Intelligent wrappers which biodegrade

Food of the future could come wrapped in smart plastic that detects contamination - and then biodegrades once thrown away.

The news is reported in the latest edition of the Royal Society of Chemistry's Journal of Materials Chemistry.

Dr Andrea Pucci and his team at the University of Pisa have developed the polymer film, which has properties which reveal exposure to stretching stresses and raised temperatures.

Dr Pucci said: "The film is stable in the atmosphere, but once the food is unwrapped the discarded film will be broken down by micro-organisms found in soil and fresh or sea water."

The film is made from a commercially available polyester, which is mixed with a cheap and readily available stilbene dye called BBS. 

Dr Pucci said: "Stilbene dye complies with US Food and Drug Administration regulations so could be used in food packaging."

The dye particles clump together to form aggregates throughout the polymer film - and give off a green luminescence under UV light. 

When the film is stretched or deformed, the dye aggregates are pulled apart and the molecules stop interacting - turning the luminescence blue.

Temperature changes also affect the aggregation and shift the luminescent output of the film.

Dr Christoph Weder, a pioneer in "smart" polymers at Case Western Reserve University, Cleveland, US, said he was thrilled by the new work.

He said: "Pucci has shown that these concepts can be extended to commercially available dyes rated as food compatible - which is an important achievement from a technological point of view."

Dr Pucci said: "The next challenge is to develop composite films made entirely from food-grade materials, and films with a wider activity. 

"The future of this field is based on the formulation of nanostructured sensors sensitive to a broad range of external stimuli."

with thanks to James Mitchell Crow for the original article.