The Filling Technology of Liquid Food (Part Two)
3. Comparison between hot filling and cold-aseptic filling
There are many packaging types for liquid food, including glass bottles, cans, PET bottles and compound soft packaging. At present, the most popular packaging type is PET bottles. The following are simple comparisons between PET bottle hot filling and cold-aseptic filling.(1) Process comparison
For packing materials, the two filling techniques have different requirements for PET bottles. Hot filling requires that PET bottles can withstand the high temperature between 85℃ and 92℃ and keep good heat resistance. Therefore, the PET bottles used for hot filling have thick walls, and the ribs of the walls can prevent thermal contraction, which greatly limits the bottle design. Besides, the price of heat-resistant PET bottles and caps is relatively high. In contrast, cold-aseptic filling can use ordinary light bottles (The highest heat-resistance temperature is between 60℃ and 70℃) and standard caps, thus greatly reducing the cost of bottles and caps. Also, ordinary PET bottles can be freely designed in any type.
In terms of technological processes, it is unnecessary to sterilize the bottle and cap separately before hot filling. After filling, the bottle should be tilted to sterilize the cap with the heat of the product. For medium temperature hot filling, pasteurization is needed later.
Before cold-aseptic filling, products, bottles, caps and filling equipment should be sterilized. Because ordinary PET bottles and caps are not heat-resistant, they need to be sterilized with chemical reagents. To ensure that the bottles and caps can be effectively disinfected, and chemical reagents will not affect the liquid food, the following measures are generally taken for cold-aseptic filling.
- The original number of bacterial colonies of blown bottles should not exceed 5 CFU/bottle.
- Bottles are conveyed by air conveyor in the sterile environment.
- The inside and outside of the bottle should be sterilized with disinfectant.
- There is an automatic recovery and concentration determination system to ensure stable concentration of disinfectant.
- Rinse the residual disinfectant in the bottle with sterile water and dry up the bottle with sterile air.
- Because the PET bottle will not contract after cold-aseptic filling, there will be a part of air between the liquid food and the bottle cap, and the oxygen between them will slowly oxidize the liquid product, causing the product to go bad. Therefore, a set of nitrogen gas (or other inert gases) replacement system will be added to cold-aseptic filling equipment to blow away the air at the top of the bottle and ensure that the product is not oxidized.
As far as the production management is concerned, the technical content of cold-aseptic filling is very high so that high-level technicians and high-quality managers are required to manage the filling in a unified way. Generally, the HACCP system is applied. A document system should be formed in the management, and someone is put in charge of implementing the system. The workshop environment of cold-aseptic filling is also strictly controlled. The purification of the filling area reaches class 100, and the purification of the bottling room and bottling line at an early stage reaches class 10,000. When the operators enter the class 10,000 cleanroom, they should be sterilized to reduce man-made pollutants.
(2) Product quality
The longer the heat treatment time is, the greater the influence on the quality and taste of the liquid product will be. Cold-aseptic filling usually uses ultra-high temperature instantaneous sterilization (UHT), and the heat treatment time of the product is extremely short (not more than 30 seconds). However, for hot filling, the loss of the heat-sensitive nutrients of the product such as vitamins is large because the product is in high temperature for a long time. And the taste and color of the product are also greatly affected.
(3) Costs
In terms of production costs, heat-resistant PET bottles and caps are needed for hot filling, and they are more expensive and heavier than ordinary PET bottles. Although cold-aseptic filling has an additional cost of disinfectant, the overall production costs of cold-aseptic filling are still lower than those of hot filling. Besides, the cold-aseptic filling line has high production speed, and the higher the output is, the more obvious the advantage of production costs will be.
With regard to equipment costs, the input costs of the two filling lines are quite different. Because the process of cold-aseptic filling is complicated and there are lots of auxiliary equipment around the filling equipment, the investment costs of the cold-aseptic filling line are much higher than those of the hot filling line.
By comparison, it can be seen that the investment costs of cold-aseptic filling are relatively high, but its production costs are relatively low. In the long run, cold-aseptic filling will have a clear cost advantage.