. Fluorescent substances have potential carcinogenic components. Consumers have long used plastic packaging bags containing fluorescent substances to contain food, especially high-temperature and high-fat cooked food such as fried chicken and fried dough sticks. Fluorescent substances will penetrate into food and enter human body, causing harm to human health. Therefore, it is strictly prohibited to add fluorescent substances to food packaging materials in China

plastic bags have been basically abandoned in foreign countries, and all bread, tomatoes and potatoes are packed in paper bags. Korean stores have - stopped offering free plastic bags to customers. Using paper bags made of natural ingredients can protect our bodies from toxins and protect the environment. In order to save wood, scientific researchers are stepping up the development of new technologies for making pulp by using non wood fibers instead of wood, improving the strength of paper bags, reducing the cost of paper bags, and striving to achieve chlorine free bleaching as soon as possible. At present, various technologies for manufacturing non wood pulp and plastic bags are in the ascendant. Non polluting paper bags made of straw, reed, wheat straw, kenaf, bamboo and bagasse are expected to replace plastic bags

although most plastic food packaging bags are safe, attention should also be paid to the methods in use. Do not use plastic bags for a long time to pack high-temperature food. In daily life, we often see that some people use plastic bags to pack steaming fried cakes, fried dough sticks, etc. if they are eaten in a short time, there is no great harm. However, if they cover the overheated food in the bag for a long time, some substances in the plastic will seep out and affect their health. When heating food in a microwave oven, it is best to use special plastic bags and containers for the microwave oven. Apply fresh-keeping film to the refrigerated and frozen food in the refrigerator instead of using ordinary plastic bags. The special processing materials of the fresh-keeping film have good air permeability and fresh-keeping performance. If the ordinary plastic bag is used a little longer, the food will deteriorate and rot, and the purpose of fresh-keeping will not be achieved. Information source: China Food media

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