Release kinetics and antimicrobial properties of carvacrol encapsulated in electrospun poly-(ε-caprolactone) nanofibres. Application in starch multilayer films

Abstract

Electrospun poly-(ε-caprolactone) (PCL) fibre mats encapsulating Carvacrol (CA) were obtained with good encapsulation efficiency (85%) and CA load (11% in the fibre). These mats were effective at controlling the growth of Escherichia coli, when the surface density of CA loaded fibres was 1.2 or 1.8 mg/cm2, in line with the CA released into the culture medium that exceeded the MIC of the bacteria. However, they were not effective at controlling the growth of Listeria innocua, since a greater release of CA was necessary to achieve the MIC of this bacterium. It was not only the CA load in the fibres, but also its release capacity in the media that determined the antimicrobial effect. The fibre showed higher release rate and ratio in less polar simulants, D1 (50% ethanol) and D2 (isooctane) (representing fatty foodstuff), where practically the total amount of CA was released; whereas in more polar systems (simulants A (10% ethanol) and B (3% acetic acid)) a more limited CA delivery (60–75%) occurred, at a slower rate. The antimicrobial action of the active PCL mats was reproduced in multilayer starch films containing the CA-loaded electrospun PCL fibres between two starch sheets, with a slightly delayed response. In the multilayer films, a great reduction in the water vapour permeability was also observed with respect to that of starch films, without relevant changes in other functional properties of the films for packaging purposes.