TESIS

1. Original article
Improvement of active chitosan film properties with rosemary
essential oil for food packaging
Mehdi Abdollahi,1
Masoud Rezaei,1
* & Gholamali Farzi2
1 Department of Seafood Science and Technology, Faculty of Marine Sciences, Tarbiat Modares University, P.O. Box 46414-356, Noor, Iran
2 Department of Material and Polymer Engineering, Faculty of Engineering, Sabzevar Tarbiat Moallem University, Sabzevar, Iran
(Received 21 July 2011; Accepted in revised form 11 November 2011)
Summary Rosemary essential oil (REO) was used to develop an active film from chitosan. The effects of REO
concentration (0.5, 1.0 and 1.5% v ⁄ v) on film properties were studied by measuring the physical, mechanical
and optical properties of the REO-loaded films. Scanning electron microscopy and Fourier transform
infrared (FTIR) spectroscopy were used to study microstructure and the interaction of the chitosan-based
films. The solubility and water gain of the chitosan film decreased about 25% and 85%, respectively, by REO
incorporation, up to 1.5% v⁄ v, because of the interaction between hydrophilic groups of chitosan and REO
as confirmed by FTIR. It was determined that REO improved the transparency of the films from 4.97 in neat
chitosan up to 7.61; moreover, it reduced the films’ light transmission in UV light more than 25%. Films
containing REO showed more antibacterial activity and total phenol content. The films containing REO
showed potential to be used as active film in food preservation.
Keywords Chitosan film, film properties, food packaging, rosemary essential oil.
Introduction
Given the increased concerns about environmental
problems caused by synthetic packaging material, the
food industry has paid growing attention to biopolymer
and edible films during the last two decades. Chitosan,
the second most abundant polysaccharide after cellu-
lose, is a deacetylated derivative of chitin (Shahidi et al.,
1999; Srinivasa & Tharanathan, 2007). Its good film-
forming ability and intrinsic antimicrobial and antiox-
idant properties have made it attractive for active food
packaging. Nevertheless, its antimicrobial activity is just
as effectively expressed in aqueous systems (Wang,
1992), and it may become negligible when chitosan is
used as an insoluble film (Ouattara et al., 2000; Ziva-
novic et al., 2005). Moreover, its hydrophilic character
limits its application especially in the presence of water
and humid environments (Wang et al., 2005; Xu et al.,
2006).
To improve the shelf life of food products, researches
(Chan et al., 2007; Jongjareonrak et al., 2008; Siripatr-
awan & Harte, 2010) have focused on natural com-
pounds like plant extracts and essential oils as an
alternative for synthetic compounds. Among essential
oils, the preponderance of reports on effective antiox-
idant properties is directed toward extracts from plants
in the rosemary family, Rosmarinus officinalis L.
(Waszkowiak, 2008), and several studies showed that it
possesses the best antioxidant activity among the wide
range of herbs and spices tested (Baratta et al., 1998;
Bicchi et al., 2000; Wijeratne & Cuppett, 2007).
The latest studies demonstrated that some plant
extracts such as cinnamon (Ojagh et al., 2010), berga-
mot (Sánchez-González et al., 2010b), essential oils and
green tea extract (Siripatrawan & Harte, 2010) could
improve mechanical properties as well as the water
sensitivity of chitosan film. However, others like oreg-
ano (Zivanovic et al., 2005), thyme, clove (Hosseini
et al., 2009) and tea tree essential oil (Sánchez-González
et al., 2010a) had negative effects on the mechanical
properties of chitosan films. Although rosemary essen-
tial oil is considered to be one of the best known natural
antioxidants, no report discusses the effects of rosemary
essential oil (REO) on the chitosan film properties.
Thus, the aim of this study was to evaluate how
properties of chitosan-based films could be affected by
the incorporation of REO in different concentrations, as
an antioxidant and antimicrobial agent, through differ-
ent physical and structural properties analyses.
