Analyzing Rosmarinus officinalis essential oil and its nanoemulsion in beef burgers shelf life at refrigerator temperature

Recently, plant essential oils and their nanoemulsions have received great attention since they help reduce the microbial load and improve the food products’ antioxidant activity. In the present research, rosemary essential oil (REO) and nanoemulations of rosemary essential oil (NREO), were added to a hamburger at different levels, and the properties were checked at refrigerator temperature. The results showed that the most compounds of REO were α-pinene (12.32%), 1, 8-Cineole (12.02%), Camphene (9.21%), Limonene (8.11%), Camphor (7.13%), Bornyl acetate (6.18%), Borneol (6.11%) and Verbenone (5.21%). The mean diameter of inhibition zone against Staphylococcus aureus and E. coli for NREO was considerably more than the one for REO (p ≤ 0.05). The phenol content and antioxidant activity of REO were significantly higher than that of NREO (p ≤ 0.05). In all the studied days, except on the 1st day, the highest amount of peroxide value, thiobarbituric acid and microbial population (mesophilic bacteria, psychrophilic bacteria and coliform bacteria of the samples) belonged to sample 1 (control sample). And the lowest amount of the mentioned factors belonged to hamburger containing NREO (p ≤ 0.05). The highest sensory scores (smell, taste, texture, and overall acceptance) were for hamburger which contained NREO (p ≤ 0.05). The hamburger containing NREO, was selected as the one with the superior treatment due to its lower microbial load, and higher sensory evaluation score.