BACKGROUND: Today, there is an increasing concern about the consumption of synthetic colorants in food because of their possible health hazards. Monascus purpureus has attracted a great deal of attention as it produces various coloured pigments with high chemical stability, but it also produces citrinin, a secondary toxic metabolite, along with the pigments. This study aims to investigate the amount of pigment and citrinin reduction by different treatments with Saccharomyces cerevisiae such as heat treatment and suspension concentration.
RESULTS:The results indicated that the ability of S. cerevisiae regarding citrinin adsorption increased with increase of temperature and yeast concentration. The maximum extent of citrinin adsorption was related to heat treatment at 121 ∘ C and a yeast concentration of 10 5 cells mL −1 , for which citrinin reduced from 4.43 mg L −1 in control to 0.1 mg L −1 . Heat treatment of 10 3 cells mL −1 suspension of S. cerevisiae cells at 50 ∘ C, with 0.56 mg L −1 citrinin remaining in the medium, showed the lowest ability for citrinin binding. The optimum absorbance of all red, orange and yellow pigments was observed for the heat treatment at 50 ∘ C and yeast concentrations of 10 3 and 10 4 cells mL −1 which was greater than that for the control.
CONCLUSIONS:We can conclude from this study that heat treatment with S. cerevisiae can be a useful way to reduce citrinin to below the standard limits.
The aim of this study was to determine the antifungal effect of the essential oil obtained from Ziziphora clinopodioides L on two fungi species including Aspergillus flavus and Aspergillus parasiticus using microdilution method. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined for the essential oil at 10 different concentrations (i.e. 25,000, 12,500, 6250, 3125, 1562.5, 781.25, 390.625, 195.31, 97.65, and 48.82 µg/ml). Finally, the effect of the essential oil at six levels (6250, 3125, 1600, 800, 400, and 196 µg/ml) was investigated on the growth and activity of A. flavus and A. parasiticus, and also toxin production of these species in maize at 0.97 aw and 25°C after 29 days. Aflatoxin B1 (AFB1) content was assayed by enzyme linked immuno-sorbent assay technique. Results showed that essential oil of Z. clinopodioides was found more effective on A. parasiticus than A. flavus in both in vitro and in vivo conditions. Z. clinopodioides oil exhibited the same MIC value in the liquid medium against all fungal strains (48.82 µg/ml), while it showed different activity against A. flavus and A. parasiticus with MFC values of 781.25 and 390.625 µg/ml respectively. Under storage condition in maize, AFB1 production was significantly (p < 0.05) repressed at the concentration of 6250 µg/ml for A. flavus and 6250 and 3125 µg/ml for A. parasiticus. At the lower concentrations, the AFB1 production increased gradually. The results of the present study indicated that the essential oil of Z. clinopodioides had significant antifungal activity (p < 0.05); therefore, it can be used as an antifungal agent in the food and medicinal industries.
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