Uncover the ingredients of the hottest food packag

2022-08-12
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Uncover the secret of the composition of food packaging materials: the fresh-keeping film cannot be heated in the microwave oven

with the rapid development of food technology and packaging industry, many new packaging materials and packaging forms continue to appear, but cancer causing pots, toxic lunch boxes, odor plastic bags and other problematic products have also aroused the concern of the city people. What tests should these food contact products go through before use? Which products are more safe and reliable? What should we pay attention to when choosing? During the chemical and mineral testing center of Shandong entry exit inspection and Quarantine Bureau to carry out scientific and technological innovation and better life theme science and technology week, I went to the food contact material testing laboratory of Shandong entry exit inspection and Quarantine Bureau yesterday to find the answers to these questions. The nonstick pot had to be closed with acetic acid in the laboratory. I saw that the tester Wang Yue was using water from a special water pipe. Wang Yue told that these waters are not ordinary tap water, but experimental water that has been treated to remove interfering impurities such as metal elements, so as to ensure the accuracy of detection. In addition, the inspectors will also use the designated chemical solution to imitate alcohol, grease, acetic acid and other common food in life during the work process, and then pour these liquids into the food contact products according to the detection requirements. After the contact between the two reaches the specified time, they will detect the food simulation liquid or volatile gas through advanced instruments. Staff will add two non stick pots to acetic acid solution and boil at high temperature. Wang Yue told that the reason why the nonstick pot was nonstick was due to the coating at the bottom of the pot, which was coated on the substrate and sintered at high temperature. This material includes polytetrafluoroethylene, perfluoroethylene propylene and various fluorinated copolymers. These compounds have the advantages of high temperature resistance, low temperature, self lubrication, chemical stability and so on. However, if the bonding strength of the coating is not high and cannot be completely covered on the surface of the non stick pot, some metal layers will be exposed. Under high temperature conditions, acidic substances are easy to corrode the exposed metal layer, and some metal layers will expand once corroded, resulting in the falling off of the coating and the precipitation of heavy metals, which will have a certain impact on human health. Through laboratory testing, the concentration of chromium in 4% acetic acid soaking solution is determined to know the bonding degree of the coating and the content of chromium in the metal layer. When buying non stick pots, citizens should first check whether the non stick materials are sprayed evenly and evenly, and whether the thickness is the same. Do not fry at high temperature in the process of use, and avoid cooking with a shovel and making acidic food, otherwise it is easy to cause the coating to fall off. Wang Yue said. The most stringent inspection of popular products. All kinds of colorful food containers and packaging bags are fully exposed to the liquid, and then these fully exposed liquids are sent to professional instruments for detection according to the detection requirements of their standards. In the testing laboratory of food contact materials, three large-scale testing equipment, namely, full two-dimensional gas chromatography time of flight mass spectrometer (GC-TOF), one plasma emission spectrometer (ICP) and one ion trap mass spectrometer (ITD), are the main forces for detecting various precipitates. Looking at the relevant testing standards, it is found that many popular food contact products have many testing items, and the testing standards are also very strict. Ceramic like plastic products have smooth texture, and have unique advantages such as not easy to fade, high impact resistance, low thermal conductivity, high taste resistance, durability, and easy machine washing. But what many people can't think of is that melamine, which once caused serious problems to infant milk powder, is one of the main raw materials of this product. Melamine is just not allowed to be added to food. If melamine resin tableware strictly complies with national standards, it will not be harmful to human body. The head of the laboratory said. In addition, melamine resin, like other thermosetting resins, also has a health and safety problem, that is, formaldehyde, so there are relatively many testing items for products exposed to local manufacturers and suppliers. Consumers should also be particularly careful when choosing such products, and do not buy three noes products that have not been tested, so as not to cause serious health