Moisture Sorption and Isosteric Heat of Sorption properties of
PVP-CMC Hydrogel based Food Packaging Material
Nabanita Sahaa, Dipali S.Shindeb, Madhusweta Dasb, Petr Saha a
aCentre
of Polymer Systems, University Institute, Tomas Bata University in Zlin,
Tř. T. Bati 5678, Zlin 760 01, Czech Republic
bDepartment
of Agricultural and Food Engineering, Indian Institute of Technology,
Kharagpur-721302, India
* Contact email ID: nabanita@ft.utb.cz / madhu@agfe.iitkgp.ernet.in
Tuesday, August 11, 2015
Biopolymers and Bioplastics-2015
1
Outline
INTRODUCTION





Polymer in packaging
Hydrogel food packaging
Unique properties of hydrogel
Application of hydrogels
Preparation techniques of hydrogel
MOTIVATION OF RESEARCH
 EXPERIMEMTATION
RESULTS
Visual Images of PVP-CMC hydrogel food packaging material
AFM image of PVP-CMC hydrogel film
Water activity of PVP-CMC hydrogel at different temperature
Moisture sorption isotherm of PVP-CMC hydrogel film
Comparison of PVP-CMC hydrogel film at different temperature
Effect of temperature on moisture sorption isotherm
Isosteric heat of sorption of PVP-CMC hydrogel
CONCLUSION
Tuesday, August 11, 2015
Biopolymers and Bioplastics-2015
2
Introduction
Polymers in Packaging
Polymeric materials play a dominate role in
the food packaging industry
Tuesday, August 11, 2015
3
Introduction
4
Introduction
Lists of acceptable polymers
for use in food packaging
Table
no.
Global bioplastic packaging market
by product type, 2010 (%)
Tuesday, August 11, 2015
Polymer Type
Code
1
Polyethylenes
PE
2
Polypropylenes
PP
3
Poly(ethylene-vinyl acetates)
4
Polystryrenes
5
Polyvinylchlorides
6
Ionomers
7
Polyethylene terephthalates
PET
8
Polyvinyl acetate
PVAc
9
Polycarbonates
PC
10
Polyamides
PA
11
Polyvinylalcohols
PVOH
12
Polyvinylidene choliride
PVDC
13
Others
EVA
PS
PVC
I
O
5
Introduction
Hydrogel based food packaging
Crosslinking
network and pores
in hydrogel
Hydrogel
Hydrogels are one kind of bio-inspired materials and
devices for chemical and biological defense .
Porous internal morphology
 Quite a good moisture absorption capacity
Flexible in nature for the preparation of sample
in different shape, size and thickness
Tuesday, August 11, 2015
Introduction
 Hydrogels
provide
suitable
semiwet,
three-dimensional
environments for molecular-level biological interactions.
 Provide inert surfaces that prevent nonspecific adsorption of
proteins, a property known as antifouling
 Biological molecules can be covalently incorporated into hydrogel
structures using a range of well-established chemistries
 Hydrogels can be designed to change properties (e.g.
swelling/collapse or solution-to-gel transitions) in response to
externally applied triggers, such as temperature, ionic strength,
solvent polarity, electric/magnetic field, light, or small
(bio)molecules.
Tuesday, August 11, 2015
R.V.Ulijn., et al. Materialstoday, Vol 10, p-40-48, 2007
7
Methods for the preparation of hydrogel
Based on starting materials
• Monomers
• Prepolymers
• polymers
Irradiation Technique
X-ray
UV-ray
Gamma ray
Tuesday, August 11, 2015
Physical stimuli
• Heat
Pressure
pH
Ionic strength
• Hydrophobic interactions
Chemical stimuli
• Charge interactions
• Different chemical
• Hydrogen bonding
Crosslinking agents
• Stereo complexation
• Supramolecular chemistry
Experimental
Preparation of “PVP-CMC Hydrogel” for Food Packaging
Cooling in an
aseptic environment
Moist heat
Autoclave
Polymer
solution
Occurrence
of crosslinking
phenomena
Sterile
polymer
solution
Moulds with
polymer solution in
aseptic environment
3-dimensional
crosslinking network
developed
Hydrogel
Tuesday, August 11, 2015
SEM images of hydrogels: PVP/CMC (a.i) surface (a.ii) cross section
Tuesday, August 11, 2015
9
MOTIVATION OF RESEARCH
 It is known that macromolecular network determining the properties of biopolymer based
polymeric films where this macromolecular network is dependent on moisture content.
On the other hand, moisture sorption isotherm (MSI) provides information on the moisture
holding capacity of the films at variable relative humidity (water activity, aw).
Water activity (aw) is a measure of the energy status of the moisture content in a system, and
controls several properties of biopolymer based materials; high water activity leads to chemical
and microbial instability.
The equilibrium relationship between water activity (aw, ranging within 0.0-1.0) and the
corresponding moisture content at any particular temperature is an essential tool for design of
drying, packaging and storage systems of food.
TBU researcher reported that PVP-CMC hydrogel based food packaging material has capacity
to absorb moisture, therefore, we are motivated to pursue the research to find the moisture
sorption isotherm and isosteric heat sorption properties of PVP-CMC hydrogel.
