Coffee, tea leaves, pineapple and PIXE: what do they have in common?

Information on food provenance is essential for ensuring product safety, authenticity, and traceability. Knowledge of a food product's origin is often associated with quality, unique characteristics, and higher economic value, while also helping to prevent fraudulent production and commercialization practices. Scientific data such as isotopic composition, elemental profiles, and specific chemical compounds can serve as geochemical markers for determining the provenance and authenticity of food products [1]. In this context, the aim of this work is to apply Particle-Induced X-ray Emission (PIXE) to determine the elemental composition of Brazilian food products and beverages, searching for elemental signatures through statistical analysis. The main motivations are the use of a single multielemental analytical technique for different types of organic materials and the adoption of simple and environmentally friendly sample preparation procedures [2]. Brazilian coffee, pineapple and tea leaves (Ilex paraguariensis, popularly known as yerba mate) produced and/or commercialized in Rio Grande do Sul state were analyzed using the PIXE beamline at the Ion Implantation Laboratory in Porto Alegre, Brazil. These products were selected because Brazil is one of the world's largest producers and exporters of them. Moreover, these products exhibit distinctive characteristics linked to their geographical origin and are strongly associated with specific cultivation practices and regional cultural tradition. Despite their economic relevance, there is still limited scientific data available regarding the determination of provenance and authenticity of them.

While for some products the whole production process is well known, as in the case of coffee beans or pineapple from specific farms studied here, in other many cases the final product results from a mix of raw material cultivated in different farms which are packed together, as may happen with commercial yerba mate produced in Rio Grande do Sul. In known farms, it is possible to study also their respective soils, adding valuable data to understand the product elemental composition differences. However, for products like yerba mate, the geographical differentiation accessed as a regional characteristic.

PIXE proved to be an important tool for the elemental composition analysis and the geographical differentiation of the above-mentioned products. Coffee beans from different farms within the same geographically delimited region, defined according to soil and climatic characteristics, showed different elemental concentrations, particularly for S and K. The respective farm’s soils presented differences in the concentration of Si, Mn, Ti and/or P. Additiolly, yerba mate from Rio Grande do Sul, Uruguay and Argentina were studied and it was observed significant differences among the regions for all elements except S. Multivariate statistical analyses indicated that elemental variability can be used to characterize the provenance of Ilex paraguariensis. In particular, elements such as Mg, Cu, Sr, Mn, and Ni showed correlated behavior, suggesting that they could be useful indicators for identifying the geographical origin of this product. Finally, the distinctively sweet pineapple from Terra de Areia in Rio Grande do Sul is being studied to identify elemental compounds that can serve as geochemical markers.

References.

[1] Authentication and traceability study of hazelnuts from Piedmont, Italy. M. Oddone, M. Aceto, M. Baldizzone, D. Musso and D. Osella. J. Agric. Food Chem. 57(9) (2009) pp3404-3408.

[2] Elemental characterisation of Cabernet Sauvignon wines using Particle-Induced X-ray Emission (PIXE). C.E.I dos Santos, L.R.M. da Silva, L. Boufleur, R. Debastiani, C.A. Stefenon, L. Amaral, M.L. Yoneama and J.F. Dias. Food Chem. 121 (2010) pp 244-250.