Augmentation of the stability of phycocyanin from Arthrospira maxima (Spirulina) by the addition of food preservatives and influence of pH on extracts obtained with different extraction procedures

Phycocyanin (C-PC) is a hydrophilic blue pigment found in cyanobacteria, rhodophytes, and cryptophytes. Its intense blue color and antioxidant capacity make phycocyanin an attractive substance for food and cosmetic industries. In this study, phycocyanin extracts from Arthrospira maxima, obtained by different extraction methods, were used to investigate the influence of preserving agents on thermostability of phycocyanin. C-PC remained stable at 60°C, but rapidly degraded at 70°C, and was completely lost at 80°C within 5 minutes. Addition of sorbitol, sucrose, and glucose at 32% (w/v) to phycocyanin extracted through ultrasonication and flocculation with chitosan in organic acid provided the highest stabilizing effects, with CR values of 96.67 ± 0.01 %, 83.41 ± 0.67 %, and 76.21 ± 1.34 %, respectively. The corresponding half-live values increased from 13.77 ± 0.21 min (control) to between 76.74 ± 5.12 and 614.83 ± 1.18 min, followed by xylitol, fructose, and maltose. Xylose, lactose, citric acid, and ascorbic acid showed no effects. The stabilizing effect of NaCl was dependent on pH of extracts, remaining stable at pH 6 – 7, but showing no significant effect at pH 3 – 4, and leading to precipitation. Incorporating 14 – 20% (w/v) NaCl in C-PC at pH 6.49 increased CR values from 88.61 ± 0.31 to 99.10 ± 0.01 %, with half-life values ranging from 172.03 ± 4.92 to 2291.19 ± 14.51 minutes. Conversely, the stabilizing effect of sugars was most effective in C-PC at pH 3 – 4, and least effective in C-PC obtained by freeze/thawing at pH 6 – 7.