The Effect of Water Extract of Rhus Coriaria L. on the Pathogenic Bacteria at Different Temperatures

Nowadays, natural preservatives are used in food industries rather than synthetic ones. Sumac fruit (Rhus coriaria L.) is widely used as an additive in meat products due to its antimicrobial effects. This study was conducted to examine antimicrobial properties of sumac at various temperatures. In this experimental study, the extract of sumac was prepared using soaking method. Different concentrations (3.12-50 mg/ml) of the extract were used against S. aureus, L. monocytogenes, S. typhimurium, and E. coli O157:H7 bacteria. Growth assessment curve, minimum inhibitory concentration (MIC), and the minimum bactericidal concentration (MBC) were evaluated using microplate method. The results of this study demonstrated that MIC (6.25 mg/ml) and MBC (12.5 mg/ml) belonged to S. aureus and L. monocytogenes bacteria, respectively. The extract could significantly attenuate growth of the four bacteria at 4°C and 25°C (p<0.05). The effect of the extract on Gram-positive bacteria was significantly more than Gram-negative ones (p<0.05). Temperature reduction also affected the growth of the bacteria; at 4°C bacterial growth was less than 25°C, that is, at 6.25 concentration, S. typhimurium, and E. coli populations reduced from 3.55 log and 3.31 log to 2.14 log and 1.06 log, respectively. According to our findings, water extract of sumac is a viable alternative to chemical food preservatives, particularly at 4°C.