Factors influencing the shelf life of soft package

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Factors affecting the shelf life of soft packaged liquid milk and their detection

with the development of liquid milk in the domestic market, people have higher and higher requirements for the packaging quality of liquid milk. According to the analysis of insiders, people have higher and higher requirements for the quality of milk packaging because: first, consumers' demand for high-quality milk products; Second, consumers pursue convenience, and UHT is welcomed by consumers; Third, the needs of dairy enterprises' market expansion. High quality packaging is an inevitable choice for enterprises to achieve local market penetration and foreign market expansion

plastic bag packaging occupies 70% of the whole liquid milk market by virtue of its economic advantages, and its shelf life has become the focus of attention of consumers and milk producers

the important factors affecting the shelf life of liquid fresh milk are as follows:

1 The oxygen barrier performance of the packaging material, that is, the permeability. The quality of packaging materials' oxygen barrier performance is the direct reason that affects the shelf life of milk. When the package is exposed to the air, the oxygen molecules of the air will penetrate into the inner side of the package through the molecular gap of the packaging material and directly contact with the milk. When the amount of oxygen penetrated reaches a certain amount, the milk will deteriorate. With the development of the times, milk packaging has changed from the original single-layer polyethylene plastic film bag to multi-layer composite film packaging. These multilayer composite materials are added with aluminum foil or special coating in the production process, so the barrier performance of packaging materials to oxygen is greatly improved. Its barrier performance (specifically refers to air permeability here) is affected by production process, coating thickness, material composition and other factors. At present, the detailed specification of the national standard for the test method of material permeability is GB 1038, and the test principle is the current international general principle of differential pressure method. Test of air permeability: under constant temperature and unit pressure difference, the volume of gas passing through the unit area of the sample in unit time during stable transmission. It is expressed by the volume value under standard temperature and pressure, and the unit is: cm3/m2 · D · Pa; Test of gas transmission coefficient: under constant temperature and unit pressure difference, the volume of gas passing through the unit thickness and unit area of the sample in unit time during stable transmission. It is expressed by the volume value under standard temperature and pressure, and the unit is: cm3 · cm/cm2 · s · PA. The test steps are as follows: put the sample on the high-speed quantitative filter paper (diameter 85mm), seal it in the ventilation chamber, turn on the air source, start the test, and then the system pops up the test report. Precautions: the physical properties of the tested diaphragm can be damaged, such as flatness, no scratches, no perforation, no other attachments on the surface, no elastic or inelastic stretching; To ensure the temperature stability of the laboratory, "test temperature" is one of the parameters in the calculation formula, and its stability affects the reflection of data accuracy; Before the test, the membrane should be strictly dried to avoid the adhesion of water on the membrane to participate in the test; The front and back sides of coated film and composite film shall be tested respectively

2. The quality of the sealing process of the package. Liquid milk soft packaging is mostly three side packaging. If there is a problem in the sealing process, it will directly cause the invasion of oxygen, thereby accelerating the deterioration of milk. Packaging and sealing are affected by two factors: one is the packaging process of the manufacturer, and the other is the heat sealing performance of the material itself. The detailed specification for the test method of sealing performance is gb/t 15171. The principle is: under a certain vacuum, put the sample into the vacuum chamber and observe whether there is gas escape within the set time. The test method is: put the sample into the vacuum chamber, cover the vacuum chamber sealing cover, and close the inlet pipe valve. Open the vacuum pipe valve to vacuum the vacuum chamber, and adjust its vacuum degree to one of the following values in 30 ~ 60s: 20, 30, 50, 90 kPa, etc. Stop vacuumizing when a certain vacuum degree is reached, and keep the vacuum degree for one of the following times: 3, 5, 8, 10 minutes, etc. The adjusted vacuum value and vacuum holding time are determined according to the characteristics of the sample (such as the packaging materials used, sealing conditions, etc.) or the provisions of relevant product standards. However, it is not allowed to crack the sample or the seal due to the excessive internal and external pressure difference of the sample. Taking the c-95 sealing tester developed by Beijing landmark packaging equipment Co., Ltd. as an example, the experimental steps are as follows: put the sample 3. The cooling rate: + 30 ℃ ~ 0 ℃ is about 2.0 ℃/min into the vacuum chamber, inject an appropriate amount of water into the vacuum chamber, set the test vacuum and test holding time, start the test and observe whether there are bubbles escaping. If bubbles escape, the test shall be terminated, and the sealing performance of the product does not meet the test requirements. Otherwise, the sealing of the product is qualified. It is reported that Yili dairy group, a domestic dairy giant, once purchased the c-95 sealing tester produced by Beijing landmaker packaging equipment Co., Ltd. for the detection of liquid fresh milk packaging

