Making metal food cans safer
- Problems and solutions to the production of metal food cans
Metal food cans are recognized as the safest and most environmentally friendly products in the world. The metal material has good airtightness and opacity, which can effectively prevent the contents from being oxidized by light and secondary intrusion of pollutants, and has the characteristics of safety, health, and health. In addition, metal packaging recycling recycling rate is the highest, in line with national energy conservation and environmental protection requirements.
However, with the development and use of new technologies and materials, as well as new understandings of certain characteristics of the original packaging materials, the food can manufacturing industry has encountered some new problems. How to make the name of food cans become the safest food packaging, eliminating or avoiding some obvious or invisible hazards, so that new technologies, new materials and traditional production processes can be more in line with each other, and can truly produce the company’s expectations. Economic benefits are issues that must be addressed and resolved in the industry.
Beware of the production of low-vacuum tanks At present, under the new requirements such as cost reduction and efficiency increase, and increasingly concerned environmental protection and low-carbon concepts, the gradual thinning of tinplate thickness in food cans is inevitable. However, if other production process parameters and production equipment do not change with it, a slight carelessness will lead to the production of low-vacuum defective cans, which makes many food tank manufacturers confused.
The can vacuum is formed after the exhaust seal and sterilization cooling. When the residual gas pressure in the tank is lower than the atmospheric pressure outside the tank, the pressure difference is the can vacuum.
Main factors affecting the abnormal vacuum degree change During the production process of food cans, when the exhaust process parameters are unchanged or the vacuum degree of the canning equipment is set to a certain value, and assuming that the quality of the can lid sealant is normal, the food cans can be formed in the cans after being sealed. Effective vacuum. In the subsequent high-temperature sterilization process, due to the sudden change in the pressure in the tank, when the container's sealing and holding capacity is insufficient to resist the pressure change in the tank, the vacuum in the tank will be reduced or even disappeared, which will affect the abnormal vacuum degree in the tank. The main reason (another detailed chapter).
The four major influencing factors on the pressure of the contents of the tank First, the difference in the amount of filling the contents, so that the reduction of the top gap volume is different, thereby affecting the tank pressure. Second, noncondensable gases in the contents of the tissue escape when heated and affect the pressure in the tank. Third, the mixed gas contained in the contents of the tissue escapes when heated and affects the pressure in the tank. Fourth, due to the different thermal expansion coefficients of the contents, different volume increments will be generated as the temperature increases. Under the condition that the empty can volume is certain, the reduction of the top gap volume varies greatly, resulting in different pressure changes in the tank.
Judgment of the degree of vacuum The product is judged with a small tamper before it is packaged, and the vacuum degree of the can is judged according to the clear and voiced sounds emitted when the stick strikes. This is a vacuum degree detection method commonly used by enterprises.
The test chamber is directly destructively tested with the vacuum gauge method, and a special vacuum gauge is required, which is often used for sampling inspection in the inspection department.
The advanced method is an online automatic detection method. The principle is to use an ultrasonic wave to perform analog-to-digital conversion and processing on the audio reflected from the cover, so as to accurately detect the degree of vacuum in the can. By performing on-line vacuum testing of each tank, all solid tanks with a vacuum range outside the set field value can be eliminated online.
The occurrence of low vacuum is a complex and comprehensive problem, but as long as the firm implementation of any measures to prevent the cans from being greatly degraded due to deformation, the quality problem of canned low vacuum can be controlled and avoided.
Metal food cans are recognized throughout the world as the "safest, environmentally friendly products."
The theory and practice of how to maintain the can vacuum during high temperature sterilization show that the content and the volume of the container will continue to expand during the high temperature sterilization of the food can, and the volume change of the former is often greater than the latter. Therefore, the expansion of the gas in the headspace gas and the gasification of the escaping gas and moisture of the contents form an increase in the pressure inside the tank, acting on the tank wall, especially for the bottom cover, and the sealing and holding capacity of the can container after deformation is insufficient. To withstand the pressure changes in the tank, it is clear that reducing the thickness of the tinplate will make the deformation more serious, resulting in an increase in the probability that the tightness of the crimp structure will decrease, and the vacuum in the tank will be reduced or even eliminated. In this case, maintaining the degree of vacuum in the tank depends on the quality of the seal of the can, the standardization of the sterilization operation, and other factors that cause deformation or even leakage of the can.
The standardization of sterilizing operation means that the employees who obtained the qualification certificate complete the sterilizing of the product in accordance with the operation procedures stipulated by the company in the sterilization GMP. This is a controllable process, and therefore the regular cannery production enterprises are few in this process. problem appear.
Other factors that cause cans to be deformed or even leaked Regular canners have certain production equipment and process rules. Under the conditions that the quality of the containers and bottom caps purchased meets the requirements, even if they produce low-vacuum cans, they are occasional and inconvenient. Causes the production of batch low vacuum tanks.
