Geographic Variation in Trace Element Profiles of Shrimp and Viability of Elemental Profiling as a Traceability Tool

Abstract

The increased concern about the environmental consequences of shrimp culture in importing markets has led to a greater emphasis on sustainability of the products. Traceability is an important component of making claims about product sustainability, and therefore traceability tools are being explored in seafood supply chains. One tool that has been identified is elemental profiling, which is the process of identifying pre-determined groups with classification models based on element concentrations in tissues. Here, we explored the potential for elemental profiling in shrimp from aquaculture ponds. Shrimp from five production countries were collected from shrimp farms and successfully classified based on element profiles with an overall accuracy of 91%. This provides evidence that unique within country profiles exist for shrimp from aquaculture ponds. Shrimp from retail stores were collected in the USA and Europe with the purpose of identifying country of origin identified on the labels. Shrimp labeled as originating in Ecuador, India, Indonesia, Thailand, and Vietnam were collected and classified to labeled country of origin with moderate success (71% overall accuracy). A second classification procedure with the samples from farms within the same countries was attempted where the samples from retail stores were used as a testing dataset, but this was much less accurate (40%). This suggests that the samples from retail stores are incompatible with samples from farms, and a possible confounding factor is the exposure to salts and other chemicals at the processing plants. To investigate this possible phenomenon, samples were obtained from farms in Thailand and Ecuador that were paired with samples from farms pre and post processing. The element profiles of samples in Ecuador showed no practical differences, while the samples in Thailand were markedly different because of the salt bath during processing. Finally, sources of variation that may affect elemental profiles were investigated, namely laboratory variation and shrimp tissue. In a ring-test of three laboratories, 2 of 5 elements were significantly different, and a homogenized sample replicated 20 times in one laboratory had high coefficients of variance for elements that were above detection limits. Two farms in Alabama were used to analyze variance in tissue samples from shrimp. A multivariate comparison showed an interaction between tissue type and location, suggesting that mineral compartmentalization is geographically dependent. Altogether these results show 1): elemental profiling is a viable tool in shrimp, 2) retail products likely need to be profiled with other retail products or post-processed shrimp, 3) processing interferes with the elemental profile of shrimp products, and 4) shrimp tissues are variable across geographies and laboratory analysis can play a role in increasing variation in element profiles. This work will improve future efforts in elemental profiling and shows that it is a viable tool for traceability in seafood products, specifically shrimp.