Vol.3, No.1B, 5-10 (2014) Journal of Agricultural Chemistry and Environment
http://dx.doi.org/10.4236/jacen.2014.31B002
Development of t e mperature indicat or pro t otype:
Cardpaper coated with chitosan intelligent films
Vinicius B. V. Maciel1*, Cristiana M. P. Yoshida2, Telma T. Franco1
1Department of Chemical Engineering, State University of Campinas, Campinas, Brazil;
*Corresponding Author:
2Department of Exact and Earth Sciences, Federal University of Campinas, Diadema, Brazil
Received October 2013
ABSTRACT
An intelligent and biodegradable material pack-
aging was developed based on a natural and
thermal-sensitive pigment. Anthocyanin (ATH,
0.50 g/100g) was incorporated into chitosan
matrix films (2 g/100g) forming a chitosan intel-
ligent film (C-ATH). The system is able to indi-
cate the variation of temperature during distri-
bution and storage chain of industrial products.
The novelty of this work was an alternativ e pack-
aging material that it is biodegradable and could
inform any temperature variations on the range
of 40˚C - 70˚C, by irreversible visual colour
changes. The effects of temperature (10˚C, 30˚C
and 50˚C) and luminosity (0, 500 and 1000 l×)
were analyzed on C-ATH using an experimental
design of 2 variables, measuring the colour pa-
rameters (L*, a*, b*) and mechanical properties
(tensile strength, elongation break and Young’s
modulus) as responses. C-ATH suspensions
were applied as a coating on cardpaper surface
forming a temperature indicator prototype (TIP).
C-ATH darkened after being exposed to temper-
atures above 50˚C and luminosity of 1000 lx for
72 hours. TIP was obtained, without bubbles or
defects, with reduced water absorption capacity.
Irreversible visual colour change was verified on
TIP exposed at 40˚C independently of luminosity,
turned gradually yellow. Chitosan suspensions
containing ATH and applied as a coated on card
paper sheets could be an alternative of biode-
gradable material for packaging system that in-
dicates efficiently temperature changes. This in-
dicator system has potential application tem-
perature range of 40˚C to 70˚C, such as food,
pharmaceuticals, biological, agricultural and
others products, that are highly dependent of
storage temperature conditi ons.
KEYWORDS
Chitosan; Anthocyanin; Temperature Indicator;
Coating; Card Paper
1. INTRODUCTION
The natural polymer films application in the packaging
sector has been investigated due to their biodegradability
and ability to retard the transport of moisture, gas, fla-
vour and lipids. Films based on natural macromolecules,
have been described in literature; however, industrial ap-
plications are still scarce. Among the natural polymers,
chitosan forms resistant films with an efficient oxygen
barrier [1,2].
Intelligent packaging is designed to monitor and com-
municate information about packed product quality and
safety. Examples include time-temperature indicators,
ripeness indicators, biosensors, radio frequency identifi-
cation, etc. Colourimetric indicators can detect and moni-
tor changes in the conditions of packed products [3] by
visual colour variations .
Temperatur e greatly affects the quality and safety of
thermal-sensitive products such as food, drugs and bio-
logical compounds. Variations in temperature conditions
could promote undesirable physical and chemical dete-
riorations [4]. Time-temperatur e indicato rs (TTIs) are d e -
fined as simple, cost-effective and user-friendly devices
to monitor, record and cumulatively indicate the overall
influence of temperature traceability on the quality of the
food product from the manufacturer to the consumer [5].
TTIs could be present as small self-adhesive labels that
provide visual indications of temperature history during
distribution and storage [6]. New types of TTIs have re-
cently been studied; one example is a system based on
the growth and metabolic activ ity of a strain of Lactoba-
cillus sakei, which monitored food quality throughout the
chilled-food chain [7]. Yan et al. [8] developed a new
amyl a s e -type TTI based on the reaction between amylase
and starch solution, changing the colour from blue to

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6
yellow after temperature exposure from 4˚C to 37˚C.
