Tracing the Geographical Origin of Onions by Strontium Isotope Ratio and Strontium Content

Abstract

The strontium (Sr) isotope ratio (⁸⁷Sr/⁸⁶Sr) and Sr content were used to trace the geographical origin of onions from Japan and other countries, including China, the United States of America, New Zealand, Australia, and Thailand. The mean ⁸⁷Sr/⁸⁶Sr ratio and Sr content (dry weight basis) for onions from Japan were 0.70751 and 4.6 mg kg⁻¹, respectively, and the values for onions from the other countries were 0.71199 and 12.4 mg kg⁻¹, respectively. Linear discriminant analysis was performed to classify onions produced in Japan from those produced in the other countries based on the Sr data. The discriminant equation derived from linear discriminant analysis was evaluated by 10-fold cross validation. As a result, the origins of 92% of onions were correctly classified between Japan and the other countries.