Development of polyhydroxyalkanoate composites based on food industry by-products for compostable packaging

Abstract

The high cost, small processing window and poor mechanical properties of polyhydroxyalkanoates (PHA) hamper their use in demanding packaging applications such as thin films. We report here on the first year of activity of a national project aiming at developing new PHA based composites for packaging applications.

New PHA obtained from mixed microbial cultures were designed to meet specific valerate contents. Model mixed cultures were first used and a process was optimized using cheese whey, a by-product from the dairy industry. The mixed microbial cultures concept will be briefly presented together with the preliminary PHA properties, prior to the scaling up of the production.

A second action of the project aimed at developing PHA composites using beer spent grain fibers ontained from by-products from the beer brewing industry and commercial PHA. The screening for the compound composition and processability was performed using a mini extrusion line coupling a small scale (30-100 g/hour output) twin screw extruder to a slit die to shape small films, further drawn down with a haul off. With such small scale equipment, various compositions were tested and characterized in terms of rheological melt properties and processability, along with the small film mechanical properties. As a result of this screening, two composites were selected for scale up of the compounding and further used in a film blowing lab scale line to produce thin films. The mechanical and structural characteristics of blown films will be reported

Acknowledgements. The authors thank Fundação para a Ciência e a Tecnologia (Portugal) for funding through project PTDC/AGR-ALI/122741/2010.