Scientist believes test could identify free-range eggs

Spotting the difference between free-range eggs and those produced by caged hens may soon be an exact science.

New Zealand researcher Karyne Rogers has developed a technique to identify the difference. Using isotope analysis, she found almost all the off-the-shelf eggs tested could be differentiated by relating the egg's carbon and nitrogen levels to the hen's diet.

Rogers said the technique held "considerable" promise as a tool to prevent mislabelling.

"New Zealand exports more than two million free-range eggs a year and this test could provide added consumer confidence, which would give New Zealand an advantage in export markets," she said. The research was on egg yolk, albumen and egg membrane to find which components gave the best information about a hen's diet.

Diet directly reflected a hen's farming environment, Rogers said.

"Free-range and organically farmed hens normally have access to a wider range of food sources than caged hens, such as insects, vegetation or organic feeds, and this changes the isotope fingerprint of their eggs."

The findings, published in the Journal of Agricultural and Food Chemistry, will be presented at the New Zealand Institute of Food Science and Technology conference in Christchurch next week. Securing funding for the technique to be tested and applied in the industry was the next step, Rogers said.

Her previous research showed it was possible to differentiate between organic and conventionally grown vegetables using isotope analysis.

Suse Benzie, of Kirwee's Benzie Free Range, said she had a "degree of scepticism" after research had failed to find a conclusive test. She had not seen the latest findings. "If we could find something definitive that would check to see whether an egg was free-range or not, I would be very happy."

- © Fairfax NZ News