*Correspondent: Fax: +98 122 6253499;
e-mail: rezai_ma@modares.ac.ir
International Journal of Food Science and Technology 2012, 47, 847–853 847
doi:10.1111/j.1365-2621.2011.02917.x
2012 The Authors. International Journal of Food Science and Technology 2012 Institute of Food Science and Technology

2. Materials and methods
Materials
Crab shell chitosan (medium molecular weight, 75–85%
deacetylated) was obtained from Sigma-Aldrich
Chemical Co., USA Glacial acetic acid and Tween 80
were purchased from Merck, Germany. Rosemary
essential oil (extracted with hydrodistillation method)
was obtained from Barij Essence pharmaceutical Co.
(Kashan, Esfahan, Iran), Iran, and stored in dark
container at 4 C until using.
Sample preparation
Preparation of chitosan ⁄ rosemary solutions
Aqueous solution of chitosan was prepared by dissolv-
ing 20 g of chitosan powder in 1000 mL of aqueous
acetic acid solution (1%, v⁄v), using a magnetic stirring
plate at 90 C and 80 g for 20 min, and then cooled to
room temperature. Then, 0.2% (w⁄v) of Tween 80, as
an emulsifier, was added to the mixture and stirred in
40 C for 30 min. Finally, an appropriate amount of
REO was added to the solution, to reach a final
concentration of 0.5, 1.0 and 1.5% (v⁄v), and homog-
enised with Ultra Turrax (IKA T25-Digital Ultra
Turrax, Staufen, Germany) at 4000 g for 2 min. After
cooling the resultant mixture at room temperature, it
was degassed under vacuum for 5 min to remove all
bubbles.
Preparation of films
The chitosan⁄rosemary solutions (160 mL) were cast in
a simple cubic mould made from Teflon-coated steel
with dimension of 25.5 · 28.5 cm2
and then dried for
72 h at ambient conditions (25 C) to prepare the films.
Dried films were then peeled and stored in a desiccator
(containing saturated magnesium nitrate solution) at
25 C and 50% relative humidity until evaluation.
Sample characterisation
Microstructure analysis
Surface microstructure of the chitosan-based films was
examined with a Philips XL 30 scanning electron
microscope (Philips, Eindhoven, the Netherlands) under
high vacuum condition and at an accelerating voltage of
20.0 kV. The film samples were mounted on the
specimen holder with aluminium tape and then sput-
tered with gold in a BAL-TEC SCD 005 sputter coater
(BAL-TEC AG, Balzers, Liechtenstein).
Fourier transform infrared spectra
Fourier transform infrared (FTIR) spectra were col-
lected in transmission mode by using a Bruker (EQUI-
NOX 55, Ettlingen, Germany) FTIR spectrophotometer
with DTGS detector (16 scans) in the range of 400–
4000 cm)1
at a resolution of 4 cm)1
.
Measurement of film thickness
The thickness of the samples was determined with
a manual digital micrometer (0.001 mm, Mitutoyo,
Mizonokuchi, Japan). Measurements were repeated in
ten different regions of each sample. Average values
were calculated and used in water vapour permeability
(WVP), tensile and optical properties calculations.
Determination of moisture content
Film samples (0.1 g) were weighed and dried at 105 C
in an oven for 24 h. Moisture content was determined as
a percentage of the initial film weight lost during drying
and was reported on a wet basis.
Evaluation of film solubility in water
The initial dry matter of samples (4 · 4 cm) was
determined by drying films at 105 C for 24 h. The
films were then immersed in 50 mL distilled water and
then placed in a shaker incubator at 25 C and stirred
for 24 h at 250 rpm. The samples were then filtered
through Whatman No. 1 filter paper. Papers containing
any insolubilised film were dried at 105 C for 24 h. The
film solubility (%) was calculated using the following
equation:
Solubility in water ð%Þ
¼ ðInitial dry weight Final dry weightÞ
100=Initial dry weight
Calculation of water vapour permeability
The WVP of the films was measured gravimetrically
according to the method as described by Casariego
et al., 2009. The test film was sealed on the top of a glass
permeation cell. The cell contained distilled water
(100% RH; 2.337 · 103
Pa vapour pressure at 20 C),
placed in a desiccators. It was maintained at 20 C and
0% RH (0 Pa water vapour pressure) with silica gel.
