ANTIMICROBIAL ACTIVITY OF ESSENTIAL OILS APPLIED IN DARK CHOCOLATE

Several outbreaks of Salmonella continue to occur today in chocolate. Among the strategies for microbial control in food, the addition of essential oils (EOs) appears to be an alternative from natural sources instead of chemical additives. Based on this, the aim of this study was to investigate the antimicrobial potential of EOs from Thymus vulgaris (TvEO) and the blend of T. vulgaris and Cymbopogan citratus (TvCcEO) in dark chocolates against the pathogen S. Typhimurium ATCC 14028. At first, the minimum inhibitory (MIC) and bactericidal (MBC) concentration of the EOs were determined using the plate microdilution method. For the evaluation in situ, EOs were inoculated into the chocolate mass according to their MBC for S. Typhimurium. After homogenization, the samples were packed in sterile plastic bags and stored at 25 °C ± 2 °C for 0, 7, 14, 30 and 45 days. In each time interval, samples were taken to enumerate S. Typhimurium using the plate counting technique. MIC and the MBC were 0.3 and 0.35 mg/mL for TvEO and 0.6 and 1.0 mg/mL for TvCcEO, respectively. At time 0, the initial population was ∼6 log CFU/g in all treatments. After 7 days, there was a reduction of ∼3 log CFU/log, which was maintained until 30 days for the control and TvEO treatments, while the TvCcEO treatment had a count of 2.56 log CFU/g over the same period. In 45 days of storage, the count of the control (2.65 log CFU/g) did not differ from TvEO (2.76 log CFU/g) and TvCcEO (2.54 log CFU/g) treatments. The results suggest that OEs had no significant effect on the reduction of the target microorganism.