Thermal degradation kinetics of the phycocyanin from Spirulina platensis

The cyanobacterium Spirulina platensis is a source of pigments, such as phycocyanin, which is used in the food, cosmetic and pharmaceutical industries. The thermal degradation kinetics of the liquid extract at pH values of 5, 6 and 7 was studied, evaluating its stability between 50 and 65 1C. The kinetic model was assumed and validated as being of the first order. Between 50 and 55 IC the extract was more stable at pH 6 and between 57 and 65 IC at pH 5, but was shown to be increasingly unstable at pH 7 as the temperature of the treatment increased. The addition of sorbitol between 10 and 50% (w/w) in the treatment at 62'C for 30 min increased the half-life values of the phycocyanin extract, proving that its cle-colorization was related to degradation of the protein chain. (D 2008 Elsevier B.V. All rights reserved.