High Molecular Weight λ-Carrageenan Improves the Color Stability of Phycocyanin by Associative Interactions
Stephan Buecker, Lutz Großmann, Myriam Loeffler, Elena Leeb, Jochen Weiß
Abstract
Phycocyanin is a protein-chromophore structure present in Arthrospira platensis commonly used as a blue-colorant in food. Color losses of phycocyanin can be reduced by electrostatic complexation with λ-carrageenan. The aim of this study was to investigate the effect of molecular weight ( M W ) of λ-carrageenan on the color stabilization of electrostatic complexes formed with phycocyanin and λ-carrageenan. Samples were heated to 70 or 90°C at pH 3.0 and stored at 25°C for 14 days. The M W of λ-carrageenan was reduced by ultrasound treatments for 15, 30, 60, and 90 min. Prolonged ultrasonication had a pronounced effect on the M w, which decreased from 2,341 to 228 kDa (0–90 min). Complexes prepared with low M W λ-carrageenan showed greater color changes compared to complexes prepared with high M W λ-carrageenan. The M W had no visible effect on color stability on day 0, but green/yellow shifts were observed during storage and after heating to 70°C. Medium M W showed less color stabilization effects compared to low M W when heated to 70°C. Moreover, for solutions prepared with ultrasonicated λ-carrageenan, significant hue shifts toward green/yellow, and precipitation were observed after a heat treatment at 90°C. In addition, the sizes of the complexes were significantly reduced (646–102 nm) by using ultrasonicated λ-carrageenan, except for the lowest M W λ-carrageenan when heated to 90°C. Overall, these findings demonstrated that decreasing the M W of λC had adverse effects on the color stability of PC:λC complexes heated to 70 and 90°C.