Colour modulation of blue anthocyanin-derivatives. Lignosulfonates as a tool to improve the water solubility of natural blue dyes

• Type: Article in International Scientific Journal
• Date: 2018

Authors

Araujo, P (Author) Other; Basilio, N (Author) Other; Azevedo, J (Author) Other; Fernandes, A (Author) Other; Nuno Mateus (Author) FCUP; Pina, F (Author) Other; Victor de Freitas (Author) FCUP; Joana Oliveira (Author) FCUP

Journal

Title: Dyes and Pigments

Vol. 153

Pages: 150-159

ISSN: 0143-7208

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 8 Citations

Scopus - 8 Citations

Other information

Authenticus ID: P-00N-MV7

DOI: 10.1016/j.dyepig.2018.02.019

Abstract (EN): The impact of a lignosulfonate (calcium) (L) on the chromatic features of two anthocyanin-derived bluish dyes (portisin, P and pyranoanthocyanin dimer, PD) was evaluated in aqueous solutions using UV-Visible spectroscopy. It was demonstrated that the interaction between each dye and this macromolecule at pH 1 occurs by two mechanisms, association and copigmentation that are dependent on L concentration. For instance, at low concentrations of L (up to 0.27 mu M) it is observed the association of dyes promoted by their complexation with lignin (different molecules of dye are bound to the same binding sites of L). At higher concentrations of L (25 mu M), the aggregation of dyes decreases and each molecule is bound to a different site of L resulting in the formation of a charge-transfer complex (copigmentation). Moreover, the titration of both dyes (P and PD) in the presence of L (19 mu M) showed a strong stabilization of their pyranoflavylium cation forms revealed by the considerably higher pK(a1) (6.6 +/- 0.1 and 6.2 +/- 0.1 for P and PD, respectively) in the presence of this macromolecule when compared to the values obtained in the absence (pK(a1) = 4.61 +/- 0.03 and 4.93 +/- 0.04). In addition, the water solubility of the dyes in the absence and presence of L was also evaluated by turbidimetry and the results showed that the water soluble lignosulfonate improved the solubility of the dyes over time.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10