Synergic effect of water-soluble components on the coloring strength of saffron spice

The purpose of this paper was to study the synergic effect of water-soluble components of saffron, such as picrocrocin and kaempferol-3-O-glycoside, on its coloring strength ( E 1   cm 1 % 440   nm ). The paper tries to clarify why a pool of isolated compounds responsible for coloring strength (crocetin esters, approx 94% purity) has the same coloring capacity as pure saffron (approx 20–22% of crocetin ester content). Picrocrocin and kaempferol-3-O-glycoside were added to an aqueous solution of crocetin esters at different molar ratios, temperatures and pH conditions, to promote the synergic effect between saffron components. When aqueous solutions of picrocrocin and crocetin esters were heated at 30 °C, coloring strength values were higher than aqueous solutions of crocetin esters subjected to the same treatment. Noticeable increases of E 1   cm 1 % 440 values were found when picrocrocin was added to crocetin esters at molar ratios equal to or higher than 1:1. These increases were even higher when kaempferol-3-O-glycoside was added up to a 2:1 and 5:1 molar ratio.