Kato, Yoshida, Reis, Melo and Franco [9] developed a
fast and colorimetric indicator system by combining chi-
tosan as a three-dimensional biopolymer matrix and ferr-
ous sulfate (FeSO4) as a colorimetric indicator of hydro-
gen sulfide (H2S) gas. Maciel, Yoshida and Franco [10]
developed an intelligent and biodegradable temperature
indicator packaging material based on a natural and heat-
sensitive pigment and chitosan solution dispersing on
card paper.
In this study, the objective was to develop an intelli-
gent and biodegradable alternative packaging material
based on a natural polymer, chitosan, and thermal-sensi-
tive pigment (anthocyanin, ATH) that visually change the
colour after temperature exposition in a specific range.
The efficiency response of this system was analysed by
the changes in colour parameters. The mechanical prop-
erties were measured.
2. MAT ERIALS AND METHODS
2.1. Materials
Chitosan (Primex, Iceland; d egree of acetylation (DA)
of 18% and molecular weight (Mw) of 238,000 g∙mol−1),
acetic acid (Synth, Brazil), anthocyanin (Christian Hansen,
Brazil ) and card paper tri plex TP 250 g∙m−2 ( Suzano Pa pel
e Celulose Ltd., Brazil) were used.
2.2. Chitosan Intelligent Films (C-ATH)
Film suspensions were pr epared by dispe rs ing chitosa n
(2.00 g/100g) in aqueous acetic acid [10]. The stoichio-
metric amount of acetic acid was calculated from sample
weight, taki ng int o acco unt t he val ue of DA to ac hieve the
protonation of all the NH2 sites [2] . T he sus pensi ons we re
homogenized by magnetic stirring at room temperature
for 45 minutes. The ATH (0.50 g/100g) was added to the
filmogenic suspension and homogenized. Aliquots of 9.0
mL were poured into Petri dishes (9.5 cm) and dried at
room t emperature for 36 hours a nd then ke pt at 28 ˚C in an
incubator with forced air circulation for 24 hours. As the
mass suspension used to cast the C-ATH was kept con-
stant, the total solid content per gram of dried films was
28.2 g∙m−2.
2.2.1. Experimental Design
The experimental design was applied to study the tem-
perature and luminosity effects on the colour of C-ATH
(Table 1). The luminosity range was from dark exposure
(0 l×) to simulation of supermarket light (1000 l×). The
time of exposure to temperature and luminosity condi-
tions established was 72 hours.
2.2.2. Mechanical Properties
Tensile strength (TS), elongation at break (ε) and
Tabl e 1 . Values range used in experimental design of two va-
riables.
Variables −1 0 +1
Temperature (oC) 10 30 50
Luminosity (lx) 0 500 1000
Young’s Modulus (E) were determined on C-ATH based
on ASTM Standard method D882 [11]. Films were cut
into 25.4 × 100.0 mm strips and preconditioned at 50%
relative humidity (RH) and 25˚C ± 2˚C for 48 hours.
Measurements were made using a TA.XT2 texture ana-
lyzer (Stable Micro Systems, Godalming, UK). The ini-
tial grip separation was set at 50 mm and crosshead
speed at 1 mm∙s−2. There were at least ten replicates per
experiment. F ilm thickness was measured using a micro-
meter (Mitutoyo Mfg Co. Ltd., Japan) and measurements
were taken at five random positions on the film, using
the average values to calculate film properties.
2.2.3. Scanning Electron Microscopy (SEM)
SEM analysis was performed on fractured cross-sec-
tions and the surface of gold-sputtered C-ATH films us-
ing a LEO 440i scanning electron microscope (LEO
Electron Microscopy Ltda., England), operating at 10 kV
and 100 pA [10]. Chitosan films (CF) without anthocya-
nin was studied as reference.
