POTENCIAL DO ÓLEO ESSENCIAL DE TOMILHO NA SANITIZAÇÃO DE RÚCULA

Abstract

Increasingly, minimally processed food stands out for its practicality in the meal preparation. Products in natura, including vegetables, require special care before reaching the consumer's table. For being considered safe for consumption, they must undergo a hygienic process to eliminate possible pathogenic microorganisms and to reduce other contaminating microorganisms to an acceptable level for human consumption. The type of sanitizer most used for this purpose is sodium hypochlorite solution; however, when used continuously, it can leave toxic waste and result in microbial resistance. For this reason, alternative sanitizers to chlorine are being studied, among them, essential oils, because they have antimicrobial compounds in their composition. In this context, the present study aimed to evaluate in vitro antimicrobial activity of thyme essential oil (Thymus vulgaris), and to apply it in the arugula (Eruca sativa) sanitization, aiming to increase its safety and shelf life. Antibacterial activity in vitro of the essential oil was evaluated by disc diffusion assays, minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) against different species of important bacteria in food. Results showed a strong antibacterial activity of the thyme essential oil for both Gram-positive bacteria and Gram-negative species tested, with MIC values ranging from 0.075 to 0.62 mg mL-1

. In the challenge test to evaluate the antibacterial activity in the thyme essential oil (0.2%) applied in the sanitization of arugula artificially contaminated with Escherichia coli (103 CFU mL-1 ), compared to sodium hypochlorite (120 ppm) and distilled water (negative control), there was no significant difference (p<0.05) between the treatments applied, except for a lower E. coli count in the sanitized arugula with sodium hypochlorite, on the second day of storage at 8°C. Afterwards, an experiment of applying the thyme essential oil (0.2%) as a sanitizing agent in minimally processed arugula was carried out to evaluate this vegetable shelf life, in comparison, to sodium hypochlorite (120 ppm) and distilled water (negative control). After the treatments, the arugula was stored at 8°C for seven days and periodically the number of aerobic mesophilic microorganisms, pH determination, and titratable acidity were counted, and the color of the samples was evaluated. The microbiological evaluation showed that the sanitation methods applied were not efficient to reduce the arugula natural microbiological contamination. Therefore, the pH of the samples increased during the storage period, which was also reflected on the titratable acidity reduction.