Sterile Milk Packaging Technology: Sterile Paper Packaging Aseptic Soft Packaging As people's living standards continue to improve, people's consumption habits change and food structure improvement, people's health awareness becomes stronger and stronger, and the benefits of dairy products to people have been consumed by the majority More and more recognized. The rapid development of the Chinese dairy industry has brought opportunities for the dairy packaging industry. Due to the vast territory and geographical differences in China, long-distance distribution is an obstacle that must be resolved for milk with relatively strict preservation requirements. Sterile fresh-keeping packaging is an effective way to solve this problem. The greatest advantage of aseptic packaging is that, under aseptic conditions, the nutrients and flavors of the original food are retained to the maximum. Therefore, aseptic packaging is currently widely used in milk packaging. Common forms of aseptic milk packaging In dairy products, there are mainly two types of sterile fresh-keeping packaging: 1. Sterile paper packaging The material used for sterile paper packaging is essentially a composite material and is paper, Polyethylene, aluminum foil, and Sarin resin multilayer composite paperboard, in which paper is a structural material, and aluminum foil is a high barrier material. Sterile paper packaging mainly includes roof packs, brick packs, and pillow packs. Second, aseptic soft packaging Aseptic soft packaging materials used for aluminum / plastic composite film, packaging is packaged in bags, there are Gabriel Prepack and Finpack Finpack. The main manufacturers include KF in Germany and ELECSTER in Finland. Advantages of Sterile Milk Packaging Sterile packaging is defined as a process that includes the sterilization of packaging materials or containers, the incorporation of commercial aseptic products in an aseptic environment, and the formation of packaging containers that are sufficiently tight to prevent recontamination, such as Seal the seal. Because the product requires a long shelf life under non-refrigerated conditions, the package must also provide complete protection from light and oxygen. “Aseptic†means that no microorganisms are present or removed from the product, packaging, or other specific area; “sealing†is used to indicate a suitable mechanical property, ie not to allow any bacteria to enter the package or, more strictly, to prevent microorganisms And gas or steam enters the package. First, the advantages of sterile paper packaging: aseptic packaging of milk is a high-tech filling form, not only can improve the safety of dairy products, but also can expand the scope of product sales. Its advantages are: (1) the product does not require any additives to ensure that it is harmless to the body; (2) the product can maintain its original flavor; (3) the product can reach an ideal shelf life without refrigerating. Second, the advantages of sterile soft packaging: (1) low cost of packaging film, only one-fifth of the cost of aseptic brick packaging materials; (2) can purchase packaging materials from domestic suppliers, more convenient; (3) pollution Less, the plastic bag is easy to flatten, only water and non-toxic gas after burning, in line with environmental protection packaging requirements; (4) lighter package materials, reduce transport costs; (5) flexible packaging can be used hot water soaking and heating, convenient for drinking. Sterile Milk Packaging Equipment I. Sterile Paper Packaging System The paper roll forming and packaging system is the most widely used packaging system. The packaging material is continuously supplied by the paper roll to the packaging machine, and is filled, sealed and cut through a series of forming processes. (1) Vertical/horizontal sealing structure of aseptic paper packaging system The packaging material rises from the roll into the packaging machine and rises behind the packaging machine. The vertical sealing strip is heat-sealed to the side of the packaging machine. The vertical seal adhesive has the following two main functions: to strengthen the vertical seal joint and prevent product leakage. After bonding the longitudinal seal strips, the wrapper is coated with a hydrogen peroxide film on the rollers, followed by a pair of pressure rollers to remove the excess hydrogen peroxide solution. At this point, the wrapper has reached its highest position and then moves downwards to form a cylinder through the vertical seal heater and the guide wheel. Residual hydrogen peroxide evaporates through the heater and the product begins to pour. The liquid level of the product is always controlled below the horizontal sealing level. Two pairs of horizontal sealing presses continuously pull the wrapping paper over the packaging machine, and the product continuously enters the packaging machine. Horizontal sealing is accomplished in two steps, bonding and cutting. Effective bonding requires two major factors, namely temperature and pressure. The temperature at the time of sealing is generated by the induction heating, and the cylindrical tube is clamped by the clamping jaws so that the paper tube becomes a rectangle. The product is squeezed by the pressure of the jaws in the sealing area, and the U-shaped metal ring in the jaws is fed with high-frequency current. The high-frequency current forms a reverse inductor current in the aluminum foil layer of the packaging paper, so that the aluminum foil is heated and will Heat is transferred to the inner polyethylene to melt it. Under the pressure of the jaws, the polyethylene is cooled rapidly at the same time, the melted polyethylene is cured, and the sealing is completed. The cutter in the jaws after sealing closes the package in the sealing area. The product is injected into the paper cylinder through the filling pipe, and its lower end is located below the liquid surface of the product, so