STABLE ISOTOPE ANALYSIS (SIA) BY ICP-MS FOR TRACEABILITY OF COMMERCIAL SHRIMPS

Traceability is finding a link among food stuff and the soil from where the raw material come from while authentication is highlighting the differences among food stuff on geographical, varietal or technological basis. Inductively Coupled Plasma Mass Spectrometer (ICP-MS) is more suitable for classification of food stuff considering the multi element profiling and isotope ratio analysis of heavy metals. Shrimps account for about 15% of the total value of internationally traded fishery products and are prone for mislabeling. In this study, stable isotope analysis (SIA) was carried out for few species of shrimps viz. Penaeus semisulcatus, Penaeus indicus,  Metapenaeus dobsoni and Penaeus vannamei  using ICP- MS. The stable isotopic ratio of ⁸⁷Sr/⁸⁶Sr, Sr/Ca, 206Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁷Pb and sum of Pb isotopes were examined.  The ⁸⁷Sr/⁸⁶Sr ratios of P indicus, P. semisulcatus, M. affinis and P. vannamei were 2.615, 1.712, 1.483 and 1.655 and the Sr/Ca ratios were 0.202, 0.164, 0.150 and 0.146 respectively. Significant differences in ⁸⁷Sr/⁸⁶Sr (p=0.016) and ⁸⁷Sr/Ca ratio (p=0.021) was observed among different varieties of shrimp. The ²⁰⁶Pb/²⁰⁷Pb ratios of P indicus, P. semisulcatus, M. affinis and P. vannamei were 1.094, 1.089, 1.098 and 1.085 , ²⁰⁸Pb/²⁰⁷Pb were 1.225, 1.337, 1.231 and 1.215 and the sum of Pb isotopes were 3.486, 3.597, 3.265 and 3.514, respectively. But, the ²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁷Pb isotopic ratios and sum of Pb isotopes did not show any significant difference (p>0.05). The stable Sr/ Ca and ⁸⁷Sr/⁸⁶Sr isotopic ratio shall therefore serve as best chemical marker to authenticate different shrimp varieties more specifically to differentiate the farmed and wild ones. This method shall be a better alternative for  protein or DNA based methods for authentication.