Use of egg white protein powder based films fortified with sage and lemon balm essential oils in the storage of lor cheese

Edible film was produced by adding 3 % sorbitol (w/v) to egg white protein powder (EWPP). The first group of lor cheese samples was coated with a film fortified by sage essential oil (SEO) and the second group of samples was coated with films enriched by adding lemon balm essential oil (bEO) at various concentrations [0.5 %, 1 %, 2 % (v/v)]. The films were labeled as EWPPSEO(0.5), EWPPSEO(1), EWPPSEO(2), EWPPbEO(0.5), EWPPbEO(1), EWPPbEO(2) to indicate the type and the concentration of the additive. The third batch of the lor cheese samples was coated exclusively with non-fortified EWPP and the fourth batch was uncoated. All of the cheese samples were artificially contaminated with Escherichia coli O157:H7 (E. coli O157:H7), Listeria monocytogenes (L. monocytogenes) and Staphylococcus aureus (S. auerus). Viable cell counts of these species, yeasts and moulds were determined after the cheese production. All the samples were stored at +4 °C. Their physicochemical and microbiological properties were examined on the 1st, 7th, 15th and 30th day of the storage. Thereat significant (P<0.05) relationships between the increase in the essential oil concentrations and the increase in film thickness, water vapor permeability, inner and outer hardness, decrease in the weight loss, improvement in fat barrier property, and microbial counts during storage were found. These properties were found to be significantly affected in the 2 % (v/v) SEO and bEO samples, while the effects of other additive concentrations were insignificant (P>0.05). Physicochemical and antibacterial properties were more significant in SEO at all concentrations compared to bEO. However, the antifungal effect of bEO was higher than that of SEO. The antifungal effect of bEO was the same at 1 % (v/v) and 2 % (v/v) concentrations. E. coli O157:H7 was the most resistant microorganism to the essential oils while L. monocytogenes was the most sensitive. EWPP showed a bacteriostatic effect on the microorganisms and bactericidal effects were determined on the 30th day of the storage against L. monocytogenes and yeast-moulds.