Characterising New Zealand butter using bulk and molecular multi-isotope analyses

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2018-026-pdf
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Rogers, K.M.; Phillips, A.M.; Immers, A.G.; Cooper, J.; Sim, M.; Fitzgerald, J. 2018 Characterising New Zealand butter using bulk and molecular multi-isotope analyses. Lower Hutt, N.Z.: GNS Science. GNS Science report 2018/26. 38 p.; doi: 10.21420/G2TH2G

Abstract: Food fraud is now a serious problem worldwide and the various methods of disguising the origin and authenticity of lower quality products for economic gain is increasing. For some time, stable isotopes have been employed as a tool of choice to determine origin and farming methods of agricultural and animal products. The Ministry for Primary industries (MPI) commissioned GNS Science to investigate a selection of New Zealand and overseas sourced butter to understand key differences in their chemical and isotopic fingerprints. Twenty-five butter samples were submitted to GNS Science in July 2018 with 20 samples sourced from New Zealand and 3 samples sourced from Australia and United States of America. Stable isotopes of the bulk butter and butter protein were studied using carbon, nitrogen, hydrogen, oxygen and sulphur isotopes to determine their key characteristics according to geographical origin. Bulk carbon and nitrogen isotopes were used to differentiate New Zealand products due different farming practices. New Zealand cows are free-ranging and pasture fed compared to overseas animals which are frequently limited in their feeding habits to grain supplied to them in stables or concrete shelter pads. Hydrogen and oxygen isotopes were also useful to determine geographical origin through the isotopic changes found in precipitation across latitudinal gradients. Sulphur isotopes were also found to be a unique identifier as the New Zealand landscape is affected by marine sulphates from ocean spray or from sulphur found in top dressings and fertilisers used on pasture. The investigation found stable isotopes are a promising tool to both differentiate butter from New Zealand and other countries, and also with further research, offers the potential to discriminate New Zealand butter based on either a regional basis or from a preparative basis. (auth)