The Use of Marjoram Essential Oil as a Preservative against Escherichia coli and Staphylococcus aureus in Baladi Cheese

Abstract

The increasing consumer preference for natural food preservatives necessitates innovative approaches to enhance food safety and extend shelf life. This study aimed to evaluate the antibacterial activity of Origanum majorana (marjoram) essential oil (EO) against Escherichia coli and Staphylococcus aureus, including antimicrobial-resistant (AMR) and heat-resistant (HR) strains, in Baladi cheese and investigate its effect on extending the shelf life. Various EO concentrations (250, 300, 500, 1000, and 25000 ppm) were tested to determine their impact on non-resistant E. coli growth for 7 days and determine the optimal concentration. The optimal concentration was then tested to check its efficacy on E. coli and S. aureus isolates survival in cheese. EO-supplemented cheese was inoculated with E. coli and S. aureus and stored at 4°C for testing over 21 days. Cheese samples were cultured on agar media and incubated at 37°C for 24h for E. coli and 48h for S. aureus for counting. Finally, the cheese supplemented with the optimal concentration of EO was tested to check its capacity to extend the product's shelf life and determine the consumer's overall acceptability using the triangle and a 9-point hedonic scale.

The results revealed that at 2500 ppm, EO significantly reduced bacterial counts, leading to complete elimination of HR E. coli and all S. aureus strains by days 21 and 7, respectively. In contrast, lower EO concentrations showed no significant antimicrobial effect. Additionally, EO extended the cheese’s shelf life by approximately 7 days by delaying coliform development compared to the control. However, the sensory evaluation revealed that all panelists unanimously rejected the EO-treated cheese, identifying intense flavor alterations as a limiting factor for acceptability. These findings underscore the potential of marjoram EO as a natural, effective preservative for dairy products, addressing microbial safety challenges and aligning with consumer demand for clean-label solutions. However, future research should focus on improving sensory acceptability, possibly through microencapsulation, and evaluating its economic feasibility in commercial food applications.