Evaluation and comparison of antioxidant and antibacterial properties of phycocyanin extracted from spirulina algae (Spirulina Platensis) in both pure and nanoencasulated forms with maltodextrin-sodium caseinate combination coating

Following the concerns created in the field of using synthetic preservatives in various foods, it seems necessary to pay attention to natural compounds with preservative properties. Phycocyanin extracted from spirulina microalgae is one of these compounds. The aim of the present study was to extract (using enzymatic method) and nanoencapsulation of this pigment with maltodextrin-sodium caseinate combination coating and evaluate the antioxidant and antibacterial activity (against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Yersinia ruckeri and Streptococcus iniae) of nanocapsules in comparison with pure phycocyanin. The results showed that with increasing the concentration of phycocyanin (in both pure and nanoencapsulated forms), the antioxidant and antibacterial activity of the treatments increased significantly (p<0.05). Comparison of the properties of the treatments on days 0 and 60 (stored at -18°C) showed that the antioxidant and antibacterial activity of pure phycocyanin was significantly reduced over time (p<0.05). But the nanoencapsulation technique prevents the mentioned properties from changing and helps to preserve them. Among gram-positive bacteria, Listeria monocytogenes was more sensitive than the other two bacteria and all concentrations used had an inhibitory effect on this bacteri. Staphylococcus aureus was resistant to two concentrations of 2.5 and 5 μg/ml and Streptococcus iniae to three concentrations of 2.5, 5 and 10 μg/ml. Among the two gram-negative bacteria, Yersinia ruckeri was more sensitive and the concentrations used, with the exception of concentrations of 2.5 and 5 μg/ml, had an inhibitory effect on both bacteria. According to the results of the dilution method, for the studied bacteria, the MIC range was between 50-500 and the MBC between 100-500 μg/ml. Also, the lowest MIC was recorded for Listeria monocytogenes and the highest MBC was recorded for Streptococcus iniae. It can be concluded from this research that first, pure phycocyanin has antioxidant and antibacterial activity; second, nanoencapsulation of this pigment with combined coating of maltodextrin-sodium caseinate improves these properties and their stability during the storage period.