Near-infrared spectroscopy in saffron quality control: determination of chemical composition and geographical origin

Near-infrared reflectance spectroscopy has been applied for the first time to saffron spice to determine the chemical composition and geographical origin of 111 samples from the there main producers' countries: Iran, Greece, and Spain. The validation procedures with the results obtained by UV-vis and HPLC-DAD measurements demonstrated that this technique is appropriate to determine the following parameters: moisture and volatile content, coloring strength, (250 nm), and (330 nm), established on the ISO 3632 Technical Specification Normative and used to certify saffron quality in the international market. Also, it can be used to estimate the content of the five main crocetin glycosides, the compounds responsible for saffron color, the best correlations being for trans-crocetin di-(beta-D-gentibiosyl) ester (R2= 0.93), trans-crocetin (beta-D-glucosyl)-(beta-D-gentibiosyl) (R2= 0.94), and picrocrocin (R2= 0.92), the compound accepted as responsible for saffron bitterness. Finally, a discriminant analysis among the three geographical origins reveals that Iranian samples are the most different, whereas Greek and Spanish samples are more similar. All of these results reveal that NIRS spectroscopy has an enormous potential for its application to saffron quality control as the results are obtained in 2 min and without any sample manipulation.