# Chios Mastic Essential Oil in Sodium Alginate Edible Films Combined with High-Pressure Processing as Listeria monocytogenes Inhibitors in Cheese Slices

## TL;DR

This study shows that Chios mastic essential oil in edible films, combined with high-pressure processing, can effectively inhibit Listeria in cheese slices.

## Contribution

Combining mastic EO films with HPP for Listeria inhibition in cheese is a novel food preservation approach.

## Key findings

- Mastic EO at 2% in edible films suppressed Listeria growth in cheese slices.
- High-pressure processing (HPP) alone or combined with MEFs showed highest efficacy against pathogens.
- FTIR spectroscopy proved effective for monitoring biochemical changes in cheese slices.

## Abstract

The antimicrobial effect of Chios mastic gum essential oil (mastic EO) was evaluated in vitro in a variety of spoilage and pathogenic bacteria and yeast strains isolated from spoiled cheeses with concentrations ranging from 0.006 to 2% (Minimum Inhibitory Concentration (MIC)) and in situ (cheese slices). The mastic EO (2%) was incorporated in sodium alginate edible gel films (Mastic Edible Films (MEFs)), and then the films were applied between the cheese slices that had been previously inoculated with a cocktail of three strains of Listeria monocytogenes (on both sides of the slices) and subjected or not to high-pressure processing (HPP). Cheese samples were vacuum-packaged and cold stored (4 °C), and microbiological, pH and organoleptic (in pathogen-free slices) analyses were employed, while Fourier Transform Infrared (FTIR) spectroscopy was applied as a rapid technique to monitor the biochemical changes present on the slices. Samples without MEF, without the pathogen and with or without HPP were employed as controls. Results showed that the MIC of the mastic EO varied from 0.01% to 1.8% depending on the species and/or strains. Pathogen’s growth was suppressed by HPP, MEF or their combination, which showed the highest efficacy. These results could provide useful data to support risk assessment studies on ready-to-eat foods. Finally, FTIR implementation with data analytics was found to be satisfactory, indicating FTIR’s potential as a reliable information source for cheese quality control.