Food packaging is the final process in the modern food industry. It plays a vital role in protecting, promoting, and facilitating the storage, transportation, and sale of food. To some extent, it has direct or indirect effects on food quality that not only endanger consumer health but also undermine the healthy development of my country's entire food packaging industry and the food industry as a whole. Food packaging is closely linked to food safety. Food packaging must ensure the sanitation and safety of the packaged food. Currently, food containers and packaging materials permitted for use in my country can be divided into plastic products; natural and synthetic rubber products; ceramic and enamel containers; aluminum, stainless steel, and iron containers; glass containers; food wrapping paper; composite films, composite film bags; bamboo and wood; cotton and linen, etc.
Food Packaging Material Safety Analysis
plastic
Plastic is a polymeric material made from high-molecular-weight resin polymers as its basic component, with various additives added to enhance its performance. As a rising star among packaging materials, plastic packaging has become the fastest-growing packaging material in the world over the past 40 years due to its abundant raw materials, low cost, excellent performance, light weight, and attractive appearance. The migration and leaching of toxic and harmful substances remaining in plastic packaging materials lead to food contamination, especially in the following aspects.
The toxicity of the resin itself
Unpolymerized free monomers, cracking products (vinyl chloride, styrene, phenol, nitrile rubber, formaldehyde), degradation products, and toxic substances generated by aging in resins all have an impact on food safety. The US Food and Drug Administration asserts that it is not the polyvinyl chloride (PVC) itself but the vinyl chloride (VCM) remaining in the PVC that can cause cancer after oral ingestion, and therefore prohibits PVC products from being used as food packaging materials. Vinyl chloride monomer (VCM) leached from polyvinyl chloride has anesthetic effects and can cause vasoconstriction in human limbs, producing pain. It also has carcinogenic and teratogenic effects. It forms vinyl chloride oxide in the liver, which has strong alkylating effects and can combine with DNA to produce tumors [1]. Residues in polystyrene such as styrene, ethylbenzene, toluene, and isopropylbenzene pose a threat to food safety. Styrene can inhibit rat reproduction and reduce liver and kidney weight. Low molecular weight polyethylene dissolves in oils and fats to produce a waxy odor, affecting product quality. The extent to which these harmful substances affect food safety depends on their concentration in the material, the tightness of the packaging, the nature of the food in contact with the material, time, temperature, and solubility in the food. .
Surface contamination of plastic packaging
Because plastic is easily charged, it readily absorbs dust and microorganisms, thereby contaminating food.
Toxicity of additives such as stabilizers, plasticizers, and dyes added during the manufacturing process of plastic products.
A scientific study conducted by Professor Li Shuguang of the College of Basic Medicine at Tongji University and his research team shows that plasticizer contamination in my country's food is almost everywhere. The study found that almost all brands of plastic oil-storage drums contain two plasticizers, dibutyl phthalate (DBP) and dioctyl phthalate (DOP), whereas iron oil-storage drums contain almost none. .
Food contamination caused by large amounts of toxic additives, heavy metals, pigments, viruses, etc., in illegally used recycled plastic.
Recycling and reusing plastic materials is a common trend. Due to the complexity of recycling channels, hazardous substances often remain on recycled containers, making it difficult to ensure complete cleaning and processing. To cover up quality defects in recycled products, some people often add large amounts of paint, resulting in a lot of paint pigment residue and causing food contamination. For regulatory reasons, even when large quantities of medical plastic waste are recycled, it poses hidden dangers to food safety.
Ink pollution
The main components of ink are pigments, resins, additives, and solvents. Ink manufacturers often consider the safety effects of resins and additives but overlook the indirect hazards of pigments and solvents to food safety. Some inks add certain promoters, such as siloxanes, to improve adhesion. These substances will cause the compounds to break down at certain drying temperatures, producing substances such as methanol, which can harm the human nervous system. Ink printed on plastic food packaging bags has an even greater impact on food safety because some toxic substances, such as benzene, are not easily volatile. In recent years, the pass rate for plastic food packaging bags at various locations has generally been low, only 50% to 60%. The main reasons for failure are excessive benzene residues, etc. The primary cause of the excess benzene is the use of benzene-containing solvents to dilute the ink during the plastic packaging printing process.
