• After developing a returnable PET bottle in 2020, Krones and Alpla are working to make its use more widespread.
    After developing a returnable PET bottle in 2020, Krones and Alpla are working to make its use more widespread.

Despite attractive environmental credentials, returnable PET containers remain a niche product. Krones and plastic packaging provider Alpla are working together to change that. This article first appeared in the October 2021 issue of Food and Drink Business.

The sustainability teams at Krones and Alpla have joined forces to see how they could better realise the potential of returnable PET containers. 

The result is a returnable PET container specially designed for chilled juice and dairy products.

Krones enviro representative Martina Birk says there are many reasons why sustainability issues are increasingly important when it comes to packaging decisions.

“Which type of packaging performs best from an ecological perspective depends on a number of factors and must be evaluated individually for each use case. 

“But returnable PET containers often don’t even enter into consideration in the first place, and yet they can offer outstanding environmental performance, especially if they are distributed mainly regionally,” Birk says.

Krones and Alpla teamed up to make these benefits available for a wide range of beverages.

Alpla returnables expert and project lead Jörg Schwärzler says the team wanted to look beyond the main current applications for returnable PETcontainers – soft drinks andwater.

“We were certain that, if we combined our expertise in materials science, preform design, container design, and systems engineering, we could find a solution for sensitive beverages like juices and dairy products. The option of using a 38-millimeter bottle neck offers particular advantages for sensitive returnable applications,” Schwärzler says.

Particular attention was given to the container cleaning process because PET is less heat-resistant than glass.

Krones developer Ines Bradshaw says, “We had to find a way to ensure both a high level of microbiological safety and a high number of use cycles while cleaning at lower temperatures.”

At Krones’ development plant for washing technology in Flensburg, Germany, a comprehensive testing program analysed the interaction of different bottle designs and cleaning processes.

“The tests provided us with a very clear picture of the respective thermal, chemical, and mechanical factors. We found that with the right combination of parameters – especially lye concentration, temperature, additive, and mechanical impact – temperatures around 60°C are sufficient to reliably remove even dried protein, fat, and starch contamination from the containers,” Bradshaw says.

The testing also discovered a key difference between the performance of returnable PETand returnable glass. 

Over the course of several cleaning cycles, the alkaline cleaning medium visibly roughened the surface of the glass bottle but not the PET containers.

For Bradshaw, such consistent container quality, particularly for sensitive extended shelf life beverages such as juice and milk in the cold chain, is an advantage that shouldn’t be underestimated.

Microbiological tests are currently being conducted to definitively establish whether the technology is safe. Initial results are very positive.

“Microbiologically, PET bottles that have gone through 25 cycles could not be distinguished from new ones,” Bradshaw says.

With this proof of concept, the project has reached an important milestone and is now preparing for technical field testing

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