Weight loss of the permeation cell was determined at
intervals of 2 h for 10 h. It showed that the water
transferred through the film and was adsorbed by the
desiccant. The slope of weight loss vs. time was obtained
by linear regression. The WVP was then calculated as
follows:
WVP = (WVTR LÞ=DP
where WVTR [water vapour transmission rate
(g m)2
s)1
)] is the measured slope, L is the mean film
thickness (m), and DP is the partial water vapour
Chitosan film properties with rosemary essential oil M. Abdollahi et al.
848
International Journal of Food Science and Technology 2012 2012 The Authors
International Journal of Food Science and Technology 2012 Institute of Food Science and Technology

3. pressure difference (Pa) between the two sides of the
film. This test was repeated three times for each
specimen to confirm its repeatability.
Water sorption kinetics
The water sorption kinetic of the REO-containing
chitosan films was evaluated by determining their water
sorption according to the method explained by Lavor-
gna et al., 2010. The samples were cut into small pieces
(2 · 2 cm), desiccated overnight and weighed to deter-
mine their dry mass. The weighed samples were placed
in closed beakers containing 30 mL of water (pH = 7)
and stored at T = 25 C. The kinetic of swelling was
evaluated by periodically measuring the weight incre-
ment of the samples. The films’ wet surface was gently
blotted with a tissue before weighing with a balance
accurate to 0.0001 g. The weighing was continued until
equilibrium state. The procedure was repeated three
times for each sample to confirm the repeatability. The
water gain of each sample was calculated as follows:
Water gain (% )
¼ (Weight of wet film - Weight of dry film)
100=Weight of wet film
Mechanical properties
Tensile strength (TS) and elongation at break (E%) of
the film samples were determined according to the
ASTM standard method D 882–02 (ASTM, 2002). with
an Instron Universal Testing Machine (model 200;
Hiwa, Tehran, Iran). The film samples were cut in
rectangular specimens (2.54 · 10 cm). Initial grip sepa-
ration was set at 50 mm, and cross-head speed was set at
50 mm min)1
. This test was repeated five times for each
specimen to confirm its repeatability.
Light transmission and film transparency
Transition and transparency of the chitosan-based film
were evaluated according to the method of Norajit
et al., 2010. Rectangle cut samples (5 · 50 mm) were
placed in a spectrophotometer cell. The light barrier
properties of the film samples were measured by
scanning the samples at wavelengths between 200 and
800 nm using a UV spectrophotometer. This test was
repeated three times for each specimen.
The transparency was calculated using the following
equation:
Transparency = Abs600/FT
Where Abs600 is a value of absorbance at 600 nm and
FT is the film thickness (mm).
Antibacterial activity
Antibacterial properties of REO, film-forming solution
and discs were studied using the agar diffusion method.
Five different pathogenic and spoilage bacteria includ-
ing Listeria monocytogenes (PTCC 1163), Pseudomonas
putida (PTTC 1694), Streptococcus agalactiae (PTCC
1768), Escherichia coli (PTCC 1533) and Lactococcus
lactis (PTCC 1336) were used for testing. Bacterial
strains were cultured overnight in Brain Heart Infusion
Broth at 37 C; 30 lL of REO and different film-
forming solutions was poured into Mueller Hinton agar
wells (5 mm diameter), after their plates had been seeded
with 0.1 mL of inoculums containing approximately
106
–107
CFU mL)1
of the indicated bacteria. In the
same way, films were punched into discs of 6 mm
diameter and then placed on the plates. Next, the plates
were incubated in chamber at 37 C for 24 h, and
afterwards, the zone of inhibition was measured and was
used to evaluate the antimicrobial potential of the
essential oil and the films.