there are three important indexes of material heat sealing performance: heat sealing temperature, heat sealing time and heat sealing pressure. The test method is: make samples under certain parameters, and cut samples with a width of 15 soil m and a developed length of 100 ± 1mm on the package according to the requirements of ZBY 28004 specification. Take the sample after state adjustment, take the heat sealing part as the center line, expand it to 180 °, clamp the two ends of the sample on the two clamps of the testing machine respectively, make the longitudinal axis of the sample coincide with the center line of the upper and lower clamps, and make it suitable for tightness, so as to prevent the sample from slipping and breaking in the clamp. The distance between clamps is 50mm, the test speed is 300 ± 20mm/min, and the maximum load when the sample is broken is read. If the sample is broken in the fixture, the sample will be discarded and another sample will be taken to make up. The temperature and relative humidity of the test environment are the same as that of the state adjustment environment. Taking the FS-300 heat sealing tester and ldx-200 intelligent electronic tensile machine produced by Beijing landmark packaging equipment Co., Ltd. as examples, the test steps are: set the test parameters such as predetermined temperature, time and pressure for the heat sealing tester, place the sample in the two heads after the parameters are stable, and press the test key. After the test, the sample shall be cut according to the requirements of ZBY 28004 after the sample is cooled to room temperature. Clamp the two ends of the sample on the upper and lower collets of ldx-200 intelligent electronic tensile machine respectively, and adjust the sample so that its longitudinal axis coincides with the center line of the upper and lower clamps through computer high-speed sampling, and the tightness is appropriate. Select the specified test speed, carry out the test, display the dynamic curve of the test process with LCD, and print the test report. Precautions: ensure the width of the sample, ensure that the longitudinal axis of the sample coincides with the center line, and ensure proper tightness when clamping the sample

the above are several important factors and test methods that affect the shelf life of liquid fresh milk. We hope that the majority of liquid milk manufacturers and packaging material suppliers can find out the quality control and solutions of packaging materials

the success of plastic packaging for liquid milk

with the rapid development of liquid milk and the development of new varieties in China, the packaging of products is becoming more and more important. At present, in the process of selecting liquid milk packaging materials, many dairy processing enterprises prematurely sentenced the "death penalty" of plastic packaging due to "white pollution". Regardless of their own conditions and market demand, they tried to cancel plastic flexible packaging and desperately put on some high-cost "paper" packaging, which is an undesirable development idea. At present, with the continuous improvement of materials and processing technology, Plastic packaging still plays an important role in the food industry

according to the survey of food packaging containers conducted by an American market research company, the annual growth rate of paper containers, metal containers, glass containers and plastic containers in the past five years (years) is 3.2%, 2.5%, 0.5% and 5.5%, respectively, By 2003, plastic packaging accounted for nearly 30% of the total market of food packaging containers. A the driving force for the high growth of the plastic packaging container market lies in the improvement of resin and its processing methods and the expansion of recycling. At the same time, it is also related to many factors, such as the reduction of material production costs and the continuous improvement of product performance and production efficiency

according to the prediction of China's authoritative departments, in the next two years, the sales of plastic flexible packaging in the food industry will exceed nearly 50% of the sales of the packaging industry. It is expected that the overall development speed of flexible packaging will be slightly faster than that of the overall national products

due to the excellent impermeability, UV linearity, freezing resistance and heat resistance of the improved plastic materials, the application market is broad, especially in the beverage and dairy industry. The application of plastics in aseptic packaging provides a development space for plastic packaging materials. At the same time, the improvement of plastic packaging materials will also promote the development of aseptic packaging in China

from the perspective of environmental protection: China's state environmental protection administration clearly stipulates in the definition of disposable fast food drinking utensils: materials that are easy to recycle, such as polypropylene (PP), high impact polystyrene (HIPS), two-way, people may find some color changing wall stretched polystyrene sheet products with new uses, and polypropylene filled with high filling amount of natural inorganic minerals are all listed as environmental protection materials. At present, most of the plastic materials used for liquid milk packaging in China are environmental friendly materials

judging from the development trend of international food packaging, five of the top ten development directions of food packaging in the United States are mainly plastic packaging, the first of which is: for most new packaging, raw materials based on petrochemical products are mainly used; Third, plastic cans and bottles will replace glass products and, in some cases, metal products. At the same time, they will reduce packaging costs by improving the performance of packaging materials, rather than unilaterally pursuing price reduction; Light packaging will continue to make progress; Promotion of filling packaging, etc. It can be seen from this that the development prospect of plastic packaging in the food industry is very broad

Hunan Wanrong Packaging Co., Ltd. proposed the advocacy of "cherish resources and strive to simplify dairy packaging". This action is undoubtedly in line with the current trend and will also promote the healthy development of China's liquid milk packaging industry. The company is positioned as a professional dairy packaging service provider. Its products mainly use plastic as the base material, and constantly research, develop and improve the barrier, shading, matte milk film, pearlescent milk film, milky milk film, cooking milk film, PP, hips yogurt cup, three-layer co extruded PS sheet, heat sealing cup cover film, providing a series of solutions for liquid milk packaging of dairy production enterprises

at present, in the development of plastic packaging for liquid milk, we should overcome various factors that hinder the development of plastic packaging materials, such as serious structural assimilation of plastic packaging materials, weak scientific and technological development ability, insufficient sources of funds, and take the road of high and new technology to develop more and better new products. In choosing the packaging of liquid milk, dairy processing enterprises not only rely on their own market, product positioning and the principles of "safety, convenience and low price", but also the development trend and relevant policies of international and domestic food packaging markets are important factors worth considering. To sum up, the application of plastic packaging materials in liquid milk packaging with its functionality, environmental protection, light weight and low cost will undoubtedly have a broad prospect. It is believed that after a period of great integration, the dairy industry will develop more healthily, and plastic packaging will also be continuously improved and developed in the dairy packaging industry

source: China Food Information

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