2.3. Temperature Indicator Prototype (TIP)
Sheets of card paper (0.045 m2) were coated with C-
ATH suspensions. The C-ATH suspension was spread on
the card paper surface using 80 µm wire bar coater (TKB
Erichsen, Brazil). The coated paper sheets were dried in
an oven at 1 50 ˚C for 90 s.
2.3.1. Water Absorption—Cobb Test
Water absorption capacity was determined in accor-
dance with standard ASTM D3285 [12]. T441om-90.27
The weight gain was measured using Mettler AE 163
analytical scales. The results are expressed in g m−2.
There were at least 15 replicates per experiment. Sam-
ples were preconditioned at 50 % RH and 25 °C for 48
hours in a desiccator.
2.3.2. Taber Stiffness
Taber stiffness was determined using standard method
ASTM D5342 [1 3]. Uncoated and coated cardpaper
sheets were cut into samples of 38 × 70 mm2 in the ma-
chine direction (MD) and the cross-machine direction
(CD) using a guillotine (Regmed, Brazil). Taber stiffness
was measured at an angle of 15˚ using Taber stiffness
equipment (model RI 5000, Regmed, Brazil). Results are
expressed in mN. There were at least 15 replicates per

V. B. V. Maciel et al. / Journal of Agricultural Chemistry and Environment 3 (2014) 5-10
7
experiment. Samples were preconditioned at 50% RH
and 25˚C for 48 hours in a desiccator.
2.4. Colour Response Efficiency
Measurement
The colour parameters (L*, a*, b*) of C-AT H a n d T I P
were measured at different periods of times after tem-
perature and luminosity exposition. A Chroma Meter CR
400 colourimeter (Konica Minolta, Japan) was used. The
parameter L* represents the lightness of colours from 0
(dark) to 100 (light), a* is a measure of gr eenness/redness
and b* is the grade of blueness/yellowness. Both a* and
b* scales range from −60 to +60. The transformation of
a* and b* into geometric values (hue angle – hab) for C-
ATH is a better predictor variable of sensory perception
in experimental design application. The hab (0˚ - 360˚)
was obtained by arctan b*/a* and was used to expres s the
characteristic/dominant colour [14]. According to several
authors [1 4,15] this conversion is necessary to obtain
results in the experimental design due to interaction be-
tween parameters a* and b*, where a change in one usu-
ally does not occur without changing the other. The C-
ATH was exposed to experimental design conditions and
the TIP was exposed to a range of temperatures (10˚C -
70˚C) and 0 and 1000 l×. There were three replicates per
experiments.
2.5. Statistical Analysis
Statistical analysis was carried out with the Statistic
version 7.0 program (Statistic Inc., USA) and differences
between the means were detected by the Tukey multiple
comparison test.
3. RESULTS AND DISCUSSIO N
Initially C-ATH was obtained to evaluate the colour
response efficiency of the system as temperature indica-
tor. Homogeneous, transparent, dark violet films were
obtained and following drying, were easily removed
from the support plates, forming a flexible and resistant
matrix.
3.1. Experimental Design
The colour parameters L* and hab of C-ATH were
characterized after 72 h under exposure to temperatures
and luminosities (Table 2).
The effects of temperature and luminosity on colour
variations of C-ATH were significant for a confidence
level of 90% for parameters L* and hab (Figure 1). The
initial purple colour of the films gradually turned dark.
Increasing the temperature from 10˚C to 50˚C, parame-
ters L* and hab increased to 5.02 and 3.40, respectively.
Although increasing the luminosity from 0 to 1000 l×, a
Table 2. Matrix of experimental design 22, colour parameters
and mechanicals properties of C-ATH films.