Adhesive for composite film
Adhesives can be roughly divided into polyether and polyurethane adhesives. Polyether adhesives are being gradually phased out, while polyurethane adhesives are available in two types: aliphatic and aromatic. Adhesives can also be classified as water-based, solvent-based, and solvent-free according to their application type. Water-based adhesives will not have much impact on food safety, but due to functional limitations, they are not widely used in my country [4]. Solvent-based adhesives are still mainly used in my country [5]. In terms of food safety, most people only believe that if the residual solvent is not high, it will not affect food safety. In fact, this is only one side of the story. 99.1% of the solvent-based adhesives used in my country are aromatic adhesives [6]. They contain aromatic isocyanates. After packaging food with this type of bag and then steaming it at a high temperature, they can migrate into the food and hydrolyze to form aromatic amines, which are carcinogenic. My country currently has no national standard for adhesives used in food packaging, and there is no indicator of heavy metal content in the corporate standards of various manufacturers and suppliers. However, there are strict restrictions on aromatic amines in foreign food packaging. For example, the EU stipulates that their total migration is less than 10 ppb. .
paper
Paper packaging materials hold a very important position in food packaging due to their unique advantages. In some developed countries, paper packaging materials account for 40% to 50% of the total packaging materials, and in my country, they account for about 40%. National standards set regulations for the hygiene indicators, physical and chemical indicators, and microbial indicators of food packaging base paper. Pure paper is clean, non-toxic and harmless, and can be broken down by microorganisms under natural conditions without polluting the environment. Sources of hazardous substances in paper and their effects on food safety mainly exist in the following aspects.
Pollution caused by the raw materials used in paper manufacturing itself.
Raw materials for producing food packaging paper include wood pulp, straw pulp, etc., which contain pesticide residues. Some use specific parts of recycled waste paper to make the paper, because even though the recycled waste paper has been de-inked, it only removes ink pigments, while hazardous substances such as lead, cadmium, and polychlorinated biphenyls can still remain in the pulp; others use moldy raw materials to produce it, so that the finished product contains a large amount of mold.
Additives in the paper manufacturing process
Paper manufacturing requires the addition of chemicals to the pulp, such as sizing agents, sizing agents, fillers, bleaching agents, dyes, etc. Most of the leachable soluble substances in paper come from additives, dyes, and inorganic pigments in the pulp. Various metals are often used, and these metals can leach even at levels of mg/kg and cause disease [2]. For example, in the paper processing, especially when using chemical pulping, paper and paperboard usually contain certain chemical residues, such as alkali and salts left over from the sulfate pulping process. Food Safety and Sanitation Law stipulates that fluorescent dyes or fluorescent whiteners are prohibited for use in food packaging materials, as they are carcinogenic [7]. Additionally, antifungal agents or formaldehyde used in resin processing can also leach from paper products.
Pollution caused by ink
My country does not have special inks for food packaging. Most of the inks printed on paper packaging are organic solvent-based gravure inks containing toluene and xylene. To dilute the ink, benzene-containing solvents are often used, resulting in excessive benzene solvents. Benzene solvents are not permitted for use in the GB9685 standard, but they are still used in large quantities; second, the pigments and dyes used in the ink contain heavy metals (lead, cadmium, mercury, chromium, etc.), aniline or condensed ring compounds, which cause heavy metal contamination, and aniline or condensed ring dyes are known carcinogens. During printing, they are mixed together, causing the non-printed surface to come into contact with the ink, forming secondary contamination. Therefore, the hazardous substances in paper packaging printing inks have a serious impact on food safety. To ensure the safety of food packaging, the use of benzene-free printing will be a development trend.
Pollution during storage and transportation
The surface of paper packaging becomes contaminated with dust, dirt, and microorganisms during storage and transportation, which compromises food safety.
metal
Metal packaging materials are one of the traditional packaging materials and have been used for food packaging for nearly 200 years. Metal packaging materials are processed into various types of containers using metal sheets or foil as the raw materials for food packaging. Due to its advantages of high barrier properties, high and low temperature resistance, and easy waste recycling, metal packaging materials are increasingly used in food packaging. The biggest disadvantage of metal as a food packaging material is its poor chemical stability and resistance to acids and alkalis. In particular, it is easily corroded when used to package highly acidic foods, and metal ions are easily precipitated, thereby affecting the food's taste. The main safety issue with iron containers is that zinc will migrate into the food after the galvanized coating comes into contact with it, causing food poisoning. Aluminum materials contain elements such as lead and zinc, and long-term ingestion will cause chronic cumulative poisoning; aluminum has poor corrosion resistance and is prone to chemical reactions that cause it to precipitate or produce harmful substances, and it is difficult to control the impurities and hazardous metals in recycled aluminum. Stainless steel products contain a large amount of nickel, which causes the container's surface to turn black when exposed to high temperatures. At the same time, its rapid heat transfer makes it easy for unstable substances in food to gelatinize and denature, and may also produce carcinogens. Stainless steel should not come into contact with ethanol, as it can leach nickel and cause chronic poisoning in the human body. Therefore, it is generally necessary to use paint on the inner and outer walls of metal containers. The inner wall coating is an organic coating applied to the inner walls of metal cans, which can prevent the contents from direct contact with the metal, avoid electrochemical corrosion, and extend the shelf life of food. However, chemical contaminants in the coating will also migrate into the contents during canning and storage, causing contamination. These substances include BPA (bisphenol-A), LENCANA (bisphenol-A diglycidyl ether), NOGE (phenolic varnish glycerol ether), and their derivatives. Bisphenol-A epoxy derivatives are environmental hormones that enter the body through canned food, causing endocrine disruption and genetic mutations.
