Classification of organic and conventional sweet peppers and lettuce using a combination of isotopic and bio-markers with multivariate analysis

• Verification of organic pepper and lettuce authenticity.
• Treatments included different origins and types of N fertilisers and biosolarisation.
• Multivariate analysis (δ15N values, key-metabolites and mineral content).
• Canonical discriminant analysis to predict the mode of cultivation.
• The use of biomarkers in lettuce allowed 90.4% of cases to be correctly classified.

In order to verify the authenticity of organic products, multivariate data (δ15N values, key-metabolites and mineral content) were used to classify organic and conventional peppers and lettuce by means of canonical discriminant analysis. Different origins and types of fertilisers were considered. This is the first paper to look into the influence of biosolarisation, a soil disinfection technique widely used in organic cultivation, on the differentiation between organic and conventional crops. The use of pre-harvest parameters (plant and soil δ15N and plant weight) allowed 78.8% and 65.4% of pepper and lettuce samples, respectively, to be correctly classified. In pepper, this percentage was reduced (69.2%) when only post-harvest sampling parameters were used to build the classification model. In lettuce, the use of biomarkers significantly improved the model, allowing 90.4% of cases to be correctly classified. This methodology showed a high potential for use as an authenticity control tool for organic cultivation.