Thermal stability improvement of duble colorant C-phycocyanin from Spirulina platensis for food industry applications.

C-Phycocyanin (C-PC) is a blue pigment in cyanobacteria, rhodophytes and cryptophytes with potential use as a value-added food colorant. Its stability was studied by examining the thermal degradation reactions in a range of temperature (25-80 C) before and after the addition of selected edible preservatives. The natural protein crosslinker methylglyoxal does not stabilize significantly C-PC whereas addition of honey or high concentration of sugars greatly diminish the blue color degradation occurring when C-PC is exposed to high temperature. Data show that the sugar preservative effect on the C-PC blue color is related to the final concentration of sugar added rather than the type of sugar. For this reason the best preservative was found to be fructose, which is the most soluble sugar among those tested, at saturation concentration. Exploratory sterilization studies have been carried out with six blue/green fructose syrups made by mixing C-PC with the natural yellow pigment Carthamus tinctorius. Both after a "low temperature" and a "high temperature" sterilization procedure the syrups remain clear and maintain their bright color with only partial blue color degradation. After the sterilization process, the syrups were monitored for two months, in such observation period the loss of blue color is minimal.