Determination of the Geographic Origin of Eel Products by Stable Isotope Ratio Analysis

Abstract

Stable isotope analysis of carbon, nitrogen, and oxygen (¹³C/¹²C, ¹⁵N/¹⁴N and ¹⁸O/¹⁶O) was evaluated as a potential tool for discriminating the geographical origin of eel products. We investigated a total of 244 samples collected from two countries ; 139 samples from Japan and 105 samples from China. We also developed method to minimize N₂ contamination of ¹⁸O/¹⁶O measurements, and confirmed the absence of oxygen-exchange during ultrasonic cleaning of the samples. The isotope ratios of carbon, nitrogen, and oxygen were significantly different between the Japanese and Chinese samples. The difference in the isotope ratio between collection years (i.e., 2010 and 2011) was significant for carbon and nitrogen, but negligible for oxygen. Based on these results, we established a linear discriminant model and tested its predictive accuracy by leave-one-out cross validation. Consequently, 97.8 % of the Japanese samples and 83.8 % of the Chinese samples were correctly identified. We concluded that stable isotope analysis is useful for discriminating the geographic origin of eel products.