Study of temperature and food-grade preservatives affecting the in vitro stability of phycocyanin and phycoerythrin extracted from two Nostoc strains

Abstract

Cyanobacteria have many bioactive compounds. In the present study, we investigated the degree of purification and free radical scavenging ability of phycocyanin (PC) and phycoerythrin (PE), and compare their stability against selected preservatives at different temperatures with the aim of achieving the best and most stable preservative in increasing shelf life of PC and PE. After collecting and culturing Nostoc sp. strains FSN and ASN in BG-110 medium, the pigments phycocyanin and phycoerythrin were extracted and purified with 56% ammonium sulfate followed by dialysis. The antioxidant activity of pigments was evaluated by DPPH and ABTS assays. Their stability was compared with food-grade preservatives citric acid, sodium chloride, sucrose, and calcium chloride at two temperatures of 5 °C and 35 °C over time period from 3 to 30 days of cultivation. The results showed that the concentration and purity of the pigments increased after the dialysis, the pigments had antioxidant properties and were more stable at 5 °C. In addition, among different preservatives, citric acid caused more stability over time.