Improving fruit juice origin assignment by combined carbon and nitrogen isotope ratio determination in pulps

The combination of the relative abundances of carbon and nitrogen isotopes (delta(13)C- and delta(15)N- values) in fruit juice pulps led to characteristic clusters, on the basis of which regional origin assignments of citrus juices were possible, which would not have been attained on the basis of only one of these parameters. Thus, while the delta(13)C-values of juice pulps from Italy partially overlapped with those from Brazil, the delta(15)N- values permitted an origin assignment. First attempts to extend this multi-isotope analysis to a multi-compound N-15 analysis, by correlating the delta(15)N-values of fruit juice pulps to those of free amino acids, were promising. The results obtained were in line with general observation on N-15 abundances and biochemical correlations of secondary plant products.