Introduction of oxygen barrier test method for yogurt soft plastic packaging at low temperature
Abstract: Due to its high content of nutrients such as fatty acids, yogurt has a short shelf life. In order to extend the user's expiration date, it is often packaged with high-barrier packaging materials. In particular, the convenient Peli packaging has begun to use high barriers. Coextruded film of resin raw material. Whether the soft plastic packaging materials used in yogurt can guarantee the indicated shelf life requirements in a low temperature storage environment requires timely monitoring. In this paper, the common high-barrier black and white film yogurt package and milky white yoghurt package are placed in the low temperature environment of 5 °C and 0% RH for the detection and comparison of oxygen transmission rate, providing reliable technical and data reference for related industry customers.
Key words: yogurt, shelf life, Bailey bag, black and white film, milky white film, low temperature environment, oxygen barrier, oxygen barrier, oxygen transmission rate
Test significance:
Yogurt is a kind of dairy product which is added to the pasteurized milk to be fermented and then cooled and filled. Commonly, there are solidified, agitated and fruity types. Yogurt not only retains the nutrients that milk should have, but also causes some sugars and proteins in milk to be hydrolyzed into small molecules such as galactose, lactic acid and amino acids due to different processing techniques. The fatty acid content after fermentation is increased by 2 times compared with raw milk , making yogurt It is more easily digested and absorbed by the human body, and the utilization rate of various nutrients is improved. In order to ensure the nutritional value of yoghurt is preserved, the finished yoghurt packaging is usually stored at a low temperature. In order to make the yoghurt have a longer shelf life on the basis of low temperature preservation, more and more yoghurt packaging adopts high barrier material, Preventing the infiltration of large amounts of external O 2 and causing deterioration of the yogurt.
Yogurt is packed in various forms, mainly divided into Baili bag, plastic box and aseptic brick packaging. Among them, aseptic brick is a newly-emerging packaging form, which is a material structure of cardboard, metal foil and plastic composite film. The package is matched with special yogurt processing technology. It can achieve a shelf life of up to 6 months under normal temperature storage , but at a higher price. The yoghurt commonly eaten daily is mostly in the form of a bag. Usually, a co-extruded film of a white film and a black-and-white film is used, and a black-and-white film formed by adding a high-resistance resin material can meet the shelf life requirement of 14 to 21 days in a low temperature environment . In general, the lower the oxygen transmission rate of the packaging material, that is, the higher the oxygen barrier property, the longer the shelf life of the yogurt. We selected a brand of high-barrier black and white film yoghurt packaging and milky white yoghurt packaging, tested and measured the oxygen transmission rate in 5 °C , 0% RH environment, so as to realize the monitoring of oxygen barrier properties of yogurt soft plastic packaging at low temperature. It is convenient for dairy products manufacturers to monitor the quality of packaging materials in a timely manner.
Detection method:
The oxygen barrier test method for soft plastic packaging is divided into equal pressure method and differential pressure method. The tester of the differential pressure method is to place the sample between the high and low pressure chambers, vacuum the low pressure chamber, and charge the high pressure chamber. Oxygen gas with a certain pressure is tested for the oxygen permeability of the sample by testing the pressure change in the low pressure chamber. This method has a wide measuring range and is suitable for the detection of low oxygen permeability of high barrier materials and high oxygen permeability. Excessive non-blocking black and white film testing, and low temperature test conditions can be achieved.
At present, the domestic differential pressure test for oxygen transmission rate ( 23 °C standard test environment) test follows the national standard of GB 1038-2000 "Plastic film and sheet gas permeability test method differential pressure method". Taking into account the requirements of testing the 5 °C test environment, we will use the VAC-V3 differential pressure gas permeation instrument independently developed by Labthink to refer to the above standard method for oxygen transmission rate test of high-barrier black-and-white film and milky-white yoghurt bag. .
