Determination of free amino acids and ammonium ion in saffron (Crocus sativus L.) from different geographical origins

Amino acids are important in human nutrition and also influence the sensory traits of products. Up to now, no report has been available on the free amino acid content of saffron spice. This study developed a rapid method for the extraction of free amino acids and ammonium ion from saffron, thus permitting the differentiation of saffron samples by origin. The first step tested the extraction time (15, 30, 60, 120 and 240 min) and extractive solvent (water, 0.1 N HCl, 0.5 N HCl and 1 N HCl). The best results for the free amino acids and ammonium ion extraction were obtained using 0.1 N HCl during 60 min. Subsequently, these compounds were derivatised using diethyl ethoxymethylenemalonate (DEEMM) and analysed by HPLC. Using this method, 20 saffron samples from different countries (Spain, Italy, Greece and Iran) were analysed. Alanine, proline and aspartic acid were the major amino acids in all the samples. Alanine presented the maximum value in Iranian samples with 0.17 ± 0.02 mg/100 mg of saffron. The highest concentration of proline (0.087 ± 0.01 mg/100 mg) appeared in Greek samples and the maximum value of aspartic acid was 0.04 ± 0.01 mg/100 mg in Spanish samples. Greek and Iranian saffron presented the highest total free amino acid content, 0.50 ± 0.08 mg/100 mg and 0.55 ± 0.07 mg/100 mg, respectively. Furthermore, the free amino acid profile enabled us to differentiate the Iranian samples from the European samples (p < 0.05).