glass
Glass is an ancient packaging material. More than 3,000 years ago, the Egyptians first made glass containers, and since then, glass has been used to package food and other goods. Glass is a molten product of silicates, metal oxides, etc. It is a inert material that is non-toxic and harmless. The greatest characteristics of glass as a packaging material are: high barrier properties, brightness and transparency, good chemical stability, and ease of forming. Its use accounts for approximately 10% of the total packaging materials.
Dissociation of toxic materials during melting
In general, the internal ions in glass are tightly bound. After high-temperature melting, they mostly form insoluble salt compounds with excellent chemical inertness, which do not react with packaged foods and provide good packaging safety. However, glass products that do not melt properly may have issues with toxic substances leaching from the raw glass materials. Therefore, glass products should be soaked in water or heated with molten acid. Foods and medicines with strict packaging requirements can convert soda-lime glass into borosilicate glass. At the same time, attention should be paid to the quality of glass melting and molding processing to ensure the safety of packaged food.
Excessive heavy metal content
Luxury glassware such as tall wine glasses often contain lead compounds, and the amount added can be as high as 301 parts per million in the glass. This is a safety concern that is particularly prominent in glassware.
Safety hazards of coloring agents in stained glass
To prevent harmful light from damaging the contents, various dyes are used to color the glass. The main safety concern with the added metal salts is the migration of dissolved substances from the glass. For example, the added lead compounds can migrate into wine or other beverages, and silicon dioxide can also be leached. .
Ceramic
Compared to containers made of metal, plastic, and other packaging materials, ceramic containers can better preserve the flavor of food. For example, fermented bean curd packed in ceramic containers is of higher quality than fermented bean curd packed in plastic containers because ceramic containers are good at keeping air out and the arrangement of their ceramic molecules isn't too tight, so they don't completely block air, which is conducive to the later fermentation of the bean curd.
The issue of hygiene and safety of ceramic packaging materials used in food packaging primarily refers to the leaching of heavy metal elements such as lead or cadmium from the glaze layer on the surface of glazed ceramics. It is generally believed that ceramic packaging containers are non-toxic, hygienic, and safe, and will not have any adverse reactions with the food they contain. However, long-term studies have shown that glazes are primarily composed of various metal oxides and their salts such as lead, zinc, cadmium, antimony, barium, copper, chromium, and cobalt, most of which are hazardous materials. Ceramics are fired at 1000-1500°C. If the firing temperature is low, the colored glaze fails to form an insoluble silicate. When using ceramic containers, toxic and hazardous substances are easily leached and contaminate food. For example, when they contain acidic foods (such as vinegar, juice) and wine, these substances are easily leached and migrate into the food, causing safety issues. Both domestic and foreign regulations have set limit values for the total lead and cadmium leached from ceramic packaging containers.
Above is a brief introduction to the safety of food packaging materials and primary materials. With the development of the national economy, policy adjustments, and changes in consumer concepts, we have begun to establish a scientific, targeted, and practical food packaging safety control system based on the experience of developed countries; gradually establishing and improving new regulations on food packaging materials, and formulating a food packaging quality standard system in line with international standards. As consumers, it is crucial to increase their awareness of self-protection. From a survey on consumer beliefs about the hygiene and safety of food packaging materials, it can be seen that the public believes that glass, ceramics, and metal are safer [9], but these materials also have safety hazards. Consumers have a lack of safety knowledge, such as being unable to recognize information on labels, which affects their acceptance of safety information. .
Trends in the development of food packaging materials
Supporting low-carbon, eco-friendly packaging
In the food production industry chain, supporting environmental protection and low carbon has become a general trend, and environmental pollution and resource waste caused by discarded packaging are drawing increasing attention. It has become a consensus to implement packaging reduction, resource utilization, harmlessness, low carbon, safety, and reuse packaging. The food packaging experiences of Europe and the United States should be studied and used as a reference. For example, Sweden and other countries have implemented the reuse of polyester PET beverage bottles and PC baby bottles more than 20 times, the Netherlands' Wellman Company and America's Johnson Company have 100% recycled PET containers, and some paper packaging can be recycled after use. Any consumer material that is not handled properly will cause pollution.
Establish a system of reasonable use to reduce environmental pollution.
In the field of packaging materials, polymers are developing faster than glass, metal, and paper. The main reason is that polymers offer good functionality.