Total phenolic assay
Total phenolic content of the films was studied using the
Folin–Ciocalteu method as described by Siripatrawan
Harte (2010) with some modification; 50 mg of each film
sample was dissolved in 3 mL of methanol, and 0.1 mL
of film extract solution was mixed with 7 mL distilled
water and 0.5 mL of Folin–Ciocalteu reagent (Merck
Company, Darmstadt, Germany). After preserving the
mixture for 8 min at room temperature, 1.5 mL of
sodium carbonate solution and 0.9 mL of distilled water
were added to it. The mixture was stored in darkness
and at room temperature for 2 h. The absorbance values
were then measured at 765 nm using a spectrophotom-
eter. A calibration curve was drawn using gallic acid in
specific concentrations, and the total phenolic content of
the films was expressed as gallic acid equivalents. A
standard curve was obtained with the following equa-
tion:
Absorbance ¼ 0:0011 gallic acid (mg) þ 0:029
This test was repeated five times for each specimen,
and the gallic acid equivalent value was reported as
mean ± SD of triplicate.
Statistical analysis
The difference between factors and levels was evaluated
by the analysis of variance (anova). Duncan’s multiple
range tests were used to compare the means to identify
which groups were significantly different from other
groups (P 0.05). All data are presented as mean ±
SD.
Chitosan film properties with rosemary essential oil M. Abdollahi et al. 849
2012 The Authors International Journal of Food Science and Technology 2012
International Journal of Food Science and Technology 2012 Institute of Food Science and Technology

4. Results and discussion
Microstructural studies
Microstructure of chitosan-based films was studied with
the scanning electron microscope (SEM), and Fig. S1
shows micrographs of the surface of the films. Neat
chitosan film had a smooth, homogenous and compact
surface without cracks (Fig. S1a). The same structure
has been reported for chitosan film by several authors
(Vargas et al., 2009; Zhao et al., 2009; Ojagh et al.,
2010; Sánchez-González et al., 2010a). Nevertheless,
chitosan film containing REO showed a not homoge-
nous and cracked surface in comparison with neat
chitosan film (Fig. S1b). These results are in accordance
with the results of other investigators. Hosseini et al.
(2009) showed that incorporation of thyme and clove
essential oils caused a cracked and loose structure in
chitosan film. We are going to discuss this phenomenon
with further characterisation of REO-containing chito-
san film with FTIR.
Fourier transform infrared spectra of chitosan-based
films were studied to understand the interaction of REO
with functional groups of chitosan, as presented in
Fig. S2. The peaks between 3500 and 3000 cm)1
corre-
spond to the stretching vibration of free hydroxyl and to
the asymmetric and symmetric stretching of the N–H
bonds in the amino group (Siripatrawan Harte, 2010),
respectively. These are stronger in neat chitosan film
compared to those incorporated with REO. The bands
appearing between 2750 and 3000 in the spectrum of
chitosan film occur because of stretching vibrations of
the C–H bond in –CH2 (m = 2930 cm)1
) and –CH3
(m = 2870 cm)1
) groups, respectively (Paluszkiewicz
et al., 2010). In addition, two strong bands at 1541
and 1403 cm)1
, associated with –OH in-plane bending,
are less discernible in the films incorporated with REO.
These peaks became more flattened when incorporating
REO. These may be due to hydrogen bonding between
the –OH group in functional groups in REO ingredients
and the -NH and –OH groups in chitosan (Wang et al.,
2008). In general, this observation leads to an assump-
tion that there could be a particular arrangement in the
films because of the interactions of the REO ingredients’
functional groups with hydroxyl and amino groups in
chitosan matrix.
Physical properties of films
The moisture content of chitosan-based films was eval-
uated according to described method and the results
showed in Fig. S3a. The figure shows that the moisture
content of chitosan film increased significantly by 0.5%
REO incorporation in low level and then it become a
constant at higher concentration of REO. The same
results were reported about the effect of thyme and clove
on moisture content of chitosan film (Hosseini et al.,
2009). The increase in moisture content in the presence of
REO at low concentrations may be related to the break-
up of the film network, as showed by SEM micrographs,
which caused an increasing amount of water molecules
between polymer chains. As explained before, the
moisture content did not increase by addition of REO
at a higher level. This phenomenon may be related to the
hydrophobic nature of REO that consequently increased
the hydrophobicity of chitosan-based films.
