Role of saccharides on thermal stability of phycocyanin in aqueous solutions

The effect of heat and equivalent thermal effect (C-Tref(Z)) on discolouration of Spirulina algae extracts in water, sucrose and trehalose solutions at different concentration was investigated and kinetics of phycocyanin degradation evaluated by spectrophotometric and circular dichroism. At constant temperature, colour loss increased at increasing time and decreased at increasing solute concentration. Circular dichroism confirmed relation between colour loss and protein structure destabilization, and the thermostabilising effect of saccharides with sucrose performing better than trehalose. Apparent constant rate values determined by the Weibullian probabilistic model describe the corresponding phycocyanin degradation kinetics; a linear correlation between the activation energy and a(w) of the solutions has been found. Origin of phycocyanin and system saccharide concentration resulted significant discriminant factors on the discolouration when C-Tref(z) was taken into account. Results may find application in product formulation and processing optimisation, thereby the use of Spirulina extracts as colouring foodstuff could be enhanced.