Researchers look to nanotech to keep fruit fresh

[NEW DELHI] Researchers are working on 'nano-film' packaging materials to extend the shelf-life of fruit and vegetables and reduce huge post-harvest losses in South Asia.

The project follows studies at Tamil Nadu Agriculture University (TNAU) showning that a nano-film that emits a chemical vapour can extend the shelf-life of vegetables by up to 21 days without any deterioration in quality.

Now, researchers at TNAU have linked up with collaborators in Canada and India to test such novel nano-materials on mangos during a 30-month project launched in March.

The project involves the University of Guelph in Canada, TNAU in India, the Industrial Technology Institute (ITI) in Sri Lanka, and MYRADA, a nongovernmental organisation based in southern India.

K. S. Subramanian, professor at TNAU's department of nanoscience and technology, told SciDev.Net that the average person in India consumes only 80 grams of fruit a day — half the recommended amount — despite the country being a top fruit producer.

"The main reason [for the low fruit intake] is post-harvest losses," said Subramaniam, who heads the research project. A lack of cold storage and cold chain facilities within India means that at least 40 per cent of the fruit harvested is lost — worth around US$71 million (four billion Indian rupees).

To tackle the problem, the researchers are developing nanomaterials impregnated with synthetic versions of an agent called hexanal, which is found in trace amounts in plants such as beans and cucumbers.

Hexanal helps extend the freshness and shelf-life of fruit and vegetables by targeting an enzyme called phospholipase-D, which is responsible for fruit and vegetable deterioration. Farmers in some countries use hexanal sprays on crops, but this is not practical in hot countries where the chemical vapourises quickly.

The Canadian scientists developed the synthetic hexanal and the TNAU team is planning to test such hexanal impregnated into natural plant fibre. This fibre slowly releases the chemical onto the food to stop the enzyme activity.

Meanwhile, the Sri Lankan scientists will test hexanal embedded in a natural wax, which, if successful, would then be used for nano-film coating.

TNAU scientists have started spraying mango crops with hexanal in three mango-growing areas in southern India's Tamil Nadu state to test its effectiveness. They expect to have the novel nano-film ready for testing in the first half of 2014.

However, Alok Dhawan, director of the Institute of Life Sciences at Ahmedabad University and founder of the Indian Nanoscience Society, cautioned that nanofilms containing hexanal as packaging materials would need studies on the environmental impact. This is because consumers would throw the wrappings away, and they would be dumped in land-fills.

Hexanal's antimicrobial properties could also destroy some natural biodegrading bacteria in the environment, Dhawan added, suggesting that the effect on ecosystems would also need to be studied.