A comparison of eggshell mineral composition between cage and free-range eggs via inductively coupled plasma-optical emission spectrometry

Abstract

Context In Australia and many other countries, free-range eggs can be sold at significantly higher prices than cage eggs. Mislabelling cage eggs as free-range eggs and vice versa has been documented, and has a significant impact on consumer trust and egg consumption. The development of methods to identify eggs produced from different production systems is necessary to satisfy consumer demand. Aims The objective of this study was to determine whether eggshell mineral composition could be used as a way to differentiate eggs originating from each production system. Our hypothesis was that birds with access to soil would have higher levels of trace minerals in shells. Methods Eggs were randomly collected from six commercial caged and six commercial free-range flocks in Australia. Twelve eggshell samples from each flock were analysed for mineral composition (Ca, P, Mg, Na, Al, B, Cu, Mn, Fe, K, S and Zn) by using inductively coupled plasma-optical emission spectrometry. Key results The results showed that free-range eggshells contained significantly higher contents of macro-minerals (P, Mg and Na) but lower contents of micro-minerals (Cu, Fe, K, S and Mn) than the cage eggshells (P < 0.05). For all minerals measured, a high variability was noted within and between production systems. Conclusions Analysis of eggshell mineral composition may not be effective for determining the origin of eggs. Implications Systematic studies of the bird’s environment, including analysis of mineral composition in diets, pastures, soil and drinking water are required for comprehensive evaluation of the influences of production systems of laying hens on mineral composition of eggs and eggshells.

Discrimination of Free-Range and Caged Eggs by Chemometrics Analysis of the Elemental Profiles of Eggshell

“…The elemental contents of Ca, Mg, Na, and K were the highest in free-range and caged eggs. Among them, free-range eggs have higher content of Ca, Mg, and Se compared to caged eggs, while caged eggs have higher content of Na, K, Al, Sr, Fe, and Mn, which is consistent with previous studies [ 38 ]. It is noteworthy that caged eggs have higher content of heavy metals such as Pb, Cd, Cr, and Cu, and there is no detected Cd element in the free-range eggs.…”

“…In addition, mineral element-based methods combined with chemometrics have been successfully applied to identify free-range and caged eggs. In Dao's study, significantly higher levels of the mineral elements P, Mg, and Na and lower levels of the trace elements Cu, Fe, K, S, and Mn were found in Australian free-range eggs, and a good classification of free-range and caged eggs from Australia and Syria was achieved [ 38 ]. The above studies show that mineral element-based methods combined with chemometrics can achieve accurate identification of free-range eggs and caged eggs in China.…”