Application of barrier test in dairy packaging 0

Application of barrier testing in dairy packaging

Abstract: Based on the main quality influencing factors in the preservation of dairy products and dairy products, this paper introduces the application of barrier testing in dairy packaging in detail, and discusses the relationship between the barrier of packaging materials and the shelf life of products

key words: dairy products, fresh milk, fermented milk, milk powder, barrier, oxygen permeability, moisture permeability

in recent years, with the sustained and stable development of China's economy and the continuous improvement of people's living standards, the dairy industry has entered a golden period of development and become one of the fastest growing and best growing industries in China's food industry. Nowadays, milk and dairy products have become one of the symbols of healthy life. All kinds of dairy products and dairy products have extensive sales networks. However, with the different selling environment, it is difficult to ensure that dairy products are stored in a continuous and stable environment (even if it is difficult to provide low-temperature refrigeration environment for fresh milk preservation from beginning to end). Therefore, dairy packaging has a great impact on the quality of dairy products. The quality of packaging can directly affect the shelf life of dairy products, and then related to the food safety of consumers

1. The main reasons affecting the quality of dairy products and the corresponding packaging forms

dairy packaging, as an integral part of dairy products, has a profound impact on the development of dairy industry. Because milk is easy to deteriorate, both long-acting milk (UHT) and fresh-keeping milk put forward strict quality requirements for packaging. Here, it is mainly divided into three categories: fresh milk, fermented milk and milk powder

1.1. Fresh milk

fresh milk can be processed into different kinds of dairy products, and each product has different packaging requirements according to its own preservation characteristics. The most common are pasteurized milk and UHT milk

pasteurization is the most widely used fresh milk treatment method. High temperature instantaneous sterilization is generally used, that is, raw milk is heated to 70 ℃ ~ 72 ℃ for 10 ~ 20s. Pasteurization mainly kills bacteria in raw milk to ensure quality and drinking safety; At the same time, it can also eliminate other microorganisms and enzymes that can cause flavor changes, so as to prolong the shelf life of fresh milk. However, pasteurization can only kill 90% ~ 99% of microorganisms in milk, so its shelf life is not very long, and the required storage environment is low-temperature refrigeration. Light is an important cause of vitamin loss in pasteurized milk, and other nutrients will be decomposed due to photochemical reaction. Therefore, dairy packaging needs to be protected from light. Oxygen is also one of the important factors that can not be ignored. If there is too much oxygen in the top gap in the package or the container is too oxygen permeable, it will aggravate the oxidation reaction of dairy products in the package and rapidly reduce the quality. Commonly used packaging includes glass bottles, composite cartons and plastic bags. Ultra high temperature sterilization can make fresh milk continuously flow through the heating process. After a short time (1s ~ 2S) at high temperature (at least 135 ℃), it will be aseptic packaged immediately. The loss of back nutrients in UHT milk during storage depends on the storage temperature, the content of initial oxygen in the milk and the properties of packaging materials (oxygen permeability and light transmittance). The odor produced by oxidation reaction and fatty rancidity will also enter UHT milk. The expansion of these reactions depends on the oxygen content and storage temperature in the milk. Various types of packaging can be used to package UHT milk. Composite packaging with aluminum foil is the most commonly used. The aluminum foil layer is the main barrier layer, which can not only effectively prevent the infiltration of oxygen, but also preserve the flavor components in fresh milk

1.2 fermented milk

fermented dairy products are products made of fresh milk or its products after homogenization, sterilization and other process operations, and then fermented by microorganisms (such as, of course, very popular yogurt, yogurt, yogurt, etc.). Sour milk is a typical fermented dairy product. Different types of products can also be formed after adding fruits, fruit flavors or sugars. According to its existing form, it can be divided into solidification type (hard), stirring type (paste) and liquid type. Different from fresh milk, the content of carbon dioxide in fermented milk has an important impact on the change of flavor and the growth of microorganisms. At present, the packaging forms of fermented milk are also glass bottles, composite cartons and plastic bags (plastic containers, plastic cups)

1.3 milk powder

milk powder is also a kind of dairy product with large consumption. It is made of fresh milk or dairy products through spray drying. Oxidation reaction is one of the main factors for determining the shelf life of milk powder. To ensure or extend the shelf life of milk powder, sealed packaging must be carried out to reduce the impact of oxygen on the quality of milk powder. However, it should be noted that unlike liquid dairy products, the moisture resistance of milk powder packaging is as important as oxygen resistance. Commonly used packaging forms include metal cans, aluminum foil composite flexible packaging bags, and paper-based composite cans