problems. The fresh-keeping film varies from material to material. Using frozen fresh-keeping film or fresh-keeping bag to keep food fresh in the refrigerator can slow down the water evaporation of food. It was found in the laboratory that although the fresh-keeping film or bag is similar in appearance, the materials used are not necessarily the same. Sunzhongsong, head of the food contact materials testing laboratory, told that there are three main types of fresh-keeping films sold on the market at present. The first type is polyethylene (PE or LDPE). Most of the fresh-keeping films sold in supermarkets are polyethylene fresh-keeping films. Polyethylene fresh-keeping films do not add any plasticizer in the production process, and are recognized as the safest of the three, which are mainly used for the packaging of ordinary fruits, vegetables and other foods, Including the semi-finished products purchased in the supermarket are all made of this material; The second type is polyvinylidene chloride (PVDC), which has very good safety, stability and degradability. However, due to the high production cost, the current market sales and application are not very extensive, mainly used for the packaging of some cooked foods and hams with high prices; The third kind is polyvinyl chloride (PVC), which can also be used in food packaging. However, because a large amount of plasticizer needs to be added in the production process of PVC film, the plasticizer is easy to release and penetrate into food in the heating environment, and it will interfere with the secretion in the body and induce diseases after eating. Therefore, consumers cannot heat food together with its original packaging in a hot pot or microwave oven. Sun Zhongsong said that polyethylene fresh-keeping film generally has poor viscosity and transparency, which is easy to open after kneading by hand, while PVC fresh-keeping film has good transparency and viscosity, which is difficult to unfold after kneading by hand and easy to stick to hands; After the polyethylene fresh-keeping film is ignited by fire, the flame is yellow, and it will not go out when leaving the fire source, with oil dripping. The qualified fresh-keeping bag is milky white, translucent or colorless, transparent, flexible, lubricated when touched by hand, and the surface seems to have wax. Toxic fresh-keeping bags are muddy in color and bulging in hand. Hold one end of the fresh-keeping bag by hand and shake it hard. Those who make a crisp sound are relatively safe, while those who make a dull sound are generally of poor quality. There are also hidden dangers in safety materials. The public generally believes that food contact products made of glass, ceramics and metals are relatively safe and can be safely used. The inspectors can't guarantee this view. Wang Yue told that in comparison, the inspection items of glass products are relatively reduced, and the safety is relatively high. Industrial molding aluminum machine processing, but this does not mean that this kind of goods will have no problems. In particular, crystal glass, which is now emerging, is loved by many consumers because of its high grade. In fact, the content of lead oxide in crystal products is as high as 20% to 30%. Using it to hold water will generally not cause lead poisoning, but if it is used as a cup to hold wine, the wine will dissolve the lead in crystal glass products. Frankly, the longer the time, the more the dissolution. Similarly, when crystal glass containers are used to hold foods, especially acidic foods such as cola, honey and fruit juice, lead ions are also easy to form soluble lead salts, which are ingested by the human body with beverages or foods, seriously endangering health. Therefore, crystal glass products are called beautiful killers by scientists. In addition, ordinary glass tableware is not completely reliable. Under the specific environment of long-term immersion, it will produce mildew. This is because the glass is eroded by water for a long time, and the reaction between sodium silicate in the glass and carbon dioxide in the air will produce white carbonate crystals, which are harmful to human health. The way to remove these carbonate crystals is to wash them with alkaline detergent. Sun Zhongsong suggested that consumers should not choose overglaze decoration when choosing ceramic tableware, especially the inner wall of ceramic tableware should not be painted. The ceramic tableware bought back should be soaked and boiled with vinegar water first, so that most of the toxic substances can be removed. Recently, a company in Shandong applied to import a batch of wine utensils produced in Germany. According to the sampling inspection of Qingdao inspection and Quarantine Bureau and the technical support of market-oriented expansion of products, the lead and nickel content of 11 stainless steel wine utensils exceeded the standard seriously, which were 270 times and 32 times of the standard limit respectively

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