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* Contact email ID: nabanita@ft.utb.cz / madhu@agfe.iitkgp.ernet.in

Tuesday, August 11, 2015

Moisture Sorption and Isosteric Heat of Sorption properties of PVP-CMC Hydrogel based Food

Packaging Material

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

Nabanita Sahaa, Dipali S.Shindeb, Madhusweta Dasb, Petr Saha a

Biopolymers and Bioplastics-2015

OutlineINTRODUCTION

Polymer in packaging Hydrogel food packaging Unique properties of hydrogel Application of hydrogels Preparation techniques of hydrogel

MOTIVATION OF RESEARCH

EXPERIMEMTATION

RESULTSVisual Images of PVP-CMC hydrogel food packaging materialAFM image of PVP-CMC hydrogel film Water activity of PVP-CMC hydrogel at different temperatureMoisture sorption isotherm of PVP-CMC hydrogel filmComparison of PVP-CMC hydrogel film at different temperatureEffect of temperature on moisture sorption isothermIsosteric heat of sorption of PVP-CMC hydrogel

CONCLUSION

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Polymers in Packaging

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Introduction

Polymeric materials play a dominate role in the food packaging industry

4

Introduction

5

Introduction

Table no.

Polymer Type Code

1 Polyethylenes PE

2 Polypropylenes PP

3 Poly(ethylene-vinyl acetates) EVA

4 Polystryrenes PS

5 Polyvinylchlorides PVC

6 Ionomers I

7 Polyethylene terephthalates PET

8 Polyvinyl acetate PVAc

9 Polycarbonates PC

10 Polyamides PA

11 Polyvinylalcohols PVOH

12 Polyvinylidene choliride PVDC

13 Others O

Lists of acceptable polymers for use in food packaging

Global bioplastic packaging market by product type, 2010 (%)

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Hydrogel based food packaging

Hydrogel

Crosslinking network and pores in hydrogel

Hydrogels are one kind of bio-inspired materials and devices for chemical and biological defense .

Introduction

Porous internal morphology

Quite a good moisture absorption capacity

Flexible in nature for the preparation of sample in different shape, size and thickness

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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.

R.V.Ulijn., et al. Materialstoday, Vol 10, p-40-48, 2007

Introduction

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Based on starting materials • Monomers• Prepolymers• polymers

Physical stimuli• Heat Pressure pH Ionic strength

• Hydrophobic interactions• Charge interactions• Hydrogen bonding• Stereo complexation• Supramolecular chemistry

Chemical stimuli• Different chemical Crosslinking agents

Irradiation Technique X-ray UV-ray Gamma ray

Methods for the preparation of hydrogelMethods for the preparation of hydrogel

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Preparation of “PVP-CMC Hydrogel” for Food Packaging

Experimental

Polymer solution

Moulds with polymer solution in aseptic environment

Sterile polymer solution

Cooling in an aseptic environment

3-dimensional crosslinking network developed

Autoclave

Moist heat

Occurrence of crosslinking phenomena

Hydrogel

SEM images of hydrogels: PVP/CMC (a.i) surface (a.ii) cross section

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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.

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Transparent

Sealable

Printable

Able to absorb moisture

Breathable and

Biodegradable

Visual images of PVP-CMC hydrogel based food packaging material

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Front site Back site

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Salts Water activity (aw)25 35 45 55

Sodium hydroxide, NaOH

0.087 0.065 0.05 0.039

Potassium acetate,CH3COOK 0.237 0.215 0.197 0.182

Magnesium chloride, MgCl2

0.327 0.32 0.311 0.3

Potassium carbonate, K2CO3

0.443 0.436 0.429 0.424

Magnesium nitrate,Mg(NO3)2

0.536 0.515 0.497 0.481

Sodium nitrate, NaNO3 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

Potassium sulphate,K2SO4

0.9728 0.9672 0.962 0.9572

Water activity at different temperatures

Water activity of each saturated solution was estimated followingthe equation:

aw = [ΔH/R] [1/T] + c

where, T=°K

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Temperature (˚C) Water activity #EMC(%db)±SD 

