A researcher has developed a technique to identify the difference between eggs from caged hens and those from free-range and organically raised hens.
It is believed to be the first time that eggs from different farming systems have been distinguished by using isotope analysis.
While it is not something thesupermarket shopper could use every day, it has potential within the egg industry to avoid mislabelling.
Karyne Rogers, of Geological and Nuclear Science's National Isotope Centre in Lower Hutt, compared different brands of off-the-shelf eggs from cage, barn, free range and organic farming regimes.
Using isotope analysis, she found almost all the eggs could be differentiated by relating the carbon and nitrogen found in the egg to the hen's diet.
This was possible as diet directly reflected the type of farming environment where the hens were raised, Dr 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," she said.
The findings, recently published in the Journal of Agricultural and Food Chemistry, showed isotope analysis was a potentially useful technique for identifying eggs from different farming regimes.
The research was performed on egg yolk, albumen and egg membrane to see which egg components gave the best information about the hen's diet.
Dr Rogers said the technique held considerable promise for the egg industry as an effective verification tool to guard against mislabelling.
"The next step is to seek industry funding to work directly with egg producers to further refine the technique so it can be fully tested and applied in the industry."