2. The important test item of dairy packaging

through the description in the previous part, we should be able to conclude that light and the penetration of oxygen and water vapor are the main influencing factors of dairy quality. Among them, dairy products can avoid light completely. At present, the dairy packaging materials used have basically achieved good barrier to light. However, the realization of barrier is not so simple. On the one hand, it is directly related to the high cost of barrier materials. To achieve ideal packaging barrier, it will inevitably lead to high packaging cost and eventually increase the production cost of products, On the other hand, the way of multi-layer composite is a very suitable way to effectively improve the barrier, whether for composite cartons, composite plastic flexible packaging bags or composite plastic cups. However, the level of independent research and development of corresponding multi-layer composite production equipment and raw materials in China is not enough and mainly depends on imports, which is particularly prominent in the packaging of composite cartons. Therefore, although the high cost of dairy packaging has attracted extensive attention, it is still very difficult to replace this high-cost packaging material

in addition, with the decrease of the barrier property of the packaging materials used, it will lead to the increase of oxygen and water vapor penetrating into the packaging, or the faster speed of the filling gas seeping out of the packaging, which will eventually lead to the increase of oxygen content and humidity in the packaging, which are the main reasons for the deterioration of dairy products and dairy products. Therefore, it can be said that in a certain sense, for the same dairy product or dairy product (the processing process is the same), the barrier of packaging materials is the main determinant of its shelf life. Therefore, for dairy products and dairy products, the barrier detection of packaging materials is very important

how much will the different barrier properties of packaging materials affect the shelf life of dairy products? Here we list the barrier test data of some representative dairy packaging materials, and the difference is clear at a glance. The equipment used in the test are labthinkvac-v1 gas to regeneration full process penetrant (permeability test) and tsy-t3 moisture permeability tester

the samples listed in Table 1 basically contain all the packaging materials required for the packaging forms of dairy products and dairy products, such as paper plastic aluminum composite materials used in composite cartons such as roof bag and Tetra Pak bag, coating/composite packaging film used in aseptic packaging, PE black-and-white film most commonly used in mass packaging, and Al composite plastic flexible packaging film used in milk powder packaging. It can be seen from the data in the table that the paper plastic aluminum composite material used in the composite carton and the Al composite plastic flexible packaging film used in the milk powder packaging have the best barrier performance among all kinds of dairy packaging materials. The air and moisture permeability data are in the high barrier range. Of course, the corresponding cost is also very high. According to relevant information, the cost of a Tetra Pak bag is not less than 0.5 yuan. The coating/composite packaging film used in aseptic packaging is the second, which belongs to the range of medium barrier and the cost is moderate. The most common PE black-and-white film and milk film in packaging have the worst barrier performance. The air permeability data alone is thousands of times higher than that of paper plastic aluminum composite material and Al composite plastic flexible packaging film, and hundreds of times higher than that of coating/composite packaging film. Of course, the price is also the lowest, often less than 0.1 yuan

the selection of packaging materials and the selection of material structure and barrier are completely determined according to the predetermined shelf life of the product. For example, the shelf life of dairy products or dairy products packaged with paper plastic aluminum composite materials with high barrier performance and Al composite plastic flexible packaging film can often reach several months, and the requirements for the storage environment are not very high, so they basically do not need to be stored in the refrigerated environment. If the materials with low barrier performance are used, a large number of products may deteriorate in advance, or bring greater difficulties to transportation and storage. The shelf life of dairy products packaged with black-and-white film is only a few days. This product often consumes a lot and belongs to the type of fast production and fast sales. If the barrier of the packaging materials used is too good (such as the medium barrier materials), it will not significantly prolong the shelf life, but will increase the packaging cost of the products. Therefore, the packaging materials must be selected according to the characteristics and shelf life of the products. At the same time, the barrier of packaging materials can also be "customized" according to the needs of products, that is to design the structure of materials and select corresponding materials according to the required barrier. It can be seen from the data in the table that it is the same paper plastic aluminum composite material, but the gas resistance of sample 2 is not as good as that of sample 1, and the moisture resistance is better: it is the same PE film, but some have a barrier of more than 900, while others have to reach more than 1300. The improvement of barrier is based on the premise of increasing cost. Therefore, as long as the packaging materials can ensure the quality of products in the shelf life, there is no great benefit from one-sided pursuit of barrier

3. Summary

at present, China's domestic dairy packaging materials can meet the general quality assurance needs (combined with the barrier, light shielding, mechanical properties and sealing properties of the materials), but they still need to be imported in high-end dairy packaging. However, with the continuous introduction of new products and the promotion of new processing technology in the dairy industry, the research and development of new packaging forms and the use of packaging materials have also entered a period of rapid development. However, the requirements for the selection of materials are higher. Only by fully testing the properties of materials can we better ensure the quality of dairy products and the safety of consumers

reprinted from: China Packaging News