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In this paper (open access), researchers used analysis of the stable-isotope nitrogen ratio (SIRA) within specific compounds, as a refinement of the total nitrogen stable-isotope measurement technique, to differentiate products made from wheat grown in organic fertiliser compared to conventional fertiliser.  They used paired samples to demonstrate the concept (control samples, where the only difference between each pair is the wheat fertiliser regime) and have not tried the technique on market samples.  They found that δ15N analysis of specific compounds (particularly leucine and proline) gave better discrimination in processed products than total δ15N analysis, although the absolute isotope ratios were significantly impacted by the processing.

The authors added a further weight of evidence by analysing the paired samples for mycotoxins (organic wheat in general has more mycotoxin contamination than conventional, and some mycotoxins are stable to processing) and pesticide residues analysis.

For FAN’s explainer of SIRA principles, see here.

Photo by Vyshnavi Bisani on Unsplash