The quality of the can's seals From this point of view, the quality of the can's seal becomes a key factor that must be focused. First of all, when thinning materials are used, the possibility of less deformation of the container due to pressure changes is almost exhausted. Therefore, corresponding supporting measures are necessary, such as: adjusting the precision of the two rollers, or more reliably, changing. Dual reel-sealing roller curve; In addition, the width and depth of the head roller path curve must be reduced due to the smaller size of the thin-plate reel-sealing edge.
Secondly, in addition to following the traditional dual-entry seal quality control standards for all can-type empty cans and solid cans, the quality control elements of the seal structure should also be extended, ie, the strict control of double-hem curls should be added. Edge thickness (T=2tb+3tc+g) and its uniformity, the relationship between countersunkness and curl (C=W+0.15mm) and other parameters, once the curl thickness (T) and burying degree are found (C In order to deviate from the stipulated value, it is necessary to consciously adopt corrective measures as if the “triple rate†has not been met. Practice has proved that these measures can effectively avoid the occurrence of low vacuum tanks.
Concerned about the safety of food contact materials In accordance with U.S. law, food contact substances are indirect food additives. According to Article 402 of the Food, Drug and Cosmetic Act, no impurities may be incorporated into any food-grade substances. Food-grade substances must be reported to the US Food and Drug Administration (FDA). To obtain FDA approval, all ingredients must be evaluated for safety. The evaluation information includes characteristics, technical effects, self-defined use restrictions, dietary intake, and safety studies also include production processes including nanotechnology.
The problem of metal contamination of canned foods at the very beginning has now been basically solved. However, the security of organic matter inside paints has come along. There have been many reports at home and abroad in recent years. According to statistics, in 2012, the European Union's Rapid Alert System for Food and Feed (RASFF) informed the public of 551 food and feed problems imported from China, 219 of which were related to food contact materials, and accounted for 39.7% of the notified quantity. The highest proportion. Of the 219 problems related to food contact materials, 94 were metal products, accounting for the highest proportion (42.9%). The main reasons for the notification of contact with food contact products include excessive heavy metals, formaldehyde, high total precipitation, and aromatic primary amines, accounting for 80.30% of all notified metals and other materials. The European Food Safety Authority (EFSA) has reported that the absolute quantity of food contact materials has risen rapidly in recent years, and the proportion has remained high since 2009, and is on an upward trend.
In the past, in order to reduce or even completely eliminate the leaching amount of organic matter in the paint on the inner wall of cans, the main concern was to prevent the adverse effects of organic extracts on the flavor of the food in the tank, especially in the aspects of beer and beverage cans. Today, greater attention is focused on meeting the ever-increasing demands for food safety. The tolerance for many residual chemicals has been raised from ppm to ppb. Many coating companies are not able to keep up with the pace of safety parameters. The situation is particularly prominent in China.
Most of the canned foods used for metal containers are not fully connected, and they are blessed with carelessness. They say that vanadium is reported to vanish and vanadium is known as vanadium. The current situation is that some foreign large-scale can inner paint companies manufacture, sell or import in China. China's products have not yet experienced major food safety problems, and people feel that the level of paint in China's cans is in synch with the world. These coatings are made from mature processes and safe raw materials, and paint suppliers can also provide testing certificates for foreign authorities. However, the objective fact that we have to face is that the contents of canned foods vary widely, and no paint is suitable for all contents. On the other hand, with the growing awareness of food safety at home and abroad, the regulatory capabilities, business standards, and detection technologies of national food safety regulatory agencies are becoming more mature and powerful. The focus on food safety will surely increase. Deep and extensive, the security issues of many packaging materials that have touched on food safety issues will eventually surface, and the days when the printing and canning industry and the domestic coating manufacturing companies are facing a surge in pressure are approaching.
In the "12th Five-Year Plan" of National Food Safety Standards promulgated by the Ministry of Health in 2012, four work targets were proposed, one of which is to speed up the formulation and revision of national food safety standards and improve the universality and science of national food safety standards. Sex and practicality. The focus of the content includes the formulation and revision of food safety basic standards such as food packaging materials and additives. By the end of 2015, it will gradually improve food product standards for food containers, packaging, and processing equipment, and use of additives for food containers and packaging materials.
The national food safety standards for food contact materials and products in 2015 have been developed and are scheduled to be implemented on September 22, 2016. The contents include the general rules for the transfer of various cans. This information indicates that the country is Accelerate the basic legislation and legislation for the safety of food contact materials.
In today's "food is the basis of food and food is safety," metal food cans, like other packaging materials, are increasingly concerned about the relationship between packaging material migration and food safety. Problems such as melamine, plasticizers, and bisphenol A may be just the tip of the iceberg. As the classical and sustainable development of packaging materials, the migration of metal packaging materials is still a long-term task of food safety research.
As a canned food production industry, we should use a sense of historical mission and social responsibility to collaborate with the government to accelerate the development of hardware and software for basic research that is closely related to packaging materials and food safety, and actively participate in the food contact surface safety assessment. The top-level design of the safety and safety standard operating mechanism allows food safety guarantees for all metal containers including food cans to be well-founded and effective.
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