Technology and Applications of Fresh Milk Tetra Pak Filling Machines

I. Core Technology

The technological core of the Bailybao filling machine lies in achieving... Aseptic filling or Clean filling to ensure the safety and quality of fresh milk throughout its shelf life. Its key technical steps include:

1. Film sterilization technology (key pre-processing)
This is the first checkpoint for ensuring product safety. Common methods include:

Hydrogen peroxide bath sterilization method: This is the most classic and widely used technique. The packaging film is rolled and passed through a hydrogen peroxide bath at a specific concentration (typically 30–35%) and temperature (about 70℃) for a set period of time, thoroughly eliminating microorganisms on the film’s surface.

Hydrogen peroxide spray + sterile air drying: After the film has been sprayed with hydrogen peroxide, its surface is dried by sterile hot air that has been filtered through a high-efficiency particulate air (HEPA) filter, ensuring no residue remains.

Ultraviolet Sterilization: As an alternative method, ultraviolet light can also be used for sterilizing thin-film surfaces, which is more convenient and faster.

2. Technology for Establishing and Maintaining a Sterile Environment

Sterile chamber: The core area inside the machine—the filling and sealing zone—is designed as a sealed “sterile chamber.”

Clean laminar flow purification device: Clean air is continuously supplied into the chamber through a top-level Class 100 laminar flow purification filter, maintaining positive pressure inside the chamber and preventing bacteria-laden air from entering from outside.

Chemical sterilization: Before production, the entire material pipeline and sterile chamber must undergo thorough in-line cleaning (CIP) using high-temperature steam or chemical sterilants (such as hydrogen peroxide mist).

3. Precise Filling and Sealing Technology

Positive-displacement filling: High-precision piston cylinders are typically used for quantitative filling to ensure that each package of milk has a consistent volume.

Photoelectric Tracking and Longitudinal/Transverse Sealing: The machine uses photoelectric sensors to detect pre-printed color markers (markers) on the film, ensuring that the pattern position is accurate for each packaging bag. Then, it proceeds sequentially as follows:

Longitudinal sealing: Roll the flat film into a tubular shape and heat-seal the seam.

Transverse sealing and cutting: After filling is complete, a pair of heat-sealing heads simultaneously perform horizontal sealing on the top and bottom of the packaging bag and then cut it in the middle, forming a fully sealed, individual package. The control of sealing temperature, pressure, and time is crucial, directly affecting the strength and integrity of the seal.

4. Automation Control and Online Monitoring Technologies

PLC (Programmable Logic Controller) and HMI (Human-Machine Interface): Modern filling machines are all controlled by PLCs. Operators can easily set parameters—such as fill volume, temperature, and speed—via a touch screen, monitor operating status, and perform fault diagnosis.

Automatic correction: When the film deviates from its intended path, the system automatically adjusts itself to ensure continuous and stable production.

No membrane, no filling: When no film is detected, the filling valve will automatically close, preventing material waste and equipment contamination.

II. Main Applications

The Tetra Pak filling machine is primarily used for packaging liquid dairy products and similar liquid foods:

Fresh milk/Pasteurized milk: This is the core application. The equipment, operating in a clean filling environment, is connected to a pasteurization line and is used for packaging fresh milk with a relatively short shelf life (typically 7–21 days).

UHT milk/Long-life milk: When used in conjunction with ultra-high-temperature (UHT) equipment and filled under sterile conditions, this process can produce room-temperature milk with a shelf life ranging from 30 to 180 days.

Flavored milk: Such as chocolate milk, strawberry milk, and so on.

Yogurt drink (stirred yogurt): For packaging liquid or semi-liquid yogurt products.

Soy milk, plant-based protein drinks, fruit juices, etc.: The technical principle is similar and can also be applied to other liquid beverages.

III. Technical Advantages and Features

Cost-effective: The cost of BOPP film is significantly lower than that of carton-aluminum composite materials such as Tetra Pak and Combibloc, resulting in lower overall costs for both equipment and packaging.

Lightweight packaging materials: The finished product is lightweight, making it easy to transport and store, which helps reduce logistics costs.

High production efficiency: Highly automated, with an operating speed of up to several thousand packages per hour, making it suitable for large-scale production.

Good preservation performance: Multilayer composite films can effectively block light and oxygen, meeting the freshness preservation requirements for fresh milk.

Flexibility: By replacing the membrane rolls and adjusting parameters, it is possible to quickly switch over to produce products of different specifications and varieties.

Summary

The fresh milk Tetra Pak filling machine is a sophisticated system integrating mechanical engineering, automated control, microbiology, and aseptic technology. With its outstanding cost-effectiveness and reliable freshness-preserving capabilities, it has become one of the mainstream packaging solutions for liquid milk in China and around the world. As technology continues to advance, its safety, efficiency, and environmental performance will keep improving, ensuring that it will maintain a significant market position in the future.