mahbobeh sarabi-jamab

Monascus purpureus can produce a wide range of natural pigments so attract the attention of food producers as substitute of synthetic colors. Monascus pigments usually accompanied with citrinin contamination which limits their wide application in foods. The usage of Saccharomyces cerevisiae is known as a useful biological way for citrinin elimination. In this study, the effect of  Saccharomyces cerevisiae cells in twomodes of treatment (heat treatment at 121  °C and acid treatment in 2M HCL) and live at three different concentrations (103, 104, 105 CFU/mL) were investigated on the amount of citrinin and yellow, orange and red pigments produced by Monascus purpureus. The results showed that live yeast cell and yeast cells treated by heat and acid significantly decreased the citrinin in culture, so that citrinin content decreased from 4.43 mg/L in control sample to 0.9, 0.10 and 0.07 mg/L (at 105 CFU/mL yeast suspension) respectively. The maximum amount of yellow, orange and red extracellular and intracellular measured pigments belong to the samples with live yeast, while the amount of this pigments in the samples containing yeast treated with heat and acid reduced respectively. Among the treatments, the use of live yeast at concentration of 104 CFU/mL per milliliter provided the best conditions to achieve the desired goal.

In this research, determining the optimal conditions for extraction of Salvia leriifolia leaf by traditional solvent extraction method (with different solvent ratio of water/ethanol 50:50, 60:40 and 70:30 at temperatures of 70, 80 and 90 ºC and time duration of 30, 75 and 120 min) in order to investigate the antimicrobial activity of the extract, using response surface method was carried out. The  analysis of variances showed that the effect of all three independent variables on the dependent variables (the diameter of the inhibition zone of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella enteritidis, Saccharomyces cerevisiae and Aspergillus niger) was significant (P<0.05). Optimum extraction conditions including temperature of 83.60 ºC, extraction time of 60.92 min and water to ethanol ratio of 59.09 were obtained. Regarding the diameter of the inhibition zone of microorganisms, the highest inhibition zone belonged to Saccharomyces cerevisiae and Staphylococcus aureus.The optimization of extraction method resulted in extracts with the highest antimicrobial activity, especially against yeast and Gram-positive bacteria. In addition, predicting evaluation models provided an effective step in selecting extraction conditions to achieve a combination of antimicrobial properties against each microbial group.