1. Introduction to aseptic packaging of milk
Aseptic packaging is specialized technology where packaging materials are sterilized and packed with sterile products under sterile environment. This method prevents microbial contamination of food products along with preserving the flavor and nutrient contents of the product. This method finds application in various food products such as milk, fruit juices and concentrates, soups, yogurt, cream, etc.
2. Aseptic packaging process for milk
2.1 Sterilization of milk
Raw milk is sterilized using UHT treatment where the milk is subjected to elevated temperature of 135°C with a holding period of 2-5 seconds. This method helps to eliminate all spoilage microorganisms including spores revealing a commercially sterile product. Flash heating can prevent heat damage to the milk. Hot milk is then cooled to room temperature before filling in sterile containers.
2.2 Sterilization of packages
Some common packages used for aseptic packaging are:
- Bottles and jars
- Carton boxes
- Tetra packs
- Metal cans
- Bags and pouches
- Plastic cans
For the sterilization of aseptic packaging materials, heat, chemical and radiation are used as the sterilizing agents. Heat is one of the common agents which is used to sterilize packaging materials, product supply lines and equipment. The two methods heat sterilization are moist heat (121-129°C) and dry heat (176-232°C), where dry heat require more temperature load due to the high resistance of bacterial spores to dry heat. 30-35% Hydrogen peroxide is the common chemical agent used for sterilization, followed by a hot air treatment at 60-65°C to remove the residual chemical from the materials. Additionally, gamma radiation has also been used for sterilization for decades.
2.3 Aseptic filling and sealing
Sterile milk and containers are brought together in sterile conditions for aseptic filling and sealing. Filling and sealing of the packages are achieved in such a way that there is no contamination prior and post sealing.
3. Packaging materials used for aseptic milk packaging
3.1 Tetra packs
Tetra packs (light weight packages) are made of 6 layers of materials having different functions:
- Polyethylene (PE): Moisture barrier
- Paper: Stability & strength
- Polyethylene (PE): Adhesion
- Aluminum (Al): Oxygen and light barrier, prevents flavor migration
- Polyethylene (PE): Adhesion
- Polyethylene (PE): Seals in the liquid
3.2 Plastic bottles
Plastic bottles are durable, recyclable, and easy to mold into different shapes. The most common among them are High-density polyethylene (HDPE) and polyethylene terephthalate (PET). PET provides a good oxygen barrier but is typically combined with additional barriers or coatings for enhanced protection. Primarily used for single-serve or refrigerated products, though it is increasingly used in aseptic applications with additional barrier layers or treatments. Lightweight, impact-resistant, and provides excellent visibility (in the case of clear PET), making it easy to monitor product quality.
3.3 Flexible pouches
For milk packaging, 3-sided sealed pillow pouches (Polyethylene or polypropylene) are used. Often consists of multi-layer films, including polyethylene, aluminum, and polypropylene, designed to provide flexibility and barrier properties. These are lightweight, flexible, and efficient in terms of space and storage; suitable for single-serve or small-format packaging. Some examples of flexible pouches include stand-up pouches, spouted pouches, and pillow pouches.
3.4 Glass bottles
Although less common, glass bottles can be aseptically filled and sealed with a sterilized cap. Glass provides an excellent barrier against oxygen and light, preserving taste and nutritional quality. These are often used for premium or specialty milk products where consumers prefer glass for taste and environmental reasons. Glass bottles are 100% recyclable, provide high protection from external factors, and maintain product quality for an extended period.
4. Benefits of aseptic packaging
4.1 Prolonged shelf life:
Aseptic packaging technology extends the shelf life of the milk up to 12 months.
4.2 Retention of flavor and nutritional quality:
Flash heating and cooling minimizes the quality losses of milk, resulting in the preservation of flavor and nutrients.
4.3 Convenience in portability and storage:
Aseptic milk can be stored for a long time since it cannot be spoiled easily, which also makes transportation simple and effortless. Less energy is required for storage and transportation.
5. References
5.1 https://www.icpe.in/icpefoodnpackaging/pdfs/23_aseptic.pdf
5.2 https://www.eagleflexible.com/about-us/blogs/what-is-aseptic-packaging/
5.3 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations
5.4 https://gcwgandhinagar.com/econtent/document/1586855092AsepticPackaging.pdf
PMG stands for Projects Management Group. We provide world-class Engineering Services to build great food processing factories. 
Engineering is the difference between Chaos and Excellence. If you are going to do it, do it right. 
Explore the diverse range of Products in the Food Processing Industry. 
Explore the technologies at the heart of the the Food Processing Industry. 
Filter
