NOVEL INTEGRATED STRATEGIES OF NON-THERMAL FOOD PRESERVATION: COMBINATION OF HIGH HYDROSTATIC PRESSURE WITH ESSENTIAL OILS NANOEMULSIONS DELIVERED THROUGH DIRECT FOOD INFUSION OR BIOPOLYMERIC COATINGS

The combination of physical and chemical treatments was exploited to obtain naturally preserved products. Physical treatments were based on a non-thermal technology, such as high hydrostatic pressure (HHP), while chemical treatments were based on the use of natural antimicrobial compounds, such as essential oils (EOs), with the main challenge being the development of significant synergies between the two treatments, in order to minimize both HHP intensity and EO concentration.

Therefore, effective strategies of delivery of EOs were developed, in order accumulate them where microorganisms grow and proliferate, and therefore maximize the integration with the HHP treatment.

Two food matrices were tested: a vegetable (green beans) and a meat product (chicken breasts), where the EOs were applied in the form of nanoemulsions (160 nm in size), through incorporation in a chitosan-based edible coating or through direct infusion. Different essential oils were selected, depending on the product characteristics: green beans were coated with a modified (palmitoylated) chitosan layer containing a mandarin oil nanoemulsions, while chicken breasts were infused with a carvacrol nanoemulsion.

The food samples were tested in combination with HHP non-thermal treatments of mild intensity, ranging between 200 and 400 MPa, and duration between 1 s and 10 min.

For green beans, the combined treatment of coating formulation and HHP treatment showed very high antimicrobial effect against L. monocytogenes, with an evident a synergistic effect, which was able to ensure complete microbial safety over 13 days of refrigerated storage.

For chicken meat, the most interesting results were obtained by using 0.07 ml of nanoemulsion containing 2% carvacrol per gram of meat, treated at pressures of 300 MPa for 5 minutes of pressurization. Higher pressures (400 MPa) caused excessive protein denaturation of chicken, resulting in high organoleptic impact, while lower pressures (200 MPa) did not contribute significantly to antimicrobial activity.