Thermokinetic stability of phycocyanin and phycoerythrin in food-grade preservatives

Abstract

Phycocyanin (PC) and phycoerythrin (PE) are the main phycobiliproteins (PBPs) with application as colorants in food industries. In the present study, the thermokinetic stability of PBPs extracted and purified from a hot spring cyanobacterium, Nostoc sp. strain HKAR-2, was investigated. The individual components of PC and PE were isolated with a high purity ratio of 3.18 (A615/A280) and 7.2 (A563/A280), respectively. The thermokinetic stability of purified PC and PE was studied in the presence of edible preservatives such as benzoic acid, citric acid, sucrose, ascorbic acid, and calcium chloride over 30 days of incubation at 4, 25, and 40 °C. The rate of degradation (k value) of PC/PE was increased in the control (without preservative), while it declined in the presence of preservatives. The k value (day−1) was found to be the lowest for benzoic acid-treated PC/PE in comparison to the control at 4 °C. The rate of degradation also declined in benzoic acid-treated PC (0.008 day−1) and PE (0.012 day−1) at 40 °C in comparison with the control. Citric acid and sucrose were also found to maintain the stability of both PC and PE at the same temperature. Calcium chloride and ascorbic acid were shown to be the preservatives that support the least stability of PC and PE in comparison to the other preservatives studied. Overall, benzoic acid was found to be the best preservative for both PC and PE at 4 °C.