Stability of phycocyanin extracted from Spirulina sp.: Influence of temperature,pH and preservatives

Temperature and pH play an important role in the stability of phycocyanin, a natural blue colorant. Systematic investigations showed the maximum stability of phycocyanin was in the pH range 5.5–6.0. Incubation at temperatures between 47 and 64 °C caused the concentration (C_R) and half-life of phycocyanin in solution to decrease rapidly. The C_R value remained at approximately 50% after incubating for 30 min at 59 °C. After heating at 60 °C for 15 min, the C_R value of phycocyanin at pH 7.0 was maintained at around 62–70% when 20–40% glucose or sucrose was added, and the half-life increased from 19 min to 30–44 min. 2.5% sodium chloride was found to be an effective preservative for phycocyanin at pH 7.0 as a C_R value of 76% was maintained and the half-life of 67 min was increased.