The aim of this study was to evaluate the effects of adding various medicinal plants to kombucha medium and to analyze the changes that occur to its physicochemical, antimicrobial, and sensorial properties. In the first part, measurements were made to determine IC
50 value, total phenolic content, total flavonoid content, minimum inhibitory concentration, pH, organic acids, and sensorial properties of kombucha that contained cinnamon, cardamom, or Shirazi thyme. Results showed that kombucha samples containing cinnamon exhibited higher antioxidant and antimicrobial activities, more organic acids, and better sensorial scores. In the second part, properties of kombucha containing 25%–100% concentrations of cinnamon were evaluated. The result showed that by increasing the cinnamon concentration, certain increases were observed in the amounts of organic acids and in the magnitudes of antioxidants and antimicrobial activities. In conclusion, antioxidant and antimicrobial activities of kombucha can be increased by adding medicinal plants, especially at higher concentrations.
In this study, the oxidative stability of beef burgers incorporated with Shirazi thyme, cinnamon, and rosemary extracts was compared with that of BHT-incorporated and antioxidant-free samples. The chemical composition, TBARS, metmyoglobin, pH, color, and microbial and sensory characteristics were evaluated during storage at −18 ∘ C for 2 months. The results indicated that Shirazi thyme and cinnamon extracts did not change the colorimetric properties significantly ( < 0.05). Incorporating natural antioxidants led to a significant ( < 0.05) reduction in TBARS (36.58-46.34%) and metmyoglobin (16.25-18.47%) as compared to control. Except for the control sample, total microbial counts of burgers were lower than the maximum allowed limit. Burgers formulated with Shirazi thyme revealed the lowest amount of total count. Regarding the sensory characteristics, the overall acceptability of different samples decreased in the order of cinnamon > BHT > Shirazi thyme > rosemary > control. Finally, the results showed that these plant extracts can be utilized as an alternative to synthetic antioxidants in formulation of burgers.
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