Two major players in the packaging space, German packaging and bottling machine manufacturer Krones and Alpla, the packaging experts from Austria, have developed a project designed to examine the potential of using returnable PET containers in beverage packaging. Until recently, returnables played only a minor role in the discussion about sustainability and PET plastic, with the emphasis having been heavily on reduce and recycling. Undeservedly so, according to the two partners in this project, of which the first phase was recently completed. According to the results of the scientific evaluation of the material and process parameters carried out, returnable PET containers were certainly a feasible option, even for sensitive, extended shelf life products such as juice and milk in the cold chain. Until now, the main applications for returnable PET containers have been carbonated soft drinks and water.
The best choice of packaging - from an ecological perspective - depends on a number of factors and must be evaluated individually for each use case, said Martina Birk, who is responsible for the enviro-sustainability programme at Krones. And, while they can offer outstanding environmental performance, especially if they are distributed mainly regionally, they often don’t enter into the equation in the first place, she added.
The companies set up the project to find a solution for sensitive beverages like juices and dairy products.
It was found that using a 38-millimetre bottle neck offered particular advantages for sensitive returnable applications, said Jörg Schwärzler, returnables expert and project lead at Alpla. Special attention was given to the cleaning processes used to sanitise the returns.
“PET is less heat-resistant than glass,” explained developer Ines Bradshaw. “So 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.”
Extensive testing was performed, which showed that, with the right combination of parameters – in particular the lye concentration, temperature, additive, and mechanical impact – temperatures of around 60 °C were sufficient to reliably remove even dried protein, fat, and starch contamination from the containers, said Bradshaw.
A direct comparison between returnable PET and returnable glass brought to light another interesting discovery: over the course of several cleaning cycles, the alkaline cleaning medium visibly roughened the surface of the glass bottle, a phenomenon not observed in the PET containers. “For the filling of sensitive beverages in particular, consistent container quality can be an advantage that should not be underestimated,” she added.
Microbiological tests are currently being conducted to definitively establish whether the technology is safe. The initial results are very promising.
“Microbiologically, PET bottles that had gone through 25 cycles could not be distinguished from new ones,” said Bradshaw.
With this proof of concept, the project has now entered the following phase. Preparations are already well underway for the technical field test.