Sugar-mediated thermal stabilisation of C-phycocyanin from Arthrospira platensis

Abstract

C-phycocyanin (C-PC), the major protein of cyanobacteria Arthrospira platensis, is a blue pigment that primarily transfers energy during photosynthesis.It has diverse biotechnological applications since it can be used in nutraceutical, cosmetics, pharmaceutical industries, and biomedical research.Its intensive blue colour and strong antioxidant activity give C-PC significant potential to replace synthetic colourants in the food industry. However, thermal treatment of food has detrimental effects on C-PC colour due to sensitivity to higher temperatures; therefore,the application of this natural colourant in food and other products is limited. Hence, improving C-PC stability is the major challenge for successful application in food and beverages colouring. In the light of this,we aim to investigate the thermal stability of C-PC in the presence of selected sugars (glucose, fructose and sucrose), commonly used in the food industry. Ex-situabsorption spectrophotometryshowed that 18% solution (w/v) of glucose, sucrose and fructose at pH 7,upon incubation at 65℃, exhibit 91.4, 52.9 and 52.5% of colour preservation, respectively.In situ fluorescence measurements revealed that free C-PC has a melting point of 55.4°C, while the presence of glucose and sucrose increases the melting point of C-PC to 64.4 and 61.4°C, respectively. On the other hand, fructose does not significantly influence the C-PC melting point. These results show that the thermal stability ofthe CPCsolution is substantially increased in the presence of sugars, while the type of sugar significantly determines the extent of the stabilisation effect. Overall, our study provides the strategy for enhancing the application potential of C-PC as natural food colourant, providing a food product with vivid blue colour and substantial antioxidant activities.