Effects of Storage Conditions on the Stability of C-Phycocyanin in the Spirulina platensis Extract associated with Ultrasonic Process

The results of this work were to describe the long-term stability of c-Phycocyanin (C-PC) in the Spirulina platenssis extract obtained from an ultrasound process, compared with the change in C-PC content in phosphate buffer solution under the same conditions. At a low temperature of 4 degrees C and in the absence of light, the CPC amount in the extract (UE) and buffer solution (SS) decreased by less than 10% after one month of storage whereas approximately 40% of CPC in both UE and SS was reduced at 40 degrees C C in the absence of light compared with the initial contents of C-PC. It was also determined that the exposure to light significantly accelerated the decrease in C-PC contents which decreased to 60% of the initial content at 40 degrees C and even decreased to ca. 15% at 4 degrees C. In general, storage temperature affected the stability of C-PC more than light. Interestingly, the C-PC in the extract was apparently more stable than in phosphate buffer at the same concentrations possibly due to the protection of light destruction by various components in the extract. The initial storage temperature was also observed to be important for a long-term storage since most C-PC in the solutions decreased within the first two weeks of storage. Long-term storage under harsh conditions also affected the structural changes of C-PC in the solutions by selectively breaking down a subunit out of C-PC, not beta subunit, in absorption spectra analysis. These changes were also attributed to decrease in antioxidant activities of solutions, since CPC was known to have strong antioxidant activities. Therefore, this study can provide useful information for maintaining an unstable C-PC in the Spirulina extract which is highly important in many industrial fields.