Tests
Independent Var iables Properties
Temperature Luminosity L* hab (˚) ε TS E
(˚C) (lx) (%) (MPa ) (GPa)
1 −1 (10) −1 (0) 45.52 274.13 3.21 60.71 3.12
2 +1 (50) −1 (0) 48.73 307.29 2.91 66.51 3.15
3 −1 (10) +1 (1000) 45.16 298.08 3.61 60.62 2.50
4 +1 (50) +1 ( 1 000 ) 45.85 323.19 3.38 50.04 2.71
5 0 (30) 0 (500) 45.77 312.29 2.56 67.64 3.14
6 0 (30) 0 (500) 45.70 311.45 2.53 67.67 3.14
7 0 (30) 0 (500) 46.09 312.01 2.56 67.63 3.14
(a)
(b)
Figure 1. Effect of temperature and luminosity on variat ions in
colour of C-ATH: (a) Parameter L* and (b) Parameter hab.
-3.25
-4.17
5.02
p=,1
T em perature by Luminosity
Lumi nosity
T emperature
-0.47
2.33
3.40
p=,1
T em perature by Luminosity
Luminosity
Temperature

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8
process of discolouration was observed with the reduc-
tion in L*. The combined temperature and luminosity
decreased the L* in 3.25 the C-ATH became lighter.
Shaked-Sachray, Weiss, Reuveni, Nissim-Levi and
Oren-Shamir [16] studie d th e co mbin ed effect of elevated
temperatures and metal concentrations on the accumula-
tion of ATH in aster flowers and observed that the an-
thocyanin degraded and became discoloured at higher
temperatures (higher than 30˚C). Significant changes in
b* values were also found by Alighourchi and Barzegar
[17] for anthocyanins in pasteurised pomegranate juice
stored at 4˚C, 20˚C and 37˚C for 210 days. In their study,
L*, a* and b* values decreased and the most significant
colour change was observed after storage at 20˚C and
37˚C. This change was attributed to the degradation of
anthocyanin. According to Lauro and Francis [18], the
anthocyanins could change with temperature, light, oxy-
gen, presence of sugars and enzyme, pH and presence of
proteins and metal ions [19-22], producing polymers
with decreased stability.
Temperature and luminosity had not affected ε and TS
significantly (Table 2). For E, only the luminosity had a
slightly significant effect (p ≤ 0.1). Increasing luminosity
from 0 to 1000 l×, E decreased in order to 19.9% at 10˚C
and 14.0% at 50˚C. These results are indicating that
flexibility and s trength of ATH-CF were maintained sim-
ilar to the initial condition.
The good mechanical properties of CF and ATH-CF
could be related with the microstructures (Figure 2). A
compact and cohesive structure without pores or cracks
was observed in CF (Figure 2(a)). No significant differ-
ence was observed between CF and ATH-CF structures
(Figure 2(b)). ATH was entrapped in the tridimensional
matrix forming a uniform structure films. Yoshida,
Oliveira-Junior and Franco [1] found similar results for
CF and CF with palmitic acid.
3.2. Film Card Paper System (TIP)
C-ATH suspensions were applied as a coating on card
paper surface forming TIP system. The TIP drying proc-
ess time was 90 s, which was faster than the total film dry-
ing process (60 h) that could be a commercial adv antage.
C-ATH suspensions formed a homogeneous card pa-
per coating without bubbles or defects. The systems were
submitted to different temperature and luminosity condi-
tions during 72 hours. An irreversible and gradual change
in colour exposition of the TIP was visually observed
after 72 hours at different temperature and luminosity
conditions (Figure 3 ). A more pronounced colour change
was observed after luminosity exposition. Studying the
colour stability of berry anthocyanin, Rein [19] found
that the exposition at higher luminosities accelerated
ATH discolouration. The parameter b* values increased
(a) (b)
Figure 2. SEM Micrographs for (a) CF, (b) C-ATH containing
0.25% ATH.
(a)
(b)
Figure 3. The visual and b* colour parameter changes on TIP
system exposed to different temperatures and luminosities: (A)
0 l× and (b) 1000 l×.
in TIP after 0 and 1000 l× exposition.
