Evaluation of Antimicrobial Activity of Licorice Root Extract in Orange Flavored Carbonated Soft Drink

In this research، anti-microbial activity of ethanolic extract of licorice root against food spoilage microorganisms (Lactobacillus delbrueckii، Leuconostocmesenteroides، Candida krusei، Saccharomyces cerevisiae) in an orange flavored carbonated soft drink was investigated. The MIC and MBC of extract against Lactobacillus delbrueckii was 0. 7 mg/ml and 0. 8 mg/ml respectively، and against Leuconostoc mesenteroides MIC and MBC were 0. 9 mg/ml. Also، MIC and MBC against Candida krusei and Saccharomyces cerevisiae using microdillution method was equal to 0. 8mg/ml. In this research an orange flavored beverage preserved with natural licorice root extract was formulated and parameters such as phenolic contents، changes in population of aerobic mesophilic bacteria، yeast and acid-resistant micro-organisms during storage time were evaluated. Concentrations of 1000، 1500 and 2000 ppm of licorice root extract and samples containing 1000، 1500 and 2000 ppm of licorice root + 50% benzoate was used to control growth of food spoilage microorganisms in the beverage. Samples enriched with licorice root and a blank sample (commercial sample) were kept at room temperature and microbial counts were monitored during 1، 10، 20، 30، 40، 50، 60، 70، 80 and 90 days. Results of microbial examinations showed that the use of licorice root extract preserved the orange flavor carbonated soft drink during 90 days storage. Also، phenolic compounds showed good stability during 90 days storage time.