Abstract : Tinplate cans are commonly used in food packaging. To prevent the accumulation of toxic and hazardous substances in packaging materials during the storage process from affecting human health, we must ensure that their hygienic indicators meet the requirements. Evaporation residue is an important part of the health index. This article introduced the common detection methods for the amount of evaporated residue of tin can inner coating to provide reference for the industry customers.
Keywords: tinplate; coating; food safety; evaporation residue; evaporation residue constant weight meter
Test significance:
Tinplate has good barrier properties and processing properties and is commonly used in the packaging of moon cakes, chocolate, tea, coffee, biscuits, milk powder, fish, luncheon meat, beverages and other foods. The tinplate core material is iron and tin plated on the surface. Iron is very active and can easily react electrochemically with oxygen and food to corrode the packaging, resulting in destruction of the barrier and integrity of the packaging. Although the surface of the tinplate is tin-plated, due to the relatively high tin content, the tin plating amount is generally not high enough to resist the invasion of the contents by the packaging. Therefore, in addition to fruits and vegetables with poor corrosiveness and reduction requirements, tinplates used in most foods require inner coating.
Coatings are organic compounds and consist mainly of oils, resins, pigments, plasticizers, thinners, and other additives. Among them, oil and resin are the main film-forming substances, and pigments and plasticizers are auxiliary film-forming substances. Diluents are used for the dilution of resins or pigments to facilitate the coating of coatings. Solvents are volatile and should be completely volatilized after processing. However, in the actual production and use, metal tin cans protect the contents from environmental pollution and influence, and at the same time, the various types of substances contained in the coating on the inner surface of the metal can be transferred to the food at the same time, such as free phenol, Free formaldehyde and other monomers, when accumulated to a certain extent, will endanger food safety and pose a threat to human health. Therefore, it is necessary to detect the quality of the migration of tinplate coatings into foods.
Figure 1 Tin cans
Test Methods:
Evaporation residue is an indicator to measure the quality of chemical substances that may be precipitated during contact with water, acidic substances, alcohols, oils and fats during the use of the packaging. Simulated substances are usually distilled water, 4% acetic acid, 20% or 65% ethanol and Hexane. At present, domestic and foreign countries have requirements for the detection of packaging and migration of foods and standards. For example, China's GB 9685-2008 “Hygienic Standards for the Use of Additives for Food Containers and Packaging Materialsâ€, GB 4805-1994 “Hygienic Standards for Epoxy Phenolic Coatings for Food Canned Interior Walls †, GB/T 5009.69-2008 “Epoxy phenolic aldehydes for food cans Methods for Analysis of Hygienic Standards for Coatings, CFR21 PART 170-189 of the United States , Food Hygiene Law of Japan, etc.
test instrument:
The ERT-01 Evaporative Residue Constant Weight Meter of Jinan Languang Electromechanical Technology Co., Ltd. is a professional evaporative residue testing instrument, which is suitable for the detection of evaporation residue of tinplate tinplate inner can coatings. The device adopts automatic lifting mechanism design and intermittent weighing measurement method, and is automatically cleared before measurement to ensure the accuracy of weighing and effectively reduce the system error. The ERT-01 has an accuracy of 0.3 mg and a temperature control range of 100 to 130 °C . It can be weighed directly under high temperature conditions to avoid the influence of various factors in the cooling process. The instrument can test one to eight samples at a time. The blank sample and the coating sample can be tested at the same time, which not only solves the problem of time-consuming work for the blank test, but also makes the blank test and the test sample to be tested under the same conditions, increasing the test result. Accuracy.
Figure 2 ERT-01 Evaporation Residue Constant Mass Meter
Typical examples
Test sample: Empty canned meat for lunch (material tinplate). Wash the cans with soapy water 5 times, then rinse with tap water for half a minute until there is no soap foam, then rinse with distilled water 3 times, and dry for use.
Simulated liquid: Since the fat content of luncheon meat was high in this test sample, n-hexane was used as a simulated liquid in this test.
Instrument and equipment: Jinan Languang Electromechanical Technology Co., Ltd. ERT-01 Evaporation Residue Constant Weight Meter, Changzhou Nuoji Instrument Co., Ltd. Super Constant Temperature Oil Tank.
Preparation: Rinse the ERT-01 test cup with clean water, wipe and dry it for later use.
Test steps:
First empty cup test, put the test cup into the test chamber, keep the test cup level, gently place the test cup on the tray by hand, close the glass seal door and cover, weigh the ERT evaporation residue constant weight instrument comes with Test cup weight.
Then, 250 mL of n-hexane simulant was poured into five canned meat cans. According to GB/T 5009.69-2008 “Methods for Analysis of Sanitary Standards for Epoxy Phenolic Coatings on Food Cans's Inner Walls â€, five samples containing n-hexane were placed in a constant temperature oil bath and heated at 37 °C for 2 hours. . Each 200 mL soak solution was poured into five test cups of ERT-01 . At the same time, 200 mL of n-hexane stock solution was poured into the three test cups as a blank test.
Place 8 test cups in a constant temperature oil bath until most of the water evaporates, then place the test cup in the test chamber of the ERT-01 .
Set the test temperature to 105 °C and the weighing interval to 1 hour. The test mode adopts the difference mode, and the difference amount is set to 0.3 mg , that is, if the weight difference between two weighings is not more than 0.3 mg , the sample is considered to have a constant weight. The test cup containing the stock solution of n-hexane was set as the reference cup, and the test cup containing the sample was set as the test cup. When the test is started, the instrument automatically performs drying, weighing, and determination. When the constant weight is reached, the amount of evaporation residue is automatically calculated. After testing, the evaporation residue of this sample was 16.324 mg/L .
Judgment of results: According to the requirements of GB 4805-1994 "Sanitary Standard for Epoxy-Phenolic Coatings on Food Canned Inner Wall", the evaporation residue of n-hexane ( 37 °C , 2 h ) must not exceed 30 mg/L . Therefore, this sample complies with national regulations.
to sum up
The Labthink blue light ERT-01 evaporation residue constant weight meter can accurately measure the amount of evaporation residue of tinplate inner can coatings, which can effectively avoid random errors caused by manual operation and improve the accuracy and reproducibility of the test results. The simultaneous and independent testing of eight samples greatly improved the detection efficiency. The technical breakthrough of direct weighing at high temperatures further ensured the accuracy of the test results. Tinplate cans are only typical representatives of hollow containers. Other tests such as plastic bottles, jelly cups and other evaporation residue tests can follow this test method. To learn more about Labthink 's testing equipment and services, you can visit the website of Jinan Languang Company to check the equipment's specific information or call for advice. Labthink has been dedicated to providing professional testing services and equipment for customers around the world. It is looking forward to enhancing technology exchanges and cooperation with enterprises and institutions in the industry.
Copyright Notice: This article is copyrighted by Jinan Languang Electromechanical Technology Co., Ltd.
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