Phycocyanin-enriched yogurt and its antibacterial and physicochemical properties during 21 days of storage

Yogurt contained phycocyanin, owes its consumer satisfaction to their health benefits. Phycocyanin may have inhibitory effects on yogurt cultures duo to its antibacterial properties and also affects its physicochemical properties. It was the objective of study to evaluate the effects of phycocyanin on the antibacterial and physicochemical properties of yogurt. To prepare phycocyanin-enriched yogurt, when yogurt pH reached 4.5, purified phycocyanin was added, mixed and stored at 4 degrees C. Streptococcus thermophilus and Lactobacillus bulgaricus counts decreased significantly on days 21 and 14, respectively, in all the treatments. Pathogens were detected in none of the treatments. The phycocyanin enriched-yogurts was found to have a higher pH than the plain control and they showed increased viscosity with increasing phycocyanin concentration. The control yogurt showed a higher syneresis, which increased by day 14 but decreased on day 21 due to increases in the hydrophilicity of yogurt proteins. This is while the b(star) index did not decline significantly by day 14. PE-yogurt 4% (W/W) was not significantly different in overall acceptability from the plain yogurt. Because of positive effects of phycocyanin on yogurt such as decreasing syneresis, increasing firmness, color stability, and no pathogen growth it might be recommended as a bioactive colorant.