The films were processed in a pilot single screw extruder (BGM,
model EL-25, Brazil) equipped with a screw diameter (D) of 25mm
and a screw length of 28 D, four heating zones, and die with two
3 mm diameter holes for the production of pellets. For the production
of tubular films, the same extruder was used, with five heating
zones, 50 mm film-blowing die with internal air for the formation
of the film ‘‘bubble’’.
The components of the formulations (starch, chitosan and glycerol)
were mixed with a mixer (model Ciranda Classic, Arno, Brazil)
at the lowest speed (approximately 780 rpm) for 5 min. In the first
stage of the extrusion process, the mixtures were extruded and
pelletized twice to obtain good homogenization with a temperature
profile of 120/120/120/110 C and a screw speed of 35 rpm
(Fig. 1a). Next, the reprocessed pellets were used to manufacture
the film by blown extrusion with a temperature profile of
120/120/120/120/130 C and 35 rpm screw speed