Plastics are favored by the packaging industry because of their low price and simple manufacturing process. With the continuous development of today's Internet economy, the food delivery industry is rapidly emerging, and the use of plastic packaging for food has become more widespread and frequent. In order to meet actual needs, plastic packaging for food has stronger safety and heat resistance than other plastic products, so some necessary additives are often added in the production process of plastics for food. If the additives are incorrectly added or used excessively, it may directly affect the safety of food. Therefore, the analysis of the safety of food plastic packaging products has high practical significance and far-reaching impact.
1 Analysis of the material and characteristics of plastic packaging for food
Compared with other packaging materials such as paper, glass, metal, plastic materials have better plasticity, elasticity and chemical stability, and can be made into films, bags, bottles, cans, barrels and other packaging forms according to different needs. Plastic materials have a certain degree of resistance when they contain common organic solvents, salts, acids, alkalis and other materials. At the same time, plastic packaging is generally lighter and more convenient to use and carry.
1.1 Polyethylene (PE)
Polyethylene resin is the most commonly used raw material in plastic packaging products for food at this stage. It has the characteristics of good crystallinity, high transparency, good barrier properties, mechanical properties, and chemical stability. Among them, linear low-density polyethylene can be made into film materials and is widely used in the fields of plastic bags, cling film and inner plastic packaging film.
1.2 Polypropylene (PP)
Polypropylene is also one of the commonly used resin raw materials, because it has higher transparency and gloss than polyethylene, and has better mechanical properties, heat resistance and chemical resistance. It can be used at 120°C. It is used continuously, so it is often used in products such as plastic fresh-keeping boxes, take-out packaging boxes, and plastic tableware.
1.3 Polyethylene terephthalate (PET)
Polyethylene terephthalate is abbreviated as polyester, which has good transparency and gloss. At the same time, it also has high barrier properties, which can effectively block grease and air. The tensile strength can reach 5-10 times that of polyethylene, and it can be used normally in the temperature range of -70～120°C, so it is often used in beverage packaging, such as PET non-spark beverage bottles.
1.4 Polyamide (nylon)
Polyamide resin has strong water absorption, which is not only difficult to block water, but also causes overall performance degradation after water absorption, so it is not suitable for packaging foods and beverages with high water content. But it has outstanding mechanical properties, not only has high abrasion resistance, but also is cold-resistant, tear-resistant, and convenient for printing, so it is often used in the packaging of frozen food and cereal food.
1.5 Polycarbonate (PC)
Polycarbonate has obvious advantages in heat resistance, transparency, and impact resistance. However, since it must be produced from bisphenol A, the packaged products produced may contain endocrine inhibitors. Therefore, polycarbonate has been banned from being used in the production of baby products such as baby bottles.
2 Safety risk analysis of plastic packaging for food
2.1 Source analysis of hazardous substances in food plastic packaging
Hazardous substances contained in plastic materials: Plastic materials are mainly formed by the polymerization of monomers, but in the process of synthesis, some monomers, such as ethylene, acrylonitrile, styrene, and vinyl chloride, will inevitably remain. Have a certain impact on the human body. For example, polycarbonate contains many endocrine inhibitors. If it is used in food packaging, after people eat food contaminated with polycarbonate, it is easy to cause hormone secretion disorders. Even the volatilization of these monomers will cause the human body. Larger negative impact.
Additives: Plasticizers are commonly used additives, which can make plastics easy to shape and make them easier to process. Phthalates are currently the most commonly used plasticizers. Excessive intake will not only lead to disorders of secretion in the human body, but also affect organs to varying degrees. Antioxidants can effectively alleviate the aging problem of plastics and extend the use time limit. At present, dibutyl hydroxytoluene and tert-butyl hydroquinone are two common antioxidants in the production of plastic packaging products.
2.2 Detection methods of hazardous substances in plastic packaging for food
At this stage, there are many methods for detecting the content of contaminants in food plastic packaging products, mainly including gas chromatography, gas-mass spectrometry, high performance liquid chromatography, and high performance liquid chromatography-mass spectrometry. Among them, gas chromatography is the most commonly used pollutant detection method, which mainly uses the boiling point difference between oligomers and highly volatile monomers to complete trace detection. Gas chromatography-mass spectrometry is mainly used in the detection of plasticizer content in plastic packaging products for food. High performance liquid chromatography is mainly used for the substance analysis and detection of food plastic packaging products, including melamine and polyterephthalic acid. Compared with other detection methods, HPLC has high sensitivity, good accuracy, more thorough purification, shorter analysis time, and its precision, recovery rate, detection limit, etc. can meet the requirements for general substances. Testing requirements.
In summary, analyzing the safety of plastic packaging products for food has high application value. In plastic packaging products for food, ethylene, acrylonitrile, styrene, vinyl chloride, plasticizers, antioxidants and other substances are relatively common harmful substances, which are harmful to health. Through gas chromatography, gas chromatography-mass spectrometry, high performance liquid chromatography and other methods, the content and content of harmful substances in plastic food packaging products can be accurately detected, which provides a data reference for ensuring basic food safety.