Biodegradable composites from polyester and sugar beet pulp with antimicrobial coating for food packaging

Totally biodegradable, double‐layered antimicrobial composite films were introduced for food packaging. The substrate layers of the sheets were prepared from poly(lactic acid) (PLA) and sugar beet pulp (SBP) or poly (butylene adipate‐ co ‐terephthalate (PBAT) and SBP by a twin‐screw extruder. The active layer consisting of antimicrobial in either PLA or chitosan was formed on the surfaces of the substrates by solution coating followed by solvent evaporation. Air‐coupled ultrasonic evaluation and microscopic examination showed a homogeneous structure for the composite sheets. Mechanical analysis and acoustic emission demonstrated the double‐layered composites possessing appropriate tensile strength and fracture characteristics for the use as light weight‐bearing materials. The release of Nisaplin ® or allyl isothiocyanate (AIT) effectively suppressed the growth of Listeria monocytogenes and Salmonella cells, respectively; the co‐release of Nisaplin ® and AIT played a synergistic effect on inhibition of L. monocytogenes .