Chemical composition, antimicrobial, antibiofilm and insecticidal enhancing of Eucalyptus citriodora essential oil and its potential to shelf-life extension of pumpkin after inoculation of Salmonella enterica

Abstract

Our study aims to investigate the chemical composition and to evaluate the antibacterial (in vitro, in situ) and insecticidal activities of E. citridiora essential oil (ECEO), given the current emphasis on the use of natural resources, particularly essential oils, in food production to improve sensory attributes and prolong shelf-life. In addition, microbiological studies of pumpkin sous vide treated with ECEO after being inoculated with Salmonella enterica were evaluated at one and seven days of the trial. GC/MS analysis of the examined essential oil showed the presence of 30 volatile compounds (92.7% of the total). Monoterpene aldehyde citronellal (65.1%), as well as monoterpene alcohols isopulegol (8.3%), citronellol (6.5%) and iso-isopulegol (4.2%) are the most abundant compounds. Measured using the disc diffusion method, the antibacterial activity of the EO ranged from 5.67 mm for Candida albicans to 17.67 mm for Bacillus subtilis subsp. Spizizenii. The lowest minimal inhition concentration was found against S. epidermidis and Enterococcus faecalis (MIC₅₀ 0.140 and 0.155 mg/mL and MIC₉₀ 0.177 and 0.184 mg/mL). In the vapor phase, the best antibacterial activity was shown against S. epidermidis in the strawberry model, Yersinia enterocolitica in the apricot model, S. enterica forming biofilms in the cucumber model and S. epidermidis in the pumpkin model. The growth of S. enterica was inhibited and the microbial count was decreased by using the sous vide method in combination with ECEO treatment. The bacteria Bacillus amyloliquefaciens subsp. plantarum, Bacillus licheniformis, Bacillus safensis, Acinetobacter calcoaceticus, Pseudomonas ludensis, and Rhizobium radiobacter were the most isolated microbiota found in the sous vide pumpkin. In our study, ECEO was found to significantly affect the degradation of S. enterica biofilm. It is first assessment of insecticidal activity of EO against Megabruchidius dorsalis which was sensitive to the ECEO. According to our knowledge, the antimicrobial and insecticidal activity demonstrated in our ECEO study suggests that it may have a rationale for application in the food sector as an additive to prolong the preservability of processed foods and has good potential for use as a natural pesticide.