Sahar Bahram vand; Seddiqe Mohammadi
Abstract
Introduction: AFB1 is a highly carcinogenic secondary metabolite of some species of Aspergillus. Recently, use of microorganisms has been increased to reduce the absorption of mycotoxins in gastrointestinal tract. So, in this study the effect of the three yeasts Saccharomyces cerevisiae, Pichia fermentans, ...
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Introduction: AFB1 is a highly carcinogenic secondary metabolite of some species of Aspergillus. Recently, use of microorganisms has been increased to reduce the absorption of mycotoxins in gastrointestinal tract. So, in this study the effect of the three yeasts Saccharomyces cerevisiae, Pichia fermentans, and Rhodotorula mucilaginosa on reduction of AFB1 in a simulated model of human stomach was investigated. Materials and methods: At first, A. flavus was isolated and then were purified. Then, AFB1 was produced in PDB media and presence of AFB1 was determined by blue fluorescence radiation under UV light. Toxin was extracted using the method of solvation in chloroform and injected into HPLC and the final concentration was 49 ng/ml. The simulated stomach was contaminated with 0.1 ml samples of AFB1 of three concentrations: 0.25 ng/ml and 0.50 ng/ml from standard AFB1 and also 49 ng/ml from the A. flavus under study. Then the yeasts were added and the mixture was incubated. After sampling at 0 and 120 minutes, the samples were centrifuged. The supernatants were separated to determine the concentration of residual toxin by direct competitive ELISA method. The experiment was conducted in a completely randomized design with a factorial experiment. The three factors included yeast (four levels: three yeasts and non-yeast treatments), concentration (four levels: 0, 0.25, 0.50 and 0.49 ng/ml) and time (two levels: 0 and 120 min). The whole experiment was carried out 3 times. Results & ddiscussion: The results showed that all three yeasts had the ability to reduce the toxin in the stomach compared to the control treatment (without yeast), but the effect of R.mucilaginosa was more significant than the other two. The lowest toxin concentration in supernatant was observed at 0.25 ng/ml. Over time, toxin concentration in supernatant decreased. The interaction of yeasts and toxin concentration showed that in comparison with the control, at each three concentrations, all three yeasts could reduce toxin concentration. The minimum toxin concentration in supernatant was obtained at 0.25 ng/ml in the presence of R.mucilaginosa. The results of interaction of yeast×time showed that after both 0 and 120 minutes, all three yeasts were able to reduce the toxin and the minimum toxin concentration was observed after 120 minutes for R.mucilaginosa. The results of interaction of time and toxin concentration in the model showed that at 0.25 ng/ml toxin concentration was at the lowest level after 120 minutes. The results of interaction of yeast×time×toxin concentration showed that the lowest toxin concentration was related to R.mucilaginosa after 120 minutes at 0.25 ng/ml. To conclude, the results of this study showed that all three yeasts had the ability to reduce AFB1 in the simulated model of human stomach, but R.mucilaginosa can be introduced as the most efficient isolate in biocontrol of AFB1.
Maryam Ebrahimi; Morteza Khomeiri; Yahya Maghsoudlou
Abstract
Introduction:Toxigenic fungi such as A. flavus grow widely in peanut and produce aflatoxins, a group of carcinogenic metabolites. Aflatoxin produced in peanut differed from the genetic variety of plant. The high humidity and moderate temperatures in the subtropical Caspian littoral of northern Iran could ...
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Introduction:Toxigenic fungi such as A. flavus grow widely in peanut and produce aflatoxins, a group of carcinogenic metabolites. Aflatoxin produced in peanut differed from the genetic variety of plant. The high humidity and moderate temperatures in the subtropical Caspian littoral of northern Iran could increase the growth of A. flavus and the production of aflatoxin. The objectives of this study were 1) to determine the chemical composition of peanut cultivars grown in Golestan Province, Iran, 2)to select resistant variety of peanut to aflaoxigenic A. flavus growth and 3) to evaluate relationship between A. flavus growth and changes in oleic and linoleic acid content and peroxide value. Materials and method: Peanut samples were used from four important varieties of peanut, Goli, Mahalli, China and India. those have been harvested from farms in Golestan province, Iran. Fat, protein, ash, moisture, reducing sugar, AFB1 content and peroxide value in each sample were measured by the standard method of AOAC. Fatty acids of the peanut seed oil were analyzed using gas chromatography (GC, Varian CP-3800 model) with a flame ionization detector (FID) and a DB-WAX column (50 m × 0.32 mm ×0.2 µm). To study the effects of A. flavus on peanut varieties, they were sterilized with 0.5% NaClO solution and then one ml of A. flavus spore suspension was added to every 20gr disinfected peanut and was placed in the incubator for eight days at 26°C. After incubation, the number of seeds colonized by fungi, spore production, AFB1 production, the association between colonization rate of hydrolysis of fatty acids and peroxide value were determined.Results and Discussion: The results showed that there were significant differences (P
Maryam Azizkhani; Fahimeh Tooryan; Maryam Boreiry
Abstract
Introduction: Mold growth on cheese is a common problem for cheese manufacturers during ripening and curing, as well as for the retailer and consumer during refrigerated storage. Listeria monocytogenes has gained increasing attention as a pathogen of public health importance owing to large numbers of ...
