Elucidating the Origin of Milk Products on the Chinese Market Using Multi Element Stable Isotope Technique
Abstract
Eyram Norgbey, Jingyu Huang, Philip N Nkrumah, Gloria Appiah Sefah, Rainizafy Michelle
Preference for foreign milk products is the cause of the economically motivated adulteration of milk products on the Chinese market. The present study was done to ascertain the feasibility of utilizing δ2 H, δ18O and δ15N stable isotope techniques in elucidating the geographical origin of milk products on the Chinese market. 42 milk samples from the United States of America, Canada, Southern China, Northern China, Australia and New Zealand were analyzed. An isotope ratio mass spectrometer with a combination of a high-temperature conversion elemental analyzer, Thermo-Fisher was used. Statistical analysis was performed using one-way ANOVA. The study revealed that both δ2 H and δ18O had a wide range of mean values: 13.86 to 22.25% and -82.86 to -28.5%, respectively. There was a significant difference in the δ2 H (n=7; F=20880, P=7.876E-43) and δ18O (n=7; F=1399.0; P=9.215E-29) composition of the milk samples from the different regions. It was observed that δ2 H and δ18O composition is helpful in elucidating milk products from different regions on the Chinese market (P<0.05). The range of the mean δ15N values of the milk samples was very close, 3.06 to 5.61%, indicating a possible limitation in employing δ15N isotopic technique. The nitrogen stable isotope could not provide a clear distinction for the milk products because δ15N of an animal reflects that of the diet. Hence in cases of similar diet, it may not be possible to provide a distinction between the animals using this technique.