Physico-chemical, antimicrobial and antioxidant properties of gelatin-chitosan based films loaded with nanoemulsions encapsulating active compounds

The aim of this research was to develop and characterize gelatin-chitosan (4:1) based films that incorporate nanoemulsions loaded with a range of active compounds; N₁: canola oil; N₂: α-tocopherol/cinnamaldehyde; N₃: α-tocopherol/garlic oil; or N₄: a-tocopherol/cinnamaldehyde and garlic oil. Nanoemulsions were prepared in a microfluidizer with pressures ranging from 69 to 100 MPa, and 3 processing cycles. Films were produced by the casting method incorporating 5 g N_1,2,3,4/100 g biopolymers and using glycerol as a plasticizer, and subsequently characterized in terms of their physico-chemical, antimicrobial and antioxidant properties. No differences (p > 0.05) were observed for all films in terms of moisture content (18% w/w), and thermal properties. The films' solubility in water and light transmission at 280 nm were considerably reduced as compared to the control, N₁ (15% and 60% respectively) because of the nanoemulsion incorporation. The film loaded with N₁ showed the greatest (p < 0.05) opacity, elongation at break and stiffness reduction, and was the roughest, whilst the lowest tensile strength and ability to swell were attained by films loaded with N₃ and N₄, respectively. DSC and X-ray analyses suggested compatibility among the biopolymeric-blend, and a good distribution of nanodroplets embedded into the matrix was confirmed by AFM and SEM analyses. Films loaded with nanoencapsulated active compounds (NAC) were very effective against Pseudomonas aeruginosa, and also showed high antioxidant activity. Overall, the present study offers clear evidence that these active-loaded films have the potential to be utilized as packaging material for enhancing food shelf life.