25˚C 0.087 17.662±0.75*

  0.237 19.682±0.93  0.327 23.567±1.11  0.443 25.608±0.76  0.536 27.621±1.07  0.742 39.797±0.93  0.752 39.581±2.62*

  0.855 58.043±1.95  0.972 118.693±1.16  LSD 0.05 1.48  LSD 0.01 2.13

35 ˚C 0.065 19.985±1.22*

  0.215 23.085±3.03*

  0.32 23.286±0.85*

  0.436 39.739±0.97  0.515 25.33±1.13*

  0.72 35.667±0.87*

  0.748 39.295±0.77*

  0.822 53.09±1.17  0.967 119.196±26.76  LSD 0.05 11.33  LSD 0.01 16.34

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;

Moisture sorption isotherm of PVP-CMC hydrogel film

Where,EMC= equilibrium moisture content of sample on percent dry basisWEq= weight of sample after attaining equilibrium moisture contentWDry= weight of sample after removal of the moisture in the oven

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45 ˚C 0.05 37.941±2.17*

  0.197 11.054±0.40  0.311 15.704±0.95*

  0.429 32.701±4.72*

  0.497 20.115±0.78*

  0.699 25.925±1.68*

  0.745 29.873±2.47*

  0.791 36.071±0.48*

  0.968 168.022±15.77  LSD 0.05 7.09  LSD 0.01 10.22

55 ˚C 0.039 24.237±1.66*

  0.182 16.267±2.84  0.3 17.702±1.38*

  0.424 23.090±2.12*

  0.481 26.970±4.8*

  0.686 27.532±3.66*

  0.71 30.745±5.75*

  0.764 30.504±0.85*

  0.965 70.575±1.81  LSD 0.05

LSD 0.01

5.753.99

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;

Temperature (˚C) Water activity #EMC(%db)±SD 

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Model Parameter Temperature

25˚C 35˚C 45˚C 55˚C

     GAB

M0 14.266 14.244 9.777 13.323C 1.30E+45 8.62E+44 -1.05E+46 -3.12E+45

K 0.903 0.908 0.978 0.841r2 0.991 0.953 0.938 0.899RMSE 2.71 6.38 11.25 4.81MRE 7.31 13.38 23.05 13.53Residual Plot Pattern Pattern Pattern Pattern

BET

M0 3.669 4.408 6.596 3.573

C 7.54E+45 -2.16E+45 -4.49E+46 -4.10E+46r2 0.528 0.589 0.921 0.161RMSE 26.80 27.65 13.24 12.30MRE 80.91 85.84 32.24 33.11Residual Plot Pattern Pattern Pattern Pattern

    Peleg

K1 105.292 115.869 211.970 63.626n1 8.188 9.322 10.867 6.181K2 34.348 34.714 23.835 21.383n2 0.322 0.252 4.68E-15 1.81E-14r2 0.993 0.978 0.971 0.970RMSE 2.65 4.77 8.47 7.66MRE 5.77 7.57 33.73 27.67Residual Plot Random Random Random Random

Comparison of PVP-CMC hydrogel film at different temperature using GAB, BET and Peleg models

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Model Parameters Values

Modified Oswin A33.748

B -0.135

x 2.306

r2 0.921

RMSE 18.99

MRE (%) 29.22

Residual plot Random

Estimation parameters and comparison criteria for PVP- CMC hydrogel film at different temperature using Modified Oswin models

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Effect of temperature on moisture sorption isotherm of PVP-CMC hydrogel based food packaging material

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Isosteric heat of sorption of PVP-CMC hydrogel based food packaging material at different moisture content

Acknowledgement

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Authors are thankful for the financial support provided by the Ministry of Education , Youth and Sports of the Czech Republic - Program NPU I (LO1504)

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