Browsing by Subject "molds"

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  • Radi, Fatima Zahrae; Bouhrim, Mohamed; Mechchate, Hamza; Al-zahrani, Mohammed; Qurtam, Ashraf Ahmed; Aleissa, Abdulmalik M.; Drioiche, Aziz; Handaq, Nadia; Zair, Touriya (2022)
    Essential oils (EOs) are chemical products produced by odoriferous glands from a variety of plants. These essential oils have many health benefits: antiseptic, anti-inflammatory and antimicrobial activities. So due to these medicinal properties, the present study was designed to analyze essential oils of Thymus zygis L. and Thymus willdenowii Boiss. for their chemical composition and biological activities. These two thyme species were collected from the region of Ifrane, Middle Atlas of Morocco. The EO was obtained by hydrodistillation, and the yields were 5.25% for T. zygis and 3.00% for T. willdenowii. The chemical composition of the EOs was analyzed by gas chromatography coupled with mass spectrometry (GC-MS), and the results showed that T. zygis EO is dominated by carvacrol (52.5%), o-cymene (23.14%), and thymol (9.68%), while the EO of T. willdenowii contains germacrene D (16.51%), carvacrol (16.19%), and geranyl acetate (8.35%) as major compounds. The antioxidant activity assessed by Diphenylpicrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays revealed that both EOs have excellent antioxidant activities; by DPPH it resulted in IC50 = 6.13 +/- 0.11 for T. zygis and 6.78 +/- 0.3 mu g/mL for T. willdenowii, while the one by FRAP yielded EC50 = 2.46 +/- 0.01 (T. zygis) and 5.17 +/- 0.2 (T. willdenowii) mu g/mL. The antimicrobial activity of the two essential oils was evaluated against six bacterial strains and five fungal strains by the disk diffusion method to determine the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC). The EOs revealed variable antimicrobial activities against the different tested microbial strains and showed strong antimicrobial activities, even against strains known as multi-resistant to antibiotics (Acinetobacter baumannii) at low concentrations (2 mu L/mL). T. zygis EO showed the most powerful activity against all the studied bacteria, while that of T. willdenowii recorded moderate activity when tested against Shigella dysenteriae and Salmonella Typhi. With inhibition diameters that vary between 75 mm and 84 mm for concentrations of 2 mu L/mL up to 12 mu L/mL, S. aureus was shown to be the most sensitive to T. zygis EO. For the antifungal activity test, T. zygis EO showed the best inhibition diameters compared to T. willdenowii EO. These results showed that T. zygis EO has more powerful antioxidant and antimicrobial activities than T. willdenowii EO, therefore, we deduce that thyme EOs are excellent antioxidants, they have strong antimicrobial properties, and may in the future represent new sources of natural antiseptics that can be used in pharmaceutical and food industry.
  • Navarro, Andrea (Helsingin yliopisto, 2017)
    Mold spoilage is the main cause of bread spoilage. The fungal species that mostly contaminate bakery products belong to the genera Penicillium, Eurotium, Aspergillus, Monilia, Endocymes, Cladosporium, Fusarium, Neurospora and Rhizopus. The aims of the experimental work were: (1) to screen LAB strains previously isolated from bakery and sourdough environment for their antifungal properties and to be used as starters for sourdough with antifungal activity, and (2) to evaluate sourdough effects on the shelf life of white wheat bread, without affecting the textural properties. Three methods were used to determine the antifungal activity of the isolates. First, the mechanism of fungal inhibition was investigated by an agar diffusion assay with P. paneum and P. albocoremium as indicators. The inhibitory activity toward bakery-related fungi was tested with the radial growth rate of fungi measured after seven days with six indicator molds. The isolates L. pentosus/plantarum J42 and L. mesenteroides I21 were tested in the baking trials, which were conducted in the pilot plant. Physicochemical analysis and microbiological observation were performed on bread slices and loaves produced with 30% sourdough, packed and stored in polyethylene plastic bags under natural conditions at a room temperature of ~ 24 ºC in the pilot plant. The water-soluble extracts from L. pentosus/plantarum, L. mesenteroides, P. pentosaceus and W. confusa had the highest inhibition activity. L. plantarum, W. confusa, L. pseudomesenteroides/mesenteroides and L. mindensis/crustorum had low activity toward the indicator molds. Minor inhibitory effect was observed toward P. albocoremium. Overall, the highest antifungal activity toward the indicator molds was shown by L. mesenteroides I21 strain. The pH values of the water-soluble extract and the sourdough did not seem to influence the fungistatic effect observed of the selected strains toward the molds. Addition of sourdough caused no changes in the physical properties of bread. Sourdough breads had less mycelial coverage relative to the control bread. In the conditions of this study, sourdough addition was beneficial to decrease mold contamination in bread.