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Montmorillonite clay for starch-based barrier dispersion coating: Part 1 The influence of citric acid on viscosity and barrier properties
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.ORCID iD: 0000-0001-7368-7227
Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.ORCID iD: 0000-0002-1256-1708
2014 (English)In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, 160-166 p.Article in journal (Refereed) Published
Abstract [en]

Starch-based coating formulations were draw-down coated on a paper substrate and the effect on the water vapor transmission rate, WVTR, upon montmorillonite addition was compared to that of the pure the starch matrix without added plasticizer and for poly(ethylene glycol), PEG, and citric acid, CA, as potential plasticizers. Both potential plasticizers were added at a ratio of 3 to 10 to starch. Addition of CA to the starch solution substantially lowered the WVTR of the coated papers compared to coating with a pure starch or PEG-plasticized coating. The WVTR of the papers coated with starch and CA was lower than that obtained for paper coated with non-plasticized montmorillonite-starch dispersions, and approximately similar to paper coated with montmorillonite-starch dispersions plasticized with PEG or with citric acid. Addition of montmorillointe was effective in reducing the WVTR in the case of PEG-plasticized starch but not in the case of CA. These differences in WVTR were indicated to be due to differences in the viscosity and the clay swelling indicating that CA and PEG affected the state of dispersion differently. CA was also investigated as a dispersing agent by addition in small quantities to the montmorillonite dispersion at different pH values. When this clay dispersion was added to a suspension already containing PEG, CA gave slightly reduced plastic viscosity and there was also a weak correlation between low plastic viscosity and WVTR.

Place, publisher, year, edition, pages
Elsevier, 2014. 160-166 p.
Keyword [en]
Starch; Montmorillonite; Citric acid; Poly(ethylene glycol); Rheology; Barrier properties
National Category
Polymer Technologies
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kau:diva-27110DOI: 10.1016/j.clay.2014.04.040ISI: 000340302200022OAI: oai:DiVA.org:kau-27110DiVA: diva2:618484
Projects
Renewable Functional Barriers
Funder
VINNOVA
Available from: 2013-04-28 Created: 2013-04-28 Last updated: 2015-10-21Bibliographically approved
In thesis
1. Effects of Citric Acid on Starch-Based Barrier Coatings
Open this publication in new window or tab >>Effects of Citric Acid on Starch-Based Barrier Coatings
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With growing environmental concerns, efforts are made to replace petroleum based products with renewable alternatives. This is particularly evident in the packaging industry, where replacing synthetic polymers with renewable materials is of considerable interest. Materials for food packaging need to give protection, acting as a barrier against substances that can adversely affect the food quality such as water and oxygen.

In this work, barrier dispersion coatings based on starch were used to produce coated papers which act as barrier against water and oxygen. However, since starch is both a hydrophilic and hygroscopic material, this barrier material becomes problematic to use at high relative humidity. In order to reduce this problem and improve the barrier properties enabling starch based barrier materials to be used in food packaging applications, two approaches were studied.

Citric acid was utilized as a cross-linker of the starch and it was found to reduce the moisture sorption, the molecular movement and swelling at high relative humidity. It was seen that cross-linking and hydrolysis due to the low pH both affected the barrier properties significantly, but in opposing directions. By controlling these two reactions it was seen that this could lead to reduced gas permeability. It was also seen that cross-linking of starch by citric acid occurs at low temperatures, 70 °C at pH as high as 6.5.

Starch nano-composites were produced by incorporating montmorillonite, to the barrier dispersion to improve the barrier properties. It was seen that the suspension viscosity was reduced by poly(ethylene glycol) and citric acid adsorption on the montmorillonite particles. Also, a tendency for improved barrier properties with reduced aggregate volume fraction and reduced swelling was observed. It was also seen that up scaling this formulation to pilot scale was possible and that promising results were achieved.

Abstract [en]

Baksidestext

With growing environmental concerns, efforts are made to replace petroleum based materials with renewable alternatives such as starch. In this work, dispersions based on starch were used to produce coated papers which act as barrier against substances that can adversely affect the food quality such as water and oxygen. However, since starch is both a hydrophilic and hygroscopic material, this barrier material becomes problematic to use at high relative humidity.

Citric acid was utilized as cross-linker for starch and it was found to reduce the moisture sorption, diffusion and swelling at high relative humidity. Both cross-linking and hydrolysis due to the low pH affected the barrier properties significantly, but in opposing directions. By controlling these two reactions it was possible to achieve reduced gas permeability.

Starch nano-composites were produced by incorporating montmorillonite clay, to the barrier dispersion. It was seen that the suspension viscosity was reduced by poly(ethylene glycol) and citric acid adsorption on the clay. Also, a tendency for improved barrier properties with reduced aggregate volume fraction and reduced swelling was observed. It was also seen that up scaling this formulation to pilot scale was possible and promising results were achieved.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2013. 80 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2013:25
Keyword
Starch, Citric acid, Cross-linking, hydrolysis, Montmorillonite, WVTR, OTR, Barrier properties
National Category
Polymer Technologies
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-27127 (URN)978-91-7063-502-1 (ISBN)
Public defence
2013-06-13, 9C203, Nyquistsalen, Karlstads universitet, 10:15 (English)
Opponent
Supervisors
Projects
Renewable Functional Barriers
Funder
Vinnova
Available from: 2013-05-23 Created: 2013-04-29 Last updated: 2013-05-23Bibliographically approved

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Olsson, ErikJohansson, CaisaJärnström, Lars
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