Solubility could be an important characteristic for
biodegradable films because it can affect resistance of
film to water, especially in humid environments (Bour-
toom Chinnan, 2008). On the other hand, it can
determine the release of antioxidant and antimicrobial
compounds from film when placed over the food surface
(Gómez-Estaca et al., 2010). Solubility of chitosan-
based films is shown in Fig. S3b. As can be seen in the
figure, the solubility of chitosan film decreased about
25% with an additional amount of REO, up to 1.5%.
This coincides with the results of Ojagh et al. (2010),
who incorporated cinnamon essential oil into chitosan
film. This fact may contribute to cross-linking effects of
REO components leading to esters and⁄or amide groups
of chitosan. Higher cross-linking in chitosan leads to a
matrix with low affinity to water. This was supported by
FTIR spectra that showed the interaction of chitosan
functional groups with REO. Lower solubility means
that chitosan⁄REO film can release REO oil slowly and
maintain it for a long time on a food surface.
Water sorption kinetics is a means to characterise the
water absorption of the film, which in turn is transmit-
ted to the product inside. Knowledge of sorption
kinetics is also important for predicting stability and
quality changes during packaging and storage of food
products (Srinivasa et al., 2007). Figure S3(c) shows the
water sorption kinetics of chitosan-based films. Neat
chitosan film absorbed a large amount of water (about
1400%) in the initial minutes and crumbled completely
before reaching equilibrium. But films containing REO
absorbed a several times lower amount of water and
could reach equilibrium. In other words, films became
more hydrophobic by adding REO, and the amount of
sorbed water decreased by increasing REO content
1.5%, up to 200%. This agreed with the results of other
research that incorporated natural antioxidant into
biopolymers (Vargas et al., 2009; Mayachiew
Devahastin, 2010; Pereda et al., 2010). This lower water
sorption at first may be due to the hydrophobic nature
of REO. Moreover, the degree of swelling of a polymeric
matrix strongly depends on the amount and nature of
intermolecular chain interactions (Di Pierro et al., 2006;
Mayachiew Devahastin, 2010). The hydrogen
and covalent interactions between a chitosan network
and REO ingredients limit the availability of hydro-
gen groups to form hydrophilic bonds with water,
Chitosan film properties with rosemary essential oil M. Abdollahi et al.
850
International Journal of Food Science and Technology 2012 2012 The Authors
International Journal of Food Science and Technology 2012 Institute of Food Science and Technology

5. subsequently leading to a decrease in the affinity of
chitosan film to water (Siripatrawan Harte, 2010), and
made the films more hydrophobic. This hypothesis was
supported by FTIR spectra in which the interaction of
chitosan functional, hydroxyl and amide groups with
REO is shown.
Water vapour permeability of chitosan-based films
was reported in Table S1. Neat chitosan film had a
WVP of about 0.70 (g msPa)1
) 10-10, but the highest
WVP was observed in chitosan film containing 0.5%
(v⁄v) REO, which was 14% higher than neat chitosan
film. This enhancement in water passing through the
film could be related to the cracked structure that is
caused by REO. Regarding moisture content, this
structure has increased the amount of free room in the
polymer network for water molecules that finally could
transmit through the film. However, water vapour
transition through the free rooms was reduced when
chitosan films incorporated with REO at a level of 1 and
1.5% v⁄v. Water vapour transfer could generally occur
through the hydrophilic portion of the film and depends
on the hydrophilic–hydrophobic ratio of the film com-
ponents (Norajit et al., 2010). Thus, the negative effect
of cracked structure was covered with increasing
hydrophobicity of the film at higher REO ratio.
