Development of starch/chitosan nanoparticle nanocomposite films with antibacterial properties
The application of biopolymers as food packaging material are limited due to the poor desired properties. Incorporation of chitosan nanoparticle (CNP) into biopolymer films can improve the desired properties of the films which include mechanical, thermal, barrier, and antibacterial properties....
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Main Author: | |
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Format: | Thesis |
Language: | English |
Published: |
2018
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Subjects: | |
Online Access: | http://psasir.upm.edu.my/id/eprint/75427/1/FK%202018%20114%20-%20IR.pdf |
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Summary: | The application of biopolymers as food packaging material are limited due to the poor
desired properties. Incorporation of chitosan nanoparticle (CNP) into biopolymer films
can improve the desired properties of the films which include mechanical, thermal,
barrier, and antibacterial properties. Thus, this work is directed towards developing
starch/CNP films with improved properties. CNP was first synthesized using different
concentrations of chitosan 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, and 2.1% w/v) and the average
particle size of CNP was measured via DLS and TEM. DLS analysis revealed that the
particle size of CNP increased from 46.76 to 225.33 nm (4-fold increment) with the
increase in initial concentration of chitosan. The average particle size of 0.9% w/v
CNP measured via DLS was 106.34 nm while that measured via TEM analysis was
53.93 nm. Note that, TEM provides the actual size of CNP in dehydrated state whereas
DLS provide hydrodynamic size in hydrated state hence TEM was more accurate to
measure the size of the produced CNP. Starch/CNP films were produced using solution
casting method with varying concentration of CNP (5, 10, 15, 20, 25, 30, 35% w/w of
solid starch). The mechanical, thermal, barrier, and optical properties of the
starch/CNP films (average thickness: 0.07 mm) were characterized. Addition of
15% w/w CNP into starch films improved the tensile strength from 1.12 to 10.03 MPa
(7.96-fold increment) and elongation at break from 67 to 90.77% (0.35-fold
increment). This was due to the good interfacial interaction formed between starch and
CNP thus produced a compact and rigid structure of the film. Improvement in the
structure of the films led to the enhancement in the thermal stability of the film
whereby residue of starch film increased from 7.91% to 23.48% (2-fold increment).
Furthermore, reduction in the water vapor permeability from 1.1 x 10-11 g/Pa h m to
0.63 x 10-11 g/Pa h m (4-fold increment) and oxygen permeability from 7.38 x 10-3
cm3/Pa.day.m to 3.59 x 10-3 cm3/m.day.Pa (0.51-fold increment) of the film was
observed. Meanwhile, addition of CNP slightly increased the opacity of 15% w/w
starch/CNP films from 8.07 to 14.67 due to the presence of CNP within the starch
matrix that hinder the light transmission pass through the film. The antibacterial
properties of starch/CNP films were evaluated via disc-diffusion analysis to observe
the inhibition zone of the films. Starch/CNP films incorporated with 15% and 20%
w/w CNP exhibited clearer inhibitory zone for gram-positive bacteria (B. cereus, S.aureus) compared to gram-negative bacteria (E. coli, S. typhi). The application of
starch/CNP films was demonstrated on the cherry tomatoes whereby the microbial
growth in cherry tomatoes was evaluated during 10 days storage period. It was found
that the 15% w/w starch/CNP film was more efficient to inhibit the microbial growth
in cherry tomatoes (7 x 102 cfu/mL) compared to starch film (2.15 x 103 cfu/mL), thus
confirmed the antibacterial properties of the starch/CNP film. In conclusion,
starch/CNP film developed in this study exhibit improved properties and has the
potential to be used as food packaging material. |
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