1 , test equipment
VAC-V3 differential pressure gas permeation instrument ( Labthink ), the industry's efficient six-cavity independent design, can test six identical or different samples at the same time , wide range, high precision temperature control from 5 °C to 95 °C The test gas permeability can be as low as 0.01 cm 3 /m 2 ·24h·0.1MPa , and the Zui height can reach 500,000 cm 3 /m 2 ·24h·0.1MPa . The test chamber vacuum can meet the high level requirement of < 20 Pa . . The instrument meets various national and international standards of ISO 15105-1 , ISO 2556 , GB/T 1038 , ASTM D1434 , JIS K7126-1 , YBB 00082003 , and can meet various plastic film, paper-plastic composite film under different temperature and humidity environments. Gas permeability test of sheet, metal foil, aluminum-plastic composite film and various high-barrier materials, sheets, etc., can test gas as O 2 , N 2 , CO 2 , He and other inorganic gases or inert gases.
2. Preparation of samples
Both the high-barrier black and white film and the milky white film were placed in a dry environment at 5 ° C for 48 hours. After removing the specimen were cut from each sample taken a sample having a diameter of 97 mm 3.
3. Test conditions
Location: Jinan Languang Packaging Safety Testing Center Test Temperature and Humidity: 5 ° C, 0% RH
Test gas: pure dry oxygen test method: differential pressure method
4. Test procedure
4.1 Test principle
The VAC-V3 adopts the differential pressure test principle, and the pre-treated sample is placed between the upper and lower test chambers and clamped. First, vacuum treatment is performed on the low pressure chamber (lower chamber), and then the whole system is vacuumed; when the specified degree of vacuum is reached, the lower chamber of the test is closed, and the test gas of a certain pressure is filled into the high pressure chamber (upper chamber), and the test gas is ensured A constant pressure difference (adjustable) is formed on both sides of the sample; thus, the gas will permeate from the high pressure side to the low pressure side under the action of the pressure difference gradient, and the internal pressure of the low pressure side is monitored and processed, thereby obtaining the test sample. Various barrier parameters.
4.2 sample clamping
Apply a layer of vacuum grease to the outer surface of the test chamber to prevent grease from being applied to the cavity intermediate disc; after placing the filter paper on the disc in the test chamber, the three states will be cut from the high-barrier black and white film . The adjusted samples are respectively clamped on the three test chambers of the VAC-V3 differential pressure gas permeation instrument . The sample should be kept flat and free of wrinkles. Gently press the sample to make good contact with the vacuum grease. The test chamber clamping structure clamps the sample.
4.3 Detection process
VAC-V3 is an automated test instrument, and the test process is convenient and easy to operate:
- The test temperature was adjusted to 5 °C using a temperature control device , and the relative humidity was adjusted to 0% RH .
- Open the device software, set the test parameters, and start the test. Test parameters include control parameters (test mode, upper chamber purge time, upper chamber pressure, test time, degassing time, etc.) and sample parameters (number, type, area, thickness, etc.).
- End of test, data processing.
- The oxygen transmission rate of the milk white film sample was tested as described above.
- Turn off the air supply and power supply.
Among the barrier film an oxygen transmission rate milky film sample at 5 ℃, 0% RH testing conditions were 1.4071 cm 3 / m 2 · 24h · 0.1MPa, 568.2024 cm 3 / m 2 · 24h · 0.1MPa, each 3 samples results relative deviation between the samples is less than 10%. Therefore, the difference in oxygen barrier between the yogurt bags of different materials in the low temperature environment is still large, which further affects the shelf life of the yogurt.
to sum up:
When using the VAC-V3 differential pressure gas permeation tester to test the oxygen transmission rate of yogurt bags of different materials, stable and accurate test results can be obtained, and the effect of oxygen barrier properties of yogurt packaging on the quality of yogurt can be strictly monitored, especially How to monitor the oxygen permeability of packaging materials in low temperature environments is even more critical. The yoghurt plastic packaging bag is only a typical representative of the plastic packaging film. Other oxygen plastic packaging materials used for storage in a low temperature environment can be tested according to the test method in the oxygen transmission rate test. Labthink has been committed to providing professional testing services and equipment to customers around the world. Over the years, it has provided tens of thousands of oxygen permeability testing services to customers around the world, including different types of container products from many companies at home and abroad. To provide customers with reliable data support. For more information about related testing instruments, you can visit Jinan Languang for specific information or call us directly. Labthink is looking forward to enhancing technical exchanges and cooperation with enterprises and institutions in the industry.
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