Mechanical properties of films
The influence of REO on the mechanical properties of
chitosan film is shown in Table S1, which shows the
tensile strength (TS) and per cent elongation (E%) of the
films. The incorporation of REO leads to softer and
more flexible film, but no significant (P 0.05) differ-
ences were found between the mechanical parameters of
chitosan-based films. In general, TS and E% increased
about 7% and 40%, respectively, by REO incorporation
into the neat chitosan film. This may be explained by the
twosome function of REO incorporation. From one
standpoint, it caused some interaction in polymer chain
as showed in FTIR spectra, which can improve the
interchain forces in the chitosan matrix. On the other
hand, it caused a cracked structure that can negatively
affect TS. The improvements in E% may have resulted
from the increase in moisture content, as a good known
plastisizer. In general, different essential oils have shown
different effects on mechanical properties of chitosan
film. Thyme and clove decreased TS, but they improved
E% (Hosseini et al., 2009), and cinnamon improved TS
but decreased the E% of chitosan films (Ojagh et al.,
2010). Sánchez-González et al. (2010b) showed that
bergamot essential oil decreased the TS and E% of
chitosan film. On the other hand, Zivanovic et al. (2005)
also found that TS decreased when introducing some
essential oils into chitosan films, but no changes in E%
were found. These differences in essential oils’ behaviour
may be attributed to the type of chitosan (solvent and
molecular weight) used and the particular interactions
with the essential oil components which, in turn, are
affected by relative humidity, the presence of surfactants,
temperature, etc. (Sánchez-González et al., 2010a).
Optical properties of films
The transparency of film is important in that it can
directly affect the appearance of coated products in the
packaging industry (Chen et al., 2010). On the other
hand, it can affect the rate of oxidation of lipids, and
consequently food quality (Rao et al., 2010). Table S2
shows the results of spectroscopic scanning of chitosan-
based films in wavelengths between 200 and 800 nm.
Films containing REO showed lower light transmission
in UV light between 200 and 280 nm. These results were
in agreement with those of Norajit et al. (2010) for
adding ginseng extract to alginate film and of Gómez-
Guillén et al. (2007) who incorporated murta extract
into tunafish skin gelatin film. It was observed that
murta–gelatin films showed higher UV absorbance
levels than the control gelatin film. As explained before,
this decrease in transmission can be beneficial for food
preservation in that the most pronounced deleterious
effects of light on food are caused by ultraviolet light.
These results suggest that chitosan films containing
REO can potentially retard lipid oxidation induced by
UV light in food products.
Rosemary essential oil incorporation increased the
transparency of the chitosan film, and the transpar-
ency of film containing 1.5% REO was significantly
(P 0.05) higher than that of neat chitosan film. It
coincides with the results of some other studies that
added guar gum to chitosan film (Rao et al., 2010) and
ginseng extract to alginate film (Norajit et al., 2010). As
the films’ transparency depends on their internal struc-
ture (Sánchez-González et al., 2010a), the increase in the
transparency of chitosan films by REO may contribute
to the interaction of REO with the reflective index of
chitosan, which affects film transparency (Rao et al.,
2010). These findings could be useful in chitosan film
applications, particularly if they were used for coating
and packaging the food product, in that it can affect the
consumer acceptability.
Antibacterial and antioxidant activity
Antibacterial activity of REO, film-forming solutions
and film discs is shown in Table S3. Regarding their
extra protective outer membrane, gram-negative bacte-
ria are usually considerably more resistant to antibac-
terial agents than their gram-positive counterparts. In
this regard, the essential oil showed its best antibacterial
activity in the disc diffusion test on gram-positive
bacteria (i.e. L. monocytogenes, S. agalactiae). The results
are in agreement with the results of other published data
Chitosan film properties with rosemary essential oil M. Abdollahi et al. 851
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6. (Bozin et al., 2007). However, its inhibitory activity on
gram-negative bacteria (especially on E. coli) was also
notable and interesting. Bozin et al. (2007) also reported
good inhibitory activity for REO against E. coli strain.
