Paper trays coated with a "concoction" of silver nanoparticles created by Indian researchers can extend the shelf life of eggs by up to two weeks, a scientist said on Wednesday.

The development is meant to help small village farms store eggs for longer periods of time and sell them accordingly without deterioration of egg quality.

"It is a concoction made of silver, gelatin and chitosan and you could paint it or spray on the paper trays. You can store eggs after the spray dries off and the eggshell contamination by bacteria is reduced because silver has an antibacterial effect," Gopal Dhinakar Raj, of Tamil Nadu Veterinary and Animal Sciences University (TANUVAS) in Chennai, told IANS.

The reduced surface contamination raises the shelf life of eggs from 10 to 14 days to 25 to 30 days, he said.

Published in June in the Bulletin of Materials Science, the study points out the "strong antimicrobial activity of the silver nanoparticles doped trays against commonly found bacteria on egg shells - Escherichia coli, Staphylococcus aureus, Streptococcus, and Salmonella species".

Though it is easy to prepare, Raj said that the concoction can only be applied to paper trays.

"The only drawback is it can't be coated on plastic trays. The cost of application on a six-egg paper tray is around Rs 4 to Rs 5, and so if you recycle the trays then the cost goes down as a coated paper tray has a shelf life of around nine months. Cost could increase if you use single time," said Raj, also director, Translational Research Platform for Veterinary Biologicals (TRPVB).

TRPVB is a partnership programme between Department of Biotechnology and TANUVAS.

"In village chicken farms, they get small numbers (only 5 to 10 eggs a day). With the coated paper trays, they can accumulate the eggs over a period of time and sell them," he added.

The other authors of the paper are Kaliyaperumal Viswanathan, M. Latha Mala Priyadharshini, Karuppasamy Nirmala and Muthusamy Raman.