The effect of Auricularia auricula aqueous extract (AAE) on the survival of Lactobacillus acidophilus La‐5 and Bifidobacterium bifidum Bb‐12, and on chemical and sensory properties of yogurt was investigated during 28 days of storage at 4°C. The use of 0.05% of AAE improved the survival of L. acidophilus La‐5 and B. bifidum Bb‐12 about 0.35 and 0.58 log CFU/g, respectively. However, AAE in 0.1% concentration enhanced the survival of L. acidophilus La‐5 and B. bifidum Bb‐12 about 0.43 and 0.51 log CFU/g, respectively. Moreover, 0.1% concentration of AAE drastically increased antioxidant activity and total phenolic content to 115.30 mg BHT eq./kg and 1,057.6 mg Gallic acid/kg after 28 days, respectively. Addition of AAE to the yogurt significantly decreased sensorial acceptance while increased syneresis compared to the control group (p < .05). In conclusion, the results of this study showed that addition of AAE improved probiotic protection and functional properties of the yogurt recommending its application in symbiotic yogurt.

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The effect of Stevia rebaudiana aqueous extract (Stevia) and microencapsulation on the survivability of Bifidobacterium bifidum Bb-12 and Lactobacillus acidophilus La-5 and assessment of chemical and sensorial characteristics in the symbiotic ice cream were studied for 90 days at À20°C. Free B. bifidum Bb-12 and L. acidophilus La-5 survived well, despite the significant differences between day 0 and day 90 of storage (P < 0.05). However, microencapsulation maintained the survival of probiotics by about 0.07 log CFU/g during the storage period. The use of Stevia and microencapsulation compared to other treatments significantly increased the log number of viable cells of B. bifidum Bb-12 and L. acidophilus La-5 during the storage time (P < 0.05). Moreover, the sensory and chemical properties of ice cream did not change significantly in all groups. In conclusion, the simultaneous utilisation of Stevia and microencapsulation is recommended for the survival of probiotics in ice cream or other dairy products.

Probiotics and Lactic Acid Bacteria play important roles such as the production of antimicrobial compounds and other metabolites. So they have positive effects on human health. When reactive oxygen species generated in excess or cellular defenses are deficient, biomolecules can be damaged by the oxidative stress process. Various studies have shown that the best way to protect the human body from the effects of oxidation reactions is to avoid them, which can be accomplished by using antioxidants. Due to the damages of synthetic antioxidants, their usage has been discussed. Nowadays natural antioxidants derived from bio-resources have recently gained a lot of attention as a potential replacement for synthetic antioxidants. Probiotic bacteria are thought to defend against oxidative stress by restoring the gut microbiota, according to hypothesis of some scientists. This type of microorganisms indicated their antioxidant activity by producing and increasing antioxidant enzymes, production of secondary metabolites, small hydrolyzed peptides in food, resistance to the presence of hydrogen peroxide, and production of intracellular and extracellular compounds such as Exopolysaccharides. Also, they have shown their positive effect on in vivo models. In conclusion, according to the results of studies, lactic acid bacteria and probiotics are significant sources of natural antioxidants. Therefore, they have important research value and market development potential. Also, it should be noted that the mechanism of antioxidant activity of this group of microorganisms has not been fully investigated, this requires further research.