Investigating the effects of microalgae Spirulina platensis and Zedo gum on probiotic yogurt

The effects of incorporated Spirulina platensis (0-0.5 %) and Zedo gum (0-0.5 %) during storage time (1-21 days) on different manufactured yogurt types (plain/probiotic) through 20 treatments using Central Composite Design were investigated. Qualitative indices like pH, titrable acidity, probiotic viability evaluation by MRS agar medium including vancomycin, antioxidative capacity by 1, 1diphenyl 2 picryl hydrazyl radical inhibition assay, proteolysis pattern by o-Phthalaldehyde assay and overall sensory acceptance by linear scale method were evaluated. Statistical analysis and modeling revealed that incorporated Spirulina amount and storage time had significant effect on the pH and acidity (P<0.05). Regarding Lactobacillus paracasei viability, it was affected significantly by microalgae amount, storage time and interaction of gum-Spirulina amount. Also all studied variables had significant effect on proteolysis index (P<0.05) which might be related to Spirulina’s stimulant effect on the proliferation of yogurt starters and probiotic strain. Statistical analysis showed antioxidative properties of Spirulina platensis and Zedo gum in yogurt samples. The highest sensory score was obtained at 0.1 % Spirulina and 0.25 % Zedo gum which indicated a positive role of Zedo gum in the application of microalgae from sensory aspects.