r-PET, Innovation, Product Innovation

Heat sterilization of PET: A challenge for recycled material, an opportunity for the dairy industry

12/02/2024 | 2 min read

Matthias Eckerstorfer

Have you ever filled an ordinary PET water bottle with hot water? Maybe tea, just to finish it quickly in the car on the way to the office? Then you probably know that this was not a good idea: due to its chemical properties, PET changes its material properties as soon as it comes into contact with heat – and contracts. In the following article, we show why this physical phenomenon is a challenge for the use of recycled material for food packaging and what solutions are nevertheless available for the hot sterilization of PET.

The following topics will be covered:

PET + heat: the starting position
The solution: r-PET HTS^®
The advantages of r-PET HTS^®
Alternative UV sterilization

PET sterilization – an impossibility?

High filling temperatures are not uncommon, especially in the food sector, and there are many products – such as milk-based yogurts – whose packaging has to be sterilized at up to 100 °C before filling. This often rules out PET as the packaging material of choice, although it offers many other positive properties. In the food sector, only recycled PET is currently classified as a “suitable technology” by the European Food Safety Authority (EFSA) and can thus be used for food applications. Other mechanically recycled materials cannot currently be used for food packaging or are only available to a limited extent. Mechanically recycled PET, on the other hand, has been available for many years thanks to the existing recycling loop.

When things get hot – heat-resistant r-PET cups

So, if only r-PET can be used as a material for food packaging, but it is unable to withstand the necessary filling temperatures or cannot be heat-sterilized, what is the solution? Greiner Packaging has also asked itself this question and has therefore developed a more heat-resistant PET cup that can withstand temperatures of up to 100 °C for short periods and can be made entirely from recycled material.
The r-PET HTS^® (“high-temperature sterilization”) innovation has opened up new opportunities for the dairy industry to package its products sustainably without having to make significant changes to the filling process. It is an innovative thermoforming solution for high-temperature sterilization (HTS) applications. r-PET HTS^® combines recycled PET with heat resistance. It is suitable for sterilized packaging before filling and improves the temperature stability and food safety of PET. The processing excellence of r-PET HTS^® lies in the combination of the right material and the adaptation of both the machine and the tool.

The advantages of r-PET HTS® at a glance

For short periods, r-PET HTS^® can withstand temperatures of up to 100 °C during the filling or sterilization process. Since every filling process is different in terms of duration and the corresponding exposure to heat, the exact limits are currently being explored in various projects.

PET has good barrier properties and protects the contents against the effects of oxygen from the outside.

Depending on the application and customer requirements, PET HTS^® packaging can also be produced in combination with recycled material. This saves on new material and thus conserves resources.

With a cardboard-plastic combination, high-quality printing on the packaging is possible, ensuring distinctive branding at the point of sale. The cup itself is not printed, so it remains easily recyclable.

Hot sterilization vs. UV sterilization

In recent years, UV sterilization has established itself as an alternative to traditional hot sterilization for disinfecting packaging materials. In this process, ultraviolet light is used to kill or deactivate microorganisms such as bacteria, viruses, and molds. UV sterilization requires less energy compared to conventional heat or steam sterilization methods, making it a more cost-effective and environmentally friendly option. Because the process takes place at lower temperatures, it is suitable for a wider range of materials, especially heat-sensitive materials such as certain plastics or composites used in food packaging.