Antimicrobial activity and the properties of edible hydroxypropyl methylcellulose based films incorporated with encapsulated clove (Eugenia caryophyllata Thunb.) oil

Antimicrobial activity and the properties of edible film were studied by incorporating with encapsulated clove (Eugenia caryophyllata Thunb.) oil as a natural antibacterial agent. The minimal bactericidal concentration (MBC) of clove oil inhibited the growth of E. coli O175:H7, S. aureus and L. monocytogenes were tested in the stationary phase. The results showed that 1.0, 1.5 and 0.5% of clove oil inhibited about 10^5 cfu/mL of E. coli O175:H7, S. aureus and L. monocytogenes in vitro experiments respectively. Antimicrobial edible films were prepared by incorporating encapsulated clove oil from 1, 2, 3 folds of MBC into 1.5% of hydroxypropyl methylcellulose (HPMC) film solution. The edible HPMC films exhibited antibacterial activity against pathogenic bacteria tested by using agar diffusion assay. The results showed that increasing encapsulated clove oil in the edible HPMC films from 1, 2, 3 folds of MBC yielded a higher inhibition zone from 18.50-26.75, 28.75-39.00 and 16.67-31.00 mm of E. coli O175:H7, S. aureus and L. monocytogenes, respectively. Tensile strength, elongation at break, water vapor permeability, and film solubility were significantly (p 0.05) decreased with the incorporation of encapsulated clove oil. The color of edible HPMC films was affected by the addition of encapsulated clove oil; the results showed that increasing the encapsulated clove oil resulted in darker and more yellowish films. The lower transparency of the edible HPMC films was noticed when a greater amount of encapsulated clove oil was incorporated (p 0.05). Encapsulated clove oil filled edible HPMC films provided the films with a rougher surface than pure edible films.