As explained before, high antimicrobial properties are
mainly related to phenol diterpenes, such as carnosic
acid, carnosol, rosmanol, isorosmanol and rosmarinic
acid (Bozin et al., 2007; Türe et al., 2008).
Ponce et al. (2008) studied antibacterial activity of
acidic water, and the bacteria were not sensitive to the
solution. The results can coincide with our results about
chitosan film solution containing acetic acid 1%. Neat
chitosan did show antimicrobial properties neither in
solution form nor in the film form. These results coincide
with the results of Ojagh et al. (2010) and Zivanovic
et al. (2005) about chitosan film. This effect of chitosan
may be related to the fact that chitosan does not diffuse
through the adjacent agar media in the agar diffusion test
method, so that only organisms in direct contact with the
active sites of chitosan are inhibited (Coma et al., 2002).
Incorporation of REO into chitosan showed antibacte-
rial activity in higher than 1% REO in the film-forming
solution and film discs. Moreover, REO showed less
antibacterial activity in film-forming solution and film
disc, respectively, in comparison with pure essential oil.
The possible reason for the decrease in activity of the EO
incorporated in the chitosan films compared with activity
of pure EO may be due to lower amount of the EO in the
film solution and film discs in comparison with the well
test for pure EO. The other reason may be due to
slower⁄controlled release of active compounds from the
chitosan film than from well.
Total phenolic content of chitosan-based films is
shown in Fig. S4. Folin–Ciocalteu phenol reagent was
used to obtain a crude estimate of the amount of
phenolic groups present in the films. As expected, total
phenol content of chitosan film increased significantly
by incorporating REO, which was in agreement with
other reported results (Gómez-Estaca et al., 2010;
Norajit et al., 2010; Siripatrawan Harte, 2010). In
general, it has been demonstrated in many studies over
recent years that the antioxidant activity of plants is
caused mainly by phenolic compounds. The effect of
phenolic compounds on lipid molecules may depend on
structural factors, such as the number of phenolic
hydroxyl or methoxyl groups, flavone hydroxyl, keto
groups, free carboxylic groups and other structural
features (Jayabalan et al., 2008; Norajit et al., 2010).
Conclusions
Rosemary essential oil was successfully incorporated
into chitosan film, and it was shown that REO, one of
the best natural antioxidants, could notably improve the
water sensitiveness of chitosan film. FTIR spectra
confirmed that this improvement is related to the
interaction between hydrophilic groups of chitosan
incorporating REO. The WVP of chitosan film in-
creased by REO incorporation because of the cracked
structure caused by REO as confirmed by SEM. REO
made the chitosan films more flexible and increased the
transparency of films; moreover, it reduced films’ light
transmission in UV light, which can be desirable for the
food-packaging industry. More research for understand-
ing the antioxidant and antimicrobial behaviour of
chitosan film containing REO in an actual food envi-
ronment is needed.
Acknowledgment
We are grateful to Dr Badiei for preparing some
experimental facilities for this research work.
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Supporting Information
Additional Supporting Information may be found in the
online version of this article:
Figure S1. Scanning electron microscope microstruc-
ture of chitosan (a) and chitosan–rosemary 1.0% (b)
film.
Figure S2. Fourier transform infrared spectra of
chitosan film without rosemary essential oil (REO)
and films containing 1.0% REO.
Figure S3. Moisture content (a), solubility (b) and
water gain of chitosan-based films.
Figure S4. Total phenol content of chitosan-based
films.
Table S1. Antibacterial activity of rosemary essential
oil (REO), film-forming solutions (FFS) and film discs.
Table S2. Light transmission (T%) and transparency
of chitosan films containing rosemary essential oil
(REO).
Table S3. Summary of mechanical properties and
WVP chitosan-based films.
Please note: Wiley-Blackwell are not responsible for
the content or functionality of any supporting materials
supplied by the authors. Any queries (other than missing
material) should be directed to the corresponding author
for the article.
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