Aseptic Filling: Process, Advantages, and Applications

What Is Aseptic Filling?

In aseptic filling, products are filled into containers that have also been sterilized in advance under sterile conditions following thermal or physical sterilization. This prevents microorganisms from entering and spoiling the product. As a result, shelf life is extended without the need for preservatives.

Since When Has Aseptic Filling Existed?

To gently preserve sensitive products, aseptic filling has now become a key technology in industries such as the food and pharmaceutical sectors. That was not always the case: previously, industrial food preservation relied on heat treatment in the final packaging—a process known as pasteurization.

In the 1960s, the development of aseptic processes was significantly advanced—partly due to the introduction of new packaging materials and partly due to the desire to better protect nutrients and active ingredients. During this time, the Blow-Fill-Seal (BFS) technology was developed, in which the containers are formed, filled, and sealed directly within the sterile process.
This process, developed primarily by Rommelag, has sustainably accelerated the industrial implementation of aseptic filling, especially in pharmaceutical production.

Today, highly automated filling systems ensure exactly that. State-of-the-art monitoring systems ensure consistent product quality.

How Does Aseptic Filling Work?

In aseptic filling, the product and packaging are brought together under sterile conditions to avoid any contamination. This can be achieved in various ways: in classical aseptic processes, the product and packaging are sterilized separately and then filled and sealed in a controlled environment, such as a cleanroom or under Grade-A Unidirectional Airflow (UDAF; formerly known as“laminar flow”) conditions.
Alternatively, the Blow-Fill-Seal (BFS) process enables the container to be formed, filled, and sealed directly from molten polymer—in a single, closed process step. Both methods meet the highest requirements for sterility and product safety, but differ in how the sterile environment is achieved.

The individual process steps:

Sterilization of the Product

The product to be filled (e.g., a pharmaceutical solution, milk, cosmetics) is freed from microorganisms. In the pharmaceutical industry, sterilization is typically achieved through terminal sterilization (e.g., moist heat) or aseptic processing with sterilizing filtration.

Sterilization of the Packaging

Not only the product but also the packaging—i.e., all containers, lids, and closures—are sterilized. This co-occurs with the sterilization of the product, but in a separate process. Possible methods include steam, hydrogen peroxide, or UV light. In BFS, the container is formed from molten polymer (parison), then aseptically filled and hermetically sealed; the inner surface is created under sterile conditions, so no separate packaging sterilization step is needed.

Filling in an Aseptic Environment

To prevent recontamination, that is, the unwanted reintroduction of microorganisms after sterilization, the next step is filling in a sterile environment, such as a cleanroom or under Grade-A UDAF conditions. In Blow-Fill-Seal (BFS), the critical zone is protected by Grade-A air. The background environment may be classified as Grade C for aseptic processing, depending on the design and controls (including personnel gowning, segregation, and airflow). This means that BFS has significantly reduced clean room requirements.

Sealing

The packaging is hermetically sealed immediately after filling. In BFS systems, sealing occurs directly after filling by heat-sealing the still-warm plastic form—without external contact.

In Which Industries and for Which Products Is Aseptic Filling Used?

In principle, both liquid and pasty or solid products are suitable for aseptic filling. This process is used wherever products

• require particularly high purity,
• must not contain preservatives,
• need to have a long shelf life.

This applies to various industries:

Pharmaceutical Industry

Especially in the pharmaceutical industry, there are specific regulations governing the filling of products and the entire production process, including the equipment. These are defined in the international standard “Good Manufacturing Practice” (GMP). It specifies the conditions and measures required to avoid contamination during the production of sterile products.

In the pharmaceutical industry, many products require sterility to be ensured throughout the entire production process. These include, for example:

• parenterals (SVP/LVP)
• Inhalation/respiratory solutions
• ophthalmic drops
• irrigation solutions
• Irrigation solutions

Cosmetics Industry

In the cosmetics industry, there are also numerous products where microbiological spoilage must be avoided, and no preservatives should be used. These may include sterile creams, lotions, or liquid soaps.

Food Industry

In the food industry, aseptic filling is a proven method, particularly for heat-sensitive products that do not require the use of preservatives. This often applies to liquid products such as milk, juices, sauces, cream, vegetable oils, and vinegar.
There are also many examples in the beverage industry, such as drinks in PET bottles or those in Tetra Pak packages, which remain stable for months without refrigeration, thanks to aseptic filling.

What Are the Advantages of Aseptic Filling?

The advantages of aseptic filling at a glance:

• Taste, color, vitamins, and nutrients are optimally preserved thanks to the gentle process.
• Products have a longer shelf life, completely without additives or preservatives. Additionally, the products do not require refrigeration.
• Since no cold chain is required, the process is also well-suited for global supply chains.
• At the same time, the completely sterile and automated filling process ensures maximum process reliability—from production to sealing.
• Depending on the product and application, various packaging formats can be filled, from portion pouches and bottles to bag-in-box systems.

What Is the Difference Between Aseptic and Sterile?

The terms "aseptic" and "sterile" are often used in context and cannot be strictly separated: sterile describes a state, while aseptic refers to the method or process.

The term “sterile” refers to products that are free from all viable organisms, including bacteria, viruses, fungi, and spores. EN 556-1 specifies when terminally sterilized medical devices may be labeled “STERILE” (target SAL ≤ 10⁻⁶). EN 556-2 covers aseptically processed devices. For medicinal products, the applicable references are EU-GMP Annex 1 and Ph. Eur. 5.1.1.

In contrast, “aseptic” describes the process or technique rather than the state itself. Aseptic filling refers to a germ-free manufacturing and filling environment. While sterility is the ultimate goal, the primary focus is on preventing contamination.

The aseptic process maintains the sterile state, while sterilization actively creates it.