STUDY OF THE EFFECT OF PHYCOERYTHRIN AND PHYCOCYANIN ON THE ANTIMICROBIAL AND ANTIOXIDANT ACTIVITY OF LOW-FAT MILK

Abstract

In recent years, the replacement of synthetic preservatives with natural ones has gained attention due to concerns about their potential harms and the beneficial biological properties of natural preservatives. This study aimed to investigate the effects of adding natural pigments, phycocyanin (PC) and phycoerythrin (PE), extracted from the cyanobacteria Desmonostoc ablorizicum and Neowestiellopsis persica A1387, on the physicochemical properties, colorimetry, antioxidant activity, and antimicrobial activity of samples. All tests were conducted on eight treatments: T1, T2, T3, and T4 with varying concentrations of PE (0.1%, 0.5%, 1%, and 2%) and T5, T6, T7, and T8 with varying concentrations of PC (0.1%, 0.5%, 1%, and 2%) over 28 days at different time intervals. Spectrophotometric results indicated that the highest concentration and purity of PE were achieved after 72 hours (p<0.05). Statistical analyses showed that, compared to treatments containing PC, those with PE exhibited significantly higher acidity and pH values (p<0.05). However, treatments and storage duration had no significant effect on Brix, fat, or protein content (p<0.05). Antioxidant activity, evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl) And Ferric Reducing Antioxidant Power (FRAP) methods, revealed that samples with higher PE concentrations exhibited 1.27 and 1.20 times greater antioxidant activity compared to those with PC, respectively. Additionally, colorimetric analysis showed that adding PC and PE significantly reduced the brightness index (L*) while increasing the a* and b* indices of milk samples (p<0.05). The total color change index (ΔE) also indicated a significant increase in overall color variation in milk samples with added PC and PE (p<0.05). Microbial counts, including total microorganisms, Enterobacteriaceae, and Yeast showed the highest growth in control and T1 treatments and the lowest in treatments containing PC and PE (p<0.05). Sensory evaluation of overall acceptability demonstrated that adding PC and PE significantly improved the sensory acceptance of milk samples (p<0.05). Overall, this study suggests that PE and PC, due to their numerous properties such as antioxidant and antimicrobial activities, can enhance the functional and safety characteristics of low-fat milk, demonstrating high potential for use in the dairy industry as safe and effective natural additives.