Food packaging Sterilization  is an essential step in the process of food processing, which is of great significance in the whole process of food production and consumption.

In daily life, the common packaging materials for food are 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, stretch film, common polyethylene plastic bags, etc.

Different packaging materials will determine the choice of sterilizer structure. For different packaging materials, sterilizers are available in different heating forms (steam, water bath, mixed steam and air, etc.) in order to obtain a better heating environment.

The following analysis is done for different packages. Which type of sterilizer is suitable for each type of packaging.

1. Glass bottle packaging

Glass bottles should be careful not to suddenly change the ambient temperature during sterilization. Glass bottles are rigid materials and are usually canned at high temperatures, so the pressure of glass bottle products at room temperature is lower than atmospheric pressure, i.e. negative pressure. (The purpose of the negative pressure state is that in the process of storage and transportation before consumption, once the material inside the bottle deteriorates and the activity of spoilage bacteria produces some gas, the pressure inside the bottle rises and the recesses of the cap are lifted. (To remind consumers that the contents of the bottle can no longer be eaten.)

However, during the autoclaving process, the pressure inside the glass bottle will increase. By over-pressure protection, the circulating water outside the bottle can be prevented from entering the bottle through the cap seal, and 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 use water shower autoclave.

2. Box, cup and bowl packaging

For this type of food packaging sterilization, the pressure needs to be strictly controlled during the temperature change, and the temperature change should not be too fast during the heating and cooling process. The purpose is to make the packaging material basically not subject to pressure difference, so that the packaging material can be well protected from deformation due to pressure during the whole sterilization process.
As mentioned earlier, the need to heat up and cool down all products in the sterilizer within a relatively small temperature range has high requirements for the heat distribution performance of the sterilizer. Suitable for water bath sterilization.

3. Plastic bottle packaging

The sterilization of PE bottles has its own special characteristics. The canning temperature is around 85°C, the strength of PE bottles will be reduced. This is before sterilization for loading and unloading baskets, transportation, etc. In the sterilization process, with the change of temperature, the density of the material inside the PE bottle will change, which directly affects the change of bottle shape. At the same time, PE bottles have a certain shrinkage in high temperature environment, so that the internal PE bottles show a slight negative pressure state under normal temperature conditions. For this reason, controlling different pressure at different stages and temperatures, during food packaging sterilization is a key factor. Suitable for water bath sterilizers.

4. Three-piece canister products

These products are mostly used for canning liquid materials, such as beverages, puddings, etc. Due to the high strength of the three-piece cans themselves, they can withstand a certain internal pressure and also a certain external pressure. In the filling stage, most of the three-piece cans are hot-filled, the cans will show negative pressure at room temperature, while in the high-temperature state of the sterilization process, three-piece cans have a certain internal pressure.
In view of the above characteristics of three-piece cans, if conditions allow, should try to use steam heating sterilization method, because steam sterilization of the highest thermal efficiency (steam carries the heat directly to the product without intermediate media).
The bottom cover of the three-piece can and the body of the can is mostly iron. In the steam sterilization process, due to the uniformity of heat distribution in the sterilization kettle, must be in a saturated steam state, and no oxygen, so you can avoid the tank body. The occurrence of oxidation rust. Another point is that the steam sterilization method of the sterilizer structure can realize the comprehensive use of energy and fully reduce energy consumption. Suitable for automatic rotary sterilizer.

5. Two-piece can products

These products are mostly used for beverages, cola and other canned liquid materials. Due to the low strength of the two-piece cans themselves, liquid nitrogen needs to be dripped into the cans before filling and sealing. After capping, the pressure inside the can increases after liquid nitrogen sealing, thus enhancing the strength of the can. In the high temperature environment during the sterilization process, the pressure inside the tank will increase significantly (the pressure inside the tank is about 0.52 MPa when the temperature reaches 121°C), and the safety pressure strength of the two-piece tank is only about 0.25 MPa or less pressure difference, so the pressure inside the autoclave needs to be controlled at 0.30 MPa.
Sterilization of the two-piece tank is carried out in the form of water addition. The heat distribution during heating and cooling is required to be as good as possible so that all products in the sterilization kettle can be heated and cooled within a small temperature range. Suitable for water immersion retort sterilizer.