Sterile Blow-molded Bottle Packaging of Dairy Products
By increasing the shelf life of products, we can expand the sales channels and market share. Therefore, the progress of packaging technology of liquid dairy products is of great significance to large dairy production groups, but it is a contradiction between improving the shelf life and keeping the taste of liquid dairy products and keeping the appropriate cost. With the emergence of aseptic blow molding bottles and aseptic filling technology, a balance point has been found.
The composition of milk is very complex, and the vitamins in it are very sensitive to light. Ultraviolet and visible light can be absorbed by vitamins at 500nm, resulting in the loss of vitamins. Experts found through experiments (taste and gas) that when milk is exposed to light for several hours, the taste will change. Therefore, it is necessary to have barrier packaging containers and appropriate sterilization technology.
Sterilization technology and aseptic filling The storage life of dairy products mainly depends on the influence of bacteria, yeast and granular objects on them. There are many ways to extend the shelf life of products. The traditional method is to first fill the product into the packaging container and then heat the product and the packaging container at a high temperature of 118℃-129℃. Heat and sterilize together. This method of heating disinfection is suitable for containers such as metal cans, glass cans, glass bottles and plastic HDPE bottles. In Europe, this method is widely used in the field of milk packaging. To realize this process, a hydraulic disinfection tower is a common technology. In the hydraulic disinfection tower, the pressure outside the bottle can offset the internal pressure caused by the high temperature of 118℃-129℃ inside the bottle, thus avoiding the deformation of the bottle. Although these methods are safe and effective, they are limited in application, such as the limitation of container shape. In addition, the glass container needs to be slowly heated and cooled to prevent its breakage, and the taste of the product is easy to change at high temperatures. The resulting problem is that the final product packaging shapes of various manufacturers are similar and lack creativity. So the aseptic packaging method was conceived. The aseptic packaging process is to sterilize the product and the packaging container respectively, and then carry out aseptic packaging with an aseptic filling machine. Its advantages are instant high-temperature sterilization, reducing the risk of product taste change, adapting to various packaging methods and shapes, and sterilizing according to the packaging forms required by users, such as tetra pack, aseptic plastic bag packaging, etc.
Blow molding sterile plastic bottle Among all kinds of aseptic packaging, the plastic bottle is the most economical one. In particular, the aseptic plastic bottle molded by blow molding not only has all the advantages of ordinary plastic bottle packaging, but also can be made into multi-layer co-extrusion and in-mold labeling, so that the packaging effect is colorful, and the handle can be made for convenient use, and the cost can be reduced. The blow-molded sterile plastic bottle is a kind of plastic bottle that is completely sterile inside and free of yeast and other loose particles. Due to the sealing of the bottle mouth, the bottle is always kept sterile during storage and transportation to the aseptic filling machine. Just before filling, sterilize the outside of the bottle body with sterile liquid to ensure that the whole processing process such as re-opening, filling and re-sealing the bottle can be carried out in a sterile state. Compared with high-temperature sterilized plastic bottles before filling, aseptic blow bottles have higher reliability and lower cost. The principle is simple. Instead of cleaning and disinfecting dirty objects, it is better to make them pollution-free from the beginning. After the bottle is formed, it is sterilized, which not only has a high cost, and complicated equipment but also has high technical requirements for workers.
Manufacture of an aseptic blow bottle During the blow molding process of the aseptic bottle, the plastic temperature is kept at about 200℃, which is recognized by the FDA as the condition of forming an aseptic surface. At this temperature, the air and metal contacting the container will not pollute the container. Blow-molded sterile plastic bottles adopt this principle. Usually, blow molding is extruding the molten plastic from an extruder to form a tubular or spherical parison, which is blow molded in a mold. During the mold closing process, the bottle blank is usually filled with low-pressure gas to ensure that the bottle blank will not be connected frequently before blow molding. The aseptic bottle blowing technology developed by TECHNE Company of Italy uses aseptic compressed air for blow molding, which eliminates any danger of polluting the inside of the bottle. The hollow needle is inserted into the dome at the upper part of the bottle structure in the mold, and then sterile air is blown in to form the designed bottle shape. In the process of blow molding, after the plastic is cooled by the mold, the gas is released, and then the bottle body is sealed by two independently operated mechanisms at the position between the insertion point of the blowing needle and the dome. This sealed area is isolated from the metal part with the cooling channel so that after the gas channel is closed by the sealing mechanism, the plastic in this area still keeps a high temperature and compatibility with the plastic itself. Because sterilization is closely related to the sealing process, two sealing processes are generally used to improve the reliability of sterilization. The reason for using two sealing processes is not the imperfection of one sealing device, but to reduce the risk of any pollution. The sealing process is completed before the bottle body is removed from the mold, thus avoiding the possibility of contamination. Then, the mold is opened, and the bottle body is taken out for trimming. Now the sterile bottles produced can be packaged, stored, shipped or directly sent to the filling process. When sealing the bottle, it is sometimes necessary to reduce the pressure to slightly lower than the normal pressure to ensure that the latent heat of plastic will not cause the deformation of the bottle when the gas is reheated after the bottle is sealed. It should be emphasized that during the whole blow molding process, the inside and outside of the bottle are completely isolated from polluted air, and only sterile compressed air contacts the inside of the bottle. In order to ensure the barrier property of bottles, a multi-layer co-extrusion process is needed. Sterile bottles for liquid dairy products are usually made of 3 or 6 layers of HDPE. TECHNE's multi-layer co-extrusion was originally used to solve the problem of waste leftover materials, mainly to reduce the number of raw materials and recover 10%-30% of the materials in each container, but it was widely used in the manufacture of milk products blow bottles. The inner and outer layers of the three-layer bottle body are white, and the middle layer is black, which plays an anti-ultraviolet role. Without refrigeration, the shelf life of the product is 3 months. The shelf life of products can reach 6-9 months by adding an EVOH barrier layer to 6-layer bottles.
How to ensure the sterility of compressed air Ensuring the sterility of compressed air is a key link. The compressed air can be sterilized by using the precision filter. When compressed air passes through a precision filter, bacteria and yeast can be filtered out. However, when the filter is used for sterilization, the air channel downstream of the filter must also be sterilized. At the same time, in order to meet the hygienic standard of milk production, all the air that comes into contact with the product should have a smooth passage, and at the same time meet other special requirements of product production. That is to say, all compressed air channels must be sterilized and kept sterile during the whole blow molding process. At present, many sterilization methods are complicated and costly. A simple method is to sterilize with the OXONIA active sterilizing agent of Henkel Company. The aseptic bottle and aseptic filling production line produced by this process has been produced and operated in some European milk factories for many years, and the practice has proved that it is safe and reliable.