Abstract: In order to ensure its long shelf life, nitrogen or air-conditioning packaging is still needed on the basis of selecting high-barrier materials for milk powder packaging, in order to protect the milk powder from oxidation in an inert or acidic environment. Therefore, effective top air body composition testing equipment is needed to timely monitor the gas components in the milk powder packaging to prevent the quality problem of the decrease of the internal N 2 or CO 2 ratio caused by poor packaging sealing or poor material barrier properties . . This paper introduces the detection process of the internal top air component of the milk powder modified atmosphere packaging, in order to provide a more detailed technical reference for related industry users. Key words: milk powder, nitrogen-filled packaging, modified atmosphere packaging, hollow packaging container, headspace composition, headspace analyzer, nitrogen to oxygen ratio, nitrogen ratio, O 2 to CO 2 ratio, N 2 ratio Test significance: The high content of nutrients such as protein and fat in milk powder is the main material source for weak constitution and daily intake of infants and young children. Therefore, how to ensure the nutrients inside the milk powder is not destroyed and how to extend the shelf life of milk powder is a lot of milk. The important problems faced by powder production enterprises. At present, the milk powder packaging is divided into two types: bagged and canned. The bagged milk powder is mostly made of aluminum-plastic composite film or aluminized composite film material, while the canned milk powder is basically made of aluminum alloy can or tinplate can. Meets high barrier properties and good sealing. In order to further ensure that the milk powder is not easily oxidized, more brands of milk powder enterprises are filled with nitrogen ( N 2 ) or a certain proportion of carbon dioxide ( CO 2 ), that is, nitrogen- filled packaging or modified atmosphere packaging, relying on inertness of N 2 . The gas eliminates the presence of O 2 in the package , and a certain proportion of CO 2 is charged to ensure the internal acidic environment and thereby inhibit the growth of aerobic bacteria in the milk powder. However, if the packaging material used for the milk powder has a poor barrier to N 2 or CO 2 or the milk powder package is not tightly sealed, it is easy to change the content of N 2 or CO 2 inside the package , thereby making the nitrogen-filled package or gas. Adjusting the package does not protect the milk powder. In response to the above problems, we can use effective testing equipment to monitor the composition of the top air content inside the package, such as the headspace air analyzer, so as to grasp the specific proportion of O 2 , CO 2 and N 2 in the package , and timely control the finished milk powder. Packaging quality. Detection method: The headspace analysis often uses a sensor method to inject a volume of gas sample drawn from the inside of the sealed package into a specific gas analysis sensor, and record the specific gas concentration value output by the sensor after a certain test time. The detection of each gas content requires the use of different gas analysis sensors. At present, there is no targeted standard method for the detection of the top air body inside the domestic sealed package. However, there are many types of detection instruments for the top air body at home and abroad, and the technical level and accuracy of the instrument are also high, so the package is inside. The monitoring of the composition of the head air should have a certain universality. We will use the HGA-03 top air analyzer independently developed by Labthink to test the proportion of O 2 and CO 2 gas in the powder modified atmosphere packaging (aluminum-plastic composite film) . 1 , test equipment HGA-03 top air analyzer, with O 2 and CO 2 gas analysis sensors, O 2 and CO 2 measurement range is 0 ~ 100% , O 2 and CO 2 measurement accuracy is ± 0.5% , ±2% , the required sample gas volume is low, the automatic mode sample volume is only 3.6 mL , and the manual mode is also less than 5 mL . The automatic lifting sample stage is equipped to realize the complete automation of the whole sample puncture and analysis process, and the anti-blocking structure design is adopted to effectively prevent the powder sample from clogging the instrument. The instrument can be adjusted according to the height of the sample and the test space. The system is equipped with Chinese and English bilingual operating environment to meet the needs of users of different languages. The instrument can accurately and conveniently measure the content of O 2 and CO 2 in a hollow packaging container such as a sealed package, a bottle, a can, and the like , and such as coffee, milk tea, milk powder, bread, and the like. It is suitable for quickly and accurately evaluating the content and proportion of gas components in production lines, warehouses, laboratories, etc., thereby guiding production and ensuring shelf life. Figure 2 HGA-03 top air analyzer 2. Preparation of samples In a standard environment of 23 ° C and 50% RH , the sample with no obvious defects, leakage and good sealing was placed in a desiccator for more than 48 hours. The number of samples was 5 , and the average value of the test was taken as the test result. 3. Test conditions Location: Jinan Languang Packaging Safety Testing Center Test Temperature and Humidity: 23 ° C, 50% RH 4. Test procedure 4.1 Test principle The HGA-03 top air analyzer inserts the sampler into the package to be tested and collects a sufficient volume of sample gas from the headspace inside the package. The sample gas is injected into the gas analysis sensor, and the test data is recorded after a certain test time or after the gas concentration value output from the gas analysis sensor is stabilized. The detection of each gas content requires the use of different gas analysis sensors. When detecting the O 2 content in the sample gas, the sample gas needs to be injected into the O 2 analysis sensor, and the sample gas is required when detecting the CO 2 content in the sample gas. Inject the CO 2 analysis sensor. 4.2 sample processing Stick the gasket to the part to be tested of the sample, and pay attention to stick it firmly to prevent air leakage. Figure 3 sealing pad paste schematic 4.3 Detection process HGA-03 automatically collects the top air body. The instrument adopts a microcomputer control system, which can analyze, process and provide report output function for the test data, so the whole test process is convenient and quick: The top five samples in the body of air O 2 and CO 2 content ratio of the arithmetic mean, respectively, 2.1%, 25.7%, and the value of each of the arithmetic mean deviation of the test sample is not more than ± 10%. For modified atmosphere packaging, the internal gas except for O 2 and CO 2 is mostly N 2 (because N 2 is an inert gas, no corresponding gas sensor has been developed at home and abroad), and the proportion of other gases is negligible. Therefore, the N 2 ratio content can be obtained by subtracting the ratio of O 2 and CO 2 from 100% . to sum up: When the HGA-03 top air analyzer is used to test the top air component in the modified atmosphere powder, the ratio of O 2 and CO 2 with high accuracy and repeatability can be obtained , which can truly reflect the gas environment in the milk powder. Effectively monitor the harmful O 2 components to ensure that the ratio of internal CO 2 to N 2 can meet the needs of the milk powder shelf life. The test equipment used in this test is also applicable to the determination of the content of O 2 and CO 2 and the mixing ratio thereof in other packaging containers containing certain gases . Labthink has been committed to providing professional inspection services and equipment to customers around the world. Over the years, it has provided thousands of packages of internal gas composition monitoring solutions to customers around the world, providing reliable data support. Understand information concerning the relevant testing equipment more packaging barrier properties, mechanical properties, etc., you can board the Lu Languang view specific information or call us. Labthink is looking forward to enhancing technical exchanges and cooperation with enterprises and institutions in the industry. Copyright statement: Article Copyright Jinan Languang Electromechanical Technology Co., Ltd., reprinted without permission! 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Test method: gas sensor method 