Fingerprints for recognition of French monovarietal walnut oils making up the Périgord Protected Designation of Origin (PDO)

Abstract

This study is the first to be carried out for varietal recognition of cold-pressed oils from Périgord walnuts (France). Produced from Corne, Franquette, Grandjean and Marbot varieties, the Perigord oil is currently the sole walnut oil to benefit of a Protected Designation of Origin (PDO, obtained in 2020). The Fernor variety should potentially be added to the PDO. The compositions of fatty acids (FA), triacylglycerols (TAG) and tocopherols of the five walnut varieties were determined from 176 samples over three harvest years. Data of FA and TAG were used to generate graphical representations named “morphotypes” corresponding to each variety. These morphotypes provided rapid visual identification of varieties and their specific markers. Partial Least Square Discriminant Analysis (PLS1-DA) was used to predict the four Perigord walnut varieties with a control chart approach to estimate the degree of reliability of the prediction. Models from FA contents provided the best results with a percentage of samples recognized as belonging to the predicted variety equal to 93%, 81%, 75% and 86% for the varieties Corne, Franquette, Grandjean and Marbot respectively. These approaches offer the advantage to be evolutive and can be supplemented by annually collected data.