How to choose a retort machine according to the product packaging
Commonly used packaging materials for sterilizing pots include PE bottles, aluminum foil boxes, high temperature resistant plastic boxes, air bags (self-standing bags), vacuum bags, three-piece cans, two-piece cans, glass bottles, PVDC casings. Class, stretch film, ordinary polyethylene plastic bag… and many more
The difference in packaging materials will determine the choice of structure for the sterilization kettle. Because for different packaging materials, in order to obtain a better heating environment, there are different heating forms of the sterilization kettle (steam, water, water bath, steam and air, etc.);
The difference in the contents of the packaging material will determine the sterilization process (heating, heat preservation, cooling, and the pressure change corresponding to each sterilization stage) and the structure of the sterilization kettle in the sterilization process to adapt to the state of the sterilized material. , turning, shaking, etc.).
The following analysis is performed for different packages. What type of retort machine is suitable for each package.
Glass bottle packaging products
Glass bottles should be aware that the ambient temperature cannot be changed suddenly during the sterilization process. Glass bottles are rigid materials, usually filled with high temperature, so that the pressure of the glass bottle products under the normal temperature state is lower than the atmospheric pressure, that is, the negative pressure state (A purpose of the negative pressure state is that during the storage and transportation process before consumption, once the material in the bottle deteriorates and the activity of the spoilage bacteria generates some gas, the pressure in the bottle rises, and the bottle cap of the depression is raised. Remind consumers that the contents of the bottle can no longer be eaten).
However, during the high temperature sterilization process, the pressure inside the glass bottle will increase. To prevent the circulating water outside the bottle from entering the bottle through the cap seal, the pressure outside the bottle should not be higher than the pressure inside the bottle. According to these characteristics, for glass bottle packaging products, it is appropriate to select a spray type sterilizer.
Iron can packaging materials
This kind of packaging material seems to be an iron can, but because of its large size, its resistance to pressure difference is relatively weak, so in the sterilization process, the pressure control in the sterilization kettle needs to strictly follow the temperature change. Make adjustments so that the pressure differential experienced by the can is controlled to an acceptable level. It should be noted that the pressure corresponding to the same temperature is different between the heating phase and the cooling phase. Because the heating phase is to transfer heat to the inside of the product, the temperature in the tank is lower than the temperature in the sterilization kettle, the pressure required in the sterilization kettle is lower; and in the cooling phase, the heat inside the product is emitted outward, the can If the temperature in the body is higher than the temperature in the sterilizer, the pressure required in the sterilizer will be higher, which is to be noted. For different product specifications and different contents, the controlled pressure is also different and needs to be set specifically.
Plastic packaging stretch film packaging
The sterilization of such products is still a value that requires strict control of the pressure during the temperature change process. Because there is a certain amount of air inside the box, the heat transfer is slow, so the temperature change should not be too fast during the heating and cooling process, and all products placed in the sterilization kettle should be synchronized in a small temperature range as much as possible. The purpose of the ground heating and cooling is to make the packaging material basically not to withstand the pressure difference, so that the packaging material can be well protected from deformation due to the pressure during the whole sterilization process. As mentioned above, it is necessary to raise and lower the temperature of all the products in the sterilization kettle in a relatively small temperature range, which has high requirements on the heat distribution performance of the sterilization kettle. Suitable for water bath type retort machines.
Box packaging
The sterilization of such products is still a value that requires strict control of the pressure during the temperature change process. Because there is a certain amount of air inside the box, the heat transfer is slow, so the temperature change should not be too fast during the heating and cooling process, and all products placed in the sterilization kettle should be synchronized in a small temperature range as much as possible. Warming and cooling the ground. The purpose of this is to make the packaging material substantially unaffected by the pressure difference, so that the packaging material can be well protected from deformation due to the pressure throughout the sterilization process. As mentioned above, it is necessary to raise and lower the temperature of all the products in the sterilization kettle in a relatively small temperature range, which has high requirements on the heat distribution performance of the sterilization kettle. Suitable for use in water bath type retort machines.
