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Isotope analysis of eggs

Scientists at the National Isotope Centre in Lower Hutt have developed an isotope analysis test that is being used to identify eggs from different farming regimes.

Differences in diet

Dr Karyne Rogers compared different brands of off-the-shelf eggs from caged hens (commonly known as battery-farmed hens), barn hens, free-range hens and organically farmed hens.

Using isotope analysis, Dr Rogers found almost all the eggs could be differentiated by relating the carbon and nitrogen found in the egg to the hen’s diet, which directly reflects the type of farming environment where the hens were raised.

“Free-range and organically farmed hens normally have access to a wider range of food sources than caged hens. These hens eat insects, vegetation and/or organic feeds, and this changes the isotope fingerprint of their eggs,” says Dr Rogers.

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.

Added consumer confidence

Dr Rogers said the technique held considerable promise for the egg industry as an effective verification tool to guard against mislabelling.

“The technique is a good way to scientifically prove that eggs are truly free-range or organic.”

“New Zealand exports more than 2 million free-range eggs a year, and this test could provide added consumer confidence, which would give New Zealand an advantage in export markets.”

The findings were recently published in an international publication, the Journal of Agricultural and Food Chemistry, and in June 2009, Dr Rogers presented these findings at the New Zealand Institute of Food Science and Technology Annual Conference in Christchurch.

Activity idea

Dr Katja Reidel explains what isotopes are in this video from our Icy Ecosystems context.
What are isotopes?


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