Thermoplastic starch/clay nanocomposites loaded with essential oil constituents as packaging for strawberries − In vivo antimicrobial synergy over Botrytis cinerea

Abstract

Nanocomposite films based on thermoplastic starch/montmorillonite containing essential oil constituents (TPS/MMT/EOCs) carvacrol (CRV) and thymol (TML) were prepared by extrusion method to produce an antimicrobial material for a potential use as fresh fruit packaging. X-ray diffraction and transmission electron microscopy analysis of the nanocomposites showed intercalated/exfoliated morphology which resulted an increasing of mechanical and thermal resistance properties (9- and 2-fold respectively) respect to the neat TPS. An approximately 43% decrease in EOCs release parameters compared to the neat TPS was observed, that could indicate a potential material to function as a controlled-release active food packaging. In vivo additive/synergistic antimicrobial effect over Botrytis cinerea-inoculated strawberries was observed when the association of CRV and TML was included in the nanocomposite formulation respect the nanocomposites containing only CRV. A drastic reduction of 2.4-fold of inhibitory concentration IC50 from 14.16gkg−1 of total EOCs (nanocomposites containing only CRV) to 5.90gkg−1 of total EOCs for nanocomposites containing the association CRV:TML (50:50) was achieved by storing Botrytis cinerea-inoculated strawberries for five days at room conditions in indirect contact with nanocomposite films. By reducing almost one third of the total EOCs in the film, a material with antimicrobial effectiveness over Botrytis cinerea was obtained but without altering neither strawberry fruit quality parameters such as weight loss, firmness, external color and chemical properties, nor organoleptic properties (p>0.05) confirmed after discriminant sensory analysis.