Color and transparency of packaging films are important in
terms of general appearance, consumer acceptance and utilization.
Fig. 2A shows that L* values of TPS/CTS films were lower than that of
TPS film; also, the L* values of TPS/CTS films significantly decreased
with increasing chitosan concentration. This resultimplied thatthe
presence of chitosan caused a darker film. TPS film showed slightly
increased a* value and markedly increased b* value when chitosan
was incorporated. However, the film color was still a red/yellow
shade, since a* and b* values were positive. The values of a* and b* of
TPS/CTS films tended to increase with increasing chitosan content;
this was reflected by the films becoming a darker yellow.
UV absorption of the films was measured at a wavelength range
from 200 nm to 400 nm. TPS/CTS films showed higher UV absorption
than TPS film, and UVabsorption ofthe TPS/CTS films increased
with increasing chitosan content(Fig. 2B). The result suggested that
chitosan could impart UV light protection to TPS film; this might
be useful for retarding lipid oxidation induced by UV light. Bonilla
et al. (2013) also reported that PLA/CTS films showed better barrier
properties against UV light than naked PLA film.
Transparency of the films was determined from light transmission
at selected wavelengths from 400 nm to 800 nm. The
transmittance values of all samples increased with increasing
wavelength (Fig. 2C). TPS/CTS films showed lower light transmittance
values than TPS film, corresponding to the abovementioned
opacity (Fig. 1A). Higher chitosan contents gave the films greater
opacity, due to the highly dispersed chitosan in the TPS/CTS matrix