Tuesday, August 11, 2015
10
Visual images of PVP-CMC hydrogel based food packaging material
 Transparent
 Sealable
 Printable
 Able to absorb moisture
 Breathable and
 Biodegradable
Tuesday, August 11, 2015
11
Back site
Tuesday, August 11, 2015
Front site
12
Water activity at different temperatures
Salts
25
Sodium hydroxide,
NaOH
Water activity (aw)
35
45
55
Water activity of each
saturated solution was
estimated following
the equation:
0.087
0.065
0.05
0.039
0.237
0.215
0.197
0.182
0.327
0.32
0.311
0.3
0.443
0.436
0.429
0.424
aw = [ΔH/R] [1/T] + c
0.536
0.515
0.497
0.481
where, T=°K
0.742
0.72
0.699
0.686
Sodium chloride,
NaCl
0.752
0.748
0.745
0.71
Potassium chloride,
KCl
0.855
0.822
0.791
0.764
0.9728
0.9672
0.962
0.9572
Potassium
acetate,CH3COOK
Magnesium chloride,
MgCl2
Potassium
carbonate,
K2CO3
Magnesium
nitrate,Mg(NO3)2
Sodium nitrate,
NaNO3
Potassium sulphate,
K2SO4
Tuesday, August 11, 2015
13
Moisture sorption isotherm of PVP-CMC hydrogel film
Temperature (˚C)
Water activity
#EMC(%db)±SD
25˚C
0.087
0.237
0.327
0.443
0.536
0.742
0.752
0.855
0.972
LSD 0.05
LSD 0.01
0.065
0.215
0.32
0.436
0.515
0.72
0.748
0.822
0.967
LSD 0.05
LSD 0.01
17.662±0.75*
19.682±0.93
23.567±1.11
25.608±0.76
27.621±1.07
39.797±0.93
39.581±2.62*
58.043±1.95
118.693±1.16
1.48
2.13
19.985±1.22*
23.085±3.03*
23.286±0.85*
39.739±0.97
25.33±1.13*
35.667±0.87*
39.295±0.77*
53.09±1.17
119.196±26.76
11.33
16.34
35 ˚C
Where,
EMC= equilibrium moisture content of sample on
percent dry basis
WEq= weight of sample after attaining equilibrium
moisture content
WDry= weight of sample after removal of the moisture
in the oven
Note: #Mean of five replications ± SD. For each temperature, F test is positive (p<0.01) for variation of
EMC with water activity; *within a column for a particular sample, EMCs are not significantly different
(LSD test, p<0.01 or < 0.05) with change of aw;
Tuesday, August 11, 2015
14
Temperature (˚C)
Water activity
#EMC(%db)±SD
45 ˚C
0.05
0.197
0.311
0.429
0.497
0.699
0.745
0.791
0.968
LSD 0.05
LSD 0.01
0.039
0.182
0.3
0.424
0.481
0.686
0.71
0.764
0.965
LSD 0.05
LSD 0.01
37.941±2.17*
11.054±0.40
15.704±0.95*
32.701±4.72*
20.115±0.78*
25.925±1.68*
29.873±2.47*
36.071±0.48*
168.022±15.77
7.09
10.22
24.237±1.66*
16.267±2.84
17.702±1.38*
23.090±2.12*
26.970±4.8*
27.532±3.66*
30.745±5.75*
30.504±0.85*
70.575±1.81
5.75
3.99
55 ˚C
Note: #Mean of five replications ± SD. For each temperature, F test is positive
(p<0.01) for variation of EMC with water activity; *within a column for a
particular sample, EMCs are not significantly different (LSD test, p<0.01 or <
0.05) with change of aw;
Tuesday, August 11, 2015
15
Comparison of PVP-CMC hydrogel film at different temperature
using GAB, BET and Peleg models
Model
GAB
BET
Peleg
Tuesday, August 11, 2015
Parameter
Temperature
25˚C
35˚C
45˚C
55˚C
M0
C
14.266
1.30E+45
14.244
8.62E+44
9.777
-1.05E+46
13.323
-3.12E+45
K
r2
RMSE
MRE
Residual Plot
M0
0.903
0.991
2.71
7.31
Pattern
3.669
0.908
0.953
6.38
13.38
Pattern
4.408
0.978
0.938
11.25
23.05
Pattern
6.596
0.841
0.899
4.81
13.53
Pattern
3.573
C
r2
RMSE
MRE
Residual Plot
K1
n1
K2
n2
r2
RMSE
MRE
Residual Plot
7.54E+45
0.528
26.80
80.91
Pattern
105.292
8.188
34.348
0.322
0.993
2.65
5.77
Random
-2.16E+45
0.589
27.65
85.84
Pattern
115.869
9.322
34.714
0.252
0.978
4.77
7.57
Random
-4.49E+46
0.921
13.24
32.24
Pattern
211.970
10.867
23.835
4.68E-15
0.971
8.47
33.73
Random
-4.10E+46
0.161
12.30
33.11
Pattern
63.626
6.181
21.383
1.81E-14
0.970
7.66
27.67
Random
16
Estimation parameters and comparison criteria for PVP- CMC hydrogel film
at different temperature using Modified Oswin models
Tuesday, August 11, 2015
Model
Parameters
Modified Oswin
A
Values
B
33.748
-0.135
x
2.306
r2
0.921
RMSE
18.99
MRE (%)
29.22
Residual plot
Random
17
Effect of temperature on moisture sorption isotherm of
PVP-CMC hydrogel based food packaging material
Tuesday, August 11, 2015
18
Isosteric heat of sorption of PVP-CMC hydrogel based
food packaging material at different moisture content
Tuesday, August 11, 2015
19
Acknowledgement
Authors are thankful for the financial support provided
by the Ministry of Education , Youth and Sports of the
Czech Republic - Program NPU I (LO1504)
Tuesday, August 11, 2015
20
21