COLUMBIA, Mo. – Findings by University of Missouri scientists indicate that zinc oxide nanoparticles could be a weapon against harmful molds and bacteria in food.

“These results suggest that zinc oxide nanoparticles could potentially be used as an effective post-harvest antimicrobial agent in agricultural and food-safety applications,” said Mengshi Lin, assistant professor of food science.

“The use of nanoparticles has received a lot of attention for a wide range of applications, from engineering to human health,” said Alex Yang, recent food science master’s graduate. “Nanotechnology has not been widely applied to food science, but this is a promising area.”

Tests showed that these tiny particles inhibited growth of the bacterium E. coli O157, a source of food-borne illness, and two fungi that prey upon fruits, Botrytis cinerea and Penicillium expansum.

Nanoparticles are particles less than 100 nanometers in diameter. (A nanometer is one-billionth of a meter.) Nanoparticles in the study were about 70 nanometers in diameter, roughly a thousand times smaller than the width of a human hair.

In the fight against bacteria or fungi, size matters. The nanoparticles are small enough to penetrate the surface of their targets.

The scientists tested different concentrations of zinc oxide nanoparticles against E. coli growing in tryptone soy agar, a common bacterial growth medium. In bacteria, the nanoparticles distort and damage the cell membrane, resulting in leakage of intracellular content and eventual death of bacterial cells.

The nanoparticles also inhibited growth of fungi growing in potato dextrose agar. The particles affected cellular functions by releasing nucleic acids, which produced tumor-like structures in fungal cells.

A battery of methods including traditional microbial plating, electron microscopy and spectroscopy measured antimicrobial activities and mode of action of zinc oxide nanoparticles.

Results showed that even low concentrations of zinc oxide nanoparticles significantly inhibit the growth of both bacteria and fungi, Yang said.

Commercially produced zinc oxide nanoparticles are relatively inexpensive and readily available, he said.

The next step is to apply the zinc oxide nanoparticles to fruits such as apples, oranges and strawberries, he said. Application might take place through spraying or the use of edible films.

“Our research is to study the application of this technology to food science and also its safe, responsible deployment,” Lin said.

A report on the study of zinc oxide nanoparticles' effect on E. coli was published in the Journal of Applied Microbiology.


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