Cup-shaped packaging bowl-like packaging
The sterilization of such products is still a value that requires strict control of the pressure during the temperature change process. Because there is a certain amount of air inside the box, the heat transfer is slow, so the temperature change should not be too fast during the heating and cooling process, and all products placed in the sterilization kettle should be synchronized in a small temperature range as much as possible. Warming and cooling the ground. It is worth noting that if the air content in the packaging material is small, the problem of the product being compressed can be ignored, that is, the back pressure in the sterilization kettle can be increased, so that the sterilization kettle is always in the whole sterilization process. pressure. Since the material in the packaging material is incompressible and the air content is small, even if the external pressure is large, the deformation of the packaging material itself is not affected. Suitable for spray retort machines.
Sterilization of plastic bottles
The sterilization of PE bottles has its special characteristics. The materials in the bottles are generally hot canned. The canning temperature is around 85 °C, and the strength of PE bottles will be reduced. This is the loading and unloading baskets, transportation, etc. before sterilization. Links need to be noted. During the sterilization process, as the temperature changes, the density of the material in the PE bottle will change, which will directly affect the change of the bottle shape. At the same time, the PE bottle has a certain shrinkage in a high temperature environment, so that the inside of the PE bottle exhibits a slight negative pressure state under normal temperature conditions. To do this, the control of different stages, different temperatures, and different pressures during the high temperature sterilization process is a critical factor. Suitable for fully automatic spray sterilizer.
Three-piece can products
Most of these products are used for canned liquid materials, such as beverages, rice pudding and the like. Since the three-piece can itself has a high strength, it can withstand a certain internal pressure and can withstand a certain external pressure. In the filling stage, most of the three-piece cans are hot-filled, and the tank body will exhibit a negative pressure state at normal temperature, and in the high-temperature state during the sterilization process, the three-piece can has a certain internal pressure. In view of the above characteristics of the three-piece can, if conditions permit, the steam-heating sterilization mode should be used as much as possible because the thermal efficiency of the steam sterilization is the highest (the heat carried by the steam is directly transmitted to the product without the intermediate medium). The bottom cover and the body material of the three-piece can are mostly iron. During the steam sterilization process, due to the uniformity of heat distribution in the sterilization kettle, it must be in a saturated steam state, and there is no oxygen, so the tank can be avoided. The occurrence of oxidative rust. Another point is that the steam sterilization mode of the sterilization kettle structure can achieve comprehensive utilization of energy and fully reduce energy consumption. Suitable for fully automatic rotary sterilizer.
Two-piece can products
Most of these products are used for canned liquid materials such as beverages, colas, and the like. Due to the low strength of the two-piece can itself, liquid nitrogen is required to be dripped into the tank before filling and sealing. After the lid is sealed, the pressure inside the tank will be increased after the liquid nitrogen is sealed, thereby enhancing the strength of the tank. . In the high temperature environment during the sterilization process, the pressure inside the tank will increase to a large extent (the pressure in the tank is about 0.52 MPa when the temperature reaches 121 ° C), and the safe compressive strength of the two-piece tank is There is only a pressure difference of about 0.25 MPa or less, so the pressure in the autoclave needs to be controlled at 0.30 MPa. The sterilization of the two-piece cans is in the form of watering up. The heat distribution in the process of heating and cooling is required to be as good as possible, so that all products in the sterilization kettle can be heated and cooled in a small temperature range. Otherwise, it is necessary to add several times to suspend the temperature rise and cool down during the process of heating and cooling, in order to synchronize the temperature of all products in the sterilization kettle. Suitable for fully automatic spray sterilizer.
Ordinary polyethylene plastic bag
Here, the packaging is commonly used in the sterilization of edible fungus bags. Because the bag has low strength, is easy to be broken, and the sterilization requirements are not high, steam-type retort machines are often used. In order to further reduce the cost, a manual carbon steel one-bedroom steam retort machine is often used.
