Abstract

EFFECTS OF TEMPERATURE AND pH ON THE STABILITY AND ANTIOXIDANT ACTIVITY OF C-PHYCOCYANIN IN THE COMBINATION WITH CENTRAL COMPOSITE DESIGN AND RESPONSE SURFACE METHODOLOGY

Doan Thi Thanh Tra, Nguyen Anh Dung and Nguyen Hoang Khue Tu*

ABSTRACT

C-phycocyanin is a water soluble and natural blue protein pigment with many biological activities. However, C-phycocyanin is degraded easily that is a big problem when using it for developing its product. Temperature and pH levels are the two factors that can easily affect the stability of C-phycocyanin. In this study, C-phycocyanin solution was incubated in different temperatures (13oC, 20oC, 37oC, 54oC, 60oC and 70oC ± 2oC) and different pH levels (3.0, 4.0, 7.0 10.0 and 11.0 ± 0.1). When increasing temperature from 40oC to 95oC, the relative concentration (CR) values changed significantly. At 95oC, the concentration of Phycocyanin remained lowest which was 49.12%. At pH 3, 4, 10, 11, the concentration of C-phycocyanin remained 9.16%, 47.11%, 40.64%, 52.96%, respectively. To study the effects of two factors, the central composite design (CCD) and response surface methodology (RSM) were used to aid for the determination of the optimal condition for C-phycocyanin stability. The results showed that the best condition for C-phycocyanin was 37oC at pH 7 with the highest stability around 94.15%. Moreover, C-phycocyanin showed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity at this condition. The study clarified the condition for C-phycocyanin stability that will be important for C-phycocyanin product development.

Keywords: C-phycocyanin, stability, pH, temperature, response surface methodology, central composite design, DPPH radical scavenging activity.