Liquid Food Filling and Processing Technology

With the rapid development of the liquid food industry, the filling technology of liquid food has also developed rapidly. The filling technology of liquid food is mainly classified into two types: hot filling technology and sterile cold filling technology.

1. Hot Filling Technology

Hot filling technology refers to the filling of liquid food in a hot state after sterilization, using the heat of the product to sterilize the inner surface of the container. Hot filling can be divided into two types: high temperature hot filling and medium temperature filling, followed by heating the product to 65 ℃~75 ℃ for pasteurization. Hot filling technology does not require separate sterilization of bottles and lids, and only requires the product to be kept at high temperature for a sufficient period of time to sterilize the bottles and caps.

2. Sterile cold filling technology

Sterile cold filling technology refers to the cold (room temperature) filling of products under sterile conditions. The key control points for sterile cold filling technology mainly focus on the following three points: the formation and control of sterile environment, the formation and control of sterile packaging containers, and the formation and control of sterile products. In order to meet the requirements of sterile cold filling, the production line must meet the following basic requirements: the product must undergo ultra-high temperature instantaneous sterilization to achieve commercial aseptic state, packaging materials and sealed containers must be sterilized separately to achieve aseptic state, filling equipment must be sterilized to achieve aseptic state, filling and capping must be carried out in a sterile environment, the production process must be strictly controlled, and key control points must be established, monitored, recorded, and controlled.

3. Comparison between hot filling and sterile cold filling

There are many packaging forms for liquid food, including glass bottle packaging, Metal Can packaging, composite soft packaging, PET packaging, and so on. The most popular packaging method currently is PET bottle packaging. Below is a brief comparison between PET hot filling technology and sterile cold filling technology.

①Process comparison

From the comparison of packaging materials, the two filling methods have different requirements for PET bottles. Hot filling requires PET bottles to be able to withstand high temperatures ranging from 85 ℃ to 92 ℃ and maintain good heat resistance. Therefore, the PET bottles used have thicker walls and ribs to prevent thermal shrinkage. However, this greatly limits the freedom of bottle design, and the price of heat-resistant PET bottles and bottle caps is relatively high. Sterile cold filling can use ordinary lightweight bottles (with a maximum heat resistance temperature between 60 ℃ and 70 ℃) and standard caps, greatly reducing the cost of bottles and caps. In addition, ordinary bottles can also freely choose and design bottle types.

In terms of process flow, hot filling technology does not require separate sterilization of the bottle and cap before filling, but after filling, a bottle pouring process is carried out to sterilize the cap with the heat of the product. For medium temperature filling, subsequent pasteurization is also required. Before filling, sterile cold filling technology requires sterilization of the product, bottle, cap, and filling equipment to achieve a sterile state. Due to the heat resistance of ordinary PET bottles and caps, it is necessary to use chemical reagents to sterilize them. To ensure effective sterilization of bottles and lids without allowing chemical reagents to affect materials, aseptic filling technology generally adopts the following measures: a) The original bacterial count of blown bottles does not exceed 5cf/bottle; b) Using sterile air to transport bottles; c) Simultaneously disinfect the inside and outside of the bottle with disinfectant; d) Equipped with an automatic recovery and concentration measurement system for disinfectants, ensuring stable disinfectant concentration; e) Rinse the remaining disinfectant in the bottle with sterile water, and then blow dry with sterile air; f) Due to the fact that PET bottles do not shrink after cold filling, there will be some air between the material and the bottle cap, and the oxygen in it will slowly oxidize the material during storage, leading to the deterioration of the beverage. So, the sterile cold filling equipment will add a nitrogen (or other inert gas) replacement system to blow away the top air, ensuring that the material is not oxidized.

②Product quality

The longer the heat treatment time, the greater the impact on the quality and taste of the beverage. Sterile cold filling generally adopts ultra-high temperature instantaneous sterilization (UHT) technology, and the heat treatment time of materials is extremely short (no more than 30 seconds); Due to prolonged exposure to high temperatures, the hot filling materials result in significant loss of heat sensitive nutrients (such as vitamins) in the product, which also have a significant impact on the taste and color of the product.

③Cost

In terms of production costs, the difference between the two mainly comes from the difference in packaging raw material costs. Hot filling requires the use of heat-resistant PET bottles and caps, which are more expensive and heavier than regular PET bottles. Although sterile cold filling adds an additional cost of disinfectant consumption, the overall production cost is still lower than hot filling. And the sterile cold filling production line has a faster speed, and the higher its output, the more obvious the production cost advantage.
In terms of equipment cost, there is a significant difference in the input cost of the production line between the two filling methods. Due to the complexity of the sterile cold filling process and the need for more auxiliary equipment around the filling equipment, the investment cost is much higher than that of the hot filling equipment production line.

Through comparison, it can be seen that the initial investment in sterile cold filling is relatively large, but the production cost of sterile cold filling is relatively low. With the extension of equipment usage time, the low-cost advantage of sterile cold filling can be clearly demonstrated.