Evaluation of the effect of temperature, time and pH on stability of phycocyanin extracted from Spirulina platensis

Phycocyanin is a blue pigment of Spirulina algae that has antioxidant, anticancer and anti-inflammatory properties. In this study, primary culture of Spirulina was performed in the modified Zarrouk medium. Phycocyanin was extracted enzymatically using lysozyme and was purified by the use of ammonium sulfate 40% solution. The stability of phycocyanin was evaluated by the split factorial experiment in a completely randomized design based on three factors including temperature (-18, 4 and 10°C), pH (4.5, 5.5 and 7) and time (15, 30 and 45 days). The concentration and purity of phycocyanin in the crude extract were 1.815 mg/ml and 0.825, respectively whereas the concentration and purity of phycocyanin in the purified extract were 3.751 mg/ml and 1.135, respectively. The results showed that the stability of phycocyanin was relatively decreased by increasing the storage time at various temperatures. However, the highest stability of phycocyanin was observed at -18°C followed by 4°C with the same trend in the range of pH. By increasing the storage temperature to 10°C, the stability of phycocyanin drastically reduced especially in a pH of 5.5 and the absorbance of light was reached to zero in 30 days. The best conditions for the minimum concentration loss of phycocyanin were in a pH of 4.5 at -18 °C and storage duration of 30 days. According to the results, it is possible to use phycocyanin in the food products that are stored in cold or freezing temperatures such as dairy products and ice cream.