After my country joined the WTO, due to tariff reductions, the import tax on plastic resin will drop by 60%, and my country's plastic packaging industry will have more room for development. According to the report, the annual growth rate of paper containers in the United States over the past five years was 3.2%, the annual growth rate of metal containers was 2.5%, the annual growth rate of glass containers was 0.5%, and the annual growth rate of plastic containers was 5.5%. Food packaging materials need to be evaluated throughout the process. From an economic perspective, the transportation and storage costs of biodegradable materials are relatively high. For consumers, the cost of paper packaging is higher than that of plastic packaging (about twice as much). It can be seen that plastic will continue to be the most commonly used and convenient packaging material for food. Therefore, it is necessary to establish a reasonable consumer usage system to reduce and gradually eliminate its pollution to the environment.
Strengthening research, development, and safety assessment of functional packaging materials.
In the future, food packaging materials will pay more attention to functions under the premise of safety. Paper food packaging materials enhance moisture barrier, freshness preservation, sterilization, antiseptic (antioxidant) properties, water resistance, acid resistance, oil resistance, and deodorization; biodegradable packaging materials strengthen systematic research and evaluation of their stability, degradability, and economics, such as safety assessment under temperature, humidity, pH, oxygen content, and food containing oil under different microwave conditions. Therefore, the scientific research department should enhance systematic research on food packaging materials and develop products that meet food hygiene requirements and are non-toxic and harmless to the human body and the environment.
Accelerating the review and formulation of standards and establishing a quality standards system aligned with international standards.
Currently, some of my country's food packaging hygiene standards and regular sampling items were formulated in the early 1990s. The existing old standards cannot meet the testing of new materials and are no longer suitable for product safety requirements. In view of the current situation of outdated standards, management departments should refer to international advanced standards to accelerate the revision, improvement, and updating of existing standards. My country has a certain gap with developed countries in safety evaluation and testing technology, which affects the evaluation ability of new substances and new materials. Some monomers and additives cannot be detected, and even if they are detected, their sensitivity is very limited. Therefore, we should strengthen the construction of the detection and evaluation capabilities of technical support institutions, conduct research on trace detection technology and ultra-trace detection technology for some monomers and additives, establish methods for detecting multiple types of chemical substances, improve various detection standards, and develop fast and effective detection methods and detection equipment as soon as possible. At the same time, we should continue to strengthen cooperation with international organizations, such as the Codex Alimentarius Commission (CAC), the World Health Organization (WHO), the Food and Agriculture Organization of the United Nations (FAO), etc., and formulate and improve the safety evaluation procedures, evaluation mechanisms, and management methods for food packaging materials as soon as possible.
Enhancing the food packaging material safety assurance system
Accelerate the promotion of market access systems for the quality and safety of packaging materials, and actively carry out mandatory certification work. For enterprises that have obtained production licenses, post-certification supervision should be strengthened, and a robust long-term safety mechanism should be established. The relatively successful experiences in Europe and the United States should be studied, and we should establish a sound food packaging access system and regulatory measures, such as a food and packaging quality and safety certification system, a food and packaging recall system, and a traceable food and packaging safety database. The GMP and HACCP systems are now recognized worldwide as the most effective and economical food safety systems [14]. My country should implement mandatory GMP and HACCP certification systems in the food packaging materials industry as soon as possible to build a strong barrier for the safety of our food packaging.
Strengthening corporate self-discipline and social responsibility
For the average consumer, it is extremely difficult to determine whether food packaging poses safety hazards. The relevant departments should introduce appropriate measures to regulate corporate production and ensure the safety of food packaging materials at their sources. Legal awareness, self-discipline, and the social responsibility of production enterprises are directly related to food safety issues. As an important part of food processing, the food packaging industry should gradually implement annual inspections, regular inspections and surveillance, and surprise inspections, and strengthen oversight of small and family workshops and penalties for illegal enterprises. In addition, the unclear functions of supervisory departments, overlapping supervision, and regulatory weaknesses must be reformed to improve management efficiency and encourage enterprises to produce according to standards and operate within the law. Food packaging materials not only involve environmental protection issues, but more importantly, they involve public health and safety issues. The safety of food packaging materials is on par with food safety. Strengthening the quality and safety of food packaging materials not only ensures food safety, but also ensures consumer health and social stability and harmony.
Conclusion
Food packaging materials are important not only for preserving food quality but also for ensuring public health and safety. Although materials such as plastic, paper, metal, and glass are widely used, each comes with its own set of risks, including pollution, transfer of toxic substances, and environmental concerns. To address these challenges, it is essential to continuously raise safety standards, conduct comprehensive research, and establish stringent testing protocols. Furthermore, promoting eco-friendly and functional packaging materials, along with strengthening regulatory frameworks and corporate self-discipline, will be key to advancing food packaging safety. By taking these steps, we can protect consumer health and the future of the food packaging industry.
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