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Introduction: Mold growth on cheese is a common problem for cheese manufacturers during ripening and curing, as well as for the retailer and consumer during refrigerated storage. Listeria monocytogenes has gained increasing attention as a pathogen of public health importance owing to large numbers of foodborne outbreaks of listeriosis. Ingested by mouth, Listeria is among the most virulent of foodborne pathogens with up to 20% of clinical infections resulting in death. Various types of foods, mostly dairy products such as cheese, have been associated with these outbreaks and there is considerable interest in stopping this upward trend. As a result of the negative consumer perception of chemical preservatives, attention is shifting towards natural alternatives. A technique that has been used since ancient times to prevent fungal growth on foods such as cheese involves physically rubbing the product with certain herbs or spices or their oils. Therefore, regarding to the harmful effects of synthetic preservatives on consumers’ health, there is an increasing attention, both in food industry and authorities, to medicinal and aromatic plants as natural preservatives in food products. In this research, the effect of salvia and basil essential oils (EOs) on Listeria monocytogenes and Aspergillus flavus in Iranian white cheese has been investigated. Materials and method: Commercially available EOs from basil and salvia were used in this study (Pranarôm International, Ghislenghien, Belgium). EOs were analyzed by gas chromatography mass spectrometry (GC-MS). A broth microdilution assay was employed to determine the lowest concentration (MIC) in which visible growth of the bacterium is inhibited. The concentration of EO present in those wells that yielded plates with no visible colonies was considered to be the minimum bactericidal concentration (MBC). The effects of EOs on radial growth of fungal mycelium were assayed using an agar dilution method. The lowest concentration which inhibited the growth of the fungus was considered to be the minimum inhibitory concentration (MIC) whereas the lowest concentration of EO which killed the fungus (no growth observed on fresh medium) was taken to be minimum fungicidal concentration (MFC). Iranian ultra-filtered white cheese was produced in a commercial factory with different concentrations of EOs and the effects of EOs on bacterial and fungal growth in cheese during shelf-life were determined. Also, eight trained panellists performed sensory analyses. The panellists scored for colour, odour, flavour, overall acceptability and texture using a 9-point hedonic scale (1, dislike extremely to 9, like extremely).Results and Discussion: Main components of salvia EO included linalyl acetate and linalool and of basil EO consisted of linalool and α-cadinol. The MIC and MBC of salvia were obtained %0.015 and %0.02 and of basil %0.05 and %0.06, respectively, against L. monocytogenes. In the current report, L. monocytogenes was neither eliminated nor completely inhibited by basil EO, but salvia EO was able to inhibit its proliferation in cheese. The effect was even more pronounced with 1% salvia oil compared to 0.5% or 0.75%. Basil EO at a concentration of 1% caused a 7-day delay in the growth of L. monocytogenes. A growth delay of this type is particularly useful in terms of food safety for the short-term storage of products but not on prolonged storage as Listeria may reach high levels in foods over longer periods. MIC and MFC of salvia were %0.5 and %0.65, and of basil % 0.6 and %0.8, respectively, against A. flavus. At %0.35 and %0.5 the sporulation was inhibited by salvia and basil EOs, respectively. In the present study, no growth of A. flavus was observed in the presence of 1% of salvia EO, and colony diameter attained less than 5mm by the 21st day of cold storage in cheese samples treated with 1% basil EO. Also, the bacterial growth reduced up to 6 log cfu/g of cheese. EO of basil showed weaker antimicrobial effect compared to salvia EO. Cheese samples with different concentrations of EOs were evaluated and compared to the control sample to ascertain consumer acceptability for it. Significant differences were detected among samples containing EOs and the control sample in odour, color and texture, but the samples containing 0.75% and 1% of salvia EO were significantly impaired in both odour and taste as compared with the other samples. With regard to the overall acceptability, the cheese sample containing 0.75% of basil EO was the highest acceptable sample. Generally, it is well known that in complex systems such as cheese, several ingredients interact with each other and affect the sensory properties.In conclusion, the EO of salvia showed the greatest effect on limiting microbial growth. Both EOs could have potential for commercial use in improving the preservation of these products without the need for propionates or other synthetic additives. Further research could examine the utility of the combined application of basil and salvia EOs in different dairy products such as different types of cheese, as well as the use of different quantities/ratios for optimization of their antimicrobial effects.