Acorns of the two main Quercus species (Q. rotundifolia and Q. suber) of the Portuguese Montado are the main food of the black Iberian pig, which are used to produce the high value Iberian ham. Portuguese and Italian researchers analysed the isotopic composition of the acorns, and found there were no differences in nitrogen or carbon (δ15N and δ13C) isotope ratios between the two species. However, combining the samples and testing for association with the Aridity Index (aridity gradient of the region), it was found that more arid sites lead to a 15N enrichment. Examining the morphology of the acorns with Aridity index, it was found that there was a correlation of higher weight and length only in Q. suber acorns with more arid sites. These results permitted mapping of the isotopic ratios (isoscapes), which could provide a tool to enable the provenance of Iberian pigs/ham to be verified.
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