Influence of Solvent Polarity on Crocin Content and Surface Properties of Saffron (Crocus sativus L.) Extracts

Abstract

The saffron composition is being widely studied for authenticity and traceability, but very few works have been carried out to investigate the relationship between the chemical and physico-chemical properties of saffron solutes and their technological functionality in colloidal systems. This study aims at evaluating the surface properties of saffron extracts obtained using solvents of different polarities to achieve extracts with different compositions in terms of the pattern and content of polar and medium polarity crocins. The air-water surface was evaluated alone and in the presence of Tween 20 at different surfactant-extract ratios. Saffron extracts were able to decrease the surface tension of the aqueous phase, indicating the presence of surface-active compounds. In the mixed saffron extract-Tween 20 systems, competitive adsorption at the air-water interface occurred when the surfactant was present at a low concentration, while at concentrations higher than the CMC, Tween 20 hindered the adsorption of the extract surface-active compounds. The results highlight the interesting technological functionality of saffron extracts for applications in colloidal systems. To better exploit their use in the design and development of formulated foods, nutraceutics and pharma products, further studies are needed to unravel the relationship between the composition of saffron extracts and corresponding surface activity.

Keywords: air–water surface tension; crocins; extract polarity; saffron; technological functionality.

Figure 1

Adsorption kinetics of the saffron (a) WE and (b) MPE of the ABR1 sample at increasing concentrations.

Figure 2

Air–water surface tension of saffron extracts (COMM, ABR1, and ABR2) extracted with H₂O (a) and MeOH/MeCN (b) at increasing concentrations.

Figure 3

Air–water surface tension of the crocin standard mix at increasing concentrations.

Figure 4

Adsorption kinetics of the mixed system of Tween 20 at [4.91 mg/L] and the WE of the ABR1 sample at increasing concentrations [3.8, 38, and 380 mg/L]. MS = mixed system; Tw20 = Tween 20.

Figure 5

Surface tension of the mixed system containing a fixed amount of Tween 20 [1.23 × 10⁻⁴; 4.91 mg/L] and increasing concentrations of the crocin standard mix (3.8–380 mg·L⁻¹). The bars to the left of the figure represent the control system containing only Tween 20.

Figure 6

Example of a chromatogram of crocin isomers detected by HPLC-DAD.