Colour change on the TIP could be associated with
ATH molecules chemical structure. Thermal degradation
can produce changes in ATH structures that depend on
the severity and heating conditions. The mechanisms of
ATH degradation are still relatively unknown. Chemical

V. B. V. Maciel et al. / Journal of Agricultural Chemistry and Environment 3 (2014) 5-10
9
structures and the presence of other organic acids have a
strong influence [22]. Markakis, Livingstone and Fillers
[23] suggested that the pyrylium ring of ATH opens,
forming a chalcone structure as a first degradation step.
Chalcone is derived from three acetates and one cin-
namic acid. It has a yellow pigmentation and is a pre-
cursor of the biosynthesis of flavonoid. Adams [24] re-
ported that ATH could decompose upon heating into a
chalcone structure and be further transformed into a cou-
marin glucoside derivative by the loss of the B-r ing.
The ATH discolouration was observed in blue flowers
[16], pomegranate juice [17], vegetables extracts [25]
and fruits purees [26] after exposure to temperatures
higher than 30˚C. The discolouration process is usually
accelerated with luminosity [23].
3.3. Properties of TIP
The grammage, water absorption capacity and Taber
stiffness results for uncoated and coated card paper are
shown in Table 2. The C-ATH coating did not signifi-
cantly change the grammage of card paper. Water resis-
tance is an important property which can determine the
behaviour of card paper in various applications. The wa-
ter absorption of the TIP decreased significantly applying
C-ATH coating.
According to Aider [27], chitosan films have the abil-
ity to avoid moisture loss or water absorption and could
act as a reinforcement layer. Bordenave, Grelier, Picha-
vant and Coma [28] studied the potentiality of bioactive
food packaging based on ch ito san -coated papers and
show that chitosan film improved the water absorption of
paper despite the very low amount of total solids. The
incorporation of chitosan as a papermaking additive in
paper and paperboard production or as a surface coating,
had previously been investigated [29-32]. Different con-
centrations of chitosan were app lied as a coating additive
in paper and paperboard making, and it was observed
that when increased chitosan concentration from 0.1 to
0.75% (w/w), the water absorption decreased significant-
ly [29]. The greaseproof paper coated with chitosan films
did not provide an extra barrier against water absorption
[30]. The Taber stiffness values were statistically differ-
ent when applied C-ATH coating on card paper surface
as compared to uncoated card paper (Table 3). The resis-
tance and flexiblility of C-ATH strengthened the cellu-
lose fiber interbonds. Chitosan films had a positive im-
pact on the mechanical properties of coated pap er [32 ].
4. CONCLUSION
An efficient and irreversible temperature indicator ma-
terial was obtained for a specific range (from 40˚C to
70˚C) using biodegradable materials (chitosan, card pa-
per and ATH). The TIP changed the colour from violet to
yellow after temperature exposition. Luminosity acceler-
Table 3. Grammage, Cobb Test and Taber stiffness of TIP [10].
Samples Grammage Water absorption
Taber Stiffness (mN.m)
(g∙m−2) (g∙m−2) CD MD
Uncoated
cardpaper 252.71 ± 1.88a
45.48 ± 1.76a 5.60 ± 0.16a 12.97 ± 0.21a
TIP system 253.17 ± 1.71a 35.41 ± 1.66b 6.43 ± 0.17b 14.15 ± 0.09b
a, b, cMeans in the same column with different superscripts differ signifi-
cantly (p ≤ 0.05) in accordance with Tukey’s test.
ated the ATH molecule degradation. The advantages of
this temperature indicator were the simple man ufacturing
process, use of natural compounds that are food safety
contact, the biodegradability and low cost. This ind icator
system has potential applications in different areas such
as food, pharmaceuticals, biological, agricultural and
others products, that are highly dependent of storage
temperature conditions.
ACKNOWLEDGEMENTS
The financial support of CNPq, FAPESP, CA PES and Suzano Papéis
e Celulose Ltd.
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