Release of thymol from poly(lactic acid)-based antimicrobial films containing kenaf fibres as natural filler

Abstract

10The migration of thymol, a natural antimicrobial (AM) substance, from poly(lactic acid) (PLA) 11 films containing 300 g/kg kenaf fibres into food simulants is reported. Neat PLA and PLA/kenaf 12 films containing 100 g/kg thymol were prepared via melt blending and heat pressing and were 13 placed in contact with 150 mL/L and 950 mL/L ethanol/water mixtures at different temperatures. 14 First-order kinetics, diffusion modelling and Fick's law modelling were used to describe the 15 release. The release rate of thymol into 950 mL/L ethanol/water at different temperatures 16 displays Fickian behavior with diffusion coefficient values between 1 and 100 × 10 -11 m 2 s -1 with 17 close to 100% of thymol being released. The release rate of thymol is temperature dependent and 18 is affected by the percentage of ethanol in the simulant. In the case of neat PLA and PLA/kenaf 19 films, a faster release occurred in 950 mL/L ethanol/water than in 150 mL/L ethanol/water with 20 the composite film exhibiting a higher diffusion coefficient in each case. 21 22

Effect of Poly(Lactic Acid)/Kenaf Composites Incorporated with Thymol on the Antimicrobial Activity of Processed Meat

“…; Tawakkal et al . ). Similar results have also been observed in other systems whereby it was suggested that the presence of larger micro‐voids in solvent‐cast films of PLA/poly(ε‐caprolactone) (PCL) containing thymol facilitates the release of the AM agent to the surface of the film and improves its AM activity against E. coli after 24 h in liquid media (Wu et al .…”

“…Moreover, hydrophilic fibers can swell when immersed in liquid media resulting in internal stresses generated in the adjacent polymer matrix that may produce micro‐cracks, further facilitating the release of thymol (Tawakkal et al . ).…”

“…The presence of kenaf fibers in the polymer matrix may create voids thereby leading to the release of thymol (Tawakkal et al 2016b). This finding is consistent with the observation made in relation to previous scanning electron microscope images where visible voids in the composite materials are shown as well as the diffusion rates of thymol from the PLA/kenaf films into fatty and aqueous food simulants that have been previously reported (Tawakkal et al 2014;Tawakkal et al 2016b).…”

“…The presence of kenaf fibers in the polymer matrix may create voids thereby leading to the release of thymol (Tawakkal et al 2016b). This finding is consistent with the observation made in relation to previous scanning electron microscope images where visible voids in the composite materials are shown as well as the diffusion rates of thymol from the PLA/kenaf films into fatty and aqueous food simulants that have been previously reported (Tawakkal et al 2014;Tawakkal et al 2016b). Similar results have also been observed in other systems whereby it was suggested that the presence of larger micro-voids in solvent-cast films of PLA/poly(e-caprolactone) (PCL) containing thymol facilitates the release of the AM agent to the surface of the film and improves its AM activity against E. coli after 24 h in liquid media (Wu et al 2014).…”

Biopolymer films and the effects of added lipids, nanoparticles and antimicrobials on their mechanical and barrier properties: a review

“…The antimicrobial effects of edible and coating films with essential oils have been screened against a wide range of microorganisms over the years. Several researchers have proposed that the antimicrobial action of essential oils may be attributed to their ability to penetrate through bacterial membranes to their interior of the cell and exhibit inhibitory activity on the functional properties of the cell, and to their liphophilic properties (Cristescu et al, 2016;Calo et al, 2015;Cheng et al, 2015;Oliveira et al, 2015;Atar es & Chiralt, 2016;Tawakkal et al, 2016).…”