Engineers at Harvard University have developed a biodegradable coating to keep fruit and vegetables fresher and safer for longer. 

Existing antimicrobial food films often require large quantities of active ingredients. 

But the experts say that fibre-based coatings are an inexpensive alternative because the fibrous materials have high surface-to-volume ratios, which may enable more efficient use of the antimicrobial agents within them. 

However, low-throughput production and a reliance on potentially harmful substances and chemical processes has limited the current use of microfibres in food packaging.

Harvard researchers have trialled a coating system using pullulan, a naturally occurring substance that is safe to consume and is biodegradable. 

Testing it on an avocado, they found the fruits were less prone to rotting or discolouration and maintained their weight better.

This was made possible by a high-throughput fibre spinning system that enables the one-step synthesis and direct coating of antimicrobial fibres onto fresh foods without further treatment. 

The fibres are made of pullulan - a naturally occurring polysaccharide that is designated by the United States Food and Drug Administration as ‘generally regarded as safe’ - and naturally derived antimicrobial agents, such as thyme oil and citric acid. 

The researchers have demonstrated the scalability of the approach, which can produce fibres at a higher production rate (0.2 grams per minute) than popular electrospinning fibre-production techniques (0.01 grams per minute). 

The antimicrobial pullulan fibres were also found to be biodegradable in both liquid and soil environments, and when used to coat avocados resulted in reduced rotting, weight loss and discolouration, as compared with controls.

The researchers say that the water-based synthesis process - along with the edible and washable nature of pullulan, and high-throughput fibre technology - presents a promising strategy to inexpensively package perishable food products.

More details are accessible here.