The research shows it is possible to make active packaging showing water scavenger and antimicrobial activities from pseudo-multilayered films by extrusion processing and from multilayered films by co-extrusion processing, said Alix et al.
Chitosan, polycaprolactone and wheat-based polymers were combined to make the food packaging films with water scavenging and antimicrobial properties.
Polycaprolactones (PCL) were blended in a starch based matrix to improve the contact suitability with food to the packaging and to obtain a modulated water-scavenger effect and chitosan was included in the formulation to reduce the bacterial adhesion potential on the packaging.
Starch based blends were compared to thermoplastic materials produced from flour without any treatment.
Concerns about the mechanical properties and gas permeability can be solved by blending starch with another polymer, said the researchers.
Different wheat starch or wheat flour based blends with PCL were formulated and processed by extrusion or co-extrusion and an antimicrobial agent, chitosan (CS), was added to the formulation.
PCL, starch and CS were selected because they can be extruded without degradation within the same range of temperature (80-110°C).
Pseudo-multilayered films were performed by starch or flour powder being plasticized with glycerol (20% w/w) and water (10% wt.) by twin-screw extrusion after blending in a turbomixer, by thermoplasticized starches (TPS) or thermoplasticized flour (TPF) granulates were blended with PCL granules and extruded by a single-screw extruder and the blend compounds were cast-extruded to obtain films.
The researchers used different screw speeds on the processing parameters (10, 30, 50 and 70rpm) for the TPS/PCL37 (80/20 w/w) and TPS/PCL50 (80/20 w/w) blends provided in different molecular masses (37kg/mol,50kg/mol and 80kg/mol)
“The results show an influence of the screw speed in the case of TPS/PCL37 blends and no influence in the case of TPS/PCL50 blends.
“Then, it appears that the PCL37 needs increased time to migrate to the surface in the TPS matrix.”
After processing, the structure of the films was characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM).
Research has already shown chitosan-based coatings and films can extend shelf life and has the potential to protect against micro-organisms such as listeria.
The chitosan efficiency depended of the extrusion processing: better results are obtained with simple extrusion compared to co-extrusion processing.
“The weak antimicrobial activity of blends performed by co-extrusion could be due to the migration of PCL into the surface during the extrusion processing…” said the researchers.
Further work is ongoing to boost the knowledge of the PCL migration and permeation measurements in terms of oxygen and carbon dioxide and water transport through the film.
Source: European Polymer Journal
“Active pseudo-multilayered films from polycaprolactone and starch based matrix for food-packaging applications”
Authors: Sébastien Alix, Angélique Mahieu, Caroline Terrie, Jérémie Soulestin, Eloïse Gerault, Marc G.J. Feuilloley, Richard Gattin, Vincent Edon, Tarik Ait-Younes and Nathalie Leblanc