that the formation of foam can be effectively prevented. The infused, sealed package is passed through a terminal former and the top and bottom corners are each bent, folded, and bonded to form. (2) Formation of sterile paper packaging environment The hydrogen peroxide sterilization of paper packaging system is usually divided into the following two steps: First, the formation of hydrogen peroxide film. A uniform coating of hydrogen peroxide on the surface of the packaging paper prior to sterilization is a prerequisite for its sterilisation. This process of an open aseptic packaging system is achieved by a dual oxygen tank. When the open aseptic packaging system is working, the wrapper is pasted to the double oxygen tank, and a layer of hydrogen peroxide film is attached to the product contact surface of the wrapper by a set of roller system, and part of the surface of the wrapper paper is attached. Microbes. The hydrogen peroxide used here must contain a wetting agent (PSM) to reduce the surface tension of the hydrogen peroxide, otherwise it may not be evenly coated with a hydrogen peroxide membrane because the product contact surface (polyethylene) is hydrophobic. The amount of wetting agent and the like is about 0.3%. Hydrogen peroxide sinks do not sterilize the packaging paper because the temperature is low and the desired sterilization efficiency cannot be achieved. Instead, it attaches a layer of hydrogen peroxide film to the wrapping paper for subsequent sterilization. It is worth noting that after the hydrogen peroxide coating is applied, the entire wrapper is exposed to the air and moves forward. Therefore, it is very important that the package has a stable temperature and humidity. Otherwise, it will affect the evaporation of hydrogen peroxide and eventually affect the Packaging paper sterilization effect. Second, the sterilization of wrapping paper. The coated paper coated with hydrogen peroxide film is passed through a pressing roller to remove the excess hydrogen peroxide, formed by a guide roller, a forming ring, etc. down to a tube heater and a transverse sealing area. Packaging paper is sterilized by the use of a tube heater for the hydrogen peroxide heater. The tube heater is an electronic component wound around the outside of the product infusion tube. It extends up to the middle of the paper tube. According to the size of the packaging volume, the temperature range of the tube heater is also different, generally in the range of 450 ~ 650 °C. The tube heater heats the inner surface temperature of the wrapper to 110-115°C by conduction and radiant heating, and the hydrogen peroxide evaporated into gas greatly improves the sterilization efficiency. Therefore, the sterilization of the wrapper is completed in this process. In the actual production process, in order to prevent microbial contamination, on the one hand, hydrogen peroxide gas evaporating in the area of ​​the tube heater rises, and on the other hand, sterile air is continuously fed into the cylinder, so that both form a gap between the wrapping paper. Bacteria air barrier. Second, aseptic soft packaging equipment Aseptic soft packaging production line has a variety of forms, the main principle is: the processed liquid raw materials after ultra-high temperature sterilization equipment, packaging under aseptic conditions, each processing step has a high degree of automation And to improve the safety of asepsis, after the various procedures have been scientifically arranged and set up, various kinds of accessories have been combined into a united body to work in harmony. Here's a brief introduction to the working principle of an aseptic packaging machine: First of all, steam is used to sterilize the equipment pipelines, and the steam pressure is 3.5 bar (140°C) for 30 minutes. During the production, steam is located at the periphery of the equipment pipeline and the pressure is stabilized at 1.2 bar, forming a sterile barrier to the equipment. The entire device sterilization time is about 35min. The cavity of the filling chamber was sprayed with H2O2 water mist for 25 minutes, and the infusion head was soaked in H2O2 solution for 10 minutes. Sterility was achieved by the oxidation of water. And use sterile hot air at 45 °C to maintain sterility. The plastic film for packaging was sterilized with 18~45S soaked in 35% H2O2 through a H2O2 pool. H2O2 has a broad bactericidal effect on microorganisms due to its strong oxidizing properties. Its bactericidal effect is related to temperature and concentration. Ultraviolet-assisted sterilization (wavelengths of 2500A to 2600A for UV rays, 2537A for light wavelengths of 30W U.V. lamps), and drying by sterile air. The products sterilized by ultra-high temperature equipment (UHT) remain aseptic and sealed after entering the filling machine. The products filled under the above-mentioned aseptic tank and sterile plastic film are stored at room temperature, and the shelf life of milk can reach 45 days or even more. long. The status quo of sterile milk packaging and the development of aseptic packaging technology were introduced as early as half a century ago. They began to be used in the European market in the early 1960s and are currently used to package liquid foods such as fresh milk and beverages. At present, aseptic packaging accounts for only 10% of dairy products in China, while developed countries account for 65%. In addition, the per capita amount of milk in China is 5.1kg, while the world average is 38kg. Now, the country has listed liquid milk aseptic packaging as a priority development project and spent RMB 2 billion to support the development of the liquid milk industry. This shows that China's aseptic packaging of liquid milk has great room for development, the market has a bright future, but also brings new opportunities and challenges for plastics research institutes.
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