Parabens as Agents for Improving Crocetin Esters’ Shelf-Life in Aqueous Saffron Extracts

The effect of parabens on the shelf-life of crocetin esters and picrocrocin in aqueous saffron solutions was studied. Degradation of saffron crocetin esters fits a first-order kinetics model, and the results indicated that the crocetin (β-d-glucosyl)-(β-d-gentiobiosyl) esters were more stable than the crocetin di-(β-d-gentiobiosyl) esters regardless of whether trans and cis isomers were considered. Under all tested conditions both parabens gave good results, especially propyl paraben that showed a greater influence on the degradation rate constant, except for cis-crocetin di-(β-d-gentiobiosyl) ester and cis-crocetin (β-d-glucosyl)-(β-d-gentiobiosyl) ester. In presence of propyl paraben (200 mg/L), the half-life periods of trans-crocetin di-(β-d-gentiobiosyl) ester improved considerably, up to four-fold. Special attention has been paid to the effect of propyl paraben on 46 saffrons with different crocetin ester contents. No differences were observed in terms of picrocrocin. By analysis of variance, it is noteworthy that there were differences between the mean content of crocetin esters for all analysed saffron, except for trans-crocetin (β-d-glucosyl)